WHAT ARE PCB MEMBRANE SWITCHES?
PCB membrane switches combine all membrane switch technologies in one device. A PCB membrane switch can be a support panel for the membrane overlay or supply the electrical pathways.
PCB stands for “printed circuit board” and is typically made of copper clad cloth or fiber material infused a resin material. FR-4 is by far the most common material used today. The board with copper on it is called "copper-clad laminate.” The cloth or fiber material used, resin material, and the cloth-to-resin ratio determines the laminate's type designation (FR-4, CEM-1, G-10, etc.) and as a result, the characteristics of the laminate are produced. An acid resistant mask is screen printed on the copper clad and the exposed sections are etched away using acid. The exposed copper pathways are plated with various metals to protect the copper from corrosion. Gold plating is required on many PCBs in critical applications, such as air bag switches for the automotive industry.
FLEX MEMBRANE SWITCHES
Flex membrane switches are a close relative of the PCB membrane switch. Flex membrane switches use thin dielectric materials in place of the fiber material inner layer. One advantage of this technology is the ability to die cut parts which reduces cost on parts and tooling. Flex membrane switches will require a support panel similar to that of a silver circuit membrane switch.
Both PCB and flex membrane switches have several advantages over a silver printed circuit, but generally at a higher cost. The advantages over silver circuits are:
- Lower electrical resistance/higher conductivity.
- Hard soldering vs. epoxy silver paste to attach components.
- Soldering many components types using automated equipment.
- Finer pitch possible.
- Plating options, e.g., gold.
- Can be used in extreme environments.
The array of components that can be soldered to a PCB membrane is vast indeed. These components include, but are not limited to LEDs, resistors, connectors, both SMT and though hole, LCD and LED displays, and speakers. The addition of a daughter board can add even more design flexibility and can connect directly to the PCB membrane switch.