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1. Temp amp Current File Edit View Project Operate Tools Window Help q Ha 9 2 5 11 15pt Application Font 5 tar 2 6 lt Search A PJH ths CHI Val PAL Lt Temperature Indicator Pito PAY 1 Temperature Boro mi E 0 2504 700 600 2007 T rature Sto emperature Stop 4005 STOP 3002 2 100 0 100 200 Time Current Stop E ini EEE E E EE ia UV HR Z3 ERE C DUE ka E Ki Plot 0 Current Indicator E ma RAN Pto PAY primary display 100 3 M secondary display E H 3 Figure 3 20 LabVIEW software interface 18 Temp amp Current File Edit View Project Operate Tools Window Help gt Bs ale crecio for Pal an pl Temperature Temperature Stop e Numeric piRydepny EET Current iz je ar EY i secondary display Current Stop He 10 44 AM 9 1 2013 Zar OP A Figure 3 21 LabVIEW software program for TSDC system 37 3 8 Overall Schematic Diagram of TSDC System At last figure 3 22 presents the main frame of the whole diagram As discussed before TSDC cell main chamber heating unit cooling unit electrical unit vacuum unit and data acquisition unit constitute the whole TSDC system
2. gt bo Detan Delta o lo o n 130 Pure Epoxy Pure Epoxy Ceramic 10 weight 180 230 T degree C Figure 6 3 DEA temperature scan test detan Delta Table 6 1 DEA Test Temperature Scan Data Analysis Sample e max pF m Pure Epoxy Epoxy 61 De Tan Delta 18 110C 120C 130C 12 140C 150C 160C 6 170C 15 I 20C 130C 140C 9 1 500 160C 170C 3 1000 100000 10000000 10 1000 100000 10000000 De Frequency Hz De Frequency Hz Figure 6 4 Pure epoxy sample DEA Figure 6 5 10 silica filler sample DEA frequency scan test e frequency scan test e 1000 1000000 De Frequency Hz Figure 6 6 Pure epoxy sample DEA Figure 6 7 10 silica filler sample DEA frequency scan test e frequency scan test e 1000 1000000 De Frequency Hz 62 o iD De Tan Delta e UA gt an 1000 1000000 1000 1000000 De Frequency Hz De Frequency Hz Figure 6 8 Pure epoxy sample DEA Figure 6 9 10 silica filler sample DEA frequency scan test detan delta frequency scan test detan delta Epoxy Ceramic 10 weight 1 00E 00 1 00E 02 1 00E 04 1 00E 06 1 00E 08 1 00E 10 De Frequency Figure 6 10 Master curve of DEA test Pure Epoxy Pure Epoxy Epoxy Ea 82 467 kJ mol Ceramic 10 10 Silica Composite weight Ea 114 77 kJ mol 23 2 4 2 3
3. or letters or continuous such as sounds images and other measurements of continuous systems 32 Analog technology is cheaper but there is a limitation of size of data that can be transmitted at a given time Digital technology has revolutionized the way most of the equipment work Data is converted into binary code and then reassembled back into original form at reception point Since these can be easily manipulated it offers a wider range of options Therefore convert analog signal to digital signal is necessary for TSDC system TSDC system records two signals temperature signal and current signal Current magnitude in function of temperature is the typical TSDC curve Current signal is measured by Keithley 6517B pico ammeter which output digital current directly Keithley 6517B pico ammeter connects to PC by GPIB card from National Instrument Company through which current signal is transferred to PC Temperature signal from RTD sensor is an analog signal Model PT104A 4 Channel RTD Input Data Acquisition Module is used to collect temperature signal and transfer it to PC LabVIEW software from National Instrument Company was used to record and plot two signals 3 7 2 Temperature Data Logger As discussed above Model PT104A temperature data logger from Omega Company is used to convert temperature signal from analog to digital as shown in figure 3 18 The PT 104A logger is a four channel high resolution temperature data acquisition
4. pf Figure 4 5 Schematic procedure of epoxy TSPC experiment 4 4 Window Polarization Addressing the fact the most polymer relaxations are a cumulative effect of many individual relaxations Lacabanne and Chatain introduced the technique called windowing polarization to study relaxation phenomena 1 2 The relaxation time temperature relationship associated with each window is used to isolate elementary Debye type relaxations of the molecules over the entire relaxation spectrum Physically the existence of multiple relaxations can be explained by several mechanisms including dipole dipole interactions variations in size and shape of the rotating dipolar entities anisotropy of the internal field in which the dipoles reorient internal rotation bending and twisting in polymers etc 1 This technique is a further development of Bucci et al s attempt to isolate overlapping relaxations 2 To isolate the transitions for a material having two peak temperatures Tmi and Tm2 they polarized the material at Tpi such that Tm lt Tpi lt Tm2 to allow the dipoles associated with Tm to be polarized but those associated with T4 to be undisturbed The TSDC curve would then show only the 46 relaxation associated with Ti The relaxation associated with Tyo could be isolated by polarizing the material at T 2 such that Ta lt Tj and removing the field at Td such that Tm lt Ta lt Tm A schematic of this technique is shown i
5. 53 sNaumE m kTp 3 Where s is the geometrical factor associated with the dipole orientation for rotating dipoles s 1 3 Na is the concentration of dipoles Um is the electrical moment k is Boltzmann s constant and E is the directing electrical field operating on the dipoles The depolarization current density is given by dP t _ P t WS gt 4 T Since experiments are run under constant rate mode these equations are modified to include the heating rate Thus the time is now expressed in terms of the initial temperature T and heating rate r t T T 5 r The standard way to analyze TS peaks is based on the BFG Bucci Fieschi and Guidi area method for the current density J T recorded for a Debye TSDC peak and its relationship with the relaxation time Pict JC 22 6 Where P T is the residual polarization and t T is the relaxation time at each temperature T The residual polarization P T is easily determined from the area under the TSDC elementary peak from T to the end of the high temperature tail of the curve as shown in figure 5 10 J T being the ordinate of the curve at this same temperature 54 UN FT Ty Figure 5 10 BFG area method to calculate residual polarization The relaxation times calculated from part of the rise of each elementary peak analyzed in this way are represented in an Arrhenius plot of the relaxation times log t vs 1 T by a line whose sl
6. surface or volume 29 R SERVICABLE PARTS SERVICE BY QUALIFIED PERSONNEL ONLY Test Fixture COMMON 2V OUT 9 0 2VDC MAX Rus Switch Cou S ur DIGITAL I O IEEE 488 amp e uu e e e Open Switch Open Lid TRIGGER LINK RS 232 JN AGAINST FIRE HAZARD REPLACE FUSE WITH SAME TYPE AND RATING 6517B Figure 3 15 Interlock diagram of Keithley 6517B meter 3 6 7 Connecting Cable Model 7078 TRX low noise triaxial cable that is terminated at both ends with a three slot male triaxial connector was used for TSDC system as shown in figure 3 16 Figure 3 16 Cable used in TSDC system Here are the technical characteristics of Model 7078 TRX cable 26 Working voltage 600 V peak center conductor to inner shield 1 300 V peak center conductor and inner shield to outer shell 30 gt Operating environment 32 F to 122 F 0 C to 50 C up to 70 percent relative humidity at lt 95 F 35 C gt Maximum current 1 A gt Contact resistance lt 1 Q gt Insulation resistance 1013 Q center conductor to inner shield 500 V test voltage 73 F 23 C at lt 40 percent relative humidity 3 6 8 LEMO Connector The LEMO series S Coaxial Connector was used for TSDC system s connection between cable and instrument as shown in figure 3 17 Series S Coaxial Connectors are capable for all applications in which a high density of connectors is necessary espec
7. 2 They attempted to experimentally deconvolute individual relaxation contributions from the global relaxation spectra The relaxation time temperature relationship associated with each window is used to isolate elementary Debye type relaxations of the molecules over the entire relaxation spectrum 3 Physically the existence of multiple relaxations can be explained by several mechanisms including dipole dipole interactions variations in size and shape of the rotating dipolar entities anisotropy of the internal field in which the dipoles reorient internal rotation bending and twisting in polymers etc 4 This technique is a further development of the attempt by Bucci to isolate overlapping relaxations 4 To isolate the transitions for a material having two peak temperatures Tmi and Tm they polarized the material at Tp such that Tm lt Tp lt Tm to allow the dipoles associated with Tm to be polarized but those associated with Tm2 to be undisturbed The TSDC curve would then show only the relaxation associated with Tm The relaxation associated with Tm2 could be isolated by polarizing the material at Ty such that Ti lt Tp2 and removing the field at Tg such that Tmi lt Ta lt Ta Window polarization has recently been utilized to probe space charge relaxations Space charge relaxations were demarcated from glass transition relaxation by a minimal shift in peak temperatures for different temperature windows Although TSDC has a relat
8. s temperature accurately TSDC cell allows operators to mount and change sample easily Three detail views of TSDC cell are shown in figure 3 2 In order to avoid piezoelectric effects there is very little pressure applied to the sample when it is mounted between the two electrodes Both electrodes are well isolated from the sample holder and top flange 13 Figure 3 2 TSDC cell 3 3 Main Chamber The main chamber is the main structure of the system It plays the roles of supporting TSDC cell providing enclosed environment for experiment and connecting to other component of system The main chamber is made by 304 stainless steel which makes the main chamber have uniform geometry shape under extreme low and high temperature environment 19 3D model of chamber designed by Pro Engineering software and real chamber view are shown in figure 3 3 Figure 3 4 shows the dimension of the chamber There are totally seven ports on the chamber Table 3 1 shows the function for each port All the ports of main chamber are designed to standard 2 3 4 UHV flange By using standard flange adapter from Lesker Company 2 3 4 UHV FLANGE TO QF25 every function units can be easily connected to main chamber What is more to make sure main chamber has a perfect sealing performance each connection between accessories parts and main chamber was sealed by an O ring To make the 14 system being in a reliable electrical insulation environment the main c
9. 1 Polarization e Heat up sample to 120 C in 3 mins e Apply DC voltage 200V 400V 600V Hold temperature and voltage for 10 minutes 2 Freezing e Turn off heater cool down system to 50 C in 3 mins e Turn off voltage 3 Depolarization current e Wait for 15 minutes make polymer relax completely for polarized voltage e Short connect two electrodes e Heat up sample from 50 C to 120 C at rate 4 C min plot Temperature vs Current curve Electric field td Temperature v O et v Time Figure 4 4 Schematic procedure of epoxy TSDC experiment 44 Table 4 3 TSDC Experiment Parameter for Epoxy and Composite Samples 10 mins 200V mm E 400V mm 600V mm 4 3 TSPC Experiment Figure 4 5 shows a schematic of the TSPC experiment An un polarized state sample was first fixed at low temperature by cooling the sample under short circuit conditions An electrical field is then applied during subsequent definite heating The thermally stimulated transition from neutrality to a polarized state can be followed by registering the charging current as a function of temperatures Higher temperatures resulted in negative currents If dipolar or ionic processes are involved these show similar peaks as in global TSDC Further a higher current in TSPC compared to TSDC was related to the formation of ionic space charge during polarization at high temperatures in TSDC 45 Time 3 T
10. 1 T 1000 K 1 Figure 6 11 Shift factor of DEA master curve 63 6 2 Dynamic Mechanical Analysis 3 Point Bending Dynamic mechanical analysis also known as dynamic mechanical spectroscopy is a technique used to study and characterize materials It is most useful for studying the viscoelastic behavior of polymers A sinusoidal stress is applied and the strain in the material is measured allowing one to determine the complex modulus The temperature of the sample or the frequency of the stress are often varied leading to variations in the complex modulus this approach can be used to locate the glass transition temperature of the material as well as to identify transitions corresponding to other molecular motions DMA Rheometric Solid Analyzer 3 from TA instruments was used to investigate sample s mechanical property The samples with dimensions 54 84 mm x 5 94 mm x 1 72 mm length x width x height Temperature scan spectroscopy and frequency scan spectroscopy can be measured by TA DMA instrument For the temperature scan test apply 0 1 of strain determined from the strain amplitude sweep test to sample and scan temperature from room temperature to 225 C with 5 C minute increment For the frequency scan test same strain amplitude was applied 0 1 The specific temperature are 65 C 68 C 71 C 74 C 77 C 80 C 83 C The scan range of frequency is from 1 rad s to 500 rad s In phase storage modulus E out of phase lo
11. 3 point bending test E emeeeesnnreernnersvnrensvnnrssvnrsssvnrvesnnsvennrnvennrnvevnrsvevnnssene 65 Figure 6 13 DMA 3 pomit bending test E t 2 enue ta 65 Figure 6 14 DMA 3 point bending test tan delta ooncnnnnucinncnoncnnncnnonnconnnconnnoncnnonaconnncnnanonnnons 65 Ligure 6 15 Master curve of DMA esta de 66 Figure 6 16 Shift factor of DMA master curve eese oa anan aana anna nana n anana anna nenen 66 Figure 6 17 DSC Curve 55 ka BAG daa a 68 Figure 6 18 Sample moisture gain weight curve iS oet eid scias 68 Figure 6 19 Pure epoxy humidity ES We 69 Figure 6 20 10 silica sample humidity test oo eeececesccecssececeeeeeceeceeceeeeeeseeessaeeeeseeeenaeeees 69 Figure 6 21 Pure epoxy humidity test e 1o reis dde ast eased ei 69 Figure 6 22 10 silica sample humidity test ooo eee ee eeeeesececsscceessccessscceesscceesceeesseeeeseeeees 69 Figure 6 23 Pure epoxy humidity test detan delta alta dani 69 Figure 6 24 10 silica sample humidity test detan delta see 69 xi CHAPTER 1 INTRODUCTION Thermally stimulated depolarization current measurement is one of the most important methods for identifying and characterizing relaxation processes charge storage and charge decay processes in electrified dielectrics and electrets 1 The charge of electrets may be generated by various mechanisms orientation of permanent dipoles in polar materials trapping of charges by st
12. 300 C in 3 minutes For slow heating the temperature controller of the unit can output a constant heating rate usually 4 C minutes to 8 C minutes is used during experiment Alternative consideration for heating unit was using cartridge heater Unlike cartridge heater which needs to attach cartridge heaters heater block and temperature sensor to TSDC cell hot gas heating does not need to attach any accessory to TSDC cell The fewer attachment to TSDC cell the less influence for signal measurement What is more heating up by hot gas make sample have uniform temperature The top surface and bottom surface do not have temperature gradient Nitrogen gas instead of compressed air was used for heating medium Nitrogen gas can avoid moisture s influence for electrical measurement Additionally nitrogen is heated outside of the chamber and then been injected to the chamber by this way the nitrogen gas with desired temperature can be injected to sample directly Therefore system has a faster temperature response 17 Figure 3 5 Overview of heating unit 3 4 1 Gas Heater The AHP series in line gas heaters from Omega Company as shown in figure 3 6 is used to heat clean dry air or gas for temperature chamber AHP series gas process heaters provide hot air and gas up to 1000 F 540 C with infinite control by varying the voltage and or the air flow 20 The controller of gas heater is CN63100 type closed loop controller which is
13. 88 2 93 1 k 1000 1 K 95 C 93 C 90 C 88 C gt 85 C 83 C 80 C 78 C gt 75 C 73 C 1 k 1000 1 K Figure 5 12 ti vs 1 T plot for 10 silica composite sample 56 1 6 1 5 WG 10 73 y 5 1508x 135 73 C 71 C y 5 0724x 13 473 709C 68 C y 4 8649x 12 762 68 C 66 C y 3 7146x 9 6433 APA E oZ IL 1 0 669C 64 C y 3 6719x 9 6002 0 9 64 C 62 C y 3 2996x 8 5857 0 8 2 88 2 93 2 98 3 03 1 k 1000 1 K Figure 5 13 log t vs 1 T plot for pure epoxy sample 1 60 1 55 95 C 93 C y 3 2857x 7 6117 909C 889C y 2 5609x 5 7063 85 C 83 C y 2 4349x 5 4516 80 C 78 y 1 8326x 3 8606 75 C 73 y 1 2611x 2 281 2 7 2 8 2 9 1 k 1000 1 K Figure 5 14 log t vs 1 T plot for 10 silica composite sample Figure 5 15 shows activation energy value as function of temperature for two samples The data indicates that the activation energy of sample increase as temperature rise Pure epoxy sample has bigger activation energy than 10 silica sample Figure 5 16 and 5 17 show the enthalpy and entropy value as function of polarization temperature respectively for two samples 57 Nearby glass transition area material presents maximum enthalpy and entropy value Figure 5 18 shows the relationship between enthalpy and entropy Pure Epoxy E E a E 10 S
14. IEEE 488 BUS GPIB 1980 31 A J Caristi IEEE 488 General Purpose Instrumentation Bus Manual Academic Press Inc 1990 32 National Instrument Company Application Notes http www ni com labview 33 HUNTSMAN International LLC Material application notes MSDS ARALDITE LY 1556 US Epoxy Resin http www huntsman com advanced_materials a Y our 20Industry Adhesives 34 HUNTSMAN International LLC Material application notes MSDS ARADUR 2964 US Agent http www huntsman com advanced materials a Your 20Industry Adhesives 35 P Sigmund Theory of Sputtering PROLA Physical Revolution Volume 184 1969 383 416 73 36 POLARON instruments Inc Application Notes Model 5100 SEM Sputtering Coater http www quorumtech com pdf productOperatingManuals E5100_Operating_Manual pdf 37 M Mudarra J Belana J C Canadas J A Diego Windowing polarization considerations for the study of the space charge relaxation in poly methyl methacrylate by thermally stimulated depolarization currents Polymer Volume 40 Issue 10 May 1999 Pages 2659 2665 38 W Brostow Thermally stimulated depolarization of a copolymer of poly ethylene terephthalate and p hydroxybenzoic acid Polymer Volume 33 Issue 22 1992 Pages 4687 4692 74
15. also from Omega Company One temperature sensor T fittings is connected to gas heater to be a holder for RTD sensor A PRTF Type 3 wire general purpose RTD probes with fiberglass insulated cable is used to be heater s temperature measuring unit Figure 3 6 OMEGA AHP series gas heater 18 3 4 2 Nitrogen gas The gas source of heater is laboratory compressed nitrogen gas The flow of nitrogen gas in lab is 57 L min 2 SCFM or higher Pressure of laboratory compressed nitrogen gas is usually no higher than 45 to 50 psig at maximum flow 21 To provide constant and uniform gas flow to air heater in each heating cycle being able to measure the flow of gas is necessary One gas flow regulator was integrated in pipe 3 4 3 Temperature Controller Type CN63100 closed loop relay output temperature controller from Omega Company shown in figure 3 7 is used to control heating unit The control strategy is based on PID principle which was discussed already in literature review section 3 4 3 1 CN63100 Controller Output Mode CN63100 controller provides different temperature control output 22 Time proportional or linear DC mode Manual mode ON OFF mode Set Point Ramp Rate SPRP mode Time proportional or linear DC mode is the most common output type Controller provides a 10046 output Heaters will heat up sample as fast as possible When temperature arrives at setpoint controller will reduce output percentage to maintain temperatur
16. esie eaaa 43 Figure 4 3 Epoxy film sample for TSDC experiment left before sputtering right after julii p MM E 43 Figure 4 4 Schematic procedure of epoxy TSDC experiment esee 44 Figure 4 5 Schematic procedure of epoxy TSPC experlMeMt oooocooccccnnccncnoncnononcnnnoncconanccnnnnccnnnncnnns 46 Figure 4 6 Schematic procedure of epoxy window polarization experiment 48 Figure 5 1 TSDC curve 600V polarizations s mene te toe UN RD Ed Pet D te peed madidus 49 Figure 5 2 TSDC curye 400V polarizations a edo bi 49 Figure 5 3 TSDC curve 200V polarization eii et top eere c diede t dia tac 49 Figure 5 4 Pure epoxy sample depolarization current comparison among different polarization Voltages to ak gaen E Gaga 50 Figure 5 5 Epoxy silica composite sample depolarization current comparison among different polarization voltages eee ei aan 50 Ereure 6 TSPC200V iso hi PRAN 51 FipWre 5 7 TSDC 200 suppe 51 1X Figure 5 8 Window polarization data of pure epoxy sample sse 50 Figure 5 9 Window polarization data of 10 silica composite sample sess 51 Figure 5 10 BFG area method to calculate residual polarization ees 55 Figure 5 11 ti vs LT plot for pure epoxy sample e pesten gie bacon 56 Figure 5 12 ti vs 1 T plot for 10 silica composite sample seen 56 Figure 5 13 Tog s vs 1 T plot for pure epoxy sa
17. of Thermally Stimulated Depolarization Currents Institute of Physics Charles University 1991 10 P Braunlich Thermally Stimulated Relaxation in Solids Topics in Applied Physics Volume 37 1979 11 J M Giehl W M Pontuschka L C Barbosa A R Blak M Navarro Z M Da Costa Study of sodium tellurite glass using the thermally stimulated depolarization current technique TSDC Journal of Non Crystalline Solids 357 2011 1582 1586 71 12 N T Correia J M Ramos M Descamps G Collins Molecular Mobility and Fragility in Indomethacin A Thermally Stimulated Depolarization Current Study Pharmaceutical Research 2001 1767 1774 13 K Ogata Modern Control Engineering fifth edition 2010 14 K J Astrom H Tore Advanced PID Control ISA 2006 15 K H Ang G Chong Y Li PID control system analysis design and technology Control Systems Technology IEEE Transactions on Volume 13 559 576 2005 16 K J Astrom C C Hang P Persson W K Ho Towards Intelligent PID Control Automatica Volume 28 Issue 1 1 9 1992 17 Y Li K H Ang G Chong PID control system analysis and design Control Systems IEEE Volume 26 32 41 2006 18 Novocontrol Company User Manual TSDC cell http www novocontrol de html index_tsdc htm 19 X Y Wang D Y Li Mechanical and electrochemical behavior of nanocrystalline surface of 304 stainless steel Electrochimica Acta Volume 47 Issue 24 2002 3939 39
18. of activation energy can be determined What is more the frequency requirement for distinguishing these multiple transition is very low since TSDC is a low frequency technique therefore TSDC is ideal in resolution of weak transition in polymer materials 70 REFERENCES 1 N A D Souza Thermally stimulated depolarization currents in poly ethyleneterephthalate ran p hydroxybenzoates Polymer Engineering amp Science 2001 962 970 2 N A D Souza Thermally stimulated depolarization current International Journal of Polymeric Materials 1998 277 306 3 W D Callister Jr Fundamentals of Materials Science and Engineering fifth edition Department of Metallurgical Engineering University of Utah 2001 4 G M Sessler Electrets second edition University of Darmstadt 1987 5 N Kinjo M Ogata K ANishi A Kaneda Epoxy molding compounds as encapsulation materials for microelectronic devices Advances in Polymer Science Volume 88 1989 1 48 6 H G Kia Sheet Molding Compounds Science and Technology Department of Polymers General Motors Research Laboratories 1993 7 S P DaVanzo R F Hill Enhanced boron nitride composition and polymer based high thermal conductivitymolding compound Advanced Ceramics Corporation 1996 8 J V Turnhout Thermally Stimulated Discharge of Polymer Electrets Elsevier Amsterdam 1975 9 J Laudat F Laudat Dielectric Study of Frozen Aqueous Solutions of Ionic Materials by Means
19. pigment or colorant Other materials such as flame retardants adhesion promoters ion traps and stress relievers are added to the mold compound as appropriate The most popular molding compounds are generally composite materials consisting of epoxy resins phenolic hardeners silica catalysts pigments and mold release agents 6 Epoxy molding compounds for microelectronic devices have been and will continue to be the main stay of encapsulation materials in view of their cost and productivity advantages On the other hand as chip sizes become larger due to increased integration of devices compacter packages are in demand to realize the higher integration Advances in surface mounting technologies demand encapsulation materials which have extremely low thermal stress and excellent stability at the elevated temperatures used in reflow soldering Critical properties considered when selecting a molding compound include its glass transition temperature moisture absorption rate flexural modulus strength coefficient of thermal expansion thermal conductivity and adhesion properties 7 There are many types of molding compounds used in the semiconductor industry today General purpose molding compounds with relatively high flexural strengths but exert relatively larger stresses to the device may be used for large and thick packages such as the PDIP and PLCC Low to ultra low stress molding compounds is preferred for the encapsulation of thin pack
20. temperature range from 200 C to 300 C A Keithley 6517B Multi meter can supply up to 1000V DC voltage to sample and can measure DC current from 10aA to 21mA The vacuum unit creates vacuum environment inside of main chamber which is aim to avoid external factor s effect All experimental data is converted to digital signal and recorded by LabView software The TSDC curve will be plotted automatically by Labview Figure 3 1 presents the overview of the whole TSDC system Figure 3 1 Overview of whole TSDC system 12 3 2 TSDC Cell The TSDC Cell was designed by Novocontrol Company which is a German manufacturer of high tech measuring and automation systems for industrial control and scientific research 18 This sample cell has been designed for measurements of thermally stimulated depolarization current TSDC of solid samples It has a massive stainless steel construction and gold plated electrodes with reliable electrical insulation Integrated interlock switch enables high voltage application only if the cell is mounted into the temperature chamber The connection on the top flange includes a high voltage connector for the high DC polarization and two BNC connectors for the electrometer input Up to 1000V DC voltage can be supplied and 10aA current can be measured It has a wide temperature range from 200 C to 300 C PT100 temperature sensor is integrated to bottom electrode which makes the system to be able to determine sample
21. the Tg are by plotting the enthalpy or entropy v s the polarization temperature and noting the temperature at which the enthalpy is maximum 37 Figure 4 6 Schematic procedure of epoxy window polarization experiment 48 CHAPTER 5 TSDC EXPERIMENT DATA ON EPOXY AND FILLED EPOXY 5 1 TSDC Experiment Data To investigate epoxy and epoxy composite s behaviors under different polarization conditions each sample was polarized under three different voltages 200V 400V and 600V Figure 5 1 to Figure 5 3 show two samples TSDC behaviors comparison under 200V 400V and 600V polarization respectively From the comparison it was known that pure epoxy sample generated higher depolarization current than silica sample in each polarization condition This means silica improve insulation performance IN Q Current p lt a S D Fa I O N o c o Nn 70 90 110 Temperature C aR o Figure 5 1 TSDC curve 600V polarization AR Pure Epoxy 200V Current pA O N 2005 O r2 1096 Silica 200V 50 60 70 80 Temperature C 90 100 Figure 5 3 TSDC curve 200V polarization 49 0 so 60 7d 80 90 100 110 10 significantly than pure epoxy material 50 40 Pure Epoxy 400V 30 20 10 Silica 400V 10 Temperature C Figure 5 2 TSDC curve 400V polarization Figure 5 4 and 5 5 show the comparison of depolarization curre
22. 10 silica composite sample Pure Epoxy Global TSDC Curve 400V 75 C to 73 C IN e UY lt a z D I O 73 C to 71 C 70 C to 68 C 68 C to 66 C 66 C to 64 C 75 op 04 C to 62 C Temperature C Figure 5 8 Window polarization data of pure epoxy sample 52 99 10 Silica Global TSDC 400V 95 C to 93 C N Nn lt a 5 20 E O 90 C to 88 C Nn 85 C to 83 C 80 C to 78 C 75 C to 73 C 85 90 110 Temperature C Figure 5 9 Window polarization data of 10 silica composite sample 5 4 Analysis of TSDC Technique Global TSDC plots are analyzed based on the total relaxed charge Q Due to the overall depolarization process is calculated from the area bound by the TSD peak and the abscissa A is the electrode area and r is the heating rate Q A is the total polarization P There is a linear relation between the relaxed charge and E Plots of current density electric field v s temperature depict conductivity Q 5 fE Mat 1 Assuming that the relaxation is follows either the Debye rotational friction or Frohlich 2 site barrier model and that the relaxation times for polarization and depolarization are equal the decay of the polarization is given by P t B exp 5 2 Where 1 is the dipolar relaxation time Pe is the equilibrium or steady state polarization given by
23. 11 TABLE OF CONTENTS Page ACKNOWLEDGMENTS aane a aeng gada en eas s iv LIST OR TABELES cenna GR iv LIST OF FIGURES sisi iv CHAPTER T INTRODUCTION se 1 CHAPTER 2 LITERATURE REVIEW id A eM AN Ga a 3 2 1 Molding Compounds Materials e 3 22 NT erii m X t 5 2 PDC Lege 7 2 3 1 Proportional Band sc aio oasis 7 23 2 Integral VANE oos aa na I a a naa in a 8 2 3 3 Derivative DIme aoi eit td loe te teet e Ure aana elo nana ae 9 24 PIDCONIUISUPIEBES esee tus das 0 CHAPTER 3 TSDC SYSTEM INSTRUMENTATION DESIGN cree 12 3 1 Overview of the Whole System oed orsa on oq anaa ESRA 12 32 TSDC Collin rada 13 3 3 Mam Ghamber ii ss sesama nia A A td 14 34 Heating O 16 3 4 1 Gas Heater isnin anan RN ia 18 J42 NOG aa ga Eo dah aa a a aa a ga ad gan aa UE 19 34 3 Temperature Controller a 19 OO i eeo 22 iv 3 6 Electrical Unit Voltage Supply amp Current Measurement Unit 24 3 6 1 Capabilities and Features Overview sese 24 3 6 2 Guardin E a he t ye t e e eatea a aa re a a aea es aat 25 3 6 3 Voltage Source Basic Operation 0sosenene anon t tre pa qoi eaae ide 26 3 6 4 Configuring V SOUrCe eser ensem aceto Hae eR reos aaa e Pun ee Marea eu repe 27 3 63 Current Measurements 20 iS ned A ESA 28 3 6 6 Interlock and Test Fixtures scoop Qu n ttu qat intulit 29 SO T Connecting Cables ERE et de M 30 3
24. 3 Guarding diagram of Keithley 6517B meter 3 6 3 Voltage Source Basic Operation Basic operation simply consists of setting the V Source level and placing the V Source in OPERATE to output the voltage Other V Source operations are performed from the CONFIGURE V SOURCE menu to select range 100V or 1000V set voltage limit select resistance current limit and control the LO to LO connection between the V Source and the ammeter 26 Setting V Source level The V Source level is set with the instrument in the normal measurement mode The VOLTAGE SOURCE up and down keys and the cursor keys left and right are used to adjust the voltage level Pressing any one of these four keys will enable the V Source edit mode The flashing digit on the V Source display indicates the cursor position Use the cursor keys to place the cursor on the desired digit and use the VOLTAGE SOURCE up and down keys to adjust the level Polarity can be changed by placing the cursor on the polarity sign and pressing VOLTAGE SOURCE up and down Sourcing voltage The displayed voltage level is applied to the output terminals when the instrument is placed in operate by pressing the OPER key In operate the VOLTAGE SOURCE OPERATE indicator is on Pressing OPER a second time places the V Source in standby 3 6 4 Configuring V Source Perform the following steps to configure the V Source 1 Press the CONFIG key and one of the VOLTAGE SOURCE keys to display the following
25. 47 20 AHP 3741 T Type air Process Heater Application Notes OMEGA Engineering Inc http www omega com pptst AHP_SERIES html 21 COMPRESSED AIR amp GAS INSTITUTE Compressed air and gas handbook 22 Omega Company User Manual CN63100 temperature controller http www omega com pptst CN63100 html 23 S Paul A B Chattopadhyay Effects of cryogenic cooling by liquid nitrogen jet on forces temperature and surface residual stresses in grinding steels Cryogenics Volume 35 Issue 8 1995 515 523 72 24 Keithely Instrument Company User Manual Model 6517B Electrometer High Resistance Meter http www keithley com products dcac voltagesource application mn 6517B 25 R Plonsey R Collin Electrode guarding in electrical impedance measurements of physiological systems Medical and Biological Engineering and Computing Volume 15 Issue 5 1977 519 527 26 Keithely Instrument Company User Manual Model 7078 TRX 3 Low Noise Triax Cable http www keithley com products accessories cables mn 7078 TRX 3 27 LEMO S series connectors application notes http www lemo com en standard range s series domain term node tid 1 28 B P Lathi Modern Digital and Analog Communication Systems 3e Osece third edition Oxford University 1998 29 PT 104A RTD Input Data Acquisition Module Application Notes OMEGA Engineering Inc http www omega com pptst PT 104A html 30 R F Eugene C Jensen C William PET and the
26. 486 t minutes Figure 3 9 TSDC system SPRP heating mode temperature curve 3 5 Cooling Unit The TSDC system use liquid nitrogen to cool down sample A tremendous amount of energy can be taken away when liquid nitrogen is rapidly vaporized 23 This is the basic principle of liquid nitrogen cooling The TSDC system uses a nitrogen container from PLANER Company as shown in figure 3 10 The Container has a 25 liter capacity One solenoid valve is used to turn On Off of the container On the top of container there is one air pressure meter 22 designed to indicate the pressure of container The pipe of liquid nitrogen was connected to main chamber by a specific liquid nitrogen feedthrough from Lesker Company One additional 3 way valve was connected between container pipe and feedthrough The purpose of 3 way valve is to improve system cooling performance After turning on the solenoid valve the temperature of liquid gas comes out from container is not that low It is because the container and pipe themselves need to be cooled down first However TSDC experiment requires cooling down as quickly as possible Therefore liquid gas should not be injected to main chamber at the beginning of cooling process Liquid gas can be injected to outer of chamber by operate 3 way When temperature of liquid gas goes down to extreme low turn 3 way valve to main chamber direction the low nitrogen gas was injected to sample directly at this time TSDC
27. 6 8 LEMO Connector espiral llas 31 3 7 Data ACquisiHoli S YSL id A A neat ede 32 3 7 1 Analog Signal and Digital Signal esee 32 2 Temperature Data E98 ef usos ENE 33 3 7 3 IEEE 488 GPIB card Communication eene 35 SALA END Dui uA cu 36 3 8 Overall Schematic Diagram of TSDC System ooooocccnoccccnoncconnoncnnnnncnnnnnanonanoconnncnnnnnnnnnn 38 CHAPTER 4 TSDC EXPERIMENTAL PROCEDURES eerte rennen 39 4 1 Sample Preparation ace t ie te bI E ERUNT INR XAR saa NUUS A E ga nana SD de CYRUS RAT UR 39 As dl Sample Material eo eerie bete en decies iare 39 42 Sample etii rU 41 41 3 SPEDE id 41 4 2 Procedure of TSDC Experiment ti ii E a 44 4 3 TSPC EXDOEBQUL sida 45 24 Window PolartzdtlptE usd ida 46 CHAPTER 5 TSDC EXPERIMENT DATA ON EPOXY AND FILLED EPOXY 49 SI TSDC Experiment Data a 49 3 2 I SPE Experiments Dagur Gekkonidae 51 5 3 Windows PolattzattOn vegene See 52 54 Analysis of TSDC Technique vuuemsnanmjudrnssnniyndrsnnieiaeesevisseeemi ede 53 CHAPTER 6 ALTERNATIVE TECHNIQUES TO MEASURE THERMAL TRANSITIONS IN EPOXY AND FILLED EPOXY iii 60 6 1 Dicl cire Amal ysis 3 2 65 santos GS ne ee oc a A e E 60 6 2 DMA 3 Point Bending Test 1 525 iere Or ers e ere eda ea rend ss deecdavantesante 64 0 VS Te 67 64 MGISDUTE Teste eee 68 CHARTER 7 SUMMARY Vee 70 REFERENCES susi saa SA EN E E RR 71 vi LIST OF TABLES Page Table 3 1 Port Function Li
28. CN63100 temperature controller SPRP mode diagram 22 Figure 3 9 TSDC system SPRP heating mode temperature curve 0eeo0e00ooeo nenen ne anane 22 Figure 3 10 Overview of heating unit of TSDC system eese eene nnn 23 Figure 3 11 Overview of electrical unit of TSDC system eene 24 Figure 3 12 Connection diagram between TSDC cell and 6517B meter sess 25 Figure 3 13 Guarding diagram of Keithley 6517B meter sse 26 Figure 3 14 Current measurement diagram of Keithley 6517B meter esses 29 Figure 3 15 Interlock diagram of Keithley 6517B meter seen 30 viii Figure 3 16 Cable used in TSDC S ystem 4 nei bi a dte ia 30 Figure 3 17 LEMO connectors used m TSDC System uassdas rsdndtsjalkgndamemene 31 Figure 3 18 Temperature signal acquisition unit PT 104A data logger 34 Figure 5 19 GPIB card for Keithley 6517B meter cuna ai 35 Figure 3 20 LabVIEW software interlace ion ideas 37 Figure 3 21 LabVIEW software program for TSDC system aaa a aee ae anana nana aan anana anana 37 Figure 3 22 Diagram of whole TSDC SySteltbosnnxite etti tio ipe qu tdi 38 Figure 4 1 Tempered glass mold for epoxy sample seen 41 Figure 4 2 Model 5100 sputtering coater ceed etas stas satan nana n anana anan anan anae nane nu ek en vo
29. Keithley6517B Current Measurement Pico Ammeter DC Voltage supply Interlock security Cooling Unit Heating Unit Temperature Liquid Nitrogen Hot air heater Controller RTD Temperature RTD Temperature Sensor data logger LabVIEW Figure 3 22 Diagram of whole TSDC system ese 38 CHAPTER 4 TSDC EXPERIMENTAL PROCEDURES 4 1 Sample Preparation As an extremely sensitive and accurate technique the TSDC investigation has strict requirement for samples The surface of solid samples should be as flat as possible to make good contact with the electrodes Therefore mold for TSDC sample should have smooth surface or polish the contact surface of solid sample after curing What is more metallizing the sample surface is highly recommended Metallizing the sample surface can create one external electrode which can make better contact with TSDC cell electrodes This can be done by sputtering Samples should have uniform thickness Uneven thickness results in bad contacts which is One important error source for TSDC test It may reduce the current produce noise or cause additional peaks due to electrode polarization Under the same polarizing condition thinner samples can be polarized at higher level Therefore to achieve higher polarization the TSDC test requires thin samples In addition be aware high pressure between the electrodes is generally not suitable to improve bad contacts Therefore sample should not be wrested too tightl
30. THERMALLY STIMULATED DEPOLARIZATION CURRENT EVALUATION OF MOLDING COMPOUNDS Shunli Zhao Thesis Prepared for the Degree of MASTER OF SCIENCE UNIVERSITY OF NORTH TEXAS May 2014 APPROVED Nandika A D Souza Major Advisor Tae Youl Choi Committee Member Xun Yu Committee Member Yong Tao Chair of the Department of Mechanical and Energy Engineering Costas Tsatsoulis Dean of the College of Engineering Mark Wardell Dean of the Toulouse Graduate School Zhao Shunli Thermally Stimulated Depolarization Current Evaluation of Molding Compounds Master of Science Mechanical and Energy Engineering May 2014 74 pp 7 tables 76 figures reference 38 titles TSDC thermally stimulated depolarization current is one of the most important and popular technique for investigating electret materials TSDC technique can indicate the magnitude of polarization and depolarization relaxation time charge storage glass transition and activation energy To fully investigate polarization and relaxation for pure epoxy and filled epoxy materials a TSDC system was built and verified by the research The article describes the building processes and verification of the TSDC system TSDC TSPC and TWC tests data for epoxy and filled epoxy samples are presented in the article To compare TSDC technique with other related techniques DEA dielectric analysis DMA dynamic mechanical analysis and DSC differential scanning calorimetry tests a
31. agent with ratio 100 50 Stir the mixed liquid sample nicely with glass rod To have smooth surface sample a glass mold was used to cure the sample For TSDC test the thinner sample the higher polarization will be achieved Therefore to get a thin sample put 3 layer papers between two glass molds as shown in figure 4 1 compress two molds after placing liquid sample inside A 0 25mm thickness sample is achineved Liquid sample was cured at 180 C for 30 minutes at the beginning and then cured at room temperature for another 7 hours For the filled epoxy silica samples add 10 silica powder when mixing epoxy and agent stir nicely and repeat the procedure above Figure 4 1 Tempered glass mold for epoxy sample 4 1 3 Sputtering As discussed in section 4 1 to have a good electrical contact between sample and TSDC cell electrodes metallizing the sample surface by sputtering is needed 35 As shown in figure 4 2 SEM Sputtering coater Model 5100 from POLARON instruments Inc was used to sputter the sample Procedure of sputtering 36 1 Place epoxy sample in the environmental chamber and close the chamber 41 2 Turn the OPERATION SWITCH on the front panel to the PUMP position Wait until the gauge shows a ready of 0 1 mbar the time to achieve this will depend on how long the system has been open to the atmosphere and the pump down will be particularly slow when first using a new unit 3 Open leak value by rotating it ab
32. ages High thermal conductivity molding compounds on the other hand are required to encapsulate high power devices Molding compounds used for surface mount devices may have a low moisture absorption rate or a high flexural strength at board mounting temperatures or a combination of both in order to prevent popcorn cracking Proper molding compound selection will prevent problems associated with manufacturability package stress package cracking and interfacial delamination Mold compounds have evolved over the years to keep pace with industry needs 7 Each innovation in chip or package design required a similar change in the design of the encapsulant In 1969 encapsulants typically were filled with fused silica at about a 68 percent w w loading Currently materials are filled with 90 percent fused silica This shift was not made for reasons of cost but driven by end user performance requirements Over the last decade every raw material and process in mold compounds has been re examined and almost all have seen major changes 2 2 TSDC Concept As summarized by D Souza 1 2 thermally stimulated discharge TSD measures the dielectric relaxation of materials through measurement of a field induced thermally stimulated depolarization current TSDC also referred to as ionic thermo current technique 8 Under simultaneous application of electric field during a temperature ramp the orientation of the dipoles results in the formation of
33. an electret The first electrets were formed by Eguchi The use of TSDC is in no way limited to polymeric materials 9 However since dielectric relaxation is due to hindrance of the motions of the permanent dipoles and free charges by frictional forces application to polymers has been widespread TSDC measurements have been traced to Frei and Groetzinger in a review by Vanderschueren and Gasiot 10 The technique was applied to a series of complex systems by numerous researchers including Gross Wikstroem Gubkin and Matsonashvili and Murphy 11 Relating these relaxations to fundamental mechanisms of charge storage and release in nonmetallic systems was initiated by Bucci and Fieschi One of the first detailed investigations on its potential in polymers was initiated by van Turnhout As Vanderschueren points out this technique was developed independently by several researchers It is worthwhile to clarify that TSD is also referred to as electret thermal analysis thermalcurrent spectra thermally stimulated depolarization and thermally activated depolarization Applications to amorphous and semicrystalline polymers have been reviewed by Bernes The sensitivity of TSD to small fractions of uncured material extends its use to thermosetting systems In addition TSD is useful in establishing differences based on tactility and chemical structure water absorption interfaces in composites etc Its applicability to a wide variety of parameters has been r
34. configuration menu RANGE Select the 100V range or 1000V range V LIMIT Control on off and set a voltage limit absolute value RESISTIVE LIMIT Control on off the resistive 1M current limit METER CONNECT Control on off the internal connection between V Source LO and ammeter LO 2 Use the menu items to configure the V Source A menu item is selected by placing the cursor on it and pressing ENTER Options for a menu item are selected in the same way Parameter values are changed using the cursor keys left and right and the RANGE keys up and down and then pressing ENTER 27 3 Use the EXIT key to back out of the menu structure 3 6 5 Current Measurements The diagram of current measurement is shown in figure 3 14 the basic procedure is as follows 1 With zero check enabled ZeroCheck displayed select the amps function by pressing I The Z CHK key is used to enable or disable zero check 2 To achieve optimum accuracy for low current measurements zero corrects the Model 6517B To do this use the RANGE down key to select the lowest measurement range 20pA and press REL With zero correct enabled the REL indicator is on and the message ZCor is displayed 3 Select a measurement range or use auto ranging a To automatically select the most sensitive range enable auto range The AUTO key enables and disables auto range When enabled the AUTO annunciator is on b For manual ranging use the RANGE up and
35. curve for epoxy sample and silica filler sample The glass transition starts from approximate 70 C 67 Pure Epoxy DB N O Epoxy Ceramic 10 weight Nel z E E 3 Rh a n ON N 00 80 110 140 170 200 230 Temperature C Figure 6 17 DSC curve 6 4 Moisture Test To investigate moisture effect for sample s mechanical property dielectric property and thermal property moisture test was introduced for the investigation The humidity chamber holds temperature at 85 C and maintains the humidity magnitude at RH 85 Samples were placed in humidity chamber at a certain time The samples were removed and weighted every 4 hours did DMA DEA and DSC test restively to obverse sample s performance under different moisture level Figure 6 18 presents the moisture gain weight curve for two samples Figure 6 19 to 6 24 show two sample s DEA Test under 0 4 20 and 48 hours immersion Pure Epoxy E Epoxy Ceramic Relative Weight Gain 10 20 30 40 Time hours Figure 6 18 Sample moisture gain weight curve 68 e pf m Dry Status m gt Dry Status 12 d hours 4 hours soaking 9 soaking 20 hours 6 2 hours soaking soaking A 48 hours 9 48 hours soaking 0 soaking 20 40 60 4 80 100 20 40 60 80 100 Temperature C Temperature C Figure 6 19 Pure epoxy humidity test e Figure 6 20 10 silica sample humi
36. dity test e 2 5 2 Dry Status 1 5 4 hours E soaking o 20 hours 0 5 soaking 48 hours 0 soaking id Temperature Zo we 20 40 60 20 100 Temperature Figure 6 21 Pure epoxy humidity Test e Figure 6 22 10 silica sample humidity test e Dry Status Dry Status 4 hours 4 hours soaking soaking 20 hours 20 hours soaking soaking 48 hours 48 hours soaking soaking 40 60 80 100 20 40 60 80 100 Temperature Temperature C Figure 6 23 Pure rpoxy humidity test detan Figure 6 24 10 silica sample humidity test delta detan delta 69 CHAPTER 7 SUMMARY To fully investigate polarization and relaxation for pure epoxy and filled epoxy a TSDC system was designed and verified to do TSDC TSPC and TWC tests To investigate dielectric property for epoxy and filled epoxy DEA test was introduced for this research A DMA test was done to determine samples mechanical performance as function of temperature DSC test data indicates samples thermal properties What is more to investigate moisture s effect for two samples moisture test was introduced All the test data were listed in chapter 5 and chapter 6 By the comparison between different techniques TSDC technique is more sensitive in resolving polymer glass transition analysis By window polarization test each individual particle s behavior can be determined accurately Meanwhile a range
37. down keys to select a measurement range consistent with the expected current CAUTION Do not apply more than 250V peak DC to 60Hz 10 seconds per minute maximum on mA ranges or instrument damage may occur 4 Press Z CHK to disable zero check and take a reading from the display To disable zero correct enable zero check and then press REL 28 WARNING No INTERNAL OPERATOR SERVIC Triax B PREAMP OMAIN con Red HI Cable E IN 1250V pk 4 me Measured nO 5 V SOURCE Black LO O OPTION SLOT a TRIGC Recommended N CAUTION For CONTINUED PROTECTION AGAINS below 111A Input low connected to shield Figure 3 14 Current measurement diagram of Keithley 6517B meter 3 6 6 Interlock and Test Fixtures The voltage source should be used with a test fixture that incorporates a safety interlock switch By using the interlock feature the Model 6517B cannot source voltage when the lid of the test fixture is open or ajar Interlock is automatically enabled when the appropriate interlock cable is connected to the Model 6517B It is important to note that V source will not operate unless the interlock is activated When interlock is used with TSDC cell V source will go into standby whenever the lid of the test fixture is open or ajar Use the Interlock Cable as shown in Figure 3 15 This cable uses an extra line to detect which resistivity measurement type is selected at the test fixture
38. e at setpoint 22 Manual mode is a open loop control There is no temperature signal feedback to controller Operators can control output percentage manually 22 19 ON OFF mode controller only provides 0 and 100 output and keep switching between two outputs during test 22 SPRP mode controller allows heaters to heat up at a controllable rate Figure 3 7 OMEGA CN63100 temperature controller 3 4 3 2 Polarization Heating and Depolarization Heating The TSDC experiment contains two heating processes polarization heating and depolarization heating Polarization heating requires heating up sample as fast as possible Time proportional mode meets this requirement Controller is set to 100 output Nitrogen gas can be heated up to 300 C in three minutes The depolarization heating stage of the experiment requires heating up sample at a slow rate for example 4 C minute In this case SPRP mode plays an important role The SPRP feature can ramp the process at a controlled rate SPrP 0 0 to 999 9 C minute A ramp value of zero disables setpoint ramping allowing the controller to stabilize as fast as possible to the new setpoint Setpoint ramping is initiated on power up or when the setpoint value is changed Active setpoint ramping is indicated by the left most decimal point flashing in the main display 20 Once the ramping setpoint reaches the target setpoint the setpoint ramp rate disengages until the setp
39. e equals the output due to derivative action with a ramping process error 15 As long as a ramping error exists the derivative action is repeated by proportional action every derivative time The units of derivative time are seconds per repeat 22 Figure 2 4 shows one example of derivative time control Derivative action is used to shorten the process response time and helps to stabilize the process by providing an output based on the rate of change of the process 16 In effect derivative action anticipates where the process is headed and changes the output before it actually arrives Increasing the derivative time helps to stabilize the response but too much derivative time coupled with noisy signal processes may cause the output to fluctuate too greatly yielding poor control None or too little derivative action usually results in decreased stability with higher overshoots No derivative action usually requires a wider proportional and slower integral time to maintain the same degree of stability as with derivative action Derivative action is disabled by setting the time to zero 17 DEVIATION TIME OUTPUT PROPORTIONAL OUTPUT POWER DERIVATIVE OUTPUT TIME NOTE TOTAL OUTPUT POWER IS THE SUM OF THE THREE PID SETTINGS DERIVATIVE TIME Figure 2 4 Derivative time 2 3 4 PID Adjustments To aid in the adjustment of the PID parameters for improving process control a chart recorder is necessa
40. ecently reviewed 12 The principal set up of a TSDC experiment is shown in figure 2 1 The sample is placed between two electrodes of a sample capacitor The sample can be polarized charged by applying a voltage to the sample under the temperature higher than glass transition After cooling down system quickly to freeze the polarization sample will be heated up again at a constant heating rate during this heating process the depolarization current can be measured as a function of time and or temperature Capacitor Electrodes IN FN PA PA Sample Capacitor Polarization High Voltage Source Switch Current Measurement Figure 2 1 The principal set up of a typical TSDC experiment from Novocontrol manual A TSDC system should have these functions and capabilities a Provide an enclosed and stable environment for testing b Be able to control sample temperature as experiment s requirement fast heating slow heating and fast cooling c High DC voltage source to supply polarization voltage to sample d Contain accurate Pico ammeter to measure depolarization current e Data acquisition system 2 3 PID Control 2 3 1 Proportional Band Proportional band is defined as the band range the process changes to cause the percent output power to change from 0 to 100 13 The band may or may not be centered about the setpoint value depending upon the steady state requirements of the process The band is shift
41. ed by manual offset or integral action automatic reset to maintain zero error Proportional band is expressed as percent of input sensor range 14 Example as shown in figure 2 2 thermocouple type T with a temperature range of 600 C is used and is indicated in degrees Celsius with a proportional band of 5 This yields a band of 600 C X 5 30 C 22 The proportional band should be set to obtain the best response to a disturbance while minimizing overshoot Low proportional band settings high gain result in quick controller response at expense of stability and increased overshoot Settings that are excessively low produce continuous oscillations at setpoint High proportional band settings low gain result in a sluggish response with long periods of process droop A proportional band of 0 0 forces the controller into ON OFF control mode with its characteristic cycling at setpoint OUTPUT REVERSE DIRECT POWER ACTING ACTING P BAND P BAND O1 01 100 TEMPERATURE HEATING COOLING SETPOINT Figure 2 2 Proportional band feature of CN63100 controller 2 3 2 Integral Time Integral time is defined as the time in seconds in which the output due to integral action alone equals the output due to proportional action with a constant process error 15 As long as a constant error exists integral action repeats the proportional action each integral time Integral action shifts the center point posi
42. gns to the field A TA instrument ARES strain controlled shear rheometer and an Agilent E4980A multimeter are used to test dielectric properties of the samples Samples were cut to 25mm parallel plate geometry for experiment During the test to prevent piezoelectric effects no axial force was applied to sample For the temperature scan test Agilent E4980A multimeter applies 1V DC voltage to sample The frequency of electrical field maintains at 20Hz The temperature scan range is from 30 C to 225 C For the frequency scan test Agilent E4980A still supplies 1V DC voltage to sample Maintain temperature at 110 C 120 C 130 C 140 C 150 C 160 C and 170 C respectively The frequency range was from 20Hz to 2E 06Hz For both tests the real component of the dielectric constant imaginary component and tan 6 were obtained from DEA test Figure 6 1 6 2 and 6 3 show temperature scan data of epoxy sample and silica filler sample Figure 6 4 to 6 9 show frequency scan data for two samples respectively Master 60 curve of DEA test is shown in figure 6 10 Through master curves material s activation energy was determined 9 8 Pure Epoxy 7 Pure Epoxy 26 v5 4 Pure Epoxy 3 Pure Epoxy Ceramic 2 Ceramic 10 weight 10 1 weight 0 30 80 130 180 230 T degree C Figure 6 1 DEA temperature scan test e 30 80 130 180 230 T degree C Figure 6 2 DEA temperature scan test e
43. hamber is grounded strictly Four ground wires were used to connect main chamber to ground As a temperature chamber the chamber body should have low thermal conductivity To improve chamber s thermal insulation performance one clay inner which has low thermal conductivity is added to chamber Table 3 1 Port Function List of Main Chamber Port No Function 1 Backup 2 Electrical feed through 3 Liquid nitrogen feed through 4 Heating gas feed through 5 Visible port S Vacuum pum opposite to port 5 KOMP 7 Backup 15 Figure 3 3 3D design of main chamber and real picture m typ 4 Y Z typ Rte A port i anges 230 000 ed Groove LD Figure 3 4 Dimension of main chamber 3 4 Heating Unit The heating function of the TSDC system is achieved by hot nitrogen gas Gas heater from Omega Company is used to heat up compressed air as shown in figure 3 5 Hot gas is 16 injected to sample directly by a gas feeedthrough and nozzle which are connected to the main chamber To make the main chamber have satisfied thermal insulation performance clay thermal insulation is attached to the inner surface of the main chamber By using hot gas heating unit sample could be heated up to 300 C The TSDC experiment not only requires system to heat up sample as fast as possible but also requires a controllable slow heating For quick heating hot gas is able to heat up sample to
44. ially for patch panels 27 The LEMO special self latching system makes it possible to connect and disconnect with a simple axial push pull thereby reducing the space needed to mount sockets to an absolute minimum up to 50 sockets per square decimeter LEMO series S Coaxial Connector series served as the norm for NIM CAMAC CD N549 standard used in nuclear physics as well as many other applications Figure 3 17 LEMO connectors used in TSDC system 31 The features and technical specification of LEMO series 00 Coaxial Connector are shown below e Push Pull self latching e 8 sizes e Multi pole with stepped inserts e Ocolor coding e Over 50 shell styles e UL recognized e Temperature range 55 C to 250 C e Solder or print contacts e Shielding gt 75dB at 10 MHz gt 40dB at 1 GHz 3 7 Data Acquisition System 3 7 1 Analog Signal and Digital Signal An Analog signal is any continuous signal for which the time varying feature variable of the signal is a representation of some other time varying quantity 1 e analogous to another time varying signal It differs from a digital signal in terms of small fluctuations in the signal which are meaningful 28 A digital signal uses discrete discontinuous values By contrast non digital or analog systems use a continuous range of values to represent information Although digital representations are discrete the information represented can be either discrete such as numbers
45. ilica Composite Figure 5 15 Activation energy as function of temperature for pure epoxy sample and 10 silica composite ao c o c Pure Pure Epoxy Epoxy 10 Silica Composite IN o 10 Silica Composite Figure 5 16 Enthalpy value as function of Figure 5 17 Entropy value as function of polarization temperature polarization temperature Enthalpy Kcal mol N ON o o 58 4 Pure Epoxy y 2 2584x 20 256 O o Q 2 m a e E E m 10 Silica Composite y 2 2 6202x 28 771 50 100 150 Enthalpy Kcal mol Figure 5 18 Enthalpy and entropy relationship 59 CHAPTER 6 ALTERNATIVE TECHNIQUES TO MEASURE THERMAL TRANSITIONS IN EPOXY AND FILLED EPOXY 6 1 Dielectric Analysis A dielectric material is an electrical insulator that can be polarized by an applied electric field When a dielectric is placed in an electric field electric charges do not flow through the material as they do in aconductor but only slightly shift from their average equilibrium positions causing dielectric polarization Because of dielectric polarization positive charges are displaced toward the field and negative charges shift in the opposite direction This creates an internal electric field that reduces the overall field within the dielectric itself If a dielectric is composed of weakly bonded molecules those molecules not only become polarized but also reorient so that their symmetry axis ali
46. ively short history it has already evolved into a basic tool for the identification and evaluation of dipole reorientation processes and of trapping and recombination levels 5 Its rapid growth has been spurred on by the fact that charge trapping and charge transport phenomena are not only of vital importance for electrets but also for materials used in thin films photoconductors electro optical devices etc CHAPTER 2 LITERATURE REVIEW The objective of this research is molding compounds materials section 2 1 shows the background information for molding compounds materials The basic principle and history for TSDC technique is discussed in section 2 2 PID concept and application is discussed in section 2 3 2 1 Molding Compounds Materials Mold compounds are the plastics used to encapsulate many types of electronic packages from capacitors and transistors to central processing units CPUs and memory devices The modern mold compound has evolved into a complex formulation containing as many as 20 raw materials and multiple processing steps each statistically controlled to yield a uniform and predictable end product 5 At the most basic level mold compounds contain five classes of raw materials Organic resins are typically meltable Fillers are non melting inorganic materials Catalysts accelerate the cure reaction 5 The mold release material allows the naturally adhesive resin to come out of the mold The final raw material is a
47. module for use with PT100 and PT1000 RTD sensors It can also be used to measure resistance 375 Q and 10 000 Q ranges and voltage 115 mV or 2 5 V ranges In PT100 PT1000 resistance mode the unit uses a four wire circuit 29 In voltage mode the input connector can be treated as a differential input with ground or two single ended inputs Both inputs must be OV or above though it does not matter which input has the higher voltage For the 115 mV voltage range the accuracy may vary by 2 and the temperature coefficient will be 100 ppm C 33 Although accurate temperature sensors are widely available it has been difficult to take advantage of them due to errors caused by the measuring device The PT 104A however is designed to be inherently accurate Rather than relying on voltage references which tend to be temperature sensitive it uses reference resistors which are extremely stable low temperature coefficient and drift The exact value of each resistor is stored in an EEPROM to provide the ultimate in accuracy yearly re calibration is recommended To achieve the 0 001 C resolution a highlyadvanced ADC is used that can resolve to better than 1 part in 16 million The PT 104A measures temperature using platinum resistance temperature sensors RTDs Both common industry standards PT100 and PT1000 are supported The unit is compatible with 2 3 and 4 wire sensors 4 wire PT100 sensors are recommended for accurate measureme
48. mple leo RD eo a a 57 Figure 5 14 log t vs 1 T plot for 10 silica composite sample eee 57 Figure 5 15 Activation energy as function of temperature for pure epoxy sample and 10 Silica COMPOSITE iii ee v Der e A REA OE AN EA CU NA ag AE Aaa e Lugo de os Ban 58 Figure 5 16 Enthalpy value as function of polarization temperature 58 Figure 5 17 Entropy value as function of polarization temperature see 58 Figure 5 18 Enthalpy and entropy relationship iate tot ee ti ile 59 Figure 6 1 DEA temperature scan test vull 61 Figure 6 2 DEA temperature scan test e ai tias 61 Figure 6 3 DEA temperature scan test detan delta vinil 61 Figure 6 4 Pure epoxy sample DEA frequency scan test e cococococccnocnconncnonononnnonn nono ncnoncnnncnnnnnons 62 Figure 6 5 10 silica filler sample DEA frequency scan test e aaa aee ena nenen a nen an anae nane 62 Figure 6 6 Pure epoxy sample DEA frequency scan test e 62 Figure 6 7 10 silica filler sample DEA frequency scan test mmmmmrnrerevrrenvnrnnrnrvrarevrrenvnrvvrsen 62 Figure 6 8 Pure epoxy sample DEA frequency scan test detan delta sss 63 Figure 6 9 10 silica filler sample DEA frequency scan test detan delta 63 Freure 6 I0 Mastercurve of DEA festspela BA ede 63 Figure 6 11 Shift factor of DEA master Curves ieu on eite pu LANG 63 Figure 6 12 DMA
49. n Figure 4 6 The main procedures of one window polarization experiment are below e Sample is polarized at T for time tp tp is varied to orient different fractions of the dipoles e Sample is quenched to temperature Ta Tp Ta gt 10 K e Polarizing field is switched off and Ty maintained for time ta Depolarization of dipoles that are mobile at or below Tg occurs leaving only dipoles oriented that have mobility in the temperature window of T Ta e Sample is quenched to T lt lt Ta e Sample is heated to temperature T gt T at programmed rate allowing relaxations related to temperature window T T to relax By doing this at several temperature a set of individual depolarization curves for each polarization temperature are obtained that are subsets of that obtained by the global TSC spectra Elementary modes can be isolated and materials relaxation map constructed using window polarization to separate out mixed peaks having small separations has proved useful to also separate the effect of the electret discharge from the glass transition 37 As reviewed by Ibar etal window polarization and the resultant RMA allows small relaxation differences between a slowly cooled and cooling chemical composition and percentage cross linking to be detected Analysis of RMA curves is aimed at correlating the simple relaxation modes with the thermokinetic and thermodynamic parameters of the material 47 Alternative means of obtaining
50. n table 5 1 N S EN AR Pure Epoxy 200V TSPC o A m D a z D Fa I gt O 10 Silica Composite 200V TSPC lt 2 z EN O 6 oo S 60 70 80 90 100 Temperature C 100 50 Temperature Figure 5 6 TSPC 200V Figure 5 7 TSDC 200V Table 5 1 Curve Coordinate Area Comparison between TSDC and TSPC TSPC K pA TSDC K pA Pure Epoxy 1748 39 243 04 10 Silica Composite 1405 18 144 30 51 5 3 Windows Polarization To validate TSDC system s advanced performance and investigate epoxy sample s window polarization characteristic window polarization experiment for pure epoxy and 10 silica samples under 400 volts polarization voltage were investigated As the discussion in chapter 4 to isolate each individual particle s contribution for global depolarization current peak sample was polarized at every 2 C 38 For instance the sample was polarized at 80 C 400 volts Instead of cooling sample to 100 C sample was cooling down to 78 C maintain this temperature for 5 minutes then cool down to 100 C consequently In this case only dipoles in the temperature window 78 C to 80 C were oriented Consequently for the 2nd heating the depolarization current was only comes from 78 C to 80 C range dipole polarization Figure 5 8 shows the window polarization curve of pure epoxy sample Figure 5 9 shows the window polarization curve for
51. ned at nearly the same temperature throughout the experiment Generally the temperature program for a DSC analysis is designed such that the sample holder temperature increases linearly as a function of time The reference sample should have a well defined heat capacity over the range of temperatures to be scanned The technique was developed by E S Watson and M J O Neill in 1962 and introduced commercially at the 1963 Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy The first adiabatic differential scanning calorimeter that could be used in biochemistry was developed by P L Privalov and D R Monaselidze in 1964 The term DSC was coined to describe this instrument which measures energy directly and allows precise measurements of heat capacity A Perkin Elmer DSC6 Norwalk CT USA was used for DSC investigation An inert atmosphere of nitrogen was used during all the testing to protect sample from oxidizing Cut sample to 10 to 12 mg piece and placed it in an aluminum pan with 30 ul capacity Covered the pan with aluminum lid The samples were first heated from 30 to 275 C at 10 C minute and maintained at 275 C for 5 minutes to ensure sample completely relax and eliminate the blending process thermal history Samples were then cooled down to 30 C at 10 C minute After holding for another 5 min at 30 C samples were heated to 275 C to study the behavior in the absence of the process history Figure 6 17 shows DSC
52. nnection diagram between TSDC cell and 6517B meter 3 6 2 Guarding Guarding should be used for low current 1mA measurements and for voltage measurements to improve system s accuracy In a high impedance circuit guarding greatly reduces leakage currents When using long input cables guarding cancels the effects of cable capacitance that can significantly slow down the measurement response time 25 When GUARD is enabled the INPUT triax connector is reconfigured to apply the guard potential to the inner shell of the INPUT triax connector With this configuration the COMMON 29 banana jack is used for input low Figure 3 13 shows both the guarded and unguarded configurations for the INPUT connector Perform the following steps to enable or disable guard 1 Press CONFIG and then V to display the volts configuration menu 2 Use the and keys to place the cursor blinking menu item on GUARD and press ENTER 3 Place the cursor on the desired selection OFF to disable or ON to enable and press ENTER 4 Use the EXIT key to back out of the menu PANES COMMON 2V OUT 06606 ket Tr S JP I Green eR Log RANG A Tum pee E C Wm J DIGITAL VO oo Ega D Q omae A h i TRIGGER LINK RS232 CAUTION For CONTINUED PROTECTION AGAINST FIRE HAZARD REPLACE FUSE WITH SAME TYPE AND RATING Guard Safety Safety Earth Shield Ground Figure 3 1
53. nt under different voltage polarization for pure epoxy sample and epoxy composite sample respectively These contrasts indicate that higher voltage polarization generated higher depolarization current Two samples present the same trend Current pA Temperature C Pure Epoxy 600V Pure Epoxy 400V Pure Epoxy Figure 5 4 Pure epoxy sample depolarization current comparison among different polarization voltages Current pA 90 Temperature C 10 Silica 600V 10 Silica 400V 10 Silica 200V Figure 5 5 Epoxy silica composite sample depolarization current comparison among different polarization voltages 50 5 2 TSPC Experiment Data The TSPC experiment data for pure epoxy sample and 10 silica composite sample were shown in figure 5 6 The sample for TSPC test should be in un polarized status which means samples has no thermal history and all dipoles are randomly oriented Cool down sample to 20 C and turn on electrical field Heat up sample at rate of 10 C minute Positive charges drift towards cathode and negative towards anode during the heating process This thermally stimulated transition from neutrality to a polarized state generates charging current as a function of temperatures To make a comparison between TSDC curve and TSPC curve figure 5 7 shows the TSDC curve of two samples The curve coordinate area comparison between TSDC and TSPC curve for two samples is show i
54. nts Figure 3 18 Temperature signal acquisition unit PT 104A data logger 34 3 7 3 IEEE 488 GPIB card Communication The IEEE 488 bus which is also frequently referred to a GPIB General Purpose Interface Bus is a communication system between two or more electronic devices a device can be either an instrument or a computer 30 IEEE 488 bus was designed as a parallel transfer medium to optimize data transfer without using an excessive number of bus lines In TSDC system GPIB card from National Instrument Company shown in figure 3 19 is used to connect Keithley 6517 pico ammeter and PC Figure 3 19 GPIB card for Keithley 6517B meter The IEEE 488 bus usually contains eight data lines that are used for both data and with most commands Five bus management lines and three handshake lines round out the complement of bus signal lines 31 On the bus only one device can talk at a time and is addressed to talk by the controller The device that is talking is known as the active talker The devices that need to listen to the talker are addressed to listen by the controller Each listener is 35 then referred to as an active listener Devices that do not need to listen are instructed to unlisten The reason for the unlisten instruction is to optimize the speed of bus information transfer since the task of listening takes up bus time The signal lines on the IEEE 488 bus are grouped into three different categories Data line
55. oint is changed again If the ramp value is changed during ramping the new ramp rate takes effect 3 4 3 3 SPRP Mode Parameter Setup The default output mode of controller is time proportional mode To set up SPrP operators need to follow the procedure as below gt Enter parameter mode by pressing the P button from the Normal Display Mode gt Continue pressing P button go to Controller Configuration CNFP then press the Up arrow After enter Controller Configuration continue pressing P button to go to SPRP mode until SPrP is shown on the top display gt The parameter value of SPrP will flash on the top display use up and down arrow to input ramping rate we want gt Note 0 means the SPrP mode is not activated gt Press P button to confirm the input gt Press D button to go back to normal display mode Since there are two heating processes during TSDC experiment When heating unit finish temperature ramping and want to go back to normal time proportional mode please repeat the procedure above and input SPrP value as 0 One schematic diagram of SPrP output mode is shown in figure 3 8 Figure 3 9 is the heating curve of TSDC system under the control of SPrP mode 21 SETPOINT TARGET 500 pe EEE SS ee RAMP TERMINATED RAMP INITIATED INITIAL 200 TIME SETPOINT CHANGED 10 MINUTES Figure 3 8 OMEGA CN63100 temperature controller SPRP mode diagram y 4 0773x 63
56. ope and intercept allows the calculation of the activation energy and the pre exponential factor for equation 7 Based on window polarization data the relaxation time variation with temperature can be estimated in each TSDC window 1 T is calculated following the BFG area method Assuming Arrhenius relaxation times for each elementary peak t T to exp Eaj kT 7 Where the activation energy Eai and the pre exponential factor toi characteristic of each process are calculated from the slope and the intercept of the log t vs 1 T plot Activation energy is now obtained from the slope of log tT vs 1 T Compensation relations for zero entropy are now determined by the non zero enthalpy intercept denoted as H barrier height for the reverse reaction in the Eyring activated rate formulation To obtain the compensation coordinates Crine s relation is 2h H Ed s T exp exp E GK av 8 55 1 h H Te tes expe 9 Figure 5 11 and F igure 5 12 plot the t vs 1 T curve for two samples Compensation coordinates were obtained In figure 5 13 and 5 14 the log t vs 1 T plot for pure epoxy sample and 10 silica sample are presented Through log ti vs 1 T plot the activation energy Eai for each polarization window was determined by the slope of the linear line SC 73 C me 73 C 71 C 70 C 68 C 68 C 66 C 66 C 64 C 64 C 62 C 22l AA Pd fag 2
57. out 30 seconds with the gauge indicating 0 5 mbar Close the leak valve and allow the system to pump down If the unit is clean and free from contamination a pressure of about 0 01 mbar will be reached 4 Close leak valve and pump down to about 0 04 mbar Turn OPERATION SWITCH on front panel to SET HT position and turn voltage control knob to 2 5KV The milli ammeter will indicate 5 10 mA or less 5 Gradually open leak valve until milli ammeter reads 20mA A plasma glow will be observed as soon as the voltage is applied and a current of about 5 mA is flowing The specimen stage becomes covered with a gold film 6 Turn OPERATION SWITCH on front panel to TIMER position For epoxy sample set timer for 4 minutes Figure 4 3 show the epoxy film sample before and after sputtering 7 When sputtering is finished turn the vent valve fully open 3 4 rotations to vent the system to argon Note that there is a vent valve in the top plate which can be used to admit air to the system after sputtering Although this is much faster than venting to argon a longer pump down may subsequently be observed 8 Turn OPERATION SWITCH on front panel to OFF position If samples have smooth surface and good contact with electrodes no requirement for using sputtering 42 Figure 4 2 Model 5100 sputtering coater Figure 4 3 Epoxy film sample for TSDC experiment left before sputtering right after sputtering 43 4 2 Procedure of TSDC Experiment
58. re introduced Copyright 2014 by Shunli Zhao 11 ACKNOWLEDGEMENTS This thesis has been made possible by three important groups of people in my life Professors Firstly I would like to express the greatest gratitude to my adviser Dr Nandika Anne D Souza who supported my whole graduate study She taught me a lot of wisdoms which are not only for study but also for life Those wisdoms will guide my whole life It is my honor to be her students I would like to acknowledge my thesis committee members Dr Xun Yu and Dr Tae Youl Choi Dr Choi provided me with excellent support to enable me to select parts for TSDC system Thanks for Dr Choi s great contribution on building TSDC system Dr Xun Yu enabled me to learn controls for the system design Family and Friends Thank my parents who gave me life and raised me up All the glory I got is belonged to them Thank my sister for taking care of our parents during the time I am away Thanks my lab mate Mangesh Nar who gave me help and guide me all the time Thanks Andres Garcia who work together with me and made the system more perfect Thanks Bing Yang for his support Sponsor Thanks SRC Semiconductor Research Corporation sponsored our search SRC Grant Task 2071 026 Thermally Stimulated Current Evaluation of Molding Compounds Used in High Voltage Applications Thanks Denison Marie and Nguyen Luu from Texas Instrument Company Thanks for their patient guide and support 1
59. ructural defects and impurity centers and build up of charges near heterogeneities such as the amorphous crystalline interfaces in semi crystalline polymers and the grain boundaries in polycrystalline materials 2 To study the charge decay and contribution of electrets under constant heating rate TSDC technique was introduced The decay processes are thus investigated as a function of temperature instead of time 3 At room temperature charge decay measurements are rather time consuming because at such low temperatures the dipoles and charges remain virtually immobile However when the environment around the electret becomes mobile the dipoles and charges quickly regain their freedom of motion 4 Thermal stimulation of the discharge therefore shortens the measurement considerably During such heat stimulated discharge a metal connection between two electrodes generates a weak current that shows a number of peaks when recorded as a function of temperature The shape and location of these peaks are characteristic of the electrets charges storage mechanisms Analysis of the peaks yields detailed information on the permanent dipoles density relaxation time activation energy and trapping parameters energies concentration and capture cross section of traps To further isolate individual relaxations related to the macroscopic relaxation Lacabanne and Chatain proposed a modified TSDC method termed thermal sampling or window polarization
60. ry to provide a visual means of analyzing the process 22 Compare the actual process response to the PID response figures with a step change to the process Make changes to the PID parameters in no more than 20 increments from the starting value and allow the process sufficient time to stabilize before evaluating the effects of the new parameter settings Figure 2 5 presents one typical temperature PID control strategy in function of time Figure 2 6 indicates the possibility and method of adjusting controller s response rate 10 P amp I Figure 2 5 Typical response curve INPUT INPUT LA SP 7 SP AZ P UU L TIME TIME To quicken response e Decrease proportional band Decrease integral time To dampen response Increase or defeat setpoint Increase proportional band Increase integral time ramping Extend output power limits Use setpoint ramping Use output power limits Re invoke auto tune with a lower damping code Re invoke auto tune with a higher dampening code Decrease derivative time Increase derivative time Check cycle time Figure 2 6 Process response extremes 11 CHAPTER 3 TSDC SYSTEM INSTRUMENTATION DESIGN 3 1 Overview of the Whole System This TSDC system is composed of TSDC cell main chamber heating unit cooling unit electrical unit vacuum unit and data acquisition unit The heating and cooling units provide a wide
61. s management lines and handshake lines The data lines handle bus data and commands while the management and handshake lines ensure that proper data transfer and operation takes place Each bus line is active low with approximately zero volts representing logic true The compact NI GPIB USB HS transforms any computer with a USB port into a full function plug and play IEEE 488 2 controller for up to 14 programmable GPIB instruments The GPIB USB HS takes advantage of Hi Speed USB to provide superior performance of up to 1 8 MB s with the standard IEEE 488 handshake and 7 7 MB s with the high speed IEEE 488 handshake HS488 3 7 4 Labview LabVIEW short for Laboratory Virtual Instrument Engineering Workbench is a system design platform and development environment for a visual programming language from National Instruments 32 Labview helps engineers scale from design to test and from small to large systems The roles of Labview in TSDC system contains gt Collect and record current and temperature data gt Plot current vs temperature TSDC curve Send order to sub component of system such as turning on off cooling system communicating with temperature controller 36 Figure 3 20 shows the interface of labview used for TSDC system and figure 3 21 is the program to achieve each function for TSDC system which includes Keithley 6517 pico ammeter sub VI and PT104A temperature data logger sub VI
62. sample can be cool down to 150 C in two minutes Figure 3 10 Overview of heating unit of TSDC system 23 3 6 Electrical Unit Voltage Supply amp Current Measurement Unit Model 6517B Electrometer High Resistance Meter from Keithley Company was selected to be used for TSDC system s electrical unit as shown in figure 3 11 Figure 3 11 Overview of electrical unit of TSDC system 3 6 1 Capabilities and Features Overview The Model 6517B is a 6 digit electrometer high resistance test and measurement system with the following measurement capabilities 24 gt gt gt DC voltage measurements from I y V to 210V DC current measurements from 10aA to 21mA Charge measurements from 10fC to 2 1 u C Resistance measurements from 102 to 210P2 Surface resistivity measurements Volume resistivity measurements External temperature measurements from 25 C to 150 C using the supplied Model 6517 TP thermocouple 24 gt Relative humidity measurements 0 to 100 using the optional Model 6517 RH probe Some additional capabilities of the Model 6517B include gt Built in V Source The 100V range provides up to 100V at 10mA while the 1000V range provides up to 1000V at Ima Keithley 6517B Electrometer Rear Side Interlock to 2Pin Lemo Cable To Sample Temeprature Input of Temp Controller PT 100 Safety Switch Connector Temp Sensor Novocontrol TSDC Sample Cell Figure 3 12 Co
63. ss modulus E and Tangent lag angle Tan 5 were measured with frequency scan and temperature scan tests Figure 6 12 6 13 and 6 14 show the temperature scan data for epoxy sample and silica filler sample Master curve of DMA test is shown in figure 6 15 Activation energy was determined through master curve 64 Figure 6 12 DMA 3 point bending test E Figure 6 13 DMA 3 point bending test E Pure Epoxy De Tan Delta Epoxy Ceramic 10 weight Figure 6 14 DMA tan delta Table 6 2 DMA Test Temperature Scan Data Analysis E E max MPa E min MPa E max E min MPa Pure Epoxy 1170 17 6 1152 4 E Tg C E Peak Value Transition area Transition Width 50 gt 100 Epoxy Ceramic Tan Delta 65 Sample Tg C Tan 6 Peak Transition area Transition Width 50 gt 100 Pure Epoxy Epoxy Ceramic 10 weight 1 0E 00 1 0E 02 Frequency rad s Figure 6 15 Master curve of DMA test Pure Epoxy Ea 281 39 kJ mol Epoxy Ceramic 10 weight Ea 352 63 kJ mol 2 6 2 4 2 2 1 T 1000 K 1 Figure 6 16 Shift factor of master curve 66 6 3 Differential Scanning Calorimetry Differential Scanning Calorimetry is athermal analytical technique in which the difference in the amount of heat required to increase the temperature of a sample and reference is measured as a function of temperature Both the sample and reference are maintai
64. st of Main Chabelo 15 Table 4 1 Specification of 1556 US Epoxy Resin essen enne enne nnne 40 Table 4 2 Specification of Msds Aradur 2964 US Agent essere 40 Table 4 3 TSDC Experiment Parameter for Epoxy and Composite Samples 45 Table 5 1 Curve Coordinate Area Comparison between TSDC and TSPC 51 Table 6 1 DEA Test Temperature Scan Data Analysis eee 61 Table 6 2 DMA Test Temperature Scan Data Analysis ooooonnoocccnoncccnonccononcnononcnonanccnnnnccnnnncnnns 65 vii LIST OF FIGURES Page Figure 2 1 The principal set up of a typical TSDC experiment esee 6 Figure 2 2 Proportional band feature of CN63100 controller eene 8 Figure 2 5 Integra time a tt 9 Figure 24 Derivative ie AA Ele lca di dice dra ee BAG Ad 10 Fig re 2 5 Typical Te SONS CCU Eee 11 Figure 2 0 Process response extremes e CO Oe 11 Figure 3 1 Overview of whole TSDC system coin ta 12 Fip re 3 2 7 ES DC cell oo end A A Ga NG Ta Ba A Sene 14 Figure 3 3 3D design of main chamber and real picture esee 16 Figure 3 4 Dimensi n of main chamber 2 seite e One iictoiqu ies 16 Figure 3 5 Overview of heating Ut tesi ii 18 Figure 3 6 OMEGA AHP series gas Heater o e tenes ii tild 18 Figure 3 7 OMEGA CN63100 temperature controller eene 20 Figure 3 8 OMEGA
65. tion of the proportional band to eliminate error in the steady state The units of integral time are seconds per repeat 22 One of the typical integral time diagram is shown in figure 2 3 Integral action also known as automatic reset changes the output power to bring the process to setpoint Integral times that are too fast small times do not allow the process to respond to the new output value This causes over compensation and leads to an unstable process with excessive overshoot Integral times that are too slow large times cause a slow response to steady state errors Integral action may be disabled by setting the time to zero If time is set to zero the previous integral output power value is maintained If integral action is disabled manual reset is available by modifying the output power offset OPOF initially set to zero to eliminate steady state errors This parameter appears in unprotected parameter mode when integral time is set to zero The controller has the feature to prevent integral action when operating outside the proportional band This prevents reset wind 29 up DEVIATION TIME OUTPUT INTEGRAL OUTPUT POWER PROPORTIONAL OUTPUT TIME NOTE TOTAL OUTPUT POWER IS THE SUM OF THE THREE PID SETTINGS INTEGRAL TIME Figure 2 3 Integral time 2 3 3 Derivative Time Derivative time is defined as the time in seconds in which the output due to proportional action alon
66. y between two electrodes as it can deform the sample and may damage the electrodes 4 1 1 Sample Material Pure epoxy and agent from Huntsman Company were used for TSDC investigation To investigate silica filler s effect for epoxy on TSDC properties we add 10 weight present silica to epoxy sample to contrast with pure epoxy data We chose MSDS ARALDITE LY 1556 US type epoxy from Huntsman Company table 4 1 and 4 2 show the basic physical and chemical properties of MSDS ARALDITE LY 1556 US 39 epoxy resin and MSDS ARADUR 2964 US agent respectively 33 34 Silica type Cloisite 15A From Southern Clay Products Inc was selected to be epoxy s filler Table 4 1 Specification of 1556 US Epoxy Resin Chemical Name Cycloaliphatic Epoxy Resin Chemical Formula C1404H20 Molecular Weight 252 Appearance Liguid Color PtCo 0 50 Acidity wt 0 0 1 Water wt 0 0 05 Viscosity 25 C cps 350 450 Specific Gravity 25 C 1 167 1 182 Epoxide eq wt g eq 131 143 Table 4 2 Specification of MSDS ARADUR 2964 US Agent Methyl endomethylene FREIE NANG Tetrahydrophthalic Anhydride Chemical Formula C10H1003 Molecular Weight 178 2 Appearance Clear Liquid Viscosity 25 C 1 5048 230 0 cps Density 25 C 1 239 g ml Acid Content 1 0 Max Purity 98 0 Min Vapor Pressure 120 C 1 7 mmHg 40 4 1 2 Sample Curing Mix epoxy and

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