New glue may spell end for soldering, welding

Scientists have developed a new metallic glue that can bind metal components in different devices at room temperature using very little pressure, an advance that may spell the end for soldering and welding.
The glue can be used in everything from a computer's central processing unit and printed circuit board to the glass and metal filament in a light bulb, researchers said.
"It's like welding or soldering but without the heat," said Hanchen Huang, chair in the Department of Mechanical and Industrial Engineering at Northeastern University in US.
"Both 'metal' and 'glue' are familiar terms to most people, but their combination is new and made possible by unique properties of metallic nanorods - infinitesimally small rods with metal cores that we have coated with the element indium on one side and gallium on the other," researchers said.

These coated rods are arranged along a substrate like angled teeth on a comb - there is a bottom 'comb' and a top 'comb'. Then the 'teeth' are interlaced.
When indium and gallium touch each other, they form a liquid. The metal core of the rods acts to turn that liquid into a solid. The resulting glue provides the strength and thermal and electrical conductance of a metal bond.

Unlike standard polymer glue, the metallic glue can function at high temperatures or high pressures, conduct heat and electricity, and is resistant to air or gas leaks.
"'Hot' processes like soldering and welding can result in metallic connections that are similar to those produced with the metallic glue, but they cost much more," researchers said.

"In addition, the high temperature necessary for these processes has deleterious effects on neighbouring components, such as junctions in semiconductor devices. Such effects can speed up failure and not only increase cost but also prove dangerous to users," they said.
The metallic glue has multiple applications, many of them in the electronics industry. As a heat conductor, it may replace the thermal grease currently being used, and as an electrical conductor, it may replace today's solders.
The study was published in the journal of Advanced Materials and Processes.