Evaluating silver paste strength for die bonding during the reflow soldering process is important, as silver paste fracturing is one of the main causes of package failure. First, we assumed that the fracturing was caused by thermal stress and vapor pressure at the interface between the resin and the copper lead frame. Next, we measured the silver paste fracture strength using a three-point bending test and a bonded specimen with silver paste. Finally, we predicted the occurrence of silver paste fracturing by calculating the silver paste stress during reflow soldering process and comparing it with the measured fracture strength. Results obtained in strength evaluation analysis were consistent with those obtained in package reflow tests, indicating that this method can be used to predict the occurrence of silver paste fracturing.
Analysis of the formation mechanism of coarse-dense structure of silver paste in die bonding
