THE STUDY ON THE INTERFACIAL REACTION BETWEEN SNAGCU SOLDER AND NI(P)/AU, NI(P)/PD/AU UBMS
Authors: Jui-Yun Tsai, Josef Gaida, Gerhard Steinberger and Albrecht Uhlig Company: Atotech Deutschland GmbH Date Published: 4/8/2008
Abstract: The interfacial reactions between Sn3.5Ag0.5Cu solder and two UBM layers, Ni(P)/Au and Ni(P)/Pd/Au, were studied. The reliability of the solder joints were characterized by ball shear test after multiple reflows. It was found that the reaction products at the interface were the same in the all systems after multiple reflows. However, the addition of Pd layer between Ni(P) and Au played strong effects on morphology of compounds and strength of joints as well. The morphology of the compounds were needle-shaped in the Ni(P)/Au system and were layer-shaped in the Ni(P)/Pd/Au system. The needle-shaped compounds became the weak points during the ball shear test. Therefore, the major ball shear failure mode was between the roots of needle-shaped compounds and Ni(P)/Au UBM for all multiple reflow tests. In the Ni(P)/Pd/Au system, the major fracture modes were through the solder for multiple reflow tests, indicating that the interfaces between solder and Ni(P)/Pd/Au have good adhesion.