SAN FRANCISCO—Texas Instruments Inc. said Wednesday (May 23) it has shipped nearly 6.5 billion analog, embedded processing and wireless chips using copper wire bonding technology, a milestone that the firm says underscores the semiconductor industry's growing confidence in copper packaging technology as a viable replacement for gold.
According to Dave Stepniak, analog packaging development manager at TI, the firm is now at the point where it is buying more copper wire than gold. While the initial reason for transitioning from gold to copper was the rising price of gold, TI has been able to demonstrate that copper wire bonding has reliability, quality and performance advantages over gold, Stepniak said.
"We are seeing customer interest move more to a pull phase," Stepniak said. Even some customers in automotive and safety critical applications have begun to investigate copper, he said. "It's really gaining momentum in that sense," Stepniak said.
According to TI, copper wire delivers 40 percent higher electrical conductivity, decreasing operating resistance and giving customers a performance boost. Copper is also a superior conductor to gold, which reduces heat dissipation within a package, according to Stepniak. Copper also offers more thermal stability and better mechanical properties that increase bond strength and wire loop stability during molding, he said.
But copper wire bonding also requires the use of a forming gas in the during the bonding process to eliminate oxidation until the bonds are made—a requirement that gold bonding does not have. This added requirement was largely responsible for the long ramp up of the technology, Stepniak said.. While TI first began developing copper wire bonding technology in 2003, it didn't use it in production until 2008 and did not pass the 1 billion unit mark with the technology until 2010.
The biggest challenge, Stepniak said, was getting the infrastructure in place to support copper wire bonders. Eventually the firm worked with tool vendors to create a conversion kit that can be used to upgrade wire bonders to add the forming gas capability, he said.
Today, all seven of TI’s assembly and test sites are running copper wire bonding production across a range of products and package types, including quad flat no lead (QFN) packages, ball grid array packages such as nFBGA and PBGA; package-on-package (PoP); QFPs; TQFPs; TSSOPs; SOICs; PDIPs and others, according to TI.
TI's plans for the technology include taking it into production for high reliability applications, which have been slower to make the switch until the technology was proven. TI is also moving die-to-die bonding with copper wire to high volume production for multi-chip and 3-D stacked die packages, Stepniak said.