Flex Circuit Boards
In addition to being used in the electronic industry in calculators, cell phones and LCD televisions, flex circuit boards can also be found in medical devices such as heart monitors and pacemakers. They are also used in industrial products such as robotic arms, processing machines and bar code equipment. In fact, the list of possible applications is endless. This type of flexible printed circuit board has advantages over rigid and single-sided PCBs, such as the ability to bend around corners or folds. They are lightweight and take up less space than their rigid counterparts.
The main components of a flex circuit board are the conductors, insulators and support materials. Conductors are the elements that allow current to flow. They are typically copper but can be a variety of metals. Insulators separate the conductors from each other and prevent them from conducting electricity themselves. Insulators are commonly made of polyimide, polyester and/or solder masks and can be plated with either epoxy or acrylic. The support material is generally some form of a fiberglass core or an FR-4 composite board. Some flex circuits are built with an adhesive such as epoxy or acrylic while others use a construction method called Adhesive Less (ALP) which eliminates the need for an adhesive.
One of the most important considerations when designing a flex circuit is identifying the minimum amount of stress that the flexible region can withstand. This should be done during the design phase so that the correct material stack-up can be incorporated into the flex circuit. The number of layers should be limited and the conductive copper should sit closer to the neutral bend axis. This will avoid stress points in the conductors caused by stacked copper that can break the copper.
Can Flex Circuit Boards Bend?
Other common considerations for a flex circuit include determining the maximum bending angle and radius, as well as identifying the optimum placement of the conductors in the bend area. It is best to place the conductors in a manner that does not exceed the maximum bending angle and radius. It is also recommended that the conductors be placed in a staggered fashion to minimize stress points and prevent the copper from buckling under load. This is particularly important in high-speed applications where the circuit is subject to repetitive flexing.
Another crucial consideration is to be aware of the different types of flex circuits available, and which ones are best suited for a given application. For example, a single-sided flex circuit is ideal for low-speed applications and does not need to be extremely rugged, while a multi-layer rigid-flex circuit is required for high-speed or harsh environments.
It is also a good idea to have an expert review the flex circuit before it goes into production to ensure that the design will meet manufacturability standards and performance requirements. This will save time and money in the long run by preventing costly errors in the manufacturing process. By following these tips, a designer can design a flex circuit that will meet their specific project needs while minimizing assembly costs.