Impact of Conformal Coating on Thinner Wirewound Inductors

This white paper addresses the impact of conformal coating material selection on the reliability of wirewound common mode choke (CMC) inductors, particularly those utilizing thinner wire (≤0.08 mm). It outlines the vulnerabilities of CMC inductors, which are essential for EMI suppression in modern electronics, and the protective role of conformal coatings against environmental factors. However, the paper details how certain coatings can induce mechanical stress due to differing thermal expansion properties, leading to wire breakage during thermal cycling. The research includes experimental results comparing various coating materials, emphasizing the importance of selecting coatings with appropriate mechanical properties to enhance reliability. Key considerations include the modulus of the coating, the coefficient of thermal expansion, and the thickness of the applied layer. The findings provide practical guidance for engineers to optimize product longevity and reduce failures, particularly in automotive applications where reliability is critical. The paper concludes with recommendations for coating selection to mitigate risks associated with thinner wire structures.