Practical application of laser inner lead bonding to TAB devices over 500 pin counts

Tape automated bonding (TAB) is a key process for high pin count and high speed LSI devices. We developed a fully automated laser inner lead bonder for 500-1000 pin class TAB devices. The laser bonding was applied to 600-lead, 15×15 mm device having 96 μm lead pitch. This laser bonder consists of a pulsed Nd:YAG laser, a laser beam positioner with a real time bonding process monitor, a lead inspection head, a bonding stage, loading and unloading mechanisms of wafers and tape carriers, and their controller. The bonder had a total bonding accuracy of 10 μm, a bonding rate of 6 leads per second. No failures were observed after environmental tests. From the thermal analysis of the bonding area under laser irradiation, the contact states between the lead and the bump were the most important parameter for good bonding process. The real time monitoring of the lead temperature with an infrared sensor verified the analysis results thus providing an effective method to estimate bonding quality