Reliability of Gold Wire Bond Interconnects in High Temperature (450°C), High Sheer Force (14,500 G) Applications

摘要

Researchers at Arkansas Power Electronics International, Inc. are developing and testing packaging technologies that will allow silicon carbide devices to be used to their full potential in extreme operating environments. The present work describes the testing of small diameter (0.7 mil and 1 mil) gold wire bond interconnects for use in high temperature (450°C) under parallel and perpendicular sheer forces to nearly 14,500G's. Several wedge bonds were performed using a K&S 4523 semi-automatic wedge bonder onto thin-film gold and thick-film gold substrates. The wire bond settings (ultra sonic power, time, and force) were optimized for each wire diameter on each substrate. The bond strengths were optimized using the Dage 4000 vertical pull test. Each test board consisted of 180 wire bonds of varying length in the parallel direction and 165 wire bonds of varying length in the perpendicular direction. Two additional thick-film boards were produced with several wire bonded dummy die in order to test the wire bonds in a more realistic situation. All test boards were attached to gold packages. The test setup consisted of a heated spin arbor with the electronic housing at a radius of 5.67". The speed was increased to 8621rpm (11,962 G's) over 8 minutes. The temperature was increased to 450°C over at least 15 minutes. After reaching 450°C, the speed was cycled from 8621rpm to low spin speeds (500-1000rpm) 10 times with transient times of 8 minutes. The speed was then cycled from low spin speeds to 9483 rpm (14,470 G's) 10 times with transient times of 8 minutes. The analysis of the wire bonds consisted of SEM imaging before and after to determine extent of plastic deformation. Destructive vertical pull tests were also performed after the spin test to compare pull strengths between spun and control boards.