FPC’s shadow line process (Shadow)
    The black shadow process is suitable for high-end FPC, 5G products, the mainstream process of high-end PFC, and is increasingly adopted by high-end FPC manufacturers. At present, the main representatives of the market are medicine dealers: Mai Demei, Le Si. Shenzhen Feishida Machinery Equipment Co., Ltd. and Mai Demei have successfully cooperated with many equipments, and many companies are in mass production.
   The shadow method mainly uses Graphite as a conductive object. Due to the large number of free electrons in the molecular structure of graphite, the conductivity of graphite is higher than that of general carbon black. The electroplating speed is directly proportional to the electrical conductivity of the coating, so the higher the electrical conductivity of the coating, the faster the electroplating speed.
The Shadow Direct Metallization Process is simple, mainly divided into five chemical tanks:
(1) Cleaner/Conditioner
(2) Black Shadow Slot (Conductive Colloid)
(3) Fixer
(4) Micro-Etch
(5) Anti-Tarnish
Among them, the anti-oxidation tank is more selective, depending on the time the production board is placed to determine whether it is needed or not.
The shadow method has horizontal (Conveyor) and vertical (Vertical) production methods. However, because the vertical production method takes longer production time and is not as simple as horizontal production, the company strongly recommends the shadow horizontal conveying production method to replace the current production method. Traditional copper sinking process.
Types of Chemical Agents in Sombra Process
(1) Cleaner/Conditioner
The cleaning/porosing agent is a slightly alkaline liquid, the main function is to clean the surface of the hole wall and as a conditioning agent (Conditioner) to adjust the surface of the glass fiber and epoxy resin suitable for conductive colloids to have sufficient adsorption.
(2) Black Shadow Agent (Conductive Colloid)
The shading agent is a slightly alkaline liquid, which contains unique additives and conductive colloidal substances to form a conductive layer on the wall of the hole.
(3) Fixer
Remove the excess black shadow agent on the hole wall, so that the black shadow conductive layer can be more evenly distributed on the hole wall.
(4) Micro-Etch
The main components of the microetching agent are sodium persulfate and sulfuric acid. The main function of the microetching agent is to remove the black shadow on the copper surface through the side etching effect. Because the resin and glass fiber are inert, the micro-etching agent cannot remove the black shadow on the sheet.
(5) Anti-Tarnish
Antioxidant is a slightly acidic liquid, which is used to protect the copper surface so that it will not be easily oxidized
Shadowing process: boarding + micro-etching + washing + whole hole + shadowing + fixing + washing + drying