At the University of California San Diego and University of California Riverside, a team of researchers has developed a new ceramic welding technology that could bring revolution in electronics for hostile environment, smartphones, and even pacemakers.
The paper published in the Aug. 23 issue of Science, reveals that the process uses an accelerated pulsed laser to soften ceramic materials along the interface and merge them. The conventional ceramic welding methods demands heating the parts in a furnace. The new process uses less than 50 watts of laser power and works in ambient surroundings.
According to senior author Javier E. Garay, ceramics are difficult to work with as they require extremely high temperatures to dissolve, exposing them to high-temperature gradients that cause cracking. Garay is professor of mechanical engineering and material science and engineering at UC San Diego. He also led the work in cooperation with Guillermo Aguilar, UC Riverside professor and chair of mechanical engineering.
Ceramic materials are tough, shatter-resistant and biocompatible, which make them valuable and perfect for protective casings for electronics and biomedical implants. But the welding procedures for ceramics are not favorable for making such devices.
According to Garay, till now there is no process to seal or enclose electronic components inside ceramics as the entire assembly has to be put in a furnace which would end up burning the electronics.
The researchers’ target was to aim a chain of short laser pulses alongside the interface between two ceramic parts so that heat forms only at the interface and causes restricted melting. They termed their method “ultrafast pulsed laser welding.”
For this purpose, the researchers had to improve two aspects: the transparency of the ceramic material and the laser parameters which include exposure time, number of laser pulses, and duration of pulses. Together with the right combination, the laser energy pairs firmly to the ceramic, letting welds to be made using low laser power of less than 50 watts at room temperature.
“The exact time of ultrafast pulses was two picoseconds at the high repetition rate of one megahertz, along with a moderate total number of pulses. This enhanced the melt diameter, reduced material ablation, and timed cooling just right for the best weld possible,” Aguilar said.
“By focusing the energy where we want it, we avoid setting up temperature gradients throughout the ceramic, so we can enclose temperature-sensitive materials without damaging them,” added Garay.
To prove their research, the engineers fused a transparent cylindrical cap to the inside of a ceramic tube. Experiments showed that the welds are tough enough to hold vacuum.
The vacuum tests in the experiments are the same tests used commercially to validate seals on electronic and optoelectronic devices, told first author Elias Penilla, who worked as a postdoctoral researcher on the project in Garay’s research group at UC San Diego.
Until now, the process is used on a small scale that is to say only to weld tiny ceramic parts that are less than two centimeters in size. In the future, efforts would be made to optimize the method for larger scales and for different types of geometries and materials.