30 May, High Performance Packaging of Power Electronics: Role of Thermally Engineered Materials. M.C. Shaw

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1 High Performance Packaging of Power Electronics: Role of Thermally Engineered Materials M.C. Shaw Rockwell Science Center, Thousand Oaks, CA 30 May, 2001

2 REPORT DOCUMENTATION PAGE Form Approved OMB No Public reporting burder for this collection of information is estibated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burder to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports ( ), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YYYY) 2. REPORT TYPE Workshop Presentations 4. TITLE AND SUBTITLE High Performance Packaging of Power Electronics: Role of Thermally Engineered Materials Unclassified 6. AUTHOR(S) Shaw, M. C. ; 7. PERFORMING ORGANIZATION NAME AND ADDRESS Rockwell Science Center xxxxx Thousand Oaks, CAxxxxx 9. SPONSORING/MONITORING AGENCY NAME AND ADDRESS Office of Naval Research International Field Office Office of Naval Research Washington, DCxxxxx 3. DATES COVERED (FROM - TO) to a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 8. PERFORMING ORGANIZATION REPORT NUMBER 10. SPONSOR/MONITOR'S ACRONYM(S) 11. SPONSOR/MONITOR'S REPORT NUMBER(S) 12. DISTRIBUTION/AVAILABILITY STATEMENT APUBLIC RELEASE, 13. SUPPLEMENTARY NOTES See Also ADM001348, Thermal Materials Workshop 2001, held in Cambridge, UK on May 30-June 1, Additional papers can be downloaded from: ABSTRACT? Advantages of new approaches must be demonstrated at the system, e.g., motor drive, level. Device Power Density (A/cm2 or W/cm2 ) System Power Density (W/m3) Lifetime Assurance of Entire System System Cost Analysis Ultimately Required 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT Public Release a. REPORT Unclassified b. ABSTRACT Unclassified c. THIS PAGE Unclassified 18. NUMBER OF PAGES NAME OF RESPONSIBLE PERSON Fenster, Lynn lfenster@dtic.mil 19b. TELEPHONE NUMBER International Area Code Area Code Telephone Number DSN Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39.18

3 Global Energy Consumption and Power Electronics (Source: NSF Center for Power Electronic Systems: Global Energy Consumption (Terawatts) Total Energy Electrical Energy % savings with improved power electronics Year US Electrical Energy Consumption 55% Motor Computers 4% 25% Other 21% Lighting * Output of 840 power plants * EPRI 2

4 Defense Power Electronics Requirements Example: PEBBs ITHERM Rel--3 Courtesy of G. Campisi, Office of Naval Research INTEGRA TED OPERA TIONS CENTER Fault T olerant Solid State Electric Distribution System Electric Driven Accessories, Environmental Control System, Engine Accessories POWER CONTROL MODULE PM MO TOR Electric Anti-Ice Electric Actuated Brak es I E Generator Solid State Power Controllers P OA ZONAL ELECTRICAL DISTRIBUTION SYSTEM Ship Service Converter Module (SSCM) Ship Service Inverter Module (SSIM) Ship Service Converter Module (SSCM) SOURCE Power P ort POWER ELECTRONIC BUILDING BLOCK PEBB LO AD Power P ort Solid State Remote Terminals Auxiliary Power Unit Generator Electric Driven Flight Actuators POWER GENERA TION MODULE POWER DISTRIBUTION MODULES SYSTEM CONTROL Control FUEL CELL Auxiliary System Bi- Directional Inverter Energy Storage Controller for Electric Motor A uxilliary Load Distribution and Control Au o Power Source Alternator Bi- Directional Inverter Bi- Directional Inverter Motor Transmission Energy Management and Control

5 Power Electronic Systems Motor Drives Today s Topic Radar / Microwave Communications dc to dc Converters Power Supplies Electric Vehicle Drives Weapons Systems 4

6 Drive & Motor Automation System Rockwell Automation - Allen Bradley 1336 Force Drive Performance Metrics: Power Density Cost Reliability Converts AC power (fixed frequency, voltage) to AC Power (variable frequency, current, and voltage) Enables exact control of speed (RPM) and torque of motors Motors become controlled electromechanical energy converters. Rockwell Automation Reliance Electric AC Motor 5

7 Basic Power Packaging Elements Plastic Housing Gel Encapsulation Silicon Power Terminals Wirebonded Interconnections Soldered Interconnections Ceramic Insulation Metal Baseplate Heatsink 6

8 Generic Electronic Packaging Technology Hurdles Controlled Power Density ( W / m 3 ) High Power Requirements from Devices High Packaging Densities Weight Requirements Cost ( $ / Function ) Reliability ( MTBF ) 7

9 High-Temperature Packaging of SiC Electronics M.C. Shaw, J.R. Waldrop, F. Zok, 1 Rockwell Science Center, Thousand Oaks, CA 1 University of California, Santa Barbara CA CMC 30 May, 2001 Contract Number MDA97298C0002

10 Decrease in System Volume Through Utilization Of Silicon Carbide (SiC) Electronics T fin = 55C Baseplate Power Density ~ 10 5 W/m 2 Baseplate Power Density ~ 10 5 W/m 2 Silicon Power Density = 10 6 W/m 2 T fin >200C SiC Power Density = 10 6 W/m 2 Silicon Tj ~ C Heatsink Power Density ~ 10 3 W/m 2 Smaller, hotter heatsink feasible with SiC (Q=hA T) Silicon Carbide Tj ~ C Heatsink Power Density ~ 10 4 W/m 2 9

11 Thermomechatronics M.C. Shaw and E.R. Brown, 1 Rockwell Science Center, Thousand Oaks, CA 1 University of California, Los Angeles CA 30 May, 2001 Contract Number MDA97298C0002

12 Thermal Management of Power Electronics: Spread Power Density from Device to Heatsink Baseplate Power Density ~ 10 5 W/m 2 Silicon Power Density = 10 6 W/m 2 Heatsink Power Density ~ 10 3 W/m 2 5 hp Motor Drive Example 11

13 Large Area Solder Joint Reliability in Power Assemblies IGBT Cu Examples of Buried Continuous Solder Layers 1 cm Internal view of a 1200A, 3300V IGBT module (courtesy: Eupec GmbH+ Co.) 12

14 Elastic Fracture Mechanics Energy Balance in Layered Systems σ = Stress in coating h = Coating thickness E, v = Elastic properties Z ~ 0.3 σ h Film/Coating Substrate, G Ic ( 2 ) 1 υ 2 Z σ h > E < Driving Force for Crack Growth or G Ic Material or Interfacial Crack Growth Resistance Cracking depends on which is larger: 13

15 Thermal Cycling of Sn - Pb (Elastic/Plastic) vs Au-Sn (Elastic) Joints Au20Sn on Copper α = 14.1 ppm; Elastic Solder Sn-Pb or Au-Sn Solder As Soldered 1 cycle 10 cycles 100 cycles 1000 cycles Cu Si 63Sn37Pb on Copper α = 14.1 ppm, Elastic / Plastic Solder Ultrasonic Reflection Microscopy 14

16 Model of progressive crack growth in DBC/baseplate solder joint 2a 2b b/a ~ 2 2b b/a ~ 1 2b b/a ~ 0.2 = IGBT As Soldered 1 cycle 10 cycles 100 cycles 1000 cycles 15

17 Thermal Equivalent Circuit T C T J device case Heat Current T J Θ JC (large) Θ CS (small) T S heat sink Θ SA (large) T A environment T A Θ JC + Θ CS + Θ SA = Θ JA = (T J T A )/P 0 Thermal Resistance θ JC Analytic Form ~ ρt/a s ρ -> thermal resistivity, t -> thickness Typical Values 1.4 o C/W θ CS ~ ρt/a s ~ o C/W θ SA ~ 1/hA s h -> heat transfer coefficient o C/W (natural convection); 1-10 o C/W (forced air) 16

18 Solder Joint Fatigue Raises Package Thermal Resistance A. Baseplate T j.. T AA = 0 C A Pristine condition - lowest thermal resistance Thermally cycled condition - higher thermal resistance No Heat Flow b/c Fatigue Crack A. Baseplate Device T j. ~ Heat. Fatigue Crack Solder Substrate A T AA = 0 C 17

19 Bipolar Transistor Performance Degradation with Repeated Power Cycling (Ref: Evans and Evans) (Evans and Evans, IEEE Trans. Comp. Pack., Mfg. Tech., Part A, v. 21 no. 3 pp , 1998) Forward Voltage, V be Number of Power Cycles Experimental Results Showing Large Increase in Forward Voltage Drop, V be, with Repeated Power Cycling, N 18

20 Coupled Electro-Thermal Simulation Electrical Equivalent Circuit T J Modeling Features: Nonlinear thermal circuit models Connect electrical to thermal circuits through unique thermal node (after A. Hefner of NIST) Θ JC SPICE-like environment thermal node T C T S Θ CS Thermal Equivalent Circuit of Device to Ambient T A Θ SA 19

21 Schematic of Model Package Geometry Heatsource; Radius = a Power = P Substrate; Radius = b o w Baseplate Solder joint 20

22 Calculated Thermal Resistance, R th, vs. Inverse Normalized Fatigue Crack Length, b/a. Note the rapid increase in R th with penetration of the fatigue crack into the region below the device (b/a~1) 100 Thermal Resistance, b b/a ~ 0.2 Thin Substrate, a/w = 5 Thick Substrate, a/w=125 b/a ~ 2 2a 2b b/a (Inverse Normalized Fatigue Crack Length) 21

23 Dependence of Junction Temperature Increase, T j, on Inverse Normalized Fatigue Crack Length, b/a 200 2a Increase in Junction Temperature, b b/a ~ 0.2 2b b/a ~ 2 a/w = 1.25; P=500W a/w = 5; P=500W Two different power levels and substrate thicknesses. a/w = 1.25; P=100W a/w = 5; P=100W b/a (Inverse Normalized Fatigue Crack Length) 22

24 Strain Energy Release Rate, G Ic, Depends on T j Stress, σ ( α Τ) w Substrate Z σ 2 h E ( 2 ) 1 υ = G Ic Fatigue Crack Baseplate Strain energy release rate is the driving force for fatigue crack growth 23

25 Applied Strain Energy Release Rate, G, at Fixed Device Power Dissipation vs. b/a. 10,000 Applied Strain Energy Release Rate, 1, a/w = 1.25; P= 500W a/w = 1.25; P= 100W a/w = 5; P= 500W a/w = 5; P= 500W b/a (Inverse Normalized Fatigue Crack Length) 24

26 Experimental crack growth rate data, da/dn, vs. cyclic strain energy release rate range G for the Al-Al 2 O 3 and Al-Al systems. 25

27 Relationship between the number of power cycles, N, and the crack length, l for two different power levels and substrate thicknesses a/w = 5; P = a/w = 5; P = 500 a/w = 1.25; P = 100 Note the highly nonlinear relationship between the crack lengths and number of power cycles a/w = 1.25; P = Crack length (mm) 26

28 Predicted Junction Temperature Increase, T j, vs. Power Cycles, N Heatsource; Radius = a Power = P Substrate; Radius = b o 100 a/w=1.25, P=500 Baseplate Solder joint 50 a/w=1.25, P=100 a/w=5, P= Nu mb er o f Cycles, N a/w=5, P=100 27

29 Thermomechatronic Analysis of coupled flow of electrical, thermal and mechanical energy Load Electronic Device Electro-mechanical modulation X Bias Supply Energy Form Electrical Thermal Mechanical Thermo-mechanical modulation X Package Environment Thermo-mechanical feedback loop(s) Mechanical Thermal stressstrain 28

30 Conclusions Advantages of new approaches must be demonstrated at the system, e.g., motor drive, level. Device Power Density (A/cm 2 or W/cm 2 ) System Power Density (W/m 3 ) Lifetime Assurance of Entire System System Cost Analysis Ultimately Required Research Needs: 1) Materials - Controllable and High Thermal Conductivity - Functional Integration of Electrical, Thermal, Mechanical Features - High Temperature Capability - Lightweight - Compatible with Solid-State Devices - Easily Processed 2) Efficient, System-Based Design Methodologies - Mechanical, Thermal, Coupling - Lifetime Prediction / Reliability - Design Optimization / Tradeoff Capability 29