PCB News - The production difference of rigid and flexible circuit boards

The production difference of rigid and flexible circuit boards

The production process of flexible circuit board FPC is basically similar to the production process of rigid board.

For some operations, the flexibility of the laminate requires different devices and completely different processing methods. Most flexible circuit boards FPC adopt a negative method. However, some difficulties have arisen in the mechanical processing and coaxial processing of the flexible laminate. One of the main problems is the processing of the substrate. Flexible materials are rolls of different widths, so during etching, the transfer of flexible laminates requires the use of rigid trays.

In the production process, the handling and cleaning of flexible printed circuits is more important than handling rigid boards. Incorrect cleaning or operation in violation of regulations may lead to subsequent failures in product manufacturing. This is due to the sensitivity of the materials used in the flexible printed circuit. The flexible printed circuit plays an important role in the manufacturing process. The substrate is affected by mechanical pressure such as wax drying, lamination, and electroplating. The copper foil is also susceptible to knocking sounds and dents, and the extended part ensures maximum flexibility. Mechanical damage or work hardening of the copper foil will reduce the flexible life of the circuit.

During manufacturing, a typical flexible single-sided circuit needs to be cleaned at least three times. However, multi-substrates need to be cleaned 3-6 times due to its complexity. In contrast, rigid multilayer printed circuit boards may require the same number of cleaning times, but the cleaning procedures are different, and more care needs to be taken when cleaning flexible materials. Even if it is subjected to very light pressure during the cleaning process, the dimensional stability of the flexible material will be affected, and it will cause the panel to elongate in the z or y direction, depending on the bias of the pressure. The chemical cleaning of flexible circuit board FPC should pay attention to environmental protection. The cleaning process includes alkaline dye bath, thorough rinsing, micro-etching and final cleaning. The damage of the film material often occurs during the process of loading the panel, when agitating in the tank, removing the rack from the tank or not setting up the rack, and destroying the surface tension in the clean tank.

The holes in the flexible board are generally punched, which leads to an increase in processing costs. Drilling is also possible, but this requires special adjustment of the drilling parameters to obtain a smear-free hole wall. After drilling, remove the dirt from the drilling in a water cleaner with ultrasonic agitation.

The mass production of flexible boards is cheaper than rigid circuit board PCBs. This is because flexible laminates enable manufacturers to produce circuits on a continuous basis. This process starts with laminate rolls and directly produces finished boards. In order to manufacture a printed circuit board and etch a continuous processing schematic diagram of the flexible circuit board FPC, all the production processes are completed in a series of machines placed in sequence. Screen printing may not be part of this continuous transfer process, which caused an interruption in the online process.

Generally, 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.