Online methods to measure breaking force of bonding wire using a CMOS stress sensor and a proximity sensor (original) (raw)

Two real-time, in situ methods to measure the breaking force of fine bonding wires while on the wire bonder are reported and compared. The first method uses a special test chip with a piezoresistive microsensor integrated next to the bonding pad. A 25 m diameter Au wire piece is attached with a ball bond to the test pad of the microsensor. The wire piece between the ball bond and the lower edge of the wire clamps is 15 mm in length. The clamps tear the wire at a speed of 2 mm/s. The wire breaks at the heat-affected zone (HAZ) next to the ball bond. The microsensor is calibrated using FE models. The numerical results show that the microsensor signal is highly sensitive to ball and pad geometry, values of the piezoresistive coefficients, and the z-location of the microsensor under the bonding pad. This results in a high estimated error of about 46% for the calibration factor of the microsensor.