Rigid-flex technology provides the flexibility and versatility that is needed for the designing of Printed Circuit Boards (PCBs).
Worthy of mention is that consumers have discovered some of the attributes of rigid-flex PCB, and that informs the reason why they are always looking for a manufacturer to design one for them.
In addition, the solid foundation provided by rigid-flex circuit board makes it easier for the PCB designer to integrate the relevant components and fine-tune the design of the circuit board.
In this article, we will show you all you need to know about the rigid-flex PCB. Some of the things you will learn are the design rules, the cost of manufacturing the circuit board, and the capability of the design.
When Does the Rigid-Flex PCB Become an Ideal Solution?
Before any other thing, let us consider an important aspect of rigid-flex PCB. What could be the reason why consumers want to design their circuit boards using the rigid-flex design?
There are many reasons why it is the ideal solution. Some of the prominent features are:
Versatility
The design and manufacture of electronic products created a new market for Printed Circuit Boards (PCBs). Now, electronics companies are looking for circuit boards that are flexible – which is where the rigid-flex PCB comes into the picture.
The versatility of this circuit is one reason why it is an ideal solution. The versatility cuts across different options, such as geometries and layout options.
Bending
Another reason why consumers like rigid-flex PCB is because of bendable components. Unlike the traditional circuit boards, rigid-flex has multiple bends.
In addition, it plays an important role in the integration of multiple rigid circuit boards. The multiple bends also make it easier for different orientations and mounting positions to be used when designing the rigid-flex Printed Circuit Board (PCB).
Manufacturing Methods of Rigid-Flex PCB
Let us now look at the processes that must be followed to manufacture the rigid-flex circuit board.
Just before we point that out, we want you to understand that there are variants. The first is the traditional method of designing rigid-flex circuit boards. The second is the latest model that involves embedding the circuit boards.
With that being, we will now explain the manufacturing process of each of the rigid-flex PCB designing variants:
1. Traditional Rigid-Flex PCB Design
The first consideration is how to design the circuit board using the traditional method.
Generally, the traditional rigid-flex PCB design involves using an orderly and selective layer stackup model to fabricate the rigid PCB and the flexible PCB. The aim is to connect the two layers by using plated through holes.
Furthermore, the designing or manufacturing process of the rigid-flex PCB is explained below:
Production of Semi-Finished Products
The first step is to design semi-finished products. On the one hand, the polyimide material will be used to produce the single or double layer flex circuit.
On the other hand, FR4 cores will be produced to take the semblance of a multilayer PCB.
Once the layers are produced, the next step will be to create a composite material from no flow or low flow prepregs. Once this is done, semi-finished products/layers will then be pressed into a rigid-flexible composite.
The Structuring Process
The next step in designing the traditional rigid-flex PCB is to structure the circuit board. Doing this entails processing the panels using the standard production processes.
Thereafter, the FR4 cores will be prevented from bonding to the polyimide material by milling out the flexible areas.
Contouring
The last process in the manufacturing of the traditional rigid-flex circuit board is to contour it.
The aim of the contouring process is to facilitate the removal of the non-bonded rigid material from the flexible parts of the board. To do that, a groove will be used to deep mill the flexible areas so that the transition from the rigid parts to the flexible areas will be simplified.
2. Embedded Rigid-Flex PCB Design
As mentioned earlier, there are two methods of manufacturing the rigid-flex Printed Circuit Board (PCB). We have considered the traditional format. Let us now see how the embedded rigid-flex PCB manufacturing technology will be beneficial to the design of the circuit board.
Embedding and Layering
This is no doubt one of the easiest methods of designing the rigid-flex PCB. All there is to do is to embed the flexible circuit into the internal rigid boards. Afterwards, the board will go through the Building Up/Layering process.
Differences between Traditional and Embedded Rigid-Flex PCB Design
Consumers want to know why the two methods of designing and manufacturing rigid-flex PCB differ. If you are looking for the same answers, we got you covered.
Here are the outstanding differences that set the traditional and embedded rigid-flex PCB designs apart:
| Traditional Rigid-Flex PCB Design | Embedded Rigid-Flex PCB Design |
| Has limited flexible area. | The flexible area is larger, and that is why it increases the usage rate of the substrate material. |
| More substrate materials are used. | Drastically reduces the wastage rate of substrate materials. |
| The manufacturing process involves fabrication, which takes more time. | Embedding the flexible circuits into the rigid boards makes this method faster than the former. |
Advantages of Rigid-Flex PCBs
The “mad rush” for rigid-flex PCBs is not unconnected to the multiple features and advantages that the consumers will derive from the circuit board.
It makes sense that you have an idea of what these advantages are so it they would help you understand what you are paying for.
1. Space Saving
Most times, some PCB components are left out because there is not enough space to integrate them on the circuit board.
That has changed since the rigid-flex PCB is now the order of the day. The space saving undertone allows the designer to add more components that will increase the functionality of the circuit board.
2. Lightweight
Most times, the weight of a Printed Circuit Board (PCB) doesn’t necessarily mean that it is durable.
Sometimes, you need the circuit board to be as heavy as a feather. That informs the reason why you should design the rigid-flex PCB because of the lower thickness and lighter weight.
3. Flexibility
There is no limit to what you can design out of the rigid-flex PCB. Thanks to the flexibility and higher freedom; you can make whatever design you want.
In addition, the flexibility empowers you to facilitate the mechanical design and electronic design.
4. Dynamic Bending
Bending circuit board flex seems to be a challenge in the other PCB designs. It doesn’t appear to be so in the rigid-flex PCB because of the dynamic bending allowing you to fold and twist the flex to whichever pattern it will be fit for the circuit board design.
5. Faster Signal Delivery
The pace of delivering signals on a circuit board matters. There is no doubt that the electromagnetic signals on rigid-flex PCB are sent out faster than what is obtainable in the traditional PCB design.
This is so because of the excellent electrical performance that enables the electromagnetic signals to run smoothly and quickly in the flex of the rigid-flex PCB.
6. Multiple Use Cases
As more products are under development, there is a need for PCBs to facilitate their operations. Currently, the aerospace industry is in dire need of circuit boards that will power the different aerospace products.
The rigid-flex PCB earned the versatile appreciation because of the multiple applicable and use cases of the board.
The excellent thermal performance of the flexible substrate material is the reason why the rigid-flex PCB is usable in many industries.
Some of the applicable cases are:
- Aerospace
- Automotive
- Military and
- Medical care
7. Minimal Errors
Errors often reduce the success of Printed Circuit Board (PCB) designs despite expertise of the designer and the excellent materials.
Things are looking good on the rigid-flex PCB because of the minimal errors that tend to be made when designing the circuit board.
The major reason why there are fewer errors is because of the replacement of the soldered connections and plugs – which are the foundation of the errors.
8. Simplified Manufacturing Process
You stand to benefit a lot when you are using the rigid-flex PCB as the basis for your Printed Circuit Board (PCB) design.
The reason for this is that the manufacturing process is simplified, especially the embedded rigid-flex PCB design.
9. Increased Reliability
You are confident that the rigid-flex PCB will deliver what you expect every well-designed PCB to offer.
The successful elimination of fragile connectors is one major reason why the rigid-flex PCB can be relied upon at all times.
10. Cost-Saving
If you want to design a high-quality Printed Circuit Board (PCB), you needn’t be told that you have to commit enough resources to get the job done.
But, if you are working on a budget, it doesn’t mean the end of the world. You can rely on the rigid-flex PCB to deliver all you expect of a circuit board.
The cost-effectiveness of the rigid-flex PCB is one unique advantage that sets it apart from the other PCB models out there.
Major Rigid-Flex PCB Rules to Pay Attention To
As much as you have learned about the rigid-flex PCB manufacturing process, we also want you to understand the rules guiding the design.
In light of that, here are some of the important design rules that will help you maximize and make the most out of your rigid-flex PCB production:
1. Use Rounded Traces
After much testing, rounded traces were confirmed to be one of the best ways to design a rigid-flex PCB.
The reason is that if you were using flex traces, bending the flex can cause excessive stretching that may cause the material to tear. Also, acute angles can cause problems during the fabrication process.
However, using rounded traces in the flex areas reduces the potentialities of having wrinkles on the flex when it is bent.
2. Component Placement
Where the rigid-flex PCB components are placed on the board matters a lot and that is why the designer wants to use the rigid-flex PCB design.
Ideally, the components of the rigid-flex PCB should be placed in the rigid areas. When combined with quality soldering, the component placement aids in the removal of hiccups, including tombstoning.
3. How to Use Through-Hole Vias
If you intend using through-hole vias, there is a special of going about that. First, there is a misconception that using through-hole vias in the rigid areas is not ideal. As mentioned earlier, it is a misconception because rigid areas are the best places to apply the vias.
Have in mind that through-hole vias is the best for the job instead of buried vias and blind vias. The latter aren’t good because they trigger inconsistencies in signal flow, as well as cause the components on the circuit board to detach when deployed.
4. Component Footprints
The footprints of rigid-flex PCB imply where the components can be placed or mounted on the circuit board.
While you have many options on where to place the components, you also have to be careful. For example, placing the rigid-flex PCB components across the flex areas can trigger the detachment of the components.
For better placement and mounting, consider placing the rigid-flex PCB components in a way that the entire pad area will be coplanar.
5. Distribution of Traces
The last but not the least is the method of distributing the traces on the circuit board.
Have in mind that the higher the spaces between the traces, the better. Therefore, ensure that the adjacent traces are patterned to run along the through flex areas on the circuit board.
How to Save Costs Using Rigid-Flex PCB
You can save more money than you imagined when designing the rigid-flex PCB. The cost-saving undertones are done by directly saving and indirect saving.
For the direct cost-saving feature, we are looking at how to cut down on unimportant components cutting down on the Bill Of Materials (BOM). Some of the materials that can be removed are:
- Related connector pairs and
- Wire harnesses
In terms of the indirect cost-saving properties, rigid-flex PCB does that by using Surface Mount Device (SMD) machines/components and creating additional spaces to accommodate the components.
Final Words
Rigid-flex PCB presents an excellent way to design Printed Circuit Boards (PCBs) that are highly efficient and cost-effective.
Hire the services of a professional rigid-flex PCB manufacturer/designer to deliver the best PCB design you want.