A medical device company required their membrane switch to pass very stringent electrostatic discharge (ESD) testing; the device needed to withstand 15kV of charge at any given time. While this is an extreme level, many medical devices require some sort of ESD shielding to meet FDA, UL, or other requirements.
The customer also had a unique backlighting challenge. Most backlit products are designed for use in settings with low or no light, but this particular product needed all LEDs to be visible in a well-lit room. Additionally, at the top of the device, an 8”x3” light bar needed to include three color LEDs – red, green, and blue – so the user could easily tell the status of the device.
To solve this customer’s ESD challenges, JN White® engineered a brand new shielding concept. JN White® started with a three-layer etched copper flex circuit and sandwiched the sensitive circuitry between two layers of grid shields. Stitching around the perimeter of the three layers using thru-hole vias connects the top shield and the bottom shield together. The grid shields encompass the electrical components and safely protect them from any discharge a user may expel. Essentially, this created a Faraday cage to protect all the active circuitry. JN White® also added an ESD diode at each LED component of the circuit, which protects the sensitive LEDs inside the ESD cage.
Backlighting required more creative thinking from the JN White® team. First, side firing LEDs or right angle LEDs, were used to shoot light into the button areas, and then silicone discs were incorporated to evenly disperse the light across the buttons. The same concept was applied in the long light bar by creating a custom etched acrylic diffuser, which succeeded in evenly dispersing the LED light across the entire length of the bar. Both custom applications were successful in achieving LED visibility in a well-lit room.
Before JN White® stepped in, this customer had worked with a vendor that was able to achieve the backlighting requirements but was not able to solve the ESD challenge. Once this customer began working with JN White®, the engineering teams from both firms began collaborating to develop a solution. The result is a backlighting design with custom silicone discs and acrylic diffusers that allow for LEDs to be evenly dispersed and visible in a well-lit room, and an ESD design that protects circuitry and components for repeated and long-term use.
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