IACS CO., LIMITED (Yiwu Fuwei e-commerce firm)

The packaging process of LED lamps is a high-tech thing. In this circle, there are many so-called trade secrets. Because these things are related to the survival of an enterprise, so some things are not open to everyone, including some processes or processes. These things directly determine whether the enterprise can have a central competitiveness. Today, I am here to publish the knowledge of packaging technology in the LED industry, hoping to give you some assistance.

I. Production Technology

1. Production:

A) Cleaning: PCB or LED bracket is cleaned by ultrasonic wave and dried.

B) Mounting: After the bottom electrode of LED tube core (large wafer) is equipped with silver glue, the expanded tube core (large wafer) is placed on the spinning table. Under the microscope, the tube core is mounted one by one on the corresponding pad of PCB or LED bracket, and then sintered to solidify the silver glue.

C) Pressure welding: The electrodes are connected to the core of the LED tube with an aluminium wire or a gold wire welder to act as a lead for current injection. LED is directly installed on PCB, generally using aluminium wire welding machine. (Gold wire welder is required for white TOP-LED production)

D) Packaging: LED core and welding wire are protected by dispensing and epoxy. There are strict requirements for the shape of the cured colloid when dispensing glue on PCB board, which is directly related to the brightness of backlight products. This process will also undertake the task of point phosphor (white LED).

E) Welding: If the backlight is SMD-LED or other encapsulated LED, the LED needs to be welded to the PCB board before the assembly process.

F) Film cutting: various diffusive films and reflective films needed for cutting back light source with punch die.

G) Assembly: According to the requirements of the drawings, the backlight materials are manually installed in the correct position.

H) Testing: Check the photoelectric parameters of backlight and the uniformity of light output.

2. Packaging: Packing and warehousing finished products as required.

II. Packaging Technology

1. The Task of LED Packaging

It connects the external leads to the electrodes of the LED chip, protects the LED chip and improves the efficiency of light extraction. The key processes are mounting, pressure welding and packaging.

2. LED Packaging Form

LED packaging can be described as a variety of forms, mainly according to the different application occasions to use the corresponding size, heat dissipation countermeasures and lighting effect. Leds are classified as Lamp-LED, TOP-LED, Side-LED, SMD-LED, High-Power-LED and so on.

3. LED Packaging Process

A) Chip Inspection

Microscopic examination:

1. Is there any mechanical damage and lockhill on the surface of the material?

2. Whether the chip size and electrode size meet the process requirements;

3. Whether the electrode pattern is complete or not.

B) enlargement

Because the LED chips are still arranged tightly after scratching (about 0.1mm), it is not conducive to the operation of the later process. We use the expander to expand the film of the bonded chip. The distance between the LED chips is stretched to about 0.6 mm. It can also be expanded manually, but it is easy to cause bad problems such as chip dropping and waste.

C) dispensing

Silver glue or insulating glue at the corresponding position of LED bracket.

(For GaAs and SiC conductive substrates, red, yellow and yellow-green chips with back electrodes are made with silver glue. For blue and green LED chips on sapphire insulated substrates, insulating glue is used to fix the chips. ) The technical difficulty lies in the control of dispensing quantity, and there are detailed technical requirements in colloid height and dispensing position. As silver glue and insulating glue have strict requirements in storage and use, the wake-up, stirring and use time of silver glue are all matters needing attention in technology.

D) preparation

Instead of dispensing, the glue preparation machine first coats the silver glue on the back electrode of the led, and then installs the LED with the silver glue on the back bracket. The efficiency of glue preparation is much higher than that of dispensing, but not all products are suitable for glue preparation process.

E) Manual Stitches

The expanded LED chip (backup or non-backup) is placed on the fixture of the piercing table. The LED bracket is placed under the fixture. Under the microscope, the LED chip is pierced one by one to the corresponding position with a needle. Comparing with automatic mounting, manual spinning has one advantage. It is convenient to replace different chips at any time. It is suitable for products that need to install many kinds of chips.

F) Automatic mounting

Actually, automatic mounting combines two steps of glue dipping (dispensing) and chip installation. First, silver glue (insulating glue) is applied on the LED bracket, then the LED chip is sucked up and moved by vacuum suction nozzle, and then placed on the corresponding bracket position.

In the process of automatic mounting, we should be familiar with equipment operation programming, and adjust the glue staining and installation accuracy of the equipment. Bakelite suction nozzles should be selected as far as possible in the selection of suction nozzles to prevent damage to the surface of LED chips, especially for blue and green chips. Because the nozzle will scratch the current diffusion layer on the chip surface.

G) sintering

The purpose of sintering is to solidify silver glue. Sintering requires temperature monitoring to prevent bad batch performance.

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 C for 1 hour. Insulation glue is generally 150 C, 1 hour. Silver glue sintering oven must be opened and replaced at intervals of 2 hours (or 1 hour) according to the technological requirements, and should not be opened at will. Sintering oven should not be used for other purposes to prevent pollution.

H) pressure welding

The purpose of pressure welding is to lead the electrodes to the LED chip and complete the connection between the internal and external leads of the product. There are two kinds of pressure welding processes for LED: gold wire ball welding and aluminium wire welding. The right picture is the process of aluminium wire bonding. First, the first point is pressed on the electrode of the LED chip, then the aluminium wire is pulled over the corresponding bracket, then the second point is pressed and the aluminium wire is broken. The process of gold wire ball welding is similar to that of firing a ball before pressing the first point.

Pressure welding is the key link in the LED packaging technology. The shape of arc wire, solder joint and tension of pressure welding gold wire (aluminium wire) need to be monitored. In-depth study of pressure welding process involves many problems, such as material of gold (aluminium) wire, ultrasonic power, pressure of pressure welding, selection of splitter (steel nozzle), movement track of splitter (steel nozzle), and so on. (The following figure is a micro-photograph of solder joints extruded by two different splitters under the same conditions. There are differences in the micro-structure between them, which affects the quality of products. ) We will not repeat it here.

I) dispensing package

There are three main types of LED packaging: dispensing, filling and moulding. Basically, the difficulties of process control are bubble, multi-material shortage and black spot. The design is mainly about the selection of materials and the selection of epoxy and bracket with good combination. (General LED can not pass the air tightness test) TOP-LED and Side-LED as shown in the right figure are suitable for dispensing packaging. Manual dispensing packaging requires a high level of operation (especially white LED). The main difficulty is the control of dispensing volume, because epoxy will become thicker in use. White LED dispensing also has the problem of color difference caused by phosphor precipitation.

J) Filling package

Lamp-led packaging is in the form of encapsulation. The filling process is to inject liquid epoxy into the cavity of the LED forming die, then insert the pressure-welded LED bracket into the oven to solidify the epoxy. After the epoxy is solidified, the LED is removed from the cavity and formed.

K) Molded Packaging

The pressure welded LED bracket is put into the die, the upper and lower dies are closed by hydraulic press and vacuum pumped, the solid epoxy is put into the rubber duct of the die with hydraulic ejector for heating at the entrance of the injection duct, and the epoxy enters into each LED forming slot along the rubber duct and solidifies.

L) Curing and post-curing

Curing refers to the curing of packaging epoxy. Generally, the curing condition of epoxy is 135 C, 1 hour. Molded packaging is usually at 150 C for 4 minutes.

Post curing of M)

Post-curing is to make epoxy cured adequately, while thermal aging of led. Post-curing is very important to improve the bond strength between epoxy resin and stent (PCB). The general condition is 120 C for 4 hours.

N) Reinforcement and slicing

Because LED is connected (not single) in production, Lamp encapsulated led uses rib cutting to cut the ribs of LED bracket. SMD-led is on a PCB board, which needs a slicing machine to complete the separation work.

O) test

Testing the photoelectric parameters of led, inspecting the shape size, and sorting the LED products according to customer requirements.

P) packaging

The finished products are counted and packed. Super bright LED needs anti-static packaging.

Yiwu Fuwei e-commerce firm (IACS Co., Limited) is a very professional Led manufacturer who produces high quality outdoor led light. Our popular products are solar led lights, UFO lights, underwater lights and so on. If you have any question about the led product, please feel free to contact us.