SOLDER LAYER, SUBSTRATE FOR DEVICE JUNCTION UTILIZING THE SAME, AND PROCESS FOR MANUFACTURING THE SUBSTRATE

摘要

A solder layer, a substrate for device joining utilizing the same and a method of manufacturing the substrate are provided whereby the device joined remains thermally unaffected, an initial bonding strength in solder joint is enhanced and the device can be soldered reliably. The solder layer formed on a base substrate (2) consists of a plurality of layers (5a) of a solder free from lead, which are different in its phase from one another. They are constituted by a layer of a phase that is completely melted, and a layer of a phase that is not completely melted at a temperature not less than a eutectic temperature of the solder. The solder layer (5) can be applied to a device joining substrate (1) comprising an electrode layer (4) formed on the base substrate (2) and the solder layer (5) formed on the electrode layer.