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Parametric Design Study of a Power Electronics Package
Paul ParetNational Renewable Energy Laboratory ColoradoIEEE ITherm ConferenceJuly 21-23 2020
This presentation does not contain any proprietary confidential or otherwise restricted information
NREL | 2
Background
Device
Metalized SubstrateSubstrate Attach
Base Plate
Die Attach
InterconnectEncapsulant
Enclosure
Terminal
Traditional Power Electronics Package
Maximum operating temperature ndash 150 deg C
Cree Wide Bandgap Device Package
Metalized Substrate
Sintered-Silver
Base Plate
Crack Propagation in Pressure-Assisted Sintered Silver
Photo Credit Gilbert Moreno
Photo Credit Paul Paret
NREL | 3
Objective
bull Investigate the impact of power electronics packaging materials and geometric design on the substrate attachndash Large-area attachndash Prone to thermal cycling
bull Typical substrate attach materials arendash Solders such as 63Sn37Pb SAC305 95Pb5Snndash Sintered silverndash Transient liquid phase alloys
bull Automotive power electronics package designndash Reduce cost weight and volumendash Improve thermal performance and reliability
NREL | 4
Modeling Setup
Material Properties
Experimental SampleBaseplate (Cu AlSiC Al)
Ceramic (Si3N4 Al2O3 AlN)
Metallization (Cu)
254 mm
254 mm
Solder layer (not visible) is between the backside Cu metallization (not visible) and the baseplate
bull Quarter-symmetry model (yellow dashed lines in top-left figure) used in simulations
bull Anand viscoplasticity constitutive model used to simulate deformation of the solder region
bull Thermal cycling profile bull -40degC to 150degCbull 5degCmin ramp ratebull 10 min dwell at extreme temperatures
NREL | 5
Strain Energy Density
Strain Energy Density Contour Plot
bull Strain energy densitycycle (volume-averaged at the corner region) was selected as the metric for comparison
NREL | 6
Impact of Baseplate amp Ceramic Material
00
05
10
15
20
25
30
35
40
45
Copper AlSiC Al
Stra
in En
ergy
Den
sity
Cycl
e (M
Pa) Si ₃N₄ AlN Al₂O₃
Thickness of baseplate ndash 5 mm ceramic ndash 032 mm metallization ndash 02 mm
C-SAM Images of SAC305 solder with AlSiC (top) and Cu (bottom) baseplates Images on the left and right were taken at 0 cycles and 500 cycles respectively
bull AlSiC baseplate offers superior reliability than its Cu or Al counterparts mainly due to the low coefficient of thermal expansion mismatch with the ceramic material