Elements LED packaging technology are threefold: package design, selection of suitable packaging materials and craftsmanship.
Currently LED packaging structure in the form of 100 kinds, the main package types Lamp series of 40, SMD (chip LED and TOP LED) series over 30 kinds, COB series over 30 kinds, PLCC, power package, light and integrated package modular packaging, etc., the development of packaging technology to keep up with and meet the needs of LED application product development.
The basic contents of LED packaging technology
The basic requirements for LED packaging technology are: to improve light efficiency, high color performance and device reliability.
(1) improve the light efficiency
The optical efficiency of the LED package generally up to 80 to 90%.
① selection of transparency and better packaging materials: Transparency ≥95% (1mm thickness), a refractive index greater than 1.5 and so on.
② selection of high excitation efficiency, high dominant phosphor particle size appropriate.
③ loading substrate (reflector cup) have a high reflectivity, a light high optical design shape.
④ appropriate choice of packaging technology, in particular coating process.
(2) high performance light color
LED light color main technical parameters are: height, glare, color temperature, color, color tolerance, light flicker.
CRI CRI≥70 (outdoor), ≥80 (outdoor), ≥90 (art museum).
Color tolerance ≤3 SDCM≤5 SDCM (whole life period)
The amount of spectrum to be used on the package more color combination to achieve, focus on improving LED radiation distribution SPD, the spectral distribution of the amount of sunlight near. To attach importance to the development and application of fluorescent quantum dots to achieve a better quality of light and color.
(3) LED device reliability
LED reliability under different conditions contained in the LED device performance variation mechanism and failure modes (LED encapsulating material degradation, combined stresses, etc.), which is the main reference characterization value reliability - life, life is generally present LED device 3 to 5 hours, up to 5 to 10 million hours.
① appropriate choice of packaging materials: binding to large and small stress, a good match, good air tightness, temperature, humidity (low water absorption), anti-ultraviolet light.
② package thermal material: a substrate of high thermal conductivity and high electrical conductivity, high thermal conductivity, high strength and high electrical conductivity of solid crystal materials, stress is smaller.
③ suitable packaging process: loading, bonding, packaging and so on with strong, stress should be small, combine to match.
LED light integrated packaging technology
LED light integrated packaging structure of the existing more than 30 types, we are moving towards a systems integration package, the future direction of development of packaging technology.
(1) COB integrated package
COB integrated package existing MCOB, 30 variety of packages structure COMB, MOFB, MLCOB etc, COB packaging technology matures, the advantage of low cost. COB LED light source packaging now accounts for about 40% of the market, luminous efficiency of 160 ~ 178 lm / w, the thermal resistance of up to 2 ℃ / w, COB LED package package is the recent trend of development.
(2) LED Wafer Level Packaging
Wafer level packaging made from the epitaxial LED device as long as a scribe, is a multi-system integration package LED lighting needs, generally silicon substrate material without solid crystal and pressure welding, dispensing and shaping, forming system integrated package , the advantage of good reliability, low cost, is one of the packaging technology development direction.
(3) COF integrated package
COF integrated package is on a flexible substrate, a large area of the assembly power LED chip, which has the advantages of high thermal conductivity, a thin layer of flexible, low cost, light uniformity, high luminous efficiency, flexible surface light source, can provide the source line, surface light source and three-dimensional LED light source of a variety of products, but also to meet the modern LED lighting, personal lighting requirements, but also can be used as general-purpose package assembly, the market prospect.
(4) LED modular integrated package
Generally refers to a modular integrated package LED chips, power supply, the control section (including IP address), and other system components integrated package, referred to as LED module with material savings, lower cost, standardized production and maintain many advantages convenient It is the direction of LED packaging technology development.
(5) flip-chip packaging technology
Flip Chip technology was developed by the chip, the substrate, the bump forming a space, so that the package out of the chip has a small size, high performance, short connections, etc., ceramic substrates, flip-chip, eutectic processes, direct compression together to achieve high power lighting and other performance requirements.
Gold tin alloy chip laminated on a substrate, a plastic alternative to conventional silver technology "directly laminated" alternative past "reflow", with excellent electrical performance and heat transfer area. The high-power LED packaging technology is an important packaging trends.
(6) Free chip packaging technology
Free packaging technology is the integration of a technology, flip-chip, solid crystal without glue, gold wire and bracket are 70 kinds of semiconductor packaging technology in the process of forming one.
PFC-free packaged chip products can improve light efficiency to 200lm / w, light angle greater than 300 degrees ultra-wide-angle optical design of the whole week, do not use the secondary optical lens, the optical efficiency will reduce consumption and reduce costs, but to put expensive equipment.
PFC LED lighting new products hit the market, in particular the application of candle lights on, not only can simulate the shape of incandescent light, and can break through the restrictions heat volume.
(7) LED other package structures
①EMC package structure: embedded integrated package (Embedded LED Chip) does not directly see the LED light source.
②EMC packaging technology: (Epoxy Molding Compound) with epoxy molding compound scaffold packaging technology, with high heat resistance, high integration, anti-UV, small size, etc., but the tightness badly, now in volume production.
③COG Package: (Chip On Glass) LED chips on the glass substrate package.
④QFN packaging technology: When the small spacing display pixel unit is less than or equal to P.1, package adopted, will replace PLCC structure, market prospects.
⑤3D packaging technology: in the form of three-dimensional packaging technology, is being developed.
⑥ power packaging technology framework: (Chip-in-Frame Package) packaged in a small frame-power LED chips, light industrial efficiency has reached 160 ~ 170 lm / w, up to 200 lm / w or more.
LED packaging materials
LED packaging materials many varieties, and are constantly developing, here only briefly.
(1) packaging materials
Epoxy resins, epoxy molding compound, silicone, silicone plastics, technically refractive index, internal stress, adhesion strength, air tightness, high temperature, UV and other required.
(2) solid crystal material
① solid crystal plastic: resins and silicone type, internal filler metal and ceramic materials.
② eutectic: AuSn, SnAg / SnAgCu.
(3) board material: copper, aluminum and other metal alloys
① ceramic materials: Al2O3, AlN, SiC and the like.
② aluminum-based ceramic materials: referred to as the third generation of packaging materials AlSiC, AlSi like.
③SCB board material: multi-layer stamper substrate, heat (thermal conductivity 380w / m.k), and low cost.
④TES polycrystalline semiconductor ceramic substrate, heat and speed.
(4) heat sink material: copper, aluminum and other metal alloys
Graphene composites, thermal conductivity 200 ~ 1500w / m.k.
PCT special high-temperature plastic (polyethylene terephthalate, 1,4-cyclohexane dimethyl ester), plus ceramic fiber, high temperature, low water absorption.
Thermal engineering plastics: Non-isolated thermal plastic, thermal conductivity of 14w / m.k.
Insulated thermal plastic, thermal conductivity 8w / m.k.
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