FPC Plating

In the manufacturing of flexible printed circuit boards (Flexible PCBs), plating is a critical process used to ensure electrical conductivity and to protect the circuitry.
This page explains various plating techniques used in Flexible PCBs, including electroplating.

What Is Plating in Flexible PCBs?

Plating to Add a Conductor Layer to the Substrate

To add a copper layer to the base insulating material,

electroless plating is used to form a conductive seed layer on the substrate surface.

Used for circuit formation plating

To form the actual circuits, both electrolytic copper plating and electroless copper plating are used.

through-hole

Through-hole plating is used in multilayer flexible PCBs, such as those with two or more layers. It involves drilling holes to establish electrical connections between conductor layers, and then plating the inner walls of the holes.

After securing conductivity inside the holes with electroless copper plating, electrolytic copper plating is applied.

Used in surface finishing

Various plating types are used for terminal surface finishing.

Common methods include electrolytic nickel-gold plating, electroless nickel-gold plating, tin plating,and solder plating.

Differences Between Plating Methods

Electroless Plating

Electroless plating is a process that deposits metal onto the conductive surface of a Flexible PCB using a chemical reaction in the plating solution.

Common metals used include copper, nickel, and gold. Compared to sputtering, electroless plating can be performed in ambient conditions, which increases productivity. Additionally, since no electrodes are required as in electrolytic plating, it allows for uniform film thickness with greater ease.

However, it requires pretreatment and strict control of the plating solution to ensure proper chemical reactions and high-quality plating layers. Proper waste disposal must also be considered.

Electroless Copper Plating

Plating for circuit formation and through-hole plating used in circuit formation and through-hole plating processes.

Electroless Nickel Plating (ENP)

Applied over a nickel layer during surface finishing. It can also be applied directly in some cases.
This type of gold plating provides excellent solderability.

Electroless Gold Plating

Commonly used as plating applied over nickel in plating for surface treatment. There is also a method of directly applying gold plating.. This type of gold plating provides excellent solderability.
It is characterized by good solder wettability.

Electrolytic Copper Plating

Electrolytic plating is a treatment method in which the flexible printed circuit (FPC) acts as the cathode and the required metal or an insoluble electrode acts as the anode.&nbspWhen current is applied, metal is deposited onto the conductive surface of the FPC.

Metals commonly used include copper, nickel, tin, and solder. This method allows film thickness to be controlled more easily and enables faster processing, although additional measures may be required to achieve uniform thickness across the entire surface.

Electrolytic Copper Plating

Used for circuit formation platingandthrough-holeplating.

Electrolytic Nickel Plating

Used in surface finishingcreate an underlayer for gold plating.

Electrolytic gold plating

Used in surface finishingand commonly applied over nickel.

Because the gold layer is thicker than with electroless gold plating, electrolytic gold plating is selected when frequent mating/unmating cycles are expected and durability is required. While performance is good, cost is higher.

Electrolytic Solder Plating

Commonly used at joining points,such as connection areas with other circuit boards.

Summary

Plating includes a wide range of methods, and the metals introduced here are relatively widely used in flexible PCB (FPC) manufacturing.

Because many combinations of plating methods and metals are available, it is advisable to share the required specifications and intended application with the manufacturer so that appropriate options can be recommended.

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