In the midst of a booming housing market, with homeowners more eager than ever to preserve and enhance their investments, roof coatings have emerged as an unsung hero. As a homeowner or property manager, understanding the types of roof coatings, their materials, and other factors in choosing the right one can mean the difference between a lasting investment or a costly mistake. Dive into this guide, designed to illuminate your path towards making an informed decision that will shield your home for years to come.
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When selecting a roof coating, it is important to consider factors such as the type of roof, climate conditions, desired properties (such as UV protection or hail damage resistance), and budget. Our comprehensive guide on choosing the right roof coatings provides in-depth information on different types of coatings and their properties, along with practical tips to help you make an informed decision. Additionally, consulting with a professional roofing contractor or manufacturer can provide valuable insights tailored to your specific project requirements.
Ultimate Guide to Choosing Roof Coatings:
Exploring Different Types of Roof Coatings
When it comes to roof coatings, an important consideration is the type. There are various types of coatings available in the market, each with distinct pros and cons. Your choice should depend on several factors, such as roof condition, environment, budget, and expected lifespan.
Acrylic Coatings
Acrylic coatings are water-based and known for their ability to reflect UV rays, making them energy-efficient. They also help extend roof life by resisting fading and providing a waterproof layer that helps prevent leaks&#;easy application means there&#;s no need for expensive equipment or specialized training. It&#;s an ideal choice for flat and low-pitched roofs made from materials such as metal, asphalt, concrete or polyurethane foam.
150% elongation implies that if original length is 1 m, it can stretch up to 2.5m before breaking
One advantage of acrylic coatings is that they offer a high level of flexibility during installation. They can be easily applied using a brush, roller or spray, allowing for extensive coverage with little material waste. Acrylics are also highly effective heat deflectors in hot climates and maintain elasticity even in temperatures as low as -20 degrees Celsius.
However, acrylic coatings do come with a few drawbacks. One significant disadvantage is that they perform poorly in areas with heavy rainfall or snowfall due to hydrolysis breakdown due to water ingress over time. While suitable for mild weather conditions, acrylic coating has difficulty adhering to damp surfaces creating bond failures leading to reduced durability.
Despite these challenges, many homeowners continue to opt for acrylic coatings due to their energy-saving properties and flexibility over multiple substrate types.
ProsConsEnergy efficientPoor resistance in areas with heavy rainHighly flexibleDurability reduced when exposed to moist environmentsEasy applicationGood heat reflectors
- A industry report highlighted that the global roof coating market was valued at around $2.1 billion in , indicating the substantial usage of these products worldwide.
- The same report projected that acrylic roof coatings, known for their UV resistance and overall durability, hold nearly 30% of the market share, reflecting consumer favorability towards this type of coating.
- According to a survey by Roofing Contractor magazine in , about 60% of roofing professionals recommend silicone roof coatings for flat roofs due to its long-lasting protection against ponding water, despite it being on the pricier side compared to other coatings.
- Acrylic coatings are a popular choice for homeowners due to their energy-efficient properties and flexibility over multiple substrate types. They reflect UV rays, extend roof life, and provide a waterproof layer that helps prevent leaks.
- Acrylic coatings can be easily applied using various methods such as brushing, rolling, or spraying, allowing for extensive coverage with little material waste. They are also effective heat deflectors in hot climates and maintain elasticity even at low temperatures.
- However, acrylic coatings may not perform well in areas with heavy rainfall or snowfall due to hydrolysis breakdown and difficulty adhering to damp surfaces, which can reduce their durability. Overall, acrylic coatings offer numerous benefits but have limitations in certain weather conditions.
Silicone Coatings
Silicone coatings have become increasingly popular in recent years due to their ability to withstand long-term exposure to ponding water. They provide excellent UV protection and can be used on various roofing materials, including thermoplastic single-ply membranes, modified bitumen, and metal. One of its most significant drawbacks is that it tends to hold dirt on the surface, making it look dirty over time. Additionally, it loses reflectivity as it ages.
Despite this, silicone coatings can be an excellent choice for flat roofs in areas with high precipitation levels or those prone to extreme climatic events such as hurricanes or hailstorms. Moreover, they do not become brittle over time and are resistant to dimensional instability caused by temperature changes.
Polyurethane Coatings
Polyurethane coatings are a fantastic choice if you&#;re looking for something that offers high rates of impact resistance and foot traffic. They are available in two types: aromatic and aliphatic polyurethanes. Aromatic polyurethanes tend to yellow over time when exposed to UV rays but are more economical than their aliphatic counterparts. On the other hand, aliphatic polyurethanes offer superior UV stability and color retention and are ideal for rooftops exposed to sunlight.
PropertyAromatic PolyurethaneAliphatic PolyurethaneColor StabilityDiscolours over timeRetains color wellWeather resistanceModerateExcellentFoot traffic resistanceHighVery HighCost-effectivenessEconomicalExpensive
To illustrate, suppose you&#;re the owner of a commercial building with a rooftop deck that serves as an outdoor lounge area for your colleagues. In this case, using polyurethane coatings would be a practical solution since the roof would experience high foot traffic regularly. For aesthetic purposes, you might choose aliphatic polyurethane coatings, despite the higher cost.
PropertyAcrylic CoatingsPolyurethane CoatingsSilicone CoatingsUV protectionGoodModerate to HighExcellentHail damage resistanceLow to moderateHighHighFlexibilityGood to excellentModerate to goodModerateReflectivityModerate to highHigh (aliphatic type)Low over timeCost-effectivenessEconomicalExpensive (aliphatic type)More expensive than acrylic
As we&#;ve seen so far, each roof coating type has its properties and uses. However, it is essential to bear in mind that before settling for one, careful pre-application preparation following the manufacturer&#;s requirements is fundamental for all roof coatings types. Additionally, proper storage of materials should be done to ensure their effectiveness.
Studies show that roofs coated with high-quality materials can reduce energy consumption by up to 30%.
Understanding Key Properties of Roof Coatings
Roof coatings are an essential component in maintaining the integrity, durability, and longevity of a building&#;s roof. They can help protect the underlying material from degradation due to weather, sunlight, and other environmental factors. Coatings come in various types and materials, each possessing different properties that can impact its suitability for a particular roofing application.
The right choice of coating for your roof will depend on several factors &#; location, weather patterns, type of roof, slope, roofing shingles and expected lifespan. Before making a purchase decision evaluate these considerations for a tailored fit. Understanding the key properties of each option can increase the chances of selecting the best roof coating solution.
Ultraviolet (UV) Protection and Reflectivity
Two crucial properties to consider when choosing roof coatings are UV protection and reflectivity.
Ultraviolet (UV) radiation from sunlight is known to cause severe damage to roofing materials if left unprotected. These rays are notorious for causing chalking, cracking, blistering, fading, and other forms of damage. A good quality roofing coating should have UV protection as it acts as a shield against such hazards.
Reflectivity refers to how much sunlight is reflected away from the surface of the roof coating. The higher the reflectivity rate, the more heat is kept out of the building. This helps reduce cooling costs by decreasing air conditioning needs during hot summer months.
MaterialTypical Reflection RateWhite Acrylic85-95%, depending on thicknessAluminum40-70%Asphalt8-35%, depending on colorElastomeric80%
Based on results from testing conducted by the Cool Roof Rating Council (CRRC).
It&#;s imperative to understand that choosing a type of roof intended for maximum UV protection or reflectivity based on just one consideration is often insufficient. Next, we&#;ll discuss how weather resistance and suitability for ponding water affect the choice of a coating option.
Weather Resistance and Suitability for Ponding Water
When evaluating roof coatings, some of the essential factors to consider include weather resistance and ponding water. In essence, the coating should have the capacity to resist extreme weather conditions such as scorching heat, heavy rainfall, high winds and hailstorms. Additionally, it should be suitable for areas prone to standing or ponding water. A quality coating will ensure excellent surface protection against moisture penetration and prevent leaks that could lead to more severe structural damage.
Take silicone coatings for instance; they boast exceptional weather resistance making them a superior choice in environments with long sun exposure. On the other hand, polyurethane coatings rank among the most durable options since they can withstand additional weight load making them practical for roofs with equipment or higher foot traffic.
A survey conducted among building owners revealed that 7 out of 10 believed roof coatings played a significant role in preventing leaks and water damage.
Making the Right Choice: Individual Strengths and Weaknesses
The type of coating you choose will largely depend on your unique individual needs. Consider these various strengths and weaknesses as you evaluate different coatings.
Silicone roofing coatings provide excellent UV radiation protection with reflectivity capabilities reaching close to 90%. They can withstand natural wear and tear due to their highly flexible properties making them an ideal option where significant temperature fluctuations are prevalent. However, they are relatively expensive compared to other coating types.
Polyurethane coatings are highly impact resistant, representing an excellent solution for high traffic roofs used as recreational spaces. Their comparatively thicker consistency makes them perfect in low pitch roofing scenarios &#; where water drainage is not that crucial &#; raising insulation effectiveness too.
Acrylic elastomeric coatings are typically cost-effective solutions intended for more minor repair works on roofs that have not yet suffered major damage.
EPDM rubber coatings come into play when maximum flexibility is required, providing exceptional durability while also offering reflective properties.
A similar characteristic comes with liquid rubber/synthetic elastomeric roofing which has a longer lifespan than other systems while also being UV and moisture-resistant.
Bitumen roofing is primarily used in colder areas since they provide a much-improved insulation value. However, they are less resistant to temperature change, which can eventually lead to degradation.
When choosing the best roof coating for your needs, it&#;s like selecting the ideal apparel for varying weather conditions. Just as you wouldn&#;t wear shorts and a t-shirt for a snowstorm, you wouldn&#;t coat your flat commercial roof with an unsuitable material.
Consider both short-term and long-term costs when making your development decision as each product has its own advantages and drawbacks that could add up considerably over time.
Costs and User Considerations
Roof coatings are an excellent choice when deciding to restore, repair or enhance the performance of your roof. In addition to enhancing overall durability, flexibility, and reflectivity, another advantage is the added insulation and water resistance it provides. However, as with any investment, cost considerations remain a critical factor.
Consider that silicone roof coatings, which have superior protective and insulating properties over other materials such as acrylic or asphaltic emulsion products, average costs around $3-$7 per square foot for materials alone. Combined with labor costs, these can easily range from $6-$10 per square foot.
While cost is a significant factor that you should keep in mind while choosing a coating type, consider the user&#;s usage pattern. For instance, weather patterns in your area could play an essential role in determining the most efficient and durable type of coating you would need.
Think of it like buying a car: The car&#;s price may be affordable initially; however, factors like maintenance cost and fuel economy make all the difference when purchasing.
Research suggests that roofs treated with thermal insulation coatings can extend their lifespan by an average of 20 years.
Making It Last: Application Preparation and Material Storage
Proper application preparation remains key to achieving thin-film consistency and ensuring an even protective layer after applying the coating. Therefore, before applying any roof coating material, ensure that your roof surface is clean, free of debris and dust.
Here are some steps to consider when preparing a roof:
- Remove dirt particles using power washing or air blowing
- Inspect roof substrate for defects such as cracks or blisters
- Replace damaged roofing components
- Ensure proper drainage
Another aspect to focus on is proper material storage. Improper storage procedures can compromise the quality of silicone roof coatings over time due to air exposure&#;s potential damage that can cause premature toll on its quality.
That said, let&#;s explore some factors regarding material storage that you should keep abreast with:
- Always keep the adhesive covered at all times when not in use
- Make sure it&#;s stored away from infrastructures that could compromise its qualities
- Store silicone roof coatings in a dry and cool area where temperatures remain stable between 50 to 80-degree Fahrenheit.
- Keep your kegs sealed to ensure air doesn&#;t flow inside.
Improperly sealed drums or incorrect temperature control during storage can shorten the shelf life of silicone roof coatings, thereby compromising its integrity.
By adhering to these guidelines, you can be assured of the longevity of your coating material performance while still ensuring roofing sustainability.
FAQs: The Ultimate Guide to Choosing Roof Coatings
1. What are the different types of roof coatings available?
There are several types, including acrylic, silicone, elastomeric, and polyurethane coatings. Each has unique characteristics and applications, suitable for different roof types and weather conditions.
2. Which type of roof coating is best for a flat roof?
Elastomeric and silicone coatings are often preferred for flat roofs due to their flexibility, durability, and ability to withstand ponding water.
3. How long does a roof coating last?
The lifespan varies based on the type of coating, quality of application, and environmental factors, but most can last between 10-20 years with proper maintenance.
4. Can I apply a roof coating myself or do I need a professional?
While DIY is possible, professional application is recommended for optimal adhesion and effectiveness, especially for complex roofing systems. Several companies offers expert services for roof coating applications.
5. Are there any specific considerations when choosing a roof coating for metal roofs?
Yes, coatings for metal roofs should have high adhesion, corrosion resistance, and reflectivity. Acrylic and silicone coatings are often used for their ability to contract and expand with the metal.
6. What are the benefits of using an elastomeric roof coating?
Elastomeric coatings offer excellent weatherproofing, energy efficiency, and can extend the service life of the roof. They are also flexible, which accommodates roof movement and temperature changes.
7. Can I apply a roof coating over existing shingles?
Yes, but it&#;s important to choose the right type of coating and ensure the shingles are in good condition. A roof inspection prior to application is recommended.
8. How do I determine the right amount of roof coating needed for my project?
The amount depends on the roof size, type of coating, and the manufacturer&#;s recommendations. Most data sheets provide coverage rates to help calculate the required quantity.
9. Is it necessary to clean the roof before applying a coating?
Absolutely. A clean surface ensures better adhesion and effectiveness. Remove all debris, dirt, and any existing loose coatings or sealants.
10. Are there any special maintenance requirements for roofs with coatings?
Regular inspections and cleaning are recommended. Be aware of any damage or wear and perform necessary repairs to maintain the coating&#;s integrity and effectiveness.
Conclusion
When choosing a roof coating, consider factors like local weather conditions, roof age, and energy efficiency needs. With a variety of options in the market, picking the right product is crucial for ensuring longevity and performance. For more details and tailored recommendations, refer to our comprehensive guide on our website, which includes links to manufacturers, detailed product data sheets, and community forums for further insights. Remember, the right roof coating can significantly reduce energy costs, extend the life of your roof, and improve the overall efficiency of your roofing system.
With the increased popularity of miniaturized electronics and circuitry, conformal coating use has skyrocketed to solidify its relevance in a wealth of modern PCB-related applications . Choosing the ideal type of coating and application methods for your electronics is crucial. However, processing the vast amount of information online can often present a daunting task.
Well, not anymore!
In this article, you&#;ll be given all the information that you need to identify the ideal conformal coating for your application&#;s requirements. If you are searching for something specific, feel free to use the index for a more selective approach. Otherwise, this article is helpful both for beginners who seek to understand conformal coating methodology and use, and for seasoned applicators and businesses who wish to confirm their knowledge-base and procedural legitimacy. You can also check out our selection of conformal coatings here.
For more Single-coating Line supplierinformation, please contact us. We will provide professional answers.
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Types of Conformal Coating
Application Methods
Thickness Measurement
Curing Methods
Removal Methods
Certifications
Regulatory Considerations
What is Conformal Coating
Conformal coating is a special polymeric film forming product that protects circuit boards, components, and other electronic devices from adverse environmental conditions. These coatings &#;conform&#; to inherent irregularities in both the structure and environment of the PCB. They provide increased dielectric resistance, operational integrity, and protection from corrosive atmospheres, humidity, heat, fungus, and airborne contamination such as dirt and dust.
What are the Types of Conformal Coating
There are several options for coating technologies, and the best option for your particular application should depend primarily on your level of necessary protection. The application method and the ease of rework are also important factors, but should generally be considered secondary to the necessary protective performance.
Traditional Conformal Coatings
What we call &#;traditional&#; conformal coatings are 1-part systems that have a resin base and can be diluted with either solvent or (in rare cases) water. Traditional coatings are semi-permeable, which is why they are not fully hermetic nor do they seal the coated electronics. They provide resistance to environmental exposure, which increases PCB durability while keeping application and repair processes in practice. However, they are NOT fully water-proof.
The following categories are based on the basic resin of each coating. The chemical composition of each conformal coating determines its major attributes and functions. Choosing the proper conformal coating for your application is determined by the operational requirements of your electronics.
- Acrylic Resin (AR) &#; Acrylic conformal coating provides fair elasticity and general protection. Acrylic conformal coating is recognized for its high dielectric strength, and fair moisture and abrasion resistance. What generally distinguishes acrylic coating from other resins is its facility for removal. Acrylic coatings are easily and quickly removed by a variety of solvents, often without requiring agitation. This makes rework and even field repair very practical and economical. On the other hand, acrylic coatings do not protect against solvents and solvent vapors, which could result in less than ideal performance for an application that involves something like pumping equipment. Acrylic coatings can be considered basic, entry-level protection, because they are economical and protect against a broad-level of contamination. However, they are not the best-in-class for any characteristic except possibly dielectric strength.
- Silicone Resin (SR) &#; Silicone conformal coating provides excellent protection in a very wide temperature range. SR provides good chemical resistance, moisture, and salt spray resistance, and is very flexible. Silicone conformal coating isn&#;t abrasion resistant because of its rubbery nature, but this property does make it resilient against vibrational stresses. Silicone coatings are commonly used in high-humidity environments. Special formulations that can coat LED lights without color shift or reduction of intensity are available, and make SR conformal coatings a popular choice for applications such as outdoor signs. Removal can be challenging, requiring specialized solvents, long soak time, and agitation from a brush or an ultrasonic bath.
Urethane (Polyurethane) Resin (UR)
&#; Urethane conformal coating is known for its excellent moisture and chemical resistance. It is also very abrasion resistant. Combining those factors with its solvent resistance results in a conformal coating that is very difficult to remove. Like silicone, full removal generally requires special solvents, long soak time, and agitation with a brush or an ultrasonic bath. Urethane conformal coating is commonly specified for aerospace applications where exposure to fuel vapors is a common concern.
The rest of this article is concerned mainly with what we call &#;traditional&#; conformal coatings, but we&#;ll first cover other coating types to provide a complete picture of the options available.
- Epoxy Conformal Coating - Epoxy resins (ER) are usually available as two&#;part compounds and create a very hard coating. Epoxy conformal coatings provide very good humidity resistance and are not generally permeable, unlike traditional conformal coatings. They also have high abrasion and chemical resistance. Typically, they are very difficult to remove once cured and are not as flexible as the other materials. Epoxy coatings are common in potting compounds, which in contrast to conformal coatings, completely cover the electronics in a solid and level layer of material.
- Parylene Conformal Coating - Parylene conformal coatings are a unique type of coating applied by vapor phase deposition. They provide excellent dielectric strength and superior resistance to moisture, solvents, and extreme temperatures. Because of the vapor deposition method, parylene coatings can be applied thinly and still provide excellent circuit board protection. However, removal for rework is very difficult, requiring abrasion techniques, and without access to vapor phase deposition equipment, recoating with parylene is impossible.
Thin Film /&#;Nano&#; Coatings -
A coating is dissolved in a fluorocarbon&#;based carrier solvent and applied with a spray or dip method to create a very thin coat, although not at a nanometer scale as the nickname suggests. They are commonly used to provide a minimal amount of hydrophobicity, which may prevent losses from very quick exposure to water. This type of coating does not offer the level of surface protection that other coating methods do.
How To Apply Conformal Coating
Once the type of coating is selected, the next question is how to apply the conformal coating. This decision should be based on the following variables:
The following are the application methods for traditional conformal coatings:
Photo courtesy of PVA
Dipping
- The circuit board is first immersed, then withdrawn from the conformal coating solution. Immersion speed, withdrawal speed, immersion time, and viscosity determine the resulting film formation. It is a common conformal coating technique for high volume processing. A great deal of masking is generally required before the coating process. Dipping is only practical when coating on both sides of the board is acceptable.
How To Measure Conformal Coating Thickness
Conformal coatings are usually applied as very thin coatings, providing the maximum amount of protection possible while still using the thinnest amount of material. The thinness of the coatings minimize heat entrapment, unnecessary additional weight, and a variety of other concerns. Common thickness with most conformal coatings is anywhere between 1 to 5 mils (25 to 127 microns) with some coatings applied at an even thinner level. Anything greater than this thickness is usually an encapsulate or a potting compound, which typically provides more mass and thickness to protect the boards.
There are three primary ways to measure the thickness of a conformal coating.
- Wet film thickness gauge
- Wet film thickness can be measured directly by using the appropriate gauge. These gauges incorporate a series of notches and teeth, each tooth having a known and calibrated length. The gauge is placed directly onto the wet film for the film measurement. See
http://www.geionline.com/wet-film-gauge
. This measurement is then multiplied by the percent of solids in the coating to calculate the approximate dry coating thickness.
- Micrometer - Micrometer thickness measurements are taken on the board (or on a test panel) at several locations before and after coating takes place. The cured coating thickness is subtracted from the uncoated measurements and divided by 2, providing the thickness on one side of the board. The standard deviation of the measurements is then calculated to determine the uniformity of the coating. Micrometer measurements are best taken on harder coatings that do not deform under pressure.
- Eddy current probes &#; The Eddy current measurement of conformal coating thickness uses a test probe that directly measures the thickness of a coating by creating an oscillating electromagnetic field. The thickness measurements are both non-destructive and very accurate, but can be limited depending on the availability of a metal backplane or metal under the coating, and the direct contact available of the test sample. Without metal below the test area, no measurements will be made, and if the probe does not fit flat on the test area, readings will be inaccurate.
Ultrasonic thickness gauge
&#; This type of gauge measures coating thickness using ultrasonic waves. It has an edge over the eddy current probes because it does not need a metal backplane. Thickness is determined by the amount of time the sound takes to travel from the transducer, through the coating, onto the surface of the board, and then back through the coating to the transducer. A conductive medium, like propylene glycol or water, is needed to provide good contact with the surface. This is generally considered a non-destructive test unless there is a concern with the conductive medium affecting the coating.
Curing Methods
While the curing mechanism is not a primary criterion when selecting a coating, it has a direct impact on the type of application method that will be feasible, and the throughput that can be expected. Some mechanisms are relatively infallible, while others are very complex and leave room for application errors when used in an uncontrolled process.
- Evaporative Curing Mechanism - The liquid carrier evaporates, leaving just the coating resin. Although very simple in theory, circuit boards usually need to be dipped at least two times to build up an adequate coating on the edges of their components. Whether the liquid carrier is solvent or water&#;based, humidity affects application parameters. Solvent systems tend to be easy to process, and provide consistent coverage due to good wetting, and fast cure times. However, solvents are often flammable, so adequate ventilation and fume extraction methods are required. Using water as a carrier can eliminate the flammability concern, although these coatings tend to take much longer to cure, and can be very sensitive to ambient humidity.
- Moisture Curing - Primarily found in silicone and some urethane systems. These materials will react with ambient moisture to form the polymer coating. This type of curing mechanism is often coupled with an evaporative curing. As carrier solvents evaporate, moisture reacts with resin to initiate final curing.
- Heat Curing - Heat curing mechanisms can be used with one or multicomponent systems, as a secondary curing mechanism for UV curing, moisture curing, or evaporative curing. The addition of heat will cause the system to polymerize or speed the curing of the system. This can be advantageous when one curing mechanism is insufficient to gain the curing properties required or expected. However, thermal sensitivity of circuit boards and components must be taken into consideration when curing at high temperatures.
UV Curing
-
Coatings that are cured using ultraviolet light offer very fast throughputs. They are 100% solid systems with no carrier solvents. UV curing occurs in the production line, so a secondary curing mechanism is needed under the components and in shadowy areas. UV cured coatings are more difficult to repair and rework and require UV curing equipment and UV radiation protection for workers.
How to Removal Conformal Coating
On occasion, it is necessary to remove a conformal coating from the circuit board to replace damaged components or perform other reworking procedures. The methods and materials used to remove coatings are determined by both the coating resins and the size of the area, which can impact the time required for removal.
The basic methods as cited by IPC are:
- Solvent Removal &#; Most conformal coatings are susceptible to solvent removal; however, it must be determined if the solvent will damage parts or components on the circuit board. Acrylics are the most sensitive to solvents hence their easy removal. On the other hand, epoxies, urethanes, and silicones are the least sensitive. Parylene cannot be removed with a solvent.
- Peeling &#; Some conformal coatings can be peeled from the circuit board. This is mainly a characteristic of some silicone conformal coatings and some flexible conformal coatings.
- Thermal/Burn&#;through &#; A common technique of coating removal is to simply burn through the coating with a soldering iron as the board is reworked. This method works well with most forms of conformal coatings.
- Microblasting &#; Micro blasting removes the conformal coating by using a concentrated mix of soft abrasive and compressed air to abrade the coating. The process can be used to remove small areas of the conformal coating. It is most commonly used when removing Parylene and epoxy coatings.
Grinding/Scraping
&#; In this method, the conformal coating is removed by abrading the circuit board. This method is more effective with harder conformal coatings, such as parylene, epoxy and polyurethane. This method is only used as a method of last resort, as serious damage can be incurred.
If all you are doing is replacing a component or working on an isolated area, it is common to simply burn through the coating with a soldering iron. In cases when this is aesthetically unacceptable, contamination is a concern, or components are densely spaced, coating removers are available in pen packaging.
Certifications
Certifications are an important way to distinguish general purpose varnishes and shellacs from engineered coatings designed specifically for PCB protection. Although there are dozens of user and industry specifications, the two major certifications are IPC-CC-830B and UL746E. When selecting a coating, look for the availability of 3rd party test documentation, rather than coatings with the claim that &#;they meet the requirements&#;. Both standards use the UL94 standard to judge flammability, with a V-0 rating signifying the lowest flammability potential.
IPC-CC-830B / MIL-I-C
This standard originated with the military standard MIL-I-C, which became obsolete in . The civilian version IPC-CC-830B is nearly identical, so it is generally understood that if a board passes the IPC spec it will also pass the MIL spec., and vice versa. IPC-CC-830B is a battery of tests, some are pass-fail and others provide data that can be referenced and compared to:
- Appearance
- Insulation resistance
- UV fluorescence
- Fungus resistance
- Flexibility
- Flammability
- Moisture and insulation resistance
- Thermal shock
- Hydrolytic stability
UL746E
Underwriters Laboratories (UL) is considered a credible and reliable safety certification body worldwide, and UL certification is commonly required for consumer goods. UL746E tests for the electrical safety and flammable safety of coated electronics. For electrical safety, there is a battery of tests similar to IPC-CC-830B, but with a cycling current load to constantly measure the failure of the isolative properties of the coating. The flammability test uses the UL94 standard like IPC-CC-830B, which involves attempting to light the cured coating with an open flame and observing the sustainability of the flame.
Once a coating has passed the UL746E standard, it can be registered with UL and assigned a registration number. Products certified and registered to UL746E standards can include the UL symbol (which looks like a backward &#;UR&#;). To maintain the registration, a coating must be retested annually.
Coatings can, and often are, tested to standards that only represent a portion of the whole standard. In the case of UL94, this is helpful when flammability is the main concern. Some specialty coatings may not be tested to the entire IPC-CC-830B or UL746E standards because they may fail parts of the test. These failures may be due to the nature of the product and the coating&#;s necessary applications, and are not always a reflection of the quality of the product. For example, some coatings intended to coat LEDs leave out the UV indicator to prevent color shift, but this automatically would cause disqualification under IPC-CC-830B. In other words, it is impossible by definition to pass IPC-CC-830B and have optical clarity in the UV part of the spectrum.
Regulatory Considerations
Safety and environmental considerations should always play a part in chemical selection and process design, but different regulatory bodies make this an even more challenging feat, as requirements must be interpreted and matched with product specifications.
OSHA (Occupational Safety and Health Administration) - In the US, the OSHA has overriding authority over worker safety concerns. Many coatings are very flammable, and many emit fumes that have a high level of toxicity. Close attention needs to be paid to ventilation (explosion-proof when dealing with flammable fumes) and the appropriate PPE (personal protection equipment) to keep operator exposure down below the appropriate safety threshold. Flammability may be difficult to avoid without exploring more specific water-based coating materials. Newer coatings have been introduced that do not include HAPs (hazardous air pollutants &#; a government classification of particularly toxic chemicals) like toluene, xylene or methyl ethyl ketone (MEK). The Global Harmonized System (GHS &#; with those red diamond symbols) needs to be followed for labeling, which is generally taken care of by the manufacturer. Make sure safety data sheets (SDS) are readily available to operators, as they should be for any hazardous chemical in a facility.
EPA (United States Environmental Protection Agency) &#; In the US, the EPA requirements must be followed at the national and regional level. The EPA, following the Montreal Protocol treaty, enforced restrictions on ozone-depleting chemicals. Since most of the restricted chemicals are unavailable and have not been used in conformal coating formulation for years, ozone depletion isn&#;t the current concern. If there are regional agencies (see next paragraph) that have stricter requirements than the EPA, those generally will need to be followed.
CARB (California Air Review Board) and other regional regulations &#; Local agencies continue to play a larger-and-larger role in environmental restrictions. CARB was one of the early regulatory bodies, laying down VOC (volatile organic compounds &#; smog-producing chemicals) restrictions by product category. Other regional agencies followed their lead. Global warming potential (GWP) is the latest environmental topic of discussion.
This concludes our guide on conformal coating. We hope that it answered your questions and provided proper guidance in selecting the best products and methods for your needs. Like any challenge, selecting the best coating and coating process can be broken apart, analyzed, and solved.
Now we want to turn it over to you...
What did you think of this guide? Maybe there is something we missed. Let us know by leaving a comment with your feedback. Techspray has experts available that will guide you all the way through the selection and qualification process.
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