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Conformal coating of printed circuit boards (PCBs) has resulted in a steady evolution in performance and protection for modern electronics. It has allowed for lightweight and reliable controls in industries such as automotive and aerospace among others. This has brought about the possibility of increased length of warranties as well as fewer failures and claims. Nevertheless, original equipment manufacturers (OEMs) and consumers continue to raise their standards and expectations for longevity and reliability to levels unimagined just 10 years ago. In the automotive industry, as an example, thermal cycling testing might have involved as few as 10 or 50 cycles in the recent past. That standard is now often 500 or even 1000 cycles with no apparent ending in sight.

So what do I do when conformal coating is not enough?

Nobody likes masking, nevertheless it can be a necessary part of your PCB production process.

“But I thought selective conformal coating equipment had eliminated the need for masking in most cases.”

The cost of selective conformal coating equipment can easily run into hundreds of thousands of dollars. Even those who invest in the latest selective coating technology find, at times, that masking in certain areas is the only solution.

Have you ever seen your conformal coating look like the pictures above? It is a fairly common report to our technical support group. The appearance is often described as “orange peel” or sometimes “alligator skin.” We would like to offer you a basic explanation of this phenomenon, along with some simple approaches to avoid its occurrence or eliminate it when it appears.

What is orange peel and what is the cause?

In our experience, the uneven appearance that looks like the surface of your garden variety orange is almost always the result of exposing the coating to heat and airflow too quickly.

Xylene and Toluene. Two words that can evoke concern and add to paperwork for environmental health and safety departments and manufacturing professionals. Aromatic solvents have been safely used for decades by employing basic safety equipment including gloves, masks, and proper workplace ventilation. Nevertheless, concerns for maximizing employee safety and minimizing effects on the environment have led electronics manufacturers to seek out alternatives. For over 20 years, HumiSeal® has supplied a wide-ranging group of aromatic-free products across all traditional chemistries to manufacturers for whom these concerns are critical.

The evolution of conformal coatings for protection of PCBs and electronics has accelerated over the past few years. One development in particular has increased in popularity due to a promising array of advantages over its predecessors. These are LED Curable Coatings.

A partial list of existing technologies for conformal coatings would include:

• acrylics (both solvent and water-borne)
• solvent-borne polyurethanes
• silicone-based polymers
• synthetic rubber (solvent-borne)
• Parylene technology
• UV-curable acrylated urethanes (arc and microwave bulb source)

and most recently . . .

Picking a Conformal Coating

You and your organization have spent weeks or months researching conformal coatings to meet the demanding specifications of your customers. These can include factors such as dielectric strength, thermal and mechanical shock properties, processing considerations, and so on. At some point, the critical consideration of price and cost must be added to the equation. The amalgamation of cost and performance could be considered a measure of the true value of any specific coating. 

Conformal coating thickness is one of the most important characteristics to ensure long-term reliability of your electronics. A minimum coating thickness is essential to provide the required function of the conformal coating, but if a conformal coating application is too thick, it can actually have negative effects on your level of protection.

Which conformal coating thickness should be applied to reach optimal protection?

For decades, HumiSeal products have been considered the “gold standard” in electronics protection. As a result, it is no surprise that unscrupulous chemical manufacturers have been continuously trying to profit from this reputation through the production of copycat or counterfeit products. While imitation is considered the sincerest form of flattery, the use of counterfeit materials is a serious danger to the integrity of your electronics production. 

For many electronics manufacturers, the original justification for specifying a silicone coating is lost deep within the mists of time and it may be time for a re-evaluation and consideration of the question,

“Do we really need a silicone conformal coating?”

Humiseal® remains in a uniquely qualified position to help you answer this question. Unlike many coatings sources, Humiseal offers a full line of all the major conformal coating technologies including acrylics, urethanes, synthetic rubbers, water-borne, and yes; silicones. As a result, you can be certain of an unbiased approach to product evaluation that will result in the most cost-efficient material to meet your needs.

There are a number of factors to consider when evaluating your application to answer whether there is really a need for silicone technology:

IPC CC-830 revision B is a conformal coating qualification standard mostly used by board fabricators, OEM design engineers, and coatings suppliers.  

There are two fundamental uses of this IPC standard:

• Coatings’ performance capabilities
• Quality consistency

In this blog, we will go over some of the specifications along with tests requirements, passing criteria, and quality characteristics.