Research On High Light Efficiency And Reliability Of Ultraviolet Light-Emitting Diode Packaging And Its Application

Due to the mercury-free,low power consumption,compact structure,and controlled wavelength,ultraviolet light-emitting diode(UV-LED)has important applications in ink curing,illumination,sterilization,and biochemical detection.Currently,there are few researches on UV-LED packaging technology,and most UV-LEDs still use the packaging materials and structures of white LEDs.However,this packaging technology is difficult to satisfy the packaging requirements of UV-LED devices owing to the poor UV robustness of organic polymer materials.In order to achieve the UV-LEDs with high light efficiency and reliability,this dissertation started from the UV-LED packaging materials and structures and studied on the packaging technology for the light efficiency and reliability enhancement of UV-LEDs,and then this packaging technology was applied on the UV-excited white LED packaging.The main contents are described as follows:1)Packaging design of UV-LED devices:We proposed a whole inorganic packaging technology for UV-LEDs through material and structure optimization.The quartz glass cover was used as the optical lens and the three-dimensional ceramic substrate was used as the submount.The solder bonding between the glass cover and the ceramic substrate was used for the hermetic packaging.In addition,we selected the three-dimensional low temperature co-fired ceramic substrate containing a cavity and prepared the metallized patterning structure on the glass surface for the realizing of the solder bonding by three approaches,including lift-off,electroplating-etching,and metal sintering processes.2)High light efficiency of UV-LED packaging technology:In order to enhance the light efficiency of UV-LED devices,various methods were proposed to suppress the reflection losses at the glass and chip surfaces.For the Fresnel reflection at the glass surface,nanostructures were fabricated on the glass surfaces by the metal rapid annealing combined with etching process.The results show that the light power of deep UV-LEDs packaged by dual-side nanostructured glass is enhanced by 8.6%.For the total reflection loss at the chip surface,the fluoropolymer microlens arrays(MLAs)were fabricated on the chip surface by micromolding porous film templates,which were prepared by using initiative cooling based water condensing method.Consequently,the critical angle at the chip surface is improved by the MLA structure and the light power of deep UV-LED is enhanced by 15.4%.In addition,the AlN-doped fluoropolymer encapsulation layer was proposed for UV-LED packaging,which can reduce the refractive index difference between the encapsulant layer and the chips and improve the probability of light escaping from the packaging structure.The results indicate that the 0.15wt%AlN-doped fluoropolymer structure increases the light power of 16.4%.3)High reliability of UV-LED packaging technology:In order to improve the quality and reliability of UV-LED packaging,we proposed a localized induction heating packaging technology for UV-LEDs.The temperature field distribution of package model during induction heating process was analyzed.The results show that the bonding layer obtains the high temperature,which can avoid the bad effects of high temperature on the UV-LED chips.And the temperature of bonding layer increases with the increase of heating time and input frequency.Furthermore,the induction heating packaging system was designed and constructed.The UV-LEDs was packaged by using the localized heating bonding and the packaging structure achieves a tensile strength of 8.2 MPa and good air tightness.4)UV-LED excited phosphor-in-glass(RGB)for white LED packaging:In order to achive the white LEDs with high light quality and reliability,the proposed UV-LED packaging technology was applied to the UV-excited white LED packaging.The RGB PiGs were fabricated by screen-printing and low temperature sintering,the bonding between the PiG and the UV-LED was realized by the localized induction heating packaging technology,and the effects of phosphor content and phosphor layer thickness on the performances of white LEDs were investigated.When the phosphor layer thickness is 90?m and the concentration of red,green,and blue phosphors is 0.25 g/cm~3,0.6 g/cm~3,and 0.4 g/cm~3,respectively,the white LEDs achieve the warm white light with high quality.Furthermore,the multi-layered RGB PiGs were prepared to reduce the spectral overlaps between red,green,and blue spectra.The results demonstrate that the luminous efficacy of R-G-B and G-R-B multi-layered PiGs are increased by 8.2%and 17.6%,respectively.