In order to adapt to the high functionality of vehicles and the diversification of user needs, automotive electronic wiring harnesses have gradually expanded the space occupied in the vehicle. In fact, in order to improve the fuel economy of the car and reduce the weight, the wire itself is continuously reduced in diameter from the original AV wire, and then passes through the AVS wire to the AVSS wire. The diameter of the wire harness continues to decrease. Moreover, in recent years, the application of multiplex technology (vehicle local area network (LAN)) has greatly reduced the number of circuits. However, from the perspective of the development trend of wiring harnesses, the number of vehicles onboard is still increasing, and the number of circuits on high-end cars even exceeds 2000.

One of the effective ways to reduce the weight of the wiring harness is to use 42V as the power supply voltage. From the perspective of electric power steering (EPS) or electric air-conditioning devices that require large electric loads, it is considered an effective method because it is possible to increase the power supply without increasing the current (the cross-sectional area of the wire does not increase). On the other hand, as the power supply voltage rises, safety issues such as electromagnetic noise or leakage also occur, and shielded wires or waterproof connectors have to be adopted, which increases the weight of the wire harness. Therefore, with the popularization of vehicle-mounted LAN applications, it is required to use wire materials with high shielding characteristics against electromagnetic interference.

Since the 1990s, with European, American, and Japanese automobile companies as the center, the modular production method has been continuously promoted. As the wiring medium in the module, planar wiring materials such as flexible printed circuit (FPC: flexible printed circuit) have been used. circuit) or flexible flat cable (FFC: flexible flat cable). In modules, especially in car items, doors and consoles where wiring space is very limited, it is expected that it will be further promoted in the future as a method of expanding the compartment space and improving the effectiveness of the electronic wiring harness.