Specifications

13
Dec. 20
Mitsubishi IPM-series Application Note
7-2-3-2. Power Cycle Failure Mechanism
Fig.7.4 shows the typical construction of power module. When junction temperature of power module is changed, stress strain
between aluminum wire and silicon chip, and between silicon chip and insulation substrate occurs due to the difference of
coefficient of linear expansion. If this stress is supplied repetitively, thermal fatigue for the junction becomes failure.
For inverter use, power cycle life is a necessary concern, which should be given during designing system. An example is given in
Fig.7.5. The failure mode is that the crack of bonding surface makes progress by stress due to the difference of linear expansion
between aluminum wire and silicone chip and finally lead to the peel failure mode.
A power cycle testing result of Mitsubishi Electric's module is shown in Fig.7.6.
Fig.7.4 Module Structure
Fig.7.5 Bonding Surface Fatigue Caused by Power Cycle Testing
100000k
10000k
1000k
100k
10k
1k
Cycle
1 10 100
1000
Ǎ
Tj[°C]
Fig.7.6 Power Cycle Curve
Solde
r
Solde
r
Silicon Chi
p
Bonding
Wire
Base Plate
Insulation Base
p
late with Co
pp
er Foil
Reliability