Lasers allow engineers to weld ceramics, no furnace is required

Smartphones that do not scratch or break. Stimulators without metal. Electronics for space and other harsh environments. All of this could be made possible through a new ceramic welding technology developed by a team of engineers from the University of California at San Diego and the University of California Riverside.

The process, published in the August 23 issue of Science, uses a high-speed pulsed laser to fuse ceramic materials along the interface and merge them. It operates under ambient conditions and uses less than 50 watts of laser power, making it more convenient than current ceramic welding methods that require heating the parts in an oven.

Ceramics have been fundamentally difficult to weld together because they require extremely high temperatures to melt, exposing them to extreme temperature gradients that cause cracks, said lead author Javier E. Garay, a professor. mechanical engineering and materials science and engineering at UC San Diego. who led the work in collaboration with Professor UC Riverside and the Chair of Mechanical Engineering Guillermo Aguilar.

Ceramic materials are of great interest because they are biocompatible, extremely hard and burst resistant, making them ideal for biomedical implants and protective wraps for electronics. However, current ceramic welding procedures are not conducive to the manufacture of such devices.

"At the present time, there is no way to wrap or seal the electronic components inside the ceramics because it would have to place the set in one oven, which would eventually burn the electronic components, "said Garay.

The solution of Garay, Aguilar and his colleagues was to guide a series of short laser pulses along the interface between two ceramic pieces so that heat builds up only on the interface and causes localized fusion. They call their method of ultra-fast pulsed laser welding.

For this to work, the researchers had to optimize two aspects: the laser parameters (exposure time, number of laser pulses and pulse duration) and the transparency of the ceramic material. With the right combination, the laser energy is strongly coupled to the ceramic, which allows welding with low laser power (less than 50 watts) at room temperature.

"The ideal limit for high-speed pulses was two picoseconds with a high megahertz repetition rate, with a moderate total number of pulses.This maximized the melt diameter, minimized the number of pulses. ablation of the material and allowed a timed cooling just for the best possible welding, "says Aguilar.

"By concentrating energy where we want it, we avoid creating temperature gradients throughout the ceramic, so we can wrap temperature-sensitive materials without damaging them," Garay said.

To prove the concept, the researchers soldered a transparent cylindrical cap inside a ceramic tube. Tests have shown that the welds are strong enough to resist vacuum.

"The vacuum tests that we used on our solders are the same as those used in the industry to validate the seals of electronic and optoelectronic devices," said first author Elias Penilla, who worked on the project as a postdoctoral researcher in Garay's research group at UC San. Diego.

The process has so far only been used to weld small ceramic pieces smaller than two centimeters in size. Future plans will involve the optimization of the method for larger scales, as well as for different types of materials and geometries.