Hole metallization-double-sided FPC manufacturing process

The hole metallization of flexible printed boards is basically the same as that of rigid printed boards.

In recent years, there has been a direct electroplating process that replaces electroless plating and adopts the technology of forming a carbon conductive layer. The hole metallization of flexible printed circuit board also introduces this technology.
Due to its softness, flexible printed boards need special fixing fixtures. The fixtures can not only fix the flexible printed boards, but also must be stable in the plating solution, otherwise the thickness of the copper plating will be uneven, which will also cause disconnection during the etching process. And the important reason for bridging. In order to obtain a uniform copper plating layer, the flexible printed board must be tightened in the fixture, and work must be done on the position and shape of the electrode.

For outsourcing processing of hole metalization, it is necessary to avoid outsourcing to factories with no experience in the holeization of flexible printed boards. If there is no special plating line for flexible printed boards, the quality of holeization cannot be guaranteed.

Cleaning the surface of copper foil-FPC manufacturing process

In order to improve the adhesion of the resist mask, the surface of the copper foil must be cleaned before coating the resist mask. Even such a simple process requires special attention for flexible printed boards.

Generally, there are chemical cleaning process and mechanical polishing process for cleaning. For the manufacture of precision graphics, most occasions are combined with two kinds of clearing processes for surface treatment. Mechanical polishing uses the method of polishing. If the polishing material is too hard, it will damage the copper foil, and if it is too soft, it will be insufficiently polished. Generally, nylon brushes are used, and the length and hardness of the brushes must be carefully studied. Use two polishing rollers, placed on the conveyor belt, the rotation direction is opposite to the conveying direction of the belt, but at this time, if the pressure of the polishing rollers is too large, the substrate will be stretched under great tension, which will cause dimensional changes. One of the important reasons.

If the surface treatment of the copper foil is not clean, the adhesion to the resist mask will be poor, which will reduce the pass rate of the etching process. Recently, due to the improvement of the quality of copper foil boards, the surface cleaning process can also be omitted in the case of single-sided circuits. However, surface cleaning is an indispensable process for precision patterns below 100μm.