Silicone rubber, or elastomeric, keypads are being introduced in a variety of devices in consumer, medical, industrial, and automotive markets. These silicone rubber keypads are replacing keypads and keyboards based on mechanical switches in part because silicone rubber molding technology allows the manufacturer to easily create custom keypads or individual key shapes. In addition, the durability of modern silicon rubber formulations means that elastomeric keypads have operating lifetimes that now rival those of keyboards manufactured with traditional mechanical switches.

For this application, we were asked to demonstrate the feasibility of marking symbols and text by ablating an existing inked coating. Our marking setup consisted of an FH Flyer marking head, a Synrad 10-watt CO2 laser, and a copy of our WinMark Pro laser marking software. The Flyer head was fitted with a 200 mm focusing lens that provides a 290-micron (0.011”) diameter spot with a 5 mm (0.196”) depth of focus.

We created a 10-character text string in WinMark Pro using “European”, one of WinMark’s twelve built-in stroke fonts. On the Format tab, we set a Text Height of 0.94 mm (0.037”) and added 0.10 mm (0.004”) of Extra Character Spacing. On the Marking tab, we specified three (3) Mark Passes, set Power, duty cycle percentage, equivalent to 25 watts, and set a marking Velocity of 1270 mm per second (50 inches/second).

Using these mark parameters, we were able to mark thin film chip resistors in a cycle time of 100 milliseconds (0.10 sec.) per piece. As shown in the close-up photo, the resulting engraved text is legible with some magnification, but more importantly, it does not penetrate into the Nichrome resistor film layer.