LED guardrail lamp diode package structure and technology

3 Product package structure type

Since the 1990s, LED chip and material fabrication technology has made many breakthroughs in research and development, transparent substrate trapezoidal structure, textured surface structure, chip flip structure, commercial ultra-high brightness (above 1cd) red, orange, Yellow, green, and blue LED products have been asked one after another. As shown in Table 1, in 2000, applications in low- and medium-light flux special lighting were applied. The upper and middle reaches of LED industry have received unprecedented attention, further promoting the downstream packaging technology and industrial development. Different types of package structures and sizes, different luminescent color dies and their two-color or three-color combination can produce a variety of Series, variety, specifications of the product.

The types of LED product package structures are shown in Table 2, and are also classified according to the characteristics of the color of the light, the material of the chip, the brightness of the light, the size, and the like. A single die generally constitutes a point source, and a plurality of die assemblies generally constitute a surface source and a line source for information, status indication, and display. The illuminating display also uses a plurality of dies, through appropriate connections of the dies (including series and Parallel) combined with a suitable optical structure to form the illumination segment and the illumination point of the illuminated display. Surface mount LEDs can gradually replace pin-type LEDs, and the application design is more flexible. It has occupied a certain share in the LED display market and has an accelerated development trend. Some solid-state lighting sources have been launched, which will become the medium and long-term development direction of LEDs in the future.

4-pin package

The LED foot package uses lead frames as pins for various package types. It is the first package structure successfully developed on the market. The variety of products is high, the technology maturity is high, and the structure and reflective layer inside the package are still being improved. Standard LEDs are considered by most customers to be the most convenient and economical solution in the display industry. Typical LEDs are housed in an enclosure that can withstand 0.1W of input power, 90% of which is pinned by the negative pole. The rack is distributed to the PCB and then released into the air. How to reduce the temperature rise of the pn junction during operation is a must for packaging and application. The encapsulating material is mostly made of high-temperature curing epoxy resin, which has excellent optical properties, good process adaptability, high product reliability, and can be made into a transparent or colorless transparent and colored scattering or colorless lens package, different lens shapes. A variety of shapes and sizes are formed. For example, the circular shape is divided into several types according to the diameter: Φ2 mm, Φ3 mm, Φ4.4 mm, Φ5 mm, Φ7 mm, etc., and different components of the epoxy resin can produce different illuminating effects. The color point light source has a variety of different package structures: the ceramic base epoxy resin package has better working temperature performance, the lead can be bent into a desired shape, and the volume is small; the metal base plastic reflective cover type package is an energy-saving indicator light. Suitable for power indication; flashing CMOS oscillating circuit chip and LED die package, can produce self-generated flashing light with strong visual impact; two-color type consists of two different luminescent color dies, packaged in the same epoxy In the resin lens, a third mixed color can be obtained in addition to the two colors, which is widely used in a large-screen display system, and can be packaged to form a two-color display device; the voltage type is a combination of a constant current source chip and an LED die. Can directly replace the various voltage indicators of 5-24V. The surface light source is formed by bonding a plurality of LED dies to a predetermined position of the micro PCB board, and is formed by using a plastic reflective frame cover and potting the epoxy resin. The different designs of the PCB board determine the arrangement and connection manner of the outer leads, and the double row is straight. Insert and single-row inline and other structural forms. Point and surface light sources have been developed in hundreds of package shapes and sizes for the market and customers.

The LED light-emitting display can be composed of a digital tube or a meter tube, a symbol tube, and a rectangular tube to form various products, and is designed into various shapes and structures according to actual needs. Take the digital tube as an example, there are three kinds of package structures, such as a reflector cover, a single-chip integrated type, and a single seven-segment type. The connection mode includes a common anode and a common cathode. One is a commonly known digital tube, and two or more. Generally referred to as a display. The reflector type has the characteristics of large font, material saving, and flexible assembly. It is generally made of white plastic into a seven-section housing with a reflective cavity, and a single LED die is bonded to the seven reflective chambers of the reflector. On the PCB board that is aligned with each other, the center position of the bottom of each reflection cavity is the light-emitting area formed by the die, and the lead wire is bonded by a pressure welding method, and the epoxy resin is dropped in the reflection cover, and the PCB board of the die is bonded. Bonded in place and then cured. Reflective cover type is divided into air seal and solid seal. The former uses epoxy resin with scattering agent and dye, and is mostly used for unit and double-position devices; the latter is covered with color filter and uniform film, and is in the die and The bottom plate is coated with transparent insulating glue to improve the light-emitting efficiency, and is generally used for digital display of four or more digits. The monolithic integrated method is to fabricate a large number of seven-segment digital display graphic dies on a luminescent material wafer, and then dicing into a single-patterned dicing die, bonding, pressure-welding, and encapsulating a lens with a lens (commonly known as a fisheye lens). A single seven-segment type of large-area LED chip that has been fabricated into a light-emitting strip containing one or more dies, so that the same seven pieces are bonded to the digital-shaped slash frame, and are pressure-welded and epoxy. Resin package construction. The monolithic and single strip features are miniaturized and can be used in dual in-line packages, mostly for specialty products. The LED light column display houses 101 dies (up to 201 dies) on a 106mm length circuit board. It is a high-density package that uses optical refraction principles to image the point source through 13-15 strips of transparent cover. The dot-to-line display of each die is completed, and the packaging technology is more complicated.

The electroluminescence mechanism of the semiconductor pn junction determines that it is impossible for LED to produce white light with continuous spectrum. At the same time, it is impossible for a single LED to produce more than two kinds of high-brightness monochromatic light. It can only be used for packaging with fluorescent substances, blue or ultraviolet LEDs. The phosphor is coated on the die to indirectly generate a broadband spectrum, and the white light is synthesized; or a plurality of (two or three or more) dice of different color lights are packaged in one component casing, and the white LED is formed by mixing the color lights. . Both methods have been put into practical use. In 2000, Japan produced 100 million white LEDs, which developed into a class of products that stably emit white light. The design of multiple white LEDs was not required to meet the luminous flux requirements. Lord, the pursuit of a new electric light source.

5 surface mount package

In 2002, surface mount packaged LEDs (SMD LEDs) were gradually accepted by the market and gained a certain market share. From lead package to SMD, it conformed to the development trend of the whole electronics industry, and many manufacturers introduced such products.

Most of the early SMD LEDs were modified with SOT-23 with a transparent plastic body. The outer dimensions were 3.04×1.11mm, and the reel-type container was taped. Based on SOT-23, the SLM-125 series with high-brightness SMD with lens and SLM-245 series LED are developed. The former is monochromatic illumination, and the latter is two-color or three-color illumination. In recent years, SMD LED has become a development hotspot, which solves the problems of brightness, viewing angle, flatness, reliability, consistency, etc., using a lighter PCB board and reflective layer material to display the ring that needs to be filled in the reflective layer. Less oxygen resin, and remove the heavier carbon steel material pins, can reduce the weight of the product by half, reduce the weight of the product, and finally make the application more perfect, especially suitable for indoor, semi-outdoor full color display application.