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
Chart1
Aluminum (Al)
SAC305
Copper (Cu)
Aluminum Silicon Carbide (AlSiC)
Aluminum Oxide (Al₂O₃)
Aluminum Nitride (AlN)
Silicon Nitride (Si₃N₄)
Temperature (degC)
Coefficient of thermal expansion (ppmdegC)
219
216
158
684
82
45
28
221
216
16
704
82
45
28
223
216
163
724
82
45
28
225
216
165
744
82
45
28
227
216
167
764
82
45
28
229
216
169
784
82
45
28
231
216
171
804
82
45
28
233
216
173
824
82
45
28
235
216
175
844
82
45
28
237
216
177
864
82
45
28
239
216
178
884
82
45
28
241
216
18
904
82
45
28
243
216
182
924
82
45
28
MasterStudy
MasterStudy
Si3N4
AlN
Al2O3
Strain Energy DensityCycle (MPa)
BaseplateMatampThkVariation
BaseplateMatampThkVariation
Al
Copper
AlSiC
Baseplate Thickness (mm)
Strain Energy DensityCycle (MPa)
SubstrateMatampThkVariation
30 C
130 C
HighDwellCu
RampDownCu
LowDwellCu
RampUpCu
Strain (XZ)
Stress XZ (MPa)
Cu Baseplate
SubMetThkVariation
HighDwellCu
RampDownCu
LowDwellCu
RampUpCu
Strain (XZ)
Stress XZ (MPa)
AlSiC Baseplate
BaseplateFootPrintVariation
BaseplateFootPrintVariation
Si3N4
AlN
Al2O3
Substrate Ceramic Thickness (mm)
Strain Energy DensityCycle (MPa)
CTEProperties
CTEProperties
Si3N4
AlN
Al2O3
Substrate Metallization Thickness (mm)
Strain Energy DensityCycle (MPa)
Baseplate Length (mm)
Strain Energy DensityCycle (MPa)
Aluminum (Al)
SAC305
Copper (Cu)
Aluminum Silicon Carbide (AlSiC)
Aluminum Oxide (Al₂O₃)
Aluminum Nitride (AlN)
Silicon Nitride (Si₃N₄)
Temperature (degC)
Coefficient of thermal expansion (ppmdegC)
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
MatProperties
Chart1
Si₃N₄
AlN
Al₂O₃
Strain Energy DensityCycle (MPa)
1944981
1541321
0939798
0179141
0161197
0208441
392511
341359
2584948
MasterStudy
MasterStudy
Si₃N₄
AlN
Al₂O₃
Strain Energy DensityCycle (MPa)
BaseplateMatampThkVariation
BaseplateMatampThkVariation
Al
Copper
AlSiC
Baseplate Thickness (mm)
Strain Energy DensityCycle (MPa)
SubThkVariation_Cu
30 C
HighDwellCu
RampDownCu
LowDwellCu
RampUpCu
Strain (Z)
Stress Z (MPa)
Cu Baseplate
SubThkVariation_AlSiC
HighDwellCu
RampDownCu
LowDwellCu
RampUpCu
Strain (XZ)
Stress XZ (MPa)
AlSiC Baseplate
SubMetThkVariation_Cu
SubMetThkVariation_Cu
Si₃N₄
AlN
Al₂O₃
Substrate Ceramic Thickness (mm)
Strain Energy DensityCycle (MPa)
SubMetThkVariation_AlSiC
SubMetThkVariation_AlSiC
Si₃N₄
AlN
Al₂O₃
Substrate Ceramic Thickness (mm)
Strain Energy DensityCycle (MPa)
BaseplateFootPrintVariation
BaseplateFootPrintVariation
Si3N4
AlN
Al2O3
Substrate Metallization Thickness (mm)
Strain Energy DensityCycle (MPa)
CTEProperties
CTEProperties
Si3N4
AlN
Al2O3
Substrate Metallization Thickness (mm)
Strain Energy DensityCycle (MPa)
Sheet1
Sheet1
Al
Cu
AlSiC
Baseplate Length (mm)
Strain Energy DensityCycle (MPa)