HOME > R&D > Metal Dome > Metal Dome Reliability Test Criteria  
 
 
   
 
  Trip Force
  Equipment : Switch Feeling Tester made by Aikoh Engineering
  Model : 1350N with 1015A
  Plunger Diameter : 1.6mm diameter full round steel
 
   
  Setup Conditions
   

1.

2.

 The center of dome shall be positioned perpendicular to the plunger within 0.200mm of the center

The dome shall be set on a hard flat surface and to be vented avoiding air entrapment, which is
likely to increase trip force, causing a false reading.
   
  Measuring Procedures
    1.
2.
3.

4. 		Precondition the dome by 10 or more actuations.
Gradually press the dome until it trips and records the trip force reading.
Gradually release the pressure until it snaps back to its original shape when the reading represents the release force that is one of the factors identifying dome's features.
Repeat the above test twice in succession and record the second reading.
   
  Lifetime Test
  Equipment : Dome Durability Tester
  Plunger Diameter : 2.0mm diameter silicon plunger with flat bottom
  Plunger Handness : 100 durometer or more hardness
   
  Setup Conditions
    1.
2.

3.
4. 		The center of dome shall be positioned perpendicular to the plunger within 0.200mm of the center
The dome shall be fixed on the hard flat surface by means of plastic tape with press sensitive
adhesive and vented by preconditioning.
Actuation Load : 300g/ 600g / 1,300g
Speed : Approximately 2 cycles per sec.
   
  Measuring
    The test shall be run continuously at the speed of approximately 2 cycles per second and the dome
status is checked every 100K cycles by measuring the following factors featuring the dome's status.
    Compression Peak Point (CP) : The maximum load reading taken at the point of time the dome snaps
    Compression Low Point (CL) : The minimum load reading taken at the point of time the dome's inside
touches the flat bottom.
    Release Peak Point ( RP ) : The maximum load reading taken at the point of time the domesnaps
back.
    Release Low Point (RL) : The minimum load reading taken at the point of time the dome's inside
comes off the flat bottom.
    - Stroke : The displacement value read at the point of time the dome's inside touches the flat bottom.
    - Click Rate : The close-to-open ratio that comes out by the formula (CP-RL) / CP * 100 is desirably
around 50%.
 
 
 
   
  Failure Criteria
  The dome, when its trip force or other factors drop significantly by more than 20% of the specified criteria,
no longer exhibiting crisp tactile feedback, is considered to have failed.