The　thermal　fatigue　delamination　interface　of　die　attach　materials　in　high-brightness　light-emitting　diodes　(HB　LEDs)　is　determined　using　a　noninvasive　approach.　Failure　analysis　of　HB　LEDs　containing　Au80Sn20　eutectic　alloy　and　silver　paste　as　die　attach　materials　is　performed　by　monitoring　the　changes　in　the　partial　thermal　resistances　in　differential　structure　function　curves　of　the　HB　LEDs　through　power　cycling　experiments.　The　results　suggest　that　delamination　of　the　Au80Sn20　eutectic　and　silver　paste　materials　occurs　at　the　chip-to-die　attach　interface　and　die　attach-to-heat　sink　interface,　respectively,　which　is　consistent　with　cross-sectional　scanning　electron　microscope　analysis.