Lithium Battery Protect Design
In order to prevent affecting the battery life of lithium batteries in the abnormal state of the overcharge, over-discharge, over-current, typically by a lithium battery protection device to prevent damage of the abnormal state of the battery. More widely lithium battery applications, from portable devices such as mobile phones, MP3, MP4, GPS, toys to the need to continue to save gas meter data, its market capacity has reached hundreds of millions of only a month.
The lithium battery protection circuit of the device shown in Figure 1, mainly by the battery protection control IC and an external discharge switch M1 and a charging switch M2. When the P + / P-end connected to the charger, the battery normal charge, M1, M2 in the conduction state; when the control IC to detect charging abnormal, M2 is off to terminate charging. When the P + / P-end connected load, battery discharge normal, M1, M2 are turned on; when the control IC to detect abnormal discharge off the M1 termination of the discharge.
Several existing lithium battery protection program
Figure 2 is based on the principle of the lithium battery protection design of a common lithium battery protection board. In SOT23-6L package control IC package SOP8 double switch M1, M2. Vary due to the manufacturing process and manufacturing process of the switch control IC , Figure 2, two chip made from a different process, usually these two chips is also provided by the chip manufacturers.
In recent years, the industry has a few chips packaged together to improve integration, reduce the trend of the last program area. Lithium battery protection market is no exception. A and B of Figure 3, two lithium battery protection looks in Figure 2 two chip integrated on a single chip, but in fact its package internal controller IC and the switch chip is still separate and different from manufacturers, the program is only two together sealed together, commonly known as "core unity.
Two internal chip actual still from different vendors, the shape can not be a good match, resulting in the final package shapes, in many cases, can not adopt a common package. The relatively large size of this package, they can not save external components, so this "core one" program actually Province, not too much space. In terms of cost, although the cost of two packages is reduced to the cost of a package, but this package is usually relatively large, some not generic package, some in order to reduce the package size, chip stacking package in the form, so traditional compared to the two-chip solution, the cost advantage is not obvious.
Figure 4 is a true controller chip and switch chip integrated single-chip solutions in the same wafer. Switch tube in the schematic diagram of the traditional scheme 1 is an N-type tubes, and between the B-and P-In Figure 1, commonly known as cathodic protection. The program in Figure 4, for technical reasons, the switching tube can only be changed to a P-type tube, connected between the B + and P +, commonly known as the positive electrode protection. Complete program of protection board with this chip, users need to be replaced in the detection protection board test device and philosophy. Although reduced packaging costs, but the cost of the chip has not been reduced, there is no real cost advantage in the the mature traditional program with a large quantity competition. In contrast the the cathode protection concept incompatible with the traditional program became the promotion process huge obstacles.
Although the above "core one" program and Single-chip cathode protection program to the user in the size and cost of the program has brought certain advantages, but the advantage is still not clear. These programs at the same time bring some drawbacks, therefore, in the process with the the mature traditional program competitive customers, eventually only to reduce the margin space to compete on price. Because the truly original cost of these programs and there is no obvious advantage, control IC and the switch chip price cuts as the traditional program, the program of these two core one "or positive protection program has not been able to shake the market domination of the traditional program position.
Market in recent years there have been many ups switch tube chip manufacturers, in order to reduce costs, the package originally hit gold wire into a play copper the switch tube nor with ESD protection. Although these products and brand performance switch compared to some differences, but because of the cost advantage quickly seize the secondary market, but also for the traditional program with two cores one "and cathode protection program of competition in the market The win made a great contribution.
Fully integrated lithium battery protection program
The SyChip Microelectronics patent through independent research and development of a number of devices and circuits combined with unique technology, the control IC switch tube integrated on the same chip, the introduction of the world's smallest lithium battery the protection program XB430X products. This series of products using traditional N-type switch, consistent with the principle of cathodic protection of traditional programs, the protection board manufacturer or the manufacturer of lithium batteries do not need to replace any test equipment or philosophy. The series chip itself is a lithium battery protection program without the need for any external components can be realized lithium battery protection function. In order to prevent the noise of the VCC line, it is recommended in when using XB430X series chip between VCC and the negative terminal of the battery connected to a capacitor, as shown in Figure 5.
XB430X series chip integration is very high, not only to the traditional control IC and the switch integration, and the principle of Figure 1, R1, R2 is also integrated into the same chip. Integrated chip is very small, the smallest market generic SOT23-5L package. The chip series switch resistance is very low minimum internal resistance of up to 40m? With the best available switch resistance quite. When using the smallest package SOT23-5L, continuous charge and discharge current up to 2.5 amps instead of a heat problem. Continuing to charge and discharge current greater than 2.5 amps, it is recommended that SOP8 package products the XB430X series.
XB430X have all the protection features of the traditional protection programs: overcharge protection, over-discharge protection, overcurrent and short circuit protection. Moreover, due to the control IC with the switch tube integrated on the same chip, readily detect switch chip temperature control IC. A result of long-term use in high-temperature environments, or charge-discharge current exceeds the normal charge and discharge current when the battery reasons, but did not reach the overcurrent protection threshold when the chip temperature is too high, you will start over temperature protection, in order to protect the chip and battery supplier. In addition, the built-in switch tube with ESD protection, can significantly improve the yield of protection board and battery in the process.
XB430X internal control IC and switch tube from the same production process, the same vendor, package selection of the most mature and versatile package, thus consistent performance than traditional programs, two cores, one "program, the positive protection program should be much higher.
XB4301 series chip, the completion of the final battery protection program only two components (see Figure 5), compared with the five components of the traditional program, the capacity and efficiency of each placement machine can be increased to 2.5 times. Compared with the traditional program, protection board manufacturers not to buy the resistors and switch chip, to streamline the resource chain, but also in the production of the protective plate to reduce the two resistor pads and switch 8 welds, thereby greatly reducing the production costs of the protective plate.
The lithium battery protection circuit of the device shown in Figure 1, mainly by the battery protection control IC and an external discharge switch M1 and a charging switch M2. When the P + / P-end connected to the charger, the battery normal charge, M1, M2 in the conduction state; when the control IC to detect charging abnormal, M2 is off to terminate charging. When the P + / P-end connected load, battery discharge normal, M1, M2 are turned on; when the control IC to detect abnormal discharge off the M1 termination of the discharge.
Several existing lithium battery protection program
Figure 2 is based on the principle of the lithium battery protection design of a common lithium battery protection board. In SOT23-6L package control IC package SOP8 double switch M1, M2. Vary due to the manufacturing process and manufacturing process of the switch control IC , Figure 2, two chip made from a different process, usually these two chips is also provided by the chip manufacturers.
In recent years, the industry has a few chips packaged together to improve integration, reduce the trend of the last program area. Lithium battery protection market is no exception. A and B of Figure 3, two lithium battery protection looks in Figure 2 two chip integrated on a single chip, but in fact its package internal controller IC and the switch chip is still separate and different from manufacturers, the program is only two together sealed together, commonly known as "core unity.
Two internal chip actual still from different vendors, the shape can not be a good match, resulting in the final package shapes, in many cases, can not adopt a common package. The relatively large size of this package, they can not save external components, so this "core one" program actually Province, not too much space. In terms of cost, although the cost of two packages is reduced to the cost of a package, but this package is usually relatively large, some not generic package, some in order to reduce the package size, chip stacking package in the form, so traditional compared to the two-chip solution, the cost advantage is not obvious.
Figure 4 is a true controller chip and switch chip integrated single-chip solutions in the same wafer. Switch tube in the schematic diagram of the traditional scheme 1 is an N-type tubes, and between the B-and P-In Figure 1, commonly known as cathodic protection. The program in Figure 4, for technical reasons, the switching tube can only be changed to a P-type tube, connected between the B + and P +, commonly known as the positive electrode protection. Complete program of protection board with this chip, users need to be replaced in the detection protection board test device and philosophy. Although reduced packaging costs, but the cost of the chip has not been reduced, there is no real cost advantage in the the mature traditional program with a large quantity competition. In contrast the the cathode protection concept incompatible with the traditional program became the promotion process huge obstacles.
Although the above "core one" program and Single-chip cathode protection program to the user in the size and cost of the program has brought certain advantages, but the advantage is still not clear. These programs at the same time bring some drawbacks, therefore, in the process with the the mature traditional program competitive customers, eventually only to reduce the margin space to compete on price. Because the truly original cost of these programs and there is no obvious advantage, control IC and the switch chip price cuts as the traditional program, the program of these two core one "or positive protection program has not been able to shake the market domination of the traditional program position.
Market in recent years there have been many ups switch tube chip manufacturers, in order to reduce costs, the package originally hit gold wire into a play copper the switch tube nor with ESD protection. Although these products and brand performance switch compared to some differences, but because of the cost advantage quickly seize the secondary market, but also for the traditional program with two cores one "and cathode protection program of competition in the market The win made a great contribution.
Fully integrated lithium battery protection program
The SyChip Microelectronics patent through independent research and development of a number of devices and circuits combined with unique technology, the control IC switch tube integrated on the same chip, the introduction of the world's smallest lithium battery the protection program XB430X products. This series of products using traditional N-type switch, consistent with the principle of cathodic protection of traditional programs, the protection board manufacturer or the manufacturer of lithium batteries do not need to replace any test equipment or philosophy. The series chip itself is a lithium battery protection program without the need for any external components can be realized lithium battery protection function. In order to prevent the noise of the VCC line, it is recommended in when using XB430X series chip between VCC and the negative terminal of the battery connected to a capacitor, as shown in Figure 5.
XB430X series chip integration is very high, not only to the traditional control IC and the switch integration, and the principle of Figure 1, R1, R2 is also integrated into the same chip. Integrated chip is very small, the smallest market generic SOT23-5L package. The chip series switch resistance is very low minimum internal resistance of up to 40m? With the best available switch resistance quite. When using the smallest package SOT23-5L, continuous charge and discharge current up to 2.5 amps instead of a heat problem. Continuing to charge and discharge current greater than 2.5 amps, it is recommended that SOP8 package products the XB430X series.
XB430X have all the protection features of the traditional protection programs: overcharge protection, over-discharge protection, overcurrent and short circuit protection. Moreover, due to the control IC with the switch tube integrated on the same chip, readily detect switch chip temperature control IC. A result of long-term use in high-temperature environments, or charge-discharge current exceeds the normal charge and discharge current when the battery reasons, but did not reach the overcurrent protection threshold when the chip temperature is too high, you will start over temperature protection, in order to protect the chip and battery supplier. In addition, the built-in switch tube with ESD protection, can significantly improve the yield of protection board and battery in the process.
XB430X internal control IC and switch tube from the same production process, the same vendor, package selection of the most mature and versatile package, thus consistent performance than traditional programs, two cores, one "program, the positive protection program should be much higher.
XB4301 series chip, the completion of the final battery protection program only two components (see Figure 5), compared with the five components of the traditional program, the capacity and efficiency of each placement machine can be increased to 2.5 times. Compared with the traditional program, protection board manufacturers not to buy the resistors and switch chip, to streamline the resource chain, but also in the production of the protective plate to reduce the two resistor pads and switch 8 welds, thereby greatly reducing the production costs of the protective plate.
Properly Install Geared Motor
Correct installation, use and maintenance of the geared motor, an important part is to ensure the normal operation of mechanical equipment. Installed planetary geared motor, must be strictly in accordance with the following requirements and steps installed correctly:
The first step: Be sure to install the motor and geared motor are intact, and to check whether the size of each part of the motor and geared motor connected matching.
Step 2: unscrew the geared motor flange outer dust-hole on the lid, adjust the PCS system clamping ring so that the side of the hole and the dust-hole alignment, insert hex wrench. Thereafter, removal of the key of the motor output shaft. Prior to the installation of the motor input shaft positioning boss and deceleration into the the machine connected parts of the anti-rust oil wipe clean with gasoline or zinc sodium water.
The third step: the motor and deceleration into machine natural connection, the connection must guarantee consistent the geared motor input holes with the DC motor input shaft concentricity, and both the outside flange parallel, to do so can not only extend the life of the geared motor and can be obtained than ideal transmission efficiency and low noise. In addition, non-time installation hit with hammers and other heavy objects, to prevent damage to the bearings or gear axial force or excessive radial force. Connected to motor and geared motor flange mounting bolts tightened after tensioning bolt clamping ring tighten the PCS system.
The fourth step: geared motor installed turned by hand should be flexible, without catching phenomenon. Boot before tightening the various joins screw, load test should not be less than two hours, the operation should be smooth, shock, vibration, noise and oil leakage, and found that the problem should be immediately removed. Should be used regularly check each fastener is loose, to ensure proper operation.
The first step: Be sure to install the motor and geared motor are intact, and to check whether the size of each part of the motor and geared motor connected matching.
Step 2: unscrew the geared motor flange outer dust-hole on the lid, adjust the PCS system clamping ring so that the side of the hole and the dust-hole alignment, insert hex wrench. Thereafter, removal of the key of the motor output shaft. Prior to the installation of the motor input shaft positioning boss and deceleration into the the machine connected parts of the anti-rust oil wipe clean with gasoline or zinc sodium water.
The third step: the motor and deceleration into machine natural connection, the connection must guarantee consistent the geared motor input holes with the DC motor input shaft concentricity, and both the outside flange parallel, to do so can not only extend the life of the geared motor and can be obtained than ideal transmission efficiency and low noise. In addition, non-time installation hit with hammers and other heavy objects, to prevent damage to the bearings or gear axial force or excessive radial force. Connected to motor and geared motor flange mounting bolts tightened after tensioning bolt clamping ring tighten the PCS system.
The fourth step: geared motor installed turned by hand should be flexible, without catching phenomenon. Boot before tightening the various joins screw, load test should not be less than two hours, the operation should be smooth, shock, vibration, noise and oil leakage, and found that the problem should be immediately removed. Should be used regularly check each fastener is loose, to ensure proper operation.
タグ ：Geared Motor
White LED Life
White led detailed graphic analysis, and how to improve white LED package
In order to obtain a sufficient white LED beam, has developed a large-size LED chip, trying in this way to achieve the intended objectives. But will actually applied on the white LED electric power continues to exceed the above 1W beam decreased, the luminous efficiency is relatively reduced by 20% to 30%, to improve the input power and the light emitting efficiency of white LED must be overcome problems are: to suppress the temperature rise; to ensure The life ; improve luminous efficiency; luminescence properties equalization.
The increase in power will use white SMD LED package thermal impedance drops to less than 10K / W and abroad have developed high-temperature white LEDs, an attempt to improve the problem of temperature rise. More due to high power white LED heat than power white LED high number of times, even if the white LED package allows the high-calorie, but allows the temperature of the white light LED chip is certain. Suppress the temperature rise of the specific method is to reduce the thermal resistance of the package.
The specific method to improve white LED service life is to improve the chip shape, a small chip. White LED emission spectrum contains wavelengths below 450nm short wavelength light, the traditional epoxy sealing material can easily be short-wavelength light damage, high power LED light accelerated the deterioration of the sealing material. Switch to the siliceous sealed ceramic package material, white LED life can improve a few.
The specific method to improve white LED luminous efficiency is to improve the chip package structure, to achieve the same level with the low-power white LED, the main reason is the current density is increased by more than 2 times, not only is not easy removed from the large chip light, the result will resulting in luminous efficiency than the low-power white LED, and improving the electrode structure of the chip, in theory, can solve the above-described light extraction.
Luminescent characteristics homogenized specific method is to improve the white LED package, generally considered long as the phosphor material to improve the white LED uniformity of the concentration with the production technology of the phosphor can be overcome the above distress.
Reduce thermal impedance, to improve the heat dissipation problem are:
(1) Reduce the chip-to-package thermal impedance.
(2) Inhibition of the package to the printed circuit board thermal impedance.
(3) Improve the the chips heat dissipation smooth.
In order to reduce the thermal impedance, many foreign led manufacturers LED chip provided in the surface of the cooling fins made of copper with a ceramic material, as shown in Figure 1, by welding the radiating conductor of the printed circuit board connected to the use of the cooling fan forces the air-cooling fin. German OSRAM Opto Semiconductors Gmb experimental results confirmed the above structure of the LED chip to the thermal impedance of the welding points can be reduced 9K / W, approximately about 1/6 of the conventional LED. Encapsulated LED 2W of the electric power applied to the LED chip temperature higher than the welding point 18 ℃, even if the temperature of the printed circuit board to rise to 500 ° C, the temperature of the LED chip is also only about 700 ℃. Once the thermal impedance is reduced, the temperature of the LED chip will be influenced by the temperature of the printed circuit board, this must be to reduce the thermal impedance of the LED chip to the welding point. Conversely, even if the white LED has to suppress the thermal impedance of the structure, if heat from the LED package can not be conducted to the printed circuit board, the LED temperature rise will make the light emitting efficiency decreases, so Panasonic Company developed a printed circuit board and package integration technology, the side length of 1mm square blue LED to overlying chips manner packaged on the ceramic substrate, the ceramic substrate can then paste in the copper surface of the printed circuit boards, including printed circuit boards, including module The overall thermal impedance is about 15K / W.
Longevity problem for white LED, the LED manufacturers in the countermeasures taken is to change the sealing material, while the fluorescent material is dispersed in the sealing material, the material degradation and the rate of decrease of light transmittance can be suppressed more effectively.
As the epoxy absorption wavelength of 400 ~ 450nm light percentage up to 45%, the siliceous sealing material is less than 1%, epoxy luminance half-time of less than 10,000 hours, siliceous sealing material may be extended to 4 million hours (Figure 2), almost the same as with the design life of the lighting device during use, this means that the lighting device without replacing the white LED. However, the the siliceous sealing material is a soft, flexible material, the processing must be used that will not scratch the surface of the sealing material production technology siliceous and easily attached Fenxie addition process on the siliceous sealing materials must be developed in the future can improve the surface characteristics technology.
Although the siliceous sealing material can ensure that the white LED has a service life of 40,000 hours, lighting equipment industry, however, has a different view, the main debate is the life of traditional incandescent and fluorescent lamps is defined as "brightness down to 30% or less", brightness The half-time of 40,000 hours of white light LED, if converted into brightness down to 30% or less, and only about 20,000 hours. There are two longer component life, the countermeasures are:
(1) Inhibit the overall temperature rise of the white LED.
(2) The stop using the resin encapsulation.
The above two countermeasures can reach a brightness reduced to 30% of the requirements of the service life of 40,000 hours. Inhibition of white LED temperature rise the cooling white LED packages The method of the printed circuit board can be used, mainly the encapsulating resin under high temperature, coupled glare rapid deterioration, in accordance with the Porto-Vilnius rule, the temperature is reduced 100 ℃ Life will be extended to 2 times.
Stop using the resin package can completely eliminate the deterioration factors, because the white light generated by the LED light is reflected within the encapsulating resin, if used may change the chip side surface of the light traveling direction of the resin material reflecting plate, the reflecting plate will absorb light, so the amount of light extraction will dropped, and this is the main reason for using a ceramic and metal packaging materials.
There are two methods to improve the luminous efficiency of the white LED chips: one is to use an area 10 times larger than the small chip (1mm2) in a large LED chip; Another is the use of a plurality of small high luminous efficiency of the LED chip are combined into a single The body of the module. Although the large LED chip may obtain a large beam, but the negative impact of increasing the chip area, for example, light-emitting layer within the chip uneven limitation, the light-emitting portion, and the chip internally generated light is emitted to the outside will be severely attenuated. To solve the above problem, through the improvement of the electrode structure of the white LED, overlying a chip package, plus integrated chip surface technology has reached 50lm / W luminous efficiency. Large white LED package shown in Figure 4. About the equality of the light-emitting layer of the chip as a whole, since the emergence of the comb-like grid-like p-type electrode, the electrode also developed optimization direction.
About follow-chip package, due to the light-emitting layer can easily exhaust heat, plus the light emission of the light-emitting layer close to the package end to the external electrode sheltered troubled American Lumileds cooperation Toyota has officially cover a chip package , the processing of the chip surface can prevent the light emitted towards the outside of the chip from the chip's internal reflection occurs at the interface, provided on a sapphire substrate is removed in the light parts of the concavo-convex structure, the chip external light extraction efficiency can be improved about 30%. The chip side improved large LED chip packaging entity emitted light toward the reflection of the package above the plate road, high efficiency to remove the chip internal light package size is 7mm x 7mm.
Small enhancement of the luminous efficiency of the LED chip seems to be more effective than the large LED chip module. For example, Japanese CITIZEN combinations of eight small LED chips reach 60lm / W high luminous efficiency. 0.3mm x 0.3mm Nichia produced small LED chip, a package module uses up to 12 chips, each LED chip using the traditional gold wire bonding package, applied power is about 2W.
The problem of uneven luminance and color temperature of white LED must be screened in the use of optical characteristics similar to the white LED. In fact reduce the unevenness of the white LED light-emitting characteristics of the LED chip emitting characteristics of the same, and the implementation of the concentration of phosphor material uniformly distributed management is very important.
LED chip light-emitting characteristics, the manufacturers are very active chip screening, light-emitting characteristics equal treatment LED light features to reduce the problem of uneven, such as Matsushita Electric Company has reached the same characteristics of the target through the screening of the chip. The follow-chip manner, 64 LED chip package on a substrate, and finally then were covering the phosphor. LED chips during processing first encapsulated in the light emission characteristics of sub-substrate test, followed by the light emitting characteristics of the same chip transplant encapsulated in the main substrate. 8 LED chip on a substrate, even if the light emitting characteristics of the LED chip is not uniform, the total light emission characteristics of the eight LED chips in the package between the unevenness will become very small.
The white LED is usually directly coated LED chip with a sealing resin containing phosphor material, the concentration of the phosphor material in the sealing resin may occur deviation finally result in uneven distribution of the color temperature of white LED. Therefore, the resin sheet containing the phosphor material is combined with the LED chip, through strict management due to the thickness of the sheet, and the concentration of the phosphor material, so the color temperature of the white LED uneven distribution of degree less than the traditional way of 4/5. The industry that the use of the phosphor sheet with the light-emitting properties of the LED chip to change the thickness of the concentration of the phosphor sheet, you can make a white LED color temperature change of control in the expected range.
Although gradually increase the possibility of application of white LED lighting in the area with white LED luminous efficiency, but obviously, single white LED luminous flux is low, so the package unlikely to achieve a single white LED lighting lumens. For this human problem, the solution can be broadly divided into two categories: one is the more traditional use only LED light source module, which each white LED drive power and general use (for 20 to 30mA); another type of method is the use of a larger area of the chip, traditional 0.3mm2 size chip is no longer in use at this time, while the use of a size of 0.6 ~ 1mm2 chip, and use a high driving current to drive so The light-emitting components (typically 150 ~ 350mA, up to 500mA). But no matter which method is used, the will must handle high heat in a tiny LED packaging, if the components can not be dispersed these heat, in addition to a variety of packaging materials will be due to the different expansion coefficient between each other and reliable products issues, the luminous efficiency of the chip as the temperature rises, and has significantly decreased, and causing life shortened significantly. Therefore, how to disperse heat from the component to become the important subject of the current white LED encapsulation technology.
For the white LED, it is most important that the output of the luminous flux and light color, so one end of the white LED must not shading, while the need to use the effect of high transparency of the epoxy resin material coated. However, there is the epoxy almost all thermally non-conductive material, for white LED packaging technology, its white LED chip under metal feet to disperse the heat emitted by the component. Opinion, the current trend, the metal foot is mainly a high thermal conductivity coefficient material mainly consisting of, e.g., aluminum, copper or even ceramic material, etc., but a great difference in coefficient of thermal expansion between these materials and chip, the direct contact, it may be because stress generated between the material at elevated temperatures and cause reliability problems, so usually coupled with a material between the intermediate material of appropriate conductivity and expansion coefficient as the interval. Matsushita Electric company only made of white LED is still in the metal material and the metal line module on a multilayer substrate made of the composite material to form a light source module, the high thermal conductivity of the substrate effect on the use of a light source, so that the output of the light source in the prolonged use able to maintain the stability. Lumileds production of the materials used in the white LED substrate of copper having a high conductivity, and then its connection to a special metal circuit board, it can be both circuit conduction and increase the effect of the heat conduction.
The high-power white LED chip manufacturing technology, packaging technology seems to have become a mainstream technology for high brightness white LED, the largest chip manufacturing technology and packaging technology, however, is not just the chip area bigger, if they want to apply white LED high brightness lighting field, technology has yet to be studied further.
White LED in general lighting field, there are still many problems to be solved, first white LED efficiency, such as the the GaInN Department of the green, blue and near-UV LED efficiency is still a big development margin. In addition, the internal quantum efficiency of the integrated energy efficiency is the most important item, and the internal quantum efficiency by the active layer of the non-light-emitting the percentage light emitting recombination percentage decided, it can lock the focus to this part in the non-light emitting recombination, and managed to reduce the crystal defects. And to reduce the dislocation density of the UV LED can indeed significantly improve internal quantum efficiency, the future need for the UV LED to further reduce the dislocation density. However, this countermeasure of green, blue LED does not have a significant impact.
Green and blue LEDs at low current densities (around 1A/cm2) have the maximum quantum efficiency, the quantum efficiency in the high current density will decrease, as shown in Figure 7. LED can be driven with high current density as possible while increasing the output power of the component, so the early unlock the mechanism and cause of decrease of the quantum efficiency in the green and blue LED high current density from the cost viewpoint, not only is the material The physical characteristics of exploration on the need for future applications, the study also has a key role. The present study shows violet LED (wavelength of 382nm) is applied, the high current density (50A/cm2), the quantum efficiency is not lowered.
The conventional white LED are the side length of 200 to 350 μm square chip packaged into a ball pillar shape, after the required order to obtain the lighting beam, then is encapsulated a plurality of white LED components are arranged in a matrix shape. Simply to high output power for the purpose of especially developed area ratio the conventional chip 6 to 10 times, dimensions up to 500 μm to 1 mm of the white LED Although the package obtained after several hundred milliwatts (tens of lumens) of output power, increase the dimensions of the chip, but the white LED light within the absorption ratio increased external light extraction rate decreased. For example, AlGaInP LED Dimensions of the chip is 0.50mm x 0.50mm, 0.22mm x 0.22mm increase external light extraction rates have reduced by about 20%. If the switch TIP structure, internal result of multiple reflection so that the internal light absorption rate decreased, the external light extraction efficiency is improved significantly. The GaInN LED also has the same effect. How to improve the external light extraction efficiency of the LED chip LED used in the field of general lighting. In addition, the considerable disadvantage of high thermal impedance (150 ~ 200K / W) for the high brightness output. LED internal quantum efficiency of the active layer temperature dependence great addition to the low thermal resistance packaging technology, the use of heat sinks become hot spots for future R & D exclude active layer of heat.
In order to obtain a sufficient white LED beam, has developed a large-size LED chip, trying in this way to achieve the intended objectives. But will actually applied on the white LED electric power continues to exceed the above 1W beam decreased, the luminous efficiency is relatively reduced by 20% to 30%, to improve the input power and the light emitting efficiency of white LED must be overcome problems are: to suppress the temperature rise; to ensure The life ; improve luminous efficiency; luminescence properties equalization.
The increase in power will use white SMD LED package thermal impedance drops to less than 10K / W and abroad have developed high-temperature white LEDs, an attempt to improve the problem of temperature rise. More due to high power white LED heat than power white LED high number of times, even if the white LED package allows the high-calorie, but allows the temperature of the white light LED chip is certain. Suppress the temperature rise of the specific method is to reduce the thermal resistance of the package.
The specific method to improve white LED service life is to improve the chip shape, a small chip. White LED emission spectrum contains wavelengths below 450nm short wavelength light, the traditional epoxy sealing material can easily be short-wavelength light damage, high power LED light accelerated the deterioration of the sealing material. Switch to the siliceous sealed ceramic package material, white LED life can improve a few.
The specific method to improve white LED luminous efficiency is to improve the chip package structure, to achieve the same level with the low-power white LED, the main reason is the current density is increased by more than 2 times, not only is not easy removed from the large chip light, the result will resulting in luminous efficiency than the low-power white LED, and improving the electrode structure of the chip, in theory, can solve the above-described light extraction.
Luminescent characteristics homogenized specific method is to improve the white LED package, generally considered long as the phosphor material to improve the white LED uniformity of the concentration with the production technology of the phosphor can be overcome the above distress.
Reduce thermal impedance, to improve the heat dissipation problem are:
(1) Reduce the chip-to-package thermal impedance.
(2) Inhibition of the package to the printed circuit board thermal impedance.
(3) Improve the the chips heat dissipation smooth.
In order to reduce the thermal impedance, many foreign led manufacturers LED chip provided in the surface of the cooling fins made of copper with a ceramic material, as shown in Figure 1, by welding the radiating conductor of the printed circuit board connected to the use of the cooling fan forces the air-cooling fin. German OSRAM Opto Semiconductors Gmb experimental results confirmed the above structure of the LED chip to the thermal impedance of the welding points can be reduced 9K / W, approximately about 1/6 of the conventional LED. Encapsulated LED 2W of the electric power applied to the LED chip temperature higher than the welding point 18 ℃, even if the temperature of the printed circuit board to rise to 500 ° C, the temperature of the LED chip is also only about 700 ℃. Once the thermal impedance is reduced, the temperature of the LED chip will be influenced by the temperature of the printed circuit board, this must be to reduce the thermal impedance of the LED chip to the welding point. Conversely, even if the white LED has to suppress the thermal impedance of the structure, if heat from the LED package can not be conducted to the printed circuit board, the LED temperature rise will make the light emitting efficiency decreases, so Panasonic Company developed a printed circuit board and package integration technology, the side length of 1mm square blue LED to overlying chips manner packaged on the ceramic substrate, the ceramic substrate can then paste in the copper surface of the printed circuit boards, including printed circuit boards, including module The overall thermal impedance is about 15K / W.
Longevity problem for white LED, the LED manufacturers in the countermeasures taken is to change the sealing material, while the fluorescent material is dispersed in the sealing material, the material degradation and the rate of decrease of light transmittance can be suppressed more effectively.
As the epoxy absorption wavelength of 400 ~ 450nm light percentage up to 45%, the siliceous sealing material is less than 1%, epoxy luminance half-time of less than 10,000 hours, siliceous sealing material may be extended to 4 million hours (Figure 2), almost the same as with the design life of the lighting device during use, this means that the lighting device without replacing the white LED. However, the the siliceous sealing material is a soft, flexible material, the processing must be used that will not scratch the surface of the sealing material production technology siliceous and easily attached Fenxie addition process on the siliceous sealing materials must be developed in the future can improve the surface characteristics technology.
Although the siliceous sealing material can ensure that the white LED has a service life of 40,000 hours, lighting equipment industry, however, has a different view, the main debate is the life of traditional incandescent and fluorescent lamps is defined as "brightness down to 30% or less", brightness The half-time of 40,000 hours of white light LED, if converted into brightness down to 30% or less, and only about 20,000 hours. There are two longer component life, the countermeasures are:
(1) Inhibit the overall temperature rise of the white LED.
(2) The stop using the resin encapsulation.
The above two countermeasures can reach a brightness reduced to 30% of the requirements of the service life of 40,000 hours. Inhibition of white LED temperature rise the cooling white LED packages The method of the printed circuit board can be used, mainly the encapsulating resin under high temperature, coupled glare rapid deterioration, in accordance with the Porto-Vilnius rule, the temperature is reduced 100 ℃ Life will be extended to 2 times.
Stop using the resin package can completely eliminate the deterioration factors, because the white light generated by the LED light is reflected within the encapsulating resin, if used may change the chip side surface of the light traveling direction of the resin material reflecting plate, the reflecting plate will absorb light, so the amount of light extraction will dropped, and this is the main reason for using a ceramic and metal packaging materials.
There are two methods to improve the luminous efficiency of the white LED chips: one is to use an area 10 times larger than the small chip (1mm2) in a large LED chip; Another is the use of a plurality of small high luminous efficiency of the LED chip are combined into a single The body of the module. Although the large LED chip may obtain a large beam, but the negative impact of increasing the chip area, for example, light-emitting layer within the chip uneven limitation, the light-emitting portion, and the chip internally generated light is emitted to the outside will be severely attenuated. To solve the above problem, through the improvement of the electrode structure of the white LED, overlying a chip package, plus integrated chip surface technology has reached 50lm / W luminous efficiency. Large white LED package shown in Figure 4. About the equality of the light-emitting layer of the chip as a whole, since the emergence of the comb-like grid-like p-type electrode, the electrode also developed optimization direction.
About follow-chip package, due to the light-emitting layer can easily exhaust heat, plus the light emission of the light-emitting layer close to the package end to the external electrode sheltered troubled American Lumileds cooperation Toyota has officially cover a chip package , the processing of the chip surface can prevent the light emitted towards the outside of the chip from the chip's internal reflection occurs at the interface, provided on a sapphire substrate is removed in the light parts of the concavo-convex structure, the chip external light extraction efficiency can be improved about 30%. The chip side improved large LED chip packaging entity emitted light toward the reflection of the package above the plate road, high efficiency to remove the chip internal light package size is 7mm x 7mm.
Small enhancement of the luminous efficiency of the LED chip seems to be more effective than the large LED chip module. For example, Japanese CITIZEN combinations of eight small LED chips reach 60lm / W high luminous efficiency. 0.3mm x 0.3mm Nichia produced small LED chip, a package module uses up to 12 chips, each LED chip using the traditional gold wire bonding package, applied power is about 2W.
The problem of uneven luminance and color temperature of white LED must be screened in the use of optical characteristics similar to the white LED. In fact reduce the unevenness of the white LED light-emitting characteristics of the LED chip emitting characteristics of the same, and the implementation of the concentration of phosphor material uniformly distributed management is very important.
LED chip light-emitting characteristics, the manufacturers are very active chip screening, light-emitting characteristics equal treatment LED light features to reduce the problem of uneven, such as Matsushita Electric Company has reached the same characteristics of the target through the screening of the chip. The follow-chip manner, 64 LED chip package on a substrate, and finally then were covering the phosphor. LED chips during processing first encapsulated in the light emission characteristics of sub-substrate test, followed by the light emitting characteristics of the same chip transplant encapsulated in the main substrate. 8 LED chip on a substrate, even if the light emitting characteristics of the LED chip is not uniform, the total light emission characteristics of the eight LED chips in the package between the unevenness will become very small.
The white LED is usually directly coated LED chip with a sealing resin containing phosphor material, the concentration of the phosphor material in the sealing resin may occur deviation finally result in uneven distribution of the color temperature of white LED. Therefore, the resin sheet containing the phosphor material is combined with the LED chip, through strict management due to the thickness of the sheet, and the concentration of the phosphor material, so the color temperature of the white LED uneven distribution of degree less than the traditional way of 4/5. The industry that the use of the phosphor sheet with the light-emitting properties of the LED chip to change the thickness of the concentration of the phosphor sheet, you can make a white LED color temperature change of control in the expected range.
Although gradually increase the possibility of application of white LED lighting in the area with white LED luminous efficiency, but obviously, single white LED luminous flux is low, so the package unlikely to achieve a single white LED lighting lumens. For this human problem, the solution can be broadly divided into two categories: one is the more traditional use only LED light source module, which each white LED drive power and general use (for 20 to 30mA); another type of method is the use of a larger area of the chip, traditional 0.3mm2 size chip is no longer in use at this time, while the use of a size of 0.6 ~ 1mm2 chip, and use a high driving current to drive so The light-emitting components (typically 150 ~ 350mA, up to 500mA). But no matter which method is used, the will must handle high heat in a tiny LED packaging, if the components can not be dispersed these heat, in addition to a variety of packaging materials will be due to the different expansion coefficient between each other and reliable products issues, the luminous efficiency of the chip as the temperature rises, and has significantly decreased, and causing life shortened significantly. Therefore, how to disperse heat from the component to become the important subject of the current white LED encapsulation technology.
For the white LED, it is most important that the output of the luminous flux and light color, so one end of the white LED must not shading, while the need to use the effect of high transparency of the epoxy resin material coated. However, there is the epoxy almost all thermally non-conductive material, for white LED packaging technology, its white LED chip under metal feet to disperse the heat emitted by the component. Opinion, the current trend, the metal foot is mainly a high thermal conductivity coefficient material mainly consisting of, e.g., aluminum, copper or even ceramic material, etc., but a great difference in coefficient of thermal expansion between these materials and chip, the direct contact, it may be because stress generated between the material at elevated temperatures and cause reliability problems, so usually coupled with a material between the intermediate material of appropriate conductivity and expansion coefficient as the interval. Matsushita Electric company only made of white LED is still in the metal material and the metal line module on a multilayer substrate made of the composite material to form a light source module, the high thermal conductivity of the substrate effect on the use of a light source, so that the output of the light source in the prolonged use able to maintain the stability. Lumileds production of the materials used in the white LED substrate of copper having a high conductivity, and then its connection to a special metal circuit board, it can be both circuit conduction and increase the effect of the heat conduction.
The high-power white LED chip manufacturing technology, packaging technology seems to have become a mainstream technology for high brightness white LED, the largest chip manufacturing technology and packaging technology, however, is not just the chip area bigger, if they want to apply white LED high brightness lighting field, technology has yet to be studied further.
White LED in general lighting field, there are still many problems to be solved, first white LED efficiency, such as the the GaInN Department of the green, blue and near-UV LED efficiency is still a big development margin. In addition, the internal quantum efficiency of the integrated energy efficiency is the most important item, and the internal quantum efficiency by the active layer of the non-light-emitting the percentage light emitting recombination percentage decided, it can lock the focus to this part in the non-light emitting recombination, and managed to reduce the crystal defects. And to reduce the dislocation density of the UV LED can indeed significantly improve internal quantum efficiency, the future need for the UV LED to further reduce the dislocation density. However, this countermeasure of green, blue LED does not have a significant impact.
Green and blue LEDs at low current densities (around 1A/cm2) have the maximum quantum efficiency, the quantum efficiency in the high current density will decrease, as shown in Figure 7. LED can be driven with high current density as possible while increasing the output power of the component, so the early unlock the mechanism and cause of decrease of the quantum efficiency in the green and blue LED high current density from the cost viewpoint, not only is the material The physical characteristics of exploration on the need for future applications, the study also has a key role. The present study shows violet LED (wavelength of 382nm) is applied, the high current density (50A/cm2), the quantum efficiency is not lowered.
The conventional white LED are the side length of 200 to 350 μm square chip packaged into a ball pillar shape, after the required order to obtain the lighting beam, then is encapsulated a plurality of white LED components are arranged in a matrix shape. Simply to high output power for the purpose of especially developed area ratio the conventional chip 6 to 10 times, dimensions up to 500 μm to 1 mm of the white LED Although the package obtained after several hundred milliwatts (tens of lumens) of output power, increase the dimensions of the chip, but the white LED light within the absorption ratio increased external light extraction rate decreased. For example, AlGaInP LED Dimensions of the chip is 0.50mm x 0.50mm, 0.22mm x 0.22mm increase external light extraction rates have reduced by about 20%. If the switch TIP structure, internal result of multiple reflection so that the internal light absorption rate decreased, the external light extraction efficiency is improved significantly. The GaInN LED also has the same effect. How to improve the external light extraction efficiency of the LED chip LED used in the field of general lighting. In addition, the considerable disadvantage of high thermal impedance (150 ~ 200K / W) for the high brightness output. LED internal quantum efficiency of the active layer temperature dependence great addition to the low thermal resistance packaging technology, the use of heat sinks become hot spots for future R & D exclude active layer of heat.
