Common Rigid-Flex PCB Configurations

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Rigid-Flex PCBs differ from conventional printed circuit boards in combining rigid and flexible circuit substrates in a single assembly. This design approach gives the designer significant advantages in terms of performance, appearance, and reliability. These advantages make rigid flex PCBs an attractive alternative to conventional rigid and flexible boards, particularly when designing applications that require durability, ruggedness, and resistance to flex fatigue.

rigid-flex pcb fabrication

Rigid flex PCBs can often be manufactured in some configurations or rigid flex combinations,  each with its strengths and weaknesses. This guide explains the configurations and their use for particular applications.

Rigid Flex PCB Configurations 

1. Rigid Flex Single Sided PCB

Rigid flex single sided PCB is the most common type of circuit board used today. It is a single sided PCB with a rigid component, usually made of FR4 (glass epoxy), on one side and a flexible component, usually made of polyimide film, on the other side. The rigid component can be solid, or it can have cutouts that allow it to flex during operation. The flexible component allows you to bend your board in half without damaging the circuit traces or components on either side of the board.

The main advantage of rigid flex single sided PCBs is that they are relatively inexpensive compared to double sided boards with the same amount of copper. They are also easier to manufacture because they do not require special handling during assembly or testing due to their rigid nature. This makes them ideal for prototype manufacturing, where space is limited, and cost must be kept low.

Rigid flex Boards can be used for all types of electronic applications like power supplies, motors, battery packs, and other similar applications that require a rigid structure to support them. They can also be used for high-frequency circuits since they have a low dielectric constant compared to other types of PCBs, made out of epoxy glass laminates with no copper foil on either side.

2. Rigid Flex Double Sided PCB

Rigid flex double sided PCB is a thin, flexible printed circuit board with a rigid core and flexible circuits on both sides. The flexible circuits allow the board to bend up to 90 degrees in all directions. Double-sided PCBs can be used for anything from simple PCBs for home projects to complex ones that require several layers and even special functions like RFID tags or connectors for sensors. The rigid flex double sided PCB utilizes a combination of rigid FR4 material on the top side and flexible FR4 material on the bottom side. The electronic components are mounted on the rigid side of the board, while traces are etched on both sides to allow for flexibility.

The main difference between rigid flex double sided PCBs, and traditional rigid PCBs is that they use flexible copper foil instead of rigid fiberglass boards to form the circuit pattern. The layer structure of rigid flex double sided PCBs consists of an interlayer insulating film sandwiched between two copper foil layers. Depending on customer requirements, the substrate can be made from FR4 or other materials. It can be fabricated in any shape or size as long as there is space on its surface for soldering components onto it. It consists of two separate layers that have been laminated together with an insulating material.

Rigid flex double sided PCB assembly is widely used in smart devices such as mobile phones, laptops, and wearable electronics. It is mainly used for the integration of electronic components such as sensors and antennas. In addition, it also provides flexibility in mechanical design and integration of various sensors, which allows designers to use various applications without worrying about whether their products are damaged when they are bent or squeezed during use.

3. Rigid Flex Multi Layer PCB

Rigid flex multi Layer PCB is a new technology that is an evolution of rigid flex single sided PCBs. Rigid flex multi layer PCBs are made with the same manufacturing process as single sided rigid flex PCBs, but instead of having one layer, they have multiple layers. These layers are stacked together using a special adhesive and then laminated to form a multi-layer board. As a result, rigid flex multi layer boards can be used for different types of applications, including high density interconnections and high frequency circuits. The main advantage of using this type of board is that it can be customized according to your needs.

Rigid flex multi layer PCBs consist of three main layers:

  1. Top Layer - The top layer is the rigid part of the circuit. It consists of copper traces and can be printed with any standard circuit pattern. If required, the top layer can be used as a heat spreader or ground plane.
  2. Bottom Layer - The bottom layer is flexible and can be made from either FR4 or Rogers 4003 material, depending on your application requirements. The bottom layer is connected to the top layer using vias placed at regular intervals along its length, typically every 0.1". These vias allow electrical connections from the top to bottom layers without compromising the board's flexibility.
  3. Core Layer - This is an optional layer that can be added between the top and bottom layers for added strength and rigidity if your design requires it. Moreover, you can stack multiple layers on top of each other to create multi-layer assemblies such as laminated plastic cases for electronic devices, such as smartphones, without having to worry about damaging your circuit design if you need multiple circuits in one case.

The rigid flex multi layer PCB can be bent in various shapes, but it does not have the flexibility of a single-sided flexible board. It is used in various applications, including telecommunications and automotive.

Final Verdict

When it comes to electronics, a rigid flex circuit is often considered an alternative to standard PCBs. But designing with a rigid flex circuit is not just choosing between one or the other; each configuration has its capabilities, features, and shortcomings. It is important that you understand all of these differences when designing with rigid flex PCBs to ensure your product works as desired. Hopefully, this guide must have helped you. Make sure to check out Hemeixin's design guidelines for rigid flex PCBs.

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