Powder abrasion is an effective means for removing UV-curable materials.

UV-curable conformal coating materials 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.

Products are available for chemical removal of conformal coatings, but many are restricted by government regulation and health and safety concerns.
An effective method for localized removal of conformal coatings, allowing rework of components, is the powder or micro-abrasion equipment.

How it works. This method uses very fine particles of wheat starch, permitting conformal coatings to be safely and selectively removed. The wheat starch powder, being relatively soft, removes conformal coating from around components and solder joints without damaging the component markings or solder mask surface. The equipment is fully ESD-safe, using static-dispersive methods at the powder application tip and in the general work area.

The powder abrasion system has adjustable powder flow control and air pressure regulation to enable removal of a range of conformal coatings from the hardest to the softest. The key factors to ensure an effective coating removal are:

• Air pressure.
• Powder flow rate, which is the ratio of abrasive powder to airflow volume.
• Nozzle diameter.
• Distance of the nozzle from the work piece.
• Duration of the process application – feed rate.

The desktop unit is self-contained, requiring only manpower and compressed air to function. It has internal powder collection with built-in filtration. For a video of how powder abrasion works, go to https://youtu.be/q9501tpyveM.

Why use this removal method? The main benefits of using the microabrasion method for localized coating removal are its high precision and reduced time required. Microabrasion of conformal coatings is the modern way to remove coatings without using hazardous chemicals, and it provides a safe and clean environment for operators.

Figure 1.  UV conformal coating removed around a solder joint by thermal abrasion.

 
Figure 2. Examples of localized coating removal.

Vlad David is European senior sales and technical support specialist at HumiSeal (humiseal.com); vdavid@chasecorp.com.

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