WO2018088751A1

WO2018088751A1 - Metal foam and preparation method therefor

Info

Publication number: WO2018088751A1
Application number: PCT/KR2017/012227
Authority: WO
Inventors: 양현경; 장형일
Original assignee: 부경대학교 산학협력단
Priority date: 2016-11-08
Filing date: 2017-11-01
Publication date: 2018-05-17
Also published as: KR101891405B1; KR20180051082A; CN109922908A

Abstract

The present invention relates to a metal foam and a preparation method therefor. A method for preparing a metal foam of the present invention comprises the steps of: mixing metal powder, active carbon, and water to form slurry; adding acid to the slurry to allow the slurry to foam; drying the foamed slurry to form a foam; and sintering the foam.

Description

Metallic foams and methods of making the same

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

As the electronic devices are increasingly integrated, a lot of heat is generated in the electronic devices, and thus problems related to heat generation such as malfunctions and malfunctions caused by the heat are generated. Therefore, there is a growing interest in heat sinks for dissipating heat from the electric appliances. The radiator uses the principle of achieving thermal equilibrium by sharing heat energy of two materials when they meet each other. As a result, an object that can lower the temperature of the heat source by dividing the strong heat of the heat source.

Heat sinks are heat sinks attached to prevent temperature rise in electronic devices such as semiconductor devices. In general, heat sinks are manufactured in the form of fins to increase surface area. Since the large surface area of the heat sink has a large area of contact with the surrounding air, it is possible to efficiently heat convection heat from the heat source efficiently.

However, it takes a lot of time and money to manufacture a conventional heat sink, there is a problem such as the weight problem according to the type of metal to be produced as the heat sink and the limitation of the surface area according to the manufacturing limitations.

However, conventional heat sinks require a lot of time and cost to manufacture, and there are problems such as weight problems due to metal and limitation of surface area size due to manufacturing limitations.

One object of the present invention is to provide a method for producing a metal foam having excellent heat dissipation characteristics.

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

Method for producing a metal foam for one purpose of the present invention is to form a slurry by mixing a 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, it can be sintered at a temperature below the melting point of the metal, under an inert gas.

In one embodiment, the metal powder is gold (Au), silver (Ag), zinc (Zn), aluminum (Al), iron (Fe), magnesium (Mg), copper (Cu), titanium (Ti), and It may include at least one powder of tin (Sn).

In one embodiment, in the step of forming the foam, the foamed slurry may be dried by heating at a temperature of more than 60 ℃ less than 300 ℃.

Metal foams for other purposes of the present invention include metal oxides and activated carbon, but are formed by foaming and curing a slurry comprising metal powder and activated carbon.

In one embodiment, the metal foam may be a heatsink.

According to the metal foam of the present invention and a manufacturing method thereof, the present invention can provide a porous metal foam having a uniform pore size and distribution. The metal foam of the present invention may be uniformly and densely distributed throughout the metal foam with uniformly sized pores and exhibit a large surface area. Therefore, by contacting the air through a large area, heat can be effectively released. According to the present invention, by the addition of an acid to prepare the metal foam, an oxidized metal foam may be produced 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 lighter as compared with a heat sink made of a conventional metal. Due to these characteristics, the metal foam can be used as a heat sink of an electronic device. In addition, according to the present invention, the manufacturing cost of the heat sink can be reduced compared to the die casting process for manufacturing a conventional heat sink can be economical.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure for demonstrating the manufacturing method of the metal foam of this invention.

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

Hereinafter, with reference to the accompanying drawings will be described in detail an embodiment of the present invention. As the inventive concept allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprises" or "having" are intended to indicate that there is a feature, step, operation, component, part, or combination thereof described on the specification, and one or more other features or steps. It is to be understood that the present invention does not exclude, in advance, the possibility of the presence or the addition of an operation, a component, a part, or a combination thereof.

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. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

Referring to FIG. 1, the present invention first prepares a slurry by mixing a metal powder, activated carbon, and water to prepare a metal foam (step S110).

The metal powder is selected from among gold (Au), silver (Ag), zinc (Zn), aluminum (Al), iron (Fe), magnesium (Mg), copper (Cu), titanium (Ti), and tin (Sn). It may include a powder of at least one metal. Although the metal powder is mentioned as an example, the present invention is not limited thereto.

Activated carbon is a material made of most carbonaceous material, and may mean the same as activated carbon.

The metal powder and the activated carbon are included in a foam formed by foaming the slurry, and thus the foam may have an excellent hardness and play a role in maintaining a shape. In addition, when a foaming agent that forms bubbles is added to the slurry including the metal powder and activated carbon, pores of fine size may be densely produced and foamed.

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

Then, an acid is added to the slurry to foam the slurry (step S120).

In this case, 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 the reaction of the metal powder of the slurry and the acid and the activated carbon. At this time, the size of the bubbles generated may be fine and uniform. The pores may be foamed evenly and densely throughout the slurry, and the pore size may be micro size. That is, bubbles of uniform size and generally dense and uniformly distributed in the slurry can be formed. In addition, by adding an acid to the slurry, while the slurry is foamed, the metal powder of the slurry can be oxidized.

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

The foamed slurry may be dried by heating the slurry at a temperature of more than 60 ℃ below 300 ℃. Through drying at the temperature conditions, moisture, impurities, etc. in the foamed slurry may be thermally decomposed. At this time, in the process of drying the foamed slurry, in addition to the formation of pores by the continuous reaction of the slurry and acid, pores may also be formed as the moisture of the slurry is removed.

When the slurry is heated at a temperature of 60 ° C. or less, moisture or impurities may not be thermally decomposed in the slurry. Alternatively, when the slurry is heated at a temperature of 300 ° C. or higher, pores may be unevenly formed in the slurry, irregular or excessively large pores may be formed, and the pores may overlap each other to cause cracks in the foam. It may be formed. Therefore, it may be desirable to dry the foamed slurry in a temperature range of more than 60 ℃ less than 300 ℃.

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

Then, the foam is sintered to prepare a 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, ie, below the melting point of the metal. Sintering is a phenomenon in which the solid tightly adheres to each other by heating and solidifies, and the coupling reaction in which the pure solid phase or some liquid phases between solids are mixed may be referred to as sintering. In the present invention, by heating and drying the foamed slurry, moisture is removed and the foam containing the metal and the activated carbon is sintered to allow the metal to be bonded. In this case, when the foam is sintered at a temperature less than the melting point of the metal included in the slurry to form a foam, the metal constituting the metal foam is bonded, but the metal is not completely melted to maintain the shape of the foam. That is, pores formed in the metal foam can be maintained. In addition, the mechanical strength of the metal foam can be improved through the bonding of the metal, and accordingly, the shape retention force of the metal foam can be improved.

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

Although the above-mentioned sintering temperature in the case of using aluminum is exemplarily mentioned, the sintering temperature may be an appropriate temperature at which the metal used may be bonded but not melted according to the type of metal used to manufacture the metal foam of the present invention as described above. have.

The metal foam of the present invention can be formed using various types of molds (frames) suitable for the desired use, shape, size, and the like. Specifically, the slurry may be selected from various molds and foamed in the mold, and then dried and sintered to form the metal foam of the present invention having a desired shape, size, and the like. For example, the present invention may use a fin in the form of a fin.

According to the present invention, as described above, the metal foam of the present invention is fine and uniform formed by reacting metal powder and activated carbon with acid, without using a foaming agent such as liquid silicate, which is generally used in the manufacture of foam. It may comprise pores of size. The metal foam may have a large surface area because it contains fine pores densely and uniformly, and since the metal foam is composed of metal, it has excellent thermal conductivity, and thus, heat is removed from the heat source by the large area in contact with the surrounding air and the excellent thermal conductivity. It can effectively allow natural convection heat dissipation. In addition, the metal foam may be lightweight because a plurality of pores are formed. In addition, a plurality of pores of fine and uniform size densely formed in the metal foam may serve to block electromagnetic waves generated from electronic devices.

In addition, the present invention in the manufacture of the metal foam, using a metal powder and activated carbon, without using a material such as a binder for maintaining the shape of the metal foam, the process of sintering the foam foamed by the acid Through, excellent mechanical strength and shape retention A metal foam having can be produced. In addition, as the metal powder is oxidized by the acid, the metal foam may exhibit an insulation effect.

In other words, the metal foam of the present invention contains a metal oxide and activated carbon, which is excellent in thermal conductivity, and excellent heat dissipation characteristics due to the large surface area due to uniformly sized micropores that are densely and evenly distributed in the metal foam. It may represent, and may have excellent durability through sufficient mechanical strength and shape retention of the metal foam. In addition, due to the foaming of the metal powder by the reaction with the acid and the oxidation of the metal powder may exhibit an insulating effect, dense and uniform pores may play a role in blocking the electromagnetic waves. Due to such a characteristic of the metal foam of the present invention, the metal foam of the present invention can be used as a heat sink for electronic equipment such as LED lighting.

Hereinafter, with reference to specific embodiments, it will be described in the metal foam of the present invention and its manufacturing method.

Using aluminum as the metal powder, A slurry was prepared by mixing 30 g of aluminum powder, 1 g of activated carbon, and water. Hydrochloric acid was then added to foam the slurry. Subsequently, the foamed slurry was dried at a temperature of 100 ° C., and then sintered at a temperature of 600 ° C. to prepare a metal foam (hereinafter, Al foam) according to Example 1 of the present invention.

In addition, zinc powder, iron powder, copper powder, and titanium powder are used as metal powders, respectively, and sintering is performed at 400 ° C for zinc, 1500 ° C for iron, 1050 ° C for copper, and 1600 for titanium for melting point temperature of each metal. Metal foams according to Examples 2, 3, 4, and 5 of the present invention (hereinafter, respectively) under substantially the same conditions as those prepared for the Al foam according to Example 1, except that each was carried out at a temperature of Zn foams, Fe foams, Cu foams, and Ti foams).

Subsequently, the foams according to Examples 1 to 5 were configured as heat sinks of an electronic device including an LED chip to measure heat distribution. The heat distribution was measured 3 hours after the operation of the electronics and the heat distribution was measured at each position of the LED chip and the heat sink and the difference was calculated. The test environment temperature was 23 ± 1 ° C. The result is shown in FIG.

2, in the case of the Al foam heat sink, the temperature at the LED chip position is 48.4 ° C, but the temperature of the heat sink is 42.2 ° C, which shows a temperature difference of 6.2 ° C., and in the case of the Zn foam heat sink, Although the temperature of 48.6 degreeC, the temperature in a heat sink shows a temperature difference of 9.0 degreeC to 39.6 degreeC. In addition, the Fe foam heat sink exhibited a temperature difference of 11.3 ° C. with an LED chip of 51.7 ° C. and a heat sink of 40.4 ° C .. It can be seen that there is a difference. In particular, it can be seen that the Ti foam heat sink has a temperature of 52.0 ° C. in the LED chip, but the temperature between the LED chip and the heat sink is 13.4 ° C. at a temperature of 38.6 ° C. in the heat sink.

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

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

	기계적 강도(MPa)Mechanical strength (MPa)	최대하중(Max-load) (kgf)Max-load (kgf)
Al 발포체Al foam	1.971.97	107.2107.2
Zn 발포체Zn foam	4.144.14	210.8210.8
Fe 발포체 Fe foam	2.562.56	138.8138.8
Cu 발포체Cu foam	2.842.84	140.0140.0
Ti 발포체Ti foam	2.302.30	120.0120.0

Referring to Table 1, it can be seen that the mechanical strength of the metal foams according to the embodiments of the present invention are Al foam 1.97, Zn foam 4.14, Fe foam 2.56, Cu foam 2.84, and Ti foam 2.30, respectively, which is according to the present invention. It is meant that the mechanical strength of the metal foams accordingly has a sufficient mechanical strength for use as a heat sink. In particular, the Zn foam of the metal foams of the present invention is the most excellent, relatively low mechanical strength of the Al foam, but it can be seen that the Al foam is also sufficient mechanical strength to be used as the heat sink of the electronic device.

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

Overall, as confirmed with reference to FIG. 2 and Table 1, the metal foams according to the present invention has excellent heat dissipation characteristics and excellent mechanical strength, and thus, can be used as a heat sink of an electronic device.

While the foregoing has been described with reference to preferred embodiments of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated.

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 to form a foam; And

Sintering the foam;

Method for producing metal foams.
The method of claim 1,

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

In the step of sintering the foam,

Sintering at a temperature below the melting point of the metal under an inert gas,

Method for producing metal foams.
The method of claim 1,

The metal powder is selected from among gold (Au), silver (Ag), zinc (Zn), aluminum (Al), iron (Fe), magnesium (Mg), copper (Cu), titanium (Ti), and tin (Sn). Characterized in that it comprises at least one powder,

Method for producing metal foams.
The method of claim 1,

In the forming of the foam,

The foamed slurry is characterized in that the drying by heating at a temperature of less than 300 ℃ over 60 ℃,

Method for producing metal foams.
Metal oxides and activated carbons,

A slurry comprising metal powder and activated carbon is formed by foaming and curing,

Metal foam.
The method of claim 6,

The metal foam is characterized in that the heat sink,

Metal foam.