Why use conformal coatings

Suitable for low volume manufacture, finishing and repairing units. Requires highly skilled operatives to get a suitable protection level. Coatings are applied with a spray aerosol or dedicated spray booth using a spry gun and is the most suitable method for low to medium volume manufacture. Most coatings can be applied this way.

After boards are conformal coated they will then need curing either by air dry, oven dry or UV light cure. Once the process of coating has been completed the coating is clearly visible as a clear and shiny material, some are hard while others have a slightly rubbery texture.

The team at 4e have been applying conformal coatings for nearly 20 years in military, medical and aerospace products. Meanwhile, Stock Electronics, which has produced motor control products for outdoor and harsh environments for 30 years, continues to use a range of conformal coatings across its product portfolio. How does conformal coating work? This is because even the best coating, when applied poorly will not provide the right levels of protection required.

Solvent based coatings cure by evaporation of solvents, this process can be accelerated in most cases by using heat, however this can affect the properties of the coating and cause coating defects if not performed correctly. Without heat cure, it offers good humidity protection. AFA , a non cross-linking solvent-based acrylic on the other hand, will reach the same protective capability regardless of the curing conditions, the use of heat just accelerates the process.

UV curing uses intense ultraviolet light to set off a chemical reaction within the coating in order to cure almost immediately in areas exposed to the UV radiation.

Due to the 3-D nature of most assemblies there will nearly always be areas that remain unexposed to the UV radiation e.

This is considerably faster than the industry standard, with a full cure guaranteed in just hours compared to up to two weeks or more with some products. UV curing materials are popular in high throughput environments, since in most cases the parts can continue through the process within seconds of the curing process, thus speeding up manufacturing velocity and reducing Work In Progress WIP.

Moisture cure coatings require moisture from the atmosphere to cure. The humidity in the atmosphere can affect the speed of cure; increasing the humidity will often speed up the process.

Humidifiers can be added to conventional and IR ovens to provide greater humidity and accelerate this process.

It is important that these products are handled with care. If containers are left open for long periods of time then moisture will be absorbed and the coating will begin to cure. In the case of dip coating a dry argon blanket can be passed over the surface of the tank to ensure that the coating is kept dry whilst processing. Conformal coating standards are a series of specifications and tests which a coating must pass in order to be considered for use in certain environments such as Military or Automotive applications.

In addition they may be recognised by Underwriters Laboratories, either as a permanent coating, in which case the flammability of the coating is assessed to UL94V0, or as a conformal coating, where the electrical properties will be assessed as part of the ULE standard. Whilst perfectly acceptable to assess the potential performance of the material, the actual protective capability of the coating in the end use environment is of greater concern to the user.

The rest of this article will be devoted to understanding the issues that relate to end use performance in potentially corrosive environments. While it has been inactive for new designs since , it is still a standard often required by military contractors. The main advantage of MIL-IC is that it requires independent testing by a MIL approved laboratory although at least one conformal coating manufacturer is an approved test laboratory so not completely independent!

Whilst similar in requirements to MIL-IC, this standard is based on supplier self-certification. CC is an active specification and is continually being updated. Once again, there is no requirement to use an independent test laboratory, and there is no QPL maintained for this specification. V-0 is the highest classification that can be achieved, with other categories such as V-1 and V-2 denoting materials that burn for longer durations.

ULE ULE is composed of a series of dielectric breakdown evaluations in addition to the UL94 flammability testing, and is intended to denote products that can be safely used on products that are required to meet UL safety standards. By documenting the use of UL recognised materials throughout the design, manufacturers can avoid the requirement to test their device to the applicable UL safety standards.

Policy:- Environmental Policy. VOCs contribute towards the formulation of ground level ozone. Such pollution can have many detrimental effects on the environment, damaging forests and vegetation. In addition, some materials classed as VOCs can act as irritants and over exposure can lead to a variety of health problems.

The main reason is that the boiling point of a substance is easier to identify and presumably more data are available than the vapour pressure at room temperature of the same substance. Nevertheless, the results of the two approaches for any one substance are, to the knowledge of the EU Commission, in most cases identical. WBP is for dipping application methods. RoHS regulations Read More. The requirements of conformal coatings can differ from application to application.

The most important properties that any conformal coating must have should be discussed first. To ensure the coating meets the desired characteristics, the coating needs to be exposed to a range of environments via appropriate test conditions to establish its performance range and limitations.

Advanced testing: Severe conditions such as salt mist, temperature extremes or rapid environmental changes. Electrolube put all of their conformal coatings through the test conditions outlined in these specifications and therefore, many other coatings from the range also meet the requirements of these standards.

For full info on Product test results, please view the product TDS available from downloads. Surface Insulation Resistance The electrical resistance of an insulation material measured between two contacts. When a board is coated it must have an electrical resistivity of ohms before environmental testing starts.

After the tests, this value should not decrease below ohms. Flexibility A coating must have a certain level of flexibility to ensure that all areas of the board will be coated sufficiently without any cracking or chipping upon cure. This will also ensure that the board can be moved and handled without damaging the coating and that an adequate level of flexibility is achieved in order to allow the PCB to expand and contract.

A strip of copper is coated and bent around either a 3mm mandrel to test. The coating must not crack, delaminate from the substrate. Adhesion Without adequate adhesion to the board the coating will not provide full protection. The cross-hatch test is a simple but effective way of measuring the adhesion of a conformal coating to standard circuit board materials. A special tool is used to score lines in the coating in both directions, forming a Cross-hatch pattern.

An adhesive tape is then applied to the cross-cut area and carefully peeled away then the coating is inspected to see if any of the squares produced have been removed from the substrate. Environmental Testing Environmental testing is essential to ensure the required level of protection is achieved. End-use conditions should be replicated or accelerated, however care must be taken to ensure accelerated tests are suitable for comparison with end-use conditions:. Environmental Cycling Based on UL test methods, the following environmental cycling profile can also be utilised:.

Humidity Tests Humidity is probably one of the most obvious causes of corrosion for PCBs as moisture in the atmosphere can react with metal components and connections on the board. Humidity testing is carried out on a conformal coating to make sure that the resistance to this humidity is maintained. Salt Mist Tests Salt mist tests are important for any board which will be operating in an environment where there will be salt present. They are required for certain features on the website and without them, the website would not function correctly.

If you disable this cookie, we will not be able to save your preferences. This means that every time you visit this website you will need to enable or disable cookies again. A conformal coating protects the circuit board during its lifetime of use A conformal coating is a protective non conductive dielectric layer that is applied onto the printed circuit board assembly surface to protect the electronic assembly during its working life.

What does the conformal coating look like? Where are conformal coatings used? How are conformal coatings applied? How critical is the application process? Privacy Overview This website uses cookies so that we can provide you with the best user experience possible. Strictly Necessary Cookies Strictly Necessary Cookies should be enabled at all times so that we can save your preferences for cookie settings.

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