PLAY thickness, and the bond-wire diameter D.
Figure 1: Power cycling sample types: PrimePACK modules with baseplate and the corresponding metallographic cross-section
Figure 3: Power cycling results of PrimePACK samples employing. XT sorted Equally important for the module ´ s lifetime are novel die-attach by a) T jmax and b) t on. technologies such as sintering using silver particles. Improved mechanical properties, with respect to soft solders, are also obtained for sintered Ag die attach layers. This is predominantly a result of the high melting point and the higher mechanical strength of the material.
To enhance the power terminals ´ connections as well, ultrasonic welding( US) is implemented. The joint between DCB and BP is upgraded utilizing an advanced solder technology. However, compared to the other interconnect materials, a higher plastic deformation during temperature cycling and creeping fatigue cannot be excluded for the substrate-to-baseplate solder.
Figure 2: Failure mechanisms during power cycling( 3, 4): Cracks are marked by red arrows. Samples with baseplate show degradation within the substrate-to-baseplate solder Figure 4: SAM pictures of the baseplate to DCB solder interconnect after
power cycling. Red arrows mark degradation: The failure mechanisms in power modules employing improved a) After 150.000 active cycles @ ΔT≈108 ° C and ton = 2 s.
wire bond technologies, sintering as die attach and the improved b) After 125.000 active cycles @ ΔT≈120 ° C and ton = 5 s. solder between substrate and baseplate were investigated in c) After 66.000 active cycles @ ΔT≈140 ° C and ton = 60 s. detail, they are displayed in figure 2. The degradation of the d) After 3000 passive thermo-shock cycles from-40 ° C to 150 ° C substrate-to-baseplate solder has been identified as the most prominent failure mode which is effecting lifetime.
For the development of a first lifetime model focusing on the new
Lifetime Analysis die attach technologies, the power cycling results presented were Current lifetime models for power modules employing standard revised. Most importantly, failure data from samples with
technologies underline the impact of the temperature difference different die attach technologies were grouped together. This is a ΔT, the mean or maximum junction temperatures T vjm, T vjmax and valid approach since the failure is always related to the substratethe duration of the load current t on during one cycle on the to-baseplate solder. estimated lifetime of a power module. Even though these models Figure 3 presents the excellent power cycling results of are empirical, ΔT, T jm and t on can be related to driving forces of PrimePACK modules employing. XT with regard to T vjmax and ton. degradation. The first lifetime model presented was later
For comparison, the results of standard technology are added to extended by adding terms that describe the impact of t on, the the graph.
current per bond-foot, the voltage class U, with respect to chip
The examination of the copper wire bond connection out of this
ELE Times | 34 | March, 2017