FR4 Circuit Board Marking with CO2 Laser Engravers
It is useful to produce marks or codes on printed circuit boards during manufacture to aid in inventory control and tracking. Laser engraving offers advantages over conventional screen-printing, chemical etching or large format printer for these purposes. Specifically, laser engraving can be easily automated, and laser engraving is non-contact, environmentally friendly and utilizes no consumables. Also, the ability to mark either serialized or variable data transmitted in real-time makes laser engraving attractive for PCB manufacturers. This applications note reviews marking of FR4 with a sealed, laser engraver.
The output beam from a Coherent GEM-100 laser operating at 10.6 µm was directed into a galvanometer scanner equipped with a 100-mm focal length lens. The theoretical spot size at the work surface for this configuration is 145 µm. A table was set beneath the scanner to allow material to be positioned in the focal plane of the scan lens.
Alphanumeric and datamatrix marks with good contrast and readability were generated on the sample material. The marks shown here were produced by ablation of the solder mask and are relatively shallow. Deeper marks, in which epoxy is removed all the way down to the glass fibers, can be produced using higher laser engraver power.
