Effects of corner and edgebond epoxy adhesives on board level solder joint reliability of BGA mezzanine connectors

In this paper, the button shear tests of seven kinds of epoxy used for corner/edge bonding of BGA mezzanine connectors are performed firstly for determining adhesive strength between the epoxies and each relevant surface material. The effect of corner/edge bonding epoxy on the board level solder joint reliability of BGA connectors is also investigated including mechanical drop and 4-point bending tests. In addition, the pre-conditioning effect of thermal aging (1000 hours at 125°C) and accelerated temperature cycling (ATC, -40~125°C, 500 cycles) on the reliability of connectors with corner/edge bonding epoxy is discussed. The failure modes and fracture strengths of the button shear and board-level tests are cross-referenced for comparison and assessed for correlation. The results from the present study not only contribute to the characterization and selection of corner/edge bonding epoxies for BGA connectors, but also improve the understanding of the corresponding relationship between simple button shear and the more complex and costly board-level reliability tests.