lexible Printed Circuit Boards (FPCBs) offer a highly efficient interconnectivity

solution that can bend, form and reform the products they are used in. As a result, FPCBs are increasingly being deployed for an ever-widening range of reasons across an ever-growing range of products. But don’t be fooled into thinking they

are just used in devices with complex circuitry. Low-tech applications, such as under-the-counter LED lights, often rely on FPCBs because they can make installation so much simpler. You would also be wrong in thinking

they are just used in the wearables market or for products that need to flex in use. There are, in fact, many applications where flexible circuits are required to fit into the device rather than to flex in use. These static applications usually use the less expensive Electro Deposited (ED) copper rather than the more dynamic Rolled Annealed (RA) copper. Growing at a rate of nearly 11% every

year, by 2022 the global market for FPCBs is expected to be worth $27 billion. This rise in demand is being driven by the benefits that FPCBs can offer to so many different electronic products.

BENEFIT: MINIATURISATION FPCBs allow electronic products with strict size constraints to maximise their functionality. Having fewer connectors allows similar functions to occupy less physical space and add less weight to each product. Furthermore, flexible circuits are

pliable enough to be configured around the edges and folds of devices; and they are durable enough to weather 200,000 bending cycles. This means these can be used in

miniature devices such as wearables, sleek fashion accessories, medical devices and smartphones. They can also be used in devices where reduced space and minimal weight are critical for performance – rockets, cars and satellites, for example.

BENEFIT: IMPROVED ASSEMBLY QUALITY The assembly process for FPCBs is, in many ways, simpler than that of their more rigid relations. This means that, in devices requiring three axes connections, for example, they can be assembled with minimal wiring, thereby reducing the risk of compromised signal integrity and noise interference. In addition, with fewer parts to solder, the risk of connection issues from cold joints is also minimised. These are therefore perfect for cameras,

John Johnston, NPI director at Chemigraphic, looks into the growing demand for flexible PCBs, discussing their advantages and the electronic devices they are ideal for

maintenance requests that fewer parts offer. They are therefore ideal for use in unattended devices, such as those used in space or by oceanographers, and in the oil industry.

HANDLING FRAGILE MATERIALS It used to be said that material handling during the manufacturing process of flexible circuits could account for an unacceptable percentage of production scrap and reliability issues. Flexible materials are certainly much

motion sensors, electronic compasses, micro electromechanical systems (MEMS) gyroscopes, and accelerometers.

BENEFIT: ENHANCED BOARD DURABILITY The lighter weight and reduced number of connectors also improves durability, while the elastic, lightweight circuit can easily absorb vibrations with minimal impact on any internal components. The polyesters and polyamides that

comprise FPCBs are also much more suited to withstanding harsher environmental conditions than rigid boards. Their resistance to extreme temperatures, vibration, corrosion and exposure to moisture makes them ideal for many challenging environments. In addition, where needed, portions

of a FPCB can be strengthened with a stiffening substrate to increase the reliability of these sections. They are therefore beneficial for

electronic applications designed for the military, aerospace, medical and automotive sectors. Their resistance to vibration also means they are suited to printers, keyboards and hard disks.

BENEFIT: REDUCE COMPONENT COSTS While it is true that rigid PCBs typically cost less than flexible circuits, there are some distinct cost savings with FPCBs, many of which may be hidden in traditional cost estimations. The reduced number of cables,

connectors, wire harnesses and overall parts required for FPCB assembly can make them more cost-effective in the long run. This is especially the case when you factor in the upstream and downstream benefits, such as the lowered supply chain risk and reduced

 DESIGN SOLUTIONS | JULY/AUGUST 2019 11

FPCBs are ideal for a wide range of applications including cameras, motion sensors, electronic compasses, micro electromechanical systems (MEMS) gyroscopes, and accelerometers

thinner and more fragile than those used in rigid boards. Flexible core materials are usually between 1-3mm thick, often containing just half an ounce of copper and with a flexible coverlay that is no more than 2mm thick. Yet, today, skilled operators using

specialist process equipment can transport these materials safely and with negligible damage. Similarly, the flexible portion of these

circuits once required laborious manual interventions from manufacturing engineers. The latest modern software puts all this to rest. Skilled engineers can quickly handle complex 3D designs to stack and test flexible parts in layers much earlier in the production process, where alterations and optimisations have much lighter cost and time implications.

Being resistant to vibration, FPCBs are suitable for printers, keyboards and hard disks

READY TO GET FLEXIBLE? It’s never a case of either/or. Hybrid rigid and flexible circuits are often used, and sometimes one part of a device may rely on FPCBs while another doesn’t. Speaking to Chemigraphic’s expert EMS team early in the design process can help you determine the benefits and decide whether it’s time to get flexible.


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