There are three elements of LED packaging technology: package structure design, selection of suitable packaging materials and process level. At present, there are more than 100 LED package structures. The main package types include more than 40 Lamp series, SMD (chip LED and TOP LED) series. More than 30 kinds, more than 30 COB series, PLCC, high power package, optical integrated package and modular package, etc., the development of packaging technology should closely follow and meet the needs of LED application product development.
The basic content of LED packaging technology
The basic requirements of LED packaging technology are: improved light extraction efficiency, high light color performance and device reliability.
(1) Improve light extraction efficiency
The light-emitting efficiency of the LED package is generally 80-90%.
1 Use a more transparent packaging material: transparency ≥ 95% (1mm thickness), refractive index greater than 1.5 and so on.
2 Select high-efficiency, high-dominance phosphors with appropriate particle size.
3 The mounting substrate (reflecting cup) should have an optical design with high reflectivity and high light extraction rate.
4 Choose the appropriate packaging process, especially the coating process.
(2) High light color performance
The main light color technical parameters of LED are: height, glare, color temperature, color rendering, color tolerance, light flicker, etc.
Color rendering index CRI ≥ 70 (outdoor), ≥ 80 (outdoor), ≥ 90 (art museum, etc.)
Color tolerance ≤3 SDCM, ≤5 SDCM (full life period)
The package should be implemented with a multi-primary color combination, focusing on improving the spectral amount distribution SPD of the LED radiation, and the spectral distribution to the sunlight is close. Pay attention to the development and application of quantum dot phosphors to achieve better light color quality.
(3) LED device reliability
LED reliability includes changes in LED device performance under various conditions and various failure mode mechanisms (degradation of LED package materials, effects of integrated stress, etc.), which is mainly referred to as the characterization value of reliability - lifetime, currently LED device life is generally 3 to 5 hours, up to 50,000 to 100,000 hours.
1 Use suitable packaging materials: large bonding force, small stress, good matching, good air tightness, temperature resistance, moisture resistance (low water absorption), anti-ultraviolet light, etc.
2 package heat-dissipating materials: high thermal conductivity and high conductivity of the substrate, high thermal conductivity, high electrical conductivity and high strength of the solid crystal material, the stress is small.
3 suitable packaging process: loading, pressure welding, packaging and other bonding strength, stress should be small, the combination should be matched.
LED light integrated packaging technology
There are more than 30 types of LED light integrated package structures, which are gradually moving toward system integration and packaging, which is the development direction of future packaging technology.
(1) COB integrated package
The COB integrated package has more than 30 kinds of package structures such as MCOB, COMB, MOFB and MLCOB. The COB packaging technology is becoming more and more mature, and its advantage is low cost. COB package now accounts for about 40% of LED light source market, light efficiency of 160~178 lm/w, thermal resistance up to 2 °C/w, COB package is the trend of recent LED package development.
(2) LED crystal garden grade package
The crystal-scale package is made of epitaxial LED devices. Once dicing, it is a multi-system integrated package for LED illumination sources. The general substrate is made of silicon material, which does not require die bonding and pressure bonding, and is formed by dispensing to form a system integrated package. The advantage is that the reliability is good and the cost is low, which is one of the development directions of the packaging technology.
(3) COF integrated package
The COF integrated package is a large-area assembled medium-power LED chip on a flexible substrate. It has the advantages of high thermal conductivity, thin layer flexibility, low cost, uniform light emission, high light efficiency, and flexible surface light source, and can provide line light source, surface light source and The various LED products of the three-dimensional light source can also meet the requirements of LED modern lighting and personalized lighting, and can also be used as a general-purpose package component, and the market prospect is promising.
(4) LED modular integrated package
Modular integrated package generally refers to system integration and packaging of LED chip, driving power supply, control part (including IP address), parts, etc., collectively referred to as LED module, which has many advantages such as saving materials, reducing cost, standardizing production, and convenient maintenance. Is the direction of LED packaging technology development.
(5) flip chip packaging technology
The flip chip packaging technology forms a space from the chip, the substrate and the bump, so that the packaged chip has the advantages of small volume, high performance, short connection, etc., using ceramic substrate, flip chip, eutectic process, direct pressure Meet to achieve high power lighting performance requirements. The chip is pressed onto the substrate with a gold-tin alloy to replace the conventional silver glue process, and the "direct press-fit" replaces the "reflow soldering" in the past, and has excellent electrical conductivity and heat-conducting area. This packaging technology is an important development trend of high-power LED packaging.
Definition and Basic Characteristics
The Parabolic Dish Antenna, shaped like a parabola, is inspired by the principle of parabolic reflectors in optics. This antenna focuses radio waves onto a single point through its parabolic reflector, thereby enhancing signal strength and directionality. Parabolic Dish Antennas are widely used in microwave communications, satellite communications, radio telescopes, and radar systems.
Classification Criteria
Parabolic Dish Antennas can be classified based on their purpose, size, frequency range, and design characteristics.
Classification by Purpose:
Microwave Communication Antennas: Used for microwave relay links, enabling telephone, television signals, and wireless WAN/LAN data communication between cities.
Satellite Communication Antennas: Part of satellite ground stations, used to receive and transmit satellite signals.
Radio Telescope Antennas: Employed in astronomical observations, collecting faint radio waves from deep space.
Radar Antennas: Utilized for detecting and locating ships, aircraft, missiles, and other targets.
Classification by Size:
Depending on the diameter of the parabolic reflector, Parabolic Dish Antennas can be categorized as small, medium, and large. Small antennas are suitable for households or small base stations, while large ones are commonly found in satellite communication stations and radar systems.
Classification by Frequency Range:
Parabolic Dish Antennas can be designed to cover different frequency ranges, such as UHF (Ultra-High Frequency) and SHF (Super-High Frequency), to meet various communication needs.
Classification by Design Characteristics:
Cassegrain Antennas: Designed to eliminate the blockage and reflection of radio waves by the sub-reflector, enhancing antenna efficiency.
Offset Antennas (e.g., Offset Gregorian Antennas): Optimize antenna performance by altering the position relationship between the feed and the reflector.
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