Electronics Assembly Knowledge, Vision & Wisdom
Ultrathin Fluoropolymer Coatings to Mitigate PCB Damage
Ultrathin Fluoropolymer Coatings to Mitigate PCB Damage
Ultra-thin fluoropolymer coatings were tested by industry approved test methods to determine whether this level of process was possible.
Materials Tech

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Adhesives, Chemicals, Cleaning Solutions, Coatings, Components, Design, Embedded Technology, Fasteners, Finishes, Flex Circuits, Flip Chip, Fluxes, PC Fab, Solders, Solder Masks, Solder Paste and more.
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Authored By:
Erik Olson, Molly Smith, Greg Marszalek, Karl Manske
3M Company
St. Paul, Minnesota

Summary
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. Ultra-thin 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, ultra-thin fluoropolymer coatings were tested by internal and industry approved test methods, such as IEC (ingress protection), IPC (conformal coating qualification), and ASTM (flowers-of-sulfur exposure), to determine whether this level of protection and process ease was possible.

The fluoropolymer coatings chosen for this test were created in a range of coating solids and application thicknesses (100 nm to 30 um). 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 fluoropolymer coating played a significant role in the level of corrosion resistance and water/vapor repellency results. The data generated demonstrates a general correlation of how thick an ultra-thin fluoropolymer coating must be in order to achieve certain levels of protection.

Conclusions
Protection of printed circuit boards and their components is an increasing concern as electronics are used in more environmental conditions. Sulfur, water vapor and water immersion can significantly shorten the working capabilities of an electronic device.

The testing above highlights how ultra-thin fluorochemical coatings and their thicknesses needed, can provide an effective barrier for metals, surfaces and electronic circuit boards for protection from sulfur, moisture, liquids, and corrosion. This barrier adds to the performance, longevity and reliability of the surfaces, metal connections and an electronic device's service life.

Initially Published in the IPC Proceedings

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