The invention provides a method for bonding a
copper wire of a power device, in particular to a method for bonding the
copper wire (91) with the
welding joints of a
chip (511). The method comprises the following steps: burning the lower end (9) of the
copper wire into a spherical shape; applying the pre-pressure on the spherical end of the
copper wire, i.e., flattening the spherical end of the
copper wire to increase the contact area of the spherical end of the
copper wire and the
chip; and
welding the spherical end of the copper wire to the bonding area of the
chip on an ultrasonic-
welding basis, wherein the pre-pressure is preferably 80g to 120g, and the time for applying the pre-pressure is preferably 80ms to 150ms. By increasing the contact area, the invention can improve the stability and reliability in welding the copper wire and the chip; the bonding production can be smooth without breaking the copper wire, breaking the welding joints or shutting down; the chip cannot be damaged by bonding; and the
bonding strength of the copper wire, the chip and the pin is high. By substituting the copper wire for the gold wire for bonding, the invention can reduce the cost for the bonding
metal wire by about 84%, reduce the overall cost for the product by 5.7% to 8.6%, reduce the
saturation voltage drop parameter of the product and improve the reliability of the product; and compared with the gold wire, the
conductivity of the copper wire is increased by about 20%, thus improving the reliability of the product.