Significant reduction of wire sweep using Ni plating to realise ultra fine pitch wire bonding

Significant reduction of the wire sweep in molding is proposed because the wire sweep is considered to be the major problem to realise wire bonding with ultra fine pitches of under 30 micrometers. In the present proposal, Ni was plated for several micrometers before molding on bonded Au wires. Ni plating was carried out by means of electroless plating for several minutes in the aqueous solution kept at 358K containing Ni and P. The wire sweep ratio for Ni plated wire (total diameter was 21 micrometers) was almost half of that for Au wire with the diameter of 15 micrometers except Ni plate, and was slightly smaller than that for Au wire with the diameter of 25 micrometers except Ni plate even the total diameter was smaller. It is considered that wire sweep suppression by this technique was due to the enhancement of both elastic and plastic properties.