Researchers at the University of Chicago have reportedly developed compounds of cadmium, lead, and bismuth that can be applied as a liquid or paste to join two semiconductors or semiconductor pieces by heating them to several hundred degrees Celsius. After application as a liquid or paste, the materials decompose to form a seamless joint that delivers good electronic performance.
“We worked out new chemistry for a broad class of compositions relevant to technologically important semiconductors,” said Dmitri Talapin, a professor in chemistry. “Our paste and our liquid convert cleanly into a material that will be compositionally matched to the bonded parts, and that required development of new chemistry. We had to design special molecules that fulfill this requirement so that they do not contaminate the material.”
Printable electronics requires assembly of semiconductors from small pieces, putting tiny grains together like Legos. “It’s like additive manufacturing, when you add things and build from pieces,” Prof. Talapin says. “If you want to assemble pieces, you need a solder or glue or connectors.”
Semiconductor soldering is unlikely to have a major impact on today’s mainstream silicon technology, but could lead to the development of less expensive, solution-processed semiconductors needed for entry into new markets. Among these markets are printable electronics, 3-D printing, flat panel display manufacturing solar cells and thermoelectric heat-to electricity generators for the Internet of Things (IoT).
A tiny transistor operates each pixel in current-generation flat-screen televisions. These transistors currently are manufactured via vacuum methods, but industry experts expect that to change to printing and other less expensive solution-based manufacturing techniques.
Prof. Talapin and his associates from UChicago, Argonne National Laboratory, and the Illinois Institute of Technology published their findings in the Jan. 23, 2014, issue of Science.
