1992 Volume 10 Issue 1 Pages 150-154
The temperature and behaviour of Sn, Ag, and Cu at the interface of the bond are shown experimentally at bonding of the copper lead and Ag/Pd thick film on the 96% alumina substrate in the micro parallel gap bonding processes.
The temperature at the interface of the bond can be measured by measuring thermal electromotive force between the copper lead and thick film using probes at the instant of the bonding current reaching zero after switching off.
Increasing input power and current duration, the interface temperature at the bond is increased from 420 k to 830 k, and furthermore, its temperature increases rapidly with current duration and becomes more unstable with increasing power input.
The interface temperature increases with current duration under bonding condition of 300-500 W, 1-4.99 ms, and 23.3 N. Sn can diffuse very rapidly into Cu lead and thick film in the case of interface temperature being above melting point of tin. At same time, Ag and Cu are diffused to tin liquids, and so the intermetallic layers of Ag-Sn-Cu near the interface of the bond are formed. Furthermore it is observed that the fillet of Sn is made at edge of bond.
