Underwater laser cutting and silver sintering to make ceramic circuit boards

Thermal stress cracking can be completely avoided by CO2 laser cutting thin alumina sheets underwater. I also show how to formulate and apply silver paste, then sinter in a kiln to produce double-sided ceramic printed circuit boards with conductive vias. 60W CW CO2 laser at 80% power. 10mm/sec. Standard lens focal length (50mm). 2mm water above ceramic. 180 passes to cut through thick alumina. Silver paste: 97% silver powder, 3% glass powder by mass. Particle size 1 micron or less. Add poly vinyl alcohol mold release until desired consistency reached. Paste applied with 4 mil thick vinyl stencil. Dried in air 10 minutes, then rapidly brought up to 900*C, held for 10 minutes, then rapidly brought back down to room temperature. Total cycle about 45 minutes. I measured electrical conductivity of the finished traces from my process with vinyl stencils: 4 milliohms per square at 10 micron final thickness. This is pretty close to the Dupont published spec ( less than 2 milliohm/sq at 16 micron thick) Underwater CO2 laser cutting reference: 60W laser cutter: Ceramic sheets at McMaster: Ceramic PCB prototypes: Quickfire kiln: Raspberry Pi picoReflow oven controller: :resources:picoreflow Silver powder: Glass glaze: Macor: ~glass-mica-ceramic/ Dupont silver paste: Binders for ceramic powder: for ceramic bodies PVA mold release: Very complete study of laser machining of ceramics: Applied Science on Patreon: