Effect of Bond Pad Surface Finish on AuSn Solder Bumping Using Laser Solder Jetting

摘要

Laser solder ball jetting is tremendously flexibility along with its advantages of no mechanical stress and low thermal on the processes packages during the assembly process. In comparison to reflow soldering using conventional method, laser reflow is more suited for solder ball alloys with high temperature due to its localized heating capability and high energy input [1]. Due to an increase in the cost price and demand of Gold (Au), Palladium (Pd) and Platinum (Pt) materials are explored as alternative material for the pad. Palladium (Pd) and Platinum (Pt) material are used in automotive catalytic converters, electrodes in medical equipment, and in fine jewelry. In this paper, we will be evaluating laser solder ball jetting process, comparing 120μm ball direct eutectic AuSn solder bumping onto different surface finish such as Au, Pd & Pt. The laser jetted direct eutectic AuSn of 120μm ball size solder bumps were observed to have a good wettability and hemispherical shape bumps on the Au bond pad surface. Au surface gives a better wettability and hemi-spherical shape bump as compare to Pd and Pt as ball height measurement of the Au is lower compare to Pd and Pt. The ball shear strength for thermal aging and comparing the failure mode on direct eutectic AuSn solder ball at 125°C for 24hrs, 500hrs and 1000hrs on different surface materials are conducted. Pd material showed a promising result that allows it to replace the costly Au surface.