Thermal　management　for　package　assembly,　especially　for　high　power　packages,　is　very　important　to　the　reliability　and　quality　of　electrical　products.　In　this　paper,　a　finite　element　approach　is　proposed　to　investigate　the　thermal　performance　of　TO252-5L(B)　package　attached　on　printed　circuit　board(PCB)　with　different　layers　and　sizes,　which　is　further　related　to　reliability　issue　of　this　type　of　IC　package.　©　2012　IEEE.