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Conformal Coating used in PCBA manufacturing by Hitech Circuits Co., Limited
Conformal Coating used in PCBA manufacturing by Hitech Circuits Co., Limited
Circuit board waterproof oil, also known as three proof paint or PCBA circuit board protective oil, is a special coating used for protecting assembled circuit boards. It can be a single component room temperature curing coating, made of materials such as silicone or acrylic resin.
This product can be applied through brushing, spraying, or dipping processes, and after curing, it forms a transparent protective film with properties such as moisture resistance, salt spray resistance, mold resistance, insulation, shock resistance, dust resistance, corrosion resistance, aging resistance, and corona resistance. The temperature range for its use is usually -50 ℃ to 120 ℃, and the coating thickness needs to be controlled between 25 microns and 130 microns.
Typical applications for electronic components and circuit board protection in fields such as automotive electronics, medical equipment, military, and outdoor LED displays. During construction, it is necessary to maintain ventilation and take personal protective measures.
Circuit board waterproof oil is a single component, low viscosity transparent acrylic resin. Three proof paint can be divided into six categories based on its chemical composition: acrylic ester, silicone, polyurethane, epoxy resin, nano, and water-based. This product belongs to the acrylic ester category. A typical product has a relative density of 0.75-0.82 g/cm ³ and a viscosity of approximately 22 CPS at 25 ℃.
The typical mechanical properties of the protective film formed after curing include tensile strength of 4.5 MPa, elongation at break of 350%, hardness (Shore D) of 60, shear strength of 3.5 MPa, and peel strength ≥ 6 N/mm. Its electrical performance is characterized by a volume resistivity of 5.0 × 10 ¹⁴Ω· cm, a dielectric strength of 21 kV/mm, and a dielectric constant of 3.0 (1.2MHz). Its operating temperature range is -50 ℃ to 120 ℃. [1] According to industry standards, the typical thickness range for such protective coatings is 25 µ m to 125 µ m.
According to international standards such as IPC-CC-830B "Qualification and Performance of Electrical Insulation Compounds for Printed Board Assemblies" and historical standard MIL-I-46058C, the coating process of waterproof oil on circuit boards must comply with relevant requirements.
Construction methods such as brushing, spraying, immersion coating, and selective coating can be used. The coating is limited to no flow or leakage. The coating thickness should be controlled between 25-125 μ m, with a recommended thickness of 50-75 μ m. Specific requirements should comply with standards such as IPC-CC-830B or MIL-I-46058C.
Before painting, the moisture and oil stains on the surface of the object to be painted must be removed first. Pretreatment requires thorough cleaning of the PCBA, removal of flux residue and grease, and pre drying (60-80 ° C) to remove moisture.
After the first coating is dry, the second coat can be applied.
Coating should ensure 100% coverage of conductors, solder joints, and easily corroded components. Exempted areas such as connector pins, test points, heat sinks, gold fingers, optical devices, etc. should be protected with masking tape or fixtures.
Used brushes, spray guns, etc. should be cleaned promptly for future use. Pay attention to ventilation during construction, and the environment should have a temperature of 15-30 ° C and a humidity of ≤ 70% RH to facilitate the evaporation of solvents in the coating and ensure safety.
Single component packaging, solidified by contact with moisture in the air during use. If it is not used up at once, it should be promptly covered for future use.
After coating is completed, performance verification is required, such as insulation resistance testing (required to be ≥ 1 × 10 ⁹ Ω, according to IPC-TM-650 2.6.3.7) and withstand voltage testing.
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