High-performance flex and rigid-flex PCBs

The rigid-flex PCB design features a combination of both rigid and flexible board technologies. In most rigid-flex boards, layers of flexible circuit substrates are attached to one or more rigid boards internally, externally or both, according to the application's design specifications. Typically, rigid-flex printed circuit boards are produced with flexible polyimide material on copper cladding substrate which is connected to the rigid board. The layers of the flexible part of rigid PCBs are usually built with padded through holes that secure interconnectivity between them.

Advantages 

Rigid-flex PCBs offer copious advantages, including being lightweight, easy to assemble and repair, as well as enhanced reliability, performance, and flexibility of electronic devices. These and more are discussed subsequently:

Compact Size

Electronic devices are increasingly designed to be smaller in size and more flexible. The versatility of rigid-flex PCBs makes them amenable to bending and folding to fit into smaller devices, with the proper connection of miniature components. This miniaturization also makes it lightweight.

Increased Reliability

Since solder joints and board-to-board connectors are reduced, there is less chance of connection impedance. Also, the connection of the attached rigid and flex layers is secure and reliable, which ensures less circuit failures.

Space Efficient

Because of the interconnecting circuit built into the flexible substrate, there is more space on the rigid-flex PCB to route the traces around. This makes the board suitable for applications with compact designs as they don't provide much room for wire harnesses and high-profile connectors.

Reduced Cost

Even though rigid-flex PCBs are more expensive than normal rigid PCBs, it is more cost-effective in terms of assembly charges. Rigid-flex PCB assembly requires less material due to the smaller size, and fewer connections. The fewer parts and connector assemblies reduce the purchasing and assembly costs of the final product and increase revenue. This means that overall manufacturing cost from assembly and logistics is significantly reduced with the rigid-flex PCB.

Ease Of Testing

The already interconnected subcircuits of the rigid-flex PCBs make it easy to perform automated testing. This testing allows manufacturers to eliminate connectivity issues before the components are assembled, thereby preventing needless wastage and expenses.

Design Flexibility

3D design and multiple layers of flexible circuits, make the rigid-flex PCB highly flexible to be able to fit into small devices. This way, devices are not restricted to specific PCB designs as it is with rigid boards because rigid-flex boards have an impressive bend radius and so can be flexed into various applications.

Resistance to High Temperature and Harsh Conditions

This type of PCB can withstand high temperatures since polyimide which has high thermal stability is used in its design. Also by combining the best features of both rigid and flex boards, it possesses considerable resistance to radiation, harmful oils and chemicals, as well as extreme shocks and vibrations, and other severe industrial conditions. This makes it perfect for devices that are likely to be subjected to excessive movement and vibrations during their use.

Disadvantages

The rigid-flex PCB might have lots of merits, but it also has quite a few deterring disadvantages that manufacturers weigh with serious consideration before diving in. For one, it has a long and difficult production process, so it is necessary to invest in more materials and manpower to gain some assembling speed, incurring costs.

If there is a need to make adjustments to the actual design during the testing phase, it is notable difficult with a rigid-flex board, as one might need to go back to the Gerber programming to correct the error. This translates to added expenditure and time since it is practically reworking the entire design. It is also known to have a low yield rate. [3]

Rigid-Flex PCB Applications

Several characteristic and functional benefits of Rigid-flex boards, such as reduced interface connections, minimal packaging weight and size, and resistance to extreme conditions make them widely sought after for application in the commercial, industrial and domestic divisions. Apart from small consumer products like phones and multimedia players, they are used in the following industries:

Medical Industry: for devices like pacemakers, cochlear implants, handheld monitors, imaging equipment, drug delivery systems, wireless controllers, and others.

Aerospace: this application produces devices such as radar equipment, GPS, radio communication systems, control tower systems, sensors, noise, and vibration testing systems, motion sensors, and environmental and climatic test chambers.

Telecommunications: for this sector, there are base stations, handheld units, communication satellites, wireless communication systems, signal processing systems, transmission media, routers and servers, online signal expansion systems, and so on.

Consumer Appliances: this is a common application for rigid-flex boards, seen in ovens, TVs remote controllers, washing systems, lighting systems, solar power systems, UV water purifiers, electronic irons, etc.

Automotives: this industry is not left out, applying rigid flex for products like electronic control modules, transmission controls, LCDs, comfort control units, as well as air conditioning, music, traction control, entertainment, and navigation systems.

Military Sector: rigid-flex printed circuit boards bear significant application here for the production of weapons guidance systems, communication systems, GPS, aircraft missile-launch detectors, surveillance or tracking systems, and many others.

Manufacturing Industry: In this sector, rigid-flex boards are applied for test equipment, electrical switches, industrial automation systems, control panels, industrial air conditioners, and CCTV surveillance systems, among others.