Thermal Interface Material Performance Measurement

Thermal Interface Material Performance Measurement Long Win Science & Technology Co., Ltd. www.longwin.com longwin@longwin.com 886-3-4643221 886-3-4986875 2007/07/16

Contents 1. Introduction Heat Transfer 2. Thermal Conductivity Measurement 3. Contact Resistance 4. Thermal Resistance (Impedance) Measurement

LED Thermal Flow Path R Ja = TJ- T P a

Heat Transfer Mechanism A. Conduction & Q conduction = ka T X B. Convection & Q convection = ha( Ts Ta) C. Radiation & Q radiation = εσa( Ts 4 Ta 4 ) = ha( Ts Ta)

h (Heat Transfer Coefficient) Radiation Type Nature convection Force convection Liquid force convection Evaporate and condense h [w/m 2 * ] 2~25 25~250 50~20,000 2500~100,000 Order 0 1 3 4 0

Thermal Resistance and Ohm s Law Electrical Resistance Thermal Resistance Voltage A Temperature A Current Power Dissipation Voltage B Temperature B R = Voltage A - Voltage B Current θ AB = Temp A - Temp B Power Dissipation Units: Ohm Units: C/Watt

Thermal resistance analysis θ j/bk θ bk/hp1 θ hp1/hp2 θ hp2/fin θ fin/amb 0.65 -------------- TIM, Contact 0.05 -------------- Bounding, Pipe 0.02 -------------- Pipe 0.05 -------------- Bounding, Fin 0.23 ~ 0.53 ---- Fan Tamb Tfin Thp2 Heat Pipe Thp1 Sink TIM Tblock Tjunction

Application Components: A. Cooler B. Pad / Grease C. Power supply D. Interface card E. LED thermal module System: A. D/T PC B. N/B PC C. Servo system D. Rack system E. Projector

Application

Thermal Conduction a. Solid state structure, such as metal heat sink. b. Fluid state structure, such as: (a) heat pipe structure (b) compressor coolant structure c. Liquid state structure, such as water cooling structure.

Fourier Law Q = K A Q:transferred heat T h L K:thermal conduction coefficient of solid state zone of substance A:effective heat transfer area of solid state zone Th:temperature in high-temperature solid state zone Tc:temperature in low-temperature solid state zone L:sampling distance between high and low temperature solid state zones T c Not Easy for DT & Thickness Measurement

Follow ASTM 5470D Standard P FORCE Insulator Guard Heater H T g H Insulator Heater T m H LVDT measure Thickness T1 Upper Meter Bar T2 Specimen T3 Lower Meter Bar T4 T5 Reference Calorimeter T6 Cooling Unit Insulator T A T D ASTM (American Society for Testing and Materials)

Longwin TIM Tester Scheme Cylinder with programmable loading Ball joint (Gimble) to make sure contact surface pressure load uniform Water cooling or air cooling module T i1 or Ta Q out T L3 Thermal isolated material T L2 LVDT measure Thickness Td Tc T L1 Tu Specimen pad/grease or grease Thermal isolated material Q in h Heat Source Tm Tl Q in = I V @ Upper and lower block with alignment fixture

Longwin TIM Tester- 9091IR

Longwin TIM Tester- 9091IR Bond Line Thickness Effect Pressure Effect

Longwin TIM Tester- 9091IR Thermal Cycle Test for Reliability

Contents 1. Introduction Heat Transfer 2. Thermal Conductivity Measurement 3. Contact Resistance 4. Thermal Resistance (Impedance) Measurement

K (Thermal Conductivity)Measurement 1. Laser flash (Transient) 2. Hot disk (Transient) 3. Hot wire (Transient) 4. Heat flux (Steady)

K Measurement Transient Steady state α = k ρ C p m s 2 Q& = k T A X α ρ C p = Thermal diffusivity = Density = Heat capacity m s 2 = m s m = Velocity Length α = 1 C V L

Laser Flash

Hot Disk Thermal Insulation Hot Disk (Transient Plane Source Method, TPS)

Heat Flux ASTM 5470D P FORCE Insulator Guard Heater H T g H Insulator Heater T m H LVDT measure Thickness T1 Upper Meter Bar T2 Specimen T3 Lower Meter Bar T4 T5 Reference Calorimeter T6 T A T D Cooling Unit Insulator

Follow ASTM-5470 D LW 9021D

Longwin TIM Tester- 9091IR

Heat Flux ASTM E1530 Tg COLD FACE HEATER d Tu Heat flow (Q) Tl Th HOT FACE HEATER Copper surface plate Guard heater Test sample Heat flow transducer Copper surface plate At thermal equilibrium : Rs = N (Tl-Tu) / Q R0 Where Rs = sample thermal resistance N = proportionality constant Tl = lower surface temperature Tu = upper surface temperature Q = heat flux transducer output R0 = constant thermal resistance

Bar Material K Measurement cooling T T 1 2 = T T 5 6 = 3T T 2 3 T 6 T T 2 3 = T 34 = T T 4 5 T 5 T 4 thermal Isolate Material T 3 T 2 T 1 Fourier Law q = KA T X Heat Flux Heat Source

Bar Material K Measurement Fourier Law with ASTM-5470 D Thermal Guard concept, For steady state can be got k value.

Table of Thermal Conductivity Diamond 895-2300 Silver 429 Copper 386 Gold 317 Aluminium 237 Brass 120 Platinum 71.6 Iron 80.2 Lead 35.3 Quartz (273K) 6.8-12 Glass 1.35 Wood 0.04 Styrofoam 0.033 Wool 0.04 Silica aerogel 0.017 Air (100 kpa) 0.0262 Water 0.6062 W Ice (273K) 2.2 0 Mercury 8.514 M C (@ 298K)

Contents 1. Introduction Heat Transfer 2. Thermal Conductivity Measurement 3. Contact Resistance 4. Thermal Resistance (Impedance) Measurement

Contact Resistance Thermal Contact Resistance = Func.( roughness, pressure, temperature, material, TIM ) Thermal Contact Resistance = Rc_upper + Rc_lower

Surface Roughness Measurement

Table of Contact Resistance Different Metal Contact Resistance Surface Roughnes s μm Temperature Pressur e MPa Impedance *cm 2 /w SS-Al Polish 20-30 20 10 3.45 SS-Al Polish 20-30 20 20 2.78 SS-Al Polish 1-2 20 10 0.61 SS-Al Polish 1-2 20 20 0.48 Al-Cu Polish 1.3-1.4 20 5 0.24 Al-Cu Polish 1.3-1.4 20 15 0.18 Al-Cu Polish 4.4-4.5 20 10 0.83 Al-Cu Polish 4.4-4.5 20 20~35 0.45 (From Holman, Ref.12, and Kreith and Bohn, Ref.16)

Table of Contact Resistance Same Metal Contact Resistance Surface Roughness μm Temperature Pressure MPa Impedance *cm 2 /w 304 Stainless Steel Polish 1.14 20 4~7 5.26 416 Stainless Steel Polish 2.54 90~200 0.3~2.5 2.63 Aluminium Polish 2.54 150 1.2~2.5 0.88 Copper Polish 3.81 20 1~5 0.18 Copper Polish 1.27 20 1.2~20 0.07 Copper (vacuum) Polish 0.25 30 0.7~7 0.88 (From Holman, Ref.12, and Kreith and Bohn, Ref.16)

Contact Resistance v.s. Pressure

Contact Resistance Measurement

Contents 1. Introduction Heat Transfer 2. Thermal Conductivity Measurement 3. Contact Resistance 4. Thermal Resistance (Impedance) Measurement

Definition of Thermal Resistance T T Q 1 2 I = T1 A Area = A L Q = K A T h L T T R = 1 2 Q T c T2 T T = Q 1 2 R T T I = 1 2 Q A

CPU Cooler Thermal Resistance Ta Fan Cooler Module Tc Tu Air flow rate & flow pattern Q out Meter Bar Q ine = I V Q in Heat Source Tm Tl thermal isolated material Q = R = K A Tc-Ta Q out T h L T c Heat loss

Heat Flux Power 1.Meter Bar Size: a. 31 31 mm b. 37 37 mm c. 25.4 25.4 mm d. User define 2. Power Supply: a. 180W b. 300W

Test Application NB Cooler Module Test DT Cooler Module Test

TIM Thermal Resistance P PAD / Grease water cooling or air cooling T i1 Q outh T L3 thermal isolated material specimen /pad or grease thermal isolated material Q ine = I V Td Tc Q inh Heat Source T L2 T L1 Tu Tm T T T Q R c d = = = = T T T l KA X T c u L1 T l X T + T Q d L1 X 3 1 Tu 2 Tu T L2 heat loss

TIM Test Section-9091IR

LED Thermal Resistance R Ja = TJ- T P a

LED Junction Temperature Measurement

LED Graphite Heat Spreader Copper Base Mount LED Temperature Sensor Graphite Sheet

Thermal Lab Apparatus TIM Research Equipments Liquid state A. Interface material Solid state Phase variation Combined Material LW-9021D LW-9091IR Surface Roughness 3-dimension microscope B. Interface relationship Load Pressure (Load Cell) shape-changing material Non-shape-changing material

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