Conformal Coating and Why Is It Used During Rigid Flex PCB Fabrication

Rigid-flex pcbs are used in an array of everyday electronic devices, from handheld electronics such as laptops and MP3 players to sophisticated medical/avionics equipment. These boards offer many benefits, including reduced manufacturing costs, extreme reliability, and the ability to occupy less space than rigid PCBs. They are also extremely durable, able to withstand multiple bends and even a twist or two.

PCB fabrication processes involve the use of a variety of materials and chemicals, which can cause damage or contamination. Conformal coating prevents contaminants from coming into contact with sensitive circuitry, thereby improving reliability and prolonging the life of the product. This is particularly important when the device is exposed to moisture or chemical contamination, which can cause corrosion and other degradation.

The conformal coating process itself can be a complex one, but it is essential for ensuring the integrity of the finished product. The process involves applying a thin film to the surface of the printed circuit board. This film is then hardened using heat or UV radiation, allowing the printed circuit board to be manipulated without fear of damaging it.

What Is Conformal Coating and Why Is It Used During Rigid Flex PCB Fabrication?

Conformal coating can be applied to any part of a rigid-flex pcb, but it is most commonly used on flex circuits and RF assemblies. This is because flex circuits and RF assemblies are more susceptible to mechanical stress, and the conformal coating can protect the components from premature failure due to mechanical shock or vibration.

Several different types of conformal coating are available, but each must be carefully chosen to ensure that it provides the protection needed for the specific application. This involves balancing the protective properties of each type against the practicalities of application and production. For example, a thicker conformal coating offers more protection but may be harder to work with.

The location of the conformal coating on a flex PCB is also important, as it must be able to accommodate the maximum amount of bending. A flex PCB typically has a hatched polygon ground plane in the area of the bend, which must be routed perpendicular to the bending line to maintain structural integrity and reduce the likelihood of premature failure. To further reduce the risk of failure, a dummy trace can be added to the flex PCB.

It is important to specify the conformal coating as an integral part of the electrical design of a flex circuit board, especially when working with a fabricator. This helps ensure that the design and fab portions of the project are well coordinated, and it can also improve overall quality. Tools such as Altium Designer make it easy to include the specification of a flex PCB conformal coating as an integral part of the design. This can then be easily shared with a fab shop via the Altium 365 Platform or other data export routes. This will help the fab team avoid the need for extra or specialized design steps, which can ultimately save time and money in the manufacturing process.