At present, there are three ways to realize LED white light for illumination: synthesizing white light by using R, G, B three primary colors, exciting R, G, B phosphor by UVLED, and exciting yellow phosphor by blue LED chip . The most common way to make white light in the LED industry today is to mix a yellow phosphor with a certain wavelength band with epoxy or silica gel, and then encapsulate it around the blue LED chip. The blue light of the chip is mixed with the yellow light generated by the phosphor to form white. . However, the phosphor tends to settle during the gel solidification process, and the uneven distribution of the phosphor caused by the sedimentation has a great influence on the concentration of the white LED color region.
In the small and medium power white LED, it is more and more applied to lighting products because of its small size, low heat dissipation and high light extraction efficiency. However, because the amount of phosphor required for small and medium power single LED device package is small, the phosphor content and the distribution change in the colloid are more likely to affect the color coordinate distribution of the package sample, resulting in a low concentration of the color region of the LED product , forming a certain inventory. Pressure increases product costs. To this end, how to improve the color zone achievement rate of white LEDs has become an urgent problem for many packaging companies.
In this paper, the factors affecting the sedimentation of phosphors and the relationship between the sedimentation of phosphors and the color coordinate concentration of packaged samples will be studied in combination with the actual packaging production. In order to find a reasonable packaging process, the color concentration of white LED devices is improved by appropriately controlling the degree of phosphor deposition, and provides some theoretical guidance for actual production.
1, white LED device package
1.1 packaging materials
The main packaging materials used in this article are as follows:
Phosphor: YAG yellow phosphor with an average particle size of about 13μm and a density of 4.8g/cm3; glue: two-component A/B silicone resin with a viscosity of 3350cp at room temperature and a density of 1.2g after mixing A/B glue /cm3; LED bracket: SMD3528 bracket, the depth of the cup is 0.38mm; in terms of chip selection, the color coordinates of the white LED will be affected by the wavelength and brightness of the chip. Here, a blue chip with a relatively concentrated wavelength and brightness range is selected to avoid The chip parameters have an impact on the analysis of subsequent experimental results. The selected blue chip parameters: size 10×16 mil, the chip main wavelength range is 456.3～456.8nm, the average wavelength is 456.5nm, the brightness range is 22.1～22.4mW, and the average brightness is 22.2mW.
1.2 Packaging Equipment and Packaging Steps
1) Solid crystal: The Dutch ASM-AD830 solid crystal equipment is used to bond the LED chip in the LED bracket cup through the solid crystal insulating rubber, and heat curing.
2) Welding wire: The chip electrode and the bracket electrode are connected by wires using the Dutch ASM-iHawkXtreme automatic wire bonding machine.
3) Matching glue: Weigh 10 parts of glue and 1 part of phosphor respectively, and uniformly mix the phosphor and glue with a vacuum mixer of Japan THINKY-ARV310 and vacuum.
4) Dispensing: Use the Japanese Musashi SM3003-3A Dispenser to pour the configured glue into the dispensing syringe, adjust the dispensing parameters, and dispense the LED holder of the bonded wire.
5) Baking and curing: The sample after dispensing is placed in an oven with a set temperature for baking and curing.
Guangdong Decosun Lighting Technology Co.,Ltd , https://www.decosun-lighting.com