Rigid-Flex PCB | Printed Curcuit Board

When the two worlds of “rigid” and “flexible” meet, a rigid-flex PCB (RFPCB) is created. It combines the robustness of a traditional rigid PCB with the versatility of a flexible circuit (FPC), enabling entirely new possibilities such as miniaturization and increased reliability in applications with continuous movement. Rigid-flex PCBs add a third dimension to assemblies without sacrificing ease of processing. By integrating flexible circuits directly into the rigid structure, the need for connectors is reduced. This not only saves space and connector costs but also delivers significantly higher reliability compared to most connector solutions. While rigid-flex PCBs may have higher unit costs than standard rigid or flexible boards, their advantages – space savings, reduced assembly steps, improved reliability, and lower long-term costs – often make them the more cost-effective choice overall. With manufacturing in Bangalore, India, and long-standing expertise from Germany, Leiton supports you in designing and producing rigid-flex PCBs tailored to your specific requirements, from prototypes to series production.

Rigid-flex PCBs – Clearing Up Myths

Many developers hesitate when it comes to designing a rigid-flex PCB. Often, uncertainty about specific design rules and the assumption that rigid-flex PCBs are “too expensive” hold them back. In reality, both concerns can usually be dispelled quickly. From a design perspective, there are only a few additional points to consider compared to rigid or flexible PCBs – and our experts are here to guide you. At Leiton India in Bangalore, as well as through our global team, we provide straightforward consultation – often just a quick call is enough to clarify key questions. For cost estimation, even rough project details are sufficient, so you don’t waste time exploring a rigid-flex option without price orientation. And when it comes to true cost comparisons, it’s important to look beyond the PCB itself. Rigid-flex designs can significantly reduce or even eliminate the need for cables, connectors, and additional assembly steps – making them not only technically reliable but also cost-effective at the system level.

The Rigid-Flex PCB (RFPCB), also known as a rigid-flex circuit board, is a hybrid of conventional rigid boards and flexible circuit boards. In this design, the flexible circuit layers are integrated into the rigid board, allowing them to extend directly from the rigid area. As a result, a rigid-flex PCB serves as a stable support structure and provides flexible connections for electronic components in three-dimensional or movable applications.

Advantages of Rigid-Flex Printed Circuit Boards

The advantages of rigid-flex PCBs are truly versatile:

• 3D electronic interconnection
• Direct connection between rigid and flexible boards
• Reduction of connectors (cost and space savings)
• Increased reliability by minimizing connectors (eliminating loose connections)
• Integration of multiple boards into a single assembly
• Miniaturization through higher compactness
• Dynamic load capacity of flexible areas
• Stability for complex components on rigid sections
• Diverse and flexible combinations of multiple rigid and flexible PCBs in an RFPCB

As the name suggests, flexible circuit boards FPC are inherently flexible. While certain areas can be partially stiffened, the conductive traces and the entire substrate are primarily designed to be flexible and bendable. Flexible PCBs are typically 1- or 2-layered, with relatively simple complexity. They are often used for interconnecting electronic components rather than supporting complex circuitry. This is primarily because flexible multilayer PCBs with more than 2 layers become less flexible and lose their inherent advantages. Moreover, complex designs with multilayer routing usually require additional components that should not be placed in flexible areas or should be stabilized with stiffeners. Therefore, for more complex designs with flexible requirements, rigid-flex PCBs are a suitable choice.

For cost-sensitive projects, flexible PCBs with stiffeners can serve as an alternative to rigid-flex boards. We are happy to provide early-stage guidance on what to consider in such cases.

The manufacturing process of rigid-flex PCBs can become extremely complex depending on the design. However, in general, it is initially similar to that of normal multilayer PCBs. To produce boards with both rigid and flexible areas, additional and sometimes elaborate steps are required. Firstly, the areas that will become flexible must be separated from the prepregs (PP) that bond the layers of the multilayer PCB. So the prepregs are pre-cut separately, unlike in standard multilayers where they are fully pressed over the entire surface.

When planning the layer stackup, it is crucial to consider that the flexible layers span the entire construction of the rigid portion.

Another significant difference in the manufacturing process of rigid-flex PCBs is the subsequent process of milling or “depth-routing”. The partially bonded flexible layers are milled or routed to a depth just before reaching the flex layer at the points where the prepreg was removed prior to pressing. This process gives the rigid-flex PCB its characteristic feature of directly connecting rigid and flexible areas.

Rigid-flex PCBs can become highly complex, and thus, the differences mentioned above are general and simplified distinctions.