'Cold welding' adhesive is conductive and heat resistant
10 January 2016
US researchers have developed a 'nanorod' based glue that binds a variety of substrates, sets at room temperature and requires little pressure to seal.
The start-up, MesoGlue was founded by Northeastern university’s Professor Hanchen Huang and two of his PhD students. They believed there was a better way to stick things together - things such as a computer’s central processing unit and a printed circuit board, to the glass and metal filament in a light bulb.
The way of attaching them is a 'glue' made from metal that sets at room temperature and requires very little pressure to seal. “It’s like welding or soldering but without the heat,” says Professor Huang.
"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," Professor Huang explains.
"These coated rods are arranged along a substrate like angled teeth on a comb: there is a bottom ‘comb’ and a top ‘comb.’ We then interlace the ‘teeth’. 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/?electrical conductance of a metal bond.”
Professor Huang says that while standard polymer glue does not function at high temperatures or high pressures, his metallic glue does. The standard glue is not a great conductor of heat and/?or electricity, but the metallic glue is. Furthermore, the standard glue is not very resistant to air or gas leaks, but the metallic glue is.
“‘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, Professor Huang adds. "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.”
MesoGlue's metallic glue has a variety of 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. Particular products include solar cells, pipe fittings, and components for computers and mobile devices.”
A paper describing this work is published in the January 2016 edition of the journal, Advanced Materials & Processes.