IGBT Modules - Technologies, Driver and Application (Second Edition) - page 518

Fig. 14.16
Structure of the individual layers for a low temperature connection
hows the result of a load change test with one module especially prepared
with chip solder and one with sintered chips. This clearly shows that the junction
temperature T
of the soldered module increases after several thousand cycles. This is
an indication for delamination of the solder between chip and DCB, which leads to an
increased thermal resistance, and thereby the resulting temperature increase. Due to
the fact that the test was continued under the same load conditions, the chip
temperature rises far above the maximum allowed temperature of 150°C. The final
failure then occurs at about 34000 cycles due to the lift-off of the bond wires from the
chip surface. With the module with sintered chip, however, the system remains stable
up to about 62000 cycles before the chip-to-DCB bond connections show fractures. This
fatigue of bondwires canbe explainedwith the thermal andmechanical stress.
Fig. 14.17
Examples for low temperature joining (LTJ)
A general problem of low temperature joining is the introduction into series production,
since it is a slow and sequential process. This connectionmethod only seems to be of
limited use for high-volume IGBT module manufacturing, despite its technical
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