Herein,the ultrasonic flip chip bonding process parameters of golden bumps,including welding force,ultrasonic power,and welding time,are systematically studied.Results reveal that the greater the welding force,the greater the die shear force;insufficient welding force can lead to an insufficient bump shape change and poor contact with the substrate;and excessive welding force causes severe deformation of the bump,resulting in it being completely flattened and spreading along the perimeter to eventually squeeze the chip pad.A reasonable welding force was determined to be in the range of 35-45 g/ball.Furthermore,the greater the ultrasonic power,the greater the die shear force.When the ultrasonic power is 40％or above,the die shear force tends to be flat,whereas when the ultrasonic power exceeds 60％,the frame of the chip pad will crack.Thus,a reasonable ultrasonic power value should be 40％.Finally,the die shear force of the chip first increases and then decreases as the welding time increases.However,if the ultrasonic time is excessively long,it can damage the welded interface by repeated friction and plastic deformation.When bonding strength is low,an optimal welding time of 1 s is recommended.
万方数据
维普
