U researchers have devised a new technique for cutting conductive materials used in solar power cells that can save company manufacturers thousands of dollars.
Eberhard Bamberg, lead researcher and assistant professor of mechanical engineering, said the original technique doesn’t work as well because one of the materials, an element called germanium, becomes brittle and weak when sliced with a wire saw.
The weakened element is easier to break and wastes time and money spent by manufacturers.
“A crack in metal goes a little bit and stops,” Bamberg said. “But with crystal, the crack can shoot through and a rapid fracture can occur.”
Sylarus Technologies, a manufacturing company in St. George experiencing problems with the weakened material, contacted Bamberg and Dinesh Rakwal, a doctoral student in mechanical engineering, about fixing the problem.
Bamberg said they realized that part of the problem was with the wire saw cutting the material. The germanium is cut into a cylinder and then thin wafers of the material are used for solar power cells.
“(The material) is cut with an abrasive wire saw that creates mechanical stresses when it slices through,” he said.
The two researchers decided to develop a less abrasive technique that does not touch the material with a wire.
Instead, they heat up a wire and send sparks shooting off onto the material. The sparks melt parts of the material off, which is then washed away by a stream of oil projected onto the metal.
Bamberg said they use oil instead of water because the material is a semiconductor, a solid material that conducts electricity and is used on mobile phones, computers and other common devices.
The wire never touches the material, but is slowly lowered down until it slices completely through.
With the new slicing technique, the remaining wafer not only remains free of defects, but more of the material is saved because the wire isn’t taking away as much of it while cutting. Also, the wafers can be cut thinner because the machine surfaces are free of cracks that otherwise would need to be polished out.
Rakwal, who is finishing his doctoral thesis on the research behind the device, said Sylarus and any other company that wants to use the device will save money and waste less material.
The thinner wires used in the new slicing technique are 100 microns and 75 microns in size, which is about twice the thickness of a strand of hair.
Rakwal said if a company uses the 100-micron wire, they will save $8,000 for every 100 wafers they produce. The 75-micron wire will save about $16,000-30,000 per 100 wafers.
Sylarus is one of only two manufacturing companies that produces germanium wafers for solar cells.
The device is intended for germanium wafers, but researchers said it could be used for any semiconductor material. Rakwal is in the process of testing the wire-cutting device on silicon, another semiconductor.
Also, because the metal researchers use for the wire is expensive, Rakwal said they are testing to see if a cheaper metal, like brass, would be as effective.
Bamberg and Rakwal are in the process of patenting the device, but said it will take another three years, if not more, for paperwork to go through.