Preparation, structure, and fracture modes of Pb-Sn and Pb-In terminated flip-chips attached to gold capped microsockets

The effects of using nickel deposited from an electroless phosphorus-based bath as the base metal to achieve solder wetting for chip interconnection is discussed. Specifically discussed are the degradation effects on solder wetting caused by precipitate formation during process thermal exposure, and the use of a gold cap to prevent the problem. The overall metallurgical characteristics of both lead-tin and lead-indium controlled-collapse chip connection joints, as well as their relation to performance (e.g. fracture mode and fatigue life) are discussed. Preliminary processing and microsocket preparation are discussed.<
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