1, chip inspection: microscopic inspection: whether there is mechanical damage and locking); On the surface of the material; Whether the chip size and electrode size meet the process requirements; Is the electrode pattern complete? 2. Spreading: Because the LED chips are still closely arranged after dicing, the spacing is very small (about 0. 1mm), which is not conducive to the subsequent process operation. We use a stretching machine to expand the film attached to the chip, that is, we can stretch the distance between LED chips to about 0.6mm, or we can use manual expansion, but it is easy to cause bad problems such as chip falling and waste. 3. Glue dispensing: Apply silver glue or insulating glue to the corresponding position of the LED bracket. (For GaAs and SiC conductive substrates, red, yellow and yellow-green chips with back electrodes are made of silver paste. For blue and green LED chips with sapphire insulating substrate, insulating glue is used to fix the chips. ) The technical difficulty lies in the control of dispensing amount, and the height and position of colloid have detailed technical requirements. Because there are strict requirements for the storage and use of silver glue and insulating glue, the proofing, mixing and using time of silver glue are all matters that must be paid attention to in the process. 4. Glue making: Contrary to glue dispensing, glue making is to apply silver glue to the electrode on the back of the LED with a glue making machine, and then install the LED with silver glue on the back on the LED bracket. The efficiency of dispensing is much higher than that of dispensing, but not all products are suitable for dispensing. 5. Manual die bonding: put the expanded LED chips (with or without glue) on the fixture of the die bonding table, put the LED bracket under the fixture, and nail the LED chips to the corresponding positions one by one under the microscope. Compared with automatic mounting, manual punching has an advantage that it is convenient to replace different chips at any time, which is suitable for products that need to install multiple chips. 6. Automatic mounting: Actually, automatic mounting is a combination of gluing (gluing) and pasting. First, apply silver glue (insulating glue) on the LED bracket, then suck the LED chip to the moving position with a suction nozzle, and then put it on the corresponding bracket position. In the process of automatic mounting, it is mainly necessary to be familiar with equipment operation programming, and at the same time to adjust the bonding and installation accuracy of equipment. In the selection of suction nozzle, try to use bakelite suction nozzle to prevent damage to the surface of LED chip, especially blue-green chip. Because the steel nozzle will scratch the current diffusion layer on the chip surface. 7. Sintering: The purpose of sintering is to cure the silver glue, and the sintering needs to monitor the temperature to prevent batch defects. The sintering temperature of silver paste is generally controlled at 65438 050℃ and the sintering time is 2 hours. It can be adjusted to 170℃ and 1 hour according to the actual situation. Insulation glue is generally 150℃ 1 hour. The silver glue sintering furnace must be opened every 2 hours (or 1 hour) according to the process requirements to replace the sintered products, and it is not allowed to be opened at will. Sintering furnace shall not be used for other purposes to prevent pollution. 8. Bonding: The purpose of bonding is to lead the electrode to the LED chip and complete the connection of the internal and external leads of the product. There are two bonding processes for LED: gold wire ball bonding and aluminum wire bonding. The picture on the right shows the bonding process of aluminum wire. First press the first point on the electrode of the LED chip, then pull the aluminum wire above the corresponding bracket, and then press the second point to pull the aluminum wire down. The gold wire ball welding process is to burn a ball first and then press the first point, and other processes are similar. Bonding is a key link in LED packaging technology, and the main processes to be monitored are the shape of gold wire (aluminum wire), the shape and tension of solder joint. The in-depth study of pressure welding technology involves many problems, such as gold (aluminum) wire material, ultrasonic power, pressure of pressure welding, selection of cleaver (steel nozzle), motion trajectory of cleaver (steel nozzle) and so on. 9. Dispensing and packaging: LED packaging mainly includes dispensing, potting and molding. Basically, the difficulties in process control are bubbles, lack of materials and black spots. The design is mainly about the selection of materials and the good combination of epoxy resin and bracket. Generally speaking, top LED and side LED are suitable for dispensing package. Manual dispensing packaging requires a high level of operation (especially white LED), and the main difficulty is to control the amount of dispensing, because epoxy will thicken during use. The dispensing of white LED still has the problem of color difference caused by phosphor precipitation. 10, potting and packaging: LED lamps are potting and packaging. The process of potting is to inject liquid epoxy resin into the mold cavity of LED molding, then insert the pressure welded LED bracket, put it in the oven to cure the epoxy resin, and then take the LED out of the mold cavity for molding. 1 1. molding and packaging: put the pressure-welded LED bracket into the mold, close the upper and lower molds with a hydraulic press and vacuum, put the solid epoxy resin into the rubber channel of the mold with a hydraulic ejector pin, heat it at the entrance of the rubber channel, and the epoxy resin enters each LED molding groove along the rubber channel for curing. 12. Curing and post-curing: Curing refers to the curing of encapsulated epoxy resin. Generally, the curing conditions of epoxy are 135℃ and 1 hour. Molding and packaging are usually carried out at 150℃ for 4 minutes. 13. Post-curing: Post-curing refers to completely curing epoxy resin and thermally aging LED. Post-curing is very important to improve the bonding strength between epoxy resin and PCB. The general situation is 120℃ for 4 hours. 14. Rib cutting and slicing: As the LEDs are connected together (not single) in production, the LEDs in the lamp package are cut by rib cutting to cut off the connecting ribs of the LED bracket. SMD-LED is on PCB and needs dicing machine to complete the separation. 15. test: test the photoelectric parameters of LED, check the overall dimensions, and classify LED products according to customer requirements. 16. packaging: counting and packaging the finished products. Ultra-bright LED needs anti-static packaging