Conformal Coating

Every organization using hazardous chemicals within their facility has the responsibility to equip their facility and personnel to maintain exposure levels below the TLV. Personal monitoring badges can be used to measure exposure of a specific material. Then, depending on the threshold limit and the application, exposure can be controlled with PPE like masks, face shields, respirators, and even coveralls. If they don’t reduce exposure below the recommended limit, you will need to consider a special ventilation hood or even containment booth. As you can see, as the exposure limit gets down to a certain level, the equipment required to safely use the solvent can get impractical. At that point, your best option is to consider a safer alternative.

The dielectric strength is material intrinsic property and withstand voltage is surface property which depend on thickness of the material. They can be slightly different for thicker materials, but for conformal coating, the two numbers should be very close or the same. That is because we test coating at 3-5 mils thickness, calculate, then report the value per mil.

Conformal coating with UV tracer can be inspected with any typical UV lamp which has wavelength of 320-380 nm.

Techspray offers the TraceTech Conformal Coating Remover Pen that allows you to remove a tight area of coating around a repair area without affecting the rest of the PCB. You first saturate the tip by tapping it lightly on a surface, which opens the valve and releases solvent. Holding the tip down may oversaturate it, which could lead to solvent flowing into unintended areas.

No, conformal coatings are non-conductive, or insulative. The job of conformal coating is to isolate the PCB or components from the environment and even components (i.e. high voltage or high heat) from the rest of the board. To do that properly, a coating must have electrically insulating properties with as high of a dielectric withstand voltage (or strength) as possible.

While conformal coatings can offer a moisture resistant layer of protection, most cannot be considered waterproof. Even if applied heavily, most coatings are semi-permeable, so allow some amount of moisture through. Conformal coating can, however, prevent current leakage or corrosion due to ambient moisture. To truly waterproof electronics, you either need gasketing to seal the electronics within the packaging or cover the electronics with a waterproof encapsulant or potting compound.

Whether or not conformal coating is required depends on the environment the electronic device will operate in, the reliability requirement of the device, and the cost of failure, whether in dollars or human lives. Typical consumer devices are generally not coated because cost is one of the top driving factors, and a coating step certainly adds to that. Devices operating in harsh environments may require coating, and the type of stresses and contamination will point to the best option, whether that is acrylic resin (AR), silicone resin (SR), urethane resin (UR), or some other type of protection. Aviation, aerospace, and medical devices often require coating because of the mission critical nature of these applications.

Conformal coating is a specially engineered polymeric film-forming product that protects circuit boards, components, and other electronic devices from harmful environmental conditions like moisture, thermal shock, static, vibration, and contamination. These coatings ‘conform’ to the irregular landscape of the PCB providing increased dielectric resistance, operational integrity, and reliability. There are a number of options for coating technologies, and the best option should depend mainly on the protection required. Application method and ease of rework are also important factors, but should generally be considered secondary to the protective performance needed.