Typically applied at m, these coatings conform to the contours of the board allowing for excellent protection and coverage, ultimately extending the working life of the PCB. Due to the rapid expansion of the electronics industry, conformal coatings are also finding their way into the domestic and mobile electronics industries, providing the necessary combination of high performance and reliability within a vast array of electronic devices. Conformal coatings can be used in a wide range of environments to protect printed circuit boards from moisture, salt spray, chemicals and temperature extremes in order to prevent corrosion, mould growth and electrical failures, for example. The protection provided by conformal coatings allows for higher power and closer track spacing, in turn enabling designers to meet the demands of miniaturisation and reliability. The range of products currently available comprises acrylics, silicones, polyurethanes, hybrid chemistries and environmentally friendly options. Electrolube can offer both transparent and pigmented coatings to improve or camouflage the appearance of printed circuit boards.

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Ease of processing and ideal for those applications requiring rework Water-Based Coating Water based coatings cure by evaporation of water from the system.

They are low-VOC options, replacing the majority of solvent in the system with water. This improves operator safety and also dramatically reduces solvent emissions.

Reduces solvent use; improves operator and environmental safety Electrolube products are NMP free; again offering a safer product Electrolube products are hybrid products offering enhanced performance Can be applied using standard equipment; dipping and spray versions available Can offer a good level of chemical resistance UV Cure Coating UV cure conformal coatings are also another example of hybrid coatings.

In this case, different chemistry types are often used to produce a dual-cure system, thus avoiding issues with areas shadowed from the UV light during curing. UV cure coatings offer the fastest curing times with coatings curing in seconds under UV light. This is extremely beneficial for high throughput applications and any shadowed areas will cure via the secondary cure system over time. Due to their highly cross-linked structure when cured, they can be difficult to remove and in some cases UV cure coatings are known to suffer from reduced flexibility during thermal changes and therefore must be carefully tested.

Extremely fast process times Secondary moisture cure system used to help shadow areas cure Good protection in a range of environments Excellent chemical resistance 2K Coatings 2K two part coatings are hybrid technologies combining the best properties of encapsulation resins with those of a conformal coating. These materials offer some of the best protection available while maintaining the processability and cost effectiveness of a conformal coating compared to a resin.

The application method of a conformal coating is AS important, if not MORE important than the selection of the right material for your application. This is because even the best coating, when applied poorly will not provide the right levels of protection required.

How do I Cure a Conformal Coating? 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 Cure Conformal Coating 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 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 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.

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.


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