Performance Evaluation of Fluoro Surf in PCB Moisture Protection and Insulation
The Fluoro Surf® FG-3000 series, designed specifically for applications requiring moisture resistance, waterproofing, and acid resistance in printed circuit boards (PCBs), exhibits excellent moisture-proof and insulating properties. It demonstrates high performance as an insulating and moisture-resistant coating for circuit boards and electronic components, as well as an acid-resistant and corrosion-resistant protective coating.
Conventional water-repellent and oil-repellent treatments typically suffer from poor mechanical strength of the film, making them prone to cracking under thermal shock. As a result, commercially available products generally limit film thickness to a maximum of 1 μm (at 2% resin concentration).
Table 1 presents a comparison of the time until insulation failure for various coating films when 200-μm-wide insulated electrodes protected by each coating were exposed to 5 wt% saline solution. The polyurethane-based moisture-proof coatings used for comparison—widely adopted by major automotive manufacturers for many years—demonstrate insulation-failure resistance of only a few seconds. In contrast, fluorinated materials exhibit overwhelmingly superior performance, maintaining insulation for durations ranging from several minutes to up to three hours depending on film thickness.
Table 1. Insulation Breakdown Resistance
| Type of Coating Film | Main Component Concentration | Coating Method | Film Thickness（μ） | Insulation Breakdown Time | Maximum Current Value(μA) |
| FG-3650TH- 8 | 8% | Immerse | 5-8 | 3 min 50 sec | 620 |
| Polyurethane-based | 15% | Spray coating twice | 5-8 | Immediately | 1000 ↑ |
| FG-3650C- 30 | 30% | Immerse twice | 15-20 | 146 min | 1.0 |
| Polyurethane-based | 15% | Spray coating 5 times | 15-20 | 3 sec | 1000 ↑ |
| FG-3650C- 40 | 40% | Immerse | 20-30 | 182 min | 2.2 |
Based on the above results, Fluorotechnology has summarized the relationship among practical application requirements, recommended film thickness, and recommended resin concentration in Table 2.
Table 2. Application Requirements and Recommended Film Thickness and Concentration
|
Grade |
Application requirement |
Recommended film thickness(μ） |
Recommended concentration |
|
Ⅰ |
To protect electronic circuits and components from moisture in the air under normal conditions |
2-4 |
4-8% |
|
Ⅱ |
To protect electronic circuits and components under hot and humid conditions in coastal areas |
4-8 |
8-10% |
|
Ⅲ |
Occasional exposure to water, or protection of electronic circuits and components from battery electrolyte and acidic gases |
6-10 |
20% |
|
Ⅳ |
Protects electronic circuits and components, enabling devices to function for up to 10 minutes underwater. |
20-40 |
30% |
|
Ⅴ |
Protects electronic circuits and components, enabling devices to function for up to 60 minutes underwater. |
30-50 |
40－50% |
|
Ⅵ |
Provides semi-permanent protection for electronic circuits and components under full water immersion. |
50 ↑＊ |
40－50% |
*Requires use with a waterproof enclosure.
In addition to the electrical characteristics mentioned above, fluoropolymers have a low dielectric constant of around 2.5, making them less susceptible to noise and suitable for high-frequency circuit boards. They also offer higher insulation performance compared to other resins.
