1. Brushing method.
This method is the easiest coating method. It is usually used for local repair and maintenance, and can also be used in laboratory environments or small batch trial production/production, generally in situations where coating quality requirements are not very high.
Advantages: almost no investment in equipment and fixtures; saving coating materials; generally no masking process.
Disadvantages: narrow scope of application. The efficiency is the lowest; there is a masking effect when painting the entire board, and the coating consistency is poor. Due to manual operation, defects such as bubbles, ripples, and uneven thickness are prone to occur; it requires a lot of manpower.
2. Dip coating method.
The dip coating method has been widely used since the early days of the coating process and is suitable for situations where complete coating is required; in terms of coating effect, the dip coating method is one of the most effective methods.
Advantages: Manual or automatic coating can be adopted. Manual operation is simple and easy, with low investment; the material transfer rate is high, and the entire product can be completely coated without masking effect; automated dipping equipment can meet the needs of mass production.
Disadvantages: If the coating material container is open, as the number of coatings increases, there will be impurity problems. The material needs to be replaced regularly and the container needs to be cleaned. The same solvent needs to be constantly replenished; the coating thickness is too large and the circuit board must be pulled out. In the end, a lot of materials will be wasted due to dripping; the corresponding parts need to be covered; covering/removing the covering requires a lot of manpower and material resources; the coating quality is difficult to control. Poor consistency; too much manual operation may cause unnecessary physical damage to the product;
Main points of dip coating method: The loss of solvent should be monitored at any time with a density meter to ensure a reasonable ratio; the speed of immersion and extraction should be controlled. To obtain satisfactory coating thickness and reduce defects such as air bubbles; should be operated in a clean and temperature/humidity controlled environment. So as not to affect the dot strength of the material; should choose non-residual and anti-static masking tape, if you choose ordinary tape, you must use a deionization fan.
3. spraying method.
Spraying is the most commonly used coating method in the industry. It has many options, such as handheld spray guns and automatic coating equipment. The use of spray cans can be easily applied to maintenance and small-scale production. The spray gun is suitable for large-scale production, but these two spraying methods require high accuracy of operation and may produce shadows (lower parts of components) areas not covered with conformal coating).
Advantages: small investment in manual spraying, easy operation; good coating consistency of automatic equipment; highest production efficiency, easy to realize online automatic production, suitable for large and medium batch production. Consistency and material costs are generally better than dip coating, although a masking process is also required but is not as demanding as dip coating.
Disadvantages: Covering process is required; material waste is large; a large amount of manpower is required; coating consistency is poor, there may be a shielding effect, and it is difficult for narrow-pitch components.
4. Equipment selective coating.
This process is the focus of today’s industry. It has developed rapidly in recent years, and a variety of related technologies have emerged. The selective coating process uses automatic equipment and program control to selectively coat relevant areas and is suitable for medium and large batch production; it Use an airless nozzle for application. The coating is accurate and does not waste material. It is suitable for large-scale coating, but it has higher requirements for coating equipment. Most suitable for large-volume lamination. Use a programmed XY table to reduce occlusion. When the PCB board is painted, there are many connectors that do not need to be painted. Sticking the adhesive paper is too slow and there is too much residual glue when tearing it off. Consider making a combined cover according to the shape, size, and position of the connector, and use the mounting holes for positioning. Cover the areas not to be painted.
Advantages: It can completely remove the masking/removing masking process and the resulting waste of a lot of manpower/material resources; it can coat various types of materials, and the material utilization rate is high, usually reaching more than 95%, which can save 50% compared with the spraying method % of the material can effectively ensure that some exposed parts will not be coated; excellent coating consistency; online production can be realized with high production efficiency; there are a variety of nozzles to choose from, which can achieve clearer edge shape.
Disadvantages: Due to cost reasons, it is not suitable for short-term/small batch applications; there is still a shadowing effect, and the coating effect on some complex components is poor, requiring manual re-spraying; the efficiency is not as good as automated dipping and automated spraying processes.
Post time: Sep-06-2023