Reflow of low melt solder tip C4's

摘要

An array of C4 solder bumps and a method for making is described incorporating an array of conductive areas on an electrical device, each conductive area having a layer of ball limited metalurgy at the device surface and two layers of solder having respective melting temperatures to form the C4 structure. The method includes melting the second layer of solder in the down position or towards earth to form a C4 solder ball or bump. The invention overcomes the problem of low temperature solder from wicking over the sidewall surfaces of the high melt solder of the C4 structure and attacking the edges of the underlying seed layers of the ball limited metalurgy.