Shaping cooler solders and smarter materials
Materials scientist Ainissa Ramirez lives for figuring out new ways to control metals and shape them into materials that can be put to practical use — for instance, in the ever-shrinking smart phones. Her research on shape memory alloys — so-called “smart materials” — and on a solder that can be manipulated into place with a magnetic field has kept her busy during her time in Yale’s School of Engineering and Applied Sciences.
“Metals are often overlooked as a field for innovation,” says Ramirez. “These materials are fundamental to things that we use everyday.”
Ramirez is known for discovering a universal solder that can bond metals to ceramics, glass, diamonds and the oxide materials used in semiconductor fabrication. She also developed thin film shape-memory alloys, which have the unique property of “remembering” and reverting back to their original shape.
“My work is in understanding their thin film behavior and integrating them into microelectromechanical systems (or MEMS),” says Ramirez. “We’re now using these materials as a way to move a MEMS device. These materials would help move liquids or blood in medical devices.” The diverse applications for these metals have made them increasingly important and visible to the world, she adds.
Even Ramirez’s side projects are revolutionary; She had a eureka moment while working with a student who needed a project for his senior thesis. “Our main goal was to find a way to strengthen solder, and we ended up with something much greater — a strong, inexpensive material that can replace traditional lead-based solders, which have been banned in many electronic products,” she says. At the time, the most popular lead-free alternative was a tin-silver alloy that is weaker than lead-based solder and doesn’t perform as well.
Ramirez and her student developed a magnetic solder that can be manipulated in three dimensions and selectively heated. The non-toxic solder is made of tin-silver containing iron particles, which makes the solder much stronger. This new material can be melted and then easily and cheaply channeled with a magnet to connect transistors, chips and other components, potentially solving a host of technological challenges.
“Devices such as smart phones are getting smaller and smaller,” notes Ramirez. “The only way to efficiently hold all the information in a smaller space is to stack chips. Having a solder that bonds them and won’t cause the whole circuit board to warp is key.”