Flexible Membrane Keyboard

As the name suggests, these keyboard are made entirely of membranes (polyester materials). The circuit is screen printed on a polyester sheet (200 microns) and the snap dome switches are assembled on the same. The graphics are also screen printed on a polyester sheet and the these 2 layers are stuck together using adhesives from 3M, Avery Dennison, etc. The tracks are terminated through a flexible tail with a connector crimped at the other end. Silver Alloy paste is used to screen print the keypad circuit. Considering that plated through holes cannot be achieved in these layers, membrane keypad circuits are generally simple layouts. Further, components cannot be assembled on these circuits as these cannot be soldered on the polyester layer. Since the circuit is screen printed, the overall life of the keypad is quite relatively quite less – less than 50K operations. Hence these keypads are not used in harsh environments or critical applications.