1. Microscopic inspection of the chip: whether there is mechanical damage and pitting on the surface of the material, whether the chip size and electrode size meet the process requirements; whether the electrode pattern is complete

2. Slicing expansion: Since the LED chips are still closely arranged after cutting, the spacing is very small, which is not conducive to the operation of the subsequent process. We use a chip extender to extend the film that bonds the chip. The pitch of the LED chips is elongated to about 0.6mm. Manual expansion can also be used, but it is easy to cause problems such as chipping and waste.

3. Dispensing: Apply silver glue or insulating glue to the corresponding position of the LED bracket. The difficulty of the process lies in the control of the amount of glue, and the height and position of the glue have detailed process requirements. Since silver glue and insulating glue have strict requirements on storage and use, the wake-up, stirring and use time of silver glue are all matters that must be paid attention to in the process.

4. Gluing: Contrary to dispensing, gluing is to use a glue applicator to apply silver glue on the back electrode of the LED, and then install the LED with silver glue on the back on the LED bracket. The dispensing efficiency is much higher than dispensing, but not all products are suitable for dispensing.

5. Manual stab: Put the unfolded LED chip on the jig of the stab table, place the LED bracket under the jig, and use a needle to pierce the LED chips into the corresponding positions one by one under the microscope. Compared with automatic placement, manual chip puncturing has an advantage, that is, it is convenient to replace different chips at any time, which is suitable for products that need to install multiple chips.

6. Automatic racking: Automatic racking actually combines the two steps of immersion and chip mounting. First apply the silver glue on the LED bracket, then use the vacuum nozzle to pick up the moving position of the LED chip, and then put it in the corresponding position. in the stands. In the process of automatic listing, it is mainly to be familiar with the operation and programming of the equipment, and at the same time adjust the glue and installation accuracy of the equipment. In the selection of nozzles, try to use bakelite nozzles to prevent damage to the surface of the LED chips, especially for blue-green chips, bakelite must be used. Because the molten steel nozzle will scratch the current spreading layer on the surface of the chip.

7. Sintering: The purpose of sintering is to solidify the silver glue, and sintering needs to monitor the temperature to prevent batch failure. The sintering temperature of silver glue is generally controlled at 150°C, and the sintering time is 2 hours. According to the actual situation, it can be adjusted to 170℃ for 1 hour. Insulation glue is generally 150 ℃, 1 hour. The silver glue sintering furnace must be opened every 2 hours, and the sintered products should be replaced according to the process requirements, and must not be opened at will. The sintering furnace must not be used for other purposes to prevent contamination.

8. Pressure welding: The purpose of pressure welding is to lead the electrodes to the LED chip to complete the connection of the inner and outer leads of the product. There are two kinds of LED pressure welding process: gold wire ball welding and aluminum wire pressure welding. The picture on the right shows the aluminum wire pressure welding process. Press the first point on the LED chip electrodes first, then pull the aluminum wire to the top of the corresponding holder, press the second point, and tear the aluminum wire apart. The gold wire ball bonding process burns a ball before pressing the first point, and the rest of the process is similar. Pressure welding is a key link in LED packaging technology. The process needs to be monitored mainly for the shape of the pressure-bonded gold wire arch wire, the shape of the solder joint, and the tension. The in-depth study of the pressure welding process involves many aspects such as gold wire material, ultrasonic power, pressure welding pressure, selection of rivets, and the trajectory of reinforcement. 9. Dispensing and packaging: LED packaging is mainly divided into three types: dispensing, potting and molding. Basically, the difficulties in process control are air bubbles, material shortages and black spots. Design is primarily a choice of materials, choosing a well-bonded epoxy and bracket. Generally speaking, TOP-LED and Side-LED are suitable for dispensing packaging. Manual dispensing and encapsulation requires a high level of operation, and the main difficulty lies in the control of the dispensing amount, because the epoxy resin will thicken during use. Dispensing white LEDs also have the problem of chromatic aberration caused by the precipitation of phosphors.