Marking PCB's with the 32-1 Laser

Circuit boards, like most components in the modern manufacturing supply-chain, are coded for tracking purposes throughout the process, from raw board creation to final assembly. Common coding solutions for printed circuit boards (PCBs) include laser marking, ink-jet printing, or affixing pre-printed labels. One of the finishing steps in the PCB fabrication process is to apply a solder mask to seal out contaminants. Solder mask, a clear epoxy, can be dyed various colors, with green being the most common circuit board color. Typically using 5-10 W of laser power, the long wavelength, of the CO2 laser, bleaches the green pigment out of the solder mask but does not expose the copper underneath. Exposing and damaging the copper can be problematic for some shorter wavelength lasers.

In a production environment, especially where a larger parent board contains many smaller boards, it is often useful to mark as many individual PCB's as possible before separation into individual boards. This reduces overall processing time, which leads to more efficient throughput. In these cases it is often useful to put a compact laser and scanhead assembly on a small X-Y stage to quickly cover the arrays on the large parent boards. At a fraction over 11 inches (284 mm) long and only 2.8 inches (71 mm) wide, Synrad’s new 32-1 has the smallest laser footprint and is perfect for the compact laser processing systems required for this application. Additionally, at 7 lbs. (3.18 kg) the 32-1 is also very light-weight reducing the weight carrying capacity needed for the X-Y gantry. When paired with a similarly small, fast, and accurate scanhead head, like the ProSeries 1 from Cambridge, high quality marks can be achieved at fast speeds.

Marking PCB Setup
A video of the experimental setup with the 32-1 and ProSeries 1.


In this case, a Cambridge ProSeries 1 marking head with a 10 mm aperture was used. A 3X beam expander was placed between the laser output and the scanhead to expand the beam to 7 mm before entering the scanhead. On the output of the scanhead, a 200 mm focal length lens was equipped giving a focused spot size of around 400 µm. In the Cambridge Scanmaster Designer software, a 4.1 mm QR code was made with 21x21 cells. The "Hatch Style" property was set to "Helix" and a scan velocity of 700 mm/sec was used. A duty cycle equivalent to 6 W output was set. The resulting code was marked on the PCB in 0.43 seconds with nice white contrast and was verified with a handheld Datalogic M8500 scanner.


PCB Mark
The 4.1 mm sized QR code marked on the PCB.



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