| 摘要 |
PROBLEM TO BE SOLVED: To avoid damage to leads due to electroless plating by providing a thicker Sn plated layer on ball pad leads than an Sn plated layer on inner leads. SOLUTION: An alkanol sulphonate electroless plating liq. is applied to form an Sn plated layer of 0.4μm on a resist surface as a plated part 6b. After removing a plating resist, a photo resist is applied to a ball pad-forming surface, exposed to form a wiring pattern 3, developed, coated with a backing agent, and etched to form a wiring pattern, inner leads 4 and ball pad leads 6a. An insulative protection paint is applied to the entire surface from the outside of the ball pad part 6 to the inside of a device hole 3 and heated at 150 deg.C for 60min. Using an electroless plating liq. an Sn plating is applied to form plated inner leads of 0.4μm thick. From evaluated results it is verified that the inner leads are 0.2μm thick and Sn plated layer on ball pad part 6 is 0.5μm thick.
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