The reliability of high-power light-emitting-diode (LED) devices strongly depends on the die-attach quality because voids may\nincrease junction temperature and total thermal resistance of LED devices. Die-attach material has a key role in the thermal\nmanagement of high-power LED package by providing low-contact thermal resistance. Thermal and mechanical analyses were\ncarried out by experiments and thermal simulation.The quantitative analysis results show that thermal resistance of die-attach layer\n(thermal resistance caused by die-attach material and voids in die-attach layer) plays an important role in total thermal resistance\nof high-power LED packaging according to the differential structure function of thermal transient characteristics. The increase of\nvoid fraction in die-attach layer causes the increases of thermal resistance of die-attach layer; the thermal resistance increased by\n1.95 K/Wwhen the void fraction increased to 62.45%.Thevoids also make an obvious influence on thermal stress and thermal strain\nof chip; the biggest thermal stress of chip was as high as 847.1MPa compared to the 565.2MPa when the void fraction increases\nfrom being void-free to 30% in the die-attach layer.
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