Gold price makes wirebonder maker consider copper

LONDON — Kulicke & Soffa Industries Inc. (Fort Washington, Pa.), a maker of wirebonding equipment, is working with customers to evaluate copper wire bonding and to compare the results to wire bonding with gold, the traditional material, the company revealed in its third fiscal quarter financial results.

With gold costing more than $600 per ounce, and having followed an exponential curve to double in price in the last four years, it is no surprise that packaging companies are considering lower cost alternatives.

Copper has the attraction that it is trading at about $3.50 per pound weight or a matter of a few cents per ounce.

Customers are reviewing the feasibility of a lower-cost copper process with respect to throughput, yield and reliability, K&S said in its results statement.

Copper has been used in packaging in the past, for example for lead-frames, but the inert and highly ductile gold is the conventional material for wirebonds, the miniature wires that link the IC pads or bumps on the surface of an integrated circuit to connections to the pins or balls that project outside the component packaging.

"A transition to IC packages containing copper wire would be a significant change from existing gold wire packaging, and would require complete reliability testing and end-use qualification prior to production," said K&S in a press notice on its financial results.

K&S did not give an indication of how long the company expected the copper wirebonding evaluation to take. Nor did the company indicate whether it would be able to adapt its automatic ball or wedge bonders to the use of copper, or whether it would need to develop a new machine for copper wirebonding.