METHOD FOR FORMING A WAFER LEVEL CHIP SCALE PACKAGE, AND PACKAGE FORMED THEREBY

摘要

A layer of gold (405) is disposed on upper surfaces (225) of copper pillars (210) on a bumped wafer (205). Coating material (410) is then applied to a level which is less than the height of the copper pillars (210), and etchant is disposed to remove coating material on the layer of gold (405) and to remove coating material (410) adhering to side surfaces of the copper pillars (210). Solder balls (405) are then disposed on the ends of the copper pillars (210), with the copper pillars (210) protruding into the solder balls (405). In an alternative embodiment, solder balls are first attached to the free ends of the copper pillars and coating material applied to encapsulate the solder balls and the copper pillars on the semiconductor wafer. An etchant is then used to remove a portion of the coating material, substantially exposing the solder balls.