Home Uncategorized What is the process of LED pin packaging?

What is the process of LED pin packaging?

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To be able to organize into a work instruction, thank you. Please help summarize it.

1. LED chip inspection

microscopic inspection: whether there is mechanical damage on the material surface, whether the size of lockhill chip and electrode meet the process requirements, and whether the electrode pattern is complete

2. Led expansion

because the LED chips are still closely arranged after dicing, the spacing is very small (about 0.1mm), which is not conducive to the operation of subsequent processes. We use a film expander to expand the film of the bonding chip, which is to stretch the spacing of the LED chip to about 0.6mm. Manual expansion can also be adopted, but it is easy to cause bad problems such as chip falling and waste

3. Led dispensing
apply silver glue or insulating glue at the corresponding position of LED support. (for GaAs and SiC conductive substrates, silver glue is used for red, yellow and yellow green chips with back electrode. For blue and green LED chips with sapphire insulating substrate, insulating glue is used to fix the chip.)

the difficulty of the process lies in the control of dispensing amount. There are detailed process requirements for colloid height and dispensing position
due to the strict requirements for the storage and use of silver glue and insulating glue, the waking, mixing and use time of silver glue are all matters that must be paid attention to in the process

4. Led glue preparation
contrary to dispensing, glue preparation is to use the glue preparation machine to apply silver glue to the electrode on the back of the LED, and then install the LED with silver glue on the back on the LED support. The efficiency of glue preparation is much higher than that of dispensing, but not all products are suitable for glue preparation process

5. Led manual pricking

place the expanded LED chips (with or without glue) on the fixture of the pricking table, put the LED support under the fixture, and prick the LED chips to the corresponding positions one by one with a needle under the microscope. Compared with automatic rack mounting, manual stabbing has one advantage, which is convenient to replace different chips at any time. It is suitable for products that need to install a variety of chips

6. Automatic mounting of LED

automatic mounting is actually a combination of two steps: dipping (dispensing) and installing the chip. First, point silver glue (insulating glue) on the LED bracket, then use the vacuum nozzle to suck the LED chip up to the moving position, and then place it on the corresponding bracket position. In the process of automatic rack mounting, it is mainly necessary to be familiar with the operation and programming of the equipment, and adjust the glue dipping and installation accuracy of the equipment at the same time. In the selection of suction nozzle, try to use bakelite suction nozzle to prevent damage to the surface of LED chip, especially the blue and green chips must use bakelite. Because the steel nozzle will scratch the current diffusion layer on the chip surface

7. Led sintering
the purpose of sintering is to solidify the silver glue. The sintering requires monitoring the temperature to prevent batch defects. The sintering temperature of silver glue is generally controlled at 150 ℃, and the sintering time is 2 hours. It can be adjusted to 170 ℃ for 1 hour according to the actual situation. Insulating glue is generally 150 ℃ for 1 hour

the silver glue sintering oven must be opened every 2 hours (or 1 hour) according to the process requirements, and the sintered products must not be opened at will. The sintering oven shall not be used for other purposes to prevent pollution

8. Led pressure welding
the purpose of pressure welding is to lead the electrode to the LED chip and complete the connection of internal and external leads of the product
there are two kinds of pressure welding processes for LED: gold wire ball welding and aluminum wire pressure welding. The right figure shows the process of aluminum wire pressure welding. First press the first point on the electrode of LED chip, then pull the aluminum wire above the corresponding support, press the second point, and then tear the aluminum wire. In the process of gold wire ball welding, burn a ball before pressing the first point, and the other processes are similar
pressure welding is a key link in LED packaging technology. The main processes to be monitored are pressure welding gold wire (aluminum wire), arch wire shape, solder joint shape and tensile force

9. Led sealing glue
LED packaging mainly includes dispensing, potting and molding. Basically, the difficulties of process control are bubbles, multiple material shortages and black spots. The design mainly focuses on the selection of materials and the selection of epoxy and support with good combination. (general LEDs cannot pass the air tightness test)

9.1 led dispensing:

Top led and side LED are suitable for dispensing packaging. Manual dispensing packaging requires high operation level (especially white LED). The main difficulty is to control the dispensing amount, because the epoxy will thicken during use. The dispensing of white LED also has the problem of light color difference caused by phosphor precipitation

9.2 led glue filling package
lamp LED is encapsulated in the form of pouring. The filling and sealing process is to inject liquid epoxy into the LED forming mold cavity, then insert the pressure welded LED support, put it into the oven for epoxy curing, and then take the led out of the mold cavity to form

9.3 led molded packaging

put the pressure welded LED support into the mold, close the upper and lower molds with a hydraulic press and vacuum, put the solid epoxy into the inlet of the glue injection channel, heat it, press it into the mold rubber channel with a hydraulic ejector rod, and the epoxy enters each LED forming groove along the rubber channel and solidifies

10. LED curing and post curing
curing refers to the curing of encapsulated epoxy. Generally, the curing condition of epoxy is 135 ℃ for 1 hour. Molded packaging is generally at 150 ℃ for 4 minutes. Post curing is to fully cure the epoxy and heat age the LED at the same time. Post curing is very important to improve the bonding strength between epoxy and support (PCB). The general condition is 120 ℃ for 4 hours

11. Led rib cutting and dicing
since LEDs are connected together in production (not single), lamp encapsulated LEDs use rib cutting to cut the connecting rib of LED support. Smd-led is on a PCB board and needs a dicing machine to complete the separation work

12. LED test
test the photoelectric parameters of LEDs, check the overall dimensions, and sort LED products according to customer requirements

13. LED packaging
count and package the finished products. Super bright LEDs need anti-static packaging.

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