I Use Waterproof Enclosures. Why Do I Need Conformal Coating?
February 10, 2021
From consumer electronics to medical devices, virtually every electronic device has an outer cover critical to its functionality. That is to say, almost every printed circuit board (PCB) is covered with an enclosure to provide necessary protection from the elements. However, conformal coatings, thin polymeric films applied directly to the PCB are also a popular means of protection. When is it best to use electrical enclosures as standalone protection, conformal coatings on their own, and are there circumstances when it is best to use both?
PCB Enclosures Versus Conformal Coating
If hermetically sealed, PCB enclosures can be a suitable means of protection. However, if not correctly sealed or degradation of the seal itself takes place, condensation build-up inside the enclosure can damage the electronics that need protection. Due to their ability to truly ‘conform’ to a PCB’s topography, conformal coatings can be a great solution when an enclosure is breached, acting as a secondary protection level for truly reliable safety. Considerations of either or both solutions is critical for any new project requiring reliability in compromising environments.
More About Enclosures – Waterproof Electrical Boxes Materials
There is a diverse range of PCB enclosures available in various materials, shapes, and sizes. Most of these materials consist of folded metal, plastic, or extruded aluminum. Other materials include fiberglass and stainless steel. The basic properties and benefits of folded metal, plastic, and extruded aluminum are discussed below:
The Most Common Enclosure Materials
Folded Metal Enclosures
Folded metal enclosures are formed from folded aluminum or sheet metal, typically with separate pieces screwed together, creating a box. This material can be a cost-effective option for applications that necessitate a large physical footprint.
- Lighter than steel
- Easy to modify
Extruded Aluminum Enclosures
Enclosures consisting of extruded aluminum can enhance the feel and aesthetics of devices but can be more costly. With enclosures made of this material, printed circuit boards are fitted into rails made up of aluminum extrusions.
- Customization is possible
- Some models offer enhanced environmental protection
Plastic PCB Enclosures
Plastic PCB enclosures are among the most cost-effective options, often used with ABS plastic, polyester plastic, Polycarbonate plastic, and PVC plastic. Each type of plastic has specific properties and benefits, and drawbacks. For example, Polycarbonate plastic is resistant to acidic environments and provides fire retention. On the other hand, this type of plastic may dissolve in solvents.
- Cheapest option
- Often provide features such as built-in battery compartments
- Easy to customize
How to Choose an Electronic Enclosure
It’s wise to consider many factors, including application requirements, protection capabilities, material, and performance standards, to choose the best electronic enclosure.
All told, application requirements come down to the market, including automotive, industrial, and IoT, and the product itself. Market considerations include specific use cases with individual needs, such as arenas, oil and gas rigs, and water treatment plants. Product application requirements involve the physical enclosure itself; an example may include ease of access.
Read our case study about making arenas more reliable by coating LED displays.
Elements such as corrosives, temperature extremes, and debris can impact an enclosure’s longevity and vary depending on the material’s resistance.
Material selection should be based on cost, durability, and availability – in other words, your needs. If you require malleability and corrosion-resistance, choose plastic. If your concern is cost-efficiency and durability, metal is a suitable choice.
Pertinent ratings, including Ingress Protection (IP rating) or NEMA, rated enclosures, should be evaluated to determine the amount of protection the PCB enclosure can offer. These standardized ratings are an excellent way to confirm that the enclosure will withstand specific environments.
For example, an IP66 enclosure is dust-tight and can withstand powerful water jets of 100 liters per minute at a distance of three meters, one minute per square meter for at least three minutes.
Download our IP checklist.
Why Do I need a Conformal Coating?
Although enclosures are virtually everywhere in the form of smartphone or smart surge protector casings, product design teams often choose to supplement this protection with conformal coatings, or when possible, replace the enclosures altogether. Conformal coatings consist of thin barrier layers applied to PCBs to protect sensitive circuitry from environmental threats such as corrosion. These films conform to a PCB’s form, providing reliable coverage. This protection can be trusted to work in various environments, improving reliability and mitigating risk in the form of recalls, repairs, and downtime.
With the right conformal coating material and application method, you can minimize PCB spacing, extend product lifecycle, and enhance your product’s reliability. Conformal coating materials include urethanes, epoxies, acrylics, silicones, and Parylene. Each has specific properties, benefits, and drawbacks, which should be carefully considered during material selection.
If not correctly sealed or degradation of the seal itself takes place, condensation build-up inside the enclosure can damage the electronics that need protection.
How to Select the Best Conformal Coating Application Method
Conformal coatings may be applied by spraying, brushing, dipping, dispensing, or vapor deposition. Even if you have selected the best conformal coating for your project, the protection will be inadequate if misapplied. Thus, the application method should be chosen with care.
Your choice may depend on:
- Quality requirements – automated application methods are more repeatable
- Masking and demasking requirements – this is the process of sealing off components such as connectors that should not be coated
- Board design requirements
- Sustainability requirements – some coatings utilize solvents and catalysts that can be harmful to the environment
- Curing requirements – Most coatings need to be cured (UV curing, heat curing, etc.) to reach optimal properties, which can be time-intensive
- Throughput requirements – including prep work, speed of the process, and how quickly the boards can be handled after coating
Download our definiteve paper on protection methods.
When You Need the Most Reliable Conformal Coating, Choose Parylene
Parylene is an ultra-thin coating that provides superior protection against extreme temperature ranges, moisture, and chemicals, as well as beneficial electrical properties such as high dielectric strength and low dielectric constant. Parylene is applied through vapor deposition, which deposits thin films of protection on a substrate, providing consistent and uniform coverage. Parylene can be utilized as either a primary protection solution or as a redundant backup solution for enclosures.
Learn more about Parylene.
For even thinner coverage than Parylene, learn more about nanocoatings.
The Big Picture
Ultimately, all protection solutions are device-dependent, and there are almost endless possibilities from which to choose. However, with a general understanding of enclosures and conformal coatings, along with the advice of a technical expert, you can select the best electronic protection method for your project. You will find that when it comes to electronics protection, there is no one-size-fits-all solution.
At HZO, we understand that you should not be pigeonholed into protection solutions and provide a turn-key solution that consists of processes, equipment, personnel, and material to provide best-in-class protection no matter what your needs are. Are you wondering if you should augment your enclosures with protective thin-films or nanocoatings or replace them with conformal coatings altogether? Reach out today for a consultation.
A general understanding of enclosures and conformal coatings, along with the advice of a technical expert, you can select the best electronic protection method for your project.
Ryan is a 9-year veteran to the world of protecting electronics from harsh environments and a lover of all things technology.