Power Cycling at High Temperature Swings of Modules with Low Temperature Joining Technique

Standard packaging and interconnection technologies limit the maximal junction temperature (T_jmax) to about 150degC at present. This restriction is caused by the limited power cycling capabilities of Al bond wires and of soft solder joints. Important applications of power devices, however, require operating temperatures of 175degC or even 200degC. To evaluate the suitability of the low temperature joining technique (LTJT) for future module set-up, test samples were prepared and investigated. Already the replacement of only the chip-to-substrate solder joint (one-sided LTJT) improved the power cycling capability at DeltaT_j=130K five times or at a DeltaT_j=156K ten times compared to the expected capability of soldered and wire bonded devices at these conditions. Application of LTJT to top side chip connections also, i.e. additional replacement of bond wires by silver stripes joined by LTJT (double-sided LTJT), yielded a further increase of power cycling capability