led display

. LED display technology:












a) Cleaning: ultrasonic cleaning PCB or LED support, and drying.






b) LED display cage: the LED die (wafer) on the bottom electrode silver paste prepared after the expansion, the expansion of the die after the (wafer) placed in the thorn crystal table, under a microscope with a thorn in the crystal pen will die one by one installed in the PCB or the LED corresponding pad on the support, followed by sintering the silver adhesive curing.






c) LED display pressure welding: welding with aluminum wire or gold wire electrodes connected to the LED die on the lead for current injection. LED mounted directly on the PCB, the general use of aluminum wire welding. (TOP-LED need to make white gold wire welder)






d) LED display package: by dispensing with epoxy to protect the LED die and wire up. Dispensing in the PCB board, the shape of the cured gel, there are strict requirements, which is directly related to the backlight brightness of the finished product. This process will also assume the point of phosphor (white LED) task.






e) LED display Welding: If the backlight is the use of SMD-LED, or other encapsulated LED, in the assembly process, you need to LED soldered to the PCB board.






f) LED display cutting film: punch die with all the necessary backlight diffusion film, reflective film.






g) LED display assembly: According to the drawings, a variety of materials to backlight manually install the correct location.






h) LED display test: Check out the backlight optical parameters and light uniformity is good.






LED display Packing: The finished product required packaging, warehousing.






Chapter II LED display packaging process






1.LED task package






Is the outer lead electrode connected to the LED chip, simultaneously protecting the LED chip, and play a role in improving the light extraction efficiency. Key process have mounted, pressure welding, package.






2.LED package






LED package can be said to be varied, mainly according to different applications using the corresponding form factor, thermal response and the light effects. Classification according to package LED Lamp-LED, TOP-LED, Side-LED, SMD-LED, High-Power-LED and so on.






3.LED packaging process






4. Packaging technology that






1. Chip testing






Examination: Are there surface pitting of mechanical damage and Ma Hang (lockhill)






Chip size and whether the size of the electrode process requirements






Electrode pattern is complete






2. Expansion pieces






Dicing the LED chips arranged in close distance and still very small (about 0.1mm), is not conducive to the process after the operation. We use expansion chip bonding machine of membrane expansion, is stretching the distance between LED chips to about 0.6mm. Expansion can also be used manually, but it is likely to cause problems and other undesirable waste chips fall.






3. Dispensing






Corresponding position in the LED bracket point silver plastic or rubber insulation.






(For GaAs, SiC conductive substrate, the back electrode has red, yellow, yellow, and green chips, with silver plastic. Insulating sapphire substrates for blue, green LED chips, the use of insulating rubber to secure the chip.)






Dispensing process difficulty is the amount of control, the gel height, dispensing locations are detailed process requirements.






Silver glue and glue the insulation in the storage and use are strict requirements, silver plastic wake up materials, mixing, time of use are processes must pay attention to.






4. Preparation of adhesive






And dispensing the contrary, the prepared gel is first prepared by glue applied to the LED on the back silver electrode gel, and then glue the back with silver LED installed in the LED bracket. Preparation of adhesive dispensing efficiency is much higher than, but not all products are prepared for plastic process.






5. Hand thorn pieces






After the expansion of LED chip (prepared or not prepared adhesive plastic) placed in the fixture thorn film sets, LED fixture on the bottom bracket, under the microscope with a pin to an LED chip, a thorn to the appropriate location. Gill plate and auto-manual than cage has the advantage of easy replacement of different chips at any time, for a variety of chip products need to be installed.






6.LED automatic pallet display






Automatic pallet is a combination of glue stick (glue) and the installation of the chip are two steps, first point in the LED bracket silver plastic (plastic insulation), and then use the vacuum nozzle to suck from the LED chip mobile location, and then placed in corresponding bracket position.






Automatically installed on the main frame in process equipment operation should be familiar with programming, while the equipment and installation of precision plastic stick to adjust. As far as possible the selection of the nozzle used bakelite nozzle to prevent surface damage to the LED chips, in particular, blue, green, chip to be used bakelite for. Because steel tips can scratch the surface of the current diffusion layer chip.






7.LED display sintering






The purpose is to make sintered silver plastic curing, sintering temperature required to monitor and prevent lots of bad.






Silver paste sintering temperature is generally controlled at 150 ℃, sintering time 2 hours. Can be adjusted according to actual conditions to 170 ℃, 1 hour.






Insulating adhesive generally 150 ℃, 1 hour.






Silver paste sintering oven process requirements must be separated by 2 hours (or 1 hour) to open replace sintered products, in the middle are not free to open. Sintering oven for other purposes shall not prevent pollution.






8.LED display bonding






The purpose of bonding the electrode lead to the LED chip, the finished product lead connections inside and outside work.






LED pressure welding process for welding a gold ball and aluminum wire bonding two. Right is the aluminum wire bonding process, the first electrode in the LED chip, the first pressure point, then the aluminum strands to the corresponding bracket above the pressure point on the second aluminum wire snapped. Gold ball bonding process is the first point in the pressure before firing a ball, like the rest of the process.






Bonding is a LED packaging technology in the key link in the main process is the need to monitor the bonding gold (aluminum wire) wire arch shape, solder joint shape, tension.






Welding of pressure-depth study of various issues involved, such as gold (aluminum) wire materials, ultrasonic power, bonding stress, wedges (wedge) selection, wedges (wedge) trajectory and so forth.






9. Dispensing package






LED package main some glue, potting, molding of three.






Basically, the difficulty is the bubble process control, multi-material shortage, black spots. Designed mainly for material selection, combined with a good selection of epoxy and bracket. (General LED can not leak test), TOP-LED and Side-LED for dispensing package. Manual dispensing package of the operational level requires a very high (especially white LED), the main difficulty is to dispense the amount of control, because the epoxy will thicken during use. Dispensing white LED phosphor precipitation there a light chromatic aberration caused the problem.






10. Filling plastic package






Lamp-LED package in the form of using potting. Casting process is the first in the LED into the liquid epoxy molding cavity, and then insert a good LED bracket bonding, into the oven for curing, the LED will emerge from the cavity is formed.






11. Molded package






The bonding in a good LED bracket into the mold, the bottom two mold clamping hydraulic machines and vacuum, the solid epoxy glue injection into the entrance road onto the heated mold with a hydraulic plunger runner, epoxy Shun the runner into the slot of each LED molding and curing.






12. Curing and after curing






Curing is the curing of epoxy encapsulation, generally epoxy curing conditions 135 ℃, 1 hour. Molded package is usually in 150 ℃, 4 minutes.






13. After the curing






After the curing is to allow full curing of epoxy, while LED thermal aging. Post-curing epoxy and support for improving the (PCB) of the adhesive strength is very important. General conditions of 120 ℃, 4 hours.






14. Cut the tendons and dicing






The LED in production are linked (not single), Lamp LED package with cut tendons cut stent with LED bars. SMD-LED is in a PCB board, you need to complete the separation of Dicing work.






15. Test






LED photoelectric parameters of the test, inspection dimensions, while LED products based on customer requirements for sorting.






16. Packaging






Count the finished product packaging. Super bright LED need anti-static packaging.