Flexible Printed Circuits for Consumer
Whether they’re found inside mobile phones, tablet computers or medical devices, the circuitry in these products needs to be thin, flexible and durable enough to fit in the compact case that surrounds them. Traditional circuit boards can’t offer this, but flex printed circuits can. These are able to be made in complex shapes that would be impossible with flat ribbon cables, and their conductor density far exceeds what is possible with ribbon cable.
These circuits are also incredibly lightweight and small, making them the perfect choice for consumer electronics. As handheld devices, these are taken everywhere, exposed to the changing temperature and environment of the surrounding space. This makes them the ideal choice for a flexible printed circuit that must be able to bend and twist without becoming damaged.
The flexibility of these circuits also helps them to be used in more inventive ways than regular PCBs. For example, some researchers are developing a pill-sized device that contains a flexible circuit board, allowing doctors and patients to see inside the body for diagnoses and treatment. The technology will be able to flex and adapt as it moves around the patient’s body, enabling them to get a more accurate view than current methods.
Flexible Printed Circuits for Consumer Electronics
A flex circuit can also be used to connect rigid boards together, eliminating the need for the tall and bulky connectors that a ribbon cable requires. This is particularly useful in creating prototypes and allowing engineers to test out new ideas before committing them to production.
Using a flex circuit can make it easier to integrate other components, such as switches and sensors, into the product. This can help reduce the amount of solder needed, reducing manufacturing costs and lead time. It can also save on component storage space. These are advantages that can have a significant impact on the profitability of the finished product.
While a flexible printed circuit can be made from many different materials, copper foil remains the most common choice because of its combination of low cost, high electrical conductivity and durability. The copper surface is coated with a dielectric material that protects it from oxidation. For contact areas this is often gold, but in some cases it’s silver.
These flex circuits can be single or double-sided. A single-sided flex has just one layer of copper conducting material, but can be designed with a dielectric and protective solder mask on both sides. This type of flex is very popular, and has the additional benefit of being able to be drilled with copper-plated through holes.
Double-access flex circuits, or back-bared flex, are a more advanced form of this simple flex design. They allow for access to selected features of the conductor pattern from both sides. However, this comes with a price of greater processing complexity.
Regardless of the type of flex circuit used, it’s important to choose the right fabrication process and materials for the application. A flex circuit is subject to considerable tensile and compressive stresses as it bends. The metal (copper) suffers work-hardening at tight bending radii, and the film substrate and coverlay experience compression. The resulting fatigue fractures can damage the circuit. To avoid this, the IPC recommends that flex corners be terminated to a component or rigid area.