Solder alloys for semiconductor elements - contg. copper as well as aluminium and germanium for shorter soldering time at lower temp.

摘要

An improved solder alloy results from doping the usual Al-Ge solder (45-58% Al, 42-55% Ge) with small concns. of Cu. The alloy produced can be used either in strip form (added Cu up to 2%) or as a powder (added Cu up to 10%). The alloy is suitable for automatic operations in microelectronics and bonds at 450 deg C and contact times of 1 sec. or less. USE/ADVANTAGE - The prod. is useful for the automatic soldering of semiconducting transistors (chips) at lower contact times and temps. than conventional soldering compsns.. Improved wettability on the chip and substrate results from Cu addn.. In an example a solder alloy according to the invention was made by blending a solder of 55.5% Al and 44.5% Ge (100 pts. wt.) with Cu 1.60 pts. wt. to give a compsn. (wt.%) Al 54.97; Ge 43.93; and Cu 1.28. This was converted to strip by normal processes. It had a hardness of 86 MVm and could be reeled on to a mandrel of 20 mm dia.. During stamping the edges cut well and the strip is suitable for automatic soldering processes for chips at 450 deg C and a contact time of 1 sec.. The wettability on the chip was 70-80% and also 70-80% on the substrate (chemically polished Fe-Ni alloy) which is an improvement of some 25% as a result of the innovation.