Interfacial Reactions in Sn-0.7wt.%Cu/Ni-V Couples at 250°C

Abstract

The Delco process is a major flip chip under-bump metallurgy process and its contact is soldered with the Ni-7wt.%V substrate; there are, however, only a few studies on the interfacial reactions between solders and Ni-V alloys. This study examines the interfacial reactions of the Sn-0.7wt.%Cu alloy with the Ni-7wt.%V, Ni-5wt.%V, and Ni-3wt.%V substrates at 250°C. It is found that the interfacial reactions between Sn-0.7wt.%Cu and Ni-V alloys are different from those between Sn-0.7wt.%Cu and pure Ni. In addition to the formation of the Cu 6 Sn 5 phase, a new Sn-rich phase, denoted the Q phase, is found in the Ni-V substrate couples. Nucleation of the Ni 3 Sn 4 phase is at a much earlier stage and the rates of consumption of Ni are much higher in Ni-V substrate couples than in Ni substrate couples. Knowledge of these different reactions is important for proper assessment of the flip chip products.

Shear and Pull Testing of Sn-3.0Ag-0.5Cu Solder with Ti/Ni(V)/Cu Underbump Metallization During Aging

“…It should be noted that the measured compositions in this study are different from those in the literature. 8,11,16,17 In the literature, the composition of the Sn-patch was usually determined randomly for two or three points, and the average composition was reported. In this way, it is difficult to determine the exact compositional variation for a nonuniform sample.…”

“…[8][9][10][11][12][13][14][15] Most literature focuses on the interfacial reaction between Ni(V)-based UBM and solder. [8][9][10][11][12][13][14][15][16][17] Notably, the Sn-rich phase, the so-called Sn-patch, would grow into the Ni(V) layer during reflow and aging. The formation mechanism of the Sn-patch is possibly due to the fast diffusion rate of Sn atoms in solder; however, the detailed mechanism is not yet clear.…”

Interfacial Reactions in Sn-Pb/Ni-8.0 at.%V Couples

“…[8][9][10][11] Similar examinations have been carried out on Sn-Cu/Ni-V couples. 12,13 In addition to the formation of a Cu 6 Sn 5 phase and the Ni 3 Sn 4 phase as in Sn-Cu/Ni couples, 14 the formation of an amorphous phase region has been observed in Sn-Cu/Ni-V couples. A Sn-Ni-V ternary phase was also found in the solder/Au/Ni-V/Ti reaction, 15 but no further characterization was reported.…”

“…The Cu 6 Sn 5 phase becomes the dominant reaction product with a small amount of Cu in the solder; 8,9,14 however, the formation of this T phase is only found in solder/Ni-V couples. [8][9][10][11][12][13] The Ni-8.0 at.%V substrate used by Chen et al [8][9][10][11][12][13] was a thick foil, different from the thin Ni-8.0 at.%V film used by others. [2][3][4][5][6][7] In a couple prepared with a thin Ni-8.0 at.%V layer, 2-7 the T phase can be absent because there is not enough Ni-8.0 at.%V material, or it could be overlooked because the layer is too thin.…”

Impact Testing of Sn-3.0Ag-0.5Cu Solder with Ti/Ni(V)/Cu Under Bump Metallization After Aging at 150°C

“…In fact, the test speed in the previous studies was too low to evaluate the effect of Sn-patch on solder joint reliability. Based on the literature, 14,15 high-speed testing (i.e., at more than 10 mm/s) is a more effective method for the measurement of impact fracture strength in solder joints. Morita et al 16 reported that the effect of Kirkendall voids on Sn-Ag-Cu/Cu solder joints was more evident with high-speed than low-speed testing.…”