Eutectic solder bumped flip chip development

Recently, smaller, thinner and higher density packaging technology is demanded. Flip chip interconnection is one of solution to these demands. We have developed solder bumping and wafer sorting processes for bare dice with eutectic solder bumps. The highlights of our solder bumping and wafer sorting process and the reliability test results are shown. The results proved that our bare chips have good reliability, allowing the bumping process to be applied to mass production product. Next we report some experimental results of the wafer sorting process, which is the key process for mass production of bare chips. For peripherally bumped bare chips, we chose a conventional type probing card, the cantilever needle card. We carried out some experiments with four cards which had different needle heads, and decided the best head shape. Using the best card, we investigated the relationship between the overdrive and the amount of bump height deformation. We demonstrated that the deformation can be controlled to smaller than 5 μm when operating a 75 μm overdrive from all pin contacts. The card can be cleaned better by brushing than by polishing with ceramic plates. To choose probing cards for area bumped bare chips, we did some experiments with three types of probing card: the cantilever type, the bumped type, and the cobra type. Results showed the cobra type is best suited to area bumps