Mechanical reliability of micron-size solder joints fabricated by explosively reacting nanolayers

In this article, mechanical reliability of solder joints fabricated using Al/Ni reactive film is described. Rectangular solid Si sample with solder-bonded section was prepared for measuring the bond strength using developed four-point bending test equipment. By changing Al/Ni film thickness, interlayer between SnAg solder and Si, and pressure load during bonding, the fracture strength was investigated. In case that 10nm-thick Au/Ni was used as the interlayer, fracture occurred at the interface between the interlayer and Si. On the other hand the specimen with Au/Ni/Cr interlayer fractured at the interface between melted and non-melted SnAg solder. The strength in thick-Al/Ni specimen was higher than that in thin-Al/Ni specimen. It was found that sufficiently melting the solder during Al/Ni flash heating is important for high strength solder joint.