Issue link: https://iconnect007.uberflip.com/i/1540984
NOVEMBER 2025 I SMT007 MAGAZINE 69 of chemistries, including acrylics, silicones, poly- urethanes, alkyds, urethanes, and polyolefins, each offering distinct barrier performance advantages and trade-offs. While these formulations have reli- ably served the industry for decades, the increas- ing complexity of electronics and the expanding demands of modern applications are giving rise to new challenges. As a result, designers and man- ufacturers are turning to material suppliers for advanced conformal coating solutions that can address issues such as: • Electrochemical Migration (ECM) ECM is a well-documented failure mechanism in modern PCBs. It occurs when metal ions migrate between conductors under the com- bined influence of moisture, ionic contami- nation, and an electric field. This migration can result in the formation of conductive den- drites. If dendrites grow long enough, they can bridge adjacent traces and cause short circuits. Traditionally, ECM was not a major concern because circuit traces were spaced relatively far apart, meaning dendrites would have needed to grow much longer to create a failure. In contrast, today's miniaturized circuits feature much finer trace spacing. As a result, dendrites can span the gap and induce short circuits in only a matter of hours under favorable conditions. What are those conditions? The primary triggers are moisture and ionic contaminants, especially when flux residues are present. Conformal coatings are essential because they function as a protective barrier against moisture and contamination. Flux residues, however, require additional mitigation strategies, which we will explore in the next section. Solder Paste Compatibility Issues Flux residues from solder pastes, particularly those that contain halide activators like chlorine or bro- mine, can promote corrosion and degrade solder joints over time. This can be particularly problem- atic in humid environments. Additionally, flux resi- dues can interfere with the proper adhesion of con- formal coatings, making them unable to adequately seal PCBs from moisture and contamination. For these reasons, flux cleaning is often recom- mended to remove residues and enhance coating adhesion. An alternative is the use of no-clean sol- der pastes. While not completely flux-free, these formulations are less reactive and more stable in humid conditions. Their popularity comes from the fact that they typically do not require cleaning after reflow soldering, which simplifies manufacturing and increases throughput. However, it is important to note that certain no-clean solder pastes may still be incompatible with some protective coatings. To address this challenge, MacDermid Alpha develops solder pastes and conformal coatings designed specifically for compatibility. SIR test- ing is conducted on these material sets to validate performance. When reliability issues, such as cor- rosion or ECM occur, the root cause may be mate- rial incompatibility. ▼ D e n d r i te g row t h d u e to EC M . ▼ C o r ro s i o n d u e to f l u x re s i d u e s . ▼ D e n d r i te g row t h d u e to EC M .