Critical Concerns in Soldering Reactions Arising from Space Confinement in 3-D IC Packages

摘要: Six critical issues relating to interfacial reactions arising from space confinement in 3-D integrated-circuit (3-D IC) packaging are presented this paper. The first issue arises the concern that intermetallics (IMCs) may occupy a large portion of solder joint volume. It will be demonstrated is real even for Ni under bump metallurgy (UBM) or surface finish, which reacts very slowly with solders. second relates impingement and ripening IMC grains. When IMCs joint, grains growing opposite sides eventually touch each other. morphology evolution point on determines final microstructure joint. Structural defects might form as result third rise impurity concentration due consumption. Many impurities solders, such those electroplating, not soluble IMCs. As Sn IMCs, these rejected into remaining solder. Consequently, concentrations increase progress reaction. Eventually, trapped between directions. impact properties joints an important issue. fourth similar except role replaced by inert alloy elements most obvious element Ag. fifth fact that, size becomes smaller, surface-area-to-volume ratio increases. This makes thin-film layers UBM finish become ever higher. One well-known Au. so-called Au embrittlement relevant again. last volume shrinkage chemical reactions. Internal stress structure because shrinkage. Experimental evidence used paper illustrate six issues, implications discussed.