With　the　increase　of　driving　current　and　power　density,　the　thermal　fatigue　characteristics　of　die　attach　materials　have　become　an　important　issue　impacting　the　long-term　reliability　of　high-brightness　light-emitting　diodes　(HB　LEDs).　In　this　paper,　an　accelerated　power　cycling　method　is　used　to　predict　the　thermal　fatigue　life　of　die　attach　materials　for　packaged　HB　LEDs.　The　thermal　fatigue　life　of　Au80Sn20　eutectic　and　silver　paste　is　investigated　at　driving　currents　of　650,　675,　and　700　mA.　Changes　in　the　thermal　resistance　of　die　attach　materials　are　monitored　by　the　noninvasive　structure　function　method　based　on　the　measurement　of　transient　temperature　response　curves　through　power　cycling　experiments.　Results　of　C-mode　scanning　acoustic　microscopy　and　cross-sectional　scanning　electron　microscopy　indicate　that　delamination　is　the　main　failure　mechanism　of　the　die　attach　materials　under　thermal　fatigue　stress.　Furthermore,　the　thermal　fatigue　life　of　die　attach　materials　can　be　derived　from　the　relationship　between　lifetime　and　temperature　difference　according　to　the　Coffin-Manson　relationship.　The　results　suggest　that　Au80Sn20　eutectic　possesses　a　longer　thermal　fatigue　life　than　silver　paste　at　the　same　temperature　difference　of　thermal　fatigue　stress.