PCB Membrane Switches
What are PCB Membrane Switches?
A PCB (or printed circuit board), is typically made of copper-clad cloth or fiber infused into a resin material. The cloth/fiber used, along with the resin material, creates a cloth-to-resin ratio to determine the laminate’s type designation (FR-4, CEM-1, G-10, etc.). FR-4 is the most common material used today.
An acid-resistant solder mask is applied to the copper-clad PCB, and the exposed areas (not covered by the solder mask) are etched away using acid. The exposed copper pathways are plated with various metals to protect the copper from corrosion. Gold plating is often required on many PCBs in critical applications where corrosion and exposure to chemicals is an issue.
The PCB Membrane Switch construction utilizes a PCB (as described above) as the main structure/support substrate, with the membrane switch on the front of the PCB assembly, and the display (along with the other discrete components) on the back side of the PCB.
The variety of discrete components can include, but is not limited to LEDs, resistors, connectors (both SMT and though-hole), LCD and LED displays, sensors, and speakers. The addition of a daughter board can add even more design flexibility and can connect directly to the PCB membrane switch.
What are the Advantages of PCB Membrane Switches?
Although PCB Membrane Switches are generally more costly than Silver Flex Membrane Switches, they enjoy several advantages over Silver Flex switches:
- Lower electrical resistance/higher conductivity.
- Hard soldering components on a PCB is a more robust method to attach components vs. epoxy silver paste.
- Soldering many component types using automated pick-and-place equipment.
- Ideal for smaller designs where dense circuit patterns or trace routing limitations exist, by using plated thru-hole technology to utilize both sides of the PCB.
- Plating options such as gold, tin-lead, and nickel.
- Can be used in extreme environments, and high-reliability/high-vibration environments.
What are the PCB Membrane Switch Design Options & Considerations?
- Single-sided, double-sided, and multi-layer designs available
- Tight trace routing capabilities
- Plating options can be tin-lead, nickel, or gold
- Tactile and non-tactile with either metal or polyester tactile domes
- Pillow or rim-embossed graphic overlays
- LEDs and other components can be soldered and are more robust
- Graphic overlays that can be digitally printed, screen printed, or a combination of both
- The graphic overlays can incorporate transparent and tinted display windows, as well as selective textures and UV hardcoat surface finishes