1. Why do PCBs need potting or conformal coating?

Potting and conformal coating are necessary technologies PCB fabrication, keeping the PCB away from adverse factors such as humidity, chemicals, and heat. It is well known that the PCB surface is covered with There are a large number of components including diodes, capacitors, fuses, and resistors, etc. Each electronic component plays a vital role in making the entire PCB usable, and damage to any one of them can cause the entire PCB board to fail. Especially in harsh environments, such as extremely high temperatures, excessive humidity or cold may cause decomposition problems, low insulation resistance, and conductor corrosion, in the end, the life of PCB components will be shortened. Therefore, we must do something to protect They and keep these components in the PCB for long term use. But how? Excellent, it's time to pour & conformal coatings to show their usefulness.

Potting and conformal coating do the same thing, they both apply organic polymers that provide chemical & thermal resistance and electrical insulation. But there are some differences between each other, for your better understanding, we will show more Detailed information is as follows.

2. Introduction to PCB Potting

2.1 Definition

Potting, also known as "encapsulation", is a method of encapsulating a PCB within a thick layer of resin that provides strong protection from physical shock and harmful chemicals, and at the same time, the process will improve electrical performance.

2.2 How does potting work?

First, we need to place the PCB assembly in an open pan and pour the liquid compound into it until the entire PCBA   is completely covered. The liquid contains some hardener to speed up the curing, and when the liquid sets and forms, it provides a good protection. Generally, the resin used is dark in color, which makes it difficult for us to see The board below it. Commonly used materials for potting compounds are epoxy, polyurethane, and silicone. Various materials have different advantages and disadvantages that should be considered, and choosing the right material depends on the application. For example, silicone and epoxy are very Suitable for high temperature environments; however, urethane has better protection against chemicals. So the key point we should pay attention to when choosing materials is to know what kind of protection we want to achieve.

3. Basic knowledge of conformal coating

3.1 Definition

As for conformal coating, it is another technique for protecting PCBA by applying a thin non-conductive layer to circuit boards and electronic components, the process can be performed manually and automatically. Characterized by thin and light (usually, The coating is only 25 to 250 microns thick), this technique does not add weight and thickness to the PCB assembly.

3.2 Five typical types

In terms of materials used, we have a variety of conformal coatings to choose from, the most popular types are acrylic conformal coatings, epoxy conformal coatings, polyurethane conformal coatings, silicone conformal coatings, and parylene Toluene, each has advantages and disadvantages. For example, acrylic resin is characterized by a fast curing time of 30 minutes, but can only withstand temperatures below 125°C. Epoxy coatings are very strong and durable, although difficult to repair. Parylene is the thinnest, Can withstand extremely high temperatures, suitable for any surface, but difficult to rework.

3.3 The main method of coating conformal paint

The three methods of applying a conformal coating include dipping, brushing, and spraying. Dip coating is the method in which one needs to dip the entire board into the coating, but it requires a great deal of proficiency to avoid leakage problems, now, due to the design Problem, there are not many PCBs in this way, but if the engineer considers the dipping method when designing, then, dipping can be a good method for high volume manufacturing. Brushing and spraying are suitable for small batch production, spraying is by spraying aerosol agent or spray gun. The next procedure is air curing, oven, or UV.