Application Of Nano-oxides In Pc-LEDs Packaging

Owing to their advantages of energy saving,environment-friendly,high brightness,fast response,and long life,Light-emitting diodes(LEDs)have been utilized in many fields,and have become the mainstream technology of solid-state lighting.Currently,most white LEDs on the market are realized by coating yellow phosphors on the surface of blue chip(pc-LEDs).For pc-LEDs,LED packaging technology plays a decisive role in the light quality of the light source.In view of this,this thesis has conducted related research on LED packaging substrate and phosphor coating technology,the main works are as follows:(1)Graphene oxide is proposed to be a thermally conductive filler to improve the thermal conductivity of the LED module and reduce the thermal resistance of the device.First,micron-scale graphene oxide was synthesized via the modified Hummers method,which was mixed with silicone grease thermal conductive adhesive and coated on a thermally conductive aluminum substrate for LED heat dissipation;when the proportion of filled graphene oxide is greater than 1%,it can effectively reduce the device thermal resistance and improve the thermal conductivity of the thermal conductive adhesive,and the larger graphene oxide particle is more conducive to thermal conduction ability.In addition,when graphene oxide with a concentration of 2 mg/mL is added to the PVA-ADC photoresist system,the thermal resistance of the device is reduced by 17%;However,because of the blue light absorption,the addition of graphene oxide reduces the luminous flux of the device by 9%,The average color temperature drops by 267 K.(2)In view of the difference in refractive index between the chip and the packaging matrix in pc-LEDs packaging,this thesis proposes to use nano-titanium dioxide(TiO2)as a silica gel filler to increase the refractive index of the packaging matrix,and improve the light extraction efficiency of the device.The results revealed that when the TiO2 filling ratio is 1%,the luminous flux of the device is increased by 9%.Furthermore,because of the precipitation of TiO2 and phosphor,the effect of curing temperature on the precipitation speed of particles and the influence of precipitation on the optical performance of LEDs were studied after the addition of TiO2.The experimental results show that the higher curing temperature has an obvious impact on the sedimentation inhibition effect of TiO2 and phosphor.When the temperature is greater than 90?,the time for the particles to reach complete precipitation is less than 10min;In addition,the LED device during the particle precipitation process,the luminous flux will increase first and then decrease,and it will also cause the average color temperature of the LED to reduce,but it has a certain improvement effect on the spatial color temperature uniformity.(3)A new optimized structure of phosphor coating is proposed.The structure is mainly divided into three parts,including silicone remote layer,phosphor dispensing layer,and adaptive exposure coating.This phosphor coating structure have the advantages of being far away from coating and self-adaptive,better spatial color temperature uniformity and luminous efficiency.The experimental results demonstrated that the spatial color temperature standard deviation of the self-adaptive phosphor coating is 201.1 K and the thermal resistance is 45.28 K/W;while the optimized phosphor color coating has a spatial color temperature standard deviation of 49.03 K and a thermal resistance of 42.17 K/W;the stable junction temperature of the adaptive phosphor coating at a working current of 350 mA is 83.30?,and the optimized device is 79.27?.In order to achieve high-quality lighting and improve the color rendering of the light source,CdSe/ZnS red quantum dot phosphor was evenly sprayed on the basis of the optimized coating,and the color rendering index Ra was increased to above 85,which improved the color rendering of the device.