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LED packaging Collection: I do not know the LED packaging process knowledge
- Dec 26, 2017 -

LED packaging Collection: I do not know the LED packaging process knowledge

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LED lamp packaging process LED is a high-tech stuff, in this circle there are many so-called commercial secrets, because these things are related to the survival of a business, so some things are not open to everyone, including some processes or Process. These things directly determine whether the company can have the center of competitiveness, today announced here LED packaging technology industry knowledge, hoping to give you some assistance.


First, the production process


1, production:


A) Cleaning: Use ultrasonic cleaning PCB or LED bracket, and drying.


b) Racking: Expanding the silver paste on the bottom electrode of led die (large wafer), placing the dilated die (large wafer) on the jacketed stage, One by one, mounted on the corresponding pads of the PCB or LED bracket, followed by sintering to cure the silver paste.


C) Pressure welding: Connect the electrode to the LED die with an aluminum or gold wire bonder to make the lead for current injection. LED directly mounted on the PCB, the general use of aluminum wire welder. (Production of white TOP-LED gold wire welding machine required)


D) Packaging: LED die and wire are protected with epoxy by dispensing. Dispensing on the PCB board, the shape of the gel after curing have strict requirements, which is directly related to the brightness of the backlight finished product. This procedure will also assume the task of phosphor (white LED).


E) Soldering: If the backlight is SMD-LED or other encapsulated LEDs, the LED needs to be soldered to the PCB before the assembly process.


F) cut film: Die with a punch die backlighting all kinds of diffusion film, reflective film.


G) Assembly: According to the drawing requirements, the backlight of the various materials manually installed in the correct location.


H) Test: Check the backlight photoelectric parameters and light uniformity is good.


2, packaging: the finished product according to the requirements of packaging, storage.


Second, the packaging process


1, LED package of the task


Is connected to the outer lead LED chip electrode, while protecting the LED chip, and play to improve the efficiency of light extraction. The key processes are rack, pressure welding, packaging.


2, LED package


LED package can be said that a wide variety of forms, mainly according to different applications using the appropriate dimensions, cooling measures and the light effect. led by the package classification of Lamp-LED, TOP-LED, Side-LED, SMD-LED, High-Power-LED and so on.


3, LED packaging process


A) Chip inspection


Microscopy:


1, the surface of the material is mechanical damage and pockmarked pit (lockhill);


2, chip size and electrode size is in line with process requirements;


3, the electrode pattern is complete.


B) Expanding


As the LED chip is still arranged in the scribe close spacing is very small (about 0.1mm), is not conducive to the operation of the process. We use the expansion machine to bond the film to expand the chip, LED chip spacing is stretched to about 0.6mm. Can also be used to manually expand, but it is easy to cause chip drop waste and other undesirable issues.


C) Dispensing


In the corresponding position bracket led silver plastic or plastic insulation.


(For GaAs, SiC conductive substrates, red, yellow, and yellow chips with back electrode, silver paste is used.) For blue and green led chips with sapphire insulation, the chip is fixed with insulating glue.) Difficulties Is the amount of plastic control, in the colloid height, dispensing location has a detailed process requirements. As the silver plastic and insulating plastic in storage and use have strict requirements, silver glue wake up, mixing, the use of time are the process must pay attention to matters.


D) glue


And dispensing the contrary, the glue is prepared with a glue machine first silver plastic coated on the back of the led electrode, and then back with silver plastic led mounted on the led bracket. The efficiency of glue preparation is much higher than the dispensing, but not all products are suitable glue preparation process.


E) Hand stab


After the expansion of the LED chip (prepared or not plastic) placed in the fixture of the thorn table, LED bracket on the bottom of the fixture, under the microscope with a needle LED chips to the corresponding position. There is a benefit of hand-held laryngosaurs compared to the automatic rack-mount, making it easy to replace different chips at any time for products that require the mounting of multiple chips.


F) Automatic rack


Automatic rack is actually a combination of glue stick (dispensing) and the two steps to install the chip, the first bracket on the led silver plastic (insulating plastic), and then use the vacuum nozzle will suck the led chip mobile position, and then placed in The corresponding bracket position.


Automatic rack in the process are mainly familiar with the equipment operation and programming, at the same time, equipment, glue and installation accuracy adjustment. In the choice of suction nozzle try to use bakelite nozzle to prevent the damage on the led chip surface, especially blue, green chips must be bakelite. Because the mouth of steel will scratch the chip surface current diffusion layer.


G) Sintering


The purpose of sintering is to make silver glue curing, sintering requires temperature monitoring, to prevent poor batch.


Silver plastic sintering temperature is generally controlled at 150 ℃, sintering time 2 hours. According to the actual situation can be adjusted to 170 ℃, 1 hour. Insulation plastic generally 150 ℃, 1 hour. Silver plastic baking oven must press the process requirements every 2 hours (or 1 hour) to open the replacement of sintered products, the middle not free to open. Sintering oven can not be used for other purposes, to prevent pollution.


H) pressure welding


The purpose of pressure welding leads to the electrode led chip to complete the connection of the product inside and outside the lead. LED pressure welding process has a gold wire ball welding and aluminum wire pressure welding two. The right is aluminum wire pressure welding process, the first chip in the LED chip pressure on the first point, and then pull the aluminum wire to the top of the corresponding bracket, the second point after the pressure on the aluminum wire. Gold wire ball welding process is in the first pressure before burning a ball, the rest of the process is similar.


Pressure welding LED packaging technology is the key link in the process of the main need to monitor the pressure welding gold wire (aluminum wire) arch shape, solder joint shape, tension. In-depth research on the pressure welding process involves many aspects, such as gold (aluminum) wire material, ultrasonic power, pressure welding pressure, riveting knife (steel nozzle) selection, riveting knife (steel nozzle) trajectory and so on. (The figure below is under the same conditions, the two different capillary pressure of the solder joint micro-photos, both in the microstructure there is a difference, thus affecting the product quality.) We are not here tired.


I) Dispensing package


LED package is the main plastic, potting, molded three. Basically the difficulty of process control is the bubble, lack of material, black spots. Design is mainly the selection of materials, the selection of a combination of good epoxy and stent. (General LED can not pass the air tightness test) As shown on the right TOP-LED and Side-LED suitable dispensing package. Manual dispensing encapsulation demanding level of operation (especially white LED), the main difficulty is the amount of plastic control, because the epoxy will thicken during use. White LED dispensing there is also the problem of phosphor color mixing caused by precipitation.


J) Glue package


Lamp-led package using potting form. The process of potting is to inject liquid epoxy into LED mold cavity first, and then insert the good welded bracket into the oven, put it into the oven to make the epoxy solidified, then led out from the mold cavity to form.


K) Molded package


The pressure welded led bracket into the mold, the upper and lower mold with a hydraulic machine clamping and evacuated, the solid epoxy into the plastic injection port heating hydraulic plunger pressed into the mold glue, epoxy cis With plastic into each led molding groove and curing.


L) Curing and post curing


Curing is curing epoxy encapsulation, the general epoxy curing conditions at 135 ℃, 1 hour. Molded package is generally 150 ℃, 4 minutes.


M) after curing


After curing is to allow epoxy fully cured, while heat aging led. Post-cure is important to improve the bond strength of the epoxy with the support (PCB). The general conditions of 120 ℃, 4 hours.


N) Cut and dice


As led in the production are linked together (not a single), led package led package cut off led stent with tendons. SMD-led is in a PCB board, need to dicing machine to complete the separation work.


O) Test


Test led optoelectronic parameters, test the size, at the same time, according to customer requirements LED products sorting.


P) Packaging


The finished product count packaging. Super bright LED requires anti-static packaging.




Source: HC