Advanced Circuit Board Design: Flexible Circuits

As the market for consumer electronics moves into ever-smaller devices like “wearables,” the demand for flexible circuit boards can be expected to increase. The old industry standard of dimensionally stable printed circuit board design may well become the exception more than the rule in just a few short years. One key factor driving demand for flexible circuit boards (and the wearable devices that they can be used in) is the rapid innovation in means of interacting with electronics. The main limiting factor in electronics miniaturization is the human limitations of interaction. If our eyes require a screen and our hands require a keyboard to receive information from and send information to our devices, then they can only attain a limited degree of miniaturization.

As AI interface systems make screens and keyboards increasingly unnecessary, device hardware manufacturers are increasingly willing to push tech into aspects of our lives where it has never gone before, such as onto our wrists, incorporated in our clothing, or on paper. In other words, flexible surfaces are likely to be a very big part of the future of electronics devices. To make that happen, PCB manufacturers are going to have to develop the flexible technologies necessary to drive these flexible devices. The challenges of a flexible PCB go beyond merely fabricating a flexible board, although that in itself is a considerable challenge. If the board is not dimensionally stable, it becomes a lot more challenging to protect the components from physical shock and to maintain the continuity of the circuit.

Flexible Electronics

There are a number of new technologies that enable the creation of “flex circuits”, or flexible electronics. These techniques involve fixing electronic components to flexible, usually plastic, substrates. One common material used for this purpose is polyimide, which is a polymer-based material. While polyimide boards are bendable and twistable, when reinforced with graphite or glass-fiber, a polyimide board can also exhibit very low expansion and contraction with great tensile strength. Polyimide boards are also durable in temperature extremes and are not reactive to most solvents and oils. Another material commonly used for flex circuits is PEEK – polyether ether ketone, a translucent thermoplastic polymer. PEEK boards, while flexible, are structurally stable, chemically resistant, and thermally durable. PEEK can be made into circuit boards using either extrusion or injection molding techniques. Polyester is another material that is increasingly being used for the fabrication of flexible circuit board design. Using a silk screen printing process, fabricators can print silver circuits on the surface of the polyester.

Flexible Electronic Components

The demand for flexible devices is driving all sorts of exciting innovation. One technique of great promise is in the area of “flexible and printed electronics” – FPE. Using a grapheme oxide “ink,” circuits and components can be printed onto polyester, polyimide, and other flexible surfaces to make ultra-miniaturized, flexible, and sturdy circuit boards. Graphene is a hex-shaped latticework microstructure that is one atom thick. The grapheme material has great electrical connectivity, and new technologies also allow printing using very simple, modified ink jet printers, making fabrication cheaper and more accessible than ever.