The base material of the circuit should be made of polyester (polyethylene phthalate) film (Polyester referred to as PET). It has good insulation and heat resistance, high mechanical strength, transparency and air tightness, especially bending resistance and high elasticity. It is an ideal material for making membrane keyboard circuits.
1. Flexible membrane keyboard
Flexible membrane keyboard is a typical form of membrane keyboard. The reason why this kind of membrane keyboard is called flexible is that the mask layer, isolation layer, and circuit layer of the membrane keyboard are all composed of software films with different properties. The circuit layer of the flexible membrane keyboard uses polyester film (PET) with good electrical properties as the carrier of the switch circuit pattern. Due to the influence of the properties of the polyester film, the film keyboard has good insulation, heat resistance, flexural resistance and high resilience. The graphics of the switch circuit, including the switch connection and its lead wires, are printed with low-resistance, conductive paint that cures under low-temperature conditions. Therefore, the composition of the entire membrane keyboard has a certain degree of flexibility, which is not only suitable for use on a flat body, but can also be matched with a curved body. The lead-out line of the flexible membrane keyboard is integrated with the switch body itself. When making the connection of the group switch, it is gathered in a certain place of the membrane and extended outward according to the designated position and standard line distance of the design as a soft , The arbitrarily bendable and sealed lead wire is connected to the rear circuit of the complete machine.
2. Rigid membrane keyboard
The rigid membrane keyboard means that the graphics and circuits of the switch are made on the common printed circuit copper clad laminate. The rigid membrane keyboard is characterized by convenient materials, stable technology, low resistance, and the ability to directly weld certain components in the circuit on its back. In the case of a small area, the hard liner layer can be omitted. Rigid membrane keyboards generally use metal guides as conductive labyrinth contacts, so they have a better feel. The disadvantage is that it is not as convenient as the flexible membrane keyboard to install and connect in the whole machine, and it is often necessary to weld the plug-in unit and lead the lead through the flat cable. In addition to the buzzer signal and LED indication, the information feedback of the rigid membrane keyboard can generally use metal handle shrapnel.
3. Flat membrane keyboard
The keys on the membrane keyboard use different colors to indicate the position, shape and size of the key body, which is more common in the initial stage of the membrane keyboard. Three-dimensional membrane keyboard: Usually, the keys on the membrane keyboard only use colors to express the position, shape and size of the key body. In this way, the accuracy of the operation can only be recognized by the operator's vision. Since there is no appropriate feedback information to indicate whether the finger is pressed in the effective range of the switch to make the switch operate, it affects the confidence in the monitoring of the whole machine and the speed of operation. A kind of membrane keyboard that makes the switch key body slightly protrude, slightly higher than the panel to form a three-dimensional shape, is called a three-dimensional key switch. The three-dimensional key can not only accurately specify the range of the key body, improve the recognition speed, make the operator's touch more sensitive, but also enhance the decorative effect of the product appearance. The production of the three-dimensional key must be done in the design stage of the panel Arrangement, with process holes for precise positioning during mold pressing, and the height of the three-dimensional protrusions should generally not exceed twice the thickness of the substrate. In order to make the appearance of the product beautiful, the protrusion of the raised membrane keyboard can have various changes.