SemiSerious

Recently, copper appeared in the news as a replacement for traditional gold bonding wires due to the rising price of gold. War and upheaval has a way of attracting investors to gold. Looking at the 30-year history of gold prices, there are spikes in 1979 when the Soviet Red Army invaded Afghanistan as well as in 1982 during the Falkland Islands War. More recently, gold was the only winner following the US invasion of Iraq in 2003.

For obvious reasons, gold has always been viewed as an expensive commodity. Therefore, there were several groups working on more cost-effective alternatives such as copper dating back 30 or more years. Several issues have held copper back. Foremost among these is copper’s tendency to continuously form an oxide. Gold, after all, is the most inert metal there is. To achieve acceptable yields in the bonding, assembly would likely need to move to much cleaner environments than those used for gold today.

No doubt, there are many good engineers out there who could overcome the shortcomings of copper as a wirebond material. Ironically, it is probably cost-effectiveness that will stop it. Gold is more expensive, but it benefits from a 40+ year history on the job. It would take an unprecedented level of extremely costly retooling to get copper into the mainstream. It is hard to imagine even a copper wirebond tool maker getting a machine into production, let alone widespread adoption by assembly houses. Gold will not be displaced by copper, at least not for wires.

What will change in the industry is the decision point for moving a design from wirebond to flipchip. Typically today, flip-chip is not considered to be a viable option below about 200 pins. If gold continues the trend to be a more significant portion of the manufacturing cost, we will see lower I/O count devices avoiding the wirebond route. In this case, copper pillar technology might be used to lower the overall cost of the chip. Solder bumping devices that use copper back-end metallization on the IC require some special additional metals - under-bump metals or UBM - to ensure low resistance die-to-package connection. Therefore, copper pillar technology such as used in the Intel 65nm D 920 Dual Core MPU, might squeeze out the solder bumps usually used today. So copper may still have a future as a cost-saving measure in the packaging industry. 

The crisis in Lebanon seems to have subsided for now, but either way, there is an impact on the markets. The news from Wall Street this time seemed to be that investors have become more hardened to the idea of major crises. This left the Dow Jones relatively stable, and gold prices actually declined slightly.

It’s doubtful that the price of gold represents the end of the world as we know it, and it’s up to you whether you buy or “share” the REM song of that name. But that brings up the whole issue of digital rights management which will have to wait for another day.

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