Ultrasonic-Assisted Micro-Silver Paste Sintering for Flip-Chip Bonding

We adopted a novel method to achieve a high-density microbump connection through microsilver paste sintering at low temperature quickly with the help of ultrasonic. Sliver paste sintering with its unique performance has the potential as an alternative to Pb-free solder and this has been generally accepted. However, it has not been applied in the field of high-density bump interconnection. The usual sintering problem is time-consuming, porous, and low wettability. Many sintering experiments were carried out in two copper plates, focusing on the study of the sintering mechanism. We conduct our research in a manner that is the closest to production, which will be helpful to production. We solving the problem that how to coat sliver paste on a high-density small space microbump uniformly. In this article, the vibration of ultrasonic, sintering curve, shear strength, fracture surface, and cross section were studied to help understand the fundamental mechanism. Experiments show that ultrasonic vibration increases the density of silver particles and generates a certain amount of frictional heat, promoting the adjacent nanoparticles to become agglomerated or aggregated. We can conclude that it can achieve Cu–Cu robust fast interconnection at low temperature by microsilver paste sintering with the appropriate sintering method and the suitable process. This study provides a possible method for the copper pillar microbump interconnection.