ASTM F1681-14

4.1 Current carrying capacity is used by designers and manufacturers of electronic interface circuitry to ensure that the membrane switch can reliably handle the loads occurring in normal use and under extreme circumstances. A thorough understanding of CCC allows manufacturers to take it into account when developing design rules for membrane switches.

4.2 Failures due to exceeding the CCC of a circuit may take the form of a significant change in conductor resistance, insulation breakdown (shorts), or conductor breakdown (opens).

4.3 Since a number of design parameters, such as trace width, ink film thickness, and heat transfer (mounting substrates, active cooling such as fans) affect the final test results, any conclusions should only be applied to specific designs, rather than to a general combination of materials.

4.4 Current carrying capacity tests may be destructive and units that have been tested should be considered unreliable for future use.

4.5 Current carrying capacity may be significantly different for static loads and dynamic (that is, cycling) loads. Failure modes are also generally different.

4.6 The use of a thermocouple to monitor the temperature of the UUT may be helpful to monitor the progress of the test.

4.7 Initial expected starting current should be calculated in advance to prevent damage to test equipment.

1.1 This test method covers the determination of the current carrying capacity of a conductor as part of a membrane switch.

1.2 This test method may be used to test a circuit to destruction, that is, to determine its maximum current carrying capacity, or it may be used to test the ability of a circuit to withstand a desired current level.

1.3 This test method applies only to static conditions, and does not apply to contact closure cycling of a membrane switch under current load (test method forthcoming).

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.