Influence of Die attach materials to optical and thermal performance of high power LEDs

In order to study the impact of die attach materials in HP LEDs, A 3-D model was established by TracePro and Ansys and two samples were fabricated with Silver epoxy and Insulation paste as the layer of die attach, respectively. The light output powers of sample1and sample2 were 295.1mW and 316.4mW at 350 mA, respectively. The light output power of sample2 using Insulation paste was 7% higher than that of sample1 with Silver epoxy at 350 mA. The light output power of sample2 declined quickly with the increase of current when the value of current was greater than 800mA. From cumulative structure function curves and differential structure function curves of sample 1 and sample 2, the total thermal resistances of sample1and sample2 were 16.7 K/W and 33.9 K/W, respectively, and the thermal resistances of the die attach layer in sample1and sample2 were 7.4 K/W and 22.9 K/W, respectively. The experiment results are well consistent with simulations by TracePro and Ansys. The result shows that LED package with Silver epoxy has better die attach quality than that of Insulation paste. However, the sample with Insulation paste has higher light output power.