LED process flow

First, LED production process

1, process:
A) cleaning: using ultrasonic cleaning PCB or LED bracket, and drying.
A: b) in LED tube core (wafer) bottom electrode prepared on silver colloid after expansion, will expand after the tube core (wafer) placed in the thorn crystal on the stage, will die a pad installed in the PCB or LED support corresponding with thorn crystal pen under the microscope then, the sintered silver glue curing.
C pressure welding: using aluminum wire or wire welding machine to connect the electrode to the LED core for the current injection of lead. LED directly installed on the PCB, the general use of aluminum wire welding machine. (white TOP-LED wire welder)
Package: D) by dispensing with epoxy, LED tube core and welding line protection. Glue on the PCB board, there are strict requirements on solidified colloid shape, which is directly related to the brightness of backlight source products. This process will also assume the task of fluorescent powder (white LED).
E welding: if the backlight is SMD-LED or other packaged LED, the assembly process, the need for LED welding to the PCB board.
F) cutting film: all kinds of diffusion film, reflective film and so on.
G assembly: according to the requirements of the drawings, the backlight source of various materials by hand to install the correct location.
H) test: check the back light source photoelectric parameters and light uniformity is good.
I) packaging: packaging and packaging of finished products as required.

Two, packaging technology
1, LED packaging tasks
The utility model is used for connecting the external lead wire to the electrode of the LED chip, and at the same time, the LED chip is protected, and the effect of improving the light extraction efficiency is improved. The key process for assembling, welding, packaging.
2, LED packaging form
LED package can be said to be a variety of forms, mainly based on different applications, the corresponding size of the shape, cooling measures and light effect. LED according to the classification of packaging has Lamp-LED, TOP-LED, Side-LED, SMD-LED, High-Power-LED, etc..
3, LED packaging process flow
Three: packaging process description
1, chip inspection
Microscopic examination: mechanical damage and pitting pit or material surface (lockhill)
Whether the chip size and electrode size meet the technical requirements; whether the electrode pattern is complete
2, expansion
Because the LED chip after dicing still closely arranged space is very small (about 0.1mm), is not conducive to the process of operation. We use the expansion of the chip on the chip to expand the film, is the LED chip spacing stretching to about 0.6mm. can also use manual expansion, but it is easy to cause chip drop waste and other undesirable problems.
3, dispensing
In the corresponding position of the LED bracket on the silver glue or insulation glue. (with the back electrode for GaAs, SiC conductive substrate, red light, yellow light, yellow green chip, using silver colloid. For the blue and green LED chips of the sapphire insulation substrate, the chip is fixed by the insulating glue The difficulty lies in the control of the dispensing process, in the process of colloidal height, dispensing position are detailed. Because of the strict requirements for the storage and use of the silver glue and the insulating rubber, the wake, mixing and using time of the silver glue are the matters needing attention in the process.
4, prepare glue
The preparation and dispensing glue is used instead, preparing the silver glue to glue machine on the back of the LED electrode, and then put back with silver colloid LED installed in the LED bracket. The preparation efficiency is much higher than the glue dispensing, but not all products are suitable for preparation of rubber technology.
5, hand thorn
After the expansion of the LED chip (glue or not prepared) is placed on the thorn table of the fixture, the LED bracket is placed under the fixture, under the microscope with the needle will be one of the LED chip to the corresponding location. Hand thorn has an advantage compared with the automatic racking, for different chips replaced at any time, suitable for the need to install a variety of chip products.
6, automatic mounting
In fact, the automatic rack is a combination of glue (dispensing and installing chip) two steps, the first in the LED bracket on the silver colloid (insulating glue), then use the vacuum suction nozzle LED chip suction location, and then placed in the bracket on the corresponding. Automatic rack in the process to be familiar with the main equipment operation and programming, to adjust the glue equipment and installation accuracy. In the selection of nozzle on selecting bakelite nozzle, to prevent damage to the surface of the LED chip, especially blue, green chips must use the bakelite. Because the nozzle will scratch the surface of the current diffusion layer.

7, sintering
The purpose of sintering is to solidify the silver glue, and to monitor the temperature of sintering, so as to prevent the bad batch. The sintering temperature of silver colloid is controlled at 150 DEG C, the sintering time is about 2 hours. According to the actual situation can be adjusted to 170 degrees, 1 hours. Insulation glue 150 DEG C, for 1 hours.
Silver glue sintering oven must be according to the requirements of the process for 2 hours (or 1 hours) to open the replacement of sintered products, the middle should not open. Sintering oven shall not be used for other purposes, to prevent pollution.

8, pressure welding
The purpose of the welding is to lead the electrode to the LED chip to complete the connection between the inside and outside of the product. LED pressure welding process has two kinds of wire ball welding and aluminum wire pressure welding. This is a process of aluminum wire bonding, the first LED chip electrode pressure on the first point, then the aluminum wire to stand above the corresponding pressure on the second points after the break, aluminum wire. Golden ball welding process in the first point before the first ball, the rest of the process is similar. Pressure welding is a key part of LED packaging technology, the main process is to monitor the welding wire (Lv Si) arch shape, the shape of solder joints, tension. Research on pressure welding process involves many aspects, such as gold (aluminum) wire material, ultrasonic power, welding pressure, capillary pressure (steel mouth) selection, capillary (steel mouth) trajectory and so on.

9, dispensing package
A dispensing, potting, molded three main LED package. Basically, the difficulty of process control is bubble, multi material, black spots. The design is mainly on the selection of materials, the choice of a good combination of epoxy and stent. (general LED not through the air tightness test) general TOP-LED and Side-LED for dispensing package. The manual dispensing package of high demands on the operation level (especially white LED), the main difficulty is to control the dispensing, because the epoxy during use will thicken. White LED also causes the dispensing color light precipitate fluorescent powder.

10, potting package
Lamp-LED package using the form of potting. The potting process is first injected in LED liquid epoxy molding cavity, and then insert the pressure LED stent welding, into the oven and make epoxy curing after LED from the mold cavity is formed.

11, molded packaging
The pressure LED stent welded into a mould, the upper and lower two sets of mould hydraulic clamping machine and vacuum, the solid epoxy glue injection into the entrance heating road with hydraulic push rod is pressed into the mould rubber road, along the road into the various LED epoxy adhesive curing and molding groove.

12, curing and post curing
Curing refers to the curing of epoxy, epoxy curing conditions at 135 DEG C, for 1 hours. Molded packaging generally at 150 degrees, 4 minutes.

13, after curing
After curing in order to allow epoxy curing, while the LED thermal aging. Post curing is very important to improve the bonding strength between epoxy and PCB. General conditions of 120 degrees, 4 hours.

14, cutting and dicing
Since the LED is connected in production (not a single), the Lamp package uses LED to cut off the tendons of the LED bracket. SMD-LED is on a PCB board, need dicing machine to complete the separation work.