Designing a membrane switch requires a lot of considerations, and like Goldilocks, it's about finding the perfect fit! The end use of the application and design requirements for fluid ingress prevention will determine what degree of seal should be used to ensure lifetime functionality. If liquid seeps into the switch it could erode the circuit and cause a field failure.A standard filler piece in the tail area will provide sufficient protection from occasional spraying or splashing for most membrane switch applications, that do not need protection from immersion or very wet conditions. As the amount of fluid exposure increases, so should the consideration on the degree of sealing.
For products used in harsh environments with a high risk of exposure to liquids (rain, chemicals, cleansers, humidity, etc.), there are 2 options: perimeter gasket or XyWeld®.Perimeter gaskets have been proven very effective in preventing fluid ingress. This is a cost effective solution for outdoor applications, however, the design must allow for the gasket to have a minimum width of 0.125". If the part has components running right up to the edge of the part, the gasket won't be thick enough to ensure a quality seal for the lifetime of the product. Gaskets are most commonly used when the tail is not internal (for example, if the tail comes out of a tail slot in a bezel), this seals the tail slot completely. However, if the tail is internal to the part, XyWeld® is the most effective solution. The Xymox XyWeld® spacer involves a specialty adhesive bonded with a proprietary heat activated process to yield a spacer that is much more robust than a standard pressure sensitive adhesive (PSA).