Nickel plated leadframe eliminated spot silver plating has become common for power transistor toreduce plating cost. As being performed on nickel surface instead of silver, its solder die-bondabilitytends to be critically influenced by bonding conditions such as atmosphere, temperature,contamination on nickel and so on. Influence of co-deposited impurity in nickel plating on its solderability was studied. Withincreasing brightness of plating, its solderability becomes worse especially in the atmospherecontaining several hundreds ppm of oxygen. ESCA analysis shows sulfur concentrated on nickelsurface during preheating for die bonding, and oxidized when annealed in high oxygen containingatmosphere. Solderability of nickel plating is influenced by oxidation of sulfur compounds due tobrightener, not simply by oxidation of nickel. Double layered nickel plating, which is mat nickel coated bright nickel plating, has both goodsolderability and brightness by optimizing those thickness.
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