Flexible Printed Circuit Boards

Electronic devices require a sturdy design, and conformal coating is an essential component of many modern applications. Its use is widespread, from consumer electronics to aerospace and defense equipment. It enhances flex circuit boards to protect them from environmental exposure, while also improving their durability. The question is, what are the best ways to apply this protective coating?

The choice of application method depends on several factors, including production requirements, sensitivity of the PCB, and how durable it needs to be. For instance, a flexible printed circuit board that will be used in extreme environments may need to be coated with a material that is resistant to moisture and other environmental contaminants.

These types of coatings can be sprayed, dipped, or brushed on, and are generally applied in layers. Whether one layer or multiple, it is important to ensure that the coating completely covers any sharp edges and contours of the board to prevent shorts between tracks. It is also vital to apply a thick enough coating to provide adequate protection, without exceeding maximum coating thickness limits.

How Conformal Coating Enhances Flexible Printed Circuit Boards

A quality conformal coating can significantly increase the lifespan of a flex circuit board, as well as improve the performance of its components. It can reduce electrical interference by providing an insulating barrier between circuits and preventing shorts caused by corrosion. It can also reduce mechanical stress from frequent use, rough handling, and thermal cycling. In addition, conformal coating can help to decrease arching of components and reduce fatigue in solder joints. It can also slow tin whisker growth, which is another common cause of shorts between components.

Considering all the benefits of conformal coating, there are a variety of different options for applying it to PCBs. Some methods require masking and pre-coating processing, which can be costly and time-consuming. Others rely on manual spraying or dipping to apply the coating, which can be impractical for high-volume production runs. In these cases, a selective automated spraying system can be utilized to control the application process and prevent areas not requiring the coating from being coated.

The type of conformal coating you choose should be compatible with the environment in which it will be deployed. Some coatings are designed to withstand extreme temperatures, while others can be formulated to withstand the high humidity and a wide range of airborne contaminants that are often found in manufacturing facilities. Additionally, some coatings are UL recognized and rated to the flammability standard UL-CC-830B.

While conformal coating can significantly improve the durability and functionality of a flexible printed circuit board, there are some concerns about its use. It is crucial to understand these concerns before deciding to implement this technology in your production line.

The most important thing to remember about conformal coating is that it is not intended to be a waterproof sealant, but rather a semi-permeable protective layer that allows any trapped moisture to escape. It is also important to keep in mind that conformal coating is not a substitute for proper PCB design and manufacturing, as well as rigorous testing and inspection.