Many PCB manufacturers fail to realize that a rigid-flex PCB is complex and requires a lot of communication between them and the consumers. There must be early discussions between the designer and the rigid-flex PCB manufacturer.
This article will explain all the necessary rigid-flex PCB manufacturing steps that you must carry out with precision.
1. Prepare and Clean the Base Material of Rigid-flex PCB
You should start the manufacture of rigid-flex boards by cleaning/preparing laminates for rigid-flex boards. Laminates consist of copper layers with adhesive or adhesive coating. It should be scrubbed carefully before being used in the further rigid-flex PCB manufacturing process.
This kind of pre-cleaning is essential because usually, the copper coil is covered with an anti-rust layer for oxidation protection. However, this protective layer is an obstacle to rigid-flex PCB manufacturing, and we need to deal with it.
Many PCB manufacturers naturally follow these three steps,
- First, you need to completely immerse the copper foil in an acid solution. If not, it can be sprayed with acid.
- Next, you will treat the copper coil with a sodium persulfate solution to micro etch it.
- Finally, you need to coat the coil extensively with an appropriate kind of oxidant. This will help you prevent oxidation and adhesion.
2. Generate Circuit Pattern for the Rigid-flex PCB
The second step in manufacturing a rigid-flex PCB board is to generate circuit patterns. Remember, always after finishing the laminate preparation. Now, the following two methods mainly generate circuit patterns:
- Screen printing-This method can directly produce the desired circuit deposits/patterns on the surface of the laminate. This is also the reason for its popularity.
- Photographic imaging-This is an ancient technology, but it is still very famous for drawing circuit patterns on the surface of laminates. You need to place the dry photoresist film containing the desired circuit pattern close to the laminate. After that, you must expose this component to ultraviolet light.
This will ensure that the circuit pattern is transferred from the photomask to the laminate. Finally, you will need to use chemicals to remove the film. Then, only keep the laminate with the required circuit traces.
3. Use the rigid-flexible printed circuit board to etch the copper laminate of the circuit board
After generating the circuit pattern, the next step is to etch the copper laminate. For rigid-flex printed circuit board manufacturing, you can immerse the laminate in an etching bath or spray it with an etchant solution. In addition, you need to engrave both sides of the copper laminate at the same time. Only in this way can you achieve the desired result.
4. Precise drilling on rigid-flex PCB
Now that you have engraved the copper laminate, you can start drilling. You can drill holes, vias, and pads according to customer requirements. As a rigid-flex PCB manufacturer, you must use advanced equipment to accurately and accurately punch holes.
5. Through-hole plating
The fifth step is one of the key stages of manufacturing rigid-flex PCB. In through-hole plating, you deposit copper in the holes and then electroless plate them. Both steps are after you drill to the required specifications.
The deposition of copper is similar to the witness of rigid PCB holes, which we call composite materials. It is recommended that the thickness of the plated layer of the through-hole of the rigid board is not less than one million miles.
This is to enhance the mechanical support of the via or pad. In contrast, a typical inexpensive rigid-flex PCB can have about ½ mil composite material. This step will allow current to flow in the form of layer-to-layer electrical connections.
6. Protect Rigid-Flex with a cover plate or cover plate
Next, you must cover the top and bottom surfaces of the rigid-flexible PCB with a cover layer. Will protect it. The rigid-flex board will be essentially protected from harsh chemicals, harsh weather conditions, and solvents.
For covering materials, most rigid-flex printed circuit board manufacturers use polyimide film and adhesives. Screen printing will cover the surface of the rigid-flexible board with a covering material.
Then you need to put it under ultraviolet light. In order to make the cover cloth and the substrate surface contact correctly, the cover sheet can be laminated under certain pressure and heat limitation.
Likewise, the difference between the cover layer and the cover layer material must be recognized. The cover layer is a laminated film, and the cover layer is directly coated on the surface of the substrate.
Now, deciding which type of coating to use depends on your application, the materials available, and the manufacturing method of the rigid-flex PCB. There is no doubt that both the cover layer and the cover layer can enhance the electrical integrity of a rigid-flexible PCB.
7. Cutting of rigid-flex board
The final second step is to cut the rigid-flex PCB board. You should blank or cut rigid-flex boards with extreme care. As a manufacturer of rigid-flex boards, you can choose hydraulic punching and mold setting methods to mass-produce rigid-flex boards.
However, we do not recommend using it for small batch production or prototyping. This is because of its high mold costs. Or, you can use a special blanking knife to develop a small number of rigid-flex PCB prototypes.
8. Electrical testing and verification of the final rigid-flexible PCB
The final step in manufacturing a rigid-flex PCB is to test and verify it. You need to conduct strict electrical tests on rigid-flex PCB boards. It will ensure isolation, continuity, quality, and circuit performance according to design specifications. Currently, flying probe and grid testing methods are very popular.
In addition, if you know the material properties, it will also help you to verify and test rigid-flex PCBs. For example, if your product is related to the automotive industry, you should model moisture, heat, shock and resonance, and chemical properties.
The precise material properties determine the minimum allowable bending radius and product reliability.
In short, as a rigid-flex PCB manufacturer, you must be very cautious from the beginning. We summarized all eight steps that should be followed when planning to manufacture a rigid-flexible PCB. The steps start with form design, material selection design, development of rigid-flex PCB, and then electrical inspection.
If you need a combination of soft and hard PCB manufacturing services, you can contact us, we can provide technology, materials, and quality services.