Direct Marking on FR4 Printed Circuit Board Material

Circuit boards, like most components in the modern manufacturing supply-chain, are bar coded for tracking purposes throughout the process from raw board creation to final assembly. Common bar coding solutions for FR4 printed circuit boards (PCBs) include laser marking, ink-jet printing, or affixing pre-printed labels. In laser marking applications, marks are typically made on a laser-markable label or ink patch to prevent damage to the FR4 substrate because direct laser marking can result in pinholes through to the underlying copper layer.

To solve this problem while eliminating the need to add a label or print an ink patch, Synrad's Applications Lab developed a set of marking parameters that allow direct 2D coding of FR4 circuit board material without introducing pinholes into the copper layer. To accomplish this task, we set up an FH Series marking head with a 125 mm lens that provides a 180-micron (0.007”) spot size with a 3 mm (0.118”) depth of focus.

We marked this 14-character 2D code directly on
FR4 PCB material in 0.26 seconds using 6 watts
of power at a speed of 35 inches per second.

The serialized data in both black anodized
rectangles was marked using 40 watts of power
at a velocity of 2.5 inches per second in an overall cycle time of 23.8 seconds per label.

Cutting Clear Polyester (PETF) Film

Polyethylene terephthalate, more commonly called polyester or PET, is produced in various forms—as a fiber, film or plastic—and is widely found in a variety of products including clothing, beverage bottles, photographic-quality printing film, and food grade packaging.

The two applications described here involve PETF, a semi-crystalline polyester film. Film thickness is measured in mils, where 1 mil equals 0.001 inch or 0.0254 mm. Thin gauge, 1.5 mil material, is flexible enough to serve as a protective coating when laminated over products while thicker gauge films are specified depending on a product’s desired rigidity. In some cases, a polyethylene layer is added to create a polyester/polyethylene laminate.

In our first application (Figure 1), large sheets of 7-mil clear polyester film were cut on an XY table. Our cutting setup consisted of a 50 W Synrad sealed CO2 laser with the beam delivered through a 63.5 mm (2.5”) focusing optic that provides a 100-micron (0.004”) diameter beam with a 1.8 mm (0.07”) depth of focus. We used air, at a pressure of 0.34 bar (5 PSI), as an assist gas. This setup allows us to cut the polyester film at line speeds of 50.8 meters per minute (2000 inches per minute or IPM). The cut edge was clean and burr-free; however, because PETF exhibits exceptional clarity, cut edges sometimes appear “cloudy” due to the deposition of vaporized residue. If this occurs in your application, careful adjustment of fume extraction or the use of secondary cleaning procedures easily eliminates this issue.

Figure 1. This clear sheet of 7-mil polyester
film was cut using 50 W of power at a speed
of 2000 IPM.





Figure 2. An FH Series marking head and
60 W laser was used to cut these 7-mil thick
parts from polyester film in a cycle time of
0.17 seconds per part.

The second application, shown in Figure 2, involves cutting small parts from sheets of 7-mil PETF using an FH Series marking head. The marking head was fitted with a 125 mm focusing lens (180 micron / 0.007” spot) and mounted to a 60 W Synrad CO2 laser. Although the part shape could have been imported into WinMark Pro as a CAD drawing, this object was created entirely in WinMark using WinMark Pro’s ability to draw elliptical as well as circular objects. At a power level of 60 W and a velocity of 762 millimeters per second (30 inches/second or 1800 IPM), parts were cut out at the rate of one every 0.17 seconds.