Influence of Shear Height on Shear Strength of Tin-Lead Solder Ball Bonding

Abstract

The crack generation energy U 1 and the crack progress energy U 2 of eutectic Sn-37 mass%Pb solder ball and Sn-36 mass%Pb-2 mass%Ag one were surveyed by the shear test. Both balls were bonded at various reflow cooling rates (10-200 K/min). The shear test was carried out under the condition of two kinds of the shear height, Z = 0 µm and Z = 200 µm. U 1 and U 2 were calculated by multiplying the shear strength by the shear distance. Though U 2 was independent on the cooling rate, the ball composition and the shear height, U 1 changed depending on these parameters. Only U 1 of Sn-36 mass%Pb-2 mass%Ag ball bonding cooled at 200 K/min dropped sharply though U 1 of both ball bonding was almost the same and increased with the faster cooling rates in case of Z = 0 µm. U 1 of Sn-36 mass%Pb-2 mass%Ag ball bonding was higher than that of the eutectic ball at each cooling rate as a result of the shear test at Z = 200 µm. The needle shape Ag 3 Sn intermetallic compound in Sn-36 mass%Pb-2 mass%Ag ball and near the interface contributed mainly to the lower U 1 at Z = 0 µm because Ni 3 Sn 4 reaction layer formed at 200 K/min was thin. The higher U 1 at Z = 200 µm was due to the fine lamellar structure (Sn phase/Pb phase) in Sn-36 mass%Pb-2 mass%Ag ball. The shear property of the same ball depended on the shear height in the present study.

Interfacial reactions and compound formation in the edge of PbSn flip-chip solder bumps on Ni/Cu under-bump metallization

“…In general, the bump strength can be estimated by a shear test. [9][10][11][12] The knowledge for interfacial reactions between solder bumps and UBMs is essential for its potential effect on the bump strength. It is believed that elemental distributions in the edge of solder joints after heat treatment is as important as that in the center.…”

Shear Fracture Behavior on Ball Grid Arrayed Tin–Silver–Copper Solder/Pure Copper Pad Joint Interface

“…[1][2][3][4] Shear test and pull test have been carried out to investigate the joint interface strength. [5][6][7][8] However, true joint strength obtained by these conventional tests using print board cannot be evaluated correctly because the fracture occurs on only solders side, not on joint interface. Commercial print board is covered with resist layer that has about 20 mm in thickness except Cu electrode.…”

“…The reaction layer was Cu 6 Sn 5 intermetallic compound as explained in Paragraph 3.4. When the commercial print board with the normal electrode (Cu/Ni-P electroless plating/Au vaporizing layer) is used, (Cu,Ni) 6 Sn 5 forms on the joint interface between Sn-Ag-Cu solder and electrode. [17][18][19] However, very rough reaction layer with characteristic shape was observed in case of using pure Cu pad without UBM layers.…”