This Article discusses different types of electronic circuit protection devices and how they protect electronic devices against ESD, water or corrosion.
The whole world runs on electronics, so it's easy to forget how insanely vulnerable the core devices are. Circuits are small, fragile things, and yet we put them everywhere and expect them to perform. In fact, our own experiences tell us that electronics are reliable pretty much anywhere.
There's a good reason for this feeling. Electronics are extremely well-protected in most cases, and they get that protection from enclosures. It's easy to understand. How often do you actually see a circuit board that is at the heart of any electronic device? Enhancements in electronic enclosures are a major part of the rapid progress of technology, and understanding more about them can help industrial applications make the most of new technology without destroying it in harsh environments.
To gain this understanding, we can look at three things. We can consider ingress protection ratings, how coatings and enclosures compare and contrast, and the primary sources of corrosion and how to beat them.
Ingress ratings are a formalized system that describes how well an enclosure or design can protect electronic equipment (or other equipment) from harmful particles. In general, ingress ratings measure protection against solid particles (like dirt and dust) and protection against water.
The IP Code is formalized by the International Electrotechnical Commission. The standard is known as EN 60529, and the code is updated every year. Despite those updates, the foundations of how the code works and what it denotes are relatively static.
IP code uses a two-digit system to rate ingress protection on two fronts. The code takes the form of "IPxy," where "x" refers to the solid particle protection and "y" refers to the liquid ingress protection. A higher number denotes better protection, so a rating of IP11 has very little protection (IP22 is typically the minimum for outdoor use), and a rating of IP69 is pretty much as good as it can get.
Keep in mind that the particle and water protections do not have to match. As an example, you can have an enclosure rated as IP53. In this case, the enclosure is well-protected from dust (not quite vacuum-tight) and can only protect against water spray. To be more specific, the 3 in the water rating means the enclosure is only safe if the spray comes as light, falling water. Direct splashing or direct pressure could compromise this example enclosure.
You can look at the full breakdown of the IP rating system to get a clear idea of what each number means and how products are tested and certified.
When you see how this formalized system carefully compares enclosures and ingress protection, you get an idea of what the protective layers are specifically aiming to accomplish. "Protecting against water" is not well-defined. "Tested for at least five minutes against a spraying water volume of 10 liters per minute at 50-150 kPA pressure" is extremely specific and shows you exactly what you are getting. This highlights the difference between marketing language and manufacturer specifications.
Coatings vs Enclosures
With a clearer idea of how protection works and what it is trying to do, we can explore the two most common methods of shielding electronic components: coating and enclosing.
The idea of coating is to put a custom material barrier between the electronics and anything that might harm them. The best-known coating for electronics is conformal coating. It is applied directly to the circuit board and consists of a small, thin material that is designed to increase surface insulation resistance and inhibit contact with harmful particles (such as water and dust). Conformal coating is very lightweight, and it is applied during the manufacturing of electronics. It is not a total barrier. Instead, it helps to protect electronics from indoor threats (including handling) until they are installed in a final device. Even after that installation, the conformal coating remains as a last line of defense.
In theory, coatings can extend beyond the well-known conformal coating. Any electronic device could undergo a final coating that offers an additional barrier. Non-corrosive substances are frequently used in such practices, but coatings have a fatal flaw. They cannot provide complete coverage of the device without restricting access to it. If you perfectly coat a material, there are no seams remaining that could be used for access.
Enclosures are the standard way to protect electronics from ingress. Every electronic device you have ever used sits inside of an enclosure. The electronics of your phone look very different from the case around them. Enclosures also can be nested to provide better protection. It is common practice for people to put their already enclosed phone into an additional case that further protects the device.
This is the normal approach to housing outdoor electronics. The device itself will have an enclosure with its own rating. That can then be housed in an additional outdoor enclosure that is designed to further protect from the elements. A great example of such an enclosure is a circuit breaker. The simple metal box keeps sun, rain and wind away from the circuit, and you can access the breaker as needed.
For more involved outdoor applications, or more sensitive devices, better enclosures are available. Non-metal enclosures can protect against rust and corrosion, and they can be made in any shape and size. They also are regularly manufactured to a variety of IP ratings.
Which Is Better
Ultimately, the best protection for electronics is a combination of coating and enclosing. The conformal coating provides an initial layer. A coated enclosure is placed around that device, and an additional enclosure (with optional coatings) can house the entire device. The real goal is to have several layers of defense that maintain protection if a single layer fails.
Water vs Other Sources of Corrosion
Water is bad for electronic devices for a lot of reasons. If it comes in direct contact, the conductive materials dissolved in the water can short the electronics and cause severe damage. Even worse, water can corrode the metals in the device. It can even corrode metal enclosures protecting the device.
To better understand how to mitigate corrosion, we should start by getting technical. Corrosion is a term that refers to the oxidation of a metal. When a metal substance has electrons stripped away, it undergoes a chemical change that can embrittle and damage the metal structure. This can happen in a number of ways. The two most common are corrosion from air and water. The natural acidity in air and water, as well as alkaline particles dissolved in either can corrode metal. So, you want an enclosure that is protected against these two threats. You also want to consider two other major sources of corrosion.
Any time an acidic substance comes in contact with metal, the potential for corrosion is present. This is how water corroded metal, but stronger acids can accelerate the process. Acids can be found in nature, and it's a risk for outdoor enclosures, but an even greater issue is industrial manufacturing. Many manufacturing processes use strong alkaline chemicals for any number of applications. Those chemicals can come in contact with electronic devices and cause severe, rapid corrosion.
It's easy to overlook, but electric currents can also corrode unprotected metals. A common way for this to happen is with standing water. The water won't house a strong current, but electric potential can naturally build up across a ponded area, and that can cause corrosion. Electricity is also a risk near electric grounds and around large static buildups. Designing enclosures around the risk of electrical exposure can prevent these issues.
Thinking about corrosion makes it easier to consider solutions. Protective coatings over metal is a common approach but minimizing metal in the system is also viable. Enclosures can be made from any number of non-metal devices (fiberglass being a great example) that still provide total protection and impressive tensile strength. You get everything you need from these enclosures, and corrosion is not a threat.
New, advanced enclosures are a vital part of protecting industrial equipment. They sit at the heart of the technological revolution underway, and every industrial application needs access to quality enclosures.
About the Author:
This Article is Written and published by Lee Drugan from Allied Moulded Products Inc.. Allied Moulded offers a full range of residential and manufactured housing products, including: Fiberglass and Polycarbonate Enclosures, Range/dryer receptacle boxes, floor boxes, lampholders, luminaires, and other products.