KR102069059B1 - Method for coating heat spreading layer and electronic component comprising the same - Google Patents

Abstract

The present invention relates to a method for forming a heat dissipation layer and an electronic component including the heat dissipation layer, the method for forming a heat dissipation layer comprising: a composition preparing step of preparing a composition for forming a heat dissipation layer including graphite and carbon nanotubes; And a heat dissipation layer forming step of screen-printing the heat dissipation layer forming composition to form a heat dissipation layer on the surface of the substrate, thereby providing a technology for forming a heat dissipation layer having excellent heat dissipation effect while using a carbon material. do.

Description

Method for forming a heat dissipation layer and an electronic component including the heat dissipation layer {METHOD FOR COATING HEAT SPREADING LAYER AND ELECTRONIC COMPONENT COMPRISING THE SAME}

The present invention relates to a method for forming a heat dissipation layer and an electronic component including the heat dissipation layer.

In recent years, as the integration of components increases through miniaturization of electronic devices, the amount of heat generated inside the product increases, resulting in deterioration of product performance, malfunction or shortening of product life due to overheating.

In order to solve the heat problem of the electronic device, attempts have been made to improve the thermal conductivity by developing a structure or a material of a heat sink. In this regard, the Republic of Korea Patent Publication No. 10-0560201 has been presented a technology related to the graphite heat dissipation sheet.

In addition, studies have been actively conducted to develop a heat dissipation structure using a carbon material such as carbon nanotubes. However, carbon nanotubes are difficult to coat evenly on the surface of the heat sink due to poor dispersibility. Even if formed, there is a problem that the carbon nanotube particles are agglomerated with each other, so that the coating layer may be easily peeled off from the heat sink.

Therefore, the development of a new technology that can improve the existing problems while excellent heat dissipation effect is required.

The present invention has been made to solve the above problems, and an object thereof is to provide a technology capable of forming a heat dissipation layer having excellent heat dissipation effect while using a carbon material.

The problem to be solved by the present invention is not limited to the above-described problem, another technical problem that is not mentioned will be clearly understood by those skilled in the art from the following description.

In one aspect of the present invention, a method for forming a heat dissipation layer includes: a composition preparation step of preparing a composition for forming a heat dissipation layer including graphite and carbon nanotubes; And a heat radiation layer forming step of forming a heat radiation layer on the surface of the substrate by screen printing the heat radiation layer forming composition.

In addition, the composition preparation step may include a first dispersion step of mixing and stirring the graphite and carbon nanotubes in a polyimide resin; And a second dispersion step of applying a shear force to the dispersion by passing the dispersion dispersed in the first dispersion step through a three-roll mill having a draw-in roller, a middle roller, and a scraper roller.

The polyimide resin may include polyimide solids and an organic solvent in the first dispersion step, and based on 64 parts by weight of the polyimide solids, the graphite may be 16 to 95 parts by weight, and the carbon nanotubes may be 0.1 to 2 parts. It may be provided in parts by weight.

In addition, in the second dispersion step, the distance between the draw-in roller and the middle roller may be set to 1 to 2 times the diameter of the graphite, and the distance between the middle roller and the scraper roller may be set to be equal to the diameter of the graphite.

In another aspect of the present invention, an electronic component includes a heat dissipation layer formed on a surface of a substrate according to the above-described heat dissipation layer forming method, wherein the heat dissipation layer is formed to be inclined with respect to the surface of the substrate. It may include.

Means for solving the above problems are merely exemplary and should not be construed as limiting the present invention. In addition to the exemplary embodiments described above, there may be additional embodiments described in the drawings and detailed description of the invention.

As described above, according to the present invention, a composition for forming a heat dissipating layer in which carbon nanotubes and graphite are uniformly dispersed in a polyimide resin may be prepared by a sequential dispersion process performed in the composition preparation step.

In addition, the present invention may be coated on the surface of the substrate using a screen printing process during the step of forming a heat radiation layer on the surface of the substrate, the heat radiation layer formed by screen printing may be formed to be inclined with respect to the surface of the substrate Therefore, the heat dissipation area is increased compared to the graphite heat dissipation layer formed in the horizontal direction of the substrate, thereby improving thermal conductivity.

That is, the present invention is excellent in heat dissipation effect compared to the existing graphite heat dissipation layer formed in the horizontal direction, thereby preventing overheating of the electronic component having the heat dissipation layer to which the present invention is applied, and extending the life of the electronic component to contribute to improving durability. There is.

The effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

1 is a flowchart illustrating a method of forming a heat radiation layer according to an embodiment of the present invention.
Figure 2 is a flow chart showing in detail the composition preparation step according to an embodiment of the present invention.
Figure 3 is a flow chart showing in detail the secondary dispersion step according to an embodiment of the present invention.
Figure 4 is a flow chart showing in detail the step of forming a heat radiation layer according to an embodiment of the present invention.
Figure 5 schematically shows a three roll mill apparatus used in the second dispersion step according to an embodiment of the present invention.
FIG. 6 is a conceptual diagram schematically illustrating a process in which graphite and carbon nanotubes are mixed with each other by application of a shear force in the second dispersion step according to an embodiment of the present invention.
Figure 7 schematically shows a mixed defoaming machine used in the third dispersion step according to an embodiment of the present invention.
8 schematically illustrates a screen printing step according to an embodiment of the present invention.
9 is a conceptual diagram schematically showing an existing graphite structure formed in a plane with a graphite structure according to an embodiment of the present invention.
10 is a photograph of a surface state of a substrate and a surface state of a comparative example according to various embodiments of the present disclosure through a scanning electron microscope.
FIG. 11 is a photograph of the surface state of the screen printed substrate and the surface state of the substrate printed by the bar coater according to an exemplary embodiment of the present invention through a scanning electron microscope.
12 is a photograph confirming whether peeling of the heat dissipation layer occurs from the substrate when one embodiment of the present invention is heated to a high temperature.
Figure 13 shows the temperature measurement point when evaluating the heat radiation characteristics of one embodiment and a comparative example of the present invention.
FIG. 14 is a graph illustrating temperature change over time occurring at each temperature measurement point in evaluating heat radiation characteristics of FIG. 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings, but the well-known technical parts will be omitted or compressed for brevity of description.

In the following embodiments, the terms first, second, etc. are used for the purpose of distinguishing one component from other components rather than a restrictive meaning.

In the following examples, the singular forms "a", "an" and "the" include plural forms unless the context clearly indicates otherwise.

In the following examples, the terms including or having means that there is a feature or component described in the specification and does not preclude the possibility of adding one or more other features or components.

In the case where an embodiment may be implemented differently, a specific process order may be performed differently from the described order. For example, two processes described in succession may be performed substantially concurrently, or may proceed in the reverse order. That is, each step of the methods described herein may be appropriately carried out in any order unless otherwise stated in the specification or otherwise clearly contradicted by context.

The term "about," which is used before numerical values throughout this specification, is used at, or in close proximity to, the numerical values when manufacturing and material tolerances inherent in the meanings indicated are used, Absolute figures are used to prevent unfair use by unscrupulous intruders. In some embodiments, the term “about” means a standard deviation within 1, 2, 3, or 4. In other embodiments, the term “about” is 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5% or 0.1% of a given value or range. Means within.

A method of forming a heat dissipation layer according to an exemplary embodiment of the present invention will be described with reference to the flowchart shown in FIG. 1 and with reference to the drawings shown in FIGS.

1. Pretreatment step <S100>

In this step, the process of removing the foreign substances contained in the graphite and carbon nanotubes by heat-treating the graphite and carbon nanotubes used in the production of the heat dissipation layer forming composition at a high temperature.

In one embodiment, impurities or foreign substances included in the carbon material may be removed through heat treatment using high frequency induction. For example, high-purity graphite and carbon nanotubes in which foreign matters are removed by heat treatment at a temperature of 800 to 1200 ° C. for 1 to 2 hours may be uniformly coated on the surface of the substrate during screen printing in the heat radiation layer forming step to be described later. Since a layer can be formed, it contributes to the improvement of heat dissipation efficiency and thermal conductivity.

On the other hand, this step may be selectively applied depending on the purity of the graphite and carbon nanotubes. That is, in the case of using high purity graphite and carbon nanotubes, this step may be omitted and the process may proceed from the next step.

2. Composition preparation step <S200>

In this step, a process of preparing a composition for forming a heat dissipating layer including graphite and carbon nanotubes may be performed. Here, the composition for forming a heat dissipation layer is a material capable of forming a heat dissipation layer by coating on the surface of the substrate, and means a composition in which polyimide resin, graphite, and carbon nanotubes are mixed. In addition, the substrate means a configuration that requires heat radiation, for example, it can be applied to a printed circuit board, a heat radiation board, a heat radiation sheet and the like.

In one embodiment, the composition preparation step may include a first dispersion step, a second dispersion step, and a third dispersion step. That is, in this step, the dispersion process may be sequentially applied to improve the dispersibility of graphite and carbon nanotubes.

2-1. First dispersion step <S210>

In this step, a process of mixing and stirring graphite and carbon nanotubes in a polyimide resin may be performed. In one embodiment, the polyimide resin may be applied to a liquid polyimide resin composed of polyimide solids and a balance of an organic solvent.

Here, the polyimide resin refers to a high heat resistant resin which is imidized by polymerizing an aromatic acid dianhydride and an aromatic diamine or an aromatic diisocyanate to prepare a polyamic acid derivative, and then ring-dehydrating at high temperature.

In one embodiment, based on 100% by weight of the total polyimide resin, polyimide solids may be applied in 7 to 16% by weight. As a specific example, the content of polyimide solids may be about 7 wt%, about 8 wt%, about 9 wt%, about 10 wt%, about 11 wt%, about 12 wt%, about 13 wt%, about 14 wt%, about 15 weight percent or about 16 weight percent. In addition, the content of the polyimide solids may be in the range of one or more of the above values and one or less of the above values.

For example, the content of polyimide solids can range from about 7 wt% to about 10 wt%, about 10 wt% to about 13 wt%, about 13 wt% to about 16 wt%, or about 7 wt% to about 16 wt% It can be provided in a range of. Polyimide solids according to one embodiment can maintain the heat resistance and coating workability of the resin in an excellent level in the above range.

If the content of the polyimide solid content is less than 7% by weight, the heat resistance is inferior, and if it exceeds 16% by weight, the heat resistance is good, but the viscosity of the liquid resin is increased so that workability may be reduced during the screen printing step to be described later. It is preferable to apply within one range.

In one embodiment, the organic solvent lowers the surface energy of the polyimide resin, thereby improving the spreadability of the heat dissipation layer forming composition and flatness of the printed heat dissipation layer during screen printing. In addition, the organic solvent may be provided in the remaining amount excluding the polyimide solids in the entire polyimide resin.

That is, the amount of the organic solvent may be adjusted so that the polyimide solid content is 7 to 16% by weight in the total polyimide resin. For example, when the total polyimide resin is 100% by weight, the content of polyimide solids in the resin may be 7 to 16% by weight, and the organic solvent may be included as the remaining content (eg, 84 to 93% by weight). have.

Here, the organic solvent is dimethylformamide (DMF, N, N-Dimethylformamide), methylpyrrolidinone (NMP, 1-Methyl-2-pyrrolidinone), dimethylacetamide (DMAc, N, N-Dimethylacetamide), dimethyl sulfoxide (DMSO, dimethylsulfoxide), diethylacetate (diethylacetate) and acetone (acetone) may be provided at least one selected from the group consisting of, but is not limited to this, if the type of solvent that can be mixed with polyimide solids other than the above-described type It is also possible to use solvents.

Commercially available polyimide resin in one embodiment may be used KPI-900-C16N2, such as KOMEC, but is not limited thereto.

When graphite and carbon nanotubes are mixed in the polyimide resin in this step, based on 64 parts by weight of polyimide solids, graphite is 16 to 95 parts by weight, and carbon nanotubes may be mixed in an amount of 0.1 to 2 parts by weight. .

As a specific example, the graphite content is about 16 parts by weight, about 20 parts by weight, about 30 parts by weight, about 40 parts by weight, about 50 parts by weight, about 60 parts by weight, about 70 parts by weight based on 64 parts by weight of polyimide solids , About 80 parts by weight, about 90 parts by weight or about 95 parts by weight. In addition, the content of graphite may be in the range of one or more of the above values and one or less of the above values.

For example, the graphite content ranges from about 16 parts by weight to about 30 parts by weight, about 30 parts by weight to about 50 parts by weight, about 50 parts by weight to about 70 parts by weight, about 70 parts by weight to about 90 parts by weight, about 50 parts by weight to about 95 parts by weight, about 60 parts by weight to about 95 parts by weight or about 16 parts by weight to about 95 parts by weight. Graphite according to an embodiment may form a uniform heat dissipation layer in the above range, and may have a high thermal conductivity and heat dissipation effect.

If the content of graphite is less than 16 parts by weight based on 64 parts by weight of polyimide solids, the content of graphite is too small to uniformly coat graphite on the surface of the substrate during screen printing. In addition, when the graphite exceeds 95 parts by weight, the viscosity of the heat dissipation layer forming composition is too high, so that the dispersibility is lowered, the heat dissipation effect is lowered and the manufacturing cost increases, so the content of graphite is within the above range It is preferable to apply.

In addition, the diameter of the graphite in one embodiment may be applied to 1 ~ 10㎛. As a specific example, the diameter of graphite may be applied to about 1㎛, about 2㎛, about 3㎛, about 4㎛, about 5㎛, about 6㎛, about 7㎛, about 8㎛, about 9㎛ or about 10㎛ . In addition, the diameter of graphite may be in the range of one or more of the above values and one or less of the above values.

For example, the diameter range of graphite ranges from about 1 μm to about 4 μm, from about 4 μm to about 6 μm, from about 6 μm to about 8 μm, from about 8 μm to about 10 μm or from about 1 μm to about 10 μm. It can be prepared as. The diameter of the graphite according to one embodiment can maintain the quality of the heat dissipation layer in the dispersibility and screen printing in the above range at an excellent level.

If the diameter of graphite is less than 1 μm, it is difficult to form a three-dimensional structure of graphite when screen printing. If the diameter exceeds 10 μm, the structure of graphite may be broken during the dispersing process, which may damage the carbon material. Since it is difficult to form a pattern when the diameter of the graphite is preferably applied within the above range.

Here, the diameter of graphite means an average value of the diameters of the graphite particles. The measurement of the average diameter of the graphite particles may be used a measurement method commonly used in the art, for example, optical microscope, optical profiler, transmission electron microscope (TEM), scanning electron microscope (SEM) The particle | grains are image | photographed using etc., a diameter is measured, and these average values can be derived as average diameter.

On the other hand, when carbon nanotubes are mixed in the polyimide resin, the carbon nanotubes may be mixed in an amount of 0.1 to 2 parts by weight based on 64 parts by weight of the polyimide solids. As a specific example, the carbon nanotube content is about 0.1 part by weight, about 0.2 part by weight, about 0.3 part by weight, about 0.4 part by weight, about 0.5 part by weight, about 0.6 part by weight, based on 64 parts by weight of polyimide solids. Parts by weight, about 0.8 parts by weight, about 0.9 parts by weight, about 1 parts by weight, about 1.1 parts by weight, about 1.2 parts by weight, about 1.3 parts by weight, about 1.4 parts by weight, about 1.5 parts by weight, about 1.6 parts by weight, about 1.7 parts by weight It may be provided in parts by weight, about 1.8 parts by weight, about 1.9 parts by weight or about 2 parts by weight. In addition, the content of carbon nanotubes may be in the range of one or more of the above values and one or less of the above values.

For example, the carbon nanotube content ranges from about 0.1 parts by weight to about 0.5 parts by weight, about 0.5 parts by weight to about 1 parts by weight, about 1 parts by weight to about 1.5 parts by weight, about 1.5 parts by weight to about 2 parts by weight. Or from about 0.1 part by weight to about 2 parts by weight. Carbon nanotubes according to an embodiment can maintain an excellent level of dispersibility in the above range, it is easy to form a three-dimensional graphite structure on the surface of the substrate.

If the carbon nanotubes are less than 0.1 parts by weight, graphite particles and carbon nanotubes may not be sufficiently mixed, so that graphite is stacked horizontally on the surface of the substrate, thereby making it difficult to improve thermal conductivity. When the amount is exceeded, the carbon nanotube particles are agglomerated among the particles, so that the graphite structure is limited to three-dimensionally formed, so the content of the carbon nanotubes is preferably performed within the above range.

Carbon nanotubes included in the carbon material of an embodiment include a single wall carbon nanotube, a double wall carbon nanotube, a multiwall carbon nanotube, and the like. The thin multi-walled carbon nanotubes (Thin Multi wall Carbon nanotube) may be provided in any one or a combination of two or more of them.

In addition, in one embodiment, multi-walled carbon nanotubes having an average diameter of 10 nm or less and an average length of 100 μm may be used, but the type, diameter, and length of the carbon nanotubes are not limited to the above examples.

In this step, polyimide resin, graphite, and carbon nanotubes may be added to the stirrer, and stirred at a high speed for a predetermined time using an impeller. For example, the rotation speed of the impeller may be set to 500 to 600 rpm, and the stirring process may be performed for 30 minutes to 1 hour, but the stirring time and speed may be changed according to the type or amount of the stirring material to be added.

2-2. Second dispersion step <S220>

In this step, the first dispersed dispersion in step S210 is passed through a three roll mill apparatus having a draw in roller, a middle roller, and a scraper roller. The process of applying the shear force to the dispersed dispersion may proceed.

Figure 5 schematically shows a three roll mill apparatus used in the second dispersion step according to an embodiment of the present invention. Referring to Figure 5, the three roll mill 100 is a device for homogenizing by passing the stirring material through the fine gap formed between the three rollers placed horizontally. The draw-in roller 110, the middle roller 120, and the scraper roller 130 adjacent to each other rotate at the same time, thereby applying pressure and shear force to the stirring material passing through the roller.

FIG. 6 is a conceptual diagram schematically illustrating a process in which graphite and carbon nanotubes are mixed with each other by application of a shear force in the second dispersion step according to an embodiment of the present invention. Referring to FIG. 6, the graphite particles included in the agitated material are slid by the shear force generated by the draw-in roller 110 and the middle roller 120 when passing through the first interval W1, and around the graphite particles. As the carbon nanotube particles were dragged into the first gap W1 together, dispersion may be performed.

On the other hand, the viscosity of the composition for forming a heat radiation layer in this step can be appropriately adjusted to the content of at least one of the polyimide solids of graphite, carbon nanotubes and polyimide resin to be applied to 10000 ~ 100,000 cps.

As a specific example, the viscosity of the heat dissipation layer forming composition may be prepared in about 10000cps, about 20000cps, about 30000cps, about 40000cps, about 50000cps, about 60000cps, about 70000cps, about 80000cps, about 90000cps or about 100000cps. In addition, the viscosity of the heat dissipation layer-forming composition may be in the range of one or more of the above values and one or less of the above values.

For example, the viscosity of the heat dissipation layer forming composition may be about 10000cps to about 30000cps, about 20000cps to about 40000cps, about 30000cps to about 60000cps, about 40000cps to about 80000cps, about 50000cps to about 90000cps to about 100000cps or about 10000cps It may be provided in the range of about 100000cps. Viscosity of the composition for forming a heat radiation layer according to an embodiment is excellent in dispersibility in the above range, it can be uniformly coated graphite.

If the viscosity of the composition for forming a heat dissipation layer is less than 10000 cps, the mixing between the polyimide resin, graphite, and carbon nanotubes is not smoothly performed during dispersion, and it is difficult to uniformly coat graphite on the surface of the heat dissipation layer during screen printing. When the viscosity of the heat dissipating layer forming composition exceeds 100000 cps, the dispersibility may be poor, so that cohesion may occur between components, or coating workability may be reduced during screen printing. .

In addition, the viscosity of the composition for forming a heat dissipation layer according to an embodiment means that it is measured by a Brookfield viscometer (spindle NO 2, 12 rpm, 25 ° C.).

In this step, the distance between the draw-in roller 110 and the middle roller 120 is set to 1 to 2 times the diameter of graphite, and the distance between the middle roller 120 and the scraper roller 130 is set to be equal to the diameter of graphite. Thus, a shear force can be applied to the composition for forming a heat dissipation layer.

For example, in this step, the distance between the draw-in roller 110 and the middle roller 120 is set to twice the diameter of graphite, and the distance between the middle roller 120 and the scraper roller 130 is equal to the diameter of the graphite. After the first shear force application step (S220A) for passing the composition for forming a heat dissipation layer to pass through the first interval (W1) and the second interval (W2) again the gap between the draw-in roller 110 and the middle roller 120 Reset to 1 times the diameter of the graphite, the interval between the middle roller 120 and the scraper roller 130 to the same diameter of the graphite to the heat dissipating layer forming composition to the first interval (W1) and the second interval (W2) A second shear force application step (S220B) to pass through may be performed.

In this case, when the distance between the rollers is smaller than the diameter of the graphite, the graphite particles are broken to form a three-dimensional structure of graphite, and when the distance between the rollers is too larger than the diameter of the graphite, the dispersibility is reduced, There is a fear that aggregation phenomenon occurs.

In addition, in the process of uniformly dispersing graphite and carbon nanotubes in a minimum process, the distance between the draw-in roller 110 and the middle roller 120 is set to 1 to 2 times the diameter of the graphite, and the middle roller 120 and the scraper It is preferable to set the distance between the rollers 130 to be equal to the diameter of graphite.

2-3. 3rd dispersion step <S230>

In this step, a process of further dispersing and defoaming the dispersion dispersed in step S220 may be performed. Specifically, in this step, the dispersion in which step S220 is completed is added to the mixed defoaming machine 200 capable of rotating and revolving the container containing the sample, and induces further dispersion of graphite and carbon nanotube particles present in the dispersion. can do.

Mixed defoaming machine 200 used in one embodiment is a device configured to apply the centrifugal force and centripetal force using the principle of the revolution and rotation can be defoamed at the same time as the sample mixing. In the mixed defoaming machine 200, the sample container 210 may rotate about the rotating shaft 220 and revolve around the rotating shaft 230.

In this step, the dispersion, which is in close contact with the bottom of the sample container 210 and pushed out due to the centrifugal force generated through the high speed revolution, slides back inward by the rotation of the sample container 210 and repeats friction and intersection with each other. In the process, graphite and carbon nanotube particles may be uniformly dispersed.

In one embodiment, the revolving speed of the sample container 210 by the revolving shaft 230 is set to 600 to 800 rpm, and the revolving speed of the sample container 210 by the revolving shaft 220 is set to 500 to 700 rpm and 1 to 2 to 5 minutes. Can be performed twice. In this case, in terms of maximizing the dispersion effect of the graphite and carbon nanotube particles, the revolution direction and the rotation direction are preferably set to rotate in opposite directions.

Thereafter, the revolving speed of the sample container 210 is set to high speed and the revolving speed is set to low speed in the mixing degassing machine 200 to remove the air present in the dispersion. That is, the dispersion is in close contact with the bottom surface of the sample container 210 by the centrifugal force generated by the high speed revolution of the sample container 210, and the rotating motion of rotating in the opposite direction to the idle is made at a low speed, Bubbles contained in the water are raised upward relatively to burst on the surface of the dispersion can be naturally defoaming. For example, the revolving speed of the sample container 210 may be set at 600 to 700 rpm, and the rotating speed is set to 50 to 100 rpm, and may be performed once for 1 to 3 minutes. The revolution speed, rotation speed, process time, etc. in this step may be changed fluidly depending on the amount or type of dispersion, and other experimental conditions.

3. Heat radiation layer forming step <S300>

In this step, the process of forming a heat dissipation layer on the surface of the substrate by screen printing the composition for forming a heat dissipation layer, the step S200 is completed may proceed. In one embodiment, the step may include a screen printing step and a heat treatment step.

3-1. Screen printing step <S310>

In this step, a process of forming a heat dissipation layer may be performed by applying a composition for forming a heat dissipation layer having a dispersion and defoaming process completed on the surface of the substrate. 8 schematically illustrates a screen printing step according to an embodiment of the present invention. Referring to FIG. 8, the heat dissipation layer forming composition 340 on the mesh net 330 is pushed down the mesh net 330 by the movement of the squeegee 320, and the heat dissipation layer ( 370 is formed.

Here, the mesh size of the mesh network 330 may be appropriately formed according to the diameter and length of graphite or carbon nanotubes. In one embodiment, a mesh network 330 having a size of 100 μm may be used in proportion to 100 μm of an average length of carbon nanotubes.

9 is a conceptual diagram schematically showing a graphite structure and a conventional graphite structure formed in a plane according to an embodiment of the present invention. In one embodiment, the average diameter of the graphite particles included in the heat dissipation layer forming composition is about 5 μm, which is very small compared to the mesh size, but the graphite (G) particles are formed by carbon nanotubes (T) having an average length of 100 μm. They have a structure in which they are entangled with each other, so that a three-dimensional structure of the form as shown in FIG. 9B can be formed on the surface of the substrate during screen printing.

In contrast, when only the graphite 11 is printed on the surface of the substrate 10, the graphite 11 is stacked horizontally on the surface of the substrate 10. The heat dissipation layer is formed.

3-2. Heat treatment step <S320>

In this step, a process of applying heat to the heat radiation layer formed in step S310 may proceed. In one embodiment, the heat treatment may be performed twice by varying the time and temperature conditions.

For example, the heat dissipation layer may be first dried at 100 to 200 ° C. for 20 to 60 minutes. In the first drying, the heat dissipation layer may be dried, and the polyimide resin included in the heat dissipation layer may be imidized. Thereafter, the heat dissipation layer may be secondarily dried at 100 to 300 ° C. for 30 minutes to 2 hours to further increase the imide ratio of the polyimide resin present in the heat dissipation layer.

Meanwhile, the electronic component according to an embodiment may include a heat dissipation layer formed on the surface of the substrate by the above-described method, and the heat dissipation layer may include graphite formed to be inclined with respect to the surface of the substrate. Here, the obliquely formed graphite means that it is formed at an angle with the surface of the substrate so that the crystal surface of the graphite is not parallel to the surface of the substrate. For example, it may be applied at an angle of 90 ° or less with respect to the horizontal plane, but is not limited to the aforementioned angle.

The heat dissipation layer formed on the surface of the substrate may be inclined with the surface of the substrate to form graphite particles, and the heat dissipation layer may include polyimide and carbon nanotubes.

Hereinafter, the present invention will be described in more detail with reference to specific examples. The following examples are only examples to help understanding of the present invention, and thus the scope of the present invention is not limited or limited thereto.

Preparation of Examples and Comparative Examples

Graphite (average diameter 5㎛) and multi-walled carbon nanotubes (average diameter 10nm, average length 100㎛) was heat-treated by high frequency induction for 1-2 hours at a temperature of 800 ~ 1200 ℃ to remove foreign substances. Thereafter, graphite and carbon nanotubes were added to the liquid polyimide resin composed of 64 g of polyimide solids and 336 g of an organic solvent (methylpyrrolidinone) at the content (in grams) shown in Table 1 below, and the impeller was rotated. The speed was set to 500-600 rpm and stirred for 30 minutes to 1 hour to disperse first. The viscosity of the primary dispersion was measured with a Brookfield viscometer (spindle NO 2, 12 rpm, 25 ° C.) and found to be 23600 cps.

The first dispersed dispersion is passed through a three-roll mill apparatus having a draw-in roller, a middle roller and a scraper roller, wherein the distance between the draw-in roller and the middle roller is set to 10 μm, which is twice the diameter of graphite, and the middle roller and the scraper The distance between the draw-in roller and the middle roller is reset to 5 μm after the first shear force application process of passing the heat dissipating layer forming composition through the first interval and the second interval by setting the interval between the rollers to 5 μm equal to the diameter of graphite. The secondary shear force application step of passing the heat dissipating layer-forming composition through the first interval and the second interval was performed.

Thereafter, the dispersion was introduced into the mixed defoaming machine, and the dispersion speed was set to 600 to 800 rpm for the sample container by the revolving shaft, and the rotating speed of the sample container to 500 to 700 rpm for the rotating shaft was performed for 2 to 5 minutes. It was. Then, the degassing | defoaming process was performed for 1-3 minutes, setting the revolution speed of a sample container to 600-700 rpm, and rotating speed to 50-100 rpm.

Using a screen printing apparatus (mesh size is 200 mesh) by applying the composition for forming the heat dissipation layer completed degassing on the surface of the substrate to form a heat dissipation layer, the heat dissipation layer for 20 to 60 minutes at 100 ~ 200 ℃ First drying, the heat-dissipating layer was secondly dried at 100 ~ 300 ℃ for 30 minutes to 2 hours to complete the process.

division Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Graphite 20 45 95 95 14 140 30 Carbon nanotubes 0.1 One One 0 One One 3

Evaluation of thermal conductivity for each example and comparative example

The thermal conductivity of each Example and Comparative Example was measured three times with a biaxial thermal conductivity meter, and the measured results are shown in Table 2 below.

division One-time longitudinal thermal conductivity of substrate (w / mk) Twice the planar longitudinal thermal conductivity of the substrate (w / mk) 3-way longitudinal thermal conductivity of substrate (w / mk) Example 1 11.14 11.41 10.99 Example 2 11.96 12.01 12.23 Example 3 13.81 12.89 13.17 Comparative Example 1 10.56 10.67 10.98 Comparative Example 2 9.57 8.98 8.89 Comparative Example 3 10.78 10.71 10.41 Comparative Example 4 10.26 10.33 10.25

As shown in Table 2, based on 64 parts by weight of polyimide solids, Examples 1 to 3 in which the content of graphite and carbon nanotubes were prepared within an optimum range were less than or above the content of graphite and carbon nanotubes. It can be confirmed that the thermal conductivity is excellent compared to the Comparative Examples 1 to 4.

10 is a photograph of a surface state of a substrate and a surface state of a comparative example according to various embodiments of the present disclosure through a scanning electron microscope. Fig. 10A shows a cross section of the heat dissipation layer of Example 1 with a scanning electron microscope, b shows a heat dissipation layer of Example 2, and c shows the heat dissipation layer of Example 3; It photographed and (d) photographed the heat dissipation layer of the comparative example 4. FIG. Referring to Figures 10 (a) to (c), it can be seen that the structure formed by the graphite is a constant inclination on the surface of the substrate. On the other hand, in the case of Comparative Example 4, the content of the carbon nanotubes more than 2 parts by weight, it can be seen that the aggregation phenomenon between the carbon nanotube particles.

FIG. 11 is a photograph of the surface state of the screen printed substrate and the surface state of the substrate printed by the bar coater according to an exemplary embodiment of the present invention through a scanning electron microscope. Figure 11 (b) shows a graphite three-dimensional structure formed in the heat dissipation layer of Example 3, Figure 11 (a) is a coating of the heat dissipation layer forming composition of Example 3 on the surface of the substrate using a bar coater One heat dissipation layer structure is shown. Referring to FIG. 11, it can be seen that the heat dissipation layer structure formed by the bar coater does not form a three-dimensional structure such as the heat dissipation layer structure formed by screen printing, but is simply stacked on the surface of the substrate.

12 is a photograph confirming whether peeling of the heat dissipation layer occurs from the substrate when one embodiment of the present invention is heated to a high temperature. That is, FIG. 12 is a screen printing of the heat dissipation layer forming composition of Example 3 on a substrate, and confirms whether the heat dissipation layer is peeled off from the substrate when heated to a specific temperature for a predetermined time, the heat dissipation layer of this embodiment is 300 ℃ It can be seen that no peeling phenomenon occurred.

Figure 13 shows the temperature measurement point when evaluating the heat radiation characteristics of one embodiment and a comparative example of the present invention. Referring to Fig. 13, (a) stacks an aluminum plate 420A on a hot plate 410A and fixes the substrate 430A on an aluminum plate 420A at a specific point (NO.1, NO.2). It is a measure of temperature change over time. 13B shows screen printing of the heat dissipating layer 440 of Example 3 on the surface of the substrate 430B, and measures the temperature change with time at specific points NO.3 and NO.4. It is.

FIG. 14 is a graph illustrating temperature change over time occurring at each temperature measurement point in evaluating heat radiation characteristics of FIG. 13. Referring to FIG. 14, it can be seen that NO.4, the point at which the heat dissipation layer is applied, has an excellent heat dissipation effect over time since the temperature is lower than that of other measurement points.

As a result, the present invention increases the surface roughness of the substrate due to the three-dimensional structure of the graphite formed to be inclined with respect to the surface of the substrate, and the surface area of the graphite is increased, so that the thermal conductivity and the heat dissipation effect are superior to the conventional graphite heat dissipation layer formed in the horizontal direction. There is an advantage.

In particular, the present invention can ensure the heat dissipation characteristics in the vertical direction, which was not expected in the conventional graphite structure stacked horizontally, thereby preventing overheating of the electronic component having the heat dissipation layer to which the present invention is applied, and extends the life of the electronic component. By extending it has the effect of contributing to the improvement of durability.

As described above, the detailed description of the present invention has been made by the embodiments with reference to the accompanying drawings. However, since the above-described embodiments have only been described by way of example, the present invention is limited to the above embodiments. It is not to be understood that the scope of the present invention is to be understood by the claims and equivalent concepts described below.

100: 3 roll mill
110: draw in roller
120: middle roller
130: scraper roller
140: scraper
W1: first interval
W2: 2nd interval
200: mixed deaerator
210: sample container
220: rotating shaft
230: idle shaft
310, 350: screen frame
320: squeegee
330 mesh
340: composition for forming a heat radiation layer
10, 360
370, 440: heat dissipation layer
410A, 410B: Hot Plate
420A, 420B: Aluminum Plate
430A, 430B: Board
11, G: Graphite
T: Carbon Nanotube

Claims (5)

A composition preparation step of preparing a composition for forming a heat dissipation layer comprising graphite and carbon nanotubes; And
And a heat radiation layer forming step of forming a heat radiation layer on a surface of the substrate by screen printing the heat radiation layer forming composition.
The composition preparation step
A first dispersion step of mixing and stirring the graphite and carbon nanotubes in a polyimide resin; And
And a second dispersion step of applying a shear force to the dispersion by passing the dispersion dispersed in the first dispersion step through a three-roll mill having a draw-in roller, a middle roller, and a scraper roller.
In the first dispersion step, the polyimide resin includes a polyimide solid content and an organic solvent,
Based on 64 parts by weight of the polyimide solid content, the graphite is 16 to 95 parts by weight, the carbon nanotubes are characterized in that 0.1 to 2 parts by weight
Heat radiation layer formation method. delete delete The method of claim 1,
In the second dispersion step, the distance between the draw-in roller and the middle roller is set to 1 to 2 times the diameter of the graphite, and the distance between the middle roller and the scraper roller is set to be equal to the diameter of the graphite.
Heat radiation layer formation method. And a heat dissipation layer formed on the surface of the substrate according to the method of any one of claims 1 and 4.
The heat dissipation layer is characterized in that it comprises a graphite formed inclined with respect to the surface of the substrate
Electronic parts.

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