Know Your Options

 

CONTACT MATERIAL

The contact materials used will define the life you can expect.

Xymox-Design Specifications
  • Carbon puck elastomer: ≥ 3 million cycles typical
  • Printed carbon elastomer: ≥ 1 million cycles typical
  • Printed silver membrane: ≥ 3 million cycles typical

Typically a carbon or gold/nickel plate over copper is recommended if the circuitry is on a printed circuit board. The carbon will have a higher contact resistance with improved immunity to extremely corrosive environments.

Contact Type                             Resistance (ohms)

Printed carbon elastomer      ≤ 1000

Carbon puck elastomer         ≤ 200

Printed silver membrane        ≤ 10 as a shorting pad
                                                ≤ 100 as a full switch

Recommended Design Pattern:

 
 

LEGENDS

Silk screen legend life will vary depending on key shape, style of the legend, and operating conditions. As a general guideline, a standard printed legend will meet 250,000 to 500,000 finger actuations (as simulated with a rubber test finger) before showing signs of wear.

To increase cycle life, overcoats can be added. This can increase the life to the equivalent of 1 million finger actuations.

Legend colors are typically matched to Pantone Colors with a tolerance of ± 1 shade. There are printing limitations on the distance between the legend and key edge:

  • Silk screen printing: 3mm minimum from key edge
  • Convex surface: 20mm minimum keytop radius
  • Concave surface: 30mm minimum keytop radius

TACTILE

Sharp tactile feel occurs with the right combination of actuation force, stroke, and rubber hardness. Sharp tactile can be obtained with 60 durometer silicone and a long stroke but as these factors are increased, keypad life decreases.

Using a half membrane switch or full membrane switch with a Metal or Poly Dome for tactile feedback, can provide sharp tactile feel while allowing for a lower overall profile than if the elastomer was designed to provide the tactile feedback.

DIMENSIONS

The following dimensions will be required to design a custom rubber keypad:

  • Overall Keypad Length and Width
  • Key to Key Center X and Y Axes
  • Key Height
  • Keytop Length and Width
  • Mat/Base Thickness

ELASTOMERIC KEYPAD STANDARD TOLERANCES

 


Legend Surface Print Tolerances: Inches +/- .012 Millimeters +/- .30