Blog

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.

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

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.

Does your conformal coating not wet properly? Do you struggle with craters, fish-eyes, or film separation? The culprit could be that the surface energy of your PCB is lower than the surface tension of the conformal coating.   The above defects are discussed frequently with customers on our technical support line, and any time we receive a technical enquiry regarding poor wetting or loss of adhesion, we ask “what is the surface energy of your substrate?” In this blog, we will explain surface energy, surface tension, and how to quickly troubleshoot defects resulting from low surface energy.