PCB Blog - 15 Ways to make your PCBs waterproof

When designing PCB boards, we inevitably face issues with humid environments, such as rainy days or steam in factories. In such situations, circuit boards are easily damaged. In the past, we had to pay high attention to the design of PCBs, using waterproof materials and special processing techniques to make them waterproof. However, the complex processes and high costs resulted in PCBs being priced higher than other products. Currently, there are various high-reliability technologies available that can make PCB boards waterproof. We can use them as alternatives to traditional methods.

How to protect your electronic products' PCB board:

It is always recommended to protect the PCB board and store it in a dry place. Placing the PCB board in a sealed bag is a good idea. This way, the PCB board will not be affected by water, even if it is raining heavily outside.

There are many methods to waterproof a PCB. You can choose one according to your needs.

1. Applying waterproof materials on the PCB board surface

This method is used for very specific purposes, such as manufacturing PCBs for control systems of ships or submarines. Through this method, you can add special materials to the surface of the PCB board to make it waterproof, such as Polybutylene Terephthalate C or Polybutylene Terephthalate N. In fact, Polybutylene Terephthalate C and Polybutylene Terephthalate N are the same material. They are high-density polymers that can be made into thin layers. Usually, when we apply them on the PCB board, they are in liquid form. After a period of time, they will cure and become waterproof materials. The thickness of Polybutylene Terephthalate C is about 2 mils (0.05mm), much thinner than traditional varnishes (such as epoxy resin). If you need to make your PCB board waterproof, you can choose Polybutylene Terephthalate C or Polybutylene Terephthalate N as your material.

2. Using waterproof materials to seal connectors

If you want to make waterproof PCBs, but not for special purposes, you can choose to use waterproof materials to seal connectors. Connectors are mainly used to connect wires and other components, such as wires, terminals, and sensors. Connectors come into direct contact with water when in use. If not sealed properly, water can seep into the PCB board. When this happens, your electronic device or PCB will be easily damaged.

3. Coating the PCB board with specialized waterproof paint

If you need to make waterproof PCBs but do not want to use special materials, you can use some paints. They are usually used as protective layers. You can easily apply them on the surface of the PCB board. The main purpose of these paints is to protect the surface of the PCB board and make it smooth. However, they can be applied to the PCB board with high quality and low cost. If you choose this method, it is recommended to choose the best waterproof coating for your PCB board.

There are many types of waterproof coatings on the market, but not all of them are reliable and effective enough. Which application process is better? Spray, manual spraying, or immersion?

Waterproof coatings for PCB circuit boards

1. Spray

This application process is the most common for PCB paints. In this process, the paint is stored in a hopper and then pumped into the gun. The paint will be sprayed onto the PCB board with the help of the gun.

2. Manual spraying

This process is similar to distribution, but when you do not have a specialized spray paint machine or have many different PCB boards to paint, you can use manual spraying, especially when these PCB boards cannot be painted through distribution. If possible, it is better to use manual spraying rather than distribution method, as manual spraying allows you to paint with high precision and make the surface of the PCB board smooth.

3. Dip coating process

In this process, the PCB board is immersed into a paint tank for coating. This is a common process in the industry. However, it is not recommended to use the dip coating process during manufacturing PCB boards and electronic products, because PCB boards should have a certain thickness. If the PCB board is immersed in a transparent coating, most of the transparent coating will adhere to the surface of the PCB board, and some will remain in the paint tank. This will result in uneven distribution of the transparent coating on the PCB board.

Every PCB has a fatal weakness: water. Apart from conformal waterproof coating, are there any other solutions?

Conformal waterproof coating is one of the most useful and popular materials used to protect PCB boards. It is a thin and flexible protective material that can be sprayed on PCB boards to make them waterproof. It can be used to protect PCBs in many different environments. However, although conformal waterproof coatings are widely used, in some cases, they are not effective enough to protect PCB boards. Generally, there are two main reasons for this:

1. Conformal waterproof coatings have low adhesion and do not effectively prevent water from seeping into PCB boards.

2. Even if conformal waterproof coatings can prevent water from seeping into PCB boards, they may still be damaged in humid environments or environments with strong corrosiveness.

In the past, PCB manufacturers only used conformal waterproof coatings to protect their PCB boards. They did not have any other solutions and did not find other ways to solve this problem. That is why they always had to pay attention to the design of PCB boards and use special PCB materials to make them waterproof.

The question arises: I use waterproof casing. Why do I need conformal coating?

Conformal coatings are different from casings. But if you need to make electronic products waterproof, you will use a casing. Casings are used to protect your electronic devices from water and air. They act as a tent that can protect your electronic products or PCB from the effects of water, air, corrosive gases, and other harmful factors.

Usually, conformal waterproof coating is sprayed on the surface of the PCB board to make it waterproof.

So, which one do I need?

1. If you want to manufacture electronic products or waterproof circuit boards, you definitely need conformal waterproof coating and a casing. If the environment is too corrosive or humid, it is recommended to use both materials at the same time. In some cases, you only need to make your electronic products or PCB waterproof. In this case, you can use a conformal coating without a casing. In humid and corrosive environments, you can use a conformal coating to protect the PCB from moisture. It is strongly recommended to use a conformal coating to protect your electronic products or PCB boards in humid and corrosive environments.

2. If you have a specific purpose for making waterproof PCBs, you do not need to use conformal waterproof coatings at all. For example, when manufacturing PCBs for control systems of ships or submarines, these materials are not necessary because water seeping into the control system is not allowed, which could lead to sinking of ships and submarines.

There are many methods to waterproof circuit boards or electronic products, and you can choose one according to your needs. If you need to make your electronic products or PCB waterproof in a humid environment, it is recommended to first use a conformal coating and then use a casing. This way, your electronic products or PCB will be well protected, not only from the effects of water but also from corrosion and other harmful factors.

How to test or check if the coating is on the surface?

1. The first method is to test the surface using other types of coatings (such as epoxy resin or silicon). If you use the above types of coatings, they will not adhere to the surface of the PCB board if it has a conformal coating.

2. The second method is to use alcohol spray and then check for water droplets on the PCB board. If there are water droplets, it means that your PCB board is covered with a liquid conformal coating.

Does the application thickness affect conductivity?

Usually, if you use too much conformal coating, it can make your PCB board more conductive. However, this depends on the thickness and type of material used to make the liquid conformal coating. If high-quality materials with good conductivity are used, it will not affect the conductivity of the PCB board.

Are there any drawbacks to excessive coating or applying too thick of a surface?

When you use too much conformal coating material, your PCB board will not be able to effectively dissipate heat and supply power. This will lead to significant heat dissipation and current, which can be very harmful to your electronic products or PCB.

Do I need to coat the conformal coating on solder joints?

You can spray conformal waterproof coating on solder joints, but it is not recommended, as it can lead to issues such as short circuits and poor conductivity. Solder joints are mainly used in electronics and PCBs to connect components together. It is not an electronic component itself. Solder joints are never covered by any conformal coating. If you apply conformal coatings to solder joints, conductivity will be reduced, leading to a decrease in performance of your electronic products or printed circuit boards.

You also need to consider the weight of the PCB board. If you apply too much conformal waterproof coating on the surface of the PCB, it will be heavy and unbalanced. A heavy and unbalanced PCB can cause malfunctions during the assembly process.