A laser based system for tape automated bonding to integrated circuits

Abstract

A laser-based process has been developed to bond tape automated bonding (TAB) leads to integrated circuit pads. This technology has many distinct advantages over conventional TAB bonding techniques, such as gang thermode bonding and single-point thermosonic bonding. TAB laser bonding is performed by positioning a focused laser beam over a lead and then pulsing the laser once, creating a reliable metallurgical bond between the plated lead and the bump. This bonding process takes advantage of a thin tin plating to absorb the laser energy and accelerate melting of the lead and bump materials. The resulting bond, which is composed of copper and gold, has withstood exposure to damaging environments. The laser-bonding equipment consists of a pseudo-pulsed Nd:YAG laser, a high-performance laser-beam positioner, a four-axis die pedestal, and a system control computer. The laser-beam positioner and laser-pulse parameters are software-controlled. The part's alignment and bonding positions are stored in a data file, and product changeover is accomplished by reading in the new product data file. The system can bond over 60 leads per second and is ideal for bonding high-pad-count or stress-sensitive integrated circuits. >