Enhancement of light-emitting diode reliability using silicone microsphere in encapsulant

The aim of this study was to prevent the delamination of encapsulant for light-emitting diode (LED) without sacrificing other optical performance. Silicone microsphere was employed to control the properties of shrinkage and hardness of encapsulant during curing process. The effects of microsphere in encapsulant were investigated by using the different concentration of microsphere. After curing reaction, the shrinkage percentage and hardness of both shore A and D encapsulants were reduced and reinforced, as increasing the concentration of microsphere. Despite the addition of microsphere, the LED packages fabricated without/with microsphere showed the similar initial optical efficiencies. It is because the light scattering effect compensated their small difference of refractive indexes between encapsulants and microsphere. Using the silicone microsphere, the improvement of reliability of LED packages could be achieved after 1000 h under condition of temperature (85 °C)/humidity (RH 85%). It is attributed to the synergy effects of shrinkage suppression and hardness improvement.