CN102339945A - High-power light-emitting diode with diamond powder-copper powder composite material as heat dissipation substrate - Google Patents

Abstract

The invention discloses a high-power light-emitting diode (LED) with a cooling substrate made of a diamond powder-copper powder composite, and the LED provided by the invention comprises an LED chip, a lens and the cooling substrate made of the diamond powder-copper powder composite, wherein the lower surface of the cooling substrate is directly contacted with the air, the upper surface of the cooling substrate is provided with a concave pit, and the LED chip is directly placed at the bottom of the concave pit on the upper surface of the cooling substrate by using a solid crystal adhesive or through metal eutectic soldering; the inside of the concave pit is filled with an insulating elastic transparent substance, and the insulating elastic transparent substance covers the whole LED chip and leading wires thereof; and the lens covers the concave pit. The composite can extract heat from the high-power LED according to the shortest path and directly discharge heat to the air. Because the thermal conductivity of the composite is large, through combining with an optimized structure design, the composite can be used for cooling a single high-power LED and an LED module, thereby achieving the purpose of enhancing the light output power and prolonging the service life of the LED.

Description

High-power light-emitting diode with diamond powder-copper powder composite material as heat dissipation substrate

technical field

The invention relates to the technical field of LED inventions, in particular to a high-power LED that directly uses a diamond powder-copper powder composite material as a heat dissipation substrate.

Background technique

In the past when LEDs could only be used as status indicator lights, heat dissipation in their packaging was never a problem. However, in recent years, the brightness and power of LEDs have been actively improved, and they have begun to be used in applications such as backlighting and electronic inventions. The problem has arisen. If the doubled current is fed into the same single package, the heat generation will naturally be doubled, so the heat dissipation will of course worsen. For example, because white LEDs are to be used as flashlights for camera phones, light bulbs for small inventions, and light bulbs for inventions in projectors, high brightness is not enough, and high power is also required. This is where heat dissipation becomes a problem. What's more, in the backlight of LCD TVs, high-brightness LEDs are used, and they must be arranged densely. In order to pay attention to shortness and thinness, the available heat dissipation design space on the back is more restricted, and it should not be used if high standards are required. Use a cooling fan, because the noise of the fan will affect the taste of watching TV. If the heat dissipation problem is not solved, the heat of the LED cannot be dissipated, and the operating temperature of the LED will rise. Will it have any impact? There are two main effects on this: (1) weakening of luminous brightness, and (2) attenuation of service life. Most of the existing high-power LED chip packaging materials are aluminum substrates and co-fired ceramic substrates, which cannot meet the heat dissipation requirements. In addition, the existing packaging structures still need to be improved a lot.

Contents of the invention

The technical problem to be solved by the invention is to overcome the heat dissipation problem of the existing LED chips, and provide a high-power light-emitting diode with a diamond powder-copper powder composite material as a heat dissipation substrate. The present invention is mainly realized through the following technical solutions.

The heat dissipation substrate is a high-power light-emitting diode made of diamond powder-copper powder composite material, including LED chips, lenses and a heat dissipation substrate made of diamond powder-copper powder composite material; the lower surface of the heat dissipation substrate is directly in contact with the air, and the upper surface is set There are pits, and the LED chip is directly placed on the bottom of the pit on the upper surface of the heat dissipation substrate through crystal-bonding glue or metal eutectic welding; the pit is filled with an insulating elastic transparent substance, and the insulating elastic transparent substance covers the entire LED chip and Its lead wire, the lens cap is on the dimple. the

As a further optimized technical solution for high-power light-emitting diodes in which the heat dissipation substrate is a diamond powder-copper powder composite material, the lower surface of the heat dissipation substrate is provided with electrodes, and the pits are provided with perforations that penetrate to the lower surface of the heat dissipation substrate. The leads are connected to the electrodes on the lower surface of the heat dissipation substrate through the through holes.

As a further optimized technical scheme for high-power light-emitting diodes in which the heat dissipation substrate is a diamond powder-copper powder composite material, a circuit layer is provided on the upper surface of the heat dissipation substrate except the pit, and the circuit layer is adhered to the surface through an adhesive layer. On the upper surface of the heat dissipation substrate, the leads of the LED chip are connected to the electrodes on the circuit layer.

As a technical solution for further optimization of the high-power light-emitting diode in which the heat dissipation substrate is a diamond powder-copper powder composite material, the lower surface of the heat dissipation substrate is processed into heat dissipation fins.

As a further optimized technical solution for high-power light-emitting diodes in which the heat dissipation substrate is a diamond powder-copper powder composite material, the lens covers the LED chip and its leads.

As a technical solution for further optimization of the above-mentioned high-power light-emitting diode whose heat dissipation substrate is a diamond powder-copper powder composite material, the insulating elastic transparent substance is silica gel.

As a further optimized technical solution for high-power light-emitting diodes in which the heat dissipation substrate is a diamond powder-copper powder composite material, phosphor powder is doped in the insulating elastic transparent substance.

As a technical solution for further optimization of the high-power light-emitting diode whose heat dissipation substrate is a diamond powder-copper powder composite material, a plurality of LED chips are placed in the pit.

As a further optimized technical solution for high-power light-emitting diodes in which the heat dissipation substrate is a diamond powder-copper powder composite material, the diamond powder-copper powder composite material is prepared by the following method: superhigh thermal conductivity diamond powder particles of 200 to 300 mesh Mix with high thermal conductivity copper powder 300~400 mesh particles, in which the volume ratio of diamond is 40%~60%, use the method of magnetron sputtering to coat the transition group with a mass ratio of 0.1%~0.3% on the surface of the mixed particles Metal, the transition group metal includes chromium, titanium or molybdenum; put the processed mixture into a mold, and then sinter it in a plasma vacuum high-pressure sintering furnace. 20~40MPa, sintering time 10~15min; the composite material after sintering is subjected to hot isostatic pressing under argon atmosphere, the pressure is 150~200MPa, the temperature is 1000~1040°C, and the heat preservation is 3~4h to obtain the diamond powder -Copper powder composite.

As a further optimized technical solution for high-power light-emitting diodes in which the heat dissipation substrate is a diamond powder-copper powder composite material, the thermal conductivity of the ultra-high thermal conductivity diamond is 2000 W/m.K, and the thermal conductivity of the high thermal conductivity copper powder is 2000 W/m.K. It is 400 W/m.K.

The heat dissipation substrate of the present invention is made of diamond powder and copper powder through high-pressure sintering, which can be made into different sizes and shapes, increases the contact area between the heat dissipation substrate and air, forms convective heat dissipation, and enhances heat dissipation effect. The circuit layer and the adhesive layer do not cover the entire surface of the heat dissipation substrate, and the heat dissipation substrate is exposed under and near the LED chip, and the LED chip is directly connected to the heat dissipation substrate through silver glue or metal eutectic welding. The heat of the LED chip is directly radiated to the air through the heat dissipation substrate, so that the heat transfer path is very short and the heat transfer efficiency is greatly improved. Moreover, combined with the excellent thermal properties of the heat dissipation substrate itself, the rise of the junction temperature of the LED chip will be greatly suppressed. The LED chip is surrounded by a reflective cup, which reflects the lateral light. The reflective cup is made of high thermal conductivity material, such as diamond-copper powder composite material, so that there is a horizontal heat dissipation effect. A lens is covered above the reflecting cup, and the structure of the lens corresponds to the outgoing angle of the light.

Compared with the prior art, the present invention has the following advantages and technical effects:

1) The present invention uses a diamond powder and copper powder composite material as the heat dissipation substrate of the LED chip, and processes fins and pits on the substrate at the same time.

2) In the present invention, the composite material of diamond powder and copper powder is perforated, and the electrode is placed at the bottom of the heat dissipation substrate, and a pit is designed on the upper surface of the heat dissipation substrate. The LED chip is placed in the pit, and the pit has the function of a reflective cup. Moreover, LED chips can be flip-chip packaged.

3) The LED chip of the present invention is directly bonded on the composite material of diamond powder and copper powder, and there is no small metal heat sink block between the two. Moreover, the heat dissipation substrate does not need to be placed on other types of heat dissipation substrates.

4) In the further optimized technical solution of the present invention, the diamond powder-copper powder composite material prepared under specific parameters has high thermal conductivity, which is far higher than that of existing aluminum, co-fired ceramics and other materials Rate. Secondly, the surface of the diamond powder and copper powder composite material is very rough, which increases the contact area between the composite material and air and enhances convective heat radiation. Again, this composite material is a block structure that has particles, so it is easy to make various required structures. These features are beneficial to using this composite material as a heat dissipation device for an LED lighting device. Undoubtedly, an LED lighting device with a good heat dissipation effect can be obtained. On the one hand, the application field of the composite material is expanded, and on the other hand, the heat dissipation device can be applied to different LED application occasions.

In short, on the basis of using a composite heat dissipation substrate of diamond powder and copper powder, the present invention changes the packaging structure of the LED chip, provides an optimized design scheme from the perspectives of heat conduction paths and heat dissipation plates to air heat dissipation, and effectively solves the problem of high-power LEDs due to a large number of power generation issues. Problems of brightness reduction and life shortening caused by heat. Taking effective heat dissipation as the main goal while taking into account the luminous characteristics can provide assistance for the invention of LEDs for different applications.

Description of drawings

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments.

Fig. 1 is a sectional view of a first embodiment of the present invention. the

Figure 2a is a cross-sectional view of a second embodiment of the present invention.

Fig. 2b is a cross-sectional view of the heat dissipation substrate of the second embodiment of the present invention.

Fig. 3 is a sectional view of a third embodiment of the present invention.

Fig. 4a is a sectional view of a fourth embodiment of the present invention.

Figure 4b is a bottom view of a fourth embodiment of the present invention.

Illustration of the present invention:

11 heat dissipation substrate; 2 adhesive layer; 3 circuit layer; 4 solid crystal glue; 5 lead wire; 6LED chip;

7 lens; 8 elastic transparent substance; 9 lower surface electrode; 111 fin; 112 pit; 113 perforation.

Detailed ways

Referring to Figures 1 to 4, the present invention provides a preferred embodiment of a high-power LED packaging structure using a diamond powder-copper powder composite material as a heat dissipation substrate, but the implementation and protection scope of the present invention are not limited thereto.

As shown in Figure 1: the upper surface of the heat dissipation substrate 11 made of diamond powder and copper powder composite material has a pit 112 in the center, and the LED chip 6 is directly placed on the bottom surface of the pit 112 through the crystal bonding glue 4, and the pit 112 Corresponding to a reflective cup, the surface of the pit 112 has a highly reflective material, such as polymer, metal silver, aluminum, etc., to emit the light from the side of the LED chip 6 . Fill elastic transparent material 8 in the pit, usually use silica gel, silica gel has many advantages, and its refractive index is big; Can not turn yellow; Keep gel. The elastic transparent substance 8 can also be mixed with fluorescent substances to play a role in wavelength conversion, such as converting blue light into yellow light, and finally synthesize white light. A light-diverging medium may also be added to the elastic transparent material 8 to change the light field distribution of the outgoing light. The elastic transparent material is covered with lens 7. The shape of the lens can be changed according to the requirements of different light exit angles. The lens 7 can be made of elastic plastic, glass, resin, acrylic and other materials. There is an adhesive layer 2 and a circuit layer 3 on the heat dissipation substrate; both the adhesive layer 2 and the circuit layer 3 have holes in the center, and the positions of the holes correspond to the positions of the LED chips 6 . The adhesive layer 2 is a highly thermally conductive insulating substance, such as epoxy resin, or glue filled with carbon nanofibers. The circuit layer 3 supplies external electricity to the LED chip 6 through the gold wire 5 .

Diamond is the material with the highest thermal conductivity. It uses phonons to transfer heat, and its thermal conductivity can reach 2000W/m.K; the linear thermal expansion coefficient of diamond can be as low as 1.2ppm/K. The thermal conductivity of copper is among the best among metals, with a value of 397W/m.K and a thermal expansion coefficient of 18ppm/K. The thermal conductivity of the composite heat dissipation substrate made by filling copper in the gaps of diamond particles by using the ductility of copper material can reach 800W/m.K, and the thermal expansion coefficient is about 5ppm/K. This material is most suitable for making substrates for high-power semiconductor chips and heat-conducting materials, such as heat-dissipating substrates for LED chips in the present invention. In addition to high thermal conductivity, the thermal expansion coefficient of the diamond-copper composite sheet can be adjusted to be close to that of the semiconductor chip to avoid damage to the semiconductor chip by thermal stress. From the perspective of heat dissipation from the heat dissipation substrate to the air, the contact area between the heat dissipation substrate and the air and the convection heat dissipation method are extremely important, and the surface of the diamond powder and copper powder composite heat dissipation substrate is already very rough without additional processing. Thermal conductivity is very beneficial; from a structural point of view, diamond powder and copper powder composite heat dissipation substrates are easy to shape, because the shape of the final heat dissipation substrate changes according to the shape of the mold, unlike metal substrates Complex processes such as punching and cutting are required. This advantage makes the diamond powder and copper powder composite heat dissipation substrate more effectively coupled with the LED chip. the

The manufacturing method of the heat dissipation substrate 11 is to combine ultra-high thermal conductivity diamond (2000 W/m.K) 200-300 mesh powder particles and high thermal conductivity copper powder 300-400 mesh (400 W/m.K) particles by (proportioned by volume, The volume ratio of diamond is 40%~60%) mixed, because the wettability of diamond and copper is not good, the surface of diamond powder is treated with surface metallization, and the mass ratio of coating on the particle surface by magnetron sputtering is 0.1%~ 0.3% transition metals such as chromium, titanium, molybdenum. The surface metallization treatment is beneficial to improve the grain boundary wettability of copper powder and diamond powder in the later powder sintering process. We put the mixed material into the pre-made mold. The shape of the mold can be changed according to the demand, and then sintered in the plasma vacuum high-pressure sintering furnace. The heating time is 10~15min, the temperature reaches 1000~1050℃, and the pressure is 20~40MPa. The sintering time is 10~15min. The composite material after sintering is subjected to hot isostatic pressing under an argon atmosphere, the pressure is 150~200MPa, the temperature is 1000~1040℃, and the heat preservation is 3~4h. Further, chemical bonds are formed between metal atoms and carbon atoms at the grain boundaries, and the two are organically combined to minimize the number of voids. Because diamond conducts heat by phonons, the voids cause a large thermal resistance. In this way, a dense block diamond powder-copper powder composite material is prepared. We can machine the heat dissipation substrate we want, and if the mold in the previous process is done properly, there is no need for machining steps. We adjusted the experimental data to obtain diamond powder copper powder composites with different thermal conductivity. The data table of the experimental results is shown in Table 1, in which the diamond is 200 mesh, and the copper powder is 300 mesh.

Table 1

experiment Ratio (diamond volume percentage) Sintering temperature (°C) Pressure (MPa) Sintering time (min) Thermal conductivity (W/m.K) Experiment 1 40 1010 20 10 513 Experiment 2 40 1030 30 10 525 Experiment 3 40 1040 40 10 517 Experiment 4 50 1010 30 10 533 Experiment 5 50 1030 40 10 547 Experiment 6 50 1040 20 10 482 Experiment 7 60 1010 40 10 606 Experiment 8 60 1030 20 10 589 Experiment 9 60 1040 30 10 734

As shown in FIG. 2 a : the structure is the same as that of the substrate in FIG. 1 , the difference is that heat dissipation fins 111 are formed on the lower surface of the heat dissipation substrate 11 . When the LED is working, the heat is radiated downward through the heat dissipation substrate to the air through the heat dissipation fins, and can also be dissipated by the side of the heat dissipation substrate like air. Here, fins or other roughened patterns can also be processed on the side of the heat dissipation substrate to enhance air convection heat dissipation.

As shown in FIG. 2 b : the structural diagram of the heat dissipation substrate 11 , there are pits 112 on the upper surface, and heat dissipation fins 111 on the lower surface. The size and arrangement of the heat dissipation fins can be changed according to requirements. This greatly simplifies the packaging structure, using the same diamond powder and copper powder composite material, processing integrated processing, to make a shape that integrates the heat dissipation substrate, fins, and reflective cups, which simplifies the LED packaging process and reduces the batch size. The cost of production. Another important advantage is reflected in the performance of the LED. Using the structure in the figure to package the LED chip 6, the heat conduction path is very short, that is, the LED chip 6, the die-bonding glue 4 to the heat dissipation substrate to the air, and there is no other medium in between. In addition to the higher thermal resistance of die-bonding glue 4, in addition to silver glue, gold-tin alloy can also be used for die-bonding. In order to reduce thermal resistance, it is better to use gold-tin eutectic soldering. There are no small pieces of heat-dissipating metal, and no other heat-dissipating materials, so the heat conduction effect must be good.

As shown in FIG. 3 : the structure is the same as that of the substrate in FIG. 2 a , the difference is that a plurality of LED chips 6 are placed in the cavity 112 . The LED chip 6 can send light of the same wavelength or light of different wavelengths, not as good as red, green and blue. Or a combination of yellow light and blue light. The depth of the pit 112 and the inclination angle of the sides, as well as the arrangement of the LED chips inside can be adjusted to change the light distribution curve of the emitted light.

As shown in FIG. 4 a , there is a pit 112 above the heat dissipation substrate 11 , and the LED chip is placed on the bottom surface of the pit 112 . There is a perforation 113 in the center of the pit 112 , and there is a wire in the perforation 113 , which supplies power to the LED chip 6 through the electrodes on the lower surface of the heat dissipation substrate 11 . The inner surface of the pit 112 has the reflective coating, and the pit 112 is equivalent to a reflective cup. The perforations in the figure can be more than two, such as four, and more than one LED chip 6 can also be placed in the pit in the figure. In addition, in this structure, the flip-chip packaging method of the LED chip can be used. In this case, the lead 5 can be omitted, because in this case, the two electrodes of the chip are very close to the through hole, and only the position of the through hole can be adjusted. The two electrodes can then be connected to the perforated positions with thermally and electrically conductive adhesive.

As shown in Fig. 4b: The external circuit supplies power to the LED chip through the electrode 9 on the lower surface, and then through the through hole 113, where the number of through holes can be more than two, and the corresponding lead wires 5 can also be more than two. Integrated packaging of multiple LED chips can also be considered.

Claims (10)

1. The heat dissipation substrate is a high-power light-emitting diode made of diamond powder-copper powder composite material, including LED chips (6) and lenses (7), and is characterized in that it also includes a heat dissipation substrate (11) made of diamond powder-copper powder composite material The lower surface of the heat dissipation substrate (11) is directly in contact with the air, and the upper surface is provided with a pit (112), and the LED chip (6) is directly placed on the heat dissipation substrate (11) through the solid crystal glue (4) or metal eutectic welding. ) bottom of the pit (112) on the upper surface; the pit (112) is filled with an insulating elastic transparent substance (8), and the insulating elastic transparent substance (8) covers the entire LED chip (6) and its leads, lens (7) Cover over the pit. 2. According to claim 1, the high-power light-emitting diode whose heat dissipation substrate is a diamond powder-copper powder composite material is characterized in that electrodes are provided on the lower surface of the heat dissipation substrate (11), and the pits are opened to penetrate to the heat dissipation substrate ( 11) The perforation on the lower surface, the leads of the LED chip (6) are connected to the electrodes on the lower surface of the heat dissipation substrate (11) through the perforation. 3. According to claim 1, the heat-dissipating substrate is a high-power light-emitting diode made of diamond powder-copper powder composite material, characterized in that, the upper surface of the heat-dissipating substrate except the pit is provided with a circuit layer (3), and the circuit The layer (3) is adhered to the upper surface of the heat dissipation substrate through the adhesive layer (2), and the leads of the LED chip (6) are connected to the electrodes on the circuit layer (3). 4. The high-power light-emitting diode whose heat dissipation substrate is a diamond powder-copper powder composite material according to claim 1, wherein the lower surface of the heat dissipation substrate (11) is processed into heat dissipation fins (111). 5. The high-power light-emitting diode whose heat dissipation substrate is a diamond powder-copper powder composite material according to claim 1, wherein the lens (7) covers the LED chip (6) and its leads. 6. The high-power light-emitting diode whose heat dissipation substrate is a diamond powder-copper powder composite material according to claim 1, wherein the insulating elastic transparent substance (8) is silica gel. 7 . The high-power light-emitting diode whose heat dissipation substrate is a diamond powder-copper powder composite material according to claim 1 , wherein phosphor powder is doped in the insulating elastic transparent substance ( 8 ). 8. According to any one of claims 1 to 7, the heat dissipation substrate is a high-power light-emitting diode made of diamond powder-copper powder composite material, characterized in that a plurality of LED chips (6) are placed in the pit (112) . 9. According to any one of claims 1 to 7, the heat dissipation substrate is a high-power light-emitting diode made of diamond powder-copper powder composite material, characterized in that the surface of the pit (112) has a highly reflective substance. 10. According to any one of claims 1 to 7, the heat dissipation substrate is a high-power light-emitting diode of a diamond powder-copper powder composite material, wherein the diamond powder-copper powder composite material is prepared by the following method: Thermally conductive diamond powder particles of 200~300 mesh and high thermal conductive copper powder particles of 300~400 mesh are mixed, and the volume ratio of diamond is 40%~60%. The mass ratio of the mixed particle surface is coated by magnetron sputtering. 0.1%~0.3% transition group metals, the transition group metals include chromium, titanium or molybdenum; put the processed mixture into a mold, then place it in a plasma vacuum high pressure sintering furnace for sintering, and the heating time is 10~15min , the temperature reaches 1000~1050℃, the pressure is 20~40MPa, and the sintering time is 10~15min. 3 to 4 hours to obtain the diamond powder-copper powder composite material.

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