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Twelve steps of making LED chip"

时间:2017-04-06 10:43:10    来源:

Upstream chip technology has always been the bottleneck of the domestic LED, and most of the core technologies are mastered abroad. Here is a brief introduction to the process of chip fabrication:
1.LED chip test
Microscopic examination: material surface is a mechanical damage and pitting pits lockhill chip size and electrode size, electrode pattern should comply with process requirements is complete.
2.LED expansion
As the LED chip is still closely spaced after dicing, the spacing is very small (about 0.1mm), which is not conducive to the operation of the subsequent process. The film of the bonding chip is expanded by an expansion machine, so that the pitch of the LED chip is stretched to about 0.6mm. Manual expansion can also be used, but it is easy to cause chip waste, waste and other undesirable problems.
3.LED dispensing
Place the silver glue or insulating glue at the corresponding position of the LED bracket. For GaAs and SiC conductive substrates, red, yellow, yellow green chips with back electrodes were used with silver paste. For sapphire blue and green LED chips with sapphire insulation substrate, insulating adhesive is used to fix the chip.
The technical difficulty lies in the dispensing quantity control, in the colloid height, the dispensing position has the detailed craft request. Because of the strict requirements for the storage and use of silver glue and insulation glue, the awakening, mixing and using time of silver glue are the matters that must be paid attention to in the process.
4.LED glue preparation
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 efficiency of preparation is much higher than that of dispensing, but not all products are suitable for sizing process.
5.LED hand stab
The expansion LED chip (glue or no glue) is placed on the gripper of the thorn table, and the LED bracket is placed under the clamp, and the LED chip is stabbed one by one at the corresponding position with the needle under the microscope. 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.LED 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 steel nozzle scratches the surface of the chip, the current diffused layer.
7.LED sintering
The purpose of sintering is to solidify the silver gel and to monitor the temperature so as to prevent batch failure. The sintering temperature of silver paste is generally controlled at 150 DEG C and the sintering time is 2 hours. According to the actual situation, can be adjusted to 170 degrees, 1 hours. Insulation rubber generally 150 degrees, 1 hours.
Silver glue sintering oven must be opened every 2 hours (or 1 hours) according to process requirements, replace sintering products, the middle may not open at will. The sintering oven shall not be used for other purposes to prevent pollution.
8.LED pressure welding
The purpose of press welding is to lead the electrode onto the LED chip to finish the connection of the inner and outer lead.
LED's welding process consists of two kinds of gold wire welding and aluminum wire welding. The process of aluminum wire bonding for the first LED chip in the 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. In the process of gold wire welding, a ball is fired before the first point of pressure, and the rest of the process is similar.
Press welding is the key part of LED packaging technology. The main process needs to be monitored is the shape of the welding line (Lv Si), the shape of the arch, the shape of the solder joint and the pulling force.
9.LED sealant
LED packaging mainly has three kinds of dispensing, potting and molding. Basically, the difficulties in process control are bubbles, multiple missing materials, and black spots. Design is mainly for the selection of materials, selection of good combination of epoxy and stent. (general LED cannot pass tightness test.)
LED dispensing TOP-LED and Side-LED apply dispensing package. Manual dispensing packaging requires a high level of operation (especially white LED), the main difficulty is to control the amount of dispensing, because the epoxy will thicken during use. White light LED still has the problem of light emitting chromatic aberration caused by phosphor precipitation.
LED potting encapsulation, Lamp-LED encapsulation using potting form. The encapsulation process is to inject liquid epoxy into the LED mold cavity, then insert the pressure welded LED stent into the oven, and then remove the LED from the die cavity after the epoxy curing.
LED will support LED molded pressure 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.
10.LED curing and post cure
Curing refers to the encapsulation of epoxy curing, generally epoxy curing conditions at 135 degrees, 1 hours. Molded packages are typically 150 degrees, 4 minutes. Post cure is to allow the epoxy to be fully cured and to heat the LED at the same time. Post cure is very important to improve bonding strength between epoxy and PCB. General conditions are 120 degrees, 4 hours.
11.LED cutting and dicing
Because the LED is linked together in production (not single), the Lamp package LED uses the ribs to cut the tendons of the LED bracket. SMD-LED is on a PCB board that requires a dicing machine to complete the separation.
12.LED test
Test the photoelectric parameters of LED, check the dimensions of the products, and sort the LED products according to the customers' requirements.


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