Semiconductor lighting is a technological revolution in this century. From the perspective of technological maturity, it is still a baby. Although LED high-power white light technology is developing rapidly, LED light decay, heat dissipation and cost are still three LEDs. The road to the development of lighting popularity.
LED light decay and heat dissipation have penetrated the entire industrial chain from chip manufacturing, packaging process, material selection, and lamp development. At present, the industry has insufficient understanding of the concept of light decay, the causes and how to solve it. There is no authoritative explanation for the theory. It is difficult to introduce it, so that there are people who are clouded, and you copy me into a strange technical chaos. For a long time, people have been desperately trying to reduce the LED light decay by using heat dissipation methods, but the effect is very small.
Solving the problem of LED light decay has become a common concern and eagerly awaited technical problem in the industry. People can't help but ask: Why does the designer not find another way to find the cause of LED light decay from the source? The author can improve the temperature resistance of the LED light source to reduce the LED light decay. The theory and practice have been discussed in depth, and relevant articles and experimental reports will be launched one after another.
First, LED light effect: the meaning of distinguishing between transient light effect and steady light effect
Second, LED thermal resistance: the meaning of distinguishing the internal thermal resistance of the light source and the external thermal resistance of the light source
Third, LED light decay: Light decay is an irreversible damage phenomenon of light source components exceeding the temperature limit.
First, improve the temperature resistance of LED light source can reduce LED light decay
Second, why should we improve the temperature resistance of LED light source?
Third, how to make the LED light source to withstand high temperatures
First, the integrated light source tomb substrate and aluminum substrate are completely unnecessary to achieve 3750V withstand voltage
Second, LED drive power can use liquid cooling technology to solve this short board
First, LED light effect
The luminous flux (lm) emitted by the LED light source divided by the power consumed by the light source (W) is called the LED luminous efficacy in lm/W.
Distinguish between transient light effects and steady-state light effects
LED transient light efficiency refers to the luminous efficiency when the LED light source starts to work. It is also called the initial cold light effect. It is the instantaneous luminous flux measured by applying a certain short pulse current to the measured light source. The measurement usually gives more than the chip and is smaller than the chip. The heating time constant of the substrate is usually in the range of 1 to several tens of ms.
Transient light effect is a short-time light-electrical conversion characteristic of the LED light source, which is related to the quantum excitation capability of the chip and the phosphor, the refractive index of the colloid, the transmittance, the reflectance of the support structure (reflector), and the junction temperature of the chip. Basically irrelevant. It only measures the contrast, and the transient light effect does not represent the actual working state.
The steady-state light effect refers to the ratio of the luminous flux measured by the LED light source to the electric power after the thermal operation of the LED light source is not stable and the light intensity is no longer changed. The steady-state light effect refers to the system light effect of the LED overall luminaire in addition to the driving power supply, which reflects the comprehensive light, electricity and heat characteristics of the LED actually working. The steady-state light effect includes the temperature change state of the heat transfer and heat dissipation of the system in addition to the transient light and electrical characteristics of the LED, which is also called the system light, which is the real working efficiency of the overall lamp.
Second, LED thermal resistance
LED thermal resistance
Thermal resistance generally refers to the resistance of heat flow through an object. It is determined by the nature of the material. The magnitude of the thermal resistance is proportional to the length of the path through which the heat flow passes, inversely proportional to the cross-sectional area of â€‹â€‹the path, and inversely proportional to the thermal conductivity of the material. which is:
2. Distinguish the internal thermal resistance of the light source and the external thermal resistance of the light source
For the system, the LED thermal resistance includes: the internal thermal resistance of the light source and the external thermal resistance of the light source are shown in Figure 1.
Internal thermal resistance of the light source
The internal thermal resistance of the light source is also called the package thermal resistance, including:
(1) The thermal resistance of the LED chip material itself, RL1.
(2) Chip and substrate (heat sink) bonding thermal resistance, RL2.
(3) substrate conduction thermal resistance RL3,
(4) Potting colloidal thermal resistance, RL4.
(5) Lens thermal resistance, RL5.
The external thermal resistance of the light source includes:
(1) The thermal conductivity of the thermal silica gel under the heat sink, RO1.
(2) CCL thermal resistance, RO2.
(3) Thermal resistance of the insulating film between the copper clad laminate and the aluminum substrate, RO3.
(4) Thermal resistance of aluminum substrate, RO4.
(5) Thermal conductivity between the aluminum substrate and the heat sink generates thermal resistance, RO5.
(6) Radiator thermal resistance, RO6.
The internal thermal resistance of the light source in the application is the thermal resistance of the package. It is related to the light decay and the longevity. It is an important indicator to measure the quality of the light source. It cannot be changed for the user of the lamp, that is, the system design has nothing to do. The system efficacy is inversely proportional to the thermal resistance of the system. The lower the thermal resistance, the higher the light efficiency.
3, using the ratio of steady-state light effect to transient light efficiency to measure the photothermal characteristics of the system
At present, the LED light source thermal resistance measurement has not yet issued a standard. Generally, the voltage measurement method is adopted according to the thermal resistance measurement method of an ordinary semiconductor device, and the K value is first measured, and then the thermal resistance of the PN junction to the PN junction is calculated. There are also spectroscopy, photothermal resistance scanning and optical power methods. Due to the complexity of the measurement procedure and the difficulty of specification, it is still not widely used. The introduction of LED "thermal resistance" from heat transfer is nothing more than hoping to find out the temperature rise of each light source and each node of the lamp through measurement, so as to design the light source temperature to work within a safe range and reduce LED light decay. In fact, the purpose of testing the junction temperature and calculating the thermal resistance is only to compare the heat transfer performance of the system, in order to optimize the heat dissipation/cost ratio. This eliminates the need to bend the corner to repeatedly measure and calculate, and the operation complexity is not accurate enough. I suggest that as long as the temperature difference between the heat transfer paths of each level is measured in the LED lamp system, the thermal resistance between them can be expressed, that is, the "node temperature difference" is used to understand the "thermal resistance". I recommend using the ratio of steady-state light effect to transient light efficiency to measure the photothermal characteristics of the system. Measurement method: First measure the transient light effect of å²€. When the system works into thermal stability, the temperature of the light source no longer rises, the light intensity no longer drops, and the steady-state light effect is measured after relatively stable. The steady-state light effect divided by the transient light effect is the steady-state light effect and transient state. The ratio of light effect, according to the inverse relationship between thermal resistance and light effect, the ratio of the value can be seen the quality of the system light or thermal resistance of different lamps, pay attention to the usual measurement to eliminate the power supply. For example, two different street lamps A and B, respectively, measure the ratio of their transient light effect to steady-state light efficiency, A=95%, B=90%, then it can be determined that A is better than B. This test method is simple and easy. Operation, the author suggests that the measurement method should be recommended in the industry measurement specifications and technical standards after discussion and improvement.
Third, LED light decay
1, LED light decay: LED light decay means that after a period of illumination of the LED, its light intensity will be lower than the initial light intensity, and can not be recovered, that is, the reduced part is called the light decay of the LED. At present, China has not yet established a definition and general standard for LED light decay. GB/T 24823-2009 requires the lumen maintenance rate specified by the performance requirements of the LED module. When the ignition point is 3000h, the lumen maintenance rate should be no less than 92%. Only one product of the indoor lighting is tested. The industry generally calls for the country to formulate LEDs as soon as possible. Light decay standard.
2, LED light decay is the irreversible damage phenomenon of the light source component exceeding the temperature limit
It is well known that after the LED works, its light intensity will decrease as the junction temperature of the chip rises, and the light efficiency will decrease. This is the inherent physical property of the semiconductor as it changes with temperature. As long as a certain component of the light source does not exceed the temperature limit, the LED stops. After the temperature drops to the original å€¤, its light intensity will return to the original, that is to say, no matter how long the LED works, it can not be considered as light decay as long as the initial light intensity is constant. The light fading refers to the light source exceeding the limit due to the long working temperature. The light intensity is not restored to the initial nickname, but the irreversible decrease in luminous flux is the true meaning of light decay. LED light decay is an irreversible damage phenomenon in which the light source component exceeds the temperature limit.
3, the current light efficiency of all chip and packaging factories is transient light effect
Some people think that the relationship between the junction temperature of LED chips announced by CREE in the United States is the LEF light decay curve. Many people regard it as the LED chip light decay curve, and even the packaging factory will copy it to the factory specification book. This is wrong.
The relationship between temperature and luminous flux/optical power disclosed in CREE above is based on expressing to the user that in the design and use, the chip should not exceed a certain junction temperature range to ensure that the luminous flux is reduced or the light decay occurs under the rated optical power. The author believes that this set of curves is not the causal relationship of the LED chip's light decay. It should be the comprehensive curve of the various components related to the luminous flux and temperature of the LED light source. Many people think that this set of curves is the cause of pure chip light decay, and does not include phosphors, viscose, stents, and temperature-related system components. This is a misunderstanding. Whether the LED light source is tested at Ta=25Â° or Ta=85Â°C, it is the steady-state measurement value of the light source system at a certain temperature. Because the steady-state light effect is affected by many temperature variables, the test complexity is not accurate enough. And the time is longer, so the current nominal light efficiency of all chip factories and packaging factories are transient light effects, as well as downstream user acceptance. No matter which company in the world publishes product performance indicators must be operable and repeatable, which means that customers who purchase your products cannot or cannot be tested for their specifications, they cannot pass. Some foreign manufacturers deliberately exaggerate the light effect more than the traditional value is not practical, because LED light efficiency and light decay is not caused by a single factor of the LED chip, it is related to many conditions of the system thermal resistance, take the laboratory light effect Only the propaganda meaning has no practical significance. If a company launches the 303LM/W product and does not push it to the market, the industry cannot understand and agree. It is not the only reason to decide the LED light effect chip, nor is it the main reason. Users blindly pursuing a certain brand and not paying attention to system design are misunderstandings, and they will work hard and lose half the effort.
Discussing the widely popular professional words such as LED light effect, LED thermal resistance and LED light decay, the meaning of distinguishing between transient light effect and steady light effect is to further reveal the cause of LED light decay and find out the solution. At the same time, it is undoubtedly beneficial to define the definition of LED technology terms and establish relevant technical standards.
Fourth, the cause of LED light decay
1, LED light decay is the irreversible attenuation failure caused by the damage of the light source material
LED light decay means that after a period of illumination of the LED, its light intensity will be lower than the original light intensity, and the low part is the light decay of the LED. At present, China has not formulated the LED light decay standard, and the industry internally stipulates 5000H. The hourly luminous flux maintenance rate is â‰¥70%, which is considered to be invalid.
2, the decrease in luminous flux is not equal to the light decay
It is well known that after the LED works, its light intensity will decrease as the junction temperature of the chip rises, and the light efficiency will decrease. This is the inherent physical property of the semiconductor as it changes with temperature. As long as a certain component of the LED light source does not exceed the temperature limit and the LED is stopped, the light intensity will be restored as soon as the temperature is restored. That is to say, no matter how long the LED works, as long as the initial light intensity is constant, it cannot be regarded as light decay. The author believes that LED light decay refers to the failure phenomenon that the LED light source is no longer recovered due to certain material damage, that is, the LED light source has no loss of luminous flux (initial light intensity) and lossy luminous flux (attenuated unrecoverable light intensity) within the specified time. The ratio.
3, the main cause of LED light source light decay is that the gel is not resistant to temperature
As we all know, the chip (including phosphor) is an inorganic material, and experiments have proved that the chip and the phosphor are not a problem in the principle of high-temperature operation of two or three Baidu. From the light source system, the main cause of LED light decay is that the gel is not resistant to temperature. At present, the best package rubber has a temperature resistance of only one hundred degrees. The test proves that a 50W integrated light source is often used when the radiator is large enough. Up to more than 200 degrees, whether it is potting glue or PPA in the long-term high temperature operation will inevitably cause colloid cracking, carbonization, and separation from the chip and cause light decay.
From the luminaire system, LED light decay is related to system thermal resistance, including heat dissipation channels, heat dissipation materials, heat dissipation methods, and temperature-related components.
The light decay of the LED light source is determined by the structure of the support, the chip, the quality of the phosphor, the temperature resistance of the gel, and the process of the packaging process. These conditions are selected by the packaging factory, and the preferred is the weather resistance of the package bracket and the gel. In a sense, the core technology of LED packaging should be the development and manufacturing technology of package bracket, which determines the purpose, function and cost performance of LED light source.
Fifth, improve the temperature resistance of LED light source can reduce LED light decay
1. Why do you want to improve the temperature resistance of LED light sources?
It is well known that LEDs belong to semiconductor low-temperature heating devices. Low-temperature heat sources have low heat dissipation efficiency under natural heat dissipation conditions. LEDs transfer heat to the air through convection and radiation. If the temperature difference between the LED heat sink and the ambient temperature is small, heat dissipation is further increased. The area of â€‹â€‹the device has little change in heat dissipation. Theoretical studies have shown that the amount of radiative heat dissipation is proportional to the fourth power of temperature: Q = ÎµÏƒ S (T w 4 -T0 4 ), the greater the temperature difference, the more heat is dissipated. That is, the higher the temperature of the heat sink at the same ambient temperature, the more heat is dissipated. Therefore, the operating temperature of the heat sink is appropriately increased, and the principle that the steady-state light effect does not change greatly after the LED light source is operated for a long time without light decay is controlled. This design idea of â€‹â€‹improving the high temperature resistance of the LED light source is not only based on balanced heat dissipation and cost considerations, but also mainly allows the LED light source to work safely at a higher temperature without occurrence of light decay. This not only reduces the amount and cost of the heat sink, but also increases the load carrying capacity of the working current of the chip, and at the same time achieves the purpose of reducing the LED light decay and prolonging the service life, and is a design revolution with multiple achievements.
2. How to make the LED light source withstand high temperature
Since the advent of LEDs, the industry has invested heavily in researching LED light decay. LED cooling affects every nerve engaged in LED people, and has tried many ways, among which:
*Flip-chip technology: Flip-chip technology as early as 10 years ago, foreign large companies invested heavily in research, aiming to avoid the use of substrate glue die welding technology, not only eliminating the fatal injury of the surface of the flip chip on the surface, but also The direct soldering technology can effectively reduce the thermal resistance of the package and allow the light source to withstand high temperatures. The industry is generally considered to be the leading edge technology of LED packaging. But people have to ask: After years of research and experimentation, why is the flip-chip technology unable to replace the positive-loading chip technology and become the mainstream? The root cause is that the early process of flip-chip relies not only on the ceramic substrate, but also on the aluminum (copper) substrate. Since the (twice) over-weld is subjected to a high temperature of 280 degrees, it will cause damage to materials and components. Compared with the metal substrate, the ceramic substrate has a low reflectance, and it is difficult to improve the transient light effect. The thermal conductivity of the ceramic substrate and the limited contact area of â€‹â€‹the chip also determine that the steady-state light effect is difficult to improve. The processing and installation are not as simple and convenient as the metal substrate. The flip-chip process twice soldering and the ceramic substrate + aluminum substrate double thermal resistance is enough to offset the above advantages. In addition, the equipment of hot-press welding and reflow soldering of the flip-chip process is expensive and immature, and the future of the flip-chip technology is still LM\yuan value, that is, the light effect is the first, and the price is king. Therefore, it caused a small factory to wait and see, and the promotion of large-scale products was difficult. The future development direction of flip chip technology is to marry the mirror aluminum COM, and the second is to graft with the fluorescent film.
*, phosphor away from chip technology
The phosphor and the potting compound tightly wrap the chip, which seriously affects heat dissipation. Keeping the phosphor away from the chip can reduce the thermal resistance of the light source package. Internationally, there are as many as two or three hundred patents for phosphor and chip separation technology, but so far the market has not seen such products successfully, because the difficulty of this technology is how to change the interlayer dielectric refraction matching after the phosphor is far away from the chip, and the chip How to get protection with gold wire bare is also a technical difficulty. At present, some factories use fluorescent films in small-scale power source experiments, but the manufacturing process and material weather resistance are not yet mature. The phosphors away from the chip technology can not only reduce the thermal resistance of the light source package, but more importantly, it can remove the glue and pump in the packaging factory. Vacuum, baking and other complicated processes. Once the breakthrough is undoubtedly a technological revolution that changes the packaging landscape.
*, liquid cooling technology
The method of dissipating the chip into the cooling liquid is to let the LED be immersed in the light-transmitting and heat-conducting liquid. The heat is quickly transferred and dissipated due to the heat exchange of the liquid. As long as there is a temperature difference between the chip and the thermal fluid, its heat flow exchange never stops. It can greatly reduce the thermal resistance of the package and is a very good design idea. Many experts at home and abroad have proposed this method, and there are countless patents. However, in the actual design, the liquid is cooled in a small package space, and subjected to high and low temperature repeated changes without leaking, and the structural design is very difficult.
*. With integrated ( COB ) package, for multiple low power arrays, the light intensity/thermal resistance ratio can be increased because the light intensity is in parallel with the heat dissipation.
*. Leather base rubber, leather de-filling glue, leather high temperature and vulnerable materials to improve the temperature resistance of the light source.
*. Reduce the total reflection of the light path, optimize the light angle, improve the light efficiency of the LED light source, and reduce system heating.
*. The aluminum substrate is removed to improve the steady-state light effect and transient light efficiency ratio.
*. Reduce the lens light distribution loss.
*. Reduce the light blocking loss of the protective member.
LED is a low-temperature semiconductor heating device. The low-temperature heat source has low heat dissipation efficiency under natural heat dissipation conditions. The greater the temperature difference at the same ambient temperature, the more heat is dissipated. The higher the temperature of the heat sink, the more heat it dissipates. Therefore, the operating temperature of the heat exchanger is appropriately increased, and the principle that light decay does not occur after the LED light source is operated for a long time is adopted. Can effectively reduce LED light decay. This design idea can not only reduce the amount and cost of the heat sink, but also increase the carrying capacity of the working current of the chip, and at the same time achieve the purpose of reducing the LED light decay and prolonging the service life, which is a design revolution with multiple wins.
First, flip chip no package technology
Recently, flip chip and no-package technology have caused widespread debate in the industry, because the traditional dressing process encounters technical bottlenecks such as heat dissipation and light decay. Flip-chip, no-package technology as early as 10 years ago, foreign companies invested heavily in research, aiming to avoid the use of substrate glue, grain soldering technology, not only can effectively reduce the thermal resistance of the package, but also completely eliminate the formal chip There are many drawbacks to the surface wire, so that the light source can withstand high temperatures and extend the life of the LED. The industry generally believes that this is definitely the cutting-edge technology in the field of packaging. But people have to ask: After years of research and experimentation, why is the flip-chip technology unable to replace the positive-loading chip technology and become the mainstream? The fundamental reason is that the flip-chip process depends not only on the ceramic substrate, but also on the aluminum (copper) substrate. The ceramic substrate is not as simple and convenient to process and install as the metal substrate. Since the solder is subjected to 280 degrees of high temperature, Inevitably damage the materials and components. Compared with the metal substrate, the ceramic substrate has a low reflectivity, and the transient light effect is difficult to increase. The thermal conductivity of the ceramic substrate and the limited contact area of â€‹â€‹the chip also limit the steady-state light effect. The flip-chip process twice soldered and the ceramic substrate + aluminum substrate double thermal resistance is enough to offset the above advantages. In addition, the equipment for hot-press welding and reflow soldering of the flip-chip process is extremely demanding, and the yield is unstable. From the perspective of the end user, a good LED should have better lighting quality, higher lighting performance, lower system cost and faster return on investment. Test the future of flip-chip technology is still (LM \ yuan) value. The quality is the first, the price is the king, so it has caused the user to wait and see, the product is difficult to promote the embarrassing situation.
Second, integrated COB packaging technology
In a sense, the core technology of LED packaging should be the development and manufacturing technology of packaged brackets, which determines the purpose, function and cost performance of LED light sources. Powerful companies are striving to solve the problem of heat dissipation, light efficiency, longevity and cost of LEDs by using packaged brackets.
Compared with single-chip packages, COB packages show many advantages in terms of light intensity, heat dissipation, light distribution, cost, etc., and more and more people believe that it is the future direction of LED development. At present, the conventional COB light source is a support in which an FR4 fiberboard is integrated into a body by an aluminum (or copper) substrate. Domestic FR-4 prepreg, thermal conductivity is only 0.3/mK, the best imported is only about 2.0 / mK, and the thermal conductivity of pure aluminum is 237 / mK, the difference between the two is more than 100 times, such a large heat consumption ratio, inevitably Increasing the thermal resistance of the system, causing severe LED light decay and reducing the service life, people have racked their brains to try to remove the insulating fiber of the aluminum substrate. However, no effective method has been found yet, such as some large companies designing the so-called "LMCOB bracket". (The copper substrate and the insulating layer are removed from the aluminum substrate), but it has not been popularized due to reasons such as equipment, gel, process and cost. In addition, the so-called "integrated light source" bracket is widely used in the market, and the electrode plate is embedded in the plastic of PPA (or EMC which is currently being promoted) by the injection molding process. Since the PPA is yellowed under high temperature and ultraviolet irradiation, Caused by ventilating water, the product has high failure rate. This kind of structure has a large amount of phosphor and gel because the electrode plate is 1.5mm higher than the chip. It not only increases the packaging cost, but also the thick colloid will affect the light transmission. Hardened cracks break the gold wire. At present, all COB supports have a dam structure without exception, so as to block the fluorescent mixed glue from overflowing. Because the dam glue and the surface white oil absorb light, the specular light reflection of the light source cannot be achieved. The above various reasons will affect the light intensity and Heat transfer is blocked, which is the main reason for the difficulty in improving the transient light efficiency and steady-state light efficiency of traditional COB light sources.
Third, the drive power technology
1. Integrated light source substrate and aluminum substrate do not need to achieve 3750V withstand voltage
In the LED system design, the most common problem is how to choose the driving power supply, but in fact the LED fails or is damaged, the driving power supply occupies a relatively high proportion, and the reliability and life of the driving power supply become the shortcomings of the LED lighting technology.
LED lighting is a general-purpose electronic product that must pass the corresponding national safety standards, that is, the LED lamp housing and human body contact does not pose an electric shock hazard. In general, LED drivers are non-isolated and isolated; non-isolated power supplies use fewer components and have higher efficiency, but are limited to use in housing insulation products, such as LED bulbs , where LEDs and drivers are integrated and sealed in Insulation plastic so that the end user is not at risk of electric shock. The isolated LED driver has an isolation transformer, meaning that the high voltage is isolated from the secondary LEDs and can be contacted directly by hand without electric shock. Isolated power supplies are larger, less efficient, and more costly than non-isolated power supplies.
Many people (including experts and professors) believe that the LED light source (pin) should have a voltage withstand voltage greater than the safety voltage (3750V). That is, the aluminum substrate and the ceramic substrate must meet the safety requirements for the heat resistance of the heat sink. In fact, this is a misunderstanding. Lack of electrical knowledge, experimental tests show that the breakdown voltage of the electrode to the ground (substrate) of the LED chip substrate after solidification by silver paste is only about 300V, and the voltage resistance of the LED chip substrate is far from the safety requirements. An isolated power supply must be used. Since the use of an isolated power supply aluminum substrate does not have to be 3750V withstand voltage, there is no need to leave a so-called "crawling distance". As the end user, whether using non-isolated power supply or isolated power supply, there is no need to require the aluminum substrate to reach 3750V insulation withstand voltage, because the input end of the non-isolated power supply is equipotential with the load, and it is not necessary to require the aluminum substrate to pass the safety voltage, aluminum The higher the substrate withstand voltage, the thicker the interlayer insulation, the higher the cost and the greater the thermal resistance. Practice has proved that most of the current COB aluminum substrates use thermoelectric separation package structure (the chip is directly bonded to the substrate) has been widely used, and the market is everywhere, which proves that this theoretical analysis is practical and feasible.
2. Can the LED driver power supply solve this short board with liquid cooling technology?
LED life can reach tens of thousands of hours, but the current matching power supply can not meet this requirement. In LED lighting products, failure is a common phenomenon, most of which is due to the failure of the power supply. Since many LED lighting application power supplies are enclosed in a small space, ventilation and heat dissipation become the main technical bottleneck. If there is no careful thermal design, LED And the power drive circuit is easily degraded or permanently disabled due to high temperatures. The key component that leads to the failure of LED driver circuit life is electrolytic capacitors. At present, the electrolytic capacitors manufactured by most domestic electrolytic capacitors have a specified life of 105 Â° C / 2000 hours, which means that the service life is only 105 Â° C. 84 days, even if it is reduced to 85 Â° C, the service life is only 332 days, less than a year! Far from meeting the LED drive requirements, why do electrolytic capacitors have temperature tolerance? The reason is that the electrolyte of the electrolytic capacitor needs to be manufactured by the "hydration" process. In order to achieve extremely low ESR, the simplest way is to increase the water content of the electrolyte. The boiling point of water is about 100 degrees, and the water content is high. Evaporation "dry" at high temperatures fails. Capacitor manufacturers have racked their brains to suppress the "hydration" reaction of high-water-containing electrolytes. Power supply manufacturers have also used glue-sealing processes to solve capacitor failures, but they are still incomplete.
The author immerses the driving power in the cooling liquid in the closed radiator cavity. Because the pressure difference between the internal and external electrolytic capacitors in the closed cavity is small, not only the explosion of the electrolytic capacitor is reduced, but also the evaporation "dry" is avoided. Since the glue is not impregnated, the disadvantages of the adhesive stress on the components and the maintenance of the components are avoided. The hermetic structure increases the water rating (up to IP68) and effectively extends the life of the power supply.
Semiconductor lighting is a technological revolution. When new technologies come out, it always needs a transition, and it will inevitably undergo long-term reform. From the perspective of the industry chain, there are many technical problems in LED chip technology, packaging technology, power supply technology, etc. Day, such as materials, equipment and supporting technology. Some of the problems are simple and unattended, such as the aluminum substrate withstand voltage problems have been fooled by the layman. Although the rapid development of such LEDs has replaced traditional lighting, people have a higher expectation for the future of LEDs: packaging chips into integrated circuits, no wires, no heat sinks, no drive power, long life, low cost targets. Will be achieved.
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