The development of OLED materials is the basis for the vigorous development of the OLED industry. The earliest OLED light-emitting materials are fluorescent materials, but the upper limit of the theoretical quantum efficiency of fluorescent materials can only reach 25% due to spin inhibition. In 1998, Ma and Forrest and Thompson successively reported the application of phosphorescent materials in OLED materials, which paved the way for breaking the law of spin statistics and utilizing 100% of the energy of all excitons. However, phosphorescent materials also have certain problems. Due to the inclusion of precious metals, the price is high and the stability of blue light materials has been stagnant for a long time.
In 2009, Professor Adachi from Kyushu University in Japan introduced thermally Silicon Nitride Ceramics activated delayed fluorescence (TADF) materials into OLEDs for the first time. Such materials have extremely low singlet triplet energy gaps and can achieve 100% intra-theoretical quantum efficiency through inverse intersystem crossing (RISC) of triplet excitons. With the improvement of material system and device structure, OLED has emerged in the display field. On the other hand, WOLED has a series of advantages such as high luminous efficiency, adjustable spectrum, less blue light components and surface light source. As a high-efficiency light source with low color temperature and no blue pollution, it is expected to become a new trend of healthy lighting in the future. The five major raw materials of LED are: chip, bracket, silver glue, gold wire, epoxy resin
The composition of the wafer: it is composed of gold pad, P pole, N pole, PN junction, and back gold layer (double pad wafer has no back gold layer). The wafer is a PN combination composed of P-layer semiconductor elements and N-layer semiconductor elements rearranged and combined by electron movement. It is this change that enables the wafer to be in a relatively stable state. When a certain voltage is applied to the Silicon Nitride Ceramics forward electrode of the wafer, the holes in the positive P region will continuously swim to the N region, and the electrons in the N region will move to the P region relative to the holes. When the electrons and holes move relative to each other, the electrons and holes pair with each other to excite photons and generate light energy. Main classification, surface-emitting type: Most of the light is emitted from the surface of the wafer. Five-sided luminous type: There are more light emitting from the surface and sides according to the luminous color, red, orange, yellow, yellow-green, pure green, standard green, blue-green, blue. The structure of the bracket is 1 layer of iron, 2 layers of copper plating (good conductivity, fast heat dissipation), 3 layers of nickel plating (anti-oxidation), 4 layers of silver plating (good reflection, easy to wire) silver glue (due to many types , we take H20E as an example) also called white glue, milky white, conductive adhesion (baking temperature: 100°C/1.5H) silver powder (conductivity, heat dissipation, fixed chip) + epoxy resin (cured silver powder) + Thinner (easy to stir). Storage conditions: Silver glue manufacturers generally store silver glue at -40 °C, and application units generally store silver glue at -5 °C. Single agent is 25 °C/1 year (dry and ventilated place), mixed agent is 25 °C/72 hours (but due to other factors "temperature, humidity and ventilation conditions" during online operation, in order to ensure the quality of the product is average The mixture use time is 4 hours) Baking conditions: 150 °C/1.5H
Stirring conditions: uniformly stir the gold wire in one direction for 15 minutes (take φ1.0mil as an example) The gold wire used for LEDs is φ1.0mil, φ1.2mil, the material of the gold wire, and the material of the gold wire for LED generally has a gold content of 99.9 %, the use of gold wire makes Silicon Nitride Ceramics use of its high gold content, soft material, easy deformation, good conductivity and good heat dissipation, so that a closed circuit is formed between the chip and the support. (Conversion relationship: 1 mil = 0.0254mm , 1 in = 25.4mm )
Epoxy resin (taking EP400 as an example) consists of: A and B two components: A glue: the main agent, consisting of epoxy resin + defoamer + heat-resistant agent + diluent B agent: curing agent, composed of acid Intoxication + release agent + accelerator Conditions of use: Mixing ratio: A/B=100/100 (weight ratio)
Mixing viscosity: 500-700CPS/30 °C
Gel time: 120 °C*12 minutes or 110 °C*18 minutes
Usable conditions: about 6 hours at room temperature 25 °C. Generally, according to the production needs of the production line, we set its use condition as 2 hours.
Hardening conditions: initial hardening 110 °C-140 °C 25-40 minutes
Post-hardening 100 °C*6-10 hours (mobility adjustment can be made according to actual needs)
What is the difference between imported and domestic industrial ceramics?
2022 05/06