The Effect of Number of Zincation in Electroless Nickel Immersion Gold (ENIG) Under Bump Metallurgy (UBM) on Reliability in Microelectronics Packaging

This paper discusses on the effect of number of zincation in electroless nickel immersion gold (ENIG) under bump metallurgy (UBM) on reliability in microelectronics packaging. Double and triple zincation of ENIG methods were used as comparison study. The effect of number of zincation to surface roughness and surface morphology were investigated. All samples were subjected to reliability tests such as multiple reflow, high temperature storage life (HTSL) and temperature/thermal cycle (TC) according to joint electron device engineering council (JEDEC) conditions. Scanning electron microscope (SEM) and atomic force microscopy (AFM) were used as analytical tools in this study. In multiple reflow tests, no reliability failure found for triple zincation, however for double zincation of ENIG UBM, the failure revealed failure after 3 times of reflow cycle. Thermal fatigue failure for both double and triple zincation of ENIG UBM revealed after 100 hours and 200 hours of HTSL, respectively. For TC test, thermal fatigue failure occurred after 150 cycles, for both double and triple zincation of ENIG UBM. The external and internal crack observed for this failure. The crack growth for double zincation is always much bigger than the triple zincation of ENIG UBM for both HTSL and TC tests. As conclusion, triple zincation gives a better surface morphology of electroless nickel. Hence, it can achieve a reliable solder joint leads to better adhesion between UBM and solder ball therefore, it can achieve a reliable solder joint