Effect of Hook Location for Ultra Fine Pitch Wirebonding Pull Testing Method

Abstract

Over the years the methods for checking bonding quality during volume production still remains the same. These inspection methods like ball shear to test the first bond quality and wire pull to test the second bond integrity and quality have proven to be acceptable and achievable for many current industrial needs. However, driven by the relentless pursuit of dimensional reduction in wire bonding technology which calls for reduction in wire diameter, these conventional methods may not be sufficient. The interaction between machine, bonding tools, materials and the different categories of failure modes and mechanism during this quality test has become much more sensitive. The intent of this paper is to study and define the different categories of failure modes during 2nd bond test for ultra fine gold wire from 15 micron diameter up to 50 micron diameter. Therefore, lifted stitch or lifted 2nd bond which is a failure description known to be a ‘reject’ before can be re-visited. Analysis found that the two different test locations revealed that test location B or placing the hook as near possible to the leads where the 2nd bond was bonded is the better method to test the 2nd bond strength and performance as compared to the earlier bond pull method (location A).