The increased temperature stress during lead-free soldering processes, especially during reflow soldering, causes a strong yellowing of some of the solder resists and marking inks which are available on the market. Of course the electrical and mechanical properties are not influenced negatively, however disadvantages in the reflectivity occur, which is important in the field of lighting technology. The yellowing-stable white-opaque photo-imageable solder resist Elpemer SD 2491 SM-TSW and the corresponding marking ink SD 2691 TSW however meet the requirements of the optoelectronics industry. They are applied by screen printing and developed in aqueous-alkaline media. The solder resist corresponds to the best flame class V-0 according to UL 94, meets requirements of IPC-SM-840D and is halogen-free according to JPCA-ES01–2003/IEC 61249–2–21.
Due to its high yellowing resistance, the white casting compound VU 4490/31 K based on polyurethane resin is particularly suitable for use in optoelectronics. Even when exposed to intense sunlight only very slight yellowing of the surface is to be expected which does not affect the protection in any way. The comparatively hard potting can be used to reliably protect high-quality and impact-sensitive electronic components, LED lights, illuminated keyboards and fittings and many more. The smooth white surface gives the potting a particularly high-grade finish. The potting compound is especially easy to process in mixing and dispensing equipment, but can be equally processed by hand despite the short pot life. Our customers appreciate the fast curing. After slight heating to 40 °C the potting can be easily removed from its mould after just 10 minutes.
SMT, booth 9–604
EPP Europe 439
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