Characterization of hybrid underfill for low-temperature process applicable to flexible substrate

As the interests in wearable devices are become growing, flexible substrates is being extensively investigated. In this study, new hybrid underfill for a low temperature process to create an electrical interconnection system on flexible substrate was studied. Hybrid underfill material is composed with underfill materials and 54Bi27In19Sn solder powder which has melting temperature at 83°C. For the stable chemical reaction, process temperature was set to 130°C. Hybrid underfill material has advantage of reducing processing step because the processing step such as solder joint formation, fluxing, cleaning, underfill step can proceed at a time. To optimize the wettability of solder powder, compositions and the ratio or the materials and processing conditions are controlled. By controlling the various conditions such as reductant and catalyst of hybrid underfill material, we optimize the low temperature process. As a result, solder joint is formed stably at a low temperature.