Reliability Control in Parallel Gap Welding

Parallel gap welding is a reliable method for joining integrated circuit flat-packs to printed circuit assemblies. Keys to the reliability of the process are the proper selection of materials, the inherent precision of the equipment, and the amenability of the welds to visual inspection.

Welds between gold-plated Kovar leads and gold-plated copper-land, glass-epoxy boards were visually inspected, and then either examined metal-lographically or tested for mechanical strength.

Normal distribution and extreme value statistics were used to evaluate the weld strength data. If proper control is exercised, over 10, 000 welded connections must be made to expect one weld with a strength value less than 0.5 pound.