The Performance of FPC Membrane Keypad Is Directly Related to the Normal Use of Membrane Keypad

When the membrane keypad is made into a "switch", the connecting wires of the function keys are pre-connected together. Unlike discrete switch components, the pins of each switch need to be connected with solder wires. Therefore, the membrane switch circuit can avoid welding errors, save welding time, and facilitate assembly and connection. This is also the convenience and reliability of the membrane switch. Since the connection of the membrane keypad is pre-made, the design of the membrane switch circuit should be submitted to the manufacturer as a process document.

The design of the FPC membrane switch circuit can be divided into two types

One is the ordinary wire method, where all the membrane switches are connected to a single wire, and the other end of the wire is separated. The advantage is that each contact can directly control a specific function. In this case, the obtained signal does not require additional decoding in the back-end circuit. This type of connection usually has only a few functional keys available. When the number of contacts is large, the number of leads is correspondingly large, and the total number of output lines is greater than the number of switches, which is not conducive to the overall connection of the FPC membrane switch. The other is the x-y matrix alignment method, which consists of rows and columns of the matrix. One end of the contact is drawn by the lines in the same direction (x direction), regardless of the number of contacts, and the other end of the membrane switch contact is drawn by the common lines in the same direction (y direction). In this way, the matrix array can form any contact x-y combination. Decoding is usually set in the back-end circuit before controlling each specific function, but it is not difficult in the logic circuit.

Using the x-y matrix method, the output lines are smaller. In some circuits of the whole machine, or due to the working conditions (working current and working voltage) of certain components, or to prevent the switch circuit from interfering with the components, certain switch keys can be specially treated. In the design of the FPC membrane switch circuit, a mixed mode of ordinary bus and single lead can be used. (You may want to contact the membrane keypad manufacturer)

The design of the FPC membrane switch circuit is a guiding document for process production

The design matrix should be consistent with the actual key positions, easy to test and avoid errors. When drawing the circuit diagram, the function of each key should be directly marked in the matrix, so that it corresponds to the actual position of the key and is arranged in order from left to right. At first glance, it is not necessary to list the circuit relationships. As a part of the control system, it includes not only the switches and their wiring but also a group of wires manufactured at the same time and connected to the back-end circuit. The exit positions of the two leads should be the same as the exit position of the back loop, and the rationality and convenience of the connection should be considered. At the same time, the metal wires should be connected to the substrate to minimize bending and make the metal wires the shortest and most economical path.

To maintain a good connection with the circuit components, the distance between the wire and the lead is usually in inches. The number of leads depends on the number of keys or the need for leads but should be limited by the connector specifications. Sometimes, in order to measure and discover the connection between each pin, there should be a line between the pins of the rows and columns, and a line between the common bus and each pin to distinguish them. When the number of output lines does not match, "dummy line positions" should be used to match the selected line positions and should be consistent with the output lines of the connected back loop to prevent the line from being disconnected from the connection and the back loop. The length of the leads of the FPC membrane switch and the circuit is made on the same film substrate, and they have the flexibility to meet bending needs, so their length should be slightly longer than the actual (straight line) length. However, if it is too long and heavy, it will also increase the difficulty and cost of production, and if it is too short, it will be inconvenient for insertion.

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