Last month, Chow and colleagues presented their work at the Electronics Components and Technology Conference in Las Vegas. They showed that their approach works on a test chip from Oracle that simulates the electrical and thermal behavior of a high-end processor. “It’s a test vehicle to evaluate the finished module,” Chow explains. The test chip has nearly 4,000 180-square-micron cells, each containing a thermometer, sensors to measure the power supplied to that part of the chip, and a heater so that the overall chip pumps out the same heat as a high-power processor working at full capacity.
Another reason to think beyond solder, says Chin Lee, a professor of electrical engineering and computer science at the University of California, Irvine, is the fact that it will soon limit the industry’s ability to make ever-smaller devices. “Alternatives are needed, because solder is not going to continue to shrink,” says Chin.
Manufacturers can position the electronic springs more accurately than solder, and this can boost performance, for example by letting them arrange the chips in more compact groups, says Chow. In the race to make faster chips, he says, chip makers can often overlook the ways that components are connected and packaged. “This isn’t a glamorous field,” says Chow. “Everyone focuses on transistors and components, but packaging is a real bottleneck for performance.”
Bahgat Sammakia, director of the Small Scale Systems Integration and Packaging Center at Binghamton University, agrees. “You can have the best technology in the world, but without packaging, you won’t get the best performance from them; it is what enables the creation of the finished systems we are aiming for.”
Sammakia says that although research into novel approaches to packaging chips is valuable, ultimately the market must decide whether a particular solution will work. “You can always solve a problem, but not always in a way that is commercial.”
Jennifer Ernst, PARC’s director of business development, says the project is being directly shaped by what is possible at commercial scale. “Our first priority is to get this into manufacturing,” she says. She notes that the springs are made simply, using just a few layers of metal and standard deposition and etching processes. “We are currently making these at our own fab, but expect the volume to be cost-competitive at commercial scale,” she says.