Method for attaching solderballs by selectively oxidizing traces

摘要

A solder mask is placed on a substrate but this solder mask is used to control solder spread but merely helps to protect traces that are distant from the bond pads. The solder mask has an opening that is preferably greater than the area of a die to be attached; this opening exposes both the bond pads and at least portions of traces proximate to the bond pads. The portions of the traces that are proximate to the bond pads are oxidized, thereby preventing solder from flowing onto these portions of the traces during the solder reflow process.