Membrane Switch Construction Type

RIGID BASE CONSTRUCTION:

 

Rigid Based Construction sample

 

Typically utilizes a printed circuit board (pc board) to support switch circuitry, mounting hardware, sub-assemblies and any electronic components.

  1. Etched printed circuit board
    1. Unclad laminate with screen printed shorting pads
  2. Spacer
  3. Membrane
  4. Overlay with or without adhesive
  5. Rear adhesive/insulator (optional)

FILM BASE CONSTRUCTION:

 

Film based construction sample

 

Consists of flexible film layers that will provide a thinner overall package thickness.

  1. Rear adhesive (not shown)
  2. Substrate
  3. Spacer
  4. Membrane
  5. Overlay with or without adhesive
  6. Rigid backer (optional)

OVERLAY

GRAPHICS REQUIREMENTS
  1. Graphics must be applied on a separate layer as an overlay.
  2. Graphics and colors are applied on surface opposite touch surface (second surface printing).
  3. Can be embossed

POLYESTER MATERIAL: Used for graphics overlay.

Type and general information

Gloss

  1. Vivid colors
  2. All types of displays are legible
  3. Good chemical resistivity
  4. Shows fingerprints and, unless hardcoated, is easily scratched
  5. Can be embossed

Matte finish

  1. Colors less vivid than gloss finish
  2. LED display is legible
  3. Non-glare appearance which diminishes seeing cosmetic flaws
  4. Can be embossed

Texture

  1. Fine texture
  2. Heavy texture
  3. Can be embossed

Hardcoated

  1. Provides scratch resistance
  2. Embossing not recommended

Selective texturing

  1. Fine/matte texture
  2. Not recommended for embossing

POLYCARBONATE MATERIAL: Used for graphics overlay.

  1. Type
    1. Gloss
    2. Velvet  texture
    3. Suede texture
  2. General information
    1. Vivid colors with a textured finish
    2. Gloss finish can be selectively textured
    3. Will be affected by chlorinated hydrocarbons and strong alkaline's
    4. Shows scratches
    5. Through textures, displays can be difficult to read unless a special "clear coat" is applied to the front of the filter area.
    6. Hardcoating improves scratch and chemical resistance
    7. Can be embossed, but not recommended with hardcoated or selective textured material.
    8. Special coating for UV protection.

SWITCH CONTACTS

MATERIALS: Used for shorting pad and switch configuration.
  1. Rigid base
    1. PC board is copper plated with electroless tin alloy and/or gold plating
    2. Membrane is silver conductive ink and/or carbon
  2. Film base
    1. Conductive silver
    2. Other conductive inks such as carbon or a silver/carbon blend are available for special applications

SWITCH RESISTANCE (terminal to terminal)

  1. Rigid base
    1. Less than 2 ohms
  2. Film base
    1. Silver ink typically provides less than 100 ohms depending on circuitry layout
    2. Higher resistances available in other conductive inks.

SWITCH/LED LOGIC

TYPES OF SWITCH LOGIC
  1. Both sides out
  2. XY matrix
  3. Switch to common
  4. XY to common
  5. Film base design may require crossover technology
  6. LED logic (when applicable)

TERMINATIONS

RIGID BASE
  1. .025" square pinned stock inserted and trimmed to length
    1. .270 to 1.0 inch long +/-.020
    2. Tin plated
    3. Gold (15 millionths) over nickel
  2. Solder pads
  3. Ribbon cable/Flat flex cable
  4. Header
FILM BASE
  1. An integral single or multiple polyester tail as required by switch matrix and customer interconnects
    1. Typical conductor .100" on centers and .060" wide
    2. .050" minimum from edge of trace to edge of tail
    3. Die cut or notched to meet customer connector requirements
  2. Flex tail terminations (tin or gold plated)
    1. Berg clincher type connectors 65801 series, can be male or female type.
    2. Others such as Nicomatic, Amp, Molex
    3. Housings can be plain, latching or polarized.