membrane switch panel

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By Steve Baker | Jun 16, 2017
GMN's membrane switch assembly for Welch Allyn.

GM Nameplate’s (GMN) Singapore Division supported Welch Allyn, a medical company, to develop and manufacture a membrane switch panel with backlit indicators for their resting electrocardiogram (ECG) device. As a device used to test a patient’s heart activity, it is critical that the backlighting appropriately indicates how much battery power the device possesses.

GMN offers an array of backlighting options including discrete LEDs, fiber optic weave, light guide film, and electroluminescence. The part had strict spacing requirements between its tactile buttons, which influenced GMN to choose discrete LEDs. Discrete LEDs are cost-effective and ideal for lighting up small indicators.

Instead of using three different colored LEDs, GMN installed one bi-color LED to occupy as little space as possible and reduce costs. The two colors within the LED were green to indicate the battery was charged, and red to indicate the battery was dead. To create the amber color that indicates when the device needs charging, the LED was positioned off-centered from the indicator window to effectively blend the red and green colors together.

Another factor GMN had to consider was the material for the overlay. GMN utilized polyester (PET) film, a common overlay material for devices in the medical industry due to its resistance to abrasion and harsh chemicals. As an extremely durable, long-lasting material, PET film is ideal for applications with tactile switches because it’s abnormal for the material to crack. 

By Brian Rowe | Oct 12, 2016
Membrane switch panel for  Given Imaging's medical device.

Given Imaging, a medical technology company, came to GM Nameplate (GMN) to assemble a membrane switch panel for their medical device. When configuring a membrane switch, many factors about each component layer must be taken into consideration. 

As the user interface for a medical device, the screen printed and embossed overlay needed to satisfy stringent requirements. The overlay must act as a sealant to prevent moisture and fluids from reaching the membrane. Additionally, the overlay must be chemical and scratch resistant to combat the strain of daily use. 

Common overlay materials include polyester and polycarbonate. Both materials are affordable options that will protect the circuit membrane from scratches, chemicals, and liquids. Due to the durability of screen printed inks, backprinting is a frequent practice to mitigate product wear and tear from everyday use.    

This Given Imaging overlay contains three colors - teal, white, and a black opaque layer. The opaquing layer was selectively applied around the LEDs which allowed light to shine through and prevented light bleed through unwanted areas of the overlay. Because of the opaquing layer, light only showed through the indicator icon on a button instead of throughout the whole part.

When looking at membrane circuit materials, printed silver ink in lower volumes provides a cheaper option than copper etched circuits, such as Kapton, while still offering comparable performance capabilities. Finding the right membrane circuit for the product application is necessary to manufacture a quality membrane switch.

For more information about GMN’s membrane switch assemblies, visit our capabilities page.