When we design a PCB board, it is inevitable that we have to face the problem of a wet environment, such as the rainy days or steam in the factory. Under this kind of situation, the circuit board will easily get damaged. In the past, we had to pay great attention to the design of PCBs and use waterproof material and special processing technology to make it waterproof. However, the complex process and high cost have made the PCB sales price higher than others. Nowadays, there are many kinds of techniques with high reliability to make a PCB board waterproof. We can use them to replace traditional methods.
How to Waterproof Your Electronics or PCBs:
It is always suggested that the PCB boards should be protected and stored in a dry place. It is a great idea to put the PCB boards in the sealed bag. Thus, PCB boards will not be affected by water and will not get wet even if it rains hard outside.
There are many ways to waterproof PCB. We can choose one according to our needs.
1.Apply waterproof material on PCB board
This method is used for very special purposes, such as making PCBs for control systems of ships or submarines, etc. In this way, you can add some special material on the surface of the PCB board to make it waterproof, such as Parylene C or Parylene N, etc. In fact, Parylene C and N are the same material. They are both high-density polymers, which can be made into thin layers. Generally, they are in liquid form when we apply them on the PCB boards. They will be solidified after a certain time, and become waterproof. The thickness of Parylene C is around 2 mils (0.05mm), which is much smaller than that of traditional varnish (such as epoxy resin). If you need to make your PCB board waterproof, you can choose Parylene C or Parylene N as your material.
2.Use Waterproofing Material to Seal up the Connectors
If you want to make a waterproof PCB, but not for special purpose, you can choose to use waterproof materials to seal up the connectors. The connectors are mainly used for connecting the wires and other components, such as wires, terminals and sensors. The connectors will be in contact with water directly when they are in use. If they are not sealed up carefully, the water will penetrate into your PCB board. When it happens, your electronics or PCBs will be damaged easily.
3.Apply special waterproof paint to the PCB board
If you need to make a waterproof PCB but you do not want to use special materials, you can use some paints. They are usually used as a protective layer. It is easy for you to 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 on the PCB board with high quality and low price. If you choose this method, it is suggested that you should select the best waterproof paint for your PCB board.
There are many kinds of waterproof paints on the market, but they are not all reliable and efficient enough.
Which application process is better? Dispensing, manual spray, or dipping?
This application process is the most commonly used to paint PCB boards. In this process, paints are stored in a hopper and then pumped into a gun. The paint will be sprayed onto the PCB board with the help of a spray gun.
This process is similar to dispensing, but manual spray can be used when you do not have a special painting machine or there are many different PCB boards for painting, which cannot be painted by dispensing. It is better to use manual spray rather than dispense method if you can because manual spray allows you to paint with high precision and makes the surface of PCB board smooth.
In this process, the PCB board will be dipped into the paint tank to be coated. It is a common process in the industry. However, it is really not recommended for you to use the dipping process when you are making PCB boards and electronics, because PCB boards should have some thickness. If you dip your PCB boards into the clear coat, most of the clear coat will stick on the surface of the PCB board and some will remain in the paint tank. This will result in uneven PCB coating of clear coat on the PCB board.
Every PCB has an Achilles heel: water. Is there a solution beyond conformal waterproof coatings?
The conformal waterproof coating is known as one of the most useful and popular materials used to protect PCB boards. It is a thin, elastic, protective material that can be sprayed on the PCB board to make it waterproof. It can be used to protect PCBs in many different environments. However, in spite of its wide application, conformal waterproof coatings have some problems. They are not effective enough to protect PCB boards under certain circumstances. Generally, there are two main reasons for this situation:
1.The conformal waterproof coating cannot effectively prevent water from penetrating into the PCB board because of its low adhesion strength.
2.Even if the conformal waterproof coating can prevent water from penetrating into the PCB board, it will be damaged in a wet environment or when the environment is too corrosive.
In the past, PCB manufacturers just used conformal waterproof coatings to protect their PCB boards. They did not have any other solution, and they did not find another way to solve this problem. That is why they always had to pay attention to the design of the PCB board and use special PCB materials to make it waterproof.
I Use Waterproof Enclosures. Why Do I Need Conformal Coating?
Conformal coating is not the same as an enclosure. However, you will use enclosures if you need to make your electronics waterproof. The enclosure is used to protect your electronics from water and air. It is like a tent that can protect your electronics or PCBs from water, air, corrosive gases and other harmful factors.
Generally, conformal waterproof coatings are sprayed on the surface of PCB board to make it waterproof.
So which one do I need?
1.If you want to make your electronics or waterproofing circuit boards, you will need both conformal waterproof coatings and enclosures for sure. If the environment is too corrosive or wet, it is recommended that you should use both of them together. In some cases, you will need to make your electronics or PCB boards waterproof only. In this case, you can use conformal coatings without enclosures. You can use conformal coatings for PCB protection against moisture in wet environments and corrosive environments. It is highly recommended that you should use conformal coatings to protect your electronics or PCB boards in wet and corrosion environments.
2.If you have a special purpose for making a waterproof PCB, you do not need to use conformal waterproof coatings at all. For example, when you are making PCBs for the control system of a ship or submarine, etc., there is no need for these kinds of materials because it is not allowed that water penetrate into the control system which can cause the ship and submarine to sink.
There are many ways to waterproof circuit boards or your electronics. You can choose one according to your needs. If you need to make your electronics or PCBs waterproof in a wet environment, it is recommended that you use a conformal coating first, and then enclosures. In this way, your electronics or PCBs will be well protected, not only from water but also from corrosion and other harmful factors.
How do you test or check if the coating is on the surface?
There are two common ways to check if the coating is on the surface or not.
1.The first method is to test the surface with some other types of coatings such as epoxy resin or silicone. If you use the above types of coatings, they will not stick onto the surface of your PCB boards if the surface is coated by conformal coating application.
2.The second method is to use alcohol spray and then see if there are water droplets on your PCB board. If there are water droplets, it means that your PCB boards are coated by liquid conformal coating.
Does the applied thickness impact conductivity?
Normally, if you use too much conformal coating application, it will make your PCB board more conductive. However, it depends on the thickness and type of materials you use for making your liquid conformal coating. If you use high-quality materials with good electrical conductivity, it will not affect the conductivity of your PCB board.
Are there disadvantages for a surface that has been over-applied or applied to be too thick?
When you apply too much conformal coating materials, your PCB board will not be able to have effective heat dissipation and electricity efficiently. It will result in a huge heat dissipation and electricity which is very harmful for your electronics or PCBs.
Do you need to apply conformal coating on solder terminals?
You can spray the terminals with conformal waterproofing coating, but it is not recommended because it can cause some problems such as short circuit, poor conductivity, etc. The solder joint is mostly used in electronics and PCBs to connect components together. It is actually not an electronic component itself. The solder joints are never covered by any conformal coatings. If you apply conformal coatings to the solder joints, the conductivity will be decreased and it will cause poor performance of your electronics or PCBs.
You also need to pay attention to the weight of the PCB board. If you apply too much conformal waterproof coatings on the surface of PCBs, it will be heavy and unbalanced. The heavy and unbalanced PCB board may cause failure in the process of assembling.