Rigid vs. Rigid-Flex PCB, How to Choose it?

 Today, almost every electrical manufacturer uses a Printed Circuit Board. However, there are different types of PCBs designed for various electronic gadgets. A Printed Circuit Board or PCB helps to join electronic components together, assisted by cable assembly.  

Even though there are various types of PCBs, the two main types are Rigid PCBs and Rigid-Flex PCBs. Below is an outline that shows the differences and similarities between the two PCBs.  

What is Rigid PCB? 

A PCB can be single-sided, double-sided, or multilayer. Also, you can find single-sided rigid PCB, double-sided rigid PCB, or multilayer rigid PCB. 

A rigid PCB cannot bend. It is solid and inflexible. This is because it is made of solid substrate material. One common rigid PCB is the computer motherboard. 

Hence, a rigid PCB is used in positions it is set to a shape and maintained throughout the remaining life of the device. 

Therefore, once the rigid PCB is manufactured, it cannot be folded into other shapes or modified. Rigid PCBs are different from rigid-flex PCBs. One is inflexible and the other is flexible. Also, their applications are different. 

Most of the hard-solid PCBs in many electronics such as mobile phones and computers are examples of rigid PCBs.  

Different types of rigid PCBs 

Single-sided rigid PCBs are rigid PCBs with metal traces on one side of the board. Single-sided PCBs are perfect for fast production due to their simple design.  

Double-sided rigid PCBs – this board has a dielectric layer on both sides. Their applications differ from low to high temperatures.  

*Multilayer rigid PCB – they feature more than two metal layers. Multilayer PCBs allow designers to build a range of interconnections.  

Advantages of rigid PCBs 

*Lightweight

*Ability to absorb variations

*They are cheaper compared to flexible PCBs

*Low electronic noise

*Ease of diagnostics and repair

*Durable

*Widely used in many electrical gadgets 

Main Material 

The primary material for rigid PCBs is copper-clad laminate or CCL. It is made of reinforcing material. Nevertheless, the materials in the rigid PCB depend on the project's specifications.  

For instance, the adhesive used will differ based on the project specs. Some of the options to consider include Prepreg, Epoxy, and Acrylic.  

Application 

Rigid PCBs provide an increased circuit density and help reduce the board's weight and size. Hence, many electronic companies worldwide prefer rigid PCBs over other types of PCBs.  

Some of the rigid PCB application includes: 

*Computer motherboard – a laptop or computer motherboard is an excellent example of a rigid PCB. It creates a reliable conducting path between GPU, CPU, and RAM.  

*Electronic products – most simple electronic products such as desktop devices, toys, and electronic gadgets have rigid PCB.  

*Telecommunication equipment – mobile devices, hand-help gadgets, and tablets.  

*Other applications include medical equipment, automotive, signal transmission, 3d printing and so on.

What is rigid-flex PCB? 

Rigid-flex PCB is a combination of rigid and flexible circuits. It provides flexibility and strength to the circuit board. The boards are made of flexible layers joined together using a Prepreg bonding sheet.  

The flex PCB is one-sided and rigid PCB is a multilayer PCB in most cases. The rigid part is soldered, and the flex part is used to maintain connections.  

The main reasons for creating rigid-flex circuits are to enhance the circuit capability to transmit signals, eliminate connection issues, minimize weight, free space in the board, and allow consistent frequency performance.  

Different types of rigid-flex PCBs 

*Single-sided Rigid-flex PCBs are simple forms of rigid-flex boards used in various industries. They are easy to produce and mainly applied in digital cameras, mobile phones, and domestic appliances.  

*Double-sided Rigid-flex PCBs – the board is manufactured with two layers of copper and insulation in between. Some application areas include laser scanners, servers, and high-end disc drives.  

*Multilayer Rigid-flex PCBs – these circuit boards are found in complex applications. They are made to meet specialized requirements of aerospace, military, and power generations.  

Advantages of rigid-flex PCBs 

*Comes with several flexible design alternatives

*High component density applications

*Decrease in size and weight of the package. Thus they are an excellent choice for many applications. 

*Dependability in connection

*Minimum interconnections and parts 

Main material 

The mainly used materials for rigid-flex PCBs are substrate materials, conductor materials, and adhesives, among others. Apart from these materials, other optional ones are used in the fabrication of rigid-flex PCBs.  

Application 

Applications of rigid-flex PCBs include: 

*Medical industry

*Aerospace industry

*Manufacturing of military equipment

*Telecommunication industry

*Automotive industry

*Consumer appliances 

Difference between rigid PCB and rigid-flex PCB 

The main difference between rigid-PCB and rigid-flex PCB can be seen in their names. Rigid PCBs are inflexible, while rigid-flex has some flexible and others inflexible parts.  

Flexibility: 

Rigid-flex PCBs have become popular because they easily bend or fold to fit an application. However, rigid PCBs are solid and cannot be folded. 

Connectivity: 

Another reason why most people prefer rigid-flex PCBs is that they offer excellent connectivity between circuit boards. Hence, they are primarily used in laptops and other foldable electronics.  

Reduced weight:

Most electronic device designers look for small and lightweight devices. Happily, rigid-flex PCBs are lighter and ideal for most modern devices. Due to their lightweight, they are used on drones and unmanned vehicles.  

Durability: 

Although rigid PCBs are strong and thicker, rigid-flex PCBs are much more durable. This is because they absorb shocks and vibrations more than rigid PCBs.  

Thus, rigid-flex PCBs are primarily used in weapons, medical equipment, and other equipment that need excellent environmental survivability.  

Resistant: 

Rigid PCBs are at a high risk of warping from chemicals, heat, and radiation. On the other hand, rigid-flex PCBs are more resistant to those factors. Hence, they are found in many automotive applications.     

Final word 

Picking the correct type of PCB is essential because they differ in functionality. Thus, understanding the types you pick is crucial.  

Rigid PCBs are great for simple computers, motherboards, electronic products, and many others. Moreover, they are simple to design and cost less.  

However, rigid-flex PCBs have many benefits compared to rigid PCBs. Due to these advantages, they have become suitable for various applications that need small and light PCBs. 

FS Tech