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Flexible and flex-rigid printed circuit boards are used when an electronic design requires combinations of flexibility, compactness, weight reduction, reliability, or tolerance for movement. The type of PCB you choose depends on the application’s requirements.
There are two major types of circuitry and boards used in industrial and large-scale manufacturing: flexible PCBs and flex-rigid PCBs. Both types differ from traditional rigid PCBs. Flexible and flex-rigid boards combine flexible and rigid materials and technologies in different ways. Flexible circuit boards are designed to provide sufficient flexibility and bending resistance, while flex-rigid PCBs combine flexible and rigid areas.
Flexible printed circuit boards are considered flexible for multiple reasons, but the most obvious is that their circuitry can be designed to match up with the electronic device or core product. Manufacturers are not forced to create a product or casing around the board itself. Instead, they can adapt the board to fit an existing design. This is beneficial when creating components or hardware that feature unconventional designs.
For instance, if total weight, portability, and durability are important considerations for a particular device, conventional boards may not be suitable.
Flexible boards may sometimes need to be adapted to a product’s limitations. For example, the board size may need to be decreased, and circuits may need to be moved or redesigned to match case specifications and dimensions. All circuitry is laid out in a distinct pattern, including components, and then supported by a malleable base material such as copper. Traditional printed circuit boards are also rolled this way, except the materials used are generally heavier and more rigid.
Flexible PCB Pros and Cons:
Reliability: Excellent due to removal of mechanical connectors
Cost: Higher cost than rigid or flex-rigid
Temperature Resistance: Fair
Completely flexible and pliable
Can accommodate any design
Better for rapid movement and high-stress conditions
Flex-rigid PCBs derive their name from the fact that they use a combination of flexible and rigid circuitry areas. Like most printed circuit boards, flex-rigid boards have multiple layers but generally have more than conventional designs.
These additional conductive layers are outlined with rigid or flexible insulation depending on the product needs. Outer layers on a board, regardless of the number of layers, often contain exposed pads or covers for safety. Conductors are deployed for the primary rigid layer, while flexible plated through-holes are used for additional layers, both flexible and rigid.
Some projects call for using traditional rigid technologies and designs. Others have limitations that prevent manufacturers from using these larger, less flexible boards. For instance, mobile and portable devices may be poorly suited to standard boards because of their moving parts, component requirements, and environmental conditions. Mobile devices need to be portable, lightweight, and able to tolerate conditions such as heat, cold, and, at times, moisture.
Flex-Rigid PCB Pros and Cons:
Reliability: Excellent due to reduced need for solder joints
Cost: Lower cost compared to flexible boards
Temperature Resistance: Excellent
Ideal for moderate to slightly higher than normal movement and stress
More flexible and pliable than conventional boards
Long-term reliability thanks to fewer interconnects and components
Requires minimal maintenance
Flexible and flex-rigid PCBs have different capabilities and are suited to different applications. Consider the features your design requires when deciding between flexible, flex-rigid, and rigid boards.
Flexible circuits and their board types are often used when reliability and maximum adaptability are needed. If a circuit needs to be bent during package assembly, flexible design is required. They are also useful when flexing and warping cannot be avoided. Flexible PCBs have also become suitable for more compact and space-limited situations.
Both flexible and flex-rigid boards were expected to see huge growth over the annual periods between 2017 and 2027.
Some things to consider before selecting flexible printed circuit boards include:
Total needed: Flexible PCBs are often best when 20 or more conductors are necessary.
Amount of available space: They work well when space is limited.
Weight: If lightweight boards are needed, flexible PCBs can be considered.
Manufacturing ability: Flexible PCBs are generally best in situations where assembly and manufacturing labor must be limited.
Questions to consider when looking at flexible PCBs include:
How important is reliability?
Are shielding and impedance control methods required?
Do the board circuits need to be dynamic and flexible?
Many computer components rely on flexible circuit boards for operation. The components in hard drives, for example, need to be flexible to keep up with the high speeds at which they write data while remaining relatively small and thin. If operating for extended periods, hard drives can also get hot, meaning the board must be able to withstand high temperatures. Flexible boards in hard drives are described as supporting their long-term operation.
These considerations are not exclusive to hard drives. Computer electronics today tend to be small and thin and can sometimes reach high temperatures. Flexible circuit boards can also be found in consumer electronics applications including televisions, gaming systems, printers, and microwaves.
Modern automobiles use flexible printed circuit boards in many electronic systems. Examples include EMUs (engine management units or computers), anti-lock braking systems, air bag controllers, instrument panels, and dash systems.
Flexible boards can be designed to fit into smaller spaces and spaces with irregular shapes, providing greater flexibility to engineers. Circuits can also be synchronized with other electronics without bulky cable ties or connectors. Weight can also be an important consideration in vehicles because even small additions can make a difference. Flexible boards are relatively lightweight and smaller than conventional parts.
Electronic components in cars also need to withstand demanding conditions. They can be exposed to extreme heat and cold as well as intense vibration during driving.
Smartphones are candidates for flexible circuit boards because they are handheld and need to remain small, lightweight, and portable. A single, thin-layer board is needed to connect and synchronize core components.
Conventional circuit boards cannot be adapted easily to fit inside these small spaces. Since mobile devices are taken everywhere, the hardware inside must withstand changing temperatures and environments too.
Smartphone manufacturers have also begun designing phones with flexible screens, including designs that can bend and roll up. This clearly requires the use of flexible printed circuit board technology. Smartphones are now often designed with water-resistant and waterproof-repelling cases designed to allow the phone to work while and after it is in contact with a liquid. Flexible boards provide the reliability that is necessary for this feature.
Flex PCBs are crucial for pharmaceutical and medical applications, especially when circuits must survive demanding conditions inside the human body.
A swallowable pill-camera device uses super-fine flexible circuitry that must be non-toxic and durable. Patients swallow the pill, allowing doctors and medical professionals to obtain an internal view of body issues or ailments. The pill must be extremely small and able to adapt and flex as it moves through the body.
Researchers have also developed a process for printing circuitry onto flexible organic material that can be implanted in the body to create more realistic prosthetic limbs. This material is described as more flexible than typical flexible PCBs, allowing natural movement without becoming damaged.
Flex-rigid boards are similar to flexible boards with one major exception: they have rigid layers. They require additional materials compared with purely flexible or conventional boards, but the rigid layers also make them more reliable.
When looking at flex-rigid PCBs, consider the following:
Do you have added reliability to make up for?
Are costs and expensive designs less of a concern?
Are extreme temperatures and conditions a factor?
Do you need smaller, shapeable boards yet rigid benefits?
For quite some time, flex-rigid PCBs were primarily used in military and aerospace industries. More recently, flex-rigid board designs and circuitry have been adapted for use in consumer products. Additionally, flex-rigid PCBs may be what you need when motion is necessary while durability is also a factor.
Wearable devices include fitness trackers, smartwatches, smart clothes, rings and jewelry, and medical devices. In the medical field, wearables can help keep doctors informed about patients’ conditions, including heart rates and breathing patterns.
Many of these wearables use flex-rigid boards. A combination of flexible and stiff components is used because these devices need to be small and lightweight, yet they must operate reliably under the stress of everyday activity. The added rigid layers provide additional dependability in demanding applications.
Flex-rigid PCBs help industrial equipment operate under consistently stressful conditions and allow greater flexibility in machinery design. Applications include radio frequency communication technology, power distribution control circuits, and many other types of industrial equipment.
Flex-rigid board design allows sensors to be much smaller and thinner than they could be with rigid boards. This opens opportunities for using sensors in small or irregularly shaped spaces where they could not fit without a more flexible or smaller component
Power distribution control circuits can experience failures because frequent movement and other conditions place additional stress on components.
A flex-rigid board deployment is often used to remedy these issues by providing additional reliability and durability to the control circuit. The flex-rigid design allows the machines in which it is used to remain operational for longer.
Traditional rigid boards can limit the use of such machinery and hold back the component’s potential. Flexible design enables manufacturers to come up with more innovative solutions for equipment performance.
The benefits that flexible and flex-rigid printed circuit boards offer are relevant in many industries. With the growing need for portable, lightweight, and versatile electronics, flexible boards can be a solution for suitable applications.
In the online retail business, shipping and fulfillment warehouses use modern electronics to scan, track, and report on the shipping process. A package or product must be located and selected, marked for shipment, reported as shipped, and then sent through the proper procedure to reach the customer who bought it.
All of this is usually tracked and reported using a portable PDA-like device that needs to be small and portable so workers can use it on the warehouse floor. These devices also need to survive the sometimes-harsh conditions of a busy warehouse. This makes flexible and flex-rigid PCBs suitable for these devices.
Electronic components are becoming increasingly compact. The need for flexibility and versatility is growing. Flexible and flex-rigid PCBs are not ideal in every situation, but professionals recommend using them in the following situations:
Motion and mobility are a requirement.
Flexibility and warping of the board and circuits are major concerns.
Tight spaces, sharp angles, and unconventional form factors are unavoidable.
Weight and portability are major factors, such as in mobile devices and handhelds.
Repair work or maintenance is simply not possible on a regular basis.
The device, product, or board will be subjected to extreme conditions and temperatures.
In some industries, especially in industrial or commercial applications, equipment needs to endure frequent movement, rapid pressure, and extreme conditions. Rigid boards are not always reliable in these circumstances over extended periods. Flexible circuitry can be used where more flexibility is needed to accommodate movement, pressure, and warping.
This is important when machinery and components move at high speeds, because a certain amount of flexibility and warping may be expected.
Sometimes boards and their circuitry must be designed to strict dimensions to match a product or its casing. Under these conditions, the PCB manufacturer must be able to produce circuitry and boards that match the application’s specific requirements.
For readers evaluating flexible or flex-rigid PCB options with Gold Phoenix PCB, these same factors—movement, available space, weight, environmental conditions, and required form factor—can be used as a starting point for defining board requirements.
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