1. FPC membrane switch:
FPC includes 1 mil up and bottom PI, 1 oz pressed copper foil and 1.5 mil immersion gold. Usual thickness is 0.135 mm.
FPC is better than silver circuitry. FPC can resist high temperature of 280 degrees and it’s resistance is low, only 20% of silver circuitry’s resistance; furthermore, LED soldered on FPC is more reliable than that glued on silver circuitry. Therefore, If there are many LEDs, environment’s temperature is high, or tail is very long, we can use FPC as below circuitry.
2. PCB membrane switch:
FR4 is from famous “Kingboard”, 1 oz pressed copper foil and 1.5 mil immersion gold. Usual thickness is 1.0 mm.