Membrane Switch Testing

Membrane Testing Gonimeter Instrument

A membrane switch is a low power electrical switch, comprised of silver or graphite impregnated ink, printed and cure bonded to a plastic substrate - polyester being the most common - and assembled with various adhesive layers and finished with a graphic overlay. Major benefits in designing a membrane switch into your product include ease of cleaning, environmental sealing, low profile, and the ability to create a visually attractive interface.

Test methods for membrane switches are performed to evaluate the properties of materials used in the construction of membrane switch or printed electronic assemblies as they are influenced by the absorption and diffusion of moisture and moisture vapor. This is an accelerated environmental test, accomplished by the continuous exposure of the test specimen to high relative humidity at an elevated temperature. Absorption of moisture by many materials results in swelling, which destroys their functional utility, causes loss of physical strength, and changes in other mechanical properties. Insulating materials which absorb moisture may suffer degradation of their electrical properties.

  • Physical changes:
    • Differential contraction or expansion rates or induced strain of dissimilar materials.
    • Cracking of surface coatings.
    • Leaking of sealed compartments.
    • Deformation or fracture of components.
  • Chemical changes:
    • Separation of constituents
    • Failure of chemical agent protection
  • Electrical changes:
    • Changes in electronic and electrical components.
    • Electronic or mechanical failures due to rapid water of condensate formation.

Materials

NTS uses the latest technology and equipment to test membrane switches. Thermo Gravimetric Analysis (TGA) may be used to identify the exact “fingerprint” of a materials. Additional testing is performed to measure the adhesion between the switch layers and to simulate environmental conditions,

Switch Actuation

Membrane Testing - Button Actuator

Specialized equipment operate the switches through millions of actuations to test reliability. Additional tests include switch functional performance, high temperature/humidity attesting and low temperature testing on switch packages.

ASTM Membrane Switch Test Methods

  • F1578 Contact Closure Cycling of a Membrane Switch
  • F1592 Detention Hollow Metal Vision Systems
  • F1598 Test Method to Determine the Effects of Chemical/Solvent Exposure to a Membrane Switch/Graphic Overlay (Spot Test Method)
  • F1661 Test Method for Determining the Contact Bounce Time of a Membrane Switch
  • F1662 Test Method for Verifying the Specified Dielectric Withstand Voltage of a Membrane Switch
  • F1663 Test Method for Determining the Capacitance of a Membrane Switch
  • F1680 Test Method for Determining the Circuit Resistance of a Membrane Switch
  • F1689 Test Method for Determining the Insulation Resistance of a Membrane Switch
  • F1842 Test Method for Determining the Ink or Coating Adhesion on Plastic Substrates for Membrane Switch Applications
  • F1896 Test Method for Determining the Electrical Resistivity of a Printed Conductive Material
  • F1995 Test Method for Determining the Bond Strength of a Surface Mount Device (SMD) on a Membrane Switch by Applying a Shear Force
  • F1996 Test Method for Silver Migration for Membrane Switch Circuitry
  • F1997 Test Method for Determining the Sensitivity (Teasing) of a Tactile Membrane Switch
  • F2073 Test Method for Non-Destructive Short Circuit Testing of a Membrane Switch
  • F2359 Test Method for Determining Color of a Membrane Switch Backlit with a Diffuse Light Source