KR101891405B1

KR101891405B1 - Metal foam and manufacturing method of the metal foam

Info

Publication number: KR101891405B1
Application number: KR1020160147948A
Authority: KR
Inventors: 양현경; 장형일
Original assignee: 부경대학교 산학협력단
Priority date: 2016-11-08
Filing date: 2016-11-08
Publication date: 2018-08-23
Also published as: WO2018088751A1; CN109922908A; KR20180051082A

Abstract

In the metal foam of the present invention and the method for producing the same, the method for producing the metal foam of the present invention comprises the steps of forming a slurry by mixing metal powder, activated carbon, and water, adding acid to the slurry to foam the slurry , Drying the foamed slurry to form a foam, and sintering the foam.

Description

FIELD OF THE INVENTION [0001] The present invention relates to metal foams,

The present invention relates to metal foams and methods of making them.

As electronic devices become more and more highly integrated, a lot of heat is generated in electronic devices, and problems related to malfunction due to heat and heat generation such as malfunction are occurring. Therefore, there is a growing interest in heat dissipators for dissipating heat from electronic devices. The heat dissipater uses the principle of achieving thermal equilibrium by sharing the heat energy with each other when the two materials meet, and as a result, it can lower the temperature of the heat source by dividing the strong heat of the heat source.

BACKGROUND ART A heat sink is a heat sink attached to an electronic device such as a semiconductor device to prevent a temperature rise, and is generally manufactured in the form of a fin to broaden the surface area. Since the large surface area of the heat sink has a large contact area with ambient air, it is possible to efficiently heat the heat from the heat source in a natural convection manner.

However, it takes a lot of time and cost to manufacture an existing heat sink, and there are problems such as a weight problem due to the type of metal to be manufactured as a heat sink, and a limitation of the surface area due to manufacturing limitations.

However, conventional heat sinks take a lot of time and cost to manufacture, and there is a problem of weight due to the metal and a limitation of the surface area size due to manufacturing limitations.

It is an object of the present invention to provide a method for producing a metal foam having excellent heat radiation characteristics.

Another object of the present invention is to provide a metal foam having excellent heat radiation characteristics.

A method for producing a metal foam for one purpose of the present invention comprises the steps of forming a slurry by mixing metal powder, activated carbon and water, adding an acid to the slurry to foam the slurry, drying the foamed slurry To form a foam, and sintering the foam.

In one embodiment, the acid may be at least one of hydrochloric acid, sulfuric acid, and nitric acid.

In one embodiment, in the step of sintering the foam, under an inert gas, it may be sintered to a temperature below the melting point of the metal.

In one embodiment, the metal powder is selected from the group consisting of Au, Ag, Zn, Al, Fe, Mg, Cu, And tin (Sn).

In one embodiment, in the step of forming the foam, the foamed slurry may be dried by heating at a temperature of greater than 60 < 0 > C but less than 300 < 0 > C.

A metal foil for another purpose of the present invention is formed by foaming and curing a slurry containing a metal oxide and an activated carbon, the metal powder and the activated carbon.

In one embodiment, the metal foam may be a heat sink.

According to the metal foam of the present invention and the method for producing the same, the present invention can provide a porous metal foam having a uniform pore size and distribution. The metal foams of the present invention are uniformly sized and uniformly distributed throughout the metal foam and can exhibit a large surface area. Thus, by contacting with air through a large area, heat can be effectively released. According to the present invention, an oxidized metal foam may be produced by adding an acid to the metal foam so that the metal foam may exhibit an insulating effect. In addition, since the metal foam of the present invention is a porous material formed with a plurality of pores, it may be light in weight as compared with a heat sink made of a conventional metal. Due to these properties, the metal foam can be used as a heat sink for electronic equipment. Further, according to the present invention, the manufacturing cost of the heat sink can be reduced, which is economical compared with a die casting process for manufacturing a conventional heat sink.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a view for explaining a method for producing a metal foam of the present invention. FIG.
2 is a view for explaining heat dissipation properties of metal foams according to embodiments of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It is to be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the term "comprises" or "having ", etc. is intended to specify that there is a feature, step, operation, element, part or combination thereof described in the specification, , &Quot; an ", " an ", " an "

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a view for explaining a method for producing a metal foam of the present invention. FIG.

Referring to FIG. 1, in order to produce a metal foam, first, a metal powder, activated carbon, and water are mixed to prepare a slurry (step S110).

The metal powder may be at least one selected from the group consisting of Au, Ag, Zn, Al, Fe, Mg, Cu, Ti, And may include powder of at least one metal. Although metal powders are mentioned by way of example, the present invention is not limited thereto.

Activated carbon is a substance in which most of the constituent material is made of carbonaceous material, which can be synonymous with activated carbon.

The metal powder and the activated carbon are included in the foam formed by foaming the slurry, so that the foam has excellent hardness and can play a role in maintaining the shape. In addition, when a foaming agent for forming bubbles is added to the slurry containing the metal powder and the activated carbon, fine pores can be densely formed and foamed.

At this time, water may be added in an appropriate amount so that the metal powder and activated carbon can be mixed uniformly.

Then, acid is added to the slurry, and the slurry is foamed (step S120).

At this time, the acid may be at least one of hydrochloric acid, sulfuric acid, and nitric acid.

When acid is added to the slurry, bubbles may be generated in the slurry by reaction of the metal powder and the activated carbon of the slurry with an acid. At this time, the size of the generated bubbles may be fine and uniform. The slurry can be uniformly and uniformly pored with pores, and the pore size can be micro-sized. That is, bubbles can be formed that are uniform in size and distributed in the slurry generally and densely and uniformly. Further, by adding an acid to the slurry, the metal powder of the slurry can be oxidized, together with the foaming of the slurry.

Subsequently, the foamed slurry is dried to form a foam (step S130).

The foamed slurry can be dried by heating the slurry at a temperature greater than 60 < 0 > C but less than 300 < 0 > C. Through the drying under the above temperature conditions, water, impurities, etc. in the foamed slurry can be thermally decomposed. At this time, in the process of drying the foamed slurry, pores may be formed as the moisture of the slurry is removed along with the formation of pores by the continuous reaction of the slurry and the acid.

When the slurry is heated at a temperature of 60 DEG C or less, moisture, impurities, and the like may not be thermally decomposed in the slurry. Or when the slurry is heated at a temperature of 300 ° C or higher, pores may be formed in the slurry not uniformly, pores having irregular sizes or excessively large pores may be formed, pores may overlap each other, . Thus, it may be desirable to dry the foamed slurry at a temperature range of greater than 60 < 0 > C but less than 300 < 0 > C.

That is, the reaction between the slurry containing the metal powder and the activated carbon and the acid and the moisture removed during the drying of the foamed slurry can form a foam in which fine pores are densely and uniformly present.

The foam is then sintered to produce the metal foam of the present invention (step S140).

The foam may be sintered under an inert gas at a temperature at which the metal contained in the slurry does not melt, i.e., at a temperature below the melting point of the metal. Sintering is a phenomenon in which heat is tightly adhered to each other and solidifies, and a sintering is a bonding reaction in which a pure solid phase or a liquid phase is mixed with a solid. In the present invention, the foamed slurry is heated and dried to remove moisture and sinter the foam containing the metal and the activated carbon to bond the metal. At this time, when the foam is sintered at a temperature lower than the melting point of the metal contained in the slurry, the metal constituting the metal foam is bonded, but the metal is not completely melted and the shape of the foam can be maintained. That is, pores formed in the metal foam may be retained. In addition, the mechanical strength of the metal foam can be improved through the joining of the metal, whereby the metal foam can be improved in shape retention.

For example, a conductor such as aluminum excellent in thermal conductivity can be used as the metal. When aluminum is used, the sintering temperature of the foam may be 400 ° C to 800 ° C. When the aluminum-containing foam is sintered at a temperature of less than 400 ° C., the metal may not be bonded, and when sintering at a temperature higher than 800 ° C., the metal of the foam may be melted and the shape of the foam may not be maintained .

Although the sintering temperature in the case of using aluminum is mentioned as an example, the sintering temperature can be selected depending on the type of metal used for manufacturing the metal foam of the present invention, as described above, have.

The metal foams of the present invention can be formed using various types of molds suitable for a desired use, shape, size, and the like. Specifically, the metal foams of the present invention having desired shapes, sizes, etc. can be formed by selecting various types of molds from the slurry, foaming them in the mold, and drying and sintering them. For example, the present invention can use a mold in the form of a fin.

According to the present invention, as described above, the metal foams of the present invention can be formed into fine, uniform, and uniformly formed metal powders and activated carbon, which are formed by reacting metal powder and activated carbon with acid, without using a foaming agent such as liquid silicate, Size pores. The metal foams have a large surface area because they contain fine pores uniformly and uniformly. They are excellent in thermal conductivity because they are made of metal. Accordingly, the metal foams have a large area in contact with ambient air and excellent heat conductivity, It is possible to effectively dissipate natural convection. In addition, the metal foam may be lightweight since many pores are formed. In addition, the fine and uniformly sized pores formed in the metal foam can shield the electromagnetic waves generated from the electronic device.

In addition, the present invention provides a process for producing a metal foam, which uses only metal powder and activated carbon without using a material such as a binder for maintaining the shape of the metal foam, and a process of sintering the foam foamed by acid Through, excellent mechanical strength and shape retention Can be produced. Further, the metal powder is oxidized by the acid, so that the metal foam can exhibit an insulating effect.

In other words, the metal foam of the present invention has excellent heat conductivity because it contains metal oxide and activated carbon, and has excellent heat dissipation characteristics due to a large surface area due to fine pores of uniform size uniformly distributed in the metal foam And it is possible to have excellent durability through the sufficient mechanical strength and shape retention of the metal foam. In addition, since the metal powder is oxidized by the reaction with acid, the metal powder is oxidized and can exhibit an insulating effect, and dense and uniform pores can play a role in blocking electromagnetic waves. Due to the characteristics of the metal foam of the present invention, the metal foam of the present invention can be used as a heat sink of an electronic device such as an LED lamp.

Hereinafter, metal foams of the present invention and a method for producing the same will be described in detail with reference to specific examples.

Using aluminum as the metal powder, 30 g of aluminum powder, 1 g of activated carbon, and water were mixed to prepare a slurry. Then, the slurry was foamed by adding hydrochloric acid. Subsequently, the foamed slurry was dried at a temperature of 100 ° C and then sintered at a temperature of 600 ° C to produce a metal foam (hereinafter referred to as Al foam) according to Example 1 of the present invention.

In addition, zinc powder, iron powder, copper powder, and titanium powder were used as metal powders, and sintering was performed at 400 DEG C for iron, 1500 DEG C for iron, 1050 DEG C for copper, 1600 3, 4, and 5 according to the present invention (hereinafter, referred to as " metal foams according to the present invention ") under substantially the same conditions as those in Example 1, Zn foams, Fe foams, Cu foams, and Ti foams).

Then, the foams according to Examples 1 to 5 were constructed as heat sinks of electronic devices including LED chips to measure heat distribution. The heat distribution was measured after 3 hours of operation of the electronic device by measuring the heat distribution at each position of the LED chip and the heat sink and calculating the difference. The test environment temperature was 23 ± 1 ° C. The results are shown in Fig.

2 is a view for explaining heat dissipation properties of metal foams according to embodiments of the present invention.

Referring to FIG. 2, in the case of the Al foam heat sink, the temperature at the LED chip position is 48.4 ° C, the temperature of the heat sink is 42.2 ° C and the temperature difference is 6.2 ° C. In the case of the Zn foam heat sink, The temperature of the heat sink is 39.6 ° C, and the temperature of the heat sink is 9.0 ° C. The Fe foam heat sink exhibits a temperature difference of 51.7 ° C for the LED chip and 11.3 ° C for the heat sink of 40.4 ° C. The temperature of the LED chip is 52.4 ° C for the Cu foam heat sink, the temperature of the heat sink is 40.6 ° C, Can be confirmed. Particularly, the temperature of the Ti foam heat sink is 52.0 ° C in the LED chip, but it is 38.6 ° C in the heat sink, and the temperature between the LED chip and the heat sink is 13.4 ° C.

That is, it can be seen that the metal foams according to embodiments of the present invention exhibit a difference in the temperature measured at the LED chip position and the position of the heat sink as a whole, which means that the metal foams according to the embodiments of the present invention exhibit heat- .

Also, the mechanical strength of the metal foams according to the embodiments of the present invention was confirmed. The results are shown in Table 1.

Mechanical strength (MPa) Max-load (kgf) Al foil 1.97 107.2 Zn foil 4.14 210.8 Fe foam 2.56 138.8 Cu foil 2.84 140.0 Ti foam 2.30 120.0

Referring to Table 1, it can be seen that the mechanical strengths of the metal foams according to the embodiments of the present invention are 1.97 for Al foil, 4.14 for Zn foil, 2.56 for Fe foil, 2.84 for Cu foil and 2.30 for Ti foil, Means that the mechanical strength of the metal foams according to the invention has sufficient mechanical strength to be used as a heat sink. Particularly, among the metal foams of the present invention, the strength of the Zn foams is the highest, and the mechanical strength of the Al foams is relatively low. However, it can be confirmed that the Al foams have sufficient mechanical strength to be used as a heat sink for electronic devices.

Accordingly, it can be confirmed that the metal foam having sufficient mechanical strength for use as a heat sink can be formed without using a separate binder according to the present invention.

2 and Table 1, it can be seen that the metal foams according to the present invention have excellent heat dissipation characteristics and excellent mechanical strength, and thus can be used as a heat sink for electronic equipment.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims. It can be understood that it is possible.

Claims

Mixing the metal powder, activated carbon, and water to form a slurry;
Adding an acid to the slurry to foam the slurry;
Drying the foamed slurry at a temperature greater than 60 < 0 > C but less than 300 < 0 > C to form a foam; And
Sintering the foam at a temperature below the melting point of the metal to bond the metal of the foam,
Wherein the metal powder in the slurry is oxidized by an acid in the step of foaming the slurry so that the foam is electrically insulative.
A method for manufacturing a metallic foam for a heat sink comprising a plurality of pores and having electrical insulation and thermal conductivity.

The method according to claim 1,
Wherein the acid is at least one of hydrochloric acid, sulfuric acid, and nitric acid.

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The method according to claim 1,
The metal powder may be at least one selected from the group consisting of Au, Ag, Zn, Al, Fe, Mg, Cu, Ti, Characterized in that it comprises at least any one powder,
A method for producing a metal foam.

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The slurry containing the metal powder and the activated carbon is foamed by the acid, and the foamed slurry is formed by curing,
Characterized in that the metal powder is oxidized by the acid to have electrical insulation.
A plurality of pores and having electrical insulation and thermal conductivity,
Metal foam for heat sink.

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