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. 

In a previous blog “How to Save Time and Money by Measuring the Right Amount of Viscosity,” viscosity was described as critical to the conformal coating process. This post will cover some of the technical details related to coating flow rate and the significant potential for savings of both time and money for PCB manufacturers.

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:

Consisting of a resin and a hardener, a two-component epoxy can be formulated to offer a wide range of mechanical, thermal and electrical properties. While mix ratios differ, they all offer the ability to cure at ambient temperatures or elevated temperatures for faster cures. Here are a few tips to help you mix and apply your two-part epoxy.

UV curable conformal coating materials such as HumiSeal UV40 are frequently used in military, aerospace and automotive applications due to superior resistance to chemicals and mechanical stress. These properties make them difficult to remove when rework under the coating is required.

There are products available for chemical removal of conformal coatings, but many are restricted by government regulation and health and safety concerns.

An effective method for localised removal of conformal coatings, allowing the rework of the components, is the powder or micro-abrasion equipment.

Encapsulant solutions are commonly used to enhance protection of circuit boards from environmental and liquid contaminants, chemical attack, and electrical shortages. While potting materials provide many positive attributes when used to protect PCBs, sometimes other issues arise during and post application of these compounds. This blog focuses on “bubbles” forming within the encapsulant itself.

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.

The conformal coating process, like any other processes, has different variables, inputs, and outputs. In order to be able to control the results of your application (outputs), we need to fully understand how each variable affects the process. 

The importance of the variables

To get the right amount of liquid, thickness, right coverage, no contamination on keep out areas, etc., you need to identify and understand the variables of the process.

The most important variables:

• Viscosity
• Flow
• Machine parameters (speed and Height)
• Curing method

In this blog, we will concentrate on reviewing the first variable: Viscosity