KR20110109263A - The effective method on sic heat sink - Google Patents

Abstract

With the development of civilization, the shortening and shortening of electronic components are proceeding rapidly, and the heat generation of electronic components is inevitable. Heat dissipation of electronic components attached to a circuit board is a big problem directly related to the life of the device. In contrast, many materials having high thermal conductivity have been manufactured in a single system or in combination. Heat dissipation at relatively high temperatures is being carried out by many researchers, but it is not practical in terms of material cost. Therefore, the present invention has been invented an efficient heat sink manufacturing method that is inexpensive manufacturing cost and can provide an appropriate level of heat dissipation effect on the part.

Description

{The effective method on SiC heat sink}

The present invention has been devised to solve malfunctions, stoppages and slowdowns of equipment due to the increase in the amount of heat generated due to the reduction of the weight and the shortening of electronic devices. The heat sink manufactured by the present invention can be utilized as IC circuit or inverter of display products, CPU, chipset and PCB of settop box, CPU, chipset and LED array of notebook, high power LED for lighting and automobile, and other cooling devices. have.

The present invention relates to an efficient method for producing porous silicon carbide ceramics having efficient heat dissipation characteristics, small coefficient of thermal expansion, light weight, and suitable for use as a heat dissipation member such as a substrate, and a heat dissipation part using the same. In today's semiconductor industry and various electronic devices, the problems of device malfunction, operation failure, and speed decrease caused by an increase in heat generation are becoming important tasks. In order to solve this problem, a heat sink of high thermal conductivity has been conventionally used for this purpose. As a high thermal conductivity material, Cu, Al, and the like are used as metals, and as a nonmetal, AlN, SiC, BeO, and Carbon are used to prepare a single system or a composite. These materials exhibit excellent thermal conductivity of about 200 W / mK or more. However, the high cost of the material itself and the high cost in its manufacturing process have a disadvantage in that the efficiency is inefficient when applied to a large number of parts. In addition, single or composite heat sinks of metals are heavy, and the coefficient of thermal expansion is large, resulting in problems such as scratching the parts when used in contact with electronic parts. In the case of a ceramic heat sink, which is a nonmetal inorganic material, a lot of research is being carried out because of relatively light weight and high thermal conductivity. Accordingly, the present invention is focused on the fact that the heat dissipation characteristics are not merely a matter of pursuing only high thermal conductivity, but the heat dissipation temperature of the component is to be reduced. In other words, the heat generated from the electronic components is heat conduction through the heat sink, but when the release to the air is late, the heat remains inside the heat sink, and eventually the heat sink having high thermal conductivity does not utilize its characteristics. In the case of metals, the heat dissipation efficiency is low as about 0.3 to 0.5, and in the case of ceramics, in particular, SiC or C, heat dissipation characteristics of about 0.7 to 0.9 or more. By using the heat dissipation characteristics of these ceramic products, we tried to reduce the manufacturing cost by producing an efficient heat sink having excellent heat dissipation effect although it has not high thermal conductivity.

At present, in order to solve heat generation problems due to light and small size reduction and high directivity of electronic components, metal or metal-based ceramic composite materials having high thermal conductivity have been studied. Pre-formed inorganic fibers or inorganic particles to form a preform, and the composite in which the metal is pressurized or spontaneously pressured therein has a disadvantage of high raw material costs and expensive manufacturing processes. In addition, the manufacturing process requires a high-cost device in the manufacturing process because it must be produced in a reducing atmosphere or a vacuum atmosphere.

What is to be solved in the present invention was to manufacture a ceramic heat sink capable of efficient heat dissipation using a general ceramic manufacturing process (press, tape casting, injection, etc.). The ceramic heat sink made of ceramic is light and its coefficient of thermal expansion is similar to that of the chip, which does not scratch the electronic parts, and the manufacturing process is simple and the manufacturing equipment is simple.

The present invention is an invention for producing a heat sink having an efficient heat dissipation characteristics.

For example, in the press process, a binder, a dispersant, and other additives are mixed with SiC powder, and granulated powder is prepared by using a spray dryer. The manufactured granulated powder is molded to have a shape in a mold by using a mechanical or hydraulic press, and fired at about 1000 to 1600 ° C. in an air atmosphere. The manufactured sintered product can be used as a product without processing as much as possible, and if there is a problem with flatness, it is finished by simple machining so that the bottom is flat.

In the case of tape casting, the raw powder is mixed with a binder, a dispersant, a plasticizer, and the like in a mill. The mixed slurry is introduced into the doctor blade to produce a ceramic sheet, and when dried, it is cut to complete molding on a plate or passed through a grooved roll to give irregularities and cut to specifications to complete molding. The prepared sheet is fired at about 1000 ~ 1600 ℃ in the kiln to produce a heat sink. If you need machining for flatness as in the press process, do so.

In the case of injection molding, the raw material powder is hot mixed with an organic binder, a plasticizer and the like and injection molded. This molded body is subjected to a long time debinding process at low temperature and then fired at about 1000 to 1600 ° C. to produce a heat sink. When flatness is needed, it should be processed and flattened.

The above manufacturing process and the other heat sink manufacturing process are manufacturing methods that do not differ significantly from the general ceramic manufacturing process.

As a heat sink raw material, the SiC powder is preferably within several μm. If the particle size of SiC powder is too large, it is difficult to express the strength after firing, so that problems such as broken or chipping may occur when bonding the heat sink to the electronic component, and if it is too small, defects such as warping may occur during firing. A particle size of several tens of micrometers is suitable. In addition, since the heat dissipation mechanism is the most influential factor due to the thermal conduction (conduction), we tried to secure the heat conduction source to the finest particles. It is also possible to add dozens to hundreds of micrometers of SiC powder. This is because the firing of only the fine particles in the manufacturing process may cause more problems such as warpage, and since there are a large amount of voids between the fine particles, the addition of large particles reduces the voids and secures more conduction route. During firing, SiC powder combines with oxygen to form SiO ₂ on the surface and expresses the strength of the produced SiO 2 material product, but it is porous to reduce the heat conduction route.

Thus, powders mixed with several micrometers of silicon carbide alone or tens to hundreds of micrometers of silicon carbide up to 90wt% are molded by pressing, tape casting or injection molding and fired at about 1000 to 1600 ° C in air. . There is a slight difference in the firing temperature depending on the size of the particles, but when firing at 1000 ℃ or less, the interparticle strength is low, so that the ceramic particles fall off the ceramic heat sink, thereby adversely affecting the circuit. When baking at 1600 degreeC or more, it is unfavorable in a manufacturing facility etc., It is preferable not to exceed the temperature. As shown in the example of the present invention it can be confirmed that the thermal conductivity does not change significantly above a certain temperature.

The fired ceramic heat sink is superior to the conventional metal-based and metal-based ceramic composites. Conventional materials have a narrow specific surface area for heat dissipation, whereas SiC ceramic heat sinks fired in an air furnace have a very large heat dissipation area due to their pores. In other words, Al ₂ O ₃ (alumina) or other inorganic materials with high thermal conductivity are densified by diffusion, evaporation, and condensation during firing, but SiC fired in the atmospheric atmosphere is oxidized to SiO _{2. 2} is a material having a characteristic of not densifying upon firing. If it is not densified during firing, it has a large specific surface area on the surface, so it has great advantages in convection, the second route of the heat radiation mechanism, and radiation, the last third of the heat radiation mechanism.

In addition, when the surface of the manufactured ceramic heat sink is roughly treated using a machine such as sand blaster, the surface area determined by the shape of the heat sink is maximized, and the specific surface area is roughly maximized, which is very effective for heat dissipation characteristics.

The present invention was to produce an efficient ceramic heat sink using the fine SiC powder. By adding a certain amount of fine SiC powder, it is possible to secure a route source where thermal conduction can occur well, and by firing the SiC powder in the air, the surface of the SiC particles is oxidized to SiO ₂ to obtain bonding strength and densification of the SiO ₂ ceramic itself. It is a method of manufacturing an efficient ceramic heat sink that maximizes heat transfer and heat emission due to convection and radiation by forming a number of micropores on the surface by using a characteristic that is not possible.

The result of measuring the thermal conductivity of the product produced by each temperature by the present invention was measured as follows. It is a value using the laser flash method according to JIS standard.

No. Fine: Assembly rate Firing temperature
(℃) Thermal conductivity
(W / mK) One 50:50 1400 16.0 2 50:50 1500 21.6 3 70:30 1500 20.9 4 50:50 1600 21.6 5 70:30 1600 23.9

In the SiC heat sink manufactured by the present invention, the heat resistance of the heater itself, which is 18.0 ° C./W, was reduced to 10.0 ° C./W or less at an ambient temperature of 30 ° C. and a calorific value of 5.7 Watts.

FIG. 1 may be circular in shape of a general ceramic heat sink.
[Fig. 2] [Fig. 3] [Fig. 4] is an example for maximizing the specific surface area is a method of maximizing the specific surface area by changing the shape of the pin to increase the specific surface area or to bend the surface.
5 is a simple structural diagram of a device used to measure heat dissipation characteristics.

For the practice of the present invention it was tested using a TLS-M SOP tester manufactured by Thermolab Co. Thermolab Co. TLS-M is a device that applies ASTM-5470-06.

 The structure is shown in [Fig. 4] and the heater is 20 * 20 mm2 and has a thermal property similar to that of a CPU with a copper plate heater spread. The ambient temperature was set to 30 ℃ and the calorific value of 5.7Watt. At this time, the surface temperature of the heater was 106.39 ℃ and the heat resistance was 18.0 ℃ / W. In addition, the thermal tape used in the test was 3M Co. 0.8W / mK (0.25t) products.

Example Amount of fine SiC (wt%) Amount of Granulated SiC (wt%) Other minerals
Type / Quantity Organic binder volume
(wt%) standard Heat resistance
(℃ / W) heater surface temperature (℃) Remarks Example 1 - - - - - 18.0 106.39 reference Example 2 50 50 - 1.5 40 * 40 * 3t 9.61 77.36 1450 ℃ Sintered Example 3 50 50 - 1.3 40 * 40 * 3t 9.43 76.66 Example 4 - - SiC / 100 3 40 * 40 * 3t 12.06 86.78 175 W / mK Example 5 50 - C / 50 1.5 40 * 40 * 3t 9.75 77.84 porous Example 6 50 50 - 1.5 40 * 40 * 3t 10.83 82.03 1600 ℃ sinter Example 7 50 50 - 1.5 40 * 40 * 3t 9.28 76.02 C coating

Example 1 is a reference to a value measured by the temperature of the heater surface without the heat sink. Example 2 and Example 3 are the measurement results of the product 50:50 ratio of the sintered granules and granulation at 1450 ℃, the heat resistance value was measured to 9.61 and 9.43. In Example 6, the influence of the denser surface, that is, the effect of heat transfer by convection and radiation was evaluated. The thermal resistance at this time is 10.83, it can be seen that the thermal resistance further increased compared to Example 2. In Example 5, the effect of reducing the heat conduction route source by adding 50% carbon was evaluated. Thermal conduction route sources are reduced but appear to be compensated by convection and radiation. Example 4 showed the heat dissipation characteristics of the material having a pore of 0.5% or less and a thermal conductivity of 175 W / mK. It is a dense material and its thermal conductivity is very high, but its specific surface area is very low compared to Examples 2 and 3, resulting in a lack of convection and radiation, and thus the thermal resistance was measured at 12.06 ° C / W. In Example 7, the heat resistance of the product coated with carbon fiber having high heat dissipation efficiency on the surface of Example 2 was measured at 9.28 ° C / W.

Based on the above results, it can be seen that the heat dissipation efficiency of a material having a relatively low thermal conductivity of about 10 to 30 W / mK has a greater effect on the heat dissipation efficiency than the high thermal conductivity.

Claims (4)

In the method of manufacturing an efficient SiC heat sink,
Using SiC powder of several micrometers or less, it is molded by press, tape casting, ceramic injection molding, etc., which is a general method of manufacturing ceramic products, and fired in an oxidizing atmosphere, and thermal conductivity is 3 ~ 150W / mK, more preferably 5 ~. Efficient Silicon Carbide Heat Sink Manufacturing Method to Have 100W / mK In the method of manufacturing an efficient SiC heat sink,
SiC powder with an average particle diameter of several micrometers or less is mixed with one or two or more kinds of SiC powder having a particle size of 10 to 500 μm or 90 wt% or less, and more preferably 30 to 80 SiC powder having an average particle diameter of about 10 to 200 μm. Method for producing an efficient silicon carbide heat sink, characterized in that the addition of about%
In the method of manufacturing an efficient SiC heat sink,
To the SiC powder with average particle diameter of several micrometer or less, carbon or organic substance is added 70wt% or less, more preferably 50% or less as pore-forming agent, so that the porosity is 50% or less, increasing the specific surface area on the surface and heat emission Efficient silicon carbide heat sink manufacturing method characterized by having a structure that can be In the method of manufacturing an efficient SiC heat sink,
Efficient silicon carbide heat sink manufacturing method characterized by coating the carbon fiber with excellent heat dissipation efficiency and having a large specific surface area or sand blasting the surface to maximize specific surface area so that heat dissipation can occur well

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