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Modern hydrogen fuel cell technologies require ever more sophisticated and reliable electronic control systems to assure both safety and longevity. Hydrogen fuel cells are gaining in popularity in critical industries including automotive, aerospace, ocean transportation, military, and power microgrid systems among others. Protection of printed circuit boards and their components from physical, chemical, and thermal damage is essential to produce robust and reliable fuel cell systems for demanding applications.

One of the most basic and common questions we at HumiSeal^® are asked by both existing and potential new customers is,

“How much does it cost to conformally coat my printed circuit boards?”

Since conformal coatings are usually sold in liquid form by the liter or gallon, it is necessary to go through a fairly basic calculation that we will present here.

The simplest and most common way to evaluate cost is by determining the cost in dollars of coating per PCB.

A critical function of conformal coatings is to protect PCBs and electronics from damage caused by moisture and humidity. In this discussion, we will attempt to answer some of the more common questions we often hear regarding the level of protection you can expect from a conformal coating.

Are conformal coatings waterproof?

The above is probably the most common question and most misunderstood subject in the area of PCB protection

In previous articles, we discussed common defects in conformal coatings related to surface energy issues. These included issues such as

• fish eyes
• lack of coating coverage
• poor bonding
• delamination

We received significant feedback, and the most common response was to ask for more specifics about just what surface energy is anyway.

The PCB industry continues to evolve with ever increasing demands for efficiency and manufacturing cost reductions. From the design phase onward, suppliers and contract manufacturers are being asked by their OEM overlords for increased performance at lower and lower costs. An obvious potential source for cost reduction is the use of alternative cheaper raw materials or their elimination where possible. At some point in the discussion, it is sometimes asked,  “Why don’t we just eliminate the conformal coating?” or "Are conformal coatings necessary".

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.

You have completed your search for an ideal conformal coating chemistry, one that will provide your PCBs the protection and reliability demanded by your industry and customers. After all that work, you probably assume your job is finished. Our apologies for being the bearer of bad news: There is still work to be done. In this basic presentation and discussion, we will talk about the proper choice and implementation of thinners for your coating. In many cases, a mistake in thinner can harm or even completely negate the protective properties of your conformal coating when applied to your PCB.

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.

The electronics industry is exploding with the introduction of innumerable consumer devices designed with ever more complex functions and controls. These range from the relatively mundane such as controlling the temperature in your home to potentially life-saving including deploying airbags in your car or sensing hazardous road conditions. The demand for smarter and more complex electronics is becoming more important in everyday life.