Design of anti-mildew smart microcapsules with chitosan as encapsulant for advanced electronic packaging epoxy coating

Moisture protection, anti-mildew and anti-corrosion are essential to guarantee the normal service of electronic devices. Although the epoxy holds great potential for electronic packaging, its inferior anti-corrosive performance and anti-mildew capability significantly affect the lifespan of the coating and thus impede further technological advances in electronic devices. To address this concern, herein, we fabricate environmental-friendly anti-mildew smart microcapsules (MCs) by encapsulating benzotriazole (BTA) loaded halloysite clay nanotubes (HNTs) with chitosan (CTS). The coating presents superior anti-mildew property with 5 wt% MCs addition. Furthermore, the charge transfer resistance (Rct) of T2 copper beneath the coating is three orders of magnitude larger after 35 days' immersion, which confirms a significantly promoted anti-corrosive performance for the coating. Moreover, mechanism study shows that such enhanced corrosion protective performance of proposed coating benefits from an excellent self-healing property enabled by a sustainable release of BTA with water and dual-pH sensitivity as well as effective adsorption of BTA on metal surface. It is further uncovered that the release rate of BTA is simultaneously determined by solubility of BTA, acid pH sensitivity of CTS and interaction between BTA and CTS. In addition, mechanical properties of coatings are enhanced with the tensile strength and elongation significantly increased, while the wet adhesion force (72 h) is also enlarged from 4.03 MPa to 7.22 MPa. Such a delicate design of environmental-friendly anti-mildew smart MCs not only enhances the corrosion protective property and the anti-mildew performance of the electronic packaging coatings, but also can facilitate the fabrication of other multifunctional organic coatings by utilizing multifunctional inhibitor or polyelectrolytes.