Circuit board manufacturers, circuit board designers, and PCBA processors explain the final metal surface treatment of FPC circuit boards

Copper is a reactive metal that must be treated with specific materials at the exposed end to maintain weldability or allow for crimping after storage. In general, FPC manufacturers will provide optional processing options.

Gold is used for connector processing at the edges of circuit boards and occasionally appears in trusted FPC designs. This treatment is generally based on electroplating technology. The bottom layer often handles one layer at a time. This state means that the conductor circuit remains connected by the interconnection mechanism.

Applying (or coating) protective film before electroplating is a good choice, as it means that the opening and electroplating treatment of the protective film can ensure the integrity of the alignment. There should be no exposed conductor surface, and there should be no adhesive on the electroplated surface. After applying protective film, electroplating must be carried out, and the conductor must be retained in the design. Is the external part extending to the cutting position cut off during molding, or can the conductor be removed through post etching, stamping, and machining. Finished products, etc. When the terminal does not retain the conductor, chemical tin plating can be used to electroplate the exposed terminal area.

Solder coating or tin treatment on the surface can provide excellent overall protection for soft board terminals. It can be used in conjunction with subsequent (welding) assembly techniques and can also be used in the production of many pressure connectors. Solder is a commonly used choice for PCB surface treatment and can be easily used in soft board applications. Unless tin infiltration occurs due to improper handling, it can lead to re melting during assembly and welding, which will inevitably damage the bonding and opening of protective films or coatings.

Therefore, welding must be carried out during the process of applying protective film. If electroplating is to be used for welding, the conductor must be retained. Hot air leveling soldering is one of the solutions. Widely used in the production of low-cost and limited soldering treatments. However, high temperature and forced hot air treatment are necessary procedures, so pre baking is used to remove moisture, and then exposed to the soldering furnace for hot air leveling to remove excess solder. However, this type of soft board processing will cause the soft board to slightly shrink and twist after processing. And there is a risk of stratification. However, after the promotion of lead-free technology, the problem of high working temperature of lead-free solder will make this process more difficult to use.

The coating of organic welding protective film has quickly become popular due to its ease of introduction into FPC factories, the product does not require wires, and can provide appropriate storage stability. It can be obtained from various electrochemical suppliers, but the time required for processing varies, mainly depending on the expected storage life and tank temperature. The practice of soaking at room temperature to 50 ℃ for 1-5 minutes is commonly used.

Chemical precipitation tin plating is another optional solution, suitable for all types of FPC, easy to control, and will not damage the circuit. When it is assumed that the gasket is clean and not excessively stored during the manufacturing process, this is a reasonable method to maintain weldability in the short term. Circuit board manufacturers, circuit board designers, and PCBA processors will introduce the final metal surface treatment of FPC circuit boards.