Metallic Glue May Replace Soldering/Welding

Northeastern University, Boston, MA

Northeastern University’s Hanchen Huang, a professor and chair of the Department of Mechanical and Industrial Engineering, and two of his PhD students say they have come up with a better way of sticking things together.

Fig. 1 – a) Coated rods are arranged along a substrate, like angled teeth on a comb. b) The teeth are then interlaced. c) When indium and galium come into contact, they form a liquid. d) The metal core of the rods turns that liquid into a solid. The resulting glue provides the strength and thermal/electrical conductance of a metal bond.

What type of things? Why, everything from a computer’s central processing unit and a printed circuit board to the glass and metal filament in a light bulb. They say that they have created a glue made out of metal that sets at room temperature and requires very little pressure to seal.

“It’s like welding or soldering but without the heat,” says Huang. Their research, published in the journal, Advanced Materials & Processes, describes the team’s latest advances in the glue’s development.

How It Works

The combination metallic glue is made possible by unique properties of metallic nanorods—tiny rods with metal cores that the team coated with the element indium on one side and galium on the other. The coated rods are arranged along a substrate like angled teeth on a comb.

Huang explains: “There is a bottom ‘comb’ and a top ‘comb.’ We then interlace the ‘teeth.’ When the indium and galium touch each other, they form a liquid. The metal core of the rods reacts to turn that liquid into a solid. The resulting glue provides the strength and thermal/electrical conductance of a metal bond.” (See Figure 1)

A standard polymer glue does not function at high temperatures or high pressures, but the metallic glue does. In addition, the metallic glue is a great conductor of heat and/or electricity, while the standard glue is not. And, metallic glue is very 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. In addition, the high tempera ¬ture necessary for these processes has deleterious effects on neighboring components, such as junctions in semiconductor devices. Such effects can speed up failure and not only increase cost but also prove dangerous to users,” says Huang.

The new metallic glue has multiple potential 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 some day replace solders. The team recently received a new provisional patent for this development through Northeastern University.

For more information, visit www.northeastern.edu/news .