Differences in FPC manufacturing methods such as subtractive method

There are several types of flexible printed circuit board (FPC) manufacturing methods, each with its own advantages and disadvantages.
This page explains the differences in manufacturing methods in flexible printed circuit boards (FPCs), such as subtractive and semi-additive methods.

What is the difference between FPC manufacturing methods?

There are two main methods of forming circuit patterns in flexible printed circuit board (FPC) manufacturing.

One is to remove copper foil from non-circuit areasThe other is to form a circuit by copper plating.

In the method of forming circuits with copper plating, there are two methods: one is to form a seed layer before plating, and the other is to perform surface treatment such as catalyzing on an insulator and then directly plating.

Type of each manufacturing method

subtractive method

The subtractive method is a method of forming circuit patterns by removing copper foil from non-circuit areas. The name comes from the English word subtract.

The specific method involves first masking with resist the areas of the flexible copper-clad laminate where circuits are not to be formed. After that,Etching is performed to remove copper foil from unnecessary areas to form a circuit pattern. Finally, resist is removed to finish the process.

The subtractive method has the disadvantage that it is more difficult to form fine circuits than the additive method described below due to the limitations of etching technology.

additive method

The additive process is a method of forming circuits by applying copper plating. The name is derived from the English word "add.

The additive method is a method of forming circuits by copper plating,Semi-additive method, in which a seed layer is formed before plating, and full-additive method, in which a surface treatment such as catalyzing is performed on an insulator and then plated directly

Compared to the subtractive method, the additive method enables the formation of finer circuits, but it has disadvantages in terms of adhesion of the plating film. To overcome this disadvantage, various companies are developing various technologies.

semi-additive method

After forming a seed layer by sputtering or electroless plating on a substrate such as polyimide film, masking with resist is applied to areas where circuits will not be formed. Subsequently,Electrolytic copper plating is applied to grow the circuit areas where the seed layer is exposed. Finally, the resist is removed to finish the process.

full additive method

Surface treatment such as catalyzing on insulator substratesand masking with resist is applied to the areas where circuits are not to be formed. Then, electroless copper plating is performed to finish.

Summary

Flexible printed circuit boards (FPCs) can be broadly classified intoThree manufacturing methods: subtractive, semi-additive, and full-additive methods

Each method has its own advantages and disadvantages, and each company has different circumstances to overcome the disadvantages. Please consult with the manufacturer carefully so that they can select a manufacturing method that meets the specifications required for the substrate.

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Handling Flexible PCBs