ABSTRACT
The effects of environmental conditions on the interfacial adhesion between screen-printed Ag film and polyimide substrate interface are quantitatively evaluated using the 90° peel test. The adhesion of printed patterns is varied by annealing time and atmosphere conditions. The peel strengths of air, high vacuum, and N2 atmosphere samples increase after post-annealing for 24 h, which are closely related to the curing effect of binder in Ag paste. The peel strengths of air, high vacuum, and N2 atmosphere samples decrease after post-annealing for 48 and 100 h. Peel strengths of samples after 48 h post-annealing in air are lower than in high vacuum and N2, indicating the effects of post-annealing atmospheric conditions on interfacial adhesion strength. The decreased adhesion strength during post-annealing seems to be closely related to Ag2O formation at screen-printed Ag/polyimide. Therefore, the optimum annealing conditions of Ag binder must be carefully applied to obtain maximum interfacial adhesion. Furthermore, it is important to control Ag2O formation during environmental reliability testing.
ABSTRACT
The effects of annealing, electromigration, and thermomigration on volume shrinkage and voiding mechanisms of Cu/Ni/Sn-2.5Ag microbumps are systematically investigated by using in-situ scanning electron microscopy under current stressing of 1.5×105 A/cm² at 150 °C. The resistance increases rapidly in the initial stage due to formation of intermetallic compounds (IMC)s followed by a gradual increase in resistance. Growth of Ni3Sn4 IMCs is controlled by a diffusion-dominant mechanism, and voids and volume shrinkage are closely related to IMC phase transformation of (Au, Ni)Sn4 to Ni3Sn4 in microbumps.
