Solvent-free high-performance insulating coatings from photocurable polyimide resin for electronic circuit boards

Polyimide (PI) materials have widespread applications as electronic insulation coatings, but their poor compatibility with photocurable monomers makes it challenging to prepare solvent-free photocurable PI coatings. This poor compatibility is caused by the high-density aromatic structure and strong intermolecular interactions within PI chains. To overcome this, maleimide resins with non-coplanar branched structures were designed and synthesized, and their structure-activity relationship was studied. The non-coplanar structure of the resin allowed it to be dissolved in photocurable monomers to prepare solvent-free photocurable PI coatings. This also reduced the carrier mobility in the coating, rendering it highly insulating. The results showed that as the maleimide content increased, the glass transition temperature (Tg) and volume resistivity of the coating both increased, reaching 208 °C and 6.3 × 1015 Ω·cm, respectively. Neutral salt spray tests showed that the insulation of the BDM-HTDA coating was one order of magnitude higher than that of the control coating, and no obvious copper corrosion was observed after 672 h. This indicates that the introduction of the BDM-HTDA resin significantly enhanced the barrier performance of the coatings. This excellent comprehensive performance gives it potential applications in electronic equipment used in complex service environments.