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LED Package Collection: LED packaging technology knowledge can not be unknown

Number of visits: Date:2016-05-25
LED lamp packaging technology LED is a high-tech things in this circle inside, there are many so-called trade secrets, as these things relate to a company's survival, so some things are not all open, including some processes or process. These things can have a direct resolution enterprises core competitiveness, released here today learning about LED industry, packaging technology, hoping to give you some help.
First, the production process
1, the production:
a) Cleaning: ultrasonic cleaning PCB or LED support, and drying.
b) pallet: the led die (wafer) bottom electrode saddled silver glue after expansion, the die (wafer) after the expansion thorn crystal placed in the table, under the microscope with thorn crystal pen will die mounted on a PCB or LED stent corresponding pads, followed by sintering silver glue curing.
c) bonding: aluminum wire or gold wire electrodes connected to the LED die to make current injection leads. LED mounted directly on the PCB, generally use aluminum wire welding. (TOP-LED need to make white gold wire welder)
d) Packaging: By dispensing with epoxy to the LED die and wire up. In the PCB board dispensing, colloidal shape after curing, there are strict requirements, which is directly related to the brightness of the backlight of the finished product. This process will also assume point phosphor (white LED) task.
e) Welding: If the backlight is SMD-LED or other encapsulated LED adoption in the assembly process, LED needs to be soldered to the PCB board.
f) cutting film: punch die with all kinds of necessary backlight diffusion film, reflective film.
g) Assembly: according to drawings, various materials backlight manually install the correct location.
h) Test: Check the backlight optical parameters and light uniformity is good.
2. Packing: The finished product required packaging, warehousing.
Second, the packaging process
1, LED packaging tasks
The outer leads are connected to the electrodes of the LED chip, while protecting the chips led, and acts to improve the light extraction efficiency. There are key process racking, bonding, packaging.
2, LED package
LED package can be said it is varied, mainly corresponding dimensions according to different applications, thermal response and light effects. led by package classification Lamp-LED, TOP-LED, Side-LED, SMD-LED, High-Power-LED and the like.
3, LED packaging process
a) test chip
Microscopy:
1, surface mechanical damage and pitting Ma pit (lockhill);
2, the chip size and the size of the electrode meets the process requirements;
3, the electrode pattern is complete.
b) spread sheet
Since the LED chip dicing still arranged after the close spacing is small (about 0.1mm), is not conducive to the operation after step. We use a tablet machine to expand the chip bonding membrane expansion, it is the LED chip spacing stretched to about 0.6mm. You can also use manual expansion, but is likely to cause chips fall waste and other undesirable problems.
c) Dispensing
In the corresponding location points led bracket silver plastic or rubber insulation.
(For GaAs, SiC conductive substrate, red, yellow, green chip having a back electrode, silver glue. Insulating sapphire substrates for blue, green led chip, glue for fixing the chip with insulation.) Technical Difficulties glue that control point, in colloidal height of the dispensing location are detailed process requirements. Since the silver plastic and rubber insulation in the storage and use are strict requirements, silver plastic material awake and stirring time is important to note the use of the technology matters.
d) Preparation of glue
And dispensing the contrary, prepare plastic is prepared melter first silver paste electrode coated on the back led, then led back with a silver plastic holder mounted on the led. Preparation of glue dispensing efficiency is much higher than, but not all products are suitable for glue preparation process.
e) hand-thorn-chip
After the expansion of LED chips (prepared glue or glue equipment) disposed on the substrate stage thorn fixture, LED stent placed under the jig under a microscope using a needle prick a LED chip to the appropriate location. Manual and automatic pallet thorn sheet compared to a benefit, to facilitate ready to switch to a different chip for the chip need to install a variety of products.
f) Automatic pallet
Automatic pallet is a combination of stick gum (glue) and two step installation chip, led to the bracket point silver plastic (insulating plastic), followed by vacuum suction nozzle to pick up movement led chip location, and then placed in corresponding bracket position.
Automatic pallet on the main process equipment should be familiar with the programming operation, while James plastic equipment and installation precision adjustment. On the choice of nozzle try to use bakelite nozzle to prevent damage to the surface of the chip led, in particular blue, green chip must be bakelite. Because the steel tips can scratch the surface of the current diffusion layer chip.
g) sintering
The purpose is to make the sintering silver glue curing, sintering requires temperature monitoring to prevent bad batch of.
Silver paste sintering temperature control in 150 ℃, sintering time of 2 hours. According to actual conditions can be adjusted to 170 ℃, 1 hour. Plastic insulation is generally 150 ℃, 1 hour. Silver plastic sintering oven process requirements must be every 2 hours (or 1 hour) to open the replacement of sintered products, intermediate not free to open. Sintering oven for other purposes shall not prevent pollution.
h) bonding
The purpose of bonding the electrode lead to the led chip, complete the connection work products inside and outside leads. LED's have a gold ball bonding process brazing two kinds of aluminum wire. The right is aluminum wire bonding process, the first LED chip electrodes on the first pressure point, and then the aluminum strands to the corresponding bracket above, the pressure on the second point after tearing aluminum wire. Gold ball bonding process in the press before the first point before burning balls, similar to the rest of the process.
Bonding LED packaging technology is a key link in the process need to be monitored is the main bonding gold wire (aluminum wire) wire arch shape, solder joint shape, tension. In-depth study of the bonding process involves many problems, such as gold (aluminum) wire material, ultrasonic power, bonding pressure, chopper (steel tip) selection, chopper (steel tip) trajectory, and so on. (The figure is under the same conditions, two different pressure out of the chopper pad microscopic photograph, the two differ in their microstructure, which affects the quality of products.) Here we no longer tired.
i) dispensing package
LED package mainly a little glue, potting, molding three. Basically difficulty of process control is a bubble, more lack of material, black spots. Designed mainly for the selection of materials, combined with a good selection of epoxy and bracket. (General LED can not leak test) as shown at right TOP-LED and Side-LED suitable dispensing package. Manual dispensing package for demanding operating level (especially white LED), the main difficulty is dispensing volume control, because the epoxy will thicken during use. White LED phosphor dispensing there is a light color precipitate cause of the problem.
j) filling plastic packaging
Lamp-led package in the form of potting. Potting process is led in the first cavity injection molding liquid epoxy, then insert a good bonding led bracket, epoxy curing oven so that later, led emerge from the mold cavity that is formed.
k) mold package
The good bonding led stent placed in a mold, the upper and lower two hydraulic mold clamping and vacuum, the solid epoxy glue injection into the channel inlet heating hydraulic ram is pressed into rubber molds Road, epoxy Shun Road access to all the plastic molding led bath and cured.
l) after curing and curing
Curing means curing epoxy encapsulation, typically an epoxy curing conditions at 135 ℃, 1 hour. Mold package is generally 150 ℃, 4 minutes.
m) after curing
After curing is to allow sufficient curing epoxy, while led thermal aging. After curing the epoxy it is very important for improving the stand (PCB) of the adhesive strength. General conditions of 120 ℃, 4 hours.
n) cut tendons and dicing
Since led in production are linked together (not individual), Lamp package led by cutting the tendons cut led bracket connected tendons. SMD-led are in the midst of the PCB, need dicing machine to complete the work of separation.
o) test
Optical parametric test led, inspection dimensions, while the LED product sorting according to customer requirements.
p) Packaging
The finished counting packaging. Super bright LED need anti-static packaging.

 

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