LED packaging technology are discrete devices in the packaging technology on the basis of development and evolved, but it's very special. Under normal circumstances, the separation of the device die in the package was sealed in the body, the role of the main package is to protect the die and the completion of the electrical interconnection. The LED package is the completion of the output signal, and die to protect the normal work output: the function of visible light, both electrical parameters and optical parameters of design and technical requirements, not simply the separation of the device used to package LED.
LED light-emitting part of the core by the p-type and an n-type semiconductor pn junction die when injected into a small number of pn junction of the carrier and most of the carrier compound, we will send out visible light, ultraviolet light or near-infrared light . Pn junction, but the district issued a non-photon orientation, firing in all directions to the same probability, not have all the die-ray can be released, depending on the quality of semiconductor materials, structure and die geometry , The internal structure of the package and encapsulation materials, LED applications to improve the internal and external quantum efficiency. Φ5mm conventional type LED package is 0.25mm side of the square die bonding or sintered in the lead on the shelf, die of the ball through the positive point of contact with the gold, bonding for the lead with a pin and connected through the negative Reflection Cup lead frame and the other linked to the pin, and then at the top of its encapsulation with epoxy resin. Cup is a reflection of the role of the collection side of the die, light interface, to the desired angle in the direction of the launch. At the top of the encapsulation resin into a certain shape, there are several roles: to protect die from the outside world, such as erosion; different shape and nature of the material (or non-doped powder doped color agent), or from diffuse lens Lens function, control of light divergence angle; die refractive index associated with the refractive index of air too, with the result that die within the critical angle of total reflection is very small, the active layer of light generated by only a small proportion of out, in the most vulnerable Die by the number of internal reflection and absorbed, prone to excessive lead to total reflection light losses refractive index of the corresponding choice of epoxy resin to make the transition to raise the light die out shooting efficiency. Pose as a shell of epoxy resin should have humidity, insulation, mechanical strength, die on the issue of light transmittance and high refractive index. Choose a different refractive index of packaging materials, packaging geometry of the photon escape the impact of efficiency are different angle of the luminous intensity distribution and structure of the die, light output, the lens used in packaging materials and related forms. Jianxing the use of a resin lens enables the LED light on the direction of the axis, the smaller angle; If at the top of the resin lens for round or flat type, and its perspective will be increased accordingly.
Under normal circumstances, LED light wavelength with temperature changes for the 0.2-0.3nm / ℃, spectral width increases, the degree of impact of bright colors. In addition, when currents are flowing through pn junction, fever and loss of balance so that the district have a temperature rise in the near room temperature, the temperature increase per 1 ℃, LED light intensity will be reduced to about 1%, cooling package; when To maintain the purity of color and luminous intensity is very important, in the past, the use of its drive to reduce the current approach to reduce junction temperature, the majority of the LED drive current limit of about 20mA. However, LED light output will increase with the current increase, at present, a lot of power-LED driver can achieve the current 70mA, 100mA or 1A level, the need to improve the structure of the package, the new LED packaging design and low thermal resistance Package structure and technology to improve the thermal characteristics. For example, the use of large flip-chip structure, selection of good thermal conductivity properties of silver plastic, metal stents increase the surface area of silicon carrier solder bump direct heat sink mounted on a first-class approach. In addition, the application in the design, PCB board, such as the thermal design, thermal performance is also very important.
In the 21st century, LED high-performance, ultra-high brightness, and the continuous development of innovative full color, red, orange LED luminous efficiency has reached 100Im / W, Green LED for the 501m / W, luminous flux of the LED alone has reached tens of Im. LED chip and package is no longer Gong along the traditional design and manufacturing production, increasing the chip's light output, the R & D is not limited to material changes in the number of impurities and lattice defects and dislocations to improve internal efficiency and at the same time, how To improve the package and die of internal structure, strengthen internal LED photon have a chance of shooting and improve optical efficiency, to address heat, light and heat Shen admitted to optimize the design, improve optical properties, surface-mount technology to speed up the process of SMD is the industry R & D The direction of the mainstream.
Product packaging type of structure
Since the 1990s since, LED chip and materials technology R & D to achieve breakthroughs in a number of transparent trapezoidal structure of the substrate, the surface texture structure, flip-chip structure, the commercialization of ultra-high brightness (1cd more) red, orange, Yellow, green and blue LED products, one after another asked the city, as shown in table 1, 2000 in the low flux in the special application lighting gain. LED's, the middle reaches of the industry has suffered an unprecedented importance to further promote the downstream packaging technology and industrial development, different packaging structure and size, different colors of light-emitting chip and two-color or tri-color combinations that produce A series of multiple varieties, specifications of the product.
LED packaging products such as the type of structure shown in Table 2, also luminescence based on color, material chips, LED brightness, size, and other characteristics of the situation to the classification. Die in general constitute a single point source, a number of die general assembly may constitute a surface light source and light line, for information, instructions and status display, LED display is used more than die, die, through the appropriate connections (including the series and Parallel) with the right combination of the optical structure, composition of the light-emitting displays, and LED light-emitting point. Surface Mount LED may be a gradual replacement of pin-LED, more flexible application design, LED display in a certain market share of possession, to accelerate the trend. Some solid source of lighting products to market, the future of the LED, long-term development.
-Pin package
LED-pin package used for a variety of lead frame shape of the package pin, is the first R & D success to market the structure of the package, the number of species range, the higher the degree of technological maturity, package and the structure of the reflector is still Continuous improvement. LED standards by the majority of customers show that the industry is the most convenient and most economical solution, typically placed in the traditional LED can withstand input power of 0.1W encapsulation, 90% of their calories from the anode pin PCB circulated to board planes, and then distributed into the air, how to reduce the working hours of the pn junction temperature rise is packaged with the application must be considered. Encapsulation material the use of high-temperature curing epoxy resin, its optical performance, adaptive technology, products * may be high, can be made transparent colored or colorless, transparent and colorless or colored scattering scattering lens of the package, different Lens shape and form constitute a variety of sizes, for example, according to the circular diameter is divided into Φ2mm, Φ3mm, Φ4.4mm, Φ5mm, Φ7mm several species such as, the resin may have a different composition different glow. Color point light sources have a wide range of structural package: base ceramic packaging resin has good temperature performance, flexible pin into the required shape, small size; base metal reflective plastic cover is a package Energy-saving lights, suitable for power with the instructions; flicker-oscillator circuit will CMOS chip LED die and package combination, they can have a strong visual impact of the flickering light; by-two-color light-emitting two different colors of the composition of the die , In the same package of epoxy resin lens, with the exception of two-color outside can also get a third of the mixed color, large-screen display system in a wide range of applications and package composed of two-color display; to-voltage Current source LED chip and package combination die, directly substitute for 5-24V voltage range of light. Face a number of LED light source is a die pass sticky Sung Wen ⑿ CB board the provisions of the location, reflective plastic box cover and epoxy potting form, PCB board design to identify the different things arranged and lead the way to connect, double row In-line with the single in-line, and other forms of structure. , Has now developed a surface light source hundreds of package shape and size for the application of marketing and customer.
LED light-emitting display may be digital or Jack tube, pipe symbol, Chen moment control the various components of a number of products, designed by the real needs of a variety of shapes and structures. Digital control, for example, there are cover-reflection, monolithic integrated, single, three-paragraph structure of the package, there are ways to connect a total of anode and cathode of the two, is a digital pipe usually say, two or more The general called the display. Cover with a reflex-type fonts, the use of materials for the province, the assembly of hybrid and flexible packaging characteristics, which tends to be used into a white plastic reflector with shell-shaped cavity of the seventh, a single LED die bonding with the seven Reflector Reflector cavity of each bit of PCB board, each reflector cavity at the bottom of the center of the die is formed by light-emitting area, with pressure welding wire bonding method, the drop in the reflection of people inside the enclosure resin, stick with the good die PCB-binding on the board, and then click is needed for curing. Cover-reflection is subdivided into closed and the air is two letters, the former agent and scattering the use of epoxy resin dyes are used for flat, double-devices; site, which even with the filter Film and die with James on the floor in a transparent plastic insulation and improve the efficiency of the light, generally used for more than four figures. Monolithic integrated light-emitting materials in the production of chips on a large number of digital display graphics seventh die, and then dicing, and is separated into single graphics chip, bonding, bonding, with lens package (commonly known as fish-eye lens) shell . Single-paragraph would have been a good large-scale production of LED chips, Ge Cheng draw only included one or more of a core of light-emitting, so the same bonding 7 in the digital characters may be cutting the shelves, the pressure welding, epoxy Constitute a resin package. Monolithic, single-style is characterized by micro-miniaturization, can be dual in-line package, the most exclusive products. Guangzhu LED display in the line of 106mm length of the board to accommodate only 101 core (up to 201 core only), high density packaging, the use of optical refraction of principle, so that the point light sources through the transparent casing of Article 13-15 of the grating image , The completion of each core by just a point to a line of shows that packaging technology is more complex.
Semiconductor pn junction of the electroluminescent LED decision can not have a mechanism with continuous spectrum of white light, while only a single LED can not have two or more monochromatic light of high brightness, only packaging material when using fluorescence, blue or ultraviolet LED die on the phosphor coating, indirect broadband spectrum, synthetic white; or a few (two or three, multiple) made light of the different die in a package components inside the shell, through the light Constitute a mixed white LED. Both methods have made practical use in Japan in 2000 the production of white LED up to 100,000,000, to develop into a class of white hair and stable products, and more than white LED designs-assembly into flux not ask for much, so as to the role of local decoration for Lord, the pursuit of the trendy electric light source.
Surface Mount Package
In 2002, the surface mount package of LED (SMD LED) has been gradually accepted by the market and get some market share from the pin SMD package to the development of the electronics industry as a whole in line with the trend, many manufacturers of such launch Products.
Most of the early SMD LED with a transparent plastic body of the SOT-23 modified, size 3.04 × 1.11mm, Reel Tape packing containers. In the SOT-23, based on research and development of the lens with a high-brightness SMD of the SLM-125 series, SLM-245 series LED, LED monochrome for the former, the latter for the two-color or tri-color LED. In recent years, SMD LED development as a hot spot, a very good solution to the brightness and viewing angle, smoothness, *, consistency and so on, the use of lighter PCB board and reflector materials, show that in the reflector to fill the needs of Less resin, and the removal of heavy carbon steel materials pin through the narrow size, lower weight, the product can be easily half the weight at the end, the application of a more perfect, especially for indoor, outdoor and a half full Color display applications.
Thermal pad is an important channel of SMD LED manufacturers to provide data to all of the 4.0 × 4.0mm pad-based, using reflow pad can be designed with the same pin. Ultra High Brightness LED products can be PLCC (plastic chip carrier with lead) -2 package size to 3.0 × 2.8mm, the assembly adopted a unique method of high-brightness chip products for the thermal resistance of 400K / W, can be CECC by way of welding, the luminous intensity in the 50mA current drive down 1250mcd. A seventh-, two, three and four SMD LED digital display a high degree of character for the 5.08-12.7mm, show that sizes wide range of options. Pin PLCC package to avoid a seventh digital display required manual pin inserted and aligned process, in line with the automatic pick - mount production equipment requirements of the application of flexible design space, a clear bright display. Multi-color PLCC package with an external reflector can be easily and LED light or the combination of lead, with reflective replace the existing transmission-type optical design for a wide range of the region to provide uniform lighting, in the R & D 3.5V, 1A Driving under the conditions of the work of the power-SMD LED package.
Power-package
LED chip and package to the development of high-power, high current under Φ5mmLED than 10-20 times that of the large luminous flux, we must adopt effective cooling and deterioration of the packaging materials do not address the issue of bad light, and shell closure Also installed its key technologies, to be capable of sustaining a number of W-power LED package has been the emergence of. 5W series of white, green, blue and green and blue LED power-supply start from the beginning of 2003, white LED light output up to 1871m, optical effect 44.31m / W green light failure problems, develop affordable 10W power LED, big Area of control; ladle size of 2.5 × 2.5mm, in 5A under the current, light output up to 2001m, as a solid light source that has ample room.
Luxeon Power LED series is A1GalnN power flip-flip-chip soldering with solder bump on the silicon carrier, and then to complete the flip Welding of silicon carrier and heat sink into the shell, the bonding package for lead . This package to get the efficiency of light, heat dissipation and increase operating current density of the design are the best. Its main features: low thermal resistance, in general only 14 ℃ / W, only conventional LED 1 / 10; * can be high, the package filled with internal stability in the soft gel, -40-120 ℃ in the area will not be Have a sudden change of temperature due to stress, lead frame to make off with gold and yellow to prevent the epoxy resin lens, the lead frame will not tarnish and oxidation as a result; lens reflex Cup and the best design so that the radiation pattern control Optical and efficient. In addition, the output optical power, outside the quantum efficiency performance, the solid LED light source to a new level.
Norlux series of power LED package for the hexagonal structure of aluminum sheet for the base (it is not conductive) the combination of multi-chip, base diameter of 31.75mm, light-emitting area is located in the center of a diameter of about (0.375 × 25.4) mm, A capacity of 40 LED die, at the same time as the aluminum heat sink. Die bonding of the lead through the production base of the point of contact with the two is that negative connection, according to the required output power to determine the size of the base on the order of the number of die can be packaged combination of ultra-high brightness and AlGaInN AlGaInP die, the launch of monochromatic light, white color or synthetic, high-end materials, according to the refractive index of optical design for the shape of entrapment. This package using conventional die combination of high-density packaging, take-ray high efficiency, low thermal resistance, better protection of the die and wire bonding, in the current under high light output power, there is also a The solid prospects for the development of LED light source.
In the application, can be packaged products have been assembled in a sandwich with aluminum metal core PCB board to form a power density LED, PCB board as a device to connect the electrodes of wiring, thermal Lvxin dissection can make use of Shen , To obtain a higher luminous flux and made optoelectronic conversion efficiency. In addition, a good package SMD LED small size, flexibility can be combined, constitute a modular, lightguide plate-type condenser, such as reflective of the colorful lighting source.
Thermal-power LED features a direct impact on the operating temperature of the LED, light-emitting efficiency, emission wavelength, such as life, power-on LED chip packaging design, manufacturing technology, has become particularly important.
LED development and application prospects
In recent years, LED light-emitting 100 times increase in efficiency, reduced costs by 10 times, is widely used by large full-color display, the instructions state, lighting signs, signals, the LCD backlight, the combination of car and car taillight Lighting and so on, the prospects for its development to attract the world's largest lighting manufacturers have all joined the LED light source and market development. Great prospects for development and application of the white LED, solid as a lighting device of significant economic and environmental benefit, is gradually replacing traditional incandescent, the world annual growth rate in more than 20% of the United States, Japan, Europe and China Taiwan Province have launched a semiconductor lighting scheme. At present, the ordinary white LED light-emitting efficiency of the 251m / W, experts are expected in 2005 may exceed 3001m / W. Power-LED excellent thermal and optical properties can adapt to the characteristics of the area of general lighting, academia and the industry is that LED lighting into the market, the only way. Alternative to fluorescent, white LED must have 150-2001m / W light efficiency, and Im the price of each should be significantly lower than 0.015/Im (at current prices of about 0.25 $ / Im, red LED to 0.065/Im) , It is necessary to achieve this goal there are still many technical problems need to look at, but to overcome these problems is not very far away. LED by solid physics, LED light-emitting efficiency can approximate 100%, therefore, LED light source as the new 21st century, is expected to become incandescent, fluorescent, high intensity discharge lamp after the fourth-generation light sources.
