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What Are Rigid Flex Circuit Boards?

Byron / 2021-01-16

Contents [hide]


What Is A Rigid Flex Printed Circuit?


Ideally, rigid flex circuit boards are perfect alternatives for rigid PCBs. Just like the name puts it, these circuit boards are a mixture of flexible and rigid circuits. The strength of these circuit boards is that, being a hybrid, they exhibit the advantages that the rigid and flexible circuit boards have. You will find that most of the rigid flex circuit boards have several layers of flexible circuit substrates joined to rigid boards either externally or internally. Depending on the design of application, designers ensure that the flexible substrates are able to flex. As a result, they are made to have a flexed curve in the manufacturing or installation process. Because of the hybrid element of rigid flex circuit boards, it is possible to fold them or continually flex them while, at the same time, maintaining the shape of the parts that require more support.


Rigid Flex Printed Circuit Types


There are two types of rigid flex printed circuit types. They are the Flex to install and the Dynamic Flex.


  • Flex to install: This is the most  common rigid flex printed circuit. For this one, the board folds once. Another important characteristic of this type of rigid flex circuit is that the flex area remains stable during its use. However, it's important      to take note that there may be some movements when using applications that exhibit high vibrations.

  • Dynamic flex: For applications that require folding and bending repeatedly, the dynamic flex type is the ideal      one. For this reason, the flexible part of the board requires special consideration for it to be in a position to resist wear and tear.      Designers acknowledge that if the right bend radius is considered, these particular circuit boards are able to last for many flex cycles without any problem.


Rigid Flex Printed Circuit Advantages


The combination of rigid and flexible circuit boards gives the hybrid version significant benefits. The advantages of rigid flex printed circuit boards are highlighted below:


  • Security: An application that is able to offer the much-needed security will always offer the best service to customers. The usage of rigid-flex circuits gives secure connections to other components. As a result, they offer stability and polarity.      Moreover, it minimizes connector components. Customers who are looking for circuit boards that offer such opt for the rigid-flex circuits.

  • They are dynamic: if you are looking for circuits that offer dynamism, flexible circuits will give you exactly that. They not only provide you with the freedom of packaging, but also maintain the precise density of printed circuits.

  • Cost saving: The ability to save costs is highly valuable. If you use rigid-flex circuit boards, you are sure to save significant PCB costs and expenses.

  • They have mechanical solidity: The ability of the circuits to have interchanging layers enables them to have a strong foundation. While the rigid boards provide the needed stability, the flexible boards offer the flexibility needed for installation in small areas.

  • Ideal for applications that need multiple rigid boards: Instead of using crowded assemblies containing four and above connected boards, it is better to opt for a single rigid-flex printed circuit board. It will end up being more cost effective.

  • Effective for high-density applications: In the event that assemblies do not have the surface area for the required connectors and cables, it is always best to opt for rigid-flex printed circuit boards. The advantage with them is that they      are able to use space well to address the problem.

  • They are ideal for high-shock and high-vibration applications: The benefit of using rigid-flex circuit boards is that they are shock resistant. This makes them capable of working well in an environment that can easily lead to equipment failure. Obviously, if they are able to survive in an environment that is highly stressful, then they are durable enough and worthy of consideration.

  • They are good for high-accuracy applications: There are applications that are more concerned about high levels of accuracy compared to cost considerations. In such cases, Rigid-flex circuit boards are the best option. For example, in a situation where a connector failure would be dangerous, it is preferable to use a durable rigid-flex printed circuit board.


Applications of Rigid Flex Printed Circuit


There are various applications that are perfectly fit for rigid-flex printed circuit boards. They are able to fit applications in diverse industries. For example, they are used for medical, military, and aerospace devices. They are also used for commercial products. They can be used in electronic devices as well as in aircraft weapon guidance systems. Part of the reason why rigid-flex circuit boards are highly used in industrial applications is because they are capable of reducing the weight of products. It is this quality or characteristic that improves the performance of these devices. That is why rigid-flex printed circuits are widely used in the aerospace, military, and medical industries. In these industries, high performance of devices is a top priority.


Other notable examples of rigid-flex printed circuit boards applications include:


  • Bar code scanners

  • Computer servers

  • CT scanners

  • Pacemakers

  • Cell phones

  • Smart jackets

  • ABS sensors

  • Digital cameras

  • USB and Ethernet


The design, application, and function of rigid-flex printed circuit boards make them to be the ideal solution for industrial and commercial products and applications. A critical analysis of this applications shows that they need powerful components with the ability to fit into small applications.


Materials of Rigid Flex Printed Circuits


The range of materials used for rigid-flex printed circuit boards' assembly is diverse. However, it is worth noting that the materials used depend on the application of the boards. Apart from the area of application, there are also other factors to consider when choosing a material for a rigid-flex circuit board. They include:


  • Cost and budget

  • Duration of the application

  • Method of manufacturing

  • Reliability needs


Here are the most commonly used materials for rigid-flex printed circuit boards:


  • Substrate materials: The common material used for the manufacture of rigid-flex circuit boards is fiberglass. It is mixed with epoxy resin. However, manufacturers acknowledge that fiberglass impregnated with epoxy resin does not offer      the reliable product because it is not able to resist constant vibrations and shocks. Therefore, for highly demanding environments, rigid-flex circuit boards are produced using polyimide and polyester.

  • Conductor material: The most commonly used conductor material for rigid-flex circuit board manufacture is copper. The material is well known for its benefits including: high workability and good electrical qualities. There are two forms of copper foils that are used in these circuits. They are: electro-deposited and rolled copper foil. The foils are available in different weights and thickness. Before they are used for the board assembly, they are usually subjected to surface treatment. In order to improve the longevity of the copper foils, a thin layer of zinc is usually applied. It is notable to      highlight that the foils pass through chemical treatment for the following reasons: increase adhesion, prevent oxidation, minimize bond degradation, and enhance bond strength.

  • Adhesives: Adhesives are instrumental in increasing the longevity of rigid-flex circuit boards. They are used for availing a secure connection between conductor materials and the substrate. During the process of rigid-flex circuit board manufacturing, manufacturers have to decide on the type of adhesive and the thickness that is needed to join substrate and conductor. Here are the most common adhesives used in the manufacture of rigid-flex circuit boards: Polyimide adhesives, polyester adhesives, acrylic adhesives, epoxies, and protective coatings.


Polyimide adhesives are mostly used because of their ability to resist high temperatures. As a result of their high temperature resistance, polyimide adhesives are used in defense and power generation applications. Polyester adhesives are a cheaper alternative and are used in simple rigid-flex printed circuit boards. They have the ability to be heat resistant, thus they are a feasible option for the assembly of intricate boards. Acrylic adhesives have qualities including: good thermal stability, chemical resistance, and easy application characteristics. In addition, they are affordable and also readily available as opposed to other adhesive types.


Epoxies serves as the most common adhesive for rigid-flex printed circuit board manufacturing. They have the ability to withstand elevated temperatures and are able to resist solvents as well as other chemicals. They are also well known for their flexibility and bond firmness. As for protective coatings, the most common coatings used in rigid-flex circuit board manufacturing include: cover lays and cover coats.


Conclusion


It is undeniable that rigid-flex printed circuit boards are widely used in diverse applications and solutions today. Their expansive use is attributed to their superior qualities and benefits. It is because of their benefits that the military and aerospace industries have been using them for more than 20 years now. Designers and manufacturers highlight that the advantages of these circuit boards stem from, among others, the fact that they are a hybrid version of flexible and rigid circuit boards. With innovation being a continuous process, it highly likely that more and more applications of rigid-flex printed circuit boards will emerge.


Rigid flex PCB technology has entered a very mature and stable development stage, PCBASTORE has full set of high efficiency production process, any more problems, The expert in PCBASTORE will make a detailed solution for you.


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