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White LED encapsulatio

Send date: 2011-06-11 13:52 Visitor:

Because of the appearance of the GaoHui blue leds, so the light body and blue leds, the combination of white LED obtained easily.Now white LED has become a portable information product main backlighting, future lighting source even can be generally household lighting source.In addition in recent years appear high power LED nearly the same available, uv fluorescent body into a white LED, the characteristics of small, LED is low power consumption, long service life, if and have color design, stability, easy to deal with freedom of the characteristics of fluorescent body combination, can become the new lighting source.

Usually the LED and fluorescence body combination, typical methods is set in fluorescent body LED nearby, the main reason is the hope of the fluorescent physical efficiency will produce light for LED wavelength conversion, and fluorescent light body will set the high density areas line radiation, the wavelength conversion is in the most simple and easy method.In addition fluorescent body encapsulation method decided the white LED the luminous efficiency and tonal, so then will BaiGuangHua according to point of view, discusses the encapsulation of the body with fluorescent LED technology.


The BaiGuangHua fluorescent body encapsulation
Figure 1 is at present already commercialization, specific white LED it is will bring the yellow light: : Ce fluorescent body dispersed in the transparent epoxy resin, then use to establish in in a bowl in the cup from the light blue LED to stimulate converted into the white light, this style of white light shine mechanism is produced using LED blue light, in part blu-ray will stimulate YAG fluorescent body yellow to shine, and the rest of the blue light is straight in the external blue and yellow and white light into mixed color, this way is simple in structure, the characteristics of it in the LED made into append fluorescent body engineering, and thus can be coated can make cost, also sharply restraining another characteristic is chroma adjustment is very simple.
 
Blue LED + YAG fluorescent body

 
Figure 2 is change within the resin fluorescent body after concentration: the results of the plot LED color coordinates, the figure known as long as color coordinates is LED and YAG fluorescent body in two color coordinates of the formation of the linear range, can adjust tonal, depend on this: fluorescent body that low concentration, the ratio of blue light wear more, whole will appear blue fundamental key white light;Relative if YAG fluorescent body high concentration, the yellow light conversion ratio of more, whole yellow fundamental key white light.

As mentioned above will be part of the blue LED as a complementary color way, don't need high density (and the percentage of resin), so the fluorescent body coating can effectively reduce the use of fluorescent body.In general fluorescent body and the percentage of resin, although increases with the conversion efficiency: fluorescent body, and the shape of the cup bowl and change, but 10 to 20 wt % or so low proportion can get white light.In addition because blu-ray LED radiation intensity of light, in the center axis and the distribution of around is different and even LED chips around the density of fluorescent body: all the same, will still be caused shaft and the surrounding light not equal problem, and it is also necessary to overcome in one of the topics.

Figure 3 is blue LED + YAG fluorescent body white LED the production procedure;Figure 4 typical light spectrum, that by the figure that by Frame with Chip is blue LED by will set in bowl, then mix in the cup with quantitative fluorescence body the resin coating: package.Because the LED have small, save electricity, the features of the longevity, so have been widely used in mobile phones, pdas and portable information products, and lighting source backlighting trails YinDaoDeng, etc.

 


 
Figure 2 blue LED + YAG fluorescent body color of adjusting method
 

Figure 4: fluorescent body + blu-ray LED light spectrum of



The BaiGuangHua fluorescent body encapsulation

The LED chip and fluorescence body that constitute the way white LED, in addition to the above the blue LED + YAG introduced fluorescent body outside, nearly ultraviolet LED + RGB fluorescent body combination, recently also more and more attention to this way are the characteristics of the nearly LED to produce ultraviolet (uv) light, convert R G, respectively, B be synthesized into a white light, the white light of the field care than the blue LED + YAG fluorescent body way more broad, in addition ultraviolet light conversion to R, G, B action principle and traditional fluorescent lamp the same, so there is no color with uneven and play the gender is very good color.

Using R, G, B fluorescent body produce white light situations, often in advance according to certain mix ratios will adjust the fluorescent body, so then to introduce the fluorescent body adjustment method.In general evaluation light color, if use the XYZ table (CIE1931) will be color are easy to understand.Basically it's roots in XYZ table again next type with lubricious department obtained the illuminant colour three stimulation value
In addition the XYZ table color fastens wait for color close number, equivalent to standard than inspect sense degree V (lambda), so use type (1) values of the Y stimulate value be said the size of the brightness.The color of the light source is generally with (Y, x, Y), so it is called expressed CIE table color value.

RGB fluorescent body occasions, if you would use all the CIE table color fluorescent body value calculation, it is necessary to use first Jane fluorescence spectrophotometry measure relative spectral distribution, him mad again generation into the type (1) and (2) type can be obtained with the color value table, this kind of situation will usually hopes to inspire the wavelength of the fluorescent body, can fall in LED center near wavelength, so can the same test conditions, the use of the fluorescent body relative spectral distribution make table color value relative processing.The fluorescent body watch hypothesis RGB color (Y, x, Y) are as follows:
YR,xR,yR)R fluorescent body: (YR, xR, YR)
(YG,xG,yG)G: (YG, fluorescent body xG, YG)
(YB,xB,yB)B: (YB fluorescent body, xB, YB)

The white chromaticity coordinates target W (xW, yW) each Y stimulate value ratio (YR, YG, YB), according to the law the following relationship mixed color addition to established:
Y:YG:YB= Y:YG:YB=

Figure 6 is adjusted RGB mixed with fluorescent body appropriate transparent (), and cement in transparent coating substrate is made of the sample, nearly LED (light emitting peak wavelength ultraviolet luminescence properties for 384 nm).General fluorescent body membrane of the penetration of fai degree have so-called peak thickness, if films thicker than peak thickness, penetrate fai degrees will with the thickness of the increase gradually reduced.The main reason that caused the phenomenon is to stimulate rays direction and take light in the same direction, especially stimulate illuminate the near surface the high density light, with the increase of thickness will be easy to be covered;In contrast reflects fai degree is as the film thickness and increase, as through fai degrees as it won't because the film thickness and reduce the phenomenon, increase with the above situation is different, the main reason is to inspire rays direction and take light caused in opposite directions, in other words inspire the high density illuminate near the surface of the film thickness out light can be obtained, origin irrelevant to a conclusion, is to use this way to convert BaiGuangShi blue leds, to get higher light conversion efficiency, therefore hope from the LED ultraviolet (uv) light, can be RGB fluorescent body conversion into visual light, especially the demand and the blue light LED + YAG fluorescent body, the more highlight method is to improve the membrane of the fluorescent body fluorescent body filling density importance.Figure 7 is obtained by the different fluorescent body SE filling the membrane of the photos section density.
7 RGB fluorescent body of the membrane of the section
 
 
The figure 7 (a) of the known with fluorescent body mixed high, fluorescent body filling density is also the increase, according to the method of figure 6 with near ultraviolet LED inspire try materials as the peak of the degrees, through fai film thickness is equivalent to practical film thickness (50 ~ 100 u m), so uv penetration is less;Relative to the figure 7 (b) of and fluorescence body mixed is lower, light body filling density with fluorescent body, reduce the volume in the membrane of the rate change, so use nearly ultraviolet LED inspire try material, some of ultraviolet light not only cannot inspire fluorescent body absorb, it will be through to the outside, and makes the ultraviolet radiation through quantitative change much, and convert into visual light change with the lower efficiency also, in addition to penetrate fai degrees when the film thickness of the peak, will be in a more thick direction and the film thickness, film thickness than practical more thick, so general and ultraviolet LED the membrane of the fluorescent body combination, most will be by using the higher density filling.

Figure 6 is the typical nearly ultraviolet LED + RGB fluorescent body encapsulation method, in fact, the encapsulation methods can be divided into penetrate type and reflection type two kinds.Figure 8 is the encapsulation of the way through the type, basically it is to use GaN is nearly LED to Flip Chip ultraviolet way to encapsulate sapphire substrates, garnish with high reflectivity metal electrodes, so it's when light output is the traditional transparent electrodes two times as likely to put up structure to the left.
 Due to the electrode wire LED chip directly from external, so it can take to will set in fluorescent inventory LED chip surface.The fluorescent body encapsulation, basically it is in glass substrates, making ultraviolet reflex film and the RGB fluorescent intercalation, and then processed into chip and LED me with the same size, shape set in fluorescent body below and and LED chip joints, in order to make the LED chip end face of ultraviolet ray also can convert injection into visual light, so the LED chip with fluorescent body around, final reoccupy resin encapsulation type penetrate into white LED.

Figure 9 is the typical reflex white LED by the graph, that it is composed by a electrode and coated with fluorescent body the concave bowl a Flip Chip cup, ultraviolet LED by bonding with ultraviolet ray, and reflective film layer and the external electrode glass substrates, internal with resin joint again or inert gas seal, form reflex white LED.
According to the above that no matter what way, that the light body into visual light turn efficient when the uv light leakage quantity is not zero, in part because ultraviolet light radiation to the outside, so must set ultraviolet light reflection film, that is how to also increase the conversion efficiency fluorescent body will be one of the main subject.Figure 10 is a spectrum of the examples. Light
Power white light LED encapsulation

The above introduction white LED chips, size is about 0.3 mm square, each of the beam is LED about 1 ~ 2 lumens, if white LED around with a general lighting source, even to replace QuanGuangShu for 800-lumen 60 watt bulb, at least have to use the 500 white LED, so as to white LED, certainly will lose the original advantage, so relevant industry have LED chip increase proposal hope size, through which improve each LED the beam of light, such as LED chip the size of the 1 mm square, if will drive current from the current 20 mA improve 10 times become 200 mA, so it can greatly improve the light output, but improve output will face how to effectively discharge LED chip problems such as the heat energy produced.

General use uv fluorescent body produces nearly stimulate white light blue LED, external quantum efficiency (into the chip's electronic number and take the number of photons to external percentage) is about 10 to 20%, recently published in the nearly ultraviolet LED external quantum efficiency were 30%, in other words other electrical energy most are in the LED chips into heat energy, and dantian LED chips with the heat energy produced is drive current in proportion, and increase the temperature of the surrounding chip rise will cause the peak wavelength LED light mobile, fluorescent body the luminous efficiency, reduce material degradation around, so the whole package design as a high power LED heat essential.图11是Heat Sink Type Stem上方mount 1mmFigure 11 is Heat Sink by above 1 mm square Stem mount nearly ultraviolet LED appearance figure, this LED to the current 500 mA toward the light output for 190 mW and light peak wavelength for 384 mm, 50 ~ 500 mA of the peak wavelength when light mobile below 0.5 nm, figure 12 is encapsulated fluorescent lamp when body appearance.

Seal of the status of the resin. LED

In accordance with the packaging appearance LED can be divided into surface encapsulation type and shells type two kinds, ever shell for the mainstream, type is due to the needs of miniaturization after, causing the surface of gradually increasing demand of packages, but recent based on large current and heat dissipation structure considerations, so there so-called large encapsulation technology.Surface encapsulation type and can be divided into the use of mould, 'to be located printing substrate with gold thread seal components (1-(1)) photos, and use of reflector form the way that way (photo frame 1-(2), 1-3) two kinds big.
 

Transparent liquid epoxy resin.

The LED the commonly used transparent Epoxy resin is the main thing sclerosis effect without water acid, the main agent and two fluid use necessary stiffening agent before mixing to use, the main agent ingredients is Epoxy Oligomer, viscosity adjustment agent, colouring and so on;Stiffening agent without water components is acid content and catalyst amount, although the hardening agent hardening promote property will with the Lord agent and the mixture ratio stiffening agent, but generally change is designed to yield ratio of 1:1, we can get the most suitable property.Figure 13 is LED with transparent epoxy resin the structure of the principal component type.In general the so-called Epoxy Oligomer Bis-is A Glycigeru Phenol Ather and Bis-Phenol F is given priority to, in addition to prevent by glass transfer point becomes tall, resin change color, so add fat ring Type Epoxy.
 
13 LED packaging with epoxy resin were the ingredients
 

Although there are many stiffening agent and promote for epoxy resin hardening agent choice, but application in the seal is transparent LED necessary things, therefore, hardening of the stiffening agent use is a degree of restrictions, such as acid no water content will usually choose MeHHPA or HHPA;Hardening agent to promote the Amine, department of Imidazol Lin, the department is given priority to, but the actual composition is the manufacturer's how prosperous.As mentioned above epoxy resin containing many ingredients, so it's very complicated. Figure 14 is the use of the acid Amine curing agent without water content sclerosis reaction structure.
 
14 acid content without water epoxy resin hardening the response of the structure
 
.Transfer Mould 'resin. Mould

The so-called 'Mould such as photo 1-(1), it is shown in the printing substrate Epoxy resin sealing LED method, specifically it is by the Epoxy resin solid B stage, and low voltage' Tablet a high precision Mould, because with sclerosis for a very short time, so for a short time Mould 'way of production, but initial investment and die' large necessary.

.Silicon. Silicon resin

Use Silicon resin sealing LED situation is very little, so the use amount of Silicon resin is also very low.The upper market at present a 1 mm square large wafer, and white LED based on resin will reduce stress performance semiconductor considerations, he can use Silicon resin as packaging materials.In fact LED with Silicon resin packaging, belong to Silicon resin Silicon gel, the chemical structure of the it for Dimethyl Siloxane heavy fit, the refractive index of 1.4 1.5 than refractive index of epoxy resin, Silicon resin and low and devices, the LeadFame attached as epoxy resin, sex also caused take light efficiency is low, become Silicon resin is the biggest weakness.About the index of refraction of the improvement in general is Siloxane grid Phenyl and addition of, so it can be to increase the refractive index around 1.5.
 

.Silicon Silicon resin. Department

 Because of the epoxy resin can't completely remove ultraviolet absorption so the Silicon is resin was considered as encapsulation ultraviolet LED best materials, but of the Silicon resin then sex, strength and refractive index problems remain to be resolved, such as adding Phenyl base while can get the index of refraction of the Silicon, but Phenyl based ultraviolet degradation problems but are much questioned. In addition to also can get based on Silicon resin is the ultraviolet radiation resistant performance and Epoxy resin then consider sex etc, so figure 7 have Epoxy base Siloxane induces the body by told eye, again in order to improve the Silicon resin then sex on the market, so in Silane Coupling agent and similar from type paper special Silicon resin. In addition Crivello USES and Epoxy resin curing agent of the same Onium optical Cation salt, as ultraviolet sclerosis type, and get Silicon resin with Epoxy base of Silicon resin.
 
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