Joining workpieces by solder preforms without using flux - where preform is shielded from oxidn. by thin coating of non:corrodible metal such as gold

摘要

The preform is made of a metal cpd. with a low m.pt., and which is oxidisable, so the preform is coated with a metal which neither oxidises nor corrodes at the soldering temp. The metal coating is pref. a pure metal or a eutectic, and is applied by chemical- or electrol- plating, or by vacuum vapour deposition. The preform is used esp. for the assembly of microelectronic components and, in an example, the preform is coated with a thin layer of gold. Used esp. in mfg. micro-packages or chip carriers without using fluxes, which are very difficult to remove after soldering and can impair the quality of the prods.