Stress relieving solutions for a WLCSP design with a bulk / bulk copper layer

摘要

A wafer level chip scale package will be described. At least one redistribution layer is connected to a wafer through an opening through a first polymer layer to a metal pad on an upper surface of the wafer, wherein the redistribution layer has a roughened upper surface and wherein holes are formed through the at least one redistribution layer in a region the rewiring layer has an area of more than 0.2 mm. At least one UBM layer contacts the at least one redistribution layer through an opening in a second polymer layer, wherein the second polymer layer contacts the first polymer layer within the holes, thereby promoting cohesion between the first and second polymer layers, and wherein the roughened top surface is one Promotes adhesion between the at least one redistribution layer and the second polymer layer.