Moisture-Resistant, Insulating, and Electrolyte-Resistant Coatings for PCBs

Specifically designed for moisture-proof, waterproof, and acid-resistant applications on printed circuit boards (PCBs), the Fluoro Surf® FG-3000 Series exhibits excellent moisture resistance and electrical insulation performance. It demonstrates high performance as an insulating and moisture-protective coating for circuit boards and electronic components, as well as an acid- and corrosion-resistant coating.

Conventional water- and oil-repellent surface treatments generally suffer from poor mechanical film strength and are prone to cracking due to thermal shock. As a result, products currently available on the market are limited to film thicknesses of approximately 1 μm or less (corresponding to a 2% resin concentration).

Table 1 shows water vapor transmission rate (WVTR) data classified by coating type and film thickness. As indicated in the table, moisture barrier performance is proportional to film thickness. Therefore, when the film thickness is limited to only a few micrometers or less, even fluoropolymer films with inherently high moisture resistance cannot exhibit sufficient protective performance.

The Fluoro Surf® FG-3000 Series can easily form coatings over a wide range of thicknesses, from several micrometers to several tens of micrometers or even thicker. Even at high film thicknesses, the coating can withstand thermal cycling stresses without cracking, thereby delivering outstanding moisture-proof and waterproof performance.

Lithium batteries are widely used in mobile devices due to their compact size and high power output. However, they are also well known for their high risk, as fire accidents occur frequently. When a mobile device is dropped and damaged, leakage of battery electrolyte may occur, potentially damaging the charge–discharge control circuitry. This damage can lead to thermal runaway and ultimately result in fire.

In the event of electrolyte leakage, fluorinated coatings offer superior resistance to battery electrolytes as well as excellent electrical properties, effectively protecting the control circuits. In contrast, other resins such as polyurethane and acrylic coatings are unable to provide sufficient protection under these conditions. This electrolyte resistance is closely related to the coating’s dielectric strength and insulation breakdown resistance.

This application has been adopted not only in mobile devices such as tablet computers and smartphones, but also in a wide range of lithium battery control circuit boards used in commercial aircraft, electrically assisted bicycles, and electric vehicles.