Effect of electroless Ni-P thickness on EFTECH 64-Ni, EFTECH 64-Cu and C194-Ni bump

Long-term reliability of board level solder joint is significantly affected by the properties of surface finish. Recently, Electroless Nickel Immersion Gold (ENIG) was offered as alternative surface finish with high solder joint strength to reduce cost. However, the use of electroless Ni-P deposition produces intermetallic compound (IMC) that exists between solder Ni-P alloy boundaries after thermal aging process. In this study, the effect of various Ni-P deposit thickness and different substrate on its failure mode is studied by measuring its shear strength and observing shear morphology after thermal aging. The Ni-P alloy deposit thickness is set to 0.5, 2.5 and 4.5 μm. The substrate used EFTECH 64-Ni, EFTECH 64-Cu and C194-Ni bumps. From the results, the use of EFTECH 64-Cu substrate produce fracture failure at both Ni-P - Substrate and Ni-P - IMC compare to other substrates. Aside that, C194-Ni alloy produces consistence shear strength but unable to produce consistence standard deviation. As a conclusion, the EFTECH 64-Ni bump is consider as suitable substrate material due no fracture was observed between the substrate boundaries and the IMC boundaries.