As flexible PCB supplier china knows that，the production or manufacturing process of Rigid-Flex PCBs is quite similar to rigid PCBs, except for a few things. Before starting the manufacturing process, our experts check all the files provided by the buyer. We offer free DFM PCB design checking to ensure there is no problem with the design. Our experts ensure the quality standards. This checking can eliminate the delays and ensure the delivery at the right time.

1) Material Selection

At first, the material is selected for the rigid and flexible parts. We have already discussed that Polyimide (PI) is commonly used for the flexible part, and FR-4 is used for the rigid part. However, everything depends on the buyer. Once the buyer informs what material will be used, everything is procured according to that. After the selection of material, the process of PCB fabrication starts.

After the selection of the board, it is thoroughly cleaned by going through various processes. It is cut into the required sizes, and the final product is ready to be used.

2) Drilling

The drilling of the board is sometimes carried out at the start, while some manufacturers do it after the etching of the board when it has the complete circuitry.

However, at this stage, the board is empty, so drilling would be quite easy. Moreover, it will be easier to clean the dirt and other pollution after the drilling as there is no circuitry on the board. The drilling is carried out according to the requirement. It is an automated process that completes the drilling according to the Gerber file. After drilling, the board is cleaned through various chemical processes, according to the type of material used. The common methods are the sulphuric acid method, chromic acid method, and plasma method.

After that, the boards can have plated through holes (PTH) after going through a chemical process. There are various baths of chemicals. The electroplating process is done with care because Polyimide is a delicate material, which might swell in the presence of strong alkalis. 

Learn more about what is via the hole in PCB?

3) Copper Plating

The PCB requires a certain thickness of copper plating, which acts as the conductive layer. The copper is plated as required by the buyer.

4) Circuit Pattern

Until this stage, the board only has holes; there is no circuitry on it. Now, it is time to generate the circuit pattern. Typically, the board is exposed to UV light. Before exposing the board to the UV light, a photo-resistive film is applied to the board. The film has the required circuit, and when the board is exposed to UV light, a pattern is created on the board. The board is now ready for etching.

5) Etching

The board has the pattern of the circuit. When it goes through the etching process, the copper from the unwanted area is removed, leaving behind the copper on the desired circuit only. A powerful alkaline solution is used carefully with Rigid-Flex PCBs as they are very delicate. The circuit board is dipped into the etching solution, or the solution is sprayed over the board. Usually, in the case of polyimide, an acidic copper chloride etching solution is preferred instead of an alkaline etching solution to prevent swelling.

6) Inspection

The board is almost ready, so it is inspected through various techniques. It goes through AOI (Automated Optical Inspection). In this inspection, there are various cameras at different angles to take the images of the PCB. It detects various errors at the surface of the PCB. It finds out open circuits, solder bridges, solder shorts, and excess or insufficient solder. The test uses statistical values and parameters to compare the board with the ideal one.

7) Solder Mask, Silk Screen, and Surface Finish

These are the three steps that are taken one by one. The solder mask i s applied as required. It prevents the shortage and creation of solder bridges. We have various colors of solder masks available, including Green, White, Blue, Black, Red, and Yellow. We also offer peelable solder masks to our customers.

Silkscreen is the labeling of components and symbols on the board through various inks. It helps to understand the placement of components. It can be in any color you want, including white, black, and yellow.

The copper circuit on the board requires protection as it can undergo oxidation. Therefore, a surface finish is applied to protect the circuit. We offer various types of surface finishes according to the requirements of the buyer, such as OSP, HASL, HASL (Lead-free), Immersion Tin, Immersion Silver, ENIG, and Flash Gold.

8) Testing

Testing is the final step before cleaning the PCB and packaging. It requires detailed testing of the performance of the PCBs. There are different types of tests carried out on the PCB to find errors. Typically, the flying probe test is the most common one because it checks various solder pads and nodes to find the shorts and opens. Other types of tests include In-circuit Testing (ICT), AOI, Burn Testing, and X-Ray inspection.