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Low Temperature Copper-Copper Thermocompression Bonding

Successful direct copper thermocompression bonding was demonstrated at room temperature under ambient environment, yielding shear strength of 21 MPa. Studies on the effect of bonding temperature on the copper joint shear strength revealed a unique phenomenon at the low temperature regime (~80degC -140degC) whereby bond integrity degrades with increasing temperature. Beyond 140degC, direct relationship between temperature and joint shear strength was observed. A hypothesis on the bonding mechanism between copper surfaces is proposed to explain the anomalous bonding behaviour with temperature.