In the indeterministic industry of electronics, the decision of selecting the most suitable printed circuit board or PCB, for any application, particularly sets the base of what can be described as excellency. Amongst all sorts of printed circuit boards, Rigid-flex PCBs and Flex PCBs have gained much importance for their characteristics and use.

The flex PCBs, or the flexible printed circuit boards, or flex circuits were developed in a way such that they embody flexibility and utility. Such boards are preferred as they are derived from flexible substrate material like polyimide or polyester and they can bend, twist, and even fold. Due to this elasticity; Flex PCBs are suitable for use wherever board space is restricted or when the board takes up an odd shape. The Rigid-Flex boards use the best of both worlds- Rigid as well as Flexible as the name suggests; which means they contain a mixture of rigid and flexible parts in their structure. Thus, making itself suitable for some complex electronic operations. This article mainly deals with Rigid Flex vs Flex PCBs, including their characteristics and applications.

Similarities between Flexible PCBs and Rigid-flex PCBs

• Material Composition

Materials used in constructing both the Flex PCBs and Rigid-Flex PCBs are almost similar and are normally flexible curing materials like polyimides or polyester. These materials are used based on high thermal stability, chemical resistance and mechanical stress resistance.

• Design Flexibility

Both Flex PCBs and Rigid-flex PCBs are highly flexible. They can be bent, twisted or folded in some ways which makes it beneficial for the designers to have a compact and small size of the electronic assemblies. This makes them suitable for use in consumer appliances for complicated medical uses.

• Reduction of Weight and Space

In general, both Flex PCBs and Rigid-Flex PCBs affect the factorial reduction of weight and space of the equipment positively. Eliminating the need for multiple rigid boards and connectors, these PCBs play a significant role in minimising the size and weight of the devices.

Differences between Flexible PCBs and Rigid-flex PCBs

• Structure and Composition

There are Flexible circuits where all the layers are flexible and the ability of the board to flex is not restricted in any way. They have no restricted parts and any of them may consist of flexible parts only, thus it is flexible to the extent.

Rigid-Flex PCBs have both flexible circuit parts as well as rigid circuit parts. Owing to that, Rigid-flex PCBs show excellence in the domain of offering flexibility of a Flex PCB along with the mechanical properties of a rigid PCB.

• Application Scope 

The most common use for Flex PCBs is in wearable devices, flexible displays and some automotive products because they are fully flexible; they can be formed in a variety of patterns and used in rather restricted spaces.

Rigid-flex PCBs are used in complex circuits where flexibility as well as rigidity are required. These are ideal to use in aerospace, military and advanced medical device applications ascribed to their high mechanical strength.

• Durability and Reliability

While both kinds can fight mechanical stress to a certain extent, Rigid PCBs are more commonly applied in applications where performance and dependability form the core requisite. The rigid sections help in the protection of the board from physical damage that may result from installation or usage, particularly where stress load is expected to be applied. While flexible PCBs have very high reliability, by constant flexing and adverse environmental impacts they prove to be fairly sensitive and can be affected by fatigue.

• Cost and Fabricating Complexity

Flex PCBs are relatively more convenient to fabricate than Rigid-flex PCBs. They are made through fewer production cycles, this could be advantageous as it reduces the cost of manufacturing, especially for relatively basic designs.

Rigid Flex boards are more intricate to fabricate when compared to other printed circuit boards due to their construction- combining of flexible and rigid material, accurate alignment of layers, and sophisticated routing which makes this whole process quite costly.

• Assembly and Handling
  
  Flexible PCBs are quite tricky to handle during the assembly process due to their extensive flexibility. On the contrary, Rigid Flex is easier to handle given its rigid attributes.

The following table gives a clear view of the Rigid Flex vs Flex PCBs based  on various characteristics:

Comparison between Flexible PCBs and Rigid-flex PCBs

Conclusion

Rigid-flex PCBs are easier to use as compared to Flexible PCBs since a portion of the comprehensive circuit is made rigid to facilitate during assembling. This may assist in going a long way in the capabilities of reducing the probabilities of potential destruction and also aid in reducing the time that is taken in the production process. Flex PCBs have paramount flexibility Thus, the usage of these types of PCBs can apply to compact and dynamic forms.

Rigid-flex PCBs and Flex PCBs can be used depending on the general functioning criteria of the system. Therefore, the printers which possess the favourable characteristics of flexibility and rigidity are often referred to as Rigid-flex PCBs and can be used in circuits that can have many variants in their shape.

For engineers and designers of the circuit boards involved in the engineering and designing of the circuit boards to choose the most suitable PCB for the desired application, they should have adequate information on Rigid Flex vs Flex PCBs. Therefore it can be appreciated that the selection of the sort of a PCB can enhance the equilibrium of the design, the performance and the cost of a specific type of the PCB, which would be related to the topic area of the application.