On LED packaging technology

1. Why should the LED encapsulation?
LED package is the role of the outer leads connected to the LED chip electrode, not only can protect the LED chip, and play a role in improving luminous efficiency. Therefore, complete LED package is not just the output signal, more importantly, work to protect the die, the output of visible light function. LED package of both electrical parameters can be seen, there are optical parameters of design and technical requirements, is not a simple task.

2.LED packaging equipment
As the LED package are higher, and therefore, whether it is line LED or SMD LED, must use a high-precision solid crystal, because the LED die into the package location is accurate, the whole package will directly affect the light-emitting devices efficiency. If the grain position within the reflector cup biased, the light can not be fully reflected, directly affect the LED brightness. However, with an advanced PR System (pre-image recognition system) solid crystal, regardless of differences in the quality of the lead frame, LED die can still be accurately welded to the intended location.

3.LED package
According to different applications, different dimensions, thermal solutions and glow. LED packaging a variety of forms. Currently, LED package according to classification of the main Lamp-LED, TOP-LED, Side-LED, SMD-LED, High-Power-LED, Flip Chip-LED, etc.

Lamp-LED (vertical LED)
Lamp-LED is the early stage of the line LED, it's packaged in the form of using potting. Casting process is first injected into the mold cavity forming the LED liquid epoxy resin, then insert a good LED bracket bonding, into the oven for epoxy curing, the mold cavity from the LED that is out of the molding. As the manufacturing process is relatively simple, low cost, has a higher market share.

SMD-LED (SMD LED)
SMD LED circuit board is affixed to the surface, suitable for SMT processing, can be reflow, a good solution to the brightness, viewing angle, flatness, reliability, consistency and other issues, using the lighter PCB and reflector materials , improved to remove the DIP LED heavy carbon steel pin, the display needs to be filled epoxy reflector less, aims to reduce the size, lower weight. In this way, surface mount LED products can be easily half the weight, and ultimately make the application more perfect.

Side-LED (light emitting side of LED)
Currently, LED packaging, another focus will be side-emitting package. If you want to use the LED as LCD (liquid crystal display) backlight, the LED side emitting light with the surface to be the same, in order to evenly light the LCD backlight. Although the use of lead-frame design, you can achieve the purpose of the side of light, but the heat has not worked. However, Lumileds company invented the mirror design, the surface emitting LED, the use of mirror principle to send into the side light, the success of the high power LED applications in large-size LCD backlight module.

TOP-LED (top-emitting LED)
Top emitting LED is more common SMD LEDs. Mainly used in multi-functional ultra-thin mobile phones and PDA's backlighting and status indicators.

High-Power-LED (high-power LED)
In order to obtain high power, high brightness LED light source, manufacturers in the LED chip and package design to high-power direction. Currently, the number of W can withstand the power of the LED package has emerged. For example Norlux series high power LED package structure of hexagonal aluminum as the base (it is not conductive) multi-chip combination, the base diameter of 31.75mm, light-emitting area is located in the center of a diameter of about (0.375 × 25.4) mm , can hold 40 LED die, the same time as the aluminum heat sink. This package using conventional die combination of high-density packaging, high luminous efficiency, low thermal resistance, high current under the high light output, but also a promising LED solid light.

Can be seen, the thermal characteristics of power type LED LED work directly affects the temperature, luminous efficiency, emission wavelength, lifetime, etc. Therefore, the power LED chip packaging design, manufacturing technology becomes more important.

Flip Chip-LED (flip chip LED)
LED flip-chip package structure is basically the system in the PCB has a plurality of perforations, each of the substrate side of the perforation are equipped with two different regions of the open-conductive material and each other, and the conductive material is spread on the substrate surface, without a plurality of packaged LED chip with conductive material placed on the side of each perforation, a single LED chip is the use of positive and negative contacts are solder balls and substrate material on the surface of the conductive link, and a plurality of LED chips on the side facing the perforated surface of all points with a transparent plastic material of the seal, the sealing rubber is in the shape of the sphere was half of each perforation. Are flip-chip light-emitting diode structure.

Conclusion

Light by solid physics, LED luminous efficiency near 100%, therefore, LED light source known as the 21st century, is expected to become incandescent, fluorescent, high intensity discharge lamps, the fourth generation light sources. Looking to the future, manufacturers will put high-power, high brightness LED in a prominent development position. LED industry chain in the substrate, epitaxy, chip, package, application needs and common development, multi-party interaction to cultivate, and packaged in a connecting part of the industrial chain, we need great attention and importance.