Rigid-flex PCB boards are one of the most widely used printed circuit boards for industrial applications. Their versatility is one of the main reasons for their popularity. They are made of a mix of rigid board and flex circuits, which means that the manufacturing method is similar to that of rigid board, but the circuit has a flexible circuit layer running through it. Their main purpose is to act as a rigid board while also meeting product specifications, making it suitable for mounting on the circuit board.

A well-designed rigid-flex board can withstand thousands of bending cycles without failure. This property of rigid-flex PCBs makes them ideal for flexing applications, also known as dynamic flexing. However, these boards are a bit expensive due to their wide range of uses and complex designs. Mentioned below are some ways to reduce the cost of rigid-flex PCBs.

Ways to Reduce Rigid-Flex PCB Cost

Simplify the Design
One way to reduce the cost of rigid-flex PCBs is to simplify complex designs and remove unnecessary materials. Minimize the number of circuit layers by cramming them into a single layer. Don’t go overboard on the number of layers if you can avoid it. Reduce the thickness of the material to be mounted on the board. Using thicker materials results in using more substance, which increases the overall cost. Customize the design to your needs by removing unnecessary elements from the board. This means more efficient, simpler circuits that are easier to use while reducing expenses.

Choose materials carefully.
The raw materials used to make rigid-flex PCB boards cost a little more than traditional PCBs. There are some modifications and changes in the manufacturing process of rigid-flex PCB boards, which makes them expensive. Factors that affect materials include mechanical properties, thermal properties, signal performance, thermal reliability, and thermal reliability.

Mechanical properties: The variation in the board’s bending strength, flexural strength, shear strength, and thickness play a big role in determining the overall cost of the board. Use materials based on the needs of the board. If you want a more rigid board, use a stronger material. However, if you need a more flexible board, a less strong board will be a cheaper but better choice.

Heat transfer: Without good heat transfer properties, the rigid-flex PCB board will affect functionality; however, if your design does not require optimal thermal conductivity, choose a nice, less expensive heat transfer system. Don’t spend all your money on a system that will not bring any real advantages to your project, but will just waste money. High temperatures affect thermal temperatures. However, the materials used to construct rigid-flex PCBs can withstand high temperatures. That is why rigid-flex PCBs are essential in applications that require high temperatures.

Signal Performance: The signal performance of rigid-flex PCBs can be adversely affected by various properties of the materials they are produced from. Infrared radiation, coupling, and Raman scattering are some of the properties that affect signal performance. Choose the appropriate material that fits your design and meets the requirements rather than going for a fancy device.

Thermal Reliability: Temperature variation is another major factor that affects rigid-flex PCBs. A decent board should be able to withstand temperature variations. The usual range that a typical rigid-flex PCB should be able to withstand is -40 degrees Celsius to +140 degrees Celsius. However, if your design does not require such a wide temperature range, you can customize it to a lower range to reduce the overall cost.

Temperature Reliability: Using the right material ensures that the PCB board can handle temperature variations as per the requirements of the board. While choosing the design of the board, it is imperative to choose the right options to enable your device to function as per the size of the board and your budget.

Therefore, if you are looking to create more efficient designs for greater output, or are looking for ways to reduce the cost of rigid-flex PCBs, it is important to choose the right materials for your PCBs.

It is not a wise move to spend too much on materials that will not bring any significant benefits to the board. Instead, use conventional materials that will meet the needs of the task.

Adjust the assembly to your requirements

The soldered components on the circuit board make up the PCBA (Printed Circuit Board Assembly) or PCB assembly. Once the required equipment is assembled, the assembly process of the PCB can begin. One of these methods is wave soldering and hand soldering.

Wave soldering is a PCB assembly process in which solder is placed in a high-temperature tank in the form of solder bars. The solder is kept molten in the tank and waves are created at high temperatures, the range of which depends on the type of solder. Tin\lead (Sn\Pb) solder has a lower melting point than lead-free solder.

The assembly process includes inserting electronic components, applying flux, preheating and wave soldering, followed by cleaning and testing. Once any failure is detected (pinhole or air hole wave soldering), it is sent for rework, which is usually done manually by the manufacturer. Manual soldering is performed in repair shops or workshops with less workload.

You can minimize the cost of the assembly process by taking the following steps:

Reducing the number of layers reduces the number of pre-stuck layers required to hold the board together.

Flexible laminates are much more expensive than rigid laminates because they are sparsely constructed of the final rigid-flex board. Therefore, limiting their number can reduce overall costs.
For a specific thickness, use rigid board laminates instead of additional board layers or flexible laminates.
Only the impedance values ​​that form a significant part of the design are modeled and tested.
All flex arms can be terminated to obtain the lowest possible cost.
The configuration of the PCB can be simplified, optimizing the design, size, shape, etc. Additional plating tanks will reduce yield.
It is always a good practice to include the manufacturer in the product design to produce optimized PCBs, thereby reducing the need for redesign.
Use vias that are not blind or buried. Round holes and loose tolerances are economical choices.
Surface mount (SMD) is recommended. Plated through-hole components require trimming or forming before mounting. Manufacturers can do this manually or by machine. Using SMD reduces the number of processes involved because it uses a placement machine.
All of the above techniques help reduce rigid-flex PCB costs, but the specific application situations vary. Sometimes, the money saved on split circuit or keyboard layers may translate into higher assembly costs. Each situation is unique and should be handled accordingly.

Improve Manufacturing Yield and Reduce Overall Cost

Manufacturing techniques vary. Today’s technology involves using fiberglass epoxy (FR4) as the outer rigid board and using a solder mask to protect the circuit pattern. Dimensional tolerance accumulation affects the circuit pattern. Therefore, embedded technology can be used to reduce this. They are printed by embedding flexible circuit units into the inner rigid board and going through a build process. The flexible circuit is embedded in the rigid board and then layered. Rigid-flex PCBs are more compact, so less material is required. It increases revenue. Therefore, you can use rigid-flex PCBs to reduce the overall manufacturing cost of the final product.

There are challenges that come with the manufacturing process. The flexible portion of the PCB may bend slightly. This means that you should consider the mechanical stress on the material. Be careful with the bend line or bend area to prevent premature failure. Avoid using vias and pads in the flex area as mechanical stress can weaken the pad. The wires must also be routed perpendicular to the bend line to ensure stability. You can add dummy traces to reinforce the bend area using existing traces. The flex area should have a shaded polygon as a ground plane instead of a solid copper plane. This can be done easily using OrCAD PCB Designer which is optimized for flex-rigid design.

By considering all the mentioned steps, you can reduce the rigid-flex PCB cost of the entire project while increasing the manufacturing yield.

Rigid-flex PCB boards have a very wide range of uses in the industry due to their versatility and ability to cater to different applications. However, all that glitters is not gold as they are expensive to manufacture. However, there are a number of ways you can reduce the overall cost including simplifying the design by eliminating redundant elements, choosing the right material that meets the design requirements, and selecting adequate cost-friendly assembly procedures. Not over-investing in unnecessary high-end technologies that are not supported by the design is one of the key steps to ensure that the developed rigid-flex PCB board fits within the budget.