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.
Frequently Asked Questions about Flexible Printed Circuit Boards
Q1. Should I order from domestic manufacturers or overseas manufacturers?
Domestic manufacturers excel in quality control, short delivery times, and detailed specification adjustments, making them suitable for prototyping and small-volume, high-mix production. Overseas manufacturers have a cost advantage, but it is necessary to consider delivery times and quality risks.
Q2. Should we change suppliers for mass production after prototyping?
For prototypes, we recommend selecting manufacturers that are flexible in adapting to specification changes, and for mass production, prioritize cost and stable supply. Manufacturers that can handle both will minimize transition-related issues.
Q3. Please tell me the selection criteria for single-sided, double-sided, and multi-layer Flexible Printed Circuits (FPCs).
We judge based on circuit complexity and implementation space. Single-sided is suitable for simple wiring applications, double-sided for complex circuits and double-sided mounting, and multi-layer FPCs are suitable when high-density and high-speed transmission are required.
Q4. Should I choose FPC or rigid-flex PCB?
Rigid-flex printed circuit boards are effective when you want to increase reliability by eliminating connectors or when three-dimensional mounting is required. Please organize your requirements before selecting, as they increase costs and manufacturing difficulty.
Q5. When selecting a manufacturer, what points should be confirmed?
It is important to confirm the minimum processable line width, number of layers, types of surface treatments, delivery time track record, compliance with quality standards, and the feasibility of integrated support from design to implementation.
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.
See the List of Manufacturers
Handling Flexible PCBs
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