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