Webinar on PCB conformal coating errors: answering your questions

In webinar held by Enrico Quagliato and dedicated to how to avoid errors in application of conformal coating we addressed the main defects that can compromise protection of electronic boards, analyzing their causes e operational solutions.

During the webinar on PCB conformal coatings, several questions emerged regarding real-world application cases. In this article, we have compiled the answers provided by Enrico Quagliato, in order to provide answers to questions and needs raised directly by those working in electronic protection.

What is the minimum thickness of the conformal coating to ensure the necessary protection quality on the board?

Generally, a thickness of less than 25 µm is not applied. This is a fairly well-established technical reference, also because IPC standards specify minimum values of this type: approximately 25 µm for acrylic or polyurethane coatings and 50 µm for silicone ones.

However, this does not mean that below 25 µm the board is not protected. The point is that there is no single thickness valid for all applications.

The choice of the correct thickness must always be verified with application tests, as it depends on several factors; including thermal cycles and exposure to aggressive environments such as salt spray and the actual operating conditions of the PCB.

In some cases, much higher thicknesses are reached, such as 75 µm, 100 µm or 150 µm. Each application therefore has its own specific requirement, linked both to the context and to the chemical nature of the conformal coating used.

Is the baking process, before using the coating, useful to facilitate its application?

Before answering the question, it is necessary to specify that baking is an industrial drying process to remove moisture absorbed by the PCB.

In general, the baking process can be useful, especially for removing moisture or air that may remain trapped in the PCB or under some components.

This helps to avoid issues during the PCB conformal coating application. At the same time, however, care must be taken, because the heat remaining in the board can influence the subsequent process. In particular, it can cause:

• a faster polymerization of the product;
• faster drying;
• increased evaporation of the solvent.

All these factors, if not controlled, can lead to defects.

Again, no fixed rule exists: it is necessary to test and find the right balance between moisture removal and control of the drying process.

Are there systems to improve the surface tension of the PCB without using plasma?

Yes, primers exist. They are liquid products that are applied before the conformal coating and serve to improve the adhesion of the coating.

The use of primers, however, introduces some complexities. On one hand, there are aspects related to compatibility with electronic components, and on the other, toxicological considerations.

For this reason, before using a primer, it is always necessary to test them to verify that they do not interfere with the operation of the components.

Primers exist for all major chemistries, including acrylic, silicone, and polyurethane conformal coatings. In some cases, they are already used successfully, but integration into the production process can be more complex, especially when working on a large scale.

By using UV-cured conformal coatings, do I limit defects from an incorrect oven drying process, or can similar defects occur?

UV-cured conformal coatings have a significant advantage because they do not contain solvent. This means that all issues related to solvent entrapment, such as bubble formation, are eliminated.

That said, it does not mean they are free of defects. If the application process is incorrect, problems can still occur. For example, suboptimal spraying can generate air bubbles which, when the conformal coating is UV-cured, remain trapped in the film.

Similarly, if the application environment is not controlled, dust or contaminants can settle on the PCB conformal coating and be embedded during curing.

In conclusion, it can be stated that UV-cured conformal coating eliminates solvent-related problems, but still requires attention in the application process.

What are the risks of applying multiple coats of conformal coating?

Applying multiple coats of conformal coating on PCBs is possible, but from a technical standpoint, it is generally discouraged.

When applying two coats, in most cases there is adhesion between the second and first layer, but a joint line still remains between the two. Furthermore, if errors are present in the first coat, a second application risks duplicating them.

For this reason, the suggestion is to work on the process and the material to reach the desired thickness with a single coat, avoiding unnecessarily complicating the application.

Does applying a coat of conformal coating and then encapsulating with resin increase or decrease protection?

Applying a first coat of conformal coating and then encapsulating can increase protection, but it is a method that must always be evaluated on a case-by-case basis.

A typical situation is when the potting is very rigid and can stress the components. In these cases, you can first apply a softer and more elastic conformal coating, which helps to reduce this stress.

Another case is related to viscosity of the potting: if it cannot penetrate all areas of the PCB, conformal coating, being more fluid, it can ensure more uniform coverage before encapsulation.

It is a less common solution, but in some applications, it can represent a concrete advantage.

For critical applications, such as in aerospace, are there particular precautions beyond using low-outgassing products and board washing?

In the aerospace sector the level of attention is much higher. Work is carried out with extremely controlled processes and with qualified materials, for example with low outgassing requirements.

That said, the basic precautions remain the same:

• PCB cleaning;
• application process control;
• correct coating selection.

Washing electronic boards is often required precisely to ensure a high level of cleanliness, but there are no completely different logics compared to other sectors. The level of control changes, not the principle.

Are there conformal coatings or potting compounds that can increase the insulation voltage on electronic boards?

Yes, specific solutions exist, especially for one of the most critical areas, namely component edges.

These areas tend to have a lower coating thickness than nominal, and therefore are more exposed.

There are formulations specifically designed to improve coverage of these critical points, known as sharp edge coverage systems.

These products allow for more uniform protection even in complex geometries, without having to excessively increase the overall coating thickness.

What is the ideal drying time for a PCB conformal coating before handling, considering a thickness of around 50-60 µm?

There is no single answer, because it depends on the type of PCB conformal coating used.

There are many variables involved:

• chemical nature of the product (acrylic, polyurethane, silicone);
• presence or absence of solvent;
• curing method, which can be air, oven, or UV.

For this reason, it is necessary to analyze case by case, evaluating both the material characteristics and the production needs in terms of curing speed.

Learn more about PCB conformal coatings

If you want to delve deeper into the topics covered in the webinar, you can access structured technical content designed to support the analysis and optimization of PCB conformal coating application processes.

In the dedicated guide “How to avoid errors in conformal coating application“, we have compiled the main operational criticalities and solutions to prevent them, with a practical approach based on direct field experience.

In view of our participation in Focus on PCB 2026, we have also developed new technical guides on silicones for electronic protection and Low Pressure Molding technology for PCBs, with the aim of exploring increasingly relevant materials and processes in the sector.

If, on the other hand, you are experiencing application defects, adhesion problems, or want to improve the reliability of your process, you can contact our industry experts directly.