This study proposes a precise treatment method employing atmospheric pressure micro-plasma jet(μ-APPJ) to address the issue of insulation properties degradation induced by electric field concentration at triple point in package insulation

achieving localized electric field optimization by interfacial modification

thus enhancing the insulation reliability of package structure. This paper establishes an Ar/ Hexamethyldisiloxane(HMDSO) plasma treatment to investigate the effects of HMDSO volume fraction(ϕH) on the μ-APPJ discharge characteristics

and its influence on partial discharge(PD) and breakdown voltage of package insulation. The plasma treatment mechanism at triple point in suppressing local electric field concentration is explored by combining physicochemical properties of material surface with plasma ionization process. The results show that the μ-APPJ treatment system generates a stable plasma plume with a diameter of 200 μm

and the Ar* excited state particles effectively fragment the HMDSO molecules

facilitating precise deposition of Si-containing film at triple point

which achieves the modification of metal/insulation interface for insulation properties regulation. The optimized insulation properties are achieved with ϕH=0.13%

which significantly suppresses the PD intensity of package insulation(<20 pC)

and enhancing the breakdown voltage by up to 50.8%. The Ar/HMDSO μ-APPJ treatment precisely constructs a micron-scale spherical-cluster Si-containing film at the triple point

which modifies the microstructure of metal/insulation interface

optimizing the dielectric constant distribution and charge transport properties

ultimately enabling electric field regulation for enhancing the insulation performance of the package insulation.