Led Package Structure And Technology Development
Under normal circumstances, core was sealed in the package body for discrete devices
, role is to preserve the core of the package and complete the electrical interconnection. LED package is the complete output signal, protect the core function, output: visible feature, existing electrical parameters and design of optical parameters and technical requirements, not simply the discrete device package for LED.
Core luminous part of LED large screen is made of p-type and n-type semiconductor pn junction core, when injected minority carriers and the majority of the pn junction when carrier composite, emits visible light, ultraviolet light, or near-infrared light. Photon is given orientation of the pn junction area, the chance to launch the same in all directions, so, not all of the core can be released, this mainly depends on the quality of semiconductor materials, core structure and geometrical shape, packaging, internal structure and encapsulation materials, increasing internal and external quantum efficiency of the LED. General-5mm LED package is a square of side length 0.25mm or sintered core bond on the lead frame, tube cores positive spherical contact point and gold wire, bonding as a leader and a PIN connected to the anode Cup through reflection and lead frame connected to another pin, and then top it with epoxy resin encapsulation.
Reflective glass collection tube side of the core, is the role of light emitted by the interface, to launch to the desired angle. Top Department package seal of epoxy resin made must shape, has so several role: protection tube core, does not by outside erosion; used different of shape and material nature (mixed with or does not mixed with bulk color agent), up lens or diffuse lens function, control light of divergent angle; tube core refraction rate and air refraction rate related too large, cause tube core internal of full reflection critical angle is small, its has source layer produced of light only fraction is out, most easy in tube core internal by times reflection and is absorption, easy occurs full reflection led to too much light loss, Choose the corresponding refractive index of epoxy resin for transition, improving the efficiency of light shot out of the core. Used as a form of shell-and-tube epoxy resins with moisture, insulation, mechanical strength, core refractive index of light and high transmission rates.
However, the LED's light output will increase over current increases, at present, many power-LED drive current up to 70mA, 100mA or 1 a level, need to improve the package structure, LED packaging design concept and low thermal resistance of the new package structure and technology, improved heat transfer characteristics. For example, with a large chip was at the bottom, use good thermal conductivity of silver colloid, increases the surface area of the metal bracket, solder bump directly mounted on heat sink Silicon carrier choice. In addition, application design, PCB circuit boards, thermal design, thermal conductivity is also very important. After entering the 21st century, high efficiency and ultra-high brightness LED, full color continuous development of innovative, LED luminous efficiency had reached 100Im/W with red, Orange, green LED for 501m/W, single LED luminous flux reached dozens of Im.
LED chip and package is no longer along Gong traditional of design concept and manufacturing production mode, in increased chip of light output area, development not only limited to change material within impurities number, lattice defects and bit wrong to improve internal efficiency, while, how improve tube core and the package internal structure, enhanced LED internal produced photon out shot of chances, improve light effect, solution thermal, take light and hot sinking optimization design, improved optical performance, accelerated surface posted loaded of SMD process more is industry development of mainstream direction.
Products package structure type since Shang century 90 generation yilai, LED chip and the material making technology of development made more items breakthrough, transparent lined end ladder structure, and texture surface structure, and chip flip structure, commercialization of super high brightness (1cd above) red, and orange, and yellow, and green, and blue of LED products have asked city, as table 1 by shows, 2000 began in low, and in the flux of special lighting in the get application. LED on the upper and middle reaches of industry received unprecedented attention and further promote the development of downstream packaging technology and industry, with different package structure and size, different core of luminous color and two-color, or color combinations, can produce a variety of series, varieties, specifications of the product.
LED package structure types, depending on the light color, chip material, glow, brightness, size, and other characteristics to classify. Single core generally constitute a point light source, multiple core Assembly generally constitute a light source and source, used for indicating and display information, State, light emitting display with more than one core, through the core of the appropriate connection (including serial and parallel) with the right combination of optical structure, constitute a luminous glow and glow of the monitor. Surface mount LED to the gradual replacement of pin LED, application design flexibility, hold certain shares in the LED display market, accelerate the trend.
Standard LED display industry by most customers that are current in the most convenient and the most economical solution, typical of the traditional LED placement can take 0. 1W power envelope, its heat is from anode pin of 90% distributed to the PCB Board, and then distributed to air, how to reduce working time of pn junction temperature is the application package and must be taken into account. High-temperature curing epoxy resin encapsulation materials used, their excellent optical properties, good adaptability technology, product reliability, can be colored or colorless transparent or colorless and colored scattering scattering lens package, different lens shapes of various shapes and sizes, for example, the circle diameter divided into 2mm, 3mm, PHI 4. 4mm, 5mm, 7mm and other species, epoxy resin of different groups can have different luminous effect.
Suit points light has multiple different of package structure: ceramic base epoxy resin package has better of work temperature performance, introduction feet can bent into by needed shape, volume small; metal base plastic reflection cover type package is a energy saving led, suitable for power indicates with; Flash type will CMOS oscillation circuit chip and LED tube core combination package, can themselves produced strong visual impact of flash light; double color type by two species different glow color of tube core composition, package in same epoxy resin lens in the, Apart from the two-color also may obtain a third mixed color, has wide application in large-screen display systems, and package composed of dual-color displays; voltage constant current source chip combined with the LED tube-core package, direct voltage led alternative to 5-24V.
Surface light source is more than one LED tube core bonding in micro-PCB Board provided on location, using plastic reflection frame and encapsulating epoxy resin formation, arranged in different design of PCB Board leads and connections, dual in-line with the single in-line structure. Point, surface light source has developed hundreds of kinds of package shapes and dimensions, for market and customer application.
LED light emitting display by digital or meter tubes, with these symbols pipe, rectangular tubes that make up the various product, design by actual needs into a variety of shapes and structures. Digital tube, for example, the reflector type, single-chip integration, single seven-segment three packaging structures such as, connection with common anode and cathode in two kinds, one is usually said digital, generally known as the monitor of the two above.
by: billy
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