LED package of more than 100 kinds of structural differences Daquan
LED packaging technology has three elements: packaging structure design, selection of appropriate packaging materials and process level.
At present, there are more than 100 types of LED package structure. The main package types include more than 40 kinds of Lamp series, over 30 kinds of SMD (chip LED and TOP LED) series, over 30 kinds of COB series, PLCC, high power package, optical integrated package Modular package, the development of packaging technology to keep up with and meet the needs of the development of LED applications.
LED packaging technology, the basic content
LED packaging technology, the basic requirements are: to improve the light efficiency, high light color performance and device reliability.
(1) improve the light efficiency
LED package light output efficiency generally up to 80 ~ 90%.
① choose a better transparency of the packaging materials: transparency ≥ 95% (1mm thickness), refractive index greater than 1.5 and so on.
② use high excitation efficiency, high dominant phosphor, particle size appropriate.
③ mounted substrate (reflector) to have high reflectivity, high optical output optical design shape.
④ select the appropriate packaging technology, especially the coating process.
(2) high light color performance
LED main light color technical parameters are: height, glare, color temperature, color, color tolerance, light flicker.
Color rendering index CRI ≥ 70 (outdoor), ≥ 80 (outdoor), ≥ 90 (Museum of Art, etc.).
Color tolerance ≤ 3 SDCM ≤ 5 SDCM (during life)
Package to be used to achieve multi-color combinations, focusing on improving the LED radiation spectral distribution SPD, to the spectral distribution of sunlight near. We must pay attention to the development and application of quantum dot phosphors to achieve better light color quality.
(3) LED device reliability
LED reliability includes LED device performance under different conditions and a variety of failure mode mechanism (LED packaging material degradation, the impact of comprehensive stress, etc.), which is mainly referred to the reliability of the characterization value - life expectancy, the current LED device life is generally 3 to 5 hours, up to 5 to 100,000 hours.
① select the appropriate packaging materials: bonding force should be large, small stress, good matching, good air tightness, temperature, moisture (low water absorption), anti-UV and so on.
② package cooling material: high thermal conductivity and high conductivity substrate, high thermal conductivity, high conductivity and high strength of the solid crystal material, the stress should be small.
③ the appropriate packaging process: Loading films, pressure welding, packaging and other strong bonding, stress should be small, with the match.
LED integrated optical packaging technology
There are more than 30 kinds of LED light integrated package structure, is gradually moving toward system integrated package, is the future direction of the development of packaging technology.
(1) COB integrated package
COB integrated package existing MCOB, COMB, MOFB, MLCOB more than 30 kinds of package structure, COB packaging technology matures, the advantage of low cost. COB package now accounts for about 40% of LED light market, light efficiency of 160 ~ 178 lm / w, thermal resistance up to 2 ℃ / w, COB package is the recent development trend of LED packaging.
(2) LED crystal-level package
Epistar package made from the epitaxial LED devices as long as a dicing, LED lighting source is the demand for multi-system integrated package, the general substrate using silicon material, without the need for solid crystal and pressure welding, and dispensing forming a system integrated package , Which has the advantages of good reliability and low cost, and is one of the development directions of the packaging technology.
(3) COF integrated package
COF integrated package is a large area assembly of medium power LED chip on a flexible substrate. It has the advantages of high thermal conductivity, thin flexible layer, low cost, uniform light, high luminous efficiency, flexible surface light source, etc. It can provide linear light source, surface light source and Three-dimensional light source of various LED products, LED lighting can also meet the modern, personalized lighting requirements, but also as a universal package components, the market prospects.
(4) LED modular integrated package
Modular integrated package generally refers to the LED chip, drive power, control part (including IP address), parts and other system integration package, collectively referred to as LED module, with the material saving, reduce costs, standardization of production, easy maintenance and many other advantages , LED packaging technology is the direction of development.
(5) flip chip packaging technology
Flip-chip packaging technology is a chip, substrate, bump to form a space, so packaged chips with small size, high performance, short connection and other advantages, the use of ceramic substrates, flip chip, eutectic process, direct pressure Equal to meet the high-power lighting performance requirements.
With gold-tin alloy chip laminated on the substrate, instead of the previous silver plastic process, "direct compression" to replace the past, "reflow", with excellent conductive effect and thermal area. The packaging technology is an important development trend of high-power LED package.
(6) Free packaging chip technology
Packaging-free technology is a technology integration, the use of flip chip, without a solid crystal, gold wire and bracket is a semiconductor packaging technology, 70 kinds of technology in one.
PFC chip-free packaging products can be increased to 200lm / w, ultra-wide angle lighting design of more than 300 degrees, do not use secondary optical lens will reduce the loss of light efficiency and reduce costs, but to invest in expensive equipment.
PFC new product main LED lighting market, especially used in the candle light, not only can simulate the shape of tungsten lamp, while breaking the thermal volume limit.
(7) LED Other package structure
①EMC package structure: embedded integrated package (Embedded LED Chip) will not directly see the LED light source.
②EMC packaging technology: (Epoxy Molding Compound) Epoxy plastic encapsulation material for the stent packaging technology, with high heat resistance, high integration, anti-UV, small size, etc., but less air tightness, is now mass production.
③ COG package: (Chip On Glass) LED chips on the glass substrate for packaging.
④ QFN packaging technology: small pitch display pixel unit is less than or equal to P.1, the package used in place of PLCC structure, the market prospects.
⑤ 3D Packaging Technology: Three-dimensional form of packaging technology, is being developed.
⑥ Power-frame packaging technology: (Chip-in-Frame Package) Encapsulates the power LED chip in the small frame, the industrialized light efficiency has reached 160 ~ 170 lm / w, up to 200 lm / w above.
LED packaging materials
LED packaging materials variety, and is constantly evolving, here is a brief introduction.
(1) packaging materials
Epoxy resin, epoxy plastic material, silicone, silicone plastic, technically on the refractive index, internal stress, bonding, air tightness, high temperature, UV resistance and other requirements.
(2) solid crystal material
① solid crystal glue: resins and silicone type, the internal filling of metal and ceramic materials.
② eutectic: AuSn, SnAg / SnAgCu.
(3) substrate material: copper, aluminum and other metal alloy materials
① ceramic materials: Al2O3, AlN, SiC and so on.
② aluminum ceramic materials: known as the third generation packaging materials AlSiC, AlSi and so on.
③ SCB substrate material: multi-layer die substrate, good heat dissipation (thermal conductivity 380w / m.k), low cost.
④ TES polycrystalline semiconductor ceramic substrate, heat transfer speed.
(4) cooling material: copper, aluminum and other metal alloy materials
Graphene composite materials, thermal conductivity 200 ~ 1500w / m.k.
PCT high temperature special engineering plastics (poly 1,4-cyclohexane dimethyl terephthalate), plus ceramic fiber, high temperature, low water absorption.
Thermal Engineering Plastics: Non-insulated thermal engineering plastics, thermal conductivity 14w / m.k.
Insulating thermal engineering plastics, thermal conductivity 8w / m.k.