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Abstract Better electrical insulation and thermal management are both urgently required in integrated power semiconductors. Electrical insulation epoxy encapsulation suffers from poor heat conduction, which has increasingly become a bottleneck of power semiconductors integration. Although incorporating high thermal conductivity ceramics, such as hexagonal boron nitride (hBN), aluminium nitride etc. into epoxy promotes the thermal conductivity, the eco‐friendly scalable fabrication of these composites with sufficient electrical breakdown strength remains a formidable challenge. Suitable voltage stabilizers are known to provide additional benefits to breakdown strength. Herein, a high‐throughput approach combining plasma with roll‐to‐roll was developed. The voltage stabilizer (acetophenone) was grafted on interfaces between hBN and epoxy matrix through plasma. The high‐energy electrons are consumed by the grafted interface, which leads to the significant suppression of partial discharge in Epoxy/hBN. Meanwhile, interfacial phonon scattering is repaired by grafting. Therefore, the epoxy composite concurrently exhibits improved breakdown strength (by 27.4%) and thermal conductivity (by 142.9%) at about 11.9 wt.% filler content, outperforming the pure epoxy. Consequently, a promising modification strategy for mass production is provided for the encapsulation materials in various high‐power‐density semiconductor devices.