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Power Electronics Packaging Solutions for Device Junction

Temperature over 220oC

EPRC – 12 Project Proposal

15th August 2012

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Motivation

Electronic Vehicle

Source: Toyota

Source: Yole

Source: Infineon

Renewable energy

Aerospace

Hybrid Vehicle

Source: Nissan

Electronic Railway

• Increased requirements of high power semiconductor device module for future automotive, aerospace and green & renewable energy industry

• Emerging wide band gap power devices : SiC and GaN can be operated >220oC

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Technology Trends• Technology trends for high power module and discrete :

High temperature endurable materials >220oC (silver sintering, encapsulations) High reliable and low stress interconnections (foil interconnects, ultrasonic bonding) Thermal cooling solution (Dual-side cooling / micro-channel cooling )

Source: Yole

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Challenges to be Addressed

Power Module

Base plate

PassiveDBC substrate

Encapsulation Materials Plastic case• Thermal endurance >220C• Void free processing• Lower stress (CTE, Modulus) • High power insulation• Moisture barrier • Delamination free

• Thermal endurance >220C• Void free processing• Lower stress (CTE, Modulus) • Electrical conductive• Die backside metallization

Power Device Attach

IGBTDiode

Encapsulations

Power Source Interconnection • Power cycling endurance• Temp cycle endurance • Process optimization• inter-metallic diffusion• Thermal & Electrical properties

Substrate (DBC) • Temp cycling endurance• Adhesion with Encapsulation• Adhesion between Cu/Ceramic• Surface finish • Thermal & Electrical properties

Passive component attach• Thermal endurance >220C• Void free processing• Temp cycle endurance • Electrical conductive• Metallization > 220C

IGBT

Power Discrete

Heat spreader

Wire

WireThermal interface materials• Thermal endurance > 220C • Temp cycle endurance • Delamination & fracture • Thermal conductivity

Base plate (system board)

Reliability testing methodologies• Reliability test spec• Reliability testing method• Failure Analysis / reliability model

Modeling and predictions• Thermal characterization• Mechanical characterization• Electro-thermal-mechanical coupling• Reliability model (power cycling)

Lead frame

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Objective Development and characterization of power semiconductor packages for high junction temperature endurable (>220oC) solutions for next generation devices, including the following:

Material solutions for TV1 and TV2 High temperature endurable die attach (Ag sintering, TLP bonding, Cu-Cu bonding) DBC surface finish option (Ni/Au finish, ENIG ) High temperature endurable encapsulation materials (High Tg EMC) Cu based interconnection through EMWLP RDL processThermal management solutions for TV1 and TV2 Dual side cooling structure package development and packaging process optimization High temperature endurable, high conductive TIM materials ( Ag sintering )Package characterization and Reliability for TV1 and TV2 Mechanical &Thermal modeling and characterization Power cycling modeling : electro-thermal- mechanical coupled analysis Reliability and failure analysis

Project Proposal

Conventional Power Module

Base plate

PassiveDBC substrate

Plastic case

IGBTDiode

Encapsulations Wire

IGBT

Wire

Base plate (system board)

Lead frame

Conventional Power discrete *

Heat spreader

Heat spreader

Diode IGBT

TV1* : Novel Dual side cooling Power Module

Top RDL layer

Heat spreader IGBT

TV2* : Novel Dual side cooling Power Discrete

Heat spreader

Heat spreader

* To be finalized with members input

* Conventional test vehicle with new material option can be considered as project test vehicle on the basis of members assembly support

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Structural modeling and interconnection life prediction for novel dual side cooling power module Power source/gate/drain RDL design

optimization for stress minimization Interconnection fatigue life prediction (plastic

constitutive model for Cu RDL) Packaging material properties effect on the

investigation Electro-thermo-mechanical coupled power

cycling impact modeling Ref. Hua Lua et al. “Lifetime Prediction for Power Electronics Module Substrate Mount-down Solder Interconnect” Proceedings of HDP’07

Thermal modeling and characterization Thermal resistance modeling for selected

material set and design Experimental Thermal resistance

Rthjc characterization Liquid based active cooling investigation

Ref. Institute of MicroelectronicsDual side cooling effect Tjmax decreased compared with single side cooling

Design Optimization and Reliability Prediction for Power Module/Discrete with Dual Side Cooling

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High Temperature Power Device interconnection development High temperature endurable die attach (drain)

Micro/Nano Ag sintering (pressure less) TLP bonding : Cu-Sn(415oC), Ag-Sn(480oC) Direct Cu-Cu ultrasonic bonding Device backside metallization

Substrate surface finish option (Ni/Au finish, ENIG) Power source and gate interconnect through

Electrolytic Cu Patterning

High Temperature Endurable Compounds Development High glass transition temperature (Tg >200oC) High thermal conductive compounds (~3W/m-K ) Compatible with Wafer level fan-out process Investigation on thermal degradation (< 3%wt) with

continuous exposure to 220oC Low stress, low thermal mismatch

High Temperature Endurable Materials for Power Module with Tjmax> 220oC

TLP bonding (Cu-Sn) used in Infineon XT modules in 2010

Ref. Institute of MicroelectronicsMicro Ag particles sintered by pressure less process

Chin-Lung Chiang et.al “Thermal stability and degradation kinetics of novel organic/inorganic epoxy hybrid…” Thermochimica Acta 453 (2007)

thermal degradation kinetics for epoxy

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Thermal Interface Material investigation High conductive /temperature endurable Metallic TIM (Ag sintering) with high power insulation

layer (Al2O3) Polymeric TIM with conductivity > 4W/m-K Thickness control Thermal performance consistency investigation after

reliability test

High Temperature Endurable Dielectric passivation layer High glass transition temperature (Tg >200oC) BCB, Polyimide photo sensitive PR Compatible with Wafer level fan-out process Investigation on thermal degradation (< 3%wt) with

continuous exposure to 220oC Low stress, low thermal mismatch

High Temperature Endurable Materials for Power Module with Tjmax> 220oC

Source : Danfoss

Source : Danfoss

Ag sintering for TIM

TIM layer crack propagation

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Dual side Cooling Power Module Assembly Process development Cu clip (Ag plated) attachment / alignment Evaluation of molding material Liquid, Granular Process condition (Temperature, time, pressure) Module shift analysis & control Die/ module pick & place tolerance Minimum clearance between die Warpage control Heat spreader attach and TIM process

Reliability Assessments for High Power Application Temperature cycling (Test condition : TBD*1) High Temperature Storage ( 220oC/ 1000 hrs ) HAST (non-biased) Power Cycling test (optional*2) Failure analysis

Dual Side Cooling Power Module Process Optimization and Reliability Assessment

IME’s Novel Dual side Cooling Power Module Assembly Process

*1 To be finalized with members input*2 Need member’s support on actual SiC wafer and testing

Power cycling : IGBT with 300W,10Hz

Tilo Poller et al. “Influence of thermal cross-couplings on power cycling lifetime of IGBT power modules” CIPS 2102

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Thermal and Structural optimization and life prediction for novel dual side cooling power module Interconnection fatigue life prediction (plastic constitutive model for Cu RDL) Packaging material properties effect on the test vehicle Thermal modeling characterization for selected material set and test vehicles Electro-thermo-mechanical coupled power cycling impact analysis

Tjmax >220oC : High Temperature Endurable Power Device Packaging material Solutions (interconnect/encapsulation/TIM) High temperature endurable die attach material characterization using Micro/Nano

Ag sintering, TLP bonding, Direct Cu-Cu ultrasonic bonding Power source and gate interconnect through Electrolytic Cu Patterning Wafer level Fan-out compatible compounds characterization TIM process optimization for dual side application

Dual side Cooling Power Module Assembly Process development Copper clip (Ag plated) attachment / alignment Mold Process condition optimization (Temperature, time, pressure) Heat spreader attach and TIM process

Reliability Assessments & F/A for Novel High Power Module Temperature cycling High Temperature Storage / Low Temperature Storage HAST (non-biased) Power Cycling test (optional) Failure analysis

Possible Research Outcome*

* To be finalized

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Project FlowFinalize Project scope and test vehicles

specifications

Mechanical Modeling & Simulation Analysis on stress and

reliability

Initial Material evaluation and quick reliability test

Thermal performance testingDual side cooling effect analysis

with active cooling

Reliability testing

Failure analysis and report writing

Identify high thermal endurable materials and evaluation

(Members to provide inputs)

Thermal Modeling & Simulation Analysis

Test methodologies (Thermal and Reliability )

Members Inputs

EWLP process modeling –

flow/Warpage

TV1,2 Dual cooling effectPower cycling modeling

Electro-Thermo-mechanical

Power module EWLP Assembly process optimization. Device chip*

(fabrication/purchase)

TV1 Thermal performance sample matrixTV2 Thermal performance sample matrix

TV2 Reliability test sample matrix TV1 Reliability test sample matrix

Scope PlanningMaterial investigation

Process and assembly

Modeling & characterization

Final reliability

Project Time line andschedule : Nov 2012 to June 2014

Note: *Electric testing will be carried out based on device chip availability

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