Solderability evaluation of printed silver solder pad for wafer-level packaging

Due to the increasing demand for smaller package size of the portable electronic devices, wafer-level packaging is quickly becoming the packaging technology of choice. One of the key enabling structures for the wafer-level packaging is the redistribution layer. At the same time, printed electronics technology keeps rapidly developing in recent years and can be utilized to fabricate the redistribution layer, which can greatly reduce packaging costs and enhance manufacturing flexibility. The material chosen for the printed pad or trace is usually the silver nanoparticle inks. However, the performance of this material as the solder pad should be investigated. In this paper, we conducted a brief study on printed solder pads by different commercially available silver nanoparticle inks. The results show that the silver pad almost completely dissolves into the bulk solder and result in very poor strength which suggests that silver nanoparticle ink may not be a good candidate for solder pads.