A CONNECTIVE MEDIUM AND A PROCESS FOR CONNECTING ELECTRICAL DEVICES TO CIRCUIT BOARDS

摘要

A connective medium for use in ball grid arrays for connecting electronic devices to circuit boards comprising high melting point solder alloy spheres (32) coated, by electroplating, with an outer concentric layer of a lower melting point solder alloy (34) of uniform thickness. In a further aspect, a leach barrier (30) is coated on the high melting point solder alloy (32) prior to electroplating the low melting point solder alloy (34) thereto. The leach barrier (30) forms a barrier to prevent the lead from leaching from the high melting point lead solder spheres (32) into the low melting point solder alloy (34) during the reflow heat treatment in the mounting process.