January 9, 2016

Researchers’ metallic glue may stick it to soldering and welding

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.
From “Advanced Mate­rials & Processes,” Jan­uary 2016

(January 9, 2016)  Perhaps no startup was launched for a more intriguing reason than that of Northeastern’s Hanchen Huang. From the company website:

“MesoGlue was founded by Huang and two of his PhD students: They had a dream of a better way of sticking things together.”

Those “things” are everything from 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, astonishingly, 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, who is pro­fessor and chair in the Department of Mechanical and Industrial Engineering.

In a new paper, published in the January issue of Advanced Materials & Processes, Huang and colleagues, including Northeastern doctoral student Paul Elliott, describe their latest advances in the glue’s development. Our curiosity was piqued: Soldering with no heat? We asked Huang to elaborate.

On new developments in the composition of the metallic glue:

“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 galium on the other. 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 galium 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. We recently received a new provisional patent for this development through Northeastern University.”

A schematic illus­trating appli­ca­tions of metallic glue:
a) A CPU on a printed cir­cuit board con­nected to a heat sink.
b) A sur­face mount device being attached to a printed cir­cuit board.
c) A press-​​fit pipe fit­ting for environments where welding is dangerous or impossible.
d) A glass plate being attached to metal with a different thermal-​​expansion coefficient to cover
a cavity with a hermetic seal.
From “Advanced Materials & Processes,” Jan­uary 2016

On the special properties of the metallic glue:

“The stan­dard polymer glue does not func­tion at high tem­per­a­tures or high pres­sures, but the 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. In addi­tion, the high tem­per­a­ture 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.”

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