Everything About PCB Conformal Coating
What Is Conformal Coating?
Conformal coating is a specially designed polymer thin film chemical coating that protects PCB plates and electronic elements from harmful environmental conditions such as moisture, pollutants, static electricity, vibration, and pollution. Manufacturers print coatings into irregular areas of PCBA plates that provide higher dielectric resistance and reliability.
The manufactured and assembled PCB is highly susceptible to contamination, thus will reduce the shelf life of the PCB with time. The conformal coating working as a protective layer made of a mixture of different ingredients protects the PCB from erosion, moisture, contamination, oxides, and other particles that will reduce PCB quality, significantly reduce performance, and even make PCB useless.
Why Does PCB Assembly Need Conformal Coating?
As mentioned above, many factors can adversely affect PCB performance without using a conformal coating. A conformal coating is a prophylactic coating that acts as a protection measure to protect the PCB from external contaminants that may occur even during PCB manufacturing, such as flux and other etching chemicals and reagents. It prevents mechanical vibration, thermal shock, and high temperature of PCB due to ambient conditions or excessive PCB operating temperature. It improves reliability and ensures the normal functioning of the PCB.
As we know that humidity is well known to be detrimental to metal components, we observed higher air humidity in areas/sites close to the sea compared to other parts of the city. Therefore, this humidity level is oxidative in metal components and electronic components. The PCB is made entirely of metal components, such as significant metals such as copper, silver, and aluminum used so that these metals react with moisture in the air to accelerate the PCB to decompose and corrode the conductor. Copper turns green with these elevated water vapor and oxygen levels, respectively. However, the conformal-coated PCB is more resistant to this high humidity and water vapor, which may be present in the environment where we use PCB. The conformal coating will prevent the oxidation and degradation of the conductor on the PCB, thereby increasing the lifetime of the PCB.
Another most important reason for requiring a conformal coating is pollution. These contaminants may be solid dust particles that get stuck in the tiny space of the PCB SMT assembly and can cause a short circuit. Other treated contaminants may be human oils, fingerprints, and food pellets. The surrounding environment that preserves or uses the PCB also produces contaminants, such as spray, grease, oil, fuel spill, and acid fog exposure. Field technicians must be trained to handle electronic PCBs with gloves properly and not spit and splash liquid while tolerating PCBs.
With printed circuit boards without conformal coating, the related electronic equipment or equipment will be prone to damage. And irreversible electronic failure in these harsh environmental conditions. Defects mainly cause pollutants in the PCB manufacturing setup, such as improper cleaning and not cleaning chemical residues during chemical plating or etching. Professionals highly recommend cleaning the PCB thoroughly before applying a conformal coating.
How many methods does Venture have for PCBA conformal coating?
There are mainly two methods to apply the conformal coating in the PCB manufacturing house.
Manual brush coating
Manual brushing can be a cost-effective solution, but it can be time-consuming. Professionals recommend using skilled technicians to smooth and evenly brush the conformal coating on PCB surfaces.
Manual aerosol coating
You shall use unique spraying rooms with a minimum number of external pollutants. Specialized technicians who master the aerosol can manually spray to produce PCB on a small scale cost-effectively. Do not shake the aerosol before spraying, as it can cause bubbles to form and transfer to the plate. Keep PCB from surface 45°, the aerosol from PCB shall be 20-30cm, spray conformal coating from top to bottom. Then rotate plate 90° and repeat until boar rotation 360°. This completed process ensures the uniformity of the conformal coating and that you coated every area on the PCB evenly.
Manual Atomized Spray Coating:
The Manual Atomized Spray Coating process is the same as the aerosol spray process but faster and more effective. Professionals must ensure proper ventilation, viscosity, air, and material proportions.
Conformal Coating Operation Process Requirements:
- Clean and bake board to remove moisture and water. You must remove the dust, moisture, and oil on the surface to ensure complete protection. A thorough cleaning ensures you remove the corrosive residue and adhere the three-proof paint well to the circuit board surface. Baking board conditions: 60°c, 10-20 minutes after removal in the oven, while hot coating effect is better;
- With the brushing method, the brushing area should be larger than the device to ensure that all the gadgets and pads are covered.
- Put the plate as flat as possible. It would be best if you don’t expose it after brushing. The brushing should be plane, and there should be no bare parts.
- Stir the diluted products thoroughly before brushing and spraying, and place them for 2 hours before brushing or spraying. Use a high-quality natural fiber brush and gently brush at room temperature. If you use machines, you should measure the viscosity of the coating (with a viscosity agent or a flow cup). And you may adjust with a diluent.