SIZE EFFECT OF MECHANICAL BEHAVIOR OF MINIATURE SOLDER JOINT INTERCONNECTIONS IN ELECTRONIC PACKAGING
电子封装微互连焊点力学行为的尺寸效应

Mechanical behaviors of miniature solder joint interconnections with different scale matches, diameter (d) in the range of 200—575 μm and length (l) of 75—525 μm, were investigated by using quasi–static micro–tensile testing. The results show that the joint geometry scaling factor (d/l) plays an important role in influencing the mechanical constraint level and tensile strength of the solder joints. However, with increasing d/l, the tensile strength of the joints does not always increase and not always exhibit a similar trend to that predicted by Orowan approximation equation, but there is an inverse size effect on the solder joint strength. For both lead–free and lead–containing solders, the correlation between the tensile strength and volume of the solder joints largely follows inverse proportion function equation, i.e., σF Joint = 1/(Ad2l) + B, where tensile strength of the solder joints increases obviously with the decrease of the solder joint volume and there is a so–called "solder joint volume effect", that is, the smaller the solder joint volume, the higher the solder joit strenth.