Printed circuit boards (PCBs) connect electrical components together using discrete wiring, resulting in a complete and functional unit. PCBs can be as simple as one or two layers of copper circuits, but are far more likely to have many layers of circuitry. The layers are necessary for the designer to “route” all of the circuits between the components – where one, two, or even eight layers of circuitry may not be enough to complete their design and make all of their connections.
While all circuit boards perform the same basic function as a substrate for the electronic components, the design and materials of their construction are the key distinguishing points. Circuit boards are custom-tailored to their particular application.
The three main types of PCBs are rigid boards, flexible circuits (or flex), and rigid-flex. This blog post will provide a clearer understanding of the differences and similarities between each type of PCB.
The most notable difference between rigid PCBs and flex PCBs can be inferred from their names. Rigid PCBs are inflexible, while flex PCBs can be bent or otherwise shaped to fit inside the designated system. Flexible circuits, when designed correctly, can also be flexed for hundreds of thousands of cycles repeatedly without failure. The increased versatility of flex boards typically comes at a higher cost, but they are essential for applications with limited space requirements, such as consumer electronics, medical devices, space and automotive applications.
Rigid circuit boards are very popular largely due to their low cost. In conventional electronics, and particularly in consumer electronics, with greater space availability, manufacturers can save significantly by using rigid circuit boards. However, flexible PCBs are beginning to siphon market share from rigid circuit boards due to their versatility, among other advantages, such as:
- Flexibility. Flexible circuits can be bent, folded, and even creased to fit the end application, giving the designer the ability to have the circuitry fit the device, rather than the end device being built around the electronics and circuit boards. Flexible circuits are ideal for wearable electronics, for example.
- Connectivity. Flexible circuits provide greater connectivity between other circuit boards, electronic components and the user interface in electronic packaging. They can even provide connectivity in dynamic flex applications where the flexible circuit needs to flex continuously over the life of the device, so they are used extensively in laptop computers, foldable electronics, and display connectivity.
- Reduced weight. A lower-weight circuit board results in a lighter end product, which is essential in today’s electronics market where small, lightweight devices are preferred by electronic device designers and consumers. Flexible circuits are ideal for unmanned vehicles and drones, due to their very light weight.
- Durability. While rigid PCBs are typically thicker and fairly strong, flex PCBs absorb shocks and vibrations much more effectively than rigid PCBs. This contributes directly to long-term reliability, product life and functionality. Flexible circuits are used extensively in medical electronics, missile guidance systems, weapons, satellite and other applications requiring excellent environmental survivability.
- Resistant. While rigid PCBs are at risk of damage or warping from heat, chemicals, or radiation, flex PCBs are much more resistant to these detrimental environments. This explains their wide application in today’s automotive electronics.
With the differences between rigid and flexible PCBs in mind, we will now compare these PCB types with their hybrid counterpart, the rigid-flex PCB.
As its name suggests, the rigid-flex PCB is a hybrid of both rigid and flex PCBs, and features the great qualities of both while eliminating many of their individual limitations. A rigid-flex PCB incorporates flexible materials in conjunction with rigid materials by layering flexible circuit substrates inside of the rigid circuit board materials, ultimately combining the versatility of flexible circuits with the stability, strength and circuit routing densities of rigid PCBs. This hybridization opens up a spectrum of possibilities for much more complex and mechanically challenging designs.
Rigid-flex PCBs are a means to streamline the electronic design, by eliminating flexible cables, connectors and discrete wiring. The electrical performance of a rigid flex PCB is enhanced compared to its counterparts, because the circuits are integral to the overall construction. All of the electrical and mechanical connections are internally contained within the rigid-flex PCB, providing the electronics designer with much improved service reliability and electrical performance.
While they do typically arrive at a higher cost than their flex and rigid board counterparts, the reliability, weight reduction, strength and space-saving advantages of rigid-flex boards are often ideal in certain applications, and outperform any other electronic packaging techniques. Ultimately, rigid-flex PCBs provide the best benefits of rigid and flex PCBs in one solution. Applications where rigid flex PCBs excel are:
- High-reliability applications. If an assembly will be exposed to excessive or repeated shock, or high vibration environments, connectors with flexible cables are more likely to fail. Rigid flex PCBs provide great reliability even when subjected to extreme vibration and shock applications.
- High-density applications. Within a small enclosure, it’s sometimes impossible to accommodate all of the cables and connectors that an electronic PCB design would require. Rigid flex boards can fold into very small, and very thin profiles, offering substantial space savings in these instances.
- Five or more rigid boards. If your application will ultimately involve five or more rigid boards connected to one another with flex cables, an integrated rigid flex solution is often the optimal and most cost-effective choice.
The applications of rigid-flex PCBs are extensive, and their implementation is growing across industries ranging from automotive, medical, military, and many more.
Based in Minneapolis, Printed Circuits is centrally located in one of the world’s largest flexible circuit manufacturing hubs. With more than 40 years of manufacturing experience in advanced circuitry, we pride ourselves on the quality and precision of our rigid-flex products and services. For more information about rigid, flex, or rigid-flex PCBs for your application, contact us today to learn more.