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By Sandy Dick | Jul 11, 2017
CONMED membrane switch assembly

CONMED, a global medical technology company, came to GM Nameplate (GMN) in need of a membrane switch for the control panel of their surgical generator. With diverse capabilities and decades of experience working with the medical industry, GMN was able to provide not only each component of the membrane switch, but the complete, value-added assembly of the part as well.

The graphic overlay was printed using a combination of screen and litho printing and included multiple display windows and LED indicators. The overlay’s background colors were screen printed to achieve a high opacity, which helped to prevent light bleed from the illuminated LEDs. Litho printing was used to apply fine details and halftone patterns to the part. A halftone dot pattern was printed on top of the background to create a gradient effect on the keys and along the top of the overlay. Creating a halftone pattern that achieved the customer’s desired aesthetic proved to be challenging, but the ideal look was reached after several trials of testing various pattern constructions (altering dot size and space between the dots). GMN also printed the membrane circuit that goes behind the overlay and connects to the LEDs and switches.

Another challenge faced during this project was choosing the correct snap domes for the different-sized keys to create a good tactile feel. The difficulty stemmed from the unusual shapes of the keys and various sizes of domes. As a consistent layer across the entire part, the spacer interacts simultaneously with every dome and affects each dome size differently. Therefore, GMN had to carefully review the stack-up to include a spacer layer with the optimal thickness to give every dome size enough room to provide a crisp tactile feel.

A variety of layers were required in the stack-up in order to ensure that the part would function properly. ESD shielding was placed under the circuit connector to protect from static discharge and an aluminum subpanel was added to support the otherwise flexible structure. A foam gasket surrounded the outside of the panel to seal the area from outside moisture and fluids. Finally, due to a concern of the closeness to the electrical components beneath the panel, an insulating layer was added to the backside of the subpanel to prevent the electrical components from shorting out against this metal layer.

From early development through full-scale production, GMN worked closely with the customer to develop this product and provide design considerations for part manufacturability. As a product used in the operating room, GMN held multiple pilot runs to ensure the part functioned as intended and met the customer’s standards. 

CONMED surgical generator with GMN's membrane switch assembly.