Connector Pin Out Sequence: Melrose produces membrane switches with both row & column matrix, or common ground circuit layouts. Customers should consider allowing Melrose to determine the pin out sequence if the sequence is unimportant to the customer’s design. With this approach a superior design (e.g., lower cost, more reliable, shorter lead time) may result if Melrose is allowed the freedom to design the circuit, and pin outs so the circuit design is as straightforward as possible.

Tail Length & Exit Positioning: Membrane switches are connected to the customer’s printed circuit board by means of a flat cable. The flat cable is cut from the circuit layer(s) of the switch. The tail exit position and tail length must be specified before Melrose can begin design of the switch. In volume production tail length, and exit position can substantially affect productions costs. Melrose can advise you when a change in tail exit position or tail length results in a significan effect on cost.

Multilayer Circuits: Multilayer membrane switches circuits can be designed as screen printed conductive inks on heat stabilized polyester (typically .005”), or with circuit boards. With screen printing technology, multiple circuit layers are created (if necessary to achieve needed trace routing) with dielectric insulating ink printed in areas where circuits cross over one another. With flexible or rigid printed circuit boards feed throughs are used to: create multiple circuit layers, as well as to produce two sided circuits.

LED's. Membrane switches from Melrose can be supplied with single or bi-color LED’s. Standard single color LED’s available from Melrose are red, yellow, orange and green (Specifications). Bi color LED’s are readily available as red/green, yellow/green, and red/yellow. (Specifications) Other single or multi color led’s are available by special order.

Light emitting diodes are typically assembled to a circuit layer that lies below the static layer that carries the key functionality due to vertical height issues and space constraints. The tail from the upper layer provides the key interface, while a second tail from the lower layer supplies power for the LED’s.

In some cases Melrose can include light emitting diodes and key functionality on the same layer, and through the same connector, thereby eliminating the cost of the second circuit layer, and connector. (typically requires an overlay embossed in the led area to provide needed vertical clearance for the led’s)

Membrane Switch Use Considerations. If properly designed and manufactured membrane switches are very reliable system components. To achieve maximum reliability, membrane switch users should:

Avoid creasing the switch tail as this can result in broken circuits or high loop resistance. Tails should not be bent around a radius of less than .020”. If desired Melrose can supply the membrane switch with a preformed radius.

Keep the switches in a flat condition prior to and during installation. Bending the membrane switch backwards in a dome area can result in dome failure or unseating of domes from their nominal position. If membrane switches are bent in areas where LED’s are placed, the LED’s may become detached from the circuit.

Membrane switches should be applied to clean, dry, oil free surfaces . Maximum adhesive bond strength is not achieved until approximately 72 hour after application. Of course specifying the proper adhesive for the applied surface, and environmental conditions is essential. Melrose can assist you in selecting the proper adhesive. This link will take you to more information on adhesives.