Thermal　control　of　printed　circuit　board　and　integrated　circuit　package　is　challenging　in　microelectronics　because　the　power　density　increases　when　smaller　and　more　complicated　packages　are　designed.　Temperature　rising　due　to　power　dissipation　and　hotspots　worsens　harmful　clock　skew　and　jeopardizes　reliability　of　products.　To　overcome　these　risks,　designers　have　to　perform　electromagnetic-thermal　co-simulations　at　the　early　design　stage.　However,　it　is　difficult　to　detect　the　hotspots　in　the　package　because　very　high-resolution　simulations　are　needed.　In　this　paper,　an　improved　adaptive　finite　element　method　(FEM)　is　applied　to　detect　hotspots,　which　only　needs　one-step　adaptive　refinement　for　a　given　error　threshold,　which　is　very　fast　and　uses　much　smaller　computation　resources.　Furthermore,　instead　of　electromagnetic-thermal　co-simulation,　this　method　directly　finds　potential　hotspots　based　on　the　volumetric　heat　generation.　Test　results　show　that　the　adaptive　FEM　only　takes　about　60　times　the　memory　and　CPU　time　to　detect　all　hotspots　when　compared　to　the　initial　FEM　solution.