Laser PCBs

Electrical Design


This week I focused on manufacturing circuit boards using the Trotec Speedy 100 Flexx

This 2-in-1 laser cutter features both a CO2 laser and a fiber laser. The CO2 laser can cut the FR1 substrate, but cannot cut copper - the beam simply reflects, unabsorbed. The fiber laser can cut copper because it is a different wavelength, but has difficulty with the FR1 substrate.

Design Rules

Two traces between pads in the ISP header

The Trotec laser can achieve much smaller feature sizes than the Roland mill can. The native resolution is 1 mil (1 thousandth of an inch), but the smallest I could reliably create was 7 mil trace and space.

Trace and Space Testing

Very small traces (<3 mil) are completely destroyed. Traces up to 5 or 6 mil may look usable, but these often delaminated and/or were prone to breaking. Above 7 mil the traces were great, though without etching correction they end up slightly smaller than designed.

Note: Diagonal Traces

The laser is rastering to cut the traces, so there is pixelation in the resulting product. This shows up readily in traces routed on a diagonal, as shown above.

Edge Routing

PCB outline and Via

The CO2 laser should be capable of routing the board outline or internal edges, but I was not successful in achieving a clean cut. This is most likely due to using double-sided FR1: Once the CO2 laser cuts through the substrate, it may reflect off the other layer of copper. This puts a lot of diffuse heat into the substrate, causing it to burn instead of cut. Insufficient CO2 passes look beautiful but don't cut (see above). Additional passes cause the ugliness below: