Solder Mask for LED Applications: Formulation 101


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In 2007, the United States passed legislation to phase out the manufacture and trade of incandescent light bulbs, the EU following passed similar legislation in 2009. The rest of the world has been following suit creating a huge opening in the lighting market for a technology to fill the gap. Fluorescent lights have become more compact with less mercury, but they still contain the heavy metal that could become a problem in landfills in large amounts.

Until recently, LED lights were expensive and poorly designed for general lighting usage. The manufacturing price and, consequently, the retail price have come down significantly in recent years, while the energy efficiency and brightness of LED bulbs have gone up. These improvements in the technology have led to some projections of 45% growth every year for the next five years. With the growth in the industry, there has become a higher demand for LED materials and higher expectations for LED material performance.

Solder masks are traditionally green in color, and are expected to withstand the high temperatures present in solder pots, with a need for a different color like blue, red, or black arising every once in a while. The rise in LED production has called for improvements in the color white and the color stability of the mask in general. For the lighting industry, not only are the solder masks expected to perform well, but the formulator needs to have an understanding of properties such as reflectance in relation to color theory and how this will change as various formula adjustments are made for different applications.

What is Reflectance, and Why is it so Important? The property of reflectance is consistently named as one of the most important properties when considering a white solder mask for LED applications, but what exactly is reflectance? First, we must differentiate between reflectance and gloss.JG-Figure01.jpg

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Editor's Note: This article originally appeared in the February 2016 issue of The PCB Magazine.

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