How Conformal Coating Enhances Rf Shielding PCB

Conformal Coating Enhances Rf Shielding PCB

Conformal coating enhances rf shielding pcb by providing a physical barrier against electromagnetic interference (EMI). It can prevent metal migration between closely spaced conducting lines, which could cause short circuits and catastrophic board failure. This is a critical function of conformal coating because moisture, impurities, and bias are major causes of metal migration on PCBs [1]. The EMI suppression offered by conformal coating also helps prevent damage to sensitive components from transient surge currents.

The material used to create conformal coating must meet a range of quality requirements, including thermal properties and resistance to humidity. The choice of material depends on the operating temperature of the circuit board and its environment, the sensitivity and durability of the electronics, and the amount of EMI protection needed.

Conformal coating can be applied manually or with a spray system. Using manual spraying requires the use of masking to protect areas not to be coated, which is a time-consuming process that must be repeated for every area of the board that is to be coated. An automated spray system uses a programmable robotic spray nozzle that is designed to specifically apply the coating to selected areas on the circuit board, removing the need for masking and saving time. It also provides a high level of repeatability and consistency.

Before and after coating, thickness measurements must be made to ensure that the coating is uniform in its application. This can be done with a non-destructive method by placing a probe against the surface of the circuit board and measuring the distance between it and the metal underneath. The measurement results provide an instantaneous indication of the coating thickness, with the standard deviation indicating the coating’s consistency and uniformity.

How Conformal Coating Enhances Rf Shielding PCB

Solvent removal is a common technique for coating removal, but care must be taken to ensure the solvent being used will not damage parts or components on the circuit board. Acrylics are the easiest to remove with solvent, while epoxies and urethanes are more difficult. Parylene cannot be removed with solvents. Peeling is another common removal method, mainly for flexible conformal coatings such as silicone or polyurethane.

Some conformal coatings can be sanded to remove them, but this is usually done only on rigid boards such as those used in computer cases. Other methods include micro blasting, which involves spraying a mixture of soft abrasive and compressed air to abrade the coating. This is used to remove parylene and epoxy conformal coatings, but it is not recommended for other types of conformal coatings due to the risk of serious damage to the circuit board.

A final alternative to conformal coating is the use of a via fence, which can block a single or range of frequencies. This can be expensive compared to the cost of using an absorbing conformal coating, but it is an effective option for circuit boards with a wide variety of frequencies that require blocking. Conformal coatings can also be stripped by heat, but this is not recommended as it may damage the circuit board and lead to failure.