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What is PCB Insulation?
Introduction
A major function of PCB insulation is the protection of the PCB copper traces
PCBs are made of many components, but all of these are vulnerable to damage if there is no proper insulation.
In this article, we discuss at length what PCB insulation is all about.
What makes it successful? Are there specific items about it that are most relevant? How does this affect what you need to consider when designing your PCB?
Don’t pass up this chance to learn more about this fascinating subject.
What is PCB Insulation?
Definition: it is the protective covering, film, or substance that coats a circuit board.
PCB insulation is achieved using two primary methods. These are standard methods used by professional PCB manufacturers.
If you are doing a DIY PCB project, you can also achieve PCB insulation simply by following PCB design/construction basics.
PCB insulation is not necessarily expensive. Depending on how you want to achieve insulation, it could be either bought with the primary PCB material, or you could apply the protective layer yourself.
Why is PCB Insulation Needed
Why is PCB Insulation Needed?
Now that we have defined what is, we proceed to the next issue.
Why would a PCB need insulation? The answers are the following:
- The PCB traces will be at risk of unwanted interference.
- The PCB will be prone to thermal stress (heat too high), or worse, thermal failure.
- The PCB will not be able to power the components mounted on it.
- There is a chance of extreme electrical stress because of electrical overload.
When the circuit board malfunctions, the electronic device will malfunction—there is a chance it will be destroyed for good. We all don’t want that to happen.
Materials Used for PCB Insulation
There are two ways of achieving sufficient PCB insulation. These are through the application of the conformal coating and through the use of appropriate PCB substrates. We tackle both methods here:
Conformal Coating
The first type of PCB insulation is the type achieved using a conformal coating. This thin coat of chemical is applied onto the surface of the PCB. The coating then provides much-needed protection so that the board does not get affected by dust, oxidation, and possible chemical exposure.
Aside from protection, the secondary function of the coating is insulation—meaning, spacing between layers of PCB is reduced. Imagine it as the foam that fills the gaps between the contents of a box. Without the foam, there will be no cushion in between the contents of the box, which can be very bad for the contents of the box.
Conformal coating chemicals are: acrylic resin, epoxy resin, parylene, silicone resin, and urethane resin
The methods used to achieve coating include spraying, brushing, dipping, and selectively applying the coat on just some parts of the PCB.
PCB Substrates
The number one requirement for PCB substrates that are used for insulation purposes is the quality to be non-conductive.
Here is a video explaining the concepts of conductive and non-conductive in electronics:
The non-conductive quality of the board permits the flow of electricity in the board.
Specifically, the non-conductive parts support the conductive parts of the board. These conductive parts are the lines etched or drilled on the PCB. The conductive lines are where electricity runs to power the components of the board.
The following substrates are perfectly non-conductive and safe. They assume the role of PCB insulation for the whole circuit board.
- FR2 (Phenolic Resin) – Even though they are not so well-liked, some manufacturers continue to produce FR2 PCBs, which are made from hard paper and phenolic resin.
- FR4 (Fiberglass Epoxy Resin) – the standard PCB substrate, compatible with conventional PCB processing methods
- Ceramic PCB – a substrate that is preferred as it has high heat conductivity and a low coefficient of expansion.
- IMS (Insulated Metal Substrate) – Aluminum is used, or a metal plate could be a crucial component of the substrate.
- PTFE/Teflon – very similar to ceramic PCB in quality
- Polyimide/Flex – used for flexible circuit boards, has high heat tolerance up to 360°C
You can make use of some of these to control the insulation level of your board. Definitely, it will rely on your device’s specifications.
How to Choose the Best PCB Insulation Type
How to Choose the Best PCB Insulation Type
One way to control the performance of your board is by choosing the right PCB insulation type. To help you make up your mind, we give you factors that need to be reflected on:
First, consider the design of your PCB. Think of the measurements of the board as well as the material used. Is it a rigid board? A flex board? Or a rigid-flex board? There are different coatings for each type of PCB material.
Second, consider the level of protection needed for the PCB. This issue is connected with the environments the PCB would be exposed to. For example, some boards will be exposed to hot conditions, extreme cold, and sudden temperature changes. Some boards are needed in damp, humid, and even wet environments (i.e. waterproof PCBs).
Third, how about the issue of rework? Some insulation options perform better when reworked, take for instance heavy or thick copper PCB substrates.
Lastly, consider the practical reasons: cost and time. If you are using substrates for insulation, this will cut some time off production time. Meanwhile, customizing the conformal spray option may lengthen the production time.
Techniques Used to Achieve PCB Insulation
Techniques Used to Achieve PCB Insulation
PCB insulation is primarily achieved using two methods:
- Use a substrate that has the insulation properties you desire. The following are acceptable: FR4, Polyimide, Ceramic of PTFE, and even FR2. By choosing an all-in-one solution, you lessen the cost and time needed to complete the PCB. In this sense, use this method if you have a tight production deadline. Most PCB substrate manufacturers are reliable. They share information about insulation properties in the substrate’s data sheet. You can refer to the information by looking up the value of “surface resistivity” and “dielectric constant” values.
- Use PCB conformal coating, also called PCB insulation coating. For customers who have fewer time constraints. Yes, you can customize what conformal coating you need, but only to a certain extent. The better your PCB manufacturer, the more options you would have. That being said, conformal coatings should be able to protect your device against excessive heat, UV rays, potentially harmful chemicals, and water. If your device is marketed as waterproof, you have to rely on conformal coating instead of the substrate method. Verify the IPC grade to which your device belongs and the engineering questions that must be addressed.
Both methods have about the same level of effectiveness. Your decision will be influenced by your budget, your schedule, and the design/purpose of your device. Whatever conformal coating you need, make sure the manufacturer can deliver your demand. Subpar companies will not be able to deliver the service if they do not have large-scale equipment. This should be taken into account if you’re considering increasing production.
PCB Insulation Coating Facts
PCB Insulation Coating Facts
The PCB insulation coating is conformal coating, as previously discussed.
Here are some facts you need when considering its use:
- Conformal coatings have varying thicknesses. A thin layer would be 1mil, the medium would be 2-4 mil, while 5 mil is the thickest application.
- Measurement of thickness should be accurately determined, as this would affect the performance of the board. Normally, PCBs do not specify how thick the coating is. In product descriptions, the thickness is specified as part of the copper thickness of the board (e.g. 1 oz, 2 oz, 3 oz).
- PCBs already come with complete conformal coating, as this is the only way the items would pass IPC standards 2 and 3.
- The insulation coating needs to be removed, in some instances. In these scenarios, solvents can dissolve the epoxy resin. For more stubborn coatings, soldering irons or microbasting techniques can be executed.
Great PCB insulation coating application must result in total protection of the board. Dielectric resistance and a smooth flow of currents must be the end result in addition to this primary function.
Conclusion
A PCB with improved capabilities and top performance is the ultimate goal of using a PCB supplier.
To fill your requests, you need a company with the following qualities:
- They have a sufficient supply of high-quality raw materials (conformal coating + substrates)
- The business must perform thorough CAM file inspections before production to guarantee its accuracy.
- The PCB supplier must answer all your engineering answers.
- The price of the PCBs should be reasonable.
- They should always be willing to help with your custom PCBs.
- Additionally, it is important that the company follows international regulations when insulating PCBs.
Searching for PCB items with good insulation? Then, PCBTok is your supplier.