Cryogenic drilling of aluminum-based printed circuit boards: a review and analysis.

An aluminum-based printed circuit board (Al-PCB) is a composite material comprising a copper layer, an insulating layer, and an aluminum base layer. In the drilling of Al-PCBs, exit burrs are formed because of the plastic deformation of the remnant aluminum under high drilling temperatures. In this work, a new method using cryogenic media is suggested to prevent exit burrs in Al-PCB drilling. The effects of cryogenic media, such as cold air, supercritical carbon dioxide solvent (scCO2), and liquid nitrogen (LN2), on the drilling temperature, chip removal, tool wear and exit burr formation were observed and analyzed. The Al-PCB drilling temperature could be effectively reduced when drilling with cold air, scCO2 or LN2. The chip removal and tool wear could be improved when drilling with cold air or LN2. The exit burr formation when drilling with scCO2 or LN2 was greater than that when drilling under cooling and cold air conditions. A cold air matching composite wood backup board (MW-0.5) could effectively control the exit burr formation within 20 μm. This is the first study on the effects of three different cryogenic media on PCB drilling and is expected to provide a good reference for the cryogenic drilling of PCBs. [ABSTRACT FROM AUTHOR]