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The printed circuit board (PCB) has done more than almost any other innovation to enable our modern electronics industry. For decades, the PCB has offered the ideal solution for electronic designers. It is compact, space-efficient, and easy to manufacture. From the simplest household appliance to the most complex AI, the PCB is the backbone of the industry.
Connecting PCBs the old-fashioned way
The PCB has been with us in one form or another for over a century, but it was the birth of microprocessors that saw the birth of the PCB as a practical solution for everyday devices. In those early days, the components fixed to the PCB – microprocessors, passive components, memory devices – were still large compared to the modern state of the art, and so the PCB itself was large. In most applications, multiple PCBs were required to provide space for all of the components required, and so a whole section of the interconnection industry developed to provide solutions for joining PCBs together. All manner of board-to-board connector designs, from headers and sockets to card-edge backplane solutions, became hugely popular.
The electronics industry has continued to evolve and improve, however. Modern microprocessors and other components are now a tiny fraction of the size of their first-generation ancestors. This has allowed designers to produce far more compact devices, and the PCB has evolved in parallel to enable this. Modern devices of all kinds are taking advantage of this reduction in size and have witnessed electronics being employed in a huge range of applications that would have been impossible even a decade ago.
However, this has created a different problem when it comes to providing board-to-board connectivity. Even though connectors have become more compact, they are often now amongst the largest components that need to be fixed to the PCB. The traditional, rigid board-to-board connection strategies using fixed pin and socket designs are simply not flexible enough to solve some of today’s design challenges.
In years gone past, ribbon cables were a hugely popular alternative to fixed PCB-mounting connectors. They are flexible and easy to manufacture and allow the connection of PCBs even when space is at a premium. If you open almost any desk-top personal computer from the last 3 decades, the chances are high that there will be ribbon cables somewhere inside. Ribbon cables still have their place, but the modern industry demands solutions that are more compact and deliver higher performance. For this reason, ribbon cable technology has evolved.
The modern alternative to traditional ribbon cables is known around the industry as FFC. FFC stands for flat flexible cable and it is the latest evolution of the humble ribbon cable. Whereas ribbon cable is constructed using several stranded wires encased in an insulator, the FFC uses flat conductors that are bonded to a plastic film, creating a flexible solution that is far thinner than the stranded ribbon cables that went before.
The Advantages of FFCs
The flat construction provides a number of benefits over cable solutions.
- Size and Weight: The design of FFCs means that they take up far less space and are lighter in weight than stranded cables.
- Flexibility and Reliability: The thin construction of FFCs make them highly flexible, which means that they are ideal for dynamic applications that experience constant movements such as flip-phones or industrial robots. Their flexibility also means that they can be folded into complex shapes, providing innovative solutions for PCBs mounted into tight spaces.
- High Density: In contrast to the stranded wires within ribbon cables, the construction of FFCs allows the conductors to be placed with a narrower gap between conductors, otherwise known as the pitch. This means that the cables themselves are more compact, and the connectors that are mounted to the PCB can be considerably smaller than the familiar pin-header solution used by ribbon cables.
- Greater Performance: Ribbon cables are ideal for low-speed applications, but as the demand for high-speed communications grows, so does the need for protection against interference (EMI – electromagnetic interference and RFI – radio frequency interference). The flat design of FFCs makes it easier to provide EMI/RFI shielding, enabling them to be used in a wide range of high-speed applications.
Molex has developed the Premo-Flex family, delivering a suite flat flexible cables (FFCs) for board-to-board connections in modern applications. Premo-Flex offers a broad range of solutions, with pitches from 0.25mm to 2.54mm for the ultimate in high-density connectivity.
The Premo-Flex family includes a range of off-the-shelf cables for durable and extra flexible PCB connections. Terminating to the PCB can be achieved with Molex Easy-On One-Touch Connectors or can be performed with hot-bar soldering which removes the need for connectors entirely. This saves board space and provides highly secure termination for demanding applications.
Premo-Flex FFCs are the natural successor to ribbon cables, providing the same board-to-board connectivity whilst offering a host of additional advantages for the modern designer. Take a look at the Premo-Flex range on the RS website and see whether you are ready to embrace the latest technology.