As we all known that in LED lighting packaging Industry, there are some generations of led lights packaging by the human people’s high development in research of led lighting.These generations technologies of led light chips are widely used and applicated in commercial shop lights like led tube lights, led bulbs, led strips, led high bay etc. Today, we are discussing the some generations of led chips packaging one by one as below:
DIP -> SMD -> COB -> MCOB -> TCOB -> CSP -> …
In the generation birth pciture, we can see clearly that there are six right now are applicated in led lights.
CSP TECHNOLOGY – What is the LED flip-chip without gold-level package?(What is CSP technology?)
– Answer: Speaking of the technology of flip-chip without gold-level packaging, it is in the traditional LED chip package, based on the reduction of the gold wire packaging process, eliminating the wire frame, playing line, leaving only the chip with the use of phosphor and encapsulated plastic . As a new packaging technology products, flip-chip gold-free chip-level light source is not due to gold wire solder joint or poor contact caused by non-bright, flashing, light fades and other issues. Compared to the traditional packaging process, chip-level light source packaging density increased by 16 times, the package size is reduced by 80%, lamp design space. Flip-chip without gold with more stable performance, better heat dissipation, more uniform light color distribution, smaller size, more and more LED lighting enterprises and end-product applications business of all ages. LED flip chip popularity of the difficulties:
1, flip-chip LED technology is currently in the high-power products and the advantages of integrated packaging greater in the application of small and medium power, the cost competitiveness is not very strong.
2, flip-chip LED subversion of the traditional process, from the chip until the package, this will require higher equipment, took the package said, can do flip-chip front-end equipment costs will increase a lot, which set the Threshold, so that some companies simply can not come into contact with this technology.
– The Analysis of LED flip – chip technology and process(The CSP packaging explainations and process details)
Light-emitting diode (LED) as a new type of green lighting, energy saving, high efficiency, low carbon, small size, fast response, strong seismic, etc., can provide users with environmental protection, stability, efficiency and safety of new lighting experience, has gradually Developed into a
mature semiconductor lighting industry.
In recent years, countries around the world have started to disable incandescent bulbs, LED will usher in a golden period of growth. In addition, in recent years, LED backlighting in the TV, mobile phones, and tablet PCs and other applications also ushered in the explosive growth of LED has a broad application prospects.
2, flip-chip LED technology development and status
Flip-chip technology in the field of LED or a relatively new technology concept, but in the traditional IC industry has been widely used and more mature, such as a variety of ball grid array package (BGA), chip size package (CSP), chip-level chip Size packaging (WLCSP) technology, all using flip chip technology, its advantages are high production efficiency, low cost and high reliability devices.
Flip chip technology used in LED devices, the main difference is that the IC is in the LED chip manufacturing and packaging process, in addition to handling a stable and reliable electrical connections, the need to deal with the issue of light, including how to make more light Out, to improve the light efficiency, and the distribution of light space.
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In 1998, JJWierer, who prepared a 1W flip-chip structure of the large flip-chip structure of the large-scale, low-cost, high reliability, Power
AlGaInN-LED blue chip, they will be the metal bump AIGalnN chip flip-chip welding with anti-static protection diodes (ESD) on the silicon carrier. Figure 1 is a picture of the LED chip and a schematic cross-sectional view. Their test results show that the flip-chip LED (FCLED) has a larger light-emitting area and very good electrical characteristics at the same chip area. In the current range of 200-1000mA, the forward voltage (VF) Is relatively low, resulting in a higher power conversion efficiency.
In 2006, O.B.Schechekin et al. Reported a novel flip-chip multi-quantum-well structure (TFFC-LED) for flip-chip bonding. The so-called film flip LED, LED film is the concept of flip-chip LED combined.
After the LED is flip-flop onto the substrate, the sapphire substrate is stripped off using a laser lift-off technique and then roughened by photolithography on the exposed N-type GaN layer.
As shown in Figure 2, this thin-film structure of the LED can effectively increase the light efficiency. But relatively speaking, this structure process is more complex, the cost will be relatively high.
With the silicon-based flip chip sold in the market, gradually found that flip-chip LED chip in the competition with the dress, the cost is at a distinct disadvantage.
As the early stage of LED development, all packages and forms are based on its vertical or vertical structure of the LED chip design, the flip-chip LED chip had to flip on the silicon substrate, and then the chip fixed in the traditional bracket, and then The electrodes on the silicon substrate are connected to electrodes on the holder by gold wires.
Making the package there is a gold wire device exists, there is no advantage of the flip-chip package without gold; but also increased the cost of the substrate, making the price higher, did not play a flip chip LED chip advantage.
To this end, the first in 2007, the company launched a ceramic-based flip-chip LED packaging products. This type of product, both as a flip-chip ceramic substrate support, but also as a whole package stand, to achieve the whole package of light source miniaturization.
This package is the first flip-chip bonding (Bonding) in the ceramic substrate, and then the phosphor coating, and finally with the mold (Molding) method of making a lens, this method will LED chip and packaging process together , Reducing costs.
This structure completely eliminates the gold line, while the cooling effect is significantly improved, typical thermal resistance <10 ℃ / W,
significantly lower than the traditional K2 form of packaging (typical 10-20 ℃ / W).
With the further application of flip-chip technology and development of the beginning of 2012, there can be direct mount (Direct Attach, DA) flip chip; the next few years, companies have begun to develop and launch this type of flip chip.
The change in the structure of the chip, the LED chip surface P, N two metal pad geometry larger, while ensuring the distance between the two pads enough, so that flip-chip LED chip in the ceramic substrate Even on the PCB board directly to the chip, so that 40mil flip chip pad size to reach the
placement machine chip precision requirements, simplifying the flip chip welding process, reducing the overall cost.
Up to now (in 2014) flip-chip DA chip has been basically mature, the market gradually increased sales, the future will become the mainstream of high-power LED chips.
In the direct placement of the DA chip, based on the beginning of 2013 to develop a white chip (part of the company called the package or no package) products, as shown in Figure 6. It is in the flip-chip DA chip manufacturing process at the same time complete the phosphor coating, the application can be directly on the PCB patch, can be used directly as a package light source.
The advantage of LED devices is small, the chip directly to the chip can reduce the thermal interface, further reducing the thermal resistance, thermal performance to further improve. So far, white chip is still in the research and development stage, the market application is not mature, we need to work together to promote white chip technology and application development.
3, flip chip LED
LED chip manufacturing process, as shown in Figure 4, the whole can be divided into LED chip manufacturing and substrate manufacturing two lines, chip and substrate manufacturing is completed, the LED chip flip welding on the substrate surface, the formation of inverted Install LED chip.
3.1, sapphire substrate and GaN epitaxial process technology
For the flip-chip, the smooth side of the sapphire, so before the epitaxy, the production of graphics substrate (PSS), will be conducive to the blue light to reduce the light in the GaN and sapphire interface reflection. So the PSS graphics size, shape and depth of the light efficiency and so have a direct impact. In the actual development and production of flip-chip needs for the characteristics of the substrate graphics to optimize the use of the highest light efficiency.
In the GaN epitaxy, because the flip-chip on the sapphire side of the light, the absorption of each layer and the difference between the mounted chip, so the need for epitaxial buffer layer (Buffer), N-GaN layer, MQW (MQW) And the thickness and doping concentration of the p-type GaN layer are adjusted so as to be suitable for the light-emitting requirements of the flip-chip and to improve the light extraction efficiency while being suitable for the ohmic contact of the flip chip manufacturing process.
3.2, flip-chip LED wafer process technology
Flip chip and the chip is almost the same as the production process, need to be etched on the epitaxial layer to expose the underlying N-type GaN; and then in the P and N were made on the ohmic contact electrode, and then the chip surface Passivation of the protective layer, and finally the production of metal welding pad, the production process shown in Figure 5.
Compared with the flip-chip, flip-chip needs to be made into the electrode down structure. This special structure, flip chip in some process steps have special needs, such as the ohmic contact layer must have a high reflectivity, so that the surface of the chip electrode to the light can be reflected back to the sapphire side, to ensure A good light efficiency.
Flip-chip layout also need to be based on the uniform distribution of current, do the optimal design.
As wafer production process, GaN etching (Mesa etching), N-type contact layer production, passivation layer production, welding metal PAD production are basically the same with the chip is not described in detail here, the following focus on flip
Chip special process for a simple description.
In the production of LED chips, the ohmic contact layer process is the core of chip production, flip-chip is particularly important. The ohmic contact layer has the function of the conventional electrical connection and the reflective layer, as shown in Fig.
In the production process of the P-type ohmic contact layer, it is necessary to select the appropriate ohmic contact material, it is necessary to
ensure the contact resistance with P-type GaN is small, but also to ensure high reflectivity. In addition, the thickness of the metal layer and the annealing process on the ohmic contact characteristics and reflectivity is very large, this process is essential, it relates to the LED light efficiency, voltage and other important technical parameters, flip chip LED technology is the most important .
At present this layer of ohmic contact layer are generally made of silver (Ag) or silver alloy material, in the appropriate process conditions, you can get a stable high-performance ohmic contact, while ensuring ohmic contact layer reflectivity of more than 95%.
3.3, flip chip LED chip after the process
As with the LED chip, wafer process, including the chip after the process, the process shown in Figure 7, including grinding, polishing, cutting, splitting, testing and classification processes. Here the process, the only difference is the test process, other processes are basically the same as with the chip, not repeat them here.
Flip chip because the light surface and the electrode surface in a different direction, so after cutting the chip point measurement, the probe in the LED front electrode needle measurement, the LED light from the back issue. To test the LED’s optical characteristics (wavelength, brightness, half-width, etc.), must be received from the bottom of the probe station.
Therefore, the flip-chip chip testing machine and the point is different from the installation, metering device (probe or integrating sphere) must be placed under the probe and chip, and the chip stage must be light, in order to light Features.
Therefore, the flip-chip point-measuring machine needs special manufacturing or transformation.
TCOB TECHNOLOGY – What is TCOB technology in Led tube lights and Led light bulbs?(What is TCOB technology?)
-Answer: TCOB is Top Chips On Board.Also called as RCOB)Round Circle Chips On Board.And 2th Mcob.
Based on the former technology of MCOB(Multi-Chips On Board),We cooperate with Chinese Academy of Science and Germany high-end crystal material Institute, it greatly improves the MCOB technology to a higher extent, We call it TCOB or TMCOB or MCOB2th.
With TCOB technology application in fluorescent LED tube lights,when 1 pcs of the led chips on board goes bad or dead, the 1 pcs fails without afftecting other chips working as usual on the same board,and still working as good as usual.
– TCOB ensures the led fluorescent tube light takes no more than 1/288×288(about 0.0024%) failed lighting, and even no feel dark with eyes.
– We do not use AG coating again (PHILIPS led technology and we use this technology till now), it ensures our led chips will never appear bad light phoenomenon and lighting decay after thousands hours of hours wokring life.
Our factory covers more than 80.000㎡ and owns more than 1500 employees. And our led lighting tubes t5 t8 fluorescent bulbs lamps already successfully be tested and passed CE,ROHS,TUV,FCC,Certificates.
>Single Layer Crystal Ceramic Plate Board
>Led chips mounted directly on Crystal Plate
>Up to 140-188lm per watt luminous efficacy per watt
>Reaches 97% heat dispersion
MCOB TECHNOLOGY – What is MCOB technology?
-Answer: MCOB Multi-Chips On Board. MCOB ceramic encapsulation light source,Single Layer Aluminum Plate, 100 lm/w – 140 lm/w, Silicone Chips are applied directly on the aluminum plate allowing for up 97% heat dispersion, with IC-tpye Power Supply
Firm structure . High intensity. High insulativity .Anti-corrosion.
Great transmission of light nd>1.8，CRI>80 130lm/w.
Thermal cycles around 50,000 times.
Itchable ceramic surface as PCS board. No pollution.
Working temperature -55°C~+85°C
Coefficient of thermal expansion 0.000003 close to Silicon simplifies production processes.
Tight encapsulation increases power density and improves reliability of system.
Realize new encapsulation ,decreasing the size.
> MCOB of LED light source on Aluminum substrate
6 grooves on Aluminum base ,insulating treatment. Gold foil integrated circuit packaging . Luminous efficacy increased to 130LM/W. However, conductive problem should be paid attention to.
> MCOB of LED light source on ceramic substrate
6 grooves on ceramic plate with function of anti-interference and anti-static. Gold foil encapsulation increases LM/W up to 130LM/W. But cost is higher.
> MCOB fo LED light source on crystal glass substrate
Silver conducted on SIOX surface. Gold foil encapsulation. 130LM/W . Crystal glass has insufficient heat dissipation
As we know, most of COB encapsulation technologies, including the one of Japan, are based on the encapsulation of the aluminum base, which assemble some chips to be encapsulated on the aluminum base. This is what we call the COB technology. The substrate of the aluminum is copper foil, which can only well conduct electric but it can’t process optical processing very well.
LED lighting source encapsulation of Convex Structure
11: Metal die casting base (6 reflective cups) with plated relector layer.
12: LED Chip
13: Insulated glue (Mixing layer of glue and phosphor)
14: Mixing layer of glue and phosphor on surface
15: Reflective Cup (Round with LED dies sticked by insulated glue)
16: Circuit board
18: Reflective layer (Silver plating layer)
19: Wire: (LED chips connected to Circuit Board)
MCOB technology opens up new competitive advantages for LED light sources.
Feature of the lamps is MCOB (Multiple Chip Cups On Board) technology, the effect of which amounted to more than 100 – 110 lumens / watt. that can significantly improve the cooling of the LED crystals and increase the efficiency of the lamp. Lamps series.
MCOB LED technology, quite distinct from the traditional technology
puts the chips in the optical cups according to optics.
It aims to make not only one cup, but many cups. It derives from a simple principle,
i.e., the light of LED is from the chip itself, which means we need many angles to let out more light.
The light efficacy can be improved if we have more light exits. In any cases, the light efficacy of low poweres chips can be at least 15% higher than high poweres chips.
The reason is that the chips of high power are bigger and they only have four light exits.
However, we can have as many as sixteen small chips on a board and 4×16 light exits.
Advantages of the technology LED MCOB
Lower cost of LED devices and increase the efficiency of their work.
Innovational develop LED MCOB allow to achieve high brightness of the light flux, even at small sizes of lighting equipment.
Manufacturing operations is reduced by half compared with the technology of SMD, significantly reduced production time of LED devices.
High optical density of the chip: 1 cm2 area of the substrate can be set to 70 chips.
Long lifetime of LEDs MCOB, reliability and efficiency of heat transfer led-devices..
Remarkable brightness of the light flux, the lack of effect of shadows.
Compact type, small size.
Installation of MCOB LED technology: the main production stages
Surface cleaning to remove dirt.
Ultra thin pure 99% gold conductors, thickness of several microns.
Crystal silicon with a phosphor uniformly dispersing the heat from all the faces of the crystals before the main heat sink.
COB TECHNOLOGY – What is COB technology?
-Answer: COB means for Chips On Board. Chip on Board (COB) LED Lighting technology, Big LED Chip on 3 Layers Plate, 70 lm/w – 90 lm/w, Larger silicone Chips are welded the same way as on the 2nd generation surface mounted device, with 50% heat dispersion. High Power Chip on 3 Layers, 60 lm/w – 80 lm/w, with 2or4 pins welded on single-sided PCB. Patent of LumiLED for multi-angle emission by optical lens .
The greatest power densities on the smallest space are often the basis for unique selling points of various products on the market. These criteria can be realized by the ( Chip on Board ) COB LEDs technology.
Direct contacting of the semiconductors (LEDs) on PCBs allows for optimal thermal management, high packaging density and thus long-lasting and high-performance COB LED modules.
(Chip on Board) COB LED technology
With this technology, the LED chips are in the form of a semiconductor chip, which is neither encased nor connected. The semiconductor chip is described as a “Die”. This LED chip is processed by means of a special procedure which is called “Die Bonding”. Here the individual chips are placed on the PCB and using the Wire Bonding method, connected to the contact surface of the PCB, which are described as “Pads”. Gold wires in the micrometer range are used for contacting. The COB LED light technology allows for virtually limitless freedom of scope for the PCBs and thus serves as the basis for totally unique LED solutions.
The Chip-on-Board LED Module
LED technology offers better color mixing and simplified thermal management for backlighting large LCD displays.
Conventionally, LED chips have been mounted on substrates to create discrete LED components, which were attached to a printed circuit board. The solder reflow process typically used to attach the component to the circuit board subjects the LED chip to a substantial amount of heat that easily can damage the chip or degrade its performance. Hence, tight (and, therefore, expensive) process control is required for this type of assembly. In fact, the substrate cost is almost invariably the second-highest in an LED component, exceeded only by the cost of the chip itself.
A different approach, called chip-on-board packaging, seems capable of meeting all the requirements of backlighting. This method mounts the LED chip directly onto the printed circuit board using a conductive adhesive, which helps reduce costs by eliminating the substrate and complicated solder reflow assembly process. In addition, direct attachment can reduce the pitch between LED chips from the conventional 5 mm to approximately 2 mm and can lower the overall height of the light source (Figure 1).
Figure 1. By mounting the LED directly onto the printed circuit board, a substrate is unnecessary, so pitch is reduced from 5 mm to approximately 2 mm.
Decreasing the LED pitch reduces the color-mixing area required (Figure 2), which means that the area of light loss is smaller. To achieve high coupling efficiency from the light source to the lightguide plate, a reflector is incorporated into the chip-on-board package to produce an oval radiation pattern. A narrow radiation pattern on the X-axis allows more light to enter the lightguide plate, whereas a wider radiation angle on the Y-axis enhances color mixing.
Figure 2. Reducing the pitch decreases the size of the color-mixing area.
Simple thermal management
A metal core printed circuit board is used in the package to provide a low thermal resistance, allowing heat generated by the LED chip to be transferred to the heat sink via the shortest possible thermal path (Figure 3), which increases the life span; moveover, the heat transfers more efficiently through three layers than through five. The chip-on-board packages are mounted directly onto the back metal (with thermal compound at the interface), so that the heat generated by the LED chips spreads efficiently on the large metal frame for efficient dissipation without additional heat sinking. In the demonstration configuration, the entire backlight unit can maintain a temperature below 60°.
Figure 3. In comparison with the conventional approach, the thermal path is reduced. (DA = die attach, MCPCB = metal core printed circuit board.)
When compared with assemblies using conventional discrete LED packages, a chip-on-board approach can be compared with RGB LED-based LCD backlighting.
The chip-on-board leds packaging has a thin outline, it produces better color mixing, and it requires simple thermal management and potentially lowers costs, all of which better match the requirements of customers. In addition, assembling a complete backlight using the chip-on-board led package is similar to that using today fluorescent lamps, which makes a changeover relatively simple.
SMD TECHNOLOGY – What is SMD technology?
-Answer: SMD is Surface Mounted Devices. With the SMD, Surface Mounted Device style, the component is adhered directly to the printed circuit board. the output ranges differ considerably here. Small LED Chip on, 70 lm/w – 90 lm/w, Silicone Chips are welded on to a 3layers aluminum plate resulting in higher cost with only 50% heat dispersion. On many LED with a small single-power source, series resistors can be accommodated in the luminaire, and connected in parallel to constant-voltage LED transformers (similar to halogen luminaires).
With the SMD type of individual high output LED (here an example of a luminaire with an energy efficiency of approx . 50 lm/w developed in 2003), the luminaires should be connected in series to constant-current LED transformers (unused sockets must be provided with short-circuit plugs).
With the new high power SMD style LED (here an example of a luminaire with an energy efficiency of 80-100 lm/w developed in 2008) the luminaires should also be connected in series to constant-current LED transformers (unused sockets must be provided with short-circuit plugs).
DIP TECHNOLOGY – What is DIP technology?
-Answer: DIP dual inline-pin package. Also known as T-type LED.
The T-type LED is the righinal style Because the sealed casing does not allow heat to dissipate, this style is not suitable forhigh luminous power applications, but only as a signal/readiness indicator.
LED Pin On PC Board, 60 lm/w 70 lm/w, Lighting Structure is made up of many pins on a PC board to achieve good lighting effect but with poor heat dispersion from multiple pin.
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