The performance of the FPC film key switch is directly related to the normal use of the film key switch. When the film key switch is made into a “Switch”, the connecting wires of the function keys are connected together in advance. Unlike discrete switch elements, each switch pin needs to be connected with a welding wire. Therefore, the thin film switch circuit can avoid welding error, save welding time, and facilitate assembly and connection. This is also the convenience and reliability of the membrane key switch. Since the connection of the membrane switch is prefabricated, the design of the Membrane Switch Circuit shall be submitted to the manufacturer as a process document. Thin-film key switch circuit design can be divided into two. One is the ordinary wire method, film switch all contact with a wire connection, the other end of the wire separation. The advantage is that each contact has direct control over a specific function. In this case, the acquired signal does not require additional decoding in the post-circuit. This type of connection is usually available with only a small number of function keys. When the number of contacts is large, the number of leads is correspondingly large, and the total number of outlets is larger than the number of switches, which is unfavorable to the integral connection of membrane switches. The other is the method of x-y Matrix alignment, which consists of rows and columns of the Matrix. One end of the contact is drawn by a line in the same direction (x direction) , independent of the number of contacts, and the other end of the membrane switch contact is drawn by a common line in the same direction (y direction) . In this way, the matrix array can form any contact x-y combination. Decoding is usually set up in the back-end circuit before controlling each particular function, but it is not difficult in the logic circuit.Using the x-y matrix method, the output line is smaller. In some circuits of the whole machine, or because of the working condition of some components (working current and working voltage) , or in order to prevent the interference of the switching circuit to the components, some switch keys can be specially treated. In the design of thin-film switch circuit, the hybrid mode of common bus and single-lead can be used. The design of thin-film Switch Circuit is the guidance document of process production. The design Matrix should be consistent with the actual key position, easy to test and avoid errors. When drawing a circuit diagram, the function of each key should be marked directly in the Matrix so that it corresponds to the actual position of the key and is arranged from left to right. At first glance, there is no need to list the wiring relationships. As an integral part of the control system, it includes not only the switch and its wiring, but also a set of concurrent wires connected to the rear circuit. The exit position 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, should consider the metal wire and the substrate connection, as far as possible reduces the bending, causes the metal wire to become the shortest economical path.In order to maintain a good connection to the circuit elements, the distance between the wire and the lead is usually 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 row and column, and a line between the common bus and each pin to distinguish them. When the number of output lines does not match, the “False line position”shall be used to match the selected line position and shall be consistent with the output line of the connected back loop to prevent the line from leaving the connection and back loop. Lead-length thin-film switch leads and circuits are made on the same thin-film substrate, they are flexible to meet the needs of bending, so their length should be slightly longer than the actual (straight) length. But too long is too heavy, also increased the difficulty of production and cost is too short, the plug is inconvenient.