SMTA International Conference Proceedings

Ultrathin Fluoropolymer Coatings to Mitigate Damage of Printed Circuit Boards Due to Environmental Exposure

Authors: Erik Olson, Molly Smith, Greg Marszalek, Karl Manske, Nikesh Dhar
Company: 3M Company and Google
Date Published: 9/27/2015   Conference: SMTA International

Abstract: As consumers become more reliant on their handheld electronic devices and take them into new environments, devices are increasingly exposed to situations that can cause failure. In response, the electronics industry is making these devices more resistant to environmental exposures. Printed circuit board assemblies, handheld devices and wearables can benefit from a protective conformal coating to minimize device failures by providing a barrier to environmental exposure and contamination.

Traditional conformal coatings can be applied very thick and often require thermal or UV curing steps that add extra cost and processing time compared to alternative technologies. These coatings, due to their thickness, commonly require time and effort to mask connectors in order to permit electrical conductivity. Ultrathin fluorochemical coatings, however, can provide excellent protection, are thin enough to not necessarily require component masking and do not necessarily require curing. In this work, ultrathin fluorinated polymer coatings were tested by internal and industry approved test methods, such as IEC (ingress protection), IPC (conformal coating qualification), and ASTM (flowers-of-sulfur and salt fog exposure), to determine whether this level of protection and process ease was possible.

The fluorinated polymer coatings chosen for this test were created in a range of coating solids and application thicknesses (100 nm to 5 µm). Being a solution, these coatings were easy to apply by either vertical dip or atomized spray methods. In this study, it was found that both the application method and the thickness of the fluorinated polymer coating played a significant role in the level of corrosion resistance and water/vapor repellency. The data generated demonstrates a general correlation of how thick an ultrathin fluorinated polymer coating must be in order to achieve certain levels of protection.

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