Light-emitting diode device manufacturing process:
1: After injecting a certain current, the electrons and holes constantly flow through the PN junction or similar structural surfaces, and spontaneous composite diode semiconductor devices to produce radiated light. Applied disciplines: surveying and mapping (first class discipline); surveying and mapping instrumentation (second class discipline) definition 2: in the semiconductor p-n junction or its similar structure on the forward current, can emit visible or non-visible radiation semiconductor light-emitting device. Applied disciplines: mechanical engineering (first level); instrumentation components (second level); display devices (third level) LED manufacturing process from the expansion to packaging
1.LED chip inspection
Mirror inspection: the material surface whether there is mechanical damage and pockmarks pockmarks (lockhill chip size and electrode size in line with the requirements of the process electrode pattern is complete)
2. LED Expansion
As the LED chip is still closely arranged after slicing, the spacing is very small (about 0.1mm), which is not conducive to the operation of the post-process. We use the expansion machine to expand the film on the bonded chip, is the LED chip spacing stretched to about 0.6mm. can also be used manually expand, but it is easy to cause the chip to fall off and waste and other bad problems.
3. LED dispensing
In the corresponding position of the LED bracket dotted with silver or insulating glue. (For GaAs, SiC conductive substrate, with the back electrode of the red, yellow, yellow-green chip, using silver glue. For sapphire insulating substrate blue, green LED chips, the use of insulating adhesive to fix the chip).
The difficulty of the process is the control of the amount of dispensing, in the height of the gel, dispensing position are detailed process requirements.
Because of the silver and insulating adhesive in the storage and use of strict requirements, the silver adhesive of the wake up, mixing, use of time is the process must pay attention to matters.
4. LED adhesive preparation
And dispensing the opposite, adhesive preparation is to use the adhesive preparation machine to apply the silver adhesive on the electrode on the back of the LED, and then the back of the LED with the silver adhesive mounted on the LED bracket. The efficiency of adhesive preparation is much higher than dispensing, but not all products are suitable for adhesive preparation process.
5. LED hand-pricked
Expansion of the LED chip (ready or not ready for glue) placed in the pricking table on the fixture, the LED bracket on the fixture under the needle under the microscope will be one by one LED chip pricked to the corresponding position. Manual felting and automatic mounting compared to the rack has the advantage of facilitating the replacement of different chips at any time, suitable for the need to install a variety of chip products.
6. LED automatic mounting
Automatic mounting is actually a combination of dip glue (dispensing) and the installation of the chip in two major steps, the first in the LED bracket on the point of silver glue (insulating adhesive), and then use the vacuum nozzle will be sucked up to move the position of the LED chip, and then placed in the corresponding bracket position. Automatic mounting in the process mainly to be familiar with the equipment operation programming, while the equipment of the glue and the installation of precision adjustments. In the selection of suction nozzle as far as possible on the selection of wood suction nozzle, to prevent damage to the surface of the LED chip, especially blue, green chips must be used in wood. Because the steel mouth will scratch the chip surface of the current diffusion layer.
7. LED sintering
The purpose of sintering is to make the silver gel curing, sintering requirements for temperature monitoring to prevent batch bad. Silver sintering temperature is generally controlled at 150 ℃, sintering time of 2 hours. According to the actual situation can be adjusted to 170 ℃, 1 hour. Insulation glue general 150 ℃, 1 hour.
Silver sintering oven must be required by the process every 2 hours (or 1 hour) to open the replacement of sintered products, the middle shall not be opened at will. Sintering oven shall not be used for other purposes to prevent pollution.
8. LED pressure welding
Pressure welding of the purpose of the electrode will lead to the LED chip, complete the product inside and outside the lead connection.
LED pressure welding process has a gold wire ball welding and aluminum wire pressure welding two kinds. The right figure is the aluminum wire pressure welding process, first in the LED chip electrode pressure on the first point, and then pull the aluminum wire to the corresponding bracket above the pressure on the second point after tearing off the aluminum wire. Gold wire ball welding process in the pressure of the first point before burning a ball, the rest of the process is similar.
Pressure welding is a key link in the LED packaging technology, the process needs to be monitored is the pressure welding wire (aluminum wire) arch wire shape, weld shape, tension.
9. LED sealing
LED encapsulation is mainly point glue, potting, molding three. Basically, the process control is difficult to control the bubble, more lack of material, black spot. Design is mainly on the selection of materials, the choice of a good combination of epoxy and bracket. (General LED can not pass the airtightness test)
9.1 LED dispensing:
TOP-LED and Side-LED applicable dispensing package. Manual dispensing package requires high level of operation (especially white LED), the main difficulty is the control of the amount of dispensing, because the epoxy will thicken in the process of use. White LED dispensing also exists phosphor precipitation leads to the problem of color difference.
9.2 LED potting package
Lamp-LED encapsulation using the form of potting. The process of encapsulation is the first in the LED molding cavity into the liquid epoxy, and then inserted into the pressure welded LED bracket, put into the oven to let the epoxy curing, the LED from the mold cavity out of the molding.
9.3 LED molding encapsulation
Press welded LED bracket into the mold, the upper and lower two pairs of molds with a hydraulic press and vacuum, solid epoxy into the injection channel of the entrance to heat with a hydraulic lever pressed into the mold channel, epoxy along the channel into the molding of each LED groove and curing.
10.LED curing and post-curing
Curing refers to the curing of epoxy encapsulation, general epoxy curing conditions at 135 ℃, 1 hour. Molded package is generally at 150 ℃, 4 minutes. Post-curing is to allow the epoxy fully cured, while the LED thermal aging. Post-curing is very important to improve the epoxy and support (PCB) bonding strength. Typical conditions are 120°C for 4 hours.
11. LED cutting and scribing
Because the LED in the production is linked together (not single), Lamp package LED cut off the LED bracket by cutting the tendon. SMD-LED is on a PCB board, need to be scribed to complete the separation work.
12.LED test
The test LED photoelectric parameters, inspection of the external dimensions, and at the same time, according to customer requirements on the LED product sorting.
13.LED packaging
The finished product will be counted and packed. Super bright LEDs need anti-static packaging.