The Ultimate Guide to Conformal Coating
With the increased popularity of miniaturized electronics and circuitry, conformal coating use has skyrocketed to solidify its relevance in an exceedingly wealth of contemporary PCB-related applications. Choosing the perfect variety of coating and application methods for your electronics is crucial. However, processing the vast amount of knowledge online can often present a frightening task. Conformal coatings are a skinny film of fabric applied to a completed circuit board that “coats” the board and its assembled parts with a protective substance for extra protection. The circuit boards that are included in these categories are consists of industrial uses, marine & automotive applications, and military & aerospace electronics.
However, with the value of their application dropping, conformal coatings are now accustomed protect circuit boards that operate in various environments that aren’t always as extreme. One example of products that are now coated with this conformal coating is wearable IoT devices like smartwatches. With the dense circuitry of wearable electronics and also the challenging conditions they need to control in, including vibration, moisture, and shock, the conformal coating has become necessary to make sure their uninterrupted performance.
Conformal Coating Spray for PCB
What is Conformal Coating?
Conformal coatings are a slim film of protective material that covers or “coats” an assembled board. Coatings are made up of non-conductive materials and might cover part or all of a PCB. Conformal coatings will cover areas of metal that normally aren’t covered with solder masks giving those areas additional protection from their operating environment. These sectors are included revealed traces, leads, and other metal on parts, and solder joints. Conformal coatings also will help protect a circuit board from stresses, rough treatment, chemicals, and corrosion and protect the components.
Circuit board conformal coating is different from, and will not be confused with, PCB surface finishing, which is an element of the fabrication process. A surface finish, like hot air solder leveling (HASL), will cover and protect the exposed metal of a bare board until its components are soldered on during the assembly process. Once the assembly process is completed, the conformal coating is applied to supply long-term protection for the PCB.
Is Conformal Coating Necessary?
Whether or not coating is required depends on the environment the electronics are employed in, the sensitivity of the electronics, and also the durability required. Mission-critical, IPC class 3 devices are more likely to be coated due to their critical nature. The increased popularity surrounding electronic miniaturization and wearable electronics has led to better demand for the additional protection and reliability offered by conformal coating.
Is Conformal Coating Waterproof?
Typically, conformal coatings don’t seem to be waterproof. These coatings are semi-permeable, so don’t fully water-proof or seal the coated electronics. They protect from environmental exposure, improving the sturdiness of the device, while still being practical to use and repair.
Advantages of Conformal Coating
Here are some advantages of Conformal Coating:
- Moisture Resistance
Conformal coatings are designed to supply resistance to moisture that would cause corrosion on PCBs. Moisture protection will vary betting on the kind of conformal coating used, the degree of cure of the coating, the presence of impurities, and the degree of adhesion onto the surface of the PCB. Conformal coatings can provide high levels of resistance to moisture but don’t seem to be completely impermeable.
- Insulation Resistance & Metal Migration
Conformal coatings block metal relocation from one place to another through the suppression of moisture integration and leakage current on PCBs. Metal movements between close area performing lines can happen when moisture, impurities, and partiality are all ready, potentially causing catastrophic shorting and abortion of PCBs. The application of conformal coating over tightly spaced components is very important to reduce the chance for potential metal migration and maintain a high insulation resistance.
- Corrosion Resistance
Conformal coatings provide corrosion resistance by creating a barrier to the penetration of corrosive factors like gases, moisture, salt, and chemicals. Gases like oxygen and sulfide can cause oxidation of metal surfaces or tarnishing of silver surfaces while CO2 and sulfur dioxide can form acids with the extra presence of moisture. Conformal coatings also provide protection to electronics that are exposed to marine environments where the chance of corrosion from salt exposure is higher.
- Biological (Fungal) Resistance
The decomposition of polymers in conformal coatings by microorganisms can have significant impacts on their physical and electrical properties. Degradation of conformal coatings by microbes can subsequently cause corrosion. Microbial resistance is especially important for PCBs which will be subjected to high humidity, tropical temperatures, or contact with soil. Most conformal coatings will either be composed of synthetic polymers and thus inherently proof against microbial growth or will have antimicrobial chemicals added to suppress growth.
Conformal coating Removal
When circuit boards need to be reworked or repaired, any applied conformal coating will first be removed. reckoning on the sort of coating used, removing it will be a challenge, and rework technicians will use one or more of those techniques to urge the duty done:
Many coatings will dissolve using different chemicals, but care needs to be taken to avoid damaging other nearby components on the board.
Coatings like silicone or other flexible materials will be peeled off the board.
In many cases, heat application through a hand tool will burn through the coating while the board is reworked.
- Micro blasting
Compressed gas combined with a soft abrasive is commonly wont to remove epoxy coatings.
Technicians often should grind and scrape the fabric off the board for harder conformal coatings like polyurethanes.
Although some coatings will be removed easier than others, it’s still an additional operation that will add time and complexity to board rework. Most contract manufacturers will advise waiting until a PCB has well-versed all its expected changes during prototyping and is prepared for full production before applying conformal coatings.