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OCTOBER 2025 I DESIGN007 MAGAZINE 59 certain environments. In addition, silicones exhibit poor adhesion, a drawback for some applications but an advantage when easy removal is desired for end-of-life recycling. • Polyurethane-based potting compounds: Polyurethane-based potting materials offer an excellent balance of flexibility and tough- ness. They are soft enough to absorb ther- mal expansion and contraction from CTE mismatch without warping circuit boards or cracking fragile component leads, yet tough enough to provide mechanical support that protects encapsulated electronics from impact, shock, and vibration. Polyurethanes perform well at temperatures up to 125°C and offer excellent resistance to moisture and many chemicals. Their ability to maintain a tight, durable seal against water and water vapor makes them a preferred choice for moist, humid, or submerged applications. They also adhere well to metals, plastics, and ceramics, ensuring secure encapsulation and long-term protection of sensitive electronics. The table below summarizes the characteristics of epoxy-, silicone-, and polyurethane-based potting materials. While each material class has hundreds of different formulations tailored to meet unique appli- cation requirements, these comparisons provide a useful overview of their typical performance traits. RF-friendly Potting Solutions An increasing number of electronic devices, par- ticularly wireless sensor applications, require RF- transparent materials that allow signals to pass through easily. RF communication is fundamental to interconnected systems, enabling wireless data transmission for a vast range of Internet of Things (IoT) applications. Examples include monitoring and controlling traffic, monitoring water quality and consumption, and enhancing the safety and effi- ciency of automobiles and industrial equipment. In today's digital age, seamless RF data exchange has become essential. While silicone-based materials are, by nature, RF transparent, epoxies and polyurethanes can be engineered to achieve comparable performance. By formulating these materials to maintain a low dielectric loss and a dielectric constant below 3.5, RF signals pass through with minimal signal absorp- tion, attenuation, reflection, or delay. To meet the growing demand for RF-compati- ble encapsulants, chemists at MacDermid Alpha Electronics Solutions have developed new pot- ting materials designed for RF transmitter devices. One such solution, the Electrolube UR5118 polyure- thane-based compound, has a low dielectric con- stant of 3.1 to preserve RF signal integrity while pro- viding robust protection against moisture, chemi- cals, and mechanical stress. C o m p a r i s o n of Pot t i n g M ate r i a l s Properties Epoxies Silicones Polyurethanes Ad h e s i o n E xc e l l e nt Po o r Ve r y g o o d ( m et a l s , p l a st i c s , c e ra m i c s) F l ex i b i l i t y Low ( r i g i d ) H i g h (s of t ) M o d e rate M e c h a n i c a l S t re n g t h H i g h Low M o d e rate M o i st u re Re s i st a n c e Ve r y G o o d M o d e rate ( p e r m e a b l e to va p o r) Tu n a b l e Te m p e rat u re R a n g e -40 to 1 8 0 ° C - 6 0 to 2 0 0 ° C 6 0 ° to 1 2 5 ° C C h e m i c a l Re s i st a n c e E xc e l l e nt M o d e rate (c a n swe l l i n o i l s) E xc e l l e nt R F C o m p at i b i l i t y ( l ow d i e l e ct r i c c o n st a nt ) Tu n a b l e Tu n a b l e Tu n a b l e Rewo r ka b i l i t y (e n d - of- l i fe re cyc l a b i l i t y ) Po o r M o d e rate (g e l s a re re m ova b l e) Po o r