| 摘要 |
PURPOSE:To contrive improvement in resistance to release of solder by a method wherein the outside layer of double layer plating is thickly formed. CONSTITUTION:When a soldering work is performed, an Ni-Sn alloy layer is grown on the contact interface between Ni plating and solder, and its thickness reaches 0.1-0.3mum. Then, the alloy layer is increased to 0.3-0.5mum or thereabout by the thermal variation with time after soldering. When the thickness of the alloy layer reaches the interlayer of double layer plating, an interlayer exfoliation is generated due to the stress concentration between layers. Accordingly, the release of solder can be prevented completely by forming the plating thickness of the outside layer thicker than the thickness of 0.3-0.5mum at which the Ni-Sn alloy layer can be grown. Besides, the desired upper limit of plating thickness is 2.0mum or smaller taking into consideration of an economical reason. Therefore, the improvement in resistance to release of solder of the lead frame can be achieved by forming the oxidation-resistive Ni alloy plated layer in the thickness of 0.7-2.0mum.
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