Electrical　tree　aging　problem　under　high-frequency　voltages　seriously　affects　the　reliability　of　packaging　insulation　for　power　electronics　modules.　In　this　article,　boron　nitride　(BN)　sheet/epoxy　resin　(ER)　composites　with　low　doping　concentration　are　prepared　and　characterized.　Varied　voltage　frequencies　(50　Hz-130　kHz)　are　selected,　and　electrical　tree　characteristics　of　composites　at　different　voltage　frequencies　are　studied.　Results　show　that　as　the　frequency　increases　from　50　Hz　to　130　kHz,　electrical　tree　initiation　voltage　of　pure　ER　decreases　by　39.8%.　However,　as　the　frequency　increases,　tree　channels　first　become　denser,　and　then,　the　tree　branches　decrease.　Moreover,　electrical　tree　shape　presents　sturdy　single-branch-like　tree　at　130　kHz.　By　introducing　BN　sheet,　the　tree　initiation　voltage　increases,　especially　at　higher　frequencies.　The　tree　scale　of　BN　sheet/ER　is　smaller　than　that　of　pure　ER　at　all　frequencies.　Combining　the　dielectric　properties　and　tree　results　of　different　materials,　the　influence　of　frequency　on　tree　characteristics　of　ER　is　discussed,　and　the　role　of　BN　sheet　in　the　bulk　is　revealed.　©　1994-2012　IEEE.