Inner Layer Process
(III): Etching and Stripping--FAQ

1. What is PCB etching?

PCB etching is the manufacturing process that removes unwanted copper from the inner layer after photoresist development. Only the copper protected by the photoresist remains, forming the designed conductive circuit pattern.

2. Why is etching important in PCB manufacturing?

Etching directly determines the final trace width, spacing, and circuit geometry. Accurate etching is essential for maintaining electrical performance, signal integrity, and overall PCB reliability.

3. What chemicals are commonly used for PCB etching?

An acidic cupric chloride solution is one of the most widely used etchants for inner-layer PCB fabrication. Its concentration, temperature, and spray conditions must be carefully controlled to achieve consistent and precise copper removal.

4. What happens if the etching process is not properly controlled?

Poor process control can lead to over-etching, which makes traces narrower than designed, or under-etching, which leaves residual copper that may cause electrical shorts. Both conditions can negatively affect product quality and yield.

5. What is photoresist stripping?

Photoresist stripping is the process of removing the hardened photoresist after etching is completed. This reveals the finished copper circuitry and prepares the PCB for the next manufacturing processes.

6. Why is complete photoresist stripping important?

Incomplete stripping can leave chemical residues on the copper surface, which may affect lamination quality, adhesion, impedance consistency, and long-term product reliability.

7. What is AOI inspection after etching and stripping?

Automated Optical Inspection (AOI) uses high-resolution imaging to inspect the finished circuit pattern. It identifies defects such as opens, shorts, missing copper, or irregular trace edges before the PCB proceeds to the next production stage.

8. How do etching and stripping affect PCB performance?

These processes define the final conductor geometry of the PCB. Precise etching and thorough stripping help ensure stable impedance, reliable signal transmission, and consistent electrical performance, especially for high-speed and high-density circuit designs.

9. Can fine-line PCBs be manufactured with high etching accuracy?

Yes. Modern PCB manufacturers use tightly controlled etching equipment, optimized process parameters, and AOI inspection to produce fine-line circuits with high dimensional accuracy and repeatability.

10. What process comes after etching and stripping?

After the inner-layer circuitry has been verified through AOI inspection, the PCB typically proceeds to inner-layer surface treatment (such as black oxide) and lamination, where multiple layers are bonded together to form the multilayer PCB structure.

Learn more: https://www.explus.com.tw/faq/Inner-Layer-Process-III-Etching-and-Stripping.html