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Copper wire bonding is becoming popular on multi chip (MCM) device in parallel with the general industry trend of integrating more functions into single product. In order to support device to device interconnect; bond stitch on ball (BSOB) bonding method is quite generally used in the industry. However, copper wire due to its material hardness is more difficult to be manufactured into BSOB as compared to gold wire. In this paper, key challenges for copper wire bond BSOB and its solutions are discussed. Problem solving methodology including copper material selection, bonding tool (capillary) design, bonding concept and special wire bond software features will be explored to develop robust process window for copper wire bonding with good reliability and production worthy.

In recent years, copper wire has been widely proliferated into mass production. However, the hardness of copper wire requires higher ultrasonic power and bonding force, which lead to higher risk of bond pad crack, in order to avoid bond pad crack without re-engineering the bond pad, silver alloy wire is proposed as an alternative to cu wire bonding due to its softer material property.In this paper, the authors researched into process development of silver alloy wire, including fine tuning of material properties, wire bond and assembly process optimization, and reliability assessment.

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