Though the trend is moving away from gold wire for high-volume production wire bonding, gold ball wire bonding still makes up about 50 percent of all wire interconnects worldwide (15 trillion total wire bond interconnects were made in 2013). The adoption of copper wire (pure copper and palladium-coated copper), which grew from about 10 percent three years ago to about 50 percent today, will likely continue to about 80 percent in 2017. Gold, however, will likely then stabilize at about 15 percent of the overall wire bond interconnects.
There are also significant infrastructure requirements at facilities that make the transition to copper ball bonding. Forming gas (5% Hydrogen, 95% Nitrogen) is recommended, even with palladium-coated copper wire, for the best ball formation. Pure nitrogen is usable during flame-off, but the grain structure of the resulting ball is not as good as with forming gas. The palladium is also better distributed through the ball with the use of forming gas. The facility modifications alone to support plumbed forming gas can exceed a million dollars.
Therefore, there is little incentive for many industries to make the switch to copper. The economic payback does not justify the additional costs involved. This is especially true with the current price of gold retreating back to the $1,250 per ounce range from its high of about $1,900 per ounce. Though the price of gold is still over 5,000 times the price of copper ($3.30 per pound), the price of gold bonding wire is only 3-4 times the price of copper wire.
Palomar Technologies Assembly Services offers a wide range of contract packaging solutions, including gold wire bonding processes. In addition, the 8000i Wire Bonder uses a unique bond-head motion (patented dual Z-axis with linear rotary motion) to form precise gold ball bumps by repeatable, smooth shearing of the wire off the top of the bump without leaving a tail. The "tailless bump" option, a patented technology allowing the formation of ball bumps without tails, makes the 8000i Wire Bonder ideal for "flip chip" technologies and other advanced electronic production technologies.
Assembly Services General Manager
Palomar Technologies, Inc.