LED packaging structure and technology of multiple forms of

Made of red, green, orange, yellow LED production accounts for about 12% of the world's total, "fifth" period the industry goal is to achieve an annual output of 30 billion ability to achieve high brightness LED epitaxial wafers and AiGslnP the chip large-scale production, annual output of more than 1 billion of red, orange, yellow super bright LED die, the key breakthrough in GaN materials technology, blue, green, white LED's in mass production. It is predicted that by 2005 the international market demand for LED is about 200 billion, with sales of 800 billion U.S. dollars.
Link in the LED industry, the upstream substrate LED chip and the substrate is produced, the middle reaches of the industry into the design and manufacture of LED chip production, downstream owned LED packaging, testing, research and development of low thermal resistance, excellent optical characteristics, packaging technology is highly reliable New LED to practical, the only way to market the industry, in a sense is a link to industry and the bond market, only to become the end product packaged in order to put into practice in order to provide customers with services to enable chain interlocking, seamless flow. Special LED LED packaging technology package in discrete devices are mostly based on the development of packaging technology evolved, but it is very special.
In general, discrete devices are sealed die inside the package, the package main function is to protect the die and the completion of electrical interconnection. The LED package is the complete output signals, protect the die work, output: the function of visible light, both electrical parameters, but also the design of optical parameters and technical requirements, can not simply be packaged discrete devices for LED.
LED light-emitting part of the core is a p-type and n-type semiconductor pn junction consisting of the die, when the pn junction into the minority carrier and majority carrier recombination, it will send visible light, ultraviolet light or near infrared light. However, photons emitted pn junction non-directional, and immediately fired in all directions have the same probability, therefore, not all the light generated by the die can be released, depending on the quality of semiconductor materials, structure and geometry of the die , the package internal structure and encapsulation materials, improved LED applications require internal and external quantum efficiency. Conventional-type LED package Φ5mm is a square of side length 0.25mm die bonding or sintering the shelves in the lead, the positive die and the gold contact points through the sphere, bonded to the lead with a pin connected to the negative through the reflection Cup and the lead frame is connected to another pin, and then the top with epoxy resin coating.
The role of reflective glass is to collect the die side of the screen the light emitted within the desired direction angle fired. Top of the envelope made of epoxy resin to shape, there is some role: to protect the die from outside such as erosion; using different shapes and material properties (doped or not doped bulk reagent), or diffuse from the lens lens function, control the light divergence angle; tube core refractive index associated with too much air, causing the die is very small within the total reflection critical angle, the light generated by the active layer is removed only a small part of the most easily in by multiple reflections within the die has been absorbed, prone to loss of ATR leads to too much light, choose the appropriate transition of the refractive index of the epoxy resin to improve die efficiency of the light emitted. Used as a form of epoxy resin shell must have moisture resistance, insulation, mechanical strength, the die emits light on the refractive index and transmission rate.
Select a different refractive index of packaging materials, packaging geometry of the photon escape efficiency is different, the angular distribution of luminous intensity and the die structure, light output, encapsulated lens material and the shape used. The use of a tapered resin lens, can focus light to the LED in the axial direction, the corresponding small angle; If the top of the resin lens is round or flat type, the corresponding angle will increase. In general, LED's emission wavelength with temperature change is 0.2-0.3nm / ℃, spectral width increases, the degree of bright colors.
In addition, when forward current flows through the pn junction, the junction loss fever temperature rise at room temperature near the temperature rises 1 ℃, LED luminous intensity will be correspondingly reduced by 1%, the package heat dissipation; to maintain color purity and luminous intensity is very important, in the past to use more ways to reduce the drive current and lower junction temperature, the majority of LED drive current is limited to 20mA or so.
However, LED light output with the increase of current, at present, a lot of power type LED drive current up to 70mA, 100mA or 1A level, need to improve the packaging structure, the new LED package design concepts and structure of low thermal resistance package and technology, improved thermal characteristics. For example, the use of large area flip-chip structure, using a good thermal conductivity of silver plastic, metal stents increase the surface area of ​​the silicon carrier solder bump heat sink mounted directly superior method. In addition, application design, PCB circuit board thermal design, thermal performance is also very important. In the 21st century, LED's efficient, high brightness of, and continuously developed panchromatic, red, orange LED light effect has been reached 100Im / W, the green LED is 501m / W, the luminous flux LED alone has reached tens of Im.
LED chip and package design is no longer along the idea of ​​Gong and manufacture of traditional modes of production, increasing the chip's light output, changes in materials research and development is not limited to the number of impurities, lattice defects and dislocations to improve internal efficiency, while improving the internal structure of the die and package, enhanced LED internally generated photons emitted chance to improve the light efficiency, solve the heat, get light and heat sink optimization of design, improved optical performance, speed up the process of SMD surface mount technology is the main direction of industry R & D .
Type of product packaging structure has been since the nineties of last century, LED chips and materials made a number of breakthroughs in technology research and development, transparent substrate ladder structure, texture, surface structure, flip chip structure, the commercialization of high brightness (1cd more) red, orange, yellow, green and blue LED products have asked the city, as shown in Table 1, 2000 in the low, medium and light flux to get the special application. LED's on the middle reaches of industry has been unprecedented attention to further promote the downstream packaging technology and industrial development, the structure of different forms and sizes of packaging, different LED die colors and color, or tri-color combination, can produce more kinds of series, varieties, specifications of the product.
LED package structure of the type of product, but also under the light color, chip material, brightness, size and other characteristics to classify the case. General constitute a single die light source, a number of the die assembly generally constitute a surface light source and line source for information and display with status indicators, LED displays are also using multiple die, die by the appropriate connections (including series and parallel) with the appropriate combination of optical structure to form light-emitting section and light-emitting display points. Gradual replacement of surface mount LED to pin type LED, a more flexible application design, LED display market has been in the possession of a certain share, to accelerate the development trend.
Some solid lighting products to market, become the next LED in the medium and long term development. Pin-type package pin type LED lead frame package for various packages used a pin shape is successfully developed the first package on the market structure, number of species range, high technology maturity, structure and reflector inside the package is still continuous improvement.
By most standard LED display industry, customers believe is the most convenient and most economical solution, placed in a typical traditional LED 0.1W input power can withstand the encapsulation within the 90% of the heat is from the negative pin distributed to the PCB board rack, and then released into the air, how to reduce the working pn junction temperature rise is packaged with the application must be considered. Encapsulation materials, high temperature curing epoxy resin and more, its light performance, process adaptability, high reliability, can be made transparent and colored transparent colored or colorless or colorless scattering scattering lens package different lens shape constitute a variety of shapes and sizes, for example, round by diameter into Φ2mm, Φ3mm, Φ4.4mm, Φ5mm, Φ7mm and several species of different components of epoxy resin can produce a different glow.
There are many different color light source package structure: ceramic base epoxy resin has good temperature performance, pin can be bent into the desired shape, small size; metal base plastic reflector-type package is an energy saving light , suitable for use as power indicator; flash-type oscillator circuit the CMOS chip and LED die-packed, self-produced a strong visual impact of the flashing light; color model by two different colors of light-emitting die form, packaged in the same ring epoxy resin lens, in addition to color outside the color can be mixed to obtain a third, in the large screen display system is extremely broad, and can be composed of two-color display packaging; voltage current source chip and the LED will die combination package, you can replace 5-24V direct various voltage indicator.
LED surface light source is more than the die bonding requirements in the micro-location on the PCB board, cover with plastic reflector box and the formation of epoxy potting, PCB board design to determine the different arrangement and connections outside the lead, with double row straight such as interpolation and single in-line structure. Point, surface light source package has been developed hundreds of shapes and sizes, suitable for the market and customers.
LED digital tube LED display could be tube or meters words, symbols, tubes, rectangular tubes, a variety of many products, Chen, from the actual needs of the design into various shapes and structures. Digital control, for example, a reflector-type, single-chip integrated, single package structure of three seven-segment type, and so, connections are both common anode and common cathode, one is often said that the digital control, two or more commonly known as the monitor.
Reflector type with a font is large, material saving, hybrid package assembly of flexible features, usually with white plastic made into seven sections of the cavity with a reflector shaped shell, a single LED die bonding with the seven reflector reflector alignment of the PCB board to each other, each reflecting the center of the bottom cavity is formed by light-emitting die area, using wire bonding method for bonding, the drops were in the reflector epoxy, glue the die and the PCB board adhesion to the bit, and then curing Serve.
Reflector-type is divided into two kinds of air sealing and real closure, the former agent with the dye by scattering epoxy resin, used for flat, two-bit devices; which cover filter and even film, and in the die and coated transparent plastic insulation on the floor, improve the efficiency of light, generally used for more than four figures. Monolithic integrated chip in the light-emitting materials, a large number of segment digital display graphics production die, and then split into single-chip graphics dicing die, bond, bonding, packaging with the lens (commonly known as fish eye lens) of the shell. Single seven-segment type will have a good production of large area LED chips, containing a plan or just cut into the core of the light bar, so the same seven bond can be attacked in the digital shelves shaped by pressure welding, epoxy resin encapsulation composition. Monolithic, single-type is characterized by miniaturization, can be dual in-line package, mostly for products.
LED Bargraph display circuit board in the 106mm length to accommodate just 101 core (up to 201 just core), is a high-density packaging, the use of optical refraction, the light source through the transparent casing of 13-15 bar grating imaging Just from the point of completion of each core to the line display, packaging technology is more complex. Semiconductor pn junction LED electroluminescence mechanism of the decision could not produce a continuous spectrum of white light, while one can not only produce two or more LED's high brightness monochromatic light, only in the package with the help of fluorescent substance, blue or UV LED tube phosphor coating on the core, indirect broadband spectrum, synthetic white; or using several (two or three, many) made different shade of the die is encapsulated in a component of the shell, through the shade of the mixed composition white LED . Both of these methods to obtain practical, Japan, in 2000 the production of white LED up to 1 million, to develop into a class of stable glowing products, and more than just pairs of luminous flux white LED design and assembly do not ask, as the partial decoration Lord, the pursuit of trendy electric light.
In 2002 surface mount package, surface mount package LED (SMD LED) have been gradually accepted by the market and gain some market share shift from the pin SMD type package development consistent with the overall trend in the electronics industry, many manufacturers launched such products. Most of the early use of SMD LED with a transparent plastic body SOT-23 improved, dimensions 3.04 × 1.11mm, disc container volume taping. Based on the SOT-23, developed high-brightness SMD lens with the SLM-125 Series, SLM-245 Series LED, the former is monochromatic light, the latter two-color or tri-color light. In recent years, SMD LED as a development hot spot, a good solution to the brightness, viewing angle, smoothness, reliability, consistency and other issues, the use of lighter materials, PCB board and the reflective layer, reflective layer need to fill in the show ring less epoxy resin, and removal of heavy carbon steel pin, by reducing the size, lower weight, can easily reduce the weight of half of the product, and ultimately make the application more perfect, especially for indoor, semi-outdoor full color display screen applications. The cooling pad is an important channel for the SMD LED manufacturers to provide data to 4.0 × 4.0mm are based on the pad, the pad can be designed using reflow and pin equal.
High brightness LED products can be used PLCC (plastic leaded chip carrier with) -2 package dimensions for the 3.0 × 2.8mm, high brightness through a unique method of assembly of the die, the product thermal resistance of 400K / W, according to CECC soldered the intensity was issued in the drive current of 50mA 1250mcd. Seven-Segment-style one, two, three and four digital SMD LED display character height of 5.08-12.7mm, the display size wide range of options. To avoid the pin PLCC package segment digital display insert with the pins by hand required to align the process, in line with automatic pick - mount equipment production requirements, application design space flexibility, bright clear display. Multi-color PLCC package with an external reflector can be easily guided with the LED, or light combined with reflective replace the existing transmission-type optical design for large areas to provide uniform lighting, R & D in 3.5V, 1A drive work under conditions of power-type SMD LED package.
Power type package to the high-power LED chip and package direction, generating a large current 10-20 times more than Φ5mmLED large luminous flux, the heat must be used effectively with the deterioration of the packaging materials do not solve the problem of bad light, so shell and packaging is the key technology, can withstand a few W power LED package has emerged. 5W series of white, green, blue and green, and blue LED power-based begin shipping in early 2003, white LED light output up to 1871m, light effect 44.31m / W green light failure problems, the development of affordable 10W power LED, a large area of ​​pipe; dagger size 2.5 × 2.5mm, current work in 5A, the light output of up to 2001m, as the solid-state lighting source that has ample room.
Luxeon power LED series is A1GalnN power type flip die flip chip bonding with solder bumps on the silicon carrier, and then complete the flip chip bonding of silicon carrier into the heat sink and the shell, the encapsulated wire bond. This package for the light extraction efficiency, thermal performance, and increase the current density are designed to work best.
Its main features: resistance is low, typically only 14 ℃ / W, only the conventional LED's 1 / 10; reliability, packaging flexibility and stability within the gel filled in the range -40-120 ℃, the temperature will not produced by sudden changes in internal stress, so that gold and disconnect the lead frame and epoxy lens to prevent yellowing, lead frame and will not stain due to oxidation; reflector and lens design allows the best control and optical radiation pattern the highest efficiency. In addition, its output power, external quantum efficiency, performance, LED solid light source to a new level.
Norlux series power LED package structure of hexagonal aluminum as the base (it does not conduct electricity) and 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 be LED die 40 to accommodate, at the same time as the aluminum heat sink. Wire bonding the die base made by the two points of contact with the positive and negative connections, according to the size of the required output power to determine the arrangement of the base number of the die, the package can be combined and ultra-high brightness AlGaInP AlGaInN die, the emitted light are monochrome, color or synthetic, white, and finally with high refractive index of the material encapsulated by the shape of the optical design. This package using conventional die combination of high-density packaging, light extraction efficiency, low thermal resistance, better protect the die and wire bonding, the large current under high optical output power, is a promising The LED solid light.
In the application can be packaged product assembled in a sandwich with a metal core PCB aluminum plate to form a power density of LED, PCB board as a device used electrodes to connect the wiring, aluminum sandwich heat sink can be used to obtain higher fat and energy conversion efficiency of luminous flux. In addition, small volume SMD LED encapsulated, can be flexibly combined to form modular, light guide plate type, concentrating, and other colorful reflective lighting. Thermal characteristics of power type LED LED direct impact on the operating temperature, luminous efficiency, emission wavelength, lifetime and so, therefore, the power type LED chip packaging design, manufacturing technology has become more important.