| Plasma treatment was applied to remove the surface oxide of Sn-3.5 mass%Ag solder bump for fluxless flip chip bonding. The effects of plasma process parameters, such as plasma power, treatment time, chamber pressure and H_2 addition, on Sn-oxide etching characteristics were evaluated by Auger depth profile analysis. The die shear tests were performed to evaluate the adhesion strength of Sn-3.5%Ag solder bump flip chip. The addition of H_2 to Ar plasma improved the oxide etching characteristics. A low chamber pressure was more effective in oxide removal. The die shear strength of the plasma-treated Sn-3.5Ag solder flip chip was higher than that of the non-treated chip, but it was lower than that of the fluxed chip. The difference in the die shear strength between the plasma-treated specimen and the non-treated specimen increased with increasing bonding temperature. The plasma-treated flip chip fractured at the solder/TSM interface at low bonding temperature, but at the solder/UBM interface at high bonding temperature. |
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