KR20110013907A - Heat dissipation pad with high thermoconductivity and manufacturing method thereof - Google Patents

Abstract

PURPOSE: A heat emitting pad with high heat conductivity and a manufacturing method thereof are provided to have a metallic oxide film with a fixed thickness, thereby increasing a heat emitting property and an electricity insulating property. CONSTITUTION: The center part of a heat emitting pad is made of silver particles. The surface of the heat emitting pad is made of the first filter and a curable coupling agent. The center of the surface is made of copper. The first filter is made of a silver oxide film whose average thickness is thicker than 500 nano meter. The surface of the heat emitting pad includes the second filer made of a copper oxide film whose average thickness is thicker than 500 nano meter.

Description

Heat dissipation pad with high thermoconductivity and manufacturing method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat radiation pad having a high thermal conductivity efficiency and a method of manufacturing the same, and to a heat radiation pad molded from a thermally conductive composition comprising a filler consisting of a metal particle in a center portion and a metal oxide film.

Various electronic parts such as semiconductors, PCBs, and display devices are accompanied by heat generation during operation of the device due to the characteristics of the material itself and the electrical resistance generated at the connection parts of the components. Heat generated in this way acts as a cause of shortening the endurance of electronic equipment by increasing the temperature of operating parts, especially circuits and lamps of CPU, memory, plasma display monitor or liquid crystal display monitor. The various electronic circuit elements of the device tend to malfunction or exhibit the maximum performance of the part above a certain temperature.

In recent years, miniaturization and integration of electronic components have caused more serious heat generation due to an increase in the number of circuits included in a unit area, and thus cooling of such electronic components has become a very important problem.

As the cooling method, the active cooling method using the cooling fan disclosed in U.S. Patent No. 6409475 and U.S. Patent No. 6,595,130 has the highest cooling performance, but in this case, the noise generated from the cooling fan and the operation of the cooling device are suppressed. The use of power for such a problem is problematic, and additional electric circuits and component spaces must be configured, and thus, there is a problem such as making it difficult to reduce the light weight of the product, which is the recent development trend of electronic products.

In order to improve this, various means have been proposed. In particular, a passive cooling method of dissipating heat to the outside by using a heat sink or a casing of an electronic device is used as an important means. In this case, since the cooling of the electronic circuit is simply performed by heat conduction by radiation or convection to the outside air through the heat sink or shell, no special external power is required to operate the device, and noiseless operation is possible. Compared to the case of using a cooling fan, more freedom in designing the device can be provided. However, when cooling by heat conduction by the heat sink or the device shell as described above, it is important to effectively transfer the heat generated from the electronic device to the heat sink or the shell.

In general, if the electronic circuit and the heat sink or the sheath are simply left in an empty space, the high heat insulating ability of the air prevents the effective diffusion of heat. Therefore, for effective heat conduction, the air layer between the electronic circuit and the heat sink or the sheath is prevented. It is necessary to exclude as much as possible. In addition, the heat sink or the outer shell should be made of metal-based material because it should be able to protect the product and should look good and at the same time be able to diffuse heat effectively. Therefore, in the case of designing contact between the electronic circuit and the heat sink or the outer skin to remove the insulation effect caused by the air layer, the current applied to the electronic circuit may be shorted, which may cause malfunction of the electronic device. At least, even if the normal operation of the device is possible, the use efficiency of the power drops drastically, and there is a risk of electric shock to the user.

In order to improve this, a method of using a filler or a heat dissipation pad has been devised between the electronic circuit and the heat sink or the outer shell of the device. For example, US Pat. No. 4,831,11 discloses a method of using a soft silicone resin between an electronic circuit and a heat sink, wherein the silicone resin transfers heat generated from the electronic circuit to the heat sink or the outer shell of the device to wait for heat. Diffusion into the medium serves to induce cooling of the electronic circuit. In addition, US Pat. No. 5679457 discloses alumina, graphite, boron nitride, and titanium nitride to maximize cooling efficiency by improving the thermal conductivity of the silicone resin used. The method of including the solid powder which is excellent in thermal conductivity etc. is disclosed.

However, in order to effectively cope with the increase in heat emission due to the recent high integration of electronic circuits and to cool the high heat dissipated in the plasma display panel or the liquid crystal display panel, the thermal conductivity efficiency must be further improved. In addition, the heat dissipation pad must have a high electrical insulation property in addition to the excellent cooling effect, because if the leakage of current occurs to the heat sink or the product shell made of metal material, not only waste of power, but also malfunction of the device and reduced durability, safety This can cause an accident.

SUMMARY OF THE INVENTION The present invention has been made to solve the conventional problems, and an object of the present invention is to provide a heat radiation pad having a high thermal conductivity efficiency and a method of manufacturing the same.

One object of the present invention is a heat dissipation pad molded from a thermally conductive composition comprising a first filler made of silver (Ag) oxide film having a central portion of silver (Ag) particles and an average thickness of 500 nm or more, and a curable binder. Can be achieved by providing

Another object of the present invention is to provide a first filler comprising a silver (Ag) oxide film having a central portion of silver (Ag) particles and an average thickness of 500 nm or more, a curable binder comprising a mixture of a binder and a curing agent, a volatile silicone oil, And mixing the curing reaction catalyst to provide a thermally conductive composition; It can be achieved by providing a method for producing a heat radiation pad comprising a; coating the thermally conductive composition on a release paper with a coater and curing and drying at a temperature range of 80 ~ 140 ℃.

In the heat dissipation pad and a method for manufacturing the same, the thermally conductive composition has a center portion made of silver (Ag) particles and a center portion is formed of copper (Ag) oxide film having an average thickness of 500 nm or more. And a second filler made of a copper (Cu) oxide film having an average thickness of 500 nm or more.

The heat dissipation pad according to the present invention has a first filler made of silver (Ag) particles having a central portion of silver (Ag) particles and an average thickness of 500 nm or more, and optionally a central portion of copper (Cu) particles. It is molded into a thermally conductive composition comprising a second filler made of a copper (Cu) oxide film having an average thickness of at least 500 nm to have a high thermal conductivity in the range of 5-6 W / mK. In addition, since the surface of the filler is made of a metal oxide film having a predetermined average thickness, it has an improved heat dissipation effect and electrical insulation, and thus can be stably used in electronic products.

In addition, when the thermally conductive composition including both the first filler and the second filler is used, heat radiation pads may be manufactured at low cost by relatively low cost copper (Cu).

One aspect of the present invention relates to a heat dissipation pad having a high thermal conductivity efficiency, the heat dissipation pad of the present invention is the first filler consisting of silver (Ag) particles in the center and the surface of the silver (Ag) oxide film, And a thermally conductive composition comprising a curable binder. In addition, the thermally conductive composition used in the manufacture of the heat dissipation pad of the present invention has a central portion made of silver (Ag) particles and a central portion made of copper (Cu) particles with a first filler made of a silver (Ag) oxide film. The upper surface may further include a second filler made of a copper (Cu) oxide film.

The filler contained in the thermally conductive composition according to the invention consists of silver (Ag) particles in the center and a silver (Ag) oxide film in the center, or in the center of copper (Cu) particles and the surface of copper (Cu) It is a filler having a double-layer structure consisting of an oxide film. The center of the filler used in the present invention is composed of silver (Ag) or copper (Cu), which has a high thermal conductivity compared to ceramic and aluminum. Therefore, the thermally conductive composition according to the present invention exhibits high thermal conductivity as compared to the case of using a ceramic filler as the filler.

In addition, as a filler of the thermally conductive composition according to the present invention, only a filler having a double-layer structure in which the center portion is made of copper (Cu) particles and the surface is made of a copper (Cu) oxide film can be used. Although copper (Cu) has a lower thermal conductivity than silver (Ag), but the difference is very small, a double layer consisting of copper (Cu) particles and a surface of copper (Cu) oxide film as a filler of the thermally conductive composition The use of a filler with a layered structure is expected to exhibit thermal conductivity close to that of a filler with a double-layered structure consisting of silver (Agu) particles in its core and a silver oxide film on its surface. do. In addition, the filler used in the thermally conductive composition according to the present invention comprises a silver (Ag) particle or a copper (Cu) particle in the center and a surface of the silver (Ag) oxide film or copper (Cu) oxide corresponding to the center particle component. One or more fillers selected from fillers having a bi-layer structure consisting of a membrane, and an aluminum (Al) oxide film or nickel whose center is composed of aluminum (Al) particles or nickel (Ni) particles and whose surface corresponds to the central particle component A combination of one or more fillers selected from fillers having a double-layer structure consisting of (Ni) oxide films.

The average thickness of the oxide film of the filler contained in the thermally conductive composition according to the present invention is at least 500 nm, when having an average thickness of less than 500 nm, the filler may not exhibit sufficient electrical-insulating capability. In addition, there is no restriction | limiting in the upper limit of the average thickness of an oxide film, However, The upper limit of average thickness is preferably 3000 nm or less from the point of not restricting the thermal conductivity of the center part extremely. The mean particle diameter of the filler is preferably 5 to 200 µm, but when the core has an average particle diameter of less than 5 µm, the diameter is too small, and sometimes there is a fear that sufficient thermal conductivity may not be exhibited, and the center has an average particle diameter of more than 200 µm. In the case of, the filler tends to be difficult to uniformly mix with the components of other thermally conductive compositions. In addition, the term "average particle diameter" as used herein means the average of the diameter of the particles in the sphere, the average of the average value of each of the long and short diameter of each particle, if the particle is an ellipsoid, The mean of the average of each of the longest and shortest lengths of the particles.

The filler contained in the thermally conductive composition according to the present invention may be produced by subjecting silver or copper particles to a predetermined treatment to form an oxide film on the particles. The oxide film can be formed by subjecting the metal particles to at least one treatment selected from the group consisting of acid treatment, energy beam irradiation treatment, electrochemical treatment, and heat treatment. In addition, an oxide film having a certain degree of thickness may be formed by simply leaving the metal particles in the air. However, it is preferable to use any of the above treatments because the thickness of the oxide film can be adjusted as desired. Further, in any of the above treatments, it is expected that an oxide film having an excellent electrical insulation performance can be formed than simply leaving the metal particles in the air.

"Acid treatment" means, for example, a treatment in which metal particles are placed in an organic or inorganic acid solution having an appropriate concentration, and mixed and stirred thereof. "Energy beam irradiation process" means a process of irradiating ultraviolet light to the surface of metallic aluminum particles, for example, with a high-pressure mercury lamp. "Electrochemical treatment" means, for example, a treatment for anodizing metal particles. "Heat treatment" means a treatment in which metal particles are placed in an oven at 400 to 600 ° C, for example, and left in an air or oxygen atmosphere for a suitable time.

In the thermally conductive composition according to the present invention, as a filler, the core is composed of copper (Cu) particles and the surface of the core is composed of silver (Ag) particles and the first filler is composed of silver (Ag) oxide film. It further comprises a second filler made of a copper (Cu) oxide film. In the case of using the first filler and the second filler as the filler, the thermal conductivity is lower than that of the first filler. However, considering that silver (Ag) is relatively expensive compared to copper (Cu), the manufacturing cost of the heat radiation pad is There is an advantage that can be significantly lowered. In addition, when using the first filler and the second filler as the filler, the content of the second filler is preferably 50 to 200 parts by weight relative to 100 parts by weight of the first filler, the content of the second filler is 100 weight of the first filler If the amount is less than 50 parts by weight, the manufacturing cost of the heat dissipation pad is high, which makes it difficult to commercialize. When the content of the second filler exceeds 200 parts by weight relative to 100 parts by weight of the first filler, the thermal conductivity value is in a predetermined range (e.g., For example, it may become lower than 5-6 W / mK).

The curable binder used as one component of the thermally conductive composition according to the present invention is a mixture of a binder and a hardener, and the binder is a silicone resin, a polyurethane resin, a polybutadiene resin, a polyisoprene resin, a natural rubber resin, a polyvinyl chloride resin. At least one selected from the group consisting of polyethylene resins, polypropylene resins, polyvinylidene chloride resins, and plasticized resins thereof. The curing agent is used corresponding to the selected binder. The curing agent for the silicone resin is di-t-butylperoxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, di In the case where the organopolysiloxane has two or more alkenyl groups as an organic peroxide such as cumyl peroxide and an addition reaction curing agent, the organohydrogenpolysiloxane containing two or more hydrogen atoms bonded to the silicon atom in one molecule and the platinum catalyst The organosilicon compound which has two or more hydrolysable groups, such as an alkoxy group, an acetoxy group, a ketooxime group, and a propenoxy group, when organopolysiloxane contains two or more silanol groups as a condensation reaction hardening | curing agent And curing by radical reaction and / or addition reaction. In addition, the curing agent of the polyurethane resin is isophorone diisocyanoic acid (ISOPHORONE DIISOCYNATE), polyamide (Polyamide) resin, modified aromatic amine resin, acid anhydride, Jeffamine (Jeffamine) and the like.

The curable binder is prepared by mixing the binder as a subject and the curing agent as a subsidiary agent, preferably the binder is liquid. When the binder is a liquid, it is easy to mix with the curing agent to easily prepare a curable binder and easy handling. In preparing the curable binder, the content of the curing agent varies depending on the combination of the binder and the corresponding curing agent, preferably 50 to 150 parts by weight relative to 100 parts by weight of the binder. If the content of the curing agent is less than 50 parts by weight based on 100 parts by weight of the binder, the degree of curing in the manufacturing process of the heat radiation pad is low, so that the quality of the heat radiation pad may be degraded (for example, insufficient internal strength). If it exceeds 150 parts by weight relative to 100 parts by weight of the binder, a part of the curing agent may be unused, and thus the degree of curing may be weak.

In manufacturing the heat dissipation pad of the present invention, when using a thermally conductive composition containing only the first filler, the content of the curable binder is preferably 10 to 40 parts by weight based on 100 parts by weight of the first filler, and the first filler and the agent In the case of using the thermally conductive composition including both the fillers, the content of the curable binder is preferably 10 to 40 parts by weight based on 100 parts by weight of (first filler + second filler). When the content of the curable binder is less than 10 parts by weight relative to 100 parts by weight of the first filler or the (first filler + second filler), the coupling between the fillers is not smoothly performed, and thus the quality of the heat radiation pad is deteriorated (for example, insufficient. Internal strength), and the viscosity of the thermally conductive composition is too high, which may cause difficulty in applying the thermally conductive composition to the release paper with a coater during the manufacturing of the heat radiation pad. In addition, when the content of the curable binder exceeds 40 parts by weight relative to 100 parts by weight of the first filler or the (first filler + second filler), the thermal conductivity of the heat radiation pad may be lower than a predetermined range.

The thermally conductive composition according to the present invention further comprises a volatile silicone oil and a curing reaction catalyst in addition to the filler, the curable binder as a component. Volatile silicone oils act as an emulsifier to facilitate the mixing of the components in the manufacture of the thermally conductive composition, and most of them are removed during the curing and drying steps of the thermal pad. The curing reaction catalyst is not particularly limited as long as it is commonly known, and preferably platinum (Pt) is used.

Another aspect of the present invention relates to a method for manufacturing a heat radiation pad having high thermal conductivity, wherein the method for manufacturing a heat radiation pad according to the present invention is made of silver (Ag) particles at the center and a surface of a silver oxide film. Mixing a filler, a curable binder consisting of a mixture of a binder and a curing agent, a volatile silicone oil, and a curing reaction catalyst to provide a thermally conductive composition; And curing and drying at a temperature range of 80 to 140 ° C. after applying the thermally conductive composition to a release paper with a coater. In addition, the thermally conductive composition is preferably composed of silver (Ag) particles as the filler, and the core is composed of copper (Cu) particles and the surface is copper ( Cu) The second filler further comprises an oxide film. When the heat radiation pad manufactured through the curing and drying step is actually applied to electronic products, it is used after removing the release paper.

Coaters used to apply the thermally conductive composition to a release paper include die coaters, comma coaters, blade coaters, gravure coaters, and the like, of which double and comma coaters are preferred. Comma coaters are particularly advantageous for coating solutions or pastes with high viscosity.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the embodiments to be described later are only for clearly understanding the present invention, and the scope of the present invention is not limited thereto.

* Explanation of terms used in Examples and Comparative Examples

First filler: Filler consisting of silver (Ag) particles in the center and a silver oxide film on the surface

Second filler: filler consisting of copper (Cu) particles in the center and a copper (Cu) oxide film on the surface

Third filler: Filler composed of aluminum (Al) particles in the center and aluminum (Al) oxide film on the surface

1. Manufacture of Heat Dissipation Pads

Example 1.

A hardening binder was prepared by adding 100 g of a curing agent to 100 g of liquid silicone resin and mixing the mixture. To the curable binder, 600 g of a first filler (average particle size: about 40 μm, oxide average thickness: about 900 nm), 48 g of volatile silicone oil, and 3.4 g of platinum catalyst were added and stirred for about 60 minutes to prepare a thermally conductive composition. The heat conductive composition was apply | coated to a release paper with a comma coater, it passed through the drying furnace of 120 degreeC for 10 minutes, hardening reaction and drying, and the heat radiation pad which is about 1 mm in thickness was manufactured.

Example 2.

It is the same as Example 1 except having used 300 g of the 1st filler and 300 g of the 2nd fillers (made by Ferro company; average particle diameter about 35 micrometers, oxide thickness about 1000 nm).

Comparative Example 1.

It was the same as Example 1 except having used 600 g of 3rd fillers (the Ferro company make; average particle diameter about 30 micrometers, oxide film average thickness about 1000 nm).

2. Thermal Conductivity Analysis of the Thermal Pads

The thermal conductivity of the heat radiation pads prepared in Examples 1 to 2 and Comparative Example 1 was measured based on the ASTM E1461 method. The thermal conductivity of the heat radiation pad prepared in Example 1 was 6 W / mK, and the thermal conductivity of the heat radiation pad prepared in Example 2 was 5.5 W / mK. On the other hand, the thermal conductivity of the heat radiation pad prepared in Comparative Example 1 was 2 W / mK showed a significantly lower value than the embodiment of the present invention.

Claims (13)

A heat dissipation pad formed of a thermally conductive composition comprising a first filler made of silver (Ag) oxide film having a central portion composed of silver (Ag) particles and an average thickness of 500 nm or more, and a curable binder.  The heat dissipation pad according to claim 1, wherein the content of the curable binder is 10 to 40 parts by weight based on 100 parts by weight of the first filler. The heat radiation pad according to claim 1, wherein the thermally conductive composition further comprises a second filler made of a copper (Cu) oxide film having a central portion made of copper (Cu) particles and having an average thickness of 500 nm or more.  The heat dissipation pad according to claim 3, wherein the content of the curable binder is 10 to 40 parts by weight based on 100 parts by weight of (the first filler + the second filler). The heat dissipation pad according to claim 3, wherein the content of the second filler is 50 to 200 parts by weight relative to 100 parts by weight of the first filler. The heat dissipation pad according to any one of claims 1 to 5, wherein the first filler or the second filler has an average particle diameter of 5 to 200 µm at the center portion. The curable binder according to any one of claims 1 to 5, wherein the curable binder is silicone resin, polyurethane resin, polybutadiene resin, polyisoprene resin, natural rubber resin, polyvinyl chloride resin, polyethylene resin, polypropylene resin, poly And a mixture of at least one binder and a curing agent selected from the group consisting of vinylidene chloride resins and plasticized resins thereof. The heat dissipation pad according to claim 8, wherein the amount of the curing agent is 50 to 150 parts by weight based on 100 parts by weight of the binder. The heat dissipation pad according to any one of claims 1 to 5, wherein the thermally conductive composition further comprises a volatile silicone oil and a curing reaction catalyst. The heat radiation pad according to any one of claims 1 to 5, wherein the heat radiation pad has a thermal conductivity of 5 W / mK or more. By mixing a first filler consisting of silver (Ag) oxide film having a central portion of silver (Ag) particles and an average thickness of 500 nm or more, a curable binder composed of a mixture of a binder and a curing agent, a volatile silicone oil, and a curing reaction catalyst Providing a thermally conductive composition; And After coating the thermally conductive composition on a release paper with a coater and curing and drying at a temperature range of 80 ~ 140 ℃; manufacturing method of a heat radiation pad comprising a. A first filler consisting of silver (Ag) oxide film having a central portion of silver (Ag) particles and an average thickness of 500 nm or more, and a copper (Cu) having a central portion of copper (Cu) particles and a surface having an average thickness of 500 nm or more Mixing a second filler comprising an oxide film, a curable binder consisting of a mixture of a binder and a curing agent, a volatile silicone oil, and a curing reaction catalyst to provide a thermally conductive composition; And After coating the thermally conductive composition on a release paper with a coater and curing and drying at a temperature range of 80 ~ 140 ℃; manufacturing method of a heat radiation pad comprising a. The method of claim 11 or 12, wherein the coater is a comma coater.