PCBs (Printed Circuit Boards) use discrete wiring to connect electrical components and create a functional and complete device. A simple PCB can simply consist of a couple of layers or sheets of copper integrated circuits, but PCBs are most likely to possess many layers of circuits. These layers of copper circuitry are required by the PCB designer in “routing” every circuitry that exists between the various components – where several layers of circuits may not be enough to complete the design of the circuitry and make all the required connections.
While all Printed Circuit Boards serve similar basic functions as the substrate used for electronics components, the materials made use of In the construction and design of these PCBs are what makes them different. PCBs are designed for specific and suitable applications. There are three classifications of PCBs namely Rigid, Flex, and Rigid-Flexible PCBs. This article provides a clear explanation of the fundamental difference between a Rigid PCB and a Flex PCB.
Difference between Rigid PCB and Flex PCB?
The most prominent difference between a flex PCB and a Rigid PCB can be easily deduced from their respective names: A Rigid PCB is not flexible, whereas a flex PCB can be shaped or bent to fit into a given system. Flex circuits when correctly designed can be flexed also for several cycles repeatedly with no failure. The increased flexibility of flex PCBs comes typically at a greater cost, however, they are important for applications that required limited space, such as medical devices, consumer electronics, automotive and space applications
Rigid PCBs are common, especially as a result of their lower cost relative to flex PCBs. In traditional electronics like consumer electronics with a greater availability of space, manufacturers can be economical by making use of Rigid PCBs. However, flex PCBs are starting to take a larger part of the market share from non-flexible or rigid PCBs as a result of their adaptability and among several advantages like:
- Flexibility: Flex PCBs can be easily twisted, bent, and even folded to fit into the end or finished application. This gives the manufacturer the flexibility of having the circuitry fitted into the end device, instead of the endpoint device being designed around the circuitry. For instance, flex circuits are perfect for wearable devices, foldable mobile phones, and cameras. Rigid PCBs are hard and don’t offer such flexibility required in flex circuits applications.
- Connectivity: Flex circuits allow a better connectivity between various electronic components, circuit boards, and user interfaces in the packaging of electronics. Flex PCBs can also create connectivity in applications (dynamic flexible applications) where the flex circuit is required to flex continually over the device’s life cycle. These types of flex circuits are widely used in laptops PCs, display connectivity, and foldable electronics.
- Minimal Weight: Circuit boards with minimal weight produce an end product that is lighter. In present-day electronics market, this is essential because small, light-weighted devices are preferable to heavier electronic devices by electronics designers and consumers. This feature makes flex circuits to be perfect for drones and unmanned vehicles.
- Durability: Although rigid Printed circuit boards are generally stronger and thicker, flex printed circuit boards absorb vibrations and shocks better and effectively compared to rigid printed circuit boards. This makes flex PCBs more reliable with a long-term shelf life and functionality. And are extensively used in missile guidance systems, satellites, weapons, medical electronics, and various applications that require great environmental viability.
- Heat Resistant: Rigid printed circuit boards are likely to be damaged from heat, radiation, or chemicals; however, flex printed circuit boards are more resistant to heat and other damaging environmental conditions. This is the reason why flex PCBs are currently and widely used in automotive electronics.
- Manufacturing Process: Flex PCBs have flex circuit overlay and are manufactured using a process known as cover lay to protect the flex PCBs circuitry (from external or apparent damage)rather than using a solder mask. Flex PCBs are generally made using Polyimide. The sheet of Polyimide has covered heat adhesives for total protection. The adhesives fill every gap on the PCB which produces a smooth flow.
- Strength of Material: The thickness and strength of rigid printed circuit boards come typically from glass. This makes rigid PCBs to be reinforced. Flex PCBs don’t provide a similar level of material strength, but instead make use of a base material (e.g. Polyimide) that is more flexible.
- Protection: Flex PCB uses circuit overlay for protection, while rigid PCB uses smolder mask for protection.
Are Rigid PCBs Different From Flex PCBs?
Rigid PCBs are not completely different from flex PCBs. There are certain similarities between both PCBs as well. A major similarity between flex PCBs and rigid PCBs is the two PCBs perform similar functions. In addition, both PCBs are built in similar ways; nevertheless, flex PCBs make use of flexible circuit coverlay for protection, while rigid PCBs use solder mask for protection.
The manufacturing and designing of rigid PCBs slightly differ from flex PCBs. As a PCB designer or manufacturer, you must be careful when designing either PCBs and ensure you follow the requisite design rules. These include minimum space, trace width, minimum hole size, design thickness, and several other factors.
A device can be designed with both PCBs In it. A laptop PC is a common device with both rigid and flex PCBs. Some parts of the laptop require rigid PCB for its functionality while the other parts require flex PCBs for the smooth and correct transfer of information.
The PCB market which consists of two main types of PCBs namely rigid PCB and flex PCB is estimated to reach about $81 billion in 2024. The differences in both PCBs have wide applications in mobile phones, consumer electronics, wearable devices, space and automotive applications, missile guided systems, weapons, toys, and others. An understanding of the differences in rigid and flex PCBs is of great significance to designers and manufacturers in the PCB industry.
Rigid and flex PCBs have their respective applications and benefits. Flex PCBs design might be quite complex than rigid PCB designs, however, when strength and connectivity are required rigid PCBs are of greater importance. Newly produced bendable mobile phones and smart technology makes use of flex PCBs.