| 摘要 |
<p>PURPOSE:To improve solderability by coating an outer lead with an Sn alloy in predetermined thickness and coating the upper section of the Sn alloy with the alloy of a specific metal in prescribed thickness. CONSTITUTION:A lower layer 2 coated with Sn or an Sn alloy in thickness of 1mum or more is formed onto a base body 1 for an outer lead, and the upper section of the lower layer 2 is coated with an upper layer 3 consisting of at least one kind of Au, Pd, Ag or In or these alloy in thickness of 0.03mum or more. The alloy of Sn-Pb, Sn-Pb-Sb, etc. is available as a foundation metal besides Sn, and electroplating is used generally. The alloy of Ag-Pd, Ag-Sn, etc. is available as the metal of the upper layer besides said metals. An Sn section reacts with Cu in a base body 1' by heating at the time of mounting to shape a Cu.Sn compound layer 2', and a residual Pb section covers the layer 2' as a Pb-rich layer 2'' to prevent the oxidation of the base body 1'. 2-7mum is preferable as the thickness of the lower layer, and 0.03-1mum, particularly, 0.05-0.5mum, is practically desirable as the thickness of the upper layer.</p> |
