Today, there is no electronic device existing that does not contain PCBs in its structure. The quality of the PCBs used in such devices directly relates to the normal functioning of the electronic devices later.
It means all PCB manufacturers need to pay great attention while designing and producing PCBs. It is because the performance of minor to major electronic devices enhances with these PCBs.
One way to make sure that the manufacturer is producing state-of-the-art PCBs is called PCB potting. In this post, we are going to have a detailed look at critical aspects of potting and how why it is important to ensure the quality of PCBs for integration into electronic gadgets.
What is PCB potting?
You can define Potting for printed circuit boards as a quality-check method that minimizes any chances that can damage electronic devices due to faulty PCBs. There are different external factors like chemicals, heat, and mechanical wear that can lead to further damage if not treated in time.
The process of potting includes a special potting material that functions similarly to a chemically formed encapsulation resin that secures the entire PCB board from the aforementioned complications.
Now, let’s discuss some prominent advantages of PCB potting below:
- Improves performance: One major benefit of using PCB potting is that it maintains the natural performance of electronic devices. It also boosts the circuit’s dependability by securing the printed circuit boards from possible threats, which include voltage issues, moisture, and alteration. Sometimes other factors like vibration and stress can create a negative impact on electronic devices, and potting helps with that as well.
- Reduce vibrations: It means potting blocks the vibrations created due to printed circuit boards and their holders. In case these vibrations exceed the limit, they can exert stress on the printed circuit boards and lead them to ultimate dysfunction.
- Tidy PCBs: The printed circuit boards can inculcate debris and dirt due to prolonged usage. Potting includes an encapsulated resin that helps in keeping the board tidy through all circumstances. Dirty and uncleaned PCBs can absorb more heat and hinder the signals, which hamper the performance of the electronic gadgets you want to use in.
- Privacy: Electronic devices cannot function properly if they lack security. For this, PCB potting is the best possible solution. The process makes the PCBs accessible and combines with engineering to ensure impeccable protection of PCBs.
Compound Guide for PCB Potting
Epoxy is among the favorite potting materials used by many PCB manufacturers. It is because it offers different benefits. It is better to have a quick look at the following benefits offered by Epoxy resins for the potting process:
- Epoxy has no parallel when it comes to adhesion
- Such resins do not need primers that speed up potting for PCBs
- They are excellent in tensile strength and stiffness
- Epoxy resins are good for use in transformers and agricultural machines due to their impressive chemical properties.
Silicone is another trusted potting material common to use. There are different applications of silicone except potting for PCBs. You will see different PCB manufacturers relying on silicone for potting. The following pointers will help you understand why is that:
- Silicone is good for potting because it has an impressive expansion ability
- Silicone is soft, and you can easily amend it in any desired form
- The temperature endurance of silicone stands the best when it comes to potting
- Silicone is not an affordable potting compound, but it does not exert any stress on the PCB components at all
We have Polyurethane which is among the commonly used potting materials. There are different reasons why Polyurethane is on this list. Let’s find them out below:
- Polyurethane is an expandable material that fits best for potting
- It resists mechanical wear and possible damage to PCBs and their parts
- It goes well with different natures of substrates due to its excellent flexibility
Merits and Demerits of PCB Potting Assembly
The method of potting is not a hectic one to perform. It is among a few effective and fruitful PCB-relevant processes that drive out positive results. Especially those PCBs that need a durable quality check method; there is no better option than potting itself.
The technique is also suitable for devices that need to avoid mechanical abrasion all the time. Potting enhances the longevity of these devices at the same time.
Experts believe that you can also consider a potting method to make sure vibration dampening, regulated heat emission, and protection of PCBs and their components are in place.
Choosing the Right PCB Potting Material
Since there are different potting materials available in the market, don’t get stuck with choosing the best for yourself. One main factor in evaluating potting compounds is their hardness.
- If a potting material is tough, it will provide better protection against weather complications like heat and moisture
- Hard potting materials are epoxy and urethane, along with silicone
- Silicone’s hardness ranges from 10A-60A, and it’s the hardest material you will find on the market
· Thermal conductivity
Another factor is the thermal conductivity. You need to make sure that the potting compound you are going to select meets the following standards of thermal conductivity:
- The compounds with an acceptable range of thermal conductivity are useful for potting.
- Epoxy and urethane can prove to be beneficial in terms of delivering a good amount of thermal conductivity.
- Silicone is the best with thermal conductivity and dissipates a large amount of heat produced by electronic devices, whether big or small.
A fine potting material must have the parameters of viscosity. In case you don’t know about them, check out the following pointers to learn about viscosity standards in detail:
- The perfect encapsulation of PCBs works flawlessly if the viscosity is less.
- If the potting material is self-leveling, it will contribute to achieving positive results.
- The potting compound should be easily adjustable to avoid any problems, and this only happens if the viscosity of the compound is less.
You cannot ignore the color of the potting material. Such compounds come in different colors, and each varies as per your situation. Let’s see how you can weigh down potting materials on the basis of their colors:
- Choosing an appropriate color of the material is necessary to enhance the presence and quality of the PCBs
- Sometimes obscure compounds can prove to be helpful in this aspect
- If you want to emphasize the LED visualization, then always go with the transparent potting materials available
Step-by-step guide for PCB Potting
One of the resins used for this process is POLYOL. However, polyol does not settle down with moisture easily at all. Due to this reason, if you’re using polyol, make sure to pre-bake the container.
Now, this pre-baking step will remove the slightest moisture present in the container. If you ignore pre-baking the container, the polyol will not be able to function naturally due to the presence of moisture inside the container.
- Marking the resin level
The amount of resin used for potting is crucial to determine. For this, if you mark the resin level, it will save you from possible fuss. So always mention the resin level on the container you are using. Plus, you also need to protect critical components of the PCBs by securing them from confronting abrasive damage when potting takes place.
- Preparing the resin
It is important to combine POLYOL and ISOCYANATE to develop a fine resin for potting. To do this, it is better to cover your face with a mask and wear neoprene gloves to save your hands and skin from this chemical reaction.
Now it’s time to extract a flexible compound from these two materials by keeping the ratio 1:6 for isocyanate and polyol. Now keep stirring the polyol with a metal bar to not let it accumulate due to fluctuations in the external environment.
Make sure you weigh the container in the first place before you add polyol to it. Now add polyol and mark down the change in the weight and keep adding the polyol once it reaches 6/7 of the weight of the resin you want to use for potting process.
Repeat the process with isocyanate but limit it to 1/7 of the weight of the resin you need to prepare. It’s time to merge both compounds by stirring this newly formed mixture.
- Pouring the resin
The next step is to add this resin mixture to the PCB container. Keep the bucket tilted at a 3-degrees angle. If you keep a smooth pad under the container, you can make the exact angle to avoid any troubles.
Now start pouring this resin into the PCB container till it reaches your marked level. Leave the entire setup at room temperature for a while and wait. After some while, put this setup into an oven and bake at 80 degrees for at least one day.
- Checking the final quality
Next day, you need to take out the PCB container from the oven. A special tool called Analog Shore which helps in analyzing the hardness of the resins, will assist you in testing your resin finally.
The shore should show the reading to be within 85-90. If you get this reading, it means the resin you have prepared is suitable for the potting process.
Different Between PCB vs. Conformal Coating
In this section, we are going to compare regular PCB potting and conformal coating. However, it is important to know the major differences between the two so that you can find out what type of methods will be suitable for you as per the situation.
There are different use cases for both these methods. Due to this reason, we are going to make it easier for you to choose the best method for easy implementation.
Before we hop onto their differences, let’s see what similarities between these two methods are:
- Both techniques are beneficial in protecting the substrate from external factors like a moist environment, excessive vibrations, and rapid corrosion.
- Both methods promise better results and can prove to be fruitful with the final product.
Below are some major differences between the two methods:
- PCB potting is better for those devices that function on the basis of fewer vibrations, minimal abrasion due to interaction with chemicals, and heat dissipation. Potting works best for those devices that are robust and often face challenges like the above.
- The resins used for potting process are excellent for avoiding electrical glitches. Due to this reason, one of the major use cases of PCB potting is integration in high-voltage electronics.
- Conformal coating, as compared to potting, is a slow and hectic process, whereas potting takes place smoothly in a short period of time.
- Conformal coating never requires repairing and checking, unlike potting, which can create a negative impact on the components of PCBs.
- The conformal coating also does not exert any pressure or stress on critical or minute PCB parts like pins, wires, and screws, unlike potting, which can compromise your substrate.
- You can easily perform conformal coating in a small enclosure which works on minimal devices, which is not true for PCB potting that only, takes place in large containers.
Which Potting should you choose for Better Results?
Now you might be wondering what type of method you should go for that promises better protection for PCBs.
Let’s find that out in this section:
For PCB potting:
- The protection of PCBs mainly depends on the type of potting resin you want to use and also the type of product.
- It is important to understand and learn about the potting resin completely to make sure it performs well and does not compromise the process at any cost.
- During the process of potting, it is crucial to regulate the temperature and maintain it within a suitable range to avoid complications.
- One drawback of this process is that when you merge the resin with the hardening substance, it will give out a large amount of heat that entirely disrupts the PCB structure.
For conformal coatings:
- If you consider conformal coatings, you must know the resins differ in their resisting power.
- In most cases, water does not harm the resins, but double-checking the resin proves to be helpful.
- Resins used in conformal coatings absorb the trauma and protect the PCBs from possible damage.
- However, there are some definite downsides of conformal coatings as well, such as more velocity can damage the PCBs and might also leave impressions on their structure in extreme cases.
- The conformal coating method is good for designing in a freehand style.
- Such a method offers complete securing of electronic devices irrespective of daily usage.
Factors to Consider While Designing PCB Potting
The designing criteria for conformal coatings and potting require your attention as we move toward the conclusion of this discussion.
- If you develop a film of resin on the upper surface of a PCB, it will increase its weight.
- If the resin is more rigid, it will not let the electronics perform in a natural way.
- Such a resin which is rigid and inappropriate, will exclude any margin of future changes if needed.
- Now if you try to exclude a pre-attached rigid resin from the PCB, it will damage it and can cause irreversible abrasion as well.
- Some coatings are transparent, which makes their usage easier and faster during the technical PCB assemblies.
- Such coatings can prove to be useful in protecting sensitive parts of PCBs.
- You can use a brush or spraying bottle to add the coating to PCBs or simply submerge the PCB into the coating.
- You can replace encapsulation with these coatings to ensure complete protection of PCBs without spending extra on cost.
You must know by far that both these methods are crucial to increase the life length of advanced PCBs. These methods are cost-efficient at the same time.
However, some factors, like their pros and cons and the complexity of both these methods, might give rise to newer and much easier technology for protecting PCBs. Hopefully, now you can easily choose the best technique and get your projects running in no time!