Ball bumping and coining operations for TAB and Flip Chip

Abstract

The process of using a ball bonder to form bumps on a chip, for subsequent TAB or Flip Chip attachment to a substrate, has now reached the production stage. A number of companies are using the process for full scale production. Other companies are using the process for rapid prototyping and limited quantity production. It requires no masks, uses existing equipment, and in many cases provides the most cost effective method for depositing bumps on chips. Two process variations are prevalent. 1. Bumping and coining, is a process where a normal ball bond with a short ductile fracture tip protruding from the top of the ball is bonded to the device, then coined flat by a second stage operation. 2. The stud bumping process produces a short loop and the crescent bond is placed on the shoulder of the ball.