Select the most appropriate construction type to achieve the most cost-effective solution you need:

1. TYPE OF TOUCH:

Membrane switch keypads are manufactured with different types of touch:

1.1 Tactile feel.
Is more appealing to operators because they feel a "response" at their fingertips. So called "metal touch", provided by a metal dome over each contact, offers best touch uniformity and operates within a wide range of temperatures although at a higher cost if the keypad has multiple keys. Domes are supplied in different sizes and actuation pressures. Active surface of each key is limited to 15 mm diameter.

"Bubble touch":
The bubble is embossed on the polyester overlay to offer a comfortable tactile feel. This touch is not recommended when keypad may be exposed to temperatures > 60°C (e.g. direct sunlight).Bubble touch is very cost-effective when keypad has multiple keys and production volume is above 100 units. Additional advantages include aesthetics and easy orientation for the user. Maximum diameter of bubble: 20 mm.
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1.2 Non-tactile feel.
"Flexible touch" keypads should include some acoustic or visual confirmation of contact for the user. These keypads operate within a wide temperature range and have a longer life expectancy than models with tactile feel. Active surface area of each key is almost unlimited.


2. FRONT PANEL MATERIALS

2.1 Polycarbonate: recommended for not very harsh operating conditions. Solvents and chemicals will damage the surface. Embossing offers well defined shapes but is not recommended for very intensive use. Colors look well defined and bright. Available in multiple thicknesses and finishes (gloss and textured).

2.2. Polyester: good resistance to fatigue and chemicals. Ideal for harsh environments and intensive use. Available in multiple thicknesses and textures. Higher cost than polycarbonate

3. EMBOSSING
"Bubble touch" keypads are always embossed. Other types may be embossed on the key, either flat or as a rim, improving aesthetics and facilitate operation. Additionally, a logo or area around the display may be embossed.

4. TRANSPARENCIES

Materials may be surface treated to make them selectively transparent and improve view of underlying display. These windows may be translucent or have transparent colors, matching the display. For good definition, display should be < 5 mm from face plate of keypad.
Same transparencies may also, be positioned over LEDs or other light signals.

5. CONNECTIONS

Internal keypad connections are designed as specified by the customer. Usual configurations include a row and column matrix, common point with independent output, or any combination of the above.

Output is via a flat, flexible, printed cable. Length and position of the cable should be defined by customer. Flat cable may be terminated at printed contacts that insert into a female connector on a printed circuit board (1/10" separation between contacts on flat cable). Optionally, female or male connector may be clamped on flat cable terminal. Connectors may be supplied by MICROTECLADOS.

6. RIGID SUPPORTS

Keypads may be mounted on a rigid support, if required by customer. Metal (aluminum, brass or iron) or plastic (phenolic laminate, acrylic, polycarbonate, etc.) substrates machined as required by customer. Mounting screws and bushings may also be included on request.

7. SLIDE-IN GRAPHICS

When special graphics for each device are required, keypad design may include a slot on the front or back, to insert customized graphics printed by user on a plastic or paper card.

 8. SHIELDING

To minimize interference in environments with "electronic noise", and to avoid electrostatic discharges from operator, membrane switch keypads may have electrostatic shielding.

9. LEDS

Surface mounted LEDs may be assembled inside the keypads. Customer should specify colors and connections. Output contacts may be on the same flat cable as key connections or may have a separate flat cable.

10. HYDRAULIC SEAL

Membrane switch keypad resists humidity quite well, but when water may fall directly on it, a special "hydraulic seal" construction is recommended.

11. BACKLIGHT

Many applications require backlight in the keypads for functional or just decorative purposes. MICROTECLADOS offers different options and it is possible to arrange that different areas or legends in the keypad may be illuminated either permanently or when a key is activated. An important application would be when keypads have to be operated at places with scarce or zero visibility.

One system is based on the inclusion of an electroluminescent (EL) panel in the keypad, which increase the thickness only 0,5 mm. The electrical supply of the EL panel is obtained via a flat cable connected to a special power supply, provided with each keypad. This type of backlight has a limited life of about 4000 hours and therefore is not suitable when the device has to be lighted continuously.