KR101742063B1 - Silicon Carbide Heatsink and Manufacturing Method Thereof - Google Patents

Abstract

The present invention relates to a method of manufacturing a silicon carbide heat sink, comprising: mixing a silicon carbide (SiC) powder and a binder to produce a mixture; Drying the mixture to prepare granules; And forming a heat sink from the granulated material through a molding process.
According to the manufacturing method of the present invention, it is possible to manufacture a heat sink having low shrinkage, low-temperature firing, and little change in size and shape by using silicate as one component of the binder and having a low energy consumption.

Description

Technical Field [0001] The present invention relates to a silicon carbide heat sink,

The present invention relates to a silicon carbide heat sink and a method of manufacturing the same, and more particularly, to a silicon carbide heat sink having a large heat dissipation coefficient, a small thermal expansion coefficient, a light weight and excellent heat resistance.

In recent years, semiconductor devices and parts of various electronic devices have been directly and miniaturized, and as a result, the amount of heat generated increases. Therefore, problems such as shortening the service life of the devices using the devices, malfunctioning of the devices, .

In order to solve such a problem, a heat-radiating plate of a highly heat conductive metal or graphite and a composite thereof has been conventionally produced and used. M-Cu, m-Al and their alloys are used as the high thermal conductive metal materials, and a single system or composite is manufactured by using AlN, SiC, BeO, Carbon or the like as a non-metal heat dissipating member.

In addition, heat sink materials are being developed through the mixing of metals and non-metals. These materials exhibit excellent thermal conductivity with a thermal conductivity of about 100 W / mK or more. However, since the material cost is high and the manufacturing cost is high, there is a disadvantage in that the efficiency is low in terms of cost when applied to a large number of parts. Particularly, metal has electric conductivity as well, so a complementary measure is needed for actual use. In addition, a single system or a composite heat sink of a metal is heavy and has a large thermal expansion coefficient, which causes problems such as scratching or tearing of components when they are used in contact with electronic components.

Therefore, a ceramic heat sink, which is a nonmetallic inorganic material, has been developed, and has attracted much attention because it is relatively light and exhibits high thermal conductivity.

The reasons why these non-metallic materials are used as heat-insulating materials are as follows. That is, the heat generated from the electronic component is transmitted through the heat sink through the heat sink. When the heat is released to the atmosphere, the heat is left in the heat sink. Therefore, You will not be able to use it. This phenomenon is called the heat accumulation phenomenon.

In the case of metals, heat dissipation efficiency is as low as about 0.3 ~ 0.5. In the case of non-metal ceramics, the nonmetallic inorganic material has an advantage compared with metal because it is about 0.7 ~ 1.0.

In particular, SiC or C has a heat release characteristic of about 0.8 to 0.9 or more. By using the heat emission characteristics of such a ceramic product, it is possible to manufacture an effective heat sink having an excellent heat conductivity although not having a high thermal conductivity.

An example of a silicon carbide material that can be used for a heat sink is Korean Patent Registration No. 10-1334640. In the prior art, at least one alkaline earth metal oxide selected from among alkaline earth metal oxides, preferably BaO, SrO, CaO and MgO used as an additive reacts with silicon dioxide to form barium silicate, strontium silicate, calcium silicate, magnesium The effect of improving the high-temperature strength, durability and oxidation resistance of silicon oxycarbide-bonded silicon carbide is obtained by forming a silicate such as silicate.

The use of such a silicate may have the effect of reducing shrinkage in the production of heat sink using silicon carbide.

On the other hand, in Korean Patent Laid-Open Publication No. 10-2011-0023799, the mechanical strength, porosity and specific surface area characteristics of the heat sink are improved by combining silicon carbide and an inorganic material having a lower melting point than silicon carbide.

Korean Patent Publication No. 10-1334640 Korean Patent Publication No. 10-2011-0023799

SUMMARY OF THE INVENTION The present invention has been conceived in view of the above-described prior art, and provides a manufacturing method capable of manufacturing a heat sink of silicon carbide without shrinking by solving the problem of shrinkage at high temperature firing when a heat sink is manufactured using silicon carbide The purpose of that is to do.

It is another object of the present invention to provide a method of manufacturing a heat sink which does not require a further shrinkage of ceramic during processing and which can improve production efficiency and lower the firing temperature.

According to another aspect of the present invention, there is provided a method of manufacturing a silicon carbide heat sink, comprising: preparing a mixture by mixing silicon carbide (SiC) powder and a binder; Drying the mixture to prepare granules; And forming a heat sink from the granulated powder through a molding process.

In this case, the silicon carbide powder may be a mixed powder of powders of 400 mesh or less and powders of 250 mesh or less.

Further, the binder is a mixture of a resin and a silicate.

At this time, the resin may be any one or more of polyvinyl alcohol (PVA) and methyl cellulose (MC), and the silicate may be any one of sodium silicate, lithium silicate, barium silicate, strontium silicate, calcium silicate, .

A method of manufacturing a heat sink according to the present invention is a method of manufacturing a heat sink made of silicon carbide without shrinking by solving the problem of shrinkage at high temperature firing by using silicate as one component of a binder in manufacturing a heat sink using silicon carbide .

Further, since the ceramic shrinkage phenomenon does not occur during processing, further processing is unnecessary, the production efficiency is improved, and the firing temperature is lowered.

FIG. 1 is an electron microscope photograph (a) of a fracture surface of a heat sink manufactured according to the manufacturing method of the present invention and an energy dispersive spectroscopic analysis (EDS) result of the observed region.
Fig. 2 (b) is an electron microscope photograph (a) showing a fracture surface of a commercially available heat sink and an energy dispersive spectroscopic analysis (EDS) of the observed region.
Fig. 3 is a schematic view of a test apparatus for evaluating the heat dissipation characteristics of the heat dissipation plate manufactured by the manufacturing method of the present invention, and is a schematic diagram of the test apparatus of the heat dissipation plate non-installed state (a) and the heat dissipation plate installed state (b).
4 is a graph illustrating thermal characteristics of a heat sink manufactured according to the manufacturing method of the present invention.
5 is a graph showing a thermal property evaluation of a commercially available heat sink.

Hereinafter, the present invention will be described in more detail. The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

A method of manufacturing a silicon carbide heat sink of the present invention comprises the steps of: preparing a mixture by mixing silicon carbide (SiC) powder and a binder; Drying the mixture to prepare granules; And forming a heat sink from the granulated powder through a molding process.

Currently, the research direction of heat sink is focused on the development of composite material of metal or metal and ceramic with high thermal conductivity in order to solve heat problem due to light weight, thin layer and high directivity of electronic parts.

However, composites in which inorganic fibers or inorganic particles are preformed to form a preform and the metal is pressurized or pressurized by natural pressure have high disadvantages due to expensive raw material costs and expensive manufacturing processes. In addition, since it is necessary to produce a vacuum atmosphere or the like in a normal reduction atmosphere of the manufacturing process, a large amount of equipment is required in the manufacturing process.

Ceramic heat sinks made of ceramics are lightweight and have a thermal expansion coefficient similar to that of the chip, so they do not generate scratches on electronic components, thereby reducing damage to electronic components and significantly reducing the peeling off of components. The manufacturing equipment is simple and the cost can be greatly reduced.

The manufacturing method of the heat sink according to the present invention is applied to a general ceramic manufacturing process (press, tape casting, injection, etc.), and the manufacturing process must be accompanied by a process of firing at a high temperature. In the high-temperature firing process, the ceramic shrinks instead of maintaining strength while cross-linking and ingrowing. As a result, the quality of the heat sink, which is the final product, is deteriorated due to changes in dimensions and shapes.

According to the manufacturing method of the present invention, low-temperature firing can be performed while maintaining the heat radiation characteristics of the silicon carbide component, and production efficiency can be improved due to no dimensional change, and there is no impurity of other components.

In addition, the silicon carbide heat sink manufactured by the above-described method does not cause the shrinkage of the ceramics caused by the general ceramic manufacturing process, and there is no change in shape, so that no further processing is required. As a result, the production efficiency is high, the production cost can be greatly reduced, and the firing temperature can be significantly reduced, which can greatly reduce the energy consumption in the manufacturing process.

In the production method of the present invention, a binder, a dispersant, and other additives are added to a silicon carbide powder, and the mixture is mixed and prepared into a granulated powder by using a spray dryer or the like. In addition, the manufactured granulated powder is molded into a shape using a mechanical or hydraulic press, or tape casting or injection molding. The molded product is sintered at about 1500 to 1600 ° C in an atmospheric or inert atmosphere, and the sintered product is finished by simple machining so that the bottom is flat so as to maintain the flatness.

When molding by tape casting, the raw material powder is mixed with a binder, a dispersant, a plasticizer, and the like in a mill. The mixed slurry is put into a doctor blade to prepare a ceramic sheet. When the ceramic slurry is dried, it is cut into a plate shape, or it is passed through a grooved roll to give irregularities and cut to meet specifications. The produced sheet is fired at about 1500 to 1600 ° C in a firing furnace to produce a heat sink. If machining for flatness is required as in the press process, it is carried out.

In the case of molding by injection molding, the raw material powder is hot-mixed with an organic binder, a plasticizer or the like and injection-molded. The molded body is debinded at a low temperature for a long time and is baked at about 1500 to 1600 ° C to produce a heat sink. If flatness is required, machining is performed to maintain flatness.

The silicon carbide powder as a raw material constituting the heat sink of the present invention is preferably several tens of micrometers or less, and it is preferable to mix two or more types of silicon carbide powder. This is to maximize particle-to-particle bonding by considering that inter-particle pores are within 0.2 times the particle radius as in the perfect-sphere theory.

It is preferable that the granulated powder is blended so that 60 to 80% by weight of fine particles are contained in an amount of 20 to 40% by weight because the greater the bond between the particles, the better the heat transfer through the particles. It is preferable to use a powder having a particle size of 250 mesh or less and a particle size of 400 mesh or less.

The particle size and the blending amount of the granulated powder and the fine powder are considered considering the filling rate according to each particle size. When the particle size range or the blending amount is out of the above range, the filling rate is decreased, so that the heat transfer efficiency is decreased in the manufactured heat sink.

For example, if one of the silicon carbide powders has an average particle size of about 10 占 퐉, the other one preferably has an average particle size of 2 占 퐉 or less. Depending on the circumstances, some powders having an average particle size of 100 mu m may be mixed and used. This should be considered in terms of the problems occurring in the manufacturing process. The surface roughness problem and the particle desorption phenomenon are considered.

Wherein one or more of polyvinyl alcohol (PVA) or methyl cellulose (MC) is added to the silicon carbide powder, and one of polyethylene glycol, monoethylene glycol, diethylene glycol, and triethylene glycol Of a plasticizer. Finally, the silicate of any one of sodium silicate, lithium silicate, barium silicate, strontium silicate, calcium silicate and magnesium silicate is mixed to prepare a mixture. The preparation after preparation of the mixture is preferably based on a common ceramic process.

In the present invention, silicate is used as the binder.

For example, sodium silicate evaporates and oxidizes to silicate at above a certain temperature. At this time, a certain amount of sodium remains, but the change to silicate is not reduced again in a room temperature atmosphere and a strong covalent bond is formed.

The sodium silicate exists in a liquid state at room temperature and surrounds the outer surface of the silicon carbide powder to silicate the surface, thereby preventing the internal silicon carbide from being oxidized at a high temperature. Since it is added to water used as a solvent, it can be easily oxidized even at a low temperature because it is uniformly applied on the surface and is formed in the form of nanoparticles at the initial stage of oxidation. In addition, since bonding is generated by low-temperature firing, the silicon carbide particles are prevented from ingrowing during firing, and shrinkage is not caused, thereby forming a non-shrinkage silicon carbide product. Further, since no additional inorganic binder is added in addition to the silicate, there is an advantage that the purity can be produced without greatly changing the purity. These properties can also be obtained from lithium silicates, barium silicates, strontium silicates, calcium silicates, and magnesium silicates.

More specifically, sodium silicate begins to oxidize to SiO ₂ at about 350 ° C., where sodium ions are present as impurities in SiO ₂ . As the sintering progresses, sodium silicate encapsulates the surface of the silicon carbide particles to produce SiO ₂ , which inhibits the silicon carbide from oxidizing and serves as a binder to bond the silicon carbide particles together.

Therefore, the silicate used in the present invention is a component serving as an inorganic binder. All of these processes are completed at a temperature of about 700 ° C to 1100 ° C, so that the grain growth of the silicon carbide particles themselves can be suppressed and the plastic shrinkage phenomenon can be prevented.

As such, a mixed powder of a few micrometers of silicon carbide alone or a mixture of silicon carbide of several tens to several hundreds of micrometers is molded into a ceramic manufacturing process such as press, tape casting or injection molding and fired at 700 to 1100 ° C in the air The firing temperature can be relatively lowered. However, when baking at a temperature of 700 ° C or less, the baking strength tends to become weak, which is undesirable. If the baking is performed at a temperature of 1100 ° C or more, there is no problem with the product.

The silicon carbide heat sink fabricated according to the present invention can be confirmed from the test results below, and it can be confirmed that the heat dissipation characteristics and the like are not largely changed in comparison with the sintered silicon carbide heat sink.

For the test, a comparative test was conducted with a commercially available silicon carbide heat sink (manufactured by Taiwan A Company).

1.5% by weight of PVA 205 (Kureai), and 0.5% by weight of TEG # 400 0.5 (based on 100% by weight of mixed powder of silicon carbide fine powder 30% by weight or less and silicon carbide- By weight, PEG # 2000 0.3% by weight, and sodium silicate (40% concentration) 10% by weight were added to water to prepare a mixture. The mixture was dried with a spray dryer to prepare granules.

The granules were put into a mold of 40 * 40 * 5t and pressed at a pressure of 800 kgf / cm2. A small amount of alumina emulsifier was sprayed on a sagas plate having a good flatness and the product was laminated. Also, a small amount of emulsifier was used between the products to prevent fusion between the products. The molded silicon carbide heat sink was fired at 850 ° C for 2 hours.

The commercially available hydrocarbon heat sink used in the comparison was manufactured by baking at 1600 ° C for 4 hours under general high temperature baking conditions.

FIG. 1 is an electron microscope (a) of the heat dissipation plate manufactured according to the manufacturing method of the present invention and a result of energy dispersive spectroscopy (EDS) of the observed region (b) (A) and the result of energy dispersive spectroscopy (EDS) of the observed region (b).

Comparing FIGS. 1 and 2, it can be seen that the densities after firing of the heat insulating plate of the present invention are not significantly different from those of commercially available heat sinks, although the firing temperature is relatively low. In addition, the results of the EDS analysis show that the atomic percentages of Si and C are 43.24: 44.82, which is close to 1: 1, indicating excellent crystallinity (Fig. 1 (b)). In contrast, the EDS analysis of commercially available heat sinks suggests that the atomic percentages of Si and C differ by 38.5: 26.72 because of the loss of C during the firing process. These results suggest that there are many crystal structure defects, which may lead to deterioration in performance when the heat sink is used for a long time.

The evaluation results for the two heat sinks are summarized in Table 1.

Density and porosity were measured by the method specified in JIS C2141 using Archimedes' method.

The strength was measured using a universal testing machine manufactured by In-Strong Co., Ltd., and the three-point bending strength was measured according to JIS R1601 standard.

The heat dissipation characteristics were measured using a test apparatus as shown in Fig. 3 in which the shapes of actual products were simulated. The heat dissipation characteristics were evaluated by measuring the temperature change at the time of installing the heat sink (FIG. 3 (b)) with reference to FIG. 3 (a) In the test apparatus, a film heater was used instead of a CPU used as a heat source. The temperature changes of the CPU (in this test, using a film heater as a heat source) and the internal temperature changes according to the flow of time are programmed to be automatically recorded by a computer.

The heat sink Commercially available heat sink Mechanical properties Density (g / cm3) 2.92 2.95 Porosity (%) 33 33 Strength (kgf) 25.6 16.8 Heat dissipation characteristics Internal temperature (℃) 35 34.5 Reference Temp. (℃) 61.8 61.8 CPU Temp. (℃) 79.3 79 ΔT (° C) 44.3 44.5

As shown in Table 1, the lighter than the conventional heat plate produced by the high temperature firing, the strength was improved by about 150%, and the heat radiation characteristics were not significantly different.

It can be seen from the graphs that the thermal characteristics of the heat sink according to the present invention shown in FIGS. 4 and 5 and the heat sinks on the market are evaluated, and the heat dissipation characteristics are not significantly different from each other even though the firing temperature is low.

The low heat-fired ceramic heat sink of the present invention is superior to conventional metal-based and metal-ceramic composite materials. Conventional materials are dense and have a small specific surface area for heat dissipation, whereas the silicon carbide heat sinks thus baked in the atmosphere have a very large heat dissipation area due to their own pores. In other words, Al ₂ O ₃ (alumina) or other inorganic materials having high thermal conductivity are densified by diffusion, evaporation and condensation at the time of firing, but the silicate-containing silicon carbide heat sink used in the present invention is not is oxidized to form an SiO ₂ and the SiO ₂ is not a high enough temperature to densify the silicon carbide during sintering are coupled to each other exhibits a sufficient strength. If this is not densified during firing, it will have a large specific surface area at the surface, which is a great advantage in the convection and radiation of the heat dissipation mechanism.

In addition, since the present invention uses a low-priced silicate as a manufacturing method of a silicon carbide heat sink, since the sintering temperature is low and the product is not deformed or dimensionally changed, a separate machining is required to maintain the flatness of the substrate. It is a very effective manufacturing method.

The heat sink according to the present invention can be used for a display device such as an IC circuit or an inverter, a CPU of a set-top box, a chipset and a PCB, a CPU of a notebook computer, a chipset and an LED array, a high output LED for lighting and automobiles, .

It is to be understood that the invention is not limited to the disclosed embodiment, but is capable of many modifications and variations within the scope of the appended claims. It is self-evident.

Claims (6)

Mixing a silicon carbide (SiC) powder and a binder to prepare a mixture;
Drying the mixture to prepare granules;
Fabricating a heat sink from the assembly through a molding process;
/ RTI >
The binder is a mixture of any one or more of polyvinyl alcohol (PVA), methyl cellulose (MC) and a silicate of any one of sodium silicate, lithium silicate, barium silicate, strontium silicate, calcium silicate and magnesium silicate,
Wherein the step of preparing the heat sink is performed by firing at 700 to 1100 ° C.
The method according to claim 1,
Wherein the silicon carbide powder is a mixed powder obtained by mixing powders of 400 mesh or less and powders of 250 mesh or less.
delete delete delete A silicon carbide heat sink, characterized in that it is manufactured according to the method of manufacturing the silicon carbide heat sink of claim 1.

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