CN201255387Y - High power LED light source packaged by liquid dipping - Google Patents

Abstract

The utility model discloses a high-power LED light source packaged by liquid immersion, which comprises an LED chip, a packaging substrate, a cooling liquid, an optical window assembly, a casing, and a radiator; the radiator is provided with a casing, a packaging substrate, and a packaging An LED core 1 is arranged on the substrate, an optical window assembly is arranged on the top of the casing, and cooling liquid is filled in the casing. The LED chip is installed on the packaging substrate, the packaging substrate is installed on the radiator, the LED chip and the packaging substrate are immersed in the cooling liquid, and the cooling liquid is sealed in the negative pressure airtight space formed by the optical window assembly, the housing and the radiator to form condensation , Evaporation cycle. The light generated by the LED chip is emitted from the optical window assembly, and the heat is transferred to the sealing assembly and the radiator by the cooling liquid, which can effectively solve the problems of heat dissipation and light output of high-power LED light sources.

Description

High-power LED light source in liquid immersion package

technical field

The utility model relates to an illumination light source, in particular to a liquid-immersion packaged high-power LED light source.

Background technique

LED light source is a new generation of green lighting source. Its power consumption is only one tenth of that of ordinary incandescent lamps, but its life is more than ten times longer. In addition, LED light sources also have the advantages of small size, durability, and rich colors. In order to meet the requirements of higher light intensity, the LED light source is realized by increasing the output power of a single chip or using an LED array. Under ideal conditions, matching optical materials and appropriate packaging structures can give full play to the efficient light-emitting performance of LEDs and convert most of the electrical energy into light. However, temperature has a great influence on the output light intensity and color temperature performance of high-power LED light sources, especially the PN junction of LED chip works at high temperature for a long time, and its optical performance will decay quickly, which needs to be solved in LED packaging The key issue. In addition, LED chips are currently made of semiconductor materials such as GaN and sapphire. The refractive index of these materials is very high, and the light generated is not easy to emit into the air with a low refractive index. Therefore, it is necessary to select an appropriate refractive index material for matching. layer to improve the output efficiency of the light source.

At present, most packaging technologies for high-power LED packaging use high thermal conductivity materials as the substrate, and then use heat conduction or convection to remove heat from the substrate. On the light-emitting surface of the LED chip, epoxy resin or silica gel with a refractive index of about 1.5 is used as the optical output matching layer. The thermal conductivity of this material is very low and the thermal resistance is large, and the heat can hardly be lost. At present, the main method to improve the heat dissipation performance of LED light source is to improve the thermal conductivity and heat dissipation performance of the substrate, using high thermal conductivity materials, forced convection and other methods, such as patent 200520047169.9, which proposes to use a micro-jet flow device to cool the LED light source. Patent 200610060840.2 proposes a LED packaging method that immerses the chip in cooling liquid. This method needs to rely on liquid flow to take away the heat. In a small sealing structure, the fluidity of the viscous liquid is very poor, which affects the cooling effect. . In order to solve this problem, the patent proposes to use forced convection, but this increases the complexity of the system, and this method is not suitable for small-sized LED packages.

From the analysis of the heat generation characteristics of the LED light source, it can be seen that the bottleneck of heat dissipation of the LED chip is between the chip and the substrate. Due to the very small size of the LED chip, the contact area between the chip and the substrate is very limited, especially the flip-chip structure. There are multiple dielectric layers between the active area and the substrate, and the thermal resistance increases rapidly. For detailed analysis, please refer to the literature "Flip Chip High Power White LED Thermal Field Analysis and Test" (Optoelectronics Laser, vol.16, num.5, pp .511-514, 2005). In this way, the heat of the LED chip cannot be dissipated as soon as possible, resulting in a high temperature of the PN junction, and other optical materials such as epoxy resin, silica gel and fluorescent agent work at high temperature for a long time, and the performance of the entire light source device decays and ages quickly. The reliability is poor, and this packaging structure is difficult to apply to high-power LED light sources with high power density. How to adopt a better cooling method on the premise of low cost, so that the LED light source can work at a lower temperature, so as to obtain higher luminous efficiency, longer life, and higher reliability are the key points of this utility model. key issues to be resolved.

Contents of the invention

The purpose of the utility model is to overcome the deficiencies of the prior art and provide a high-power LED light source packaged in liquid immersion.

The high-power LED light source with liquid immersion packaging includes LED chips, packaging substrates, cooling liquid, optical window components, housings, and radiators; the radiators are provided with housings and packaging substrates, and the packaging substrates are provided with LED cores 1 and housings. The top of the body is provided with an optical window assembly, and the casing is filled with cooling liquid.

The optical window assembly includes a lens and an optical film doped with a fluorescent substance, and a lens is arranged on the optical film doped with a fluorescent substance. The cooling liquid is acetone, ethanol, freon or water. The inner wall of the casing is provided with an optical reflector. The radiator is a fin radiator or a heat pipe radiator. The inner walls of the shell and radiator are provided with capillary grooves for liquid return.

The utility model is composed of an LED chip, a packaging substrate, a cooling liquid, an optical window assembly, a casing and a radiator. The LED chip is installed on the packaging substrate, the packaging substrate is installed on the radiator, the LED chip and the packaging substrate are immersed in the cooling liquid, and the cooling liquid is sealed in the negative pressure airtight space formed by the optical window assembly, the sealing assembly and the radiator to form condensation , Evaporation cycle. The light generated by the LED chip is emitted from the optical window assembly, and the heat is transferred to the sealing assembly and the radiator by the cooling liquid, which can effectively solve the problems of heat dissipation and light output of high-power LED light sources.

Description of drawings

Figure 1 is a schematic structural diagram of a high-power LED light source packaged in liquid immersion;

Fig. 2 is the structural representation of the optical window assembly of the present utility model;

Fig. 3 is the structural representation of radiator of the present utility model;

In the figure: LED chip 1, packaging substrate 2, coolant 3, optical window assembly 4, sealing assembly 5, heat sink 6, lens 7, optical film 8 doped with fluorescent substance, capillary groove 9.

Detailed ways

The specific embodiment of the utility model will be described in detail below in conjunction with the accompanying drawings.

As shown in Figure 1, the high-power LED light source with liquid immersion packaging includes LED chip 1, packaging substrate 2, cooling liquid 3, optical window assembly 4, housing 5, and radiator 6; the radiator 6 is provided with housing 5 1. Packaging substrate 2, LED chip 1 is arranged on packaging substrate 2, optical window assembly 4 is arranged on the top of casing 5, and cooling liquid 3 is filled in casing 5.

The LED chip is fixed on the packaging substrate by welding and bonding. The packaging substrate is made of a material with high thermal conductivity, and the circuit required for chip connection is laid on it. The packaging substrate is fixed and installed on the radiator. A negative-pressure airtight space composed of an optical window assembly, a housing and a heat sink, and then filled with an appropriate amount of cooling liquid, the LED chip and the packaging substrate are completely immersed in the cooling liquid, and the cooling liquid is in the optical window assembly, housing and The evaporation and condensation cycle is formed in the negative pressure airtight space formed by the radiator. The housing is a container made of metal or other material, the inner wall of which can be made into an optical mirror to enhance the output of light in the optical window assembly. In order to enhance the heat dissipation effect, the radiator can increase the fins to expand the heat dissipation area or adopt radiators such as heat pipes.

Coolant evaporation needs to absorb a lot of heat, and the same amount of heat needs to be released during the condensation process. The most effective heat transfer method can be realized by using the coolant evaporation and condensation cycle. The heat pipe is a heat transfer device realized in this way. Its thermal conductivity is thousands of times that of copper. The basic idea of the utility model is to quickly take away the heat of the LED chip by utilizing the evaporation and condensation cycle of the cooling liquid. Use the optical window assembly, housing and radiator to form a closed space, then draw out the air in this closed space to form a negative pressure, and add an appropriate amount of cooling liquid into the closed space, because the cooling liquid is in the negative pressure closed space. The evaporation temperature is greatly reduced, so when the LED chip heats up, the cooling liquid quickly evaporates to form a gas, and the gas condenses into a liquid on the inner surface of the housing and radiator, and the liquid flows back to the vicinity of the LED chip through the capillary grooves provided by the housing and radiator It is vaporized again to form a cycle, which does not require any external power, but only requires a temperature difference between the LED chip, the housing, and the heat sink. This package has simple structure, high reliability, and heat transfer efficiency is much higher than heat conduction and heat convection.

The cooling liquid is acetone, ethanol, freon or water. The choice of cooling liquid is very important. The cooling liquid is a transparent one with electrical insulation, thermal stability, optical stability, refractive index between 1.3 and 1.8, and a boiling point lower than 180°, non-corrosive liquid to circuits and chips. This liquid will not cause a short circuit due to its electrical insulating properties. The transparency of the cooling liquid ensures that the light generated by the LED chip 1 will not be absorbed by the cooling liquid. The cooling liquid is optically stable, and it will not change its composition and performance when it is exposed to high-intensity blue light or ultraviolet light for a long time. Furthermore, choosing a cooling liquid with a high refractive index is beneficial to improve the efficiency of light output from the LED chip, but considering the efficiency of light output into the air, the refractive index of the cooling liquid should not be too high, and should be consistent with the refractive index of the material of the optical window assembly. Basically the same (this kind of optical material generally chooses glass or epoxy resin, and the refractive index is about 1.5). Considering that the refractive index of the cooling liquid has a certain range of variation with different components, the refractive index is selected between 1.3 and 1.8. In addition, the coolant must not have a corrosive effect on the circuit and chip materials. In addition, the coolant must have thermal stability, and it will not decompose or deteriorate under high temperature for a long time. In order to make the cooling liquid evaporate easily and achieve better heat transfer effect, the boiling point of the cooling liquid should not be too high, and at the same time, by adjusting the amount of the cooling liquid added, the boiling point of the cooling liquid in the negative pressure space can be controlled.

Since the LED chip mounted on the packaging substrate is immersed in the cooling liquid, most of the heat generated is directly taken away by the cooling liquid through evaporation and condensation cycles, and then the cooling liquid transfers the heat to the housing and the radiator for dissipation, and there is a small amount of heat generated by the cooling liquid. Part of the heat is dissipated through heat conduction from the package substrate to the heat sink. Compared with the traditional encapsulation method, the method disclosed in the utility model can cool the LED chip better. The reasons are as follows: (1) The evaporation and condensation cycle is a very effective heat transfer method, which can be cooled only with a very small temperature difference. Automatically forms a cycle, which effectively prevents the local temperature of the LED chip from being too high; (2) The LED chip is immersed in the cooling liquid, and the heat transfer area is larger than the contact area between the LED chip and the packaging substrate; (3) The cooling liquid has a very large heat capacity, The same amount of heat causes a much smaller temperature rise than in air.

As shown in FIG. 2 , the optical window assembly 4 includes a lens 7 and an optical film 8 doped with a fluorescent substance. The optical film 8 doped with a fluorescent substance is provided with a lens 7 . The function of the optical window assembly is to output light intensity, and adjust the characteristics of the output light according to actual needs. The optical window assembly is installed in the direction of the light-emitting surface of the LED chip. The lens can change the divergence angle of the output light beam, and the optical film doped with fluorescent substances can change the frequency distribution of the output light to realize different color light sources, such as white LEDs. The role of the optical film doped with fluorescent substances can also be realized by directly mixing fluorescent substances in the cooling liquid.

As shown in FIG. 3 , the inner wall of the radiator 6 is provided with capillary grooves 9 for liquid backflow. Such capillary grooves are arranged centripetally around the LED chip. In order to make the condensed cooling liquid flow back to the vicinity of the LED chips, porous capillary nets or capillary grooves need to be arranged on the inner walls of the housing and the heat sink. This structure has very small holes or grooves, and the cooling liquid will fill these holes and grooves due to capillary phenomenon. Using this capillary structure, the cooling liquid can flow back to the vicinity of the LED chip against the influence of gravity. Considering that the porous capillary net will scatter light, the utility model chooses to set capillary grooves on the inner walls of the housing and the radiator.

Claims (6)

1. A liquid immersion packaged high-power LED light source, characterized in that it comprises an LED chip (1), a package substrate (2), a coolant (3), an optical window assembly (4), a housing (5), a heat dissipation The heat sink (6) is provided with a housing (5), a packaging substrate (2), the packaging substrate (2) is provided with an LED chip (1), and the top of the housing (5) is provided with an optical window assembly (4), the casing (5) is filled with cooling liquid (3). 2. A liquid immersion packaged high-power LED light source according to claim 1, characterized in that said optical window assembly (4) includes a lens (7) and an optical film (8) doped with fluorescent substances A lens (7) is arranged on the optical film (8) doped with fluorescent substances. 3. A liquid immersion packaged high-power LED light source according to claim 1, characterized in that said cooling liquid (3) is acetone, ethanol, Freon or water. 4. A liquid immersion packaged high-power LED light source according to claim 1, characterized in that the inner wall of the casing (5) is provided with an optical reflector. 5. A liquid immersion packaged high-power LED light source according to claim 1, characterized in that said radiator (6) is a fin radiator or a heat pipe radiator. 6. A liquid immersion packaged high-power LED light source according to claim 1, characterized in that the inner walls of the housing (5) and the radiator (6) are provided with capillary grooves (9) for liquid backflow ).

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