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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

Electronics continue to be placed into harsher environments, and PCB component vibration dampening remains a challenge for many industries. When the solder connection strength is not going to be sufficient to withstand years of vibration, there is a solution: staking materials.

Numerous fields of industry manufacture products that are prone to high-vibration environments. Some of them are:

Have you ever seen your conformal coating separate or de-wet?  Have you observed the conformal coating to flake off after cure? The key to your success is understanding the relationship between surface energy (of the substrate) and surface tension (of the conformal coating).  There are some simple steps you can take to help ensure you possess a healthy balance of both.

The application of the conformal coating in a uniform and consistent coverage is a key challenge that defines the reliability of the finished product.

A thin coating will provide inadequate protection against corrosion or insulation between conductors. Conversely, if the conformal coating is too thick, it will increase the risk of forming other types of coating defects such as bubbles, insufficient curing, and potential cracking during thermal shock cycles.

Besides the verification of the process parameters such as coating viscosity and the application method is correctly setup, the amount of conformal coating material applied on the printed circuit boards can be measured before curing. For this, wet film conformal coating thickness gauges are used. This method ensures quality control while the coating material is still wet.