The production process of flexible printed circuit board is basically similar to the production process of rigid plate.For some operations, the flexibility of laminate requires different devices and completely different treatment methods.Most flexible printed circuit boards adopt a negative approach.However, there are some difficulties in the machining and coaxial processing of the flexible laminate, and the main problem is the processing of the substrate.Flexible material is the coil of different widths, so during etching, the flexible laminates need to be used with rigid brackets.
In the production process, the processing and cleaning of the flexible printed circuit is more important than the rigid plate (Lexin, 1993).Improper cleaning or violation of discipline after operation may lead to failure in product manufacturing, this is due to the sensitivity of the use of flexible printed circuit, in the process of manufacture of flexible printed circuit plays an important role.The substrate is affected by mechanical pressure such as paraffin, lamination and electroplating, and copper foil is also susceptible to percussion and indentation, while the extension ensures maximum flexibility.The mechanical damage or hardening of copper foil will reduce the flexible life of the circuit.
During manufacturing, the typical flexible single surface circuit needs to be cleaned at least three times. However, due to its complexity, multi-substrate needs to be cleaned 3-6 times.In contrast, a rigid multilayer printed circuit board may require the same number of cleaning times, but the cleaning procedures are different, and the cleaning of flexible materials needs to be more careful.Even when the pressure is very light in the process of cleaning, the space stability of the flexible material will be affected, and the panel will be elongated in the z or y direction, depending on the bias of the pressure.The chemical cleaning of flexible printed circuit boards should be environmentally friendly.The cleaning process includes alkaline bath, thorough rinsing, micro-etching and final cleaning.Damage to thin film materials occurs frequently in the panel, stirring in the pool, removing the shelves from the pool, or unshelving, and the damage of surface tension in the clear pool.
The hole in the flexible plate is usually perforated, which leads to the increase of machining cost.Drilling is also possible, but it requires special adjustment of the borehole parameters to obtain an unstained hole wall.After drilling, remove the drilling dirt in a water cleaner with ultrasonic stirring.
It has been proved that the mass production of flexible plates is cheaper than the rigid printed circuit boards.This is because the flexible laminate enables the manufacturer to produce circuits on a continuous basis. The process starts with laminate rolling and produces finished panels directly.In order to create a continuous processing diagram of printed circuit boards and etching flexible printed circuit boards, all production processes are completed in a series of sequential machines.Screen printing may not be part of this continuous transmission process, resulting in an interruption of the online process.
Usually, due to the limited thermal resistance of the substrate, the welding in the flexible printed circuit is more important.Manual welding requires sufficient experience, so use wave soldering if possible.When welding flexible printed circuit, the following items should be noted:
1) because polyimide has hygroscopicity, before welding circuit must be baked (in the 250 ° F for 1 h).
2) the welding disk is placed in a large conductor area, such as the ground layer, power layer or radiator, and the heat dissipation area should be reduced, as shown in figure 12-16.This limits heat distribution and makes welding easier.
3) when manually welding pins in a dense area, try not to weld adjacent pins continuously and move them back and forth to avoid local overheating.
The design and processing of flexible printed circuits can be obtained from several sources, but the best sources of information are producers/suppliers of processing materials and chemicals.High quality flexible printed circuit boards can be produced through the information provided by suppliers and the scientific experience of processing experts.