The production process of a flexible printed circuit board is basically similar to the production process of a rigid board. For some operations, the flexibility of the laminate requires different equipment and completely different treatment methods. Most flexible printed circuit boards use a negative approach. The production process of a flexible printed circuit board is basically similar to the production process of a rigid board. For some operations, the flexibility of the laminate requires different equipment and completely different treatment methods. Most flexible printed circuit boards use a negative approach. However, some difficulties arise in the machining and coaxial processing of flexible laminates. A major problem is the handling of the substrates. Flexible materials are webs of different widths, so the transfer of flexible laminates requires a rigid bracket during etching. In the production process, the handling and cleaning of flexible printed circuits is more important than the handling of rigid plates (Lexin, 1993). Improper cleaning or violations of the procedure may result in failures in subsequent product manufacturing due to the sensitivity of the materials used in the flexible printed circuit, which plays an important role in the manufacturing process. The substrate is affected by mechanical stresses such as baking wax, lamination and plating. The copper foil is also susceptible to knocking and dents, while the extension ensures maximum flexibility. Mechanical damage or work hardening of the copper foil will reduce the flexible life of the circuit. A typical flexible single-sided circuit is cleaned at least three times during manufacturing, however, multiple substrates require cleaning for 3-6 times due to its complexity. In contrast, rigid multilayer printed circuit           boards may require the same number of cleaning cycles, but the cleaning procedure is different, and care must be taken when cleaning flexible materials. Even under the extremely light pressure during the cleaning process, the dimensional stability of the flexible material is affected and the panel is elongated in the z or y direction depending on the bias of the pressure. Chemical cleaning of flexible printed circuit boards should be environmentally friendly. The cleaning process includes alkaline dye bath, thorough rinsing, micro-etching and final cleaning. Damage to the film material often occurs during the shelf life of the panel, when the tank is agitated, when the shelf is removed from the pool or when there is no shelf, and the surface tension is destroyed in the clear pool. The holes in the flexible board are generally punched, which leads to an increase in processing cost. Drilling is also possible, but this requires special adjustment of the drilling parameters to obtain an unstained hole wall. After drilling, the borehole dirt is removed in a water cleaner with ultrasonic agitation. Mass production of flexible boards has proven to be less expensive than rigid printed circuit boards. This is because flexible laminates enable manufacturers to produce circuits on a continuous basis, starting with laminate rolls and directly producing finished boards. To produce a printed circuit board and etch a continuous process schematic of the flexible printed circuit board, all production processes are performed in a series of sequentially placed machines. Screen printing may not be part of this continuous transfer process, which creates an interruption in the online process. In general, soldering in flexible printed circuits is more important due to the limited heat resistance of the substrate. Manual soldering requires sufficient experience, so if possible, wave soldering should be used. When soldering flexible printed circuits, the following should be noted: 1) Because polyimide is hygroscopic, the circuit must be baked before soldering (for 1 h at 250 °F). 2) The pad is placed over a large conductor area, such as a ground plane, power plane, or heat sink. The heat sink area should be reduced, as shown in Figure 12-16. This limits heat dissipation and makes soldering easier. 3) When soldering the pins in a dense place, try not to continuously solder adjacent pins and move the solder back and forth to avoid local overheating. Information on flexible printed circuit design and processing can be obtained from several sources, however the best source of information is always the producer/supplier of processed materials and chemicals. Through the information provided by the supplier and the scientific experience of the processing experts, high-quality flexible printed circuit boards can be produced.