The impact strength of lead-free solder joints in a Ball Grid Array (BGA) package was evaluated using the impact-bending test, and the effect of the strain and the strain pulse duration in the Printed Wiring Board (PWB) on the impact strength was studied. The impact strength of the solder joint strongly depends on the maximum strain and the strain pulse duration in the PWB. The failure mode of lead-free solder joints differed with the fracture lifetime. When the fracture lifetime was short, the crack propagated completely within the intermetallic compound region. On the other hand, when the fracture lifetime was long, the crack initiated in the bulk solder region and propagated into the intermetallic compound region. These failure modes depend on the maximum strain and the strain pulse duration in the PWB.

View full abstract

We have developed a new plating process, which shortens the plating time by about 60% as compared with that of conventional through-electrode forming processes for three-dimensional mounting technologies. Using the new plating system, we have succeeded in the complete filling of 10 μm diameter Cu through-electrodes with an aspect ratio of 7.0. The microstructures and electrical characteristics of the Cu films formed by the new high-speed plating process were found to be at the same level as those formed by conventional plating.

View full abstract