Fracture of the Leads of Integrated Circuits with TO Package

The Kovar alloy leads broke from two integrated circuits (ICs) with TO (Tin Outline) package. Through the metallurgical microstructure analysis, energy dispersive spectrometer (EDS) analysis and fractography analysis, the failure mode of the leads was found to be stress-corrosion-cracking. After checking the whole plating process, it was found that the residual chloride ions resulted in stress-corrosion-cracking. The chloride ions were absorbed inside the residual organic containment below Ni-plating layer. And a corrective measure was proposed.