Abstract
Ultrasonic bonding of Cu composite wire with Au coating at room temperature has been investigat-ed for packaging technique of thin film device unaccepted heating. Cu composite wire used in this study consists of Cu core of 44μm in diameter and Au coating of 3pm in thickness. Two kinds of bonding pads are used. One is Au plating film of 5-6μm in thickness on Au/Cu/Cr thin film deposited by sputtering on Cu substrate. Another is Au PVD film of 0.4μm in thickness on Cu/Cr thin film deposited on Cu substrate. Specimen has been bonded under the conditions of various ultrasonic power, bonding load and bonding time. For evaluation of a bonded specimen, the wire deformation and the 90 pull strength have been measured, and fracture surface has been observed by SEM. Main results in this study are as follows;
(1) Adhesion and rupture take place alternately and periodically during ultrasonic bonding of Cu composite wire with Au coating. Then the joint strength also increases and decreases according to those. This phenomena is more remarkable on the bonding condition of a lower load and an upper US power, and the periodic time is shorter on that of an upper load and US power.
(2) If a wire deformation ratio of squeezing size to initial diameter of wire, is controlled in the range of 40 to 60 percent, the joint strength is obtained more than 0.3 N for Cu composite wire of 50μm in diameter.
