How do conformal coatings work?

Conformal coating material is a thin polymeric film which ‘conforms’ to the contours of a printed circuit board to protect the board's components. Typically applied at 25-250 μm it is applied to electronic circuitry to act as protection against moisture, dust, chemicals, and temperature extremes that, if uncoated (non-protected), could result in damage or failure of the electronics to function. When electronics must withstand harsh environments and added protection is necessary, most circuit board assembly houses coat assemblies with a layer of transparent conformal coating rather than potting.

Some typical application examples include high-reliability defence, automotive and aerospace, where coatings are used to protect against various combinations of moisture, aggressive chemicals and vapours, salt sprays, large temperature variations, mechanical vibration, and even organic attack (e.g. fungus). The protective nature of conformal coatings also means that they not only protect, but also serve to enhance product reliability and thereby reduce the potential cost and damaging effects of early field failures.

As such their use is becoming increasingly common in consumer and domestic applications that can be susceptible to environmentally-induced field failure; including portable devices comprising fine pitch, densely populated assemblies, such as mobile phones, through to washing machines.

Conformal coatings protect electronic printed circuit boards from moisture and contaminants, preventing short circuits and corrosion of conductors and solder joints. They also minimize dendritic growth and the electro migration of metal between conductors.  In addition, the use of conformal coatings protects circuits and components from abrasion and solvents. Stress relief is also provided, as well as protection of the insulation resistance of the circuit board.

Conformal coatings are designed to protect printed circuit boards and related equipment from their environment.

Typically applied at 25-75μm, these coatings ‘conform’ to the contours of the board allowing for excellent

Protection and coverage, ultimately extending the working life of the PCB.

The use of conformal coatings is particularly important in automotive, military, aerospace, marine, lighting, industrial and green energy applications. Due to the rapid expansion of the electronics industry, conformal coatings are also finding their way into the domestic and mobile electronics industries, providing the necessary combination of high performance and reliability within a vast array of electronic devices.

The particular advantages of conformal coatings can be summarised as follows:

• Insulating properties allow a reduction in PCB conductor spacing of over 80%
• Can help eliminate the need for complex, sophisticated enclosures
• Light weight
• Completely protect the assembly against chemical and corrosive attack
• Eliminate potential performance degradation due to environmental hazards
• Minimise environmental stress on a PCB assembly

Ideally, conformal coatings should exhibit the following characteristics:

• Simple application
• Easy removal, repair and replacement
• High flexibility
• Protection against thermal and mechanical shock
• Protection against environmental hazards including: moisture, chemicals and other corrosive elements