With the creeping rise in the price of gold, many microelectronics manufacturing companies have been looking for alternatives to reduce the cost of ball bonding. Recently, the trend has been to look into the use copper wire. However, there are many drawbacks to using copper wire, including the short shelf life of pure copper wire, EFO must occur in a forming gas (N2 + 3H2) adding cost and infrastructure, and Palladium-coated copper wire also adds cost to the wire.
In addition, because copper is harder than gold, bond pad structures must be scrutinized so the bonding does not damage the die. Pure silver wire has been tried as another alternative to gold but is often eliminated as an option due to the phenomenon of silver migration. |
Silver (Ag) Alloyed Wire
On the other hand, there are challenges in using silver alloy wire as well. With the alloys comes added electrical resistance, which is a negative for many applications. Also, silver alloy ball formation cannot be done in room atmosphere (it needs N2 only). There is also the drawback concerning the suitability of silver alloy wire to any given application; for example, it is probably not suitable for use in radio-frequency applications.
Platinum (Pt) Wire
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Palomar Technologies Assembly Services offers a wide range of contract packaging solutions, including gold and platinum wire bonding processes. Also, the 8000 Wire Bonder is currently in use by implantable medical device manufacturers to acheive high-precision, high-reliability Pt wire bonding. Learn more: Platinum Wire Bonding Reliability and Biocompatibility for Implantable Medical Devices
In conclusion, with the rising cost of gold and the drawbacks of using copper wire in some instances, alternate materials such as Ag alloy wire and Pt wire are being researched and tested for certain applications. The 2013 IMAPS Wire Bonding Workshop was another successful event, highlighting many experts and new discoveries in the wire bonding industry.
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David Rasmussen
Assembly Services General Manager
Palomar Technologies, Inc.