JP2007042859A - Magnesium heat radiating material superior in thermal emissivity and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To develop a light weight heat radiating material superior in absorption and radiation of the thermal energy, by forming a surface layer having a specific composition on the surface of a magnesium alloy. <P>SOLUTION: The light weight radiating material has a spinel structure or porous structure layer containing MgO or Mg(OH)<SB>2</SB>as a main component formed by anodic oxidation with spark discharge or non-spark discharge on the surface of a magnesium alloy. This surface layer has a maximum emissivity of 0.85 or higher at a material temperature of 100°C in an IR range of 4-25 μm, and a surface roughness of Ra 5 μm or less; and the material has color tones of green, blue, purple and reddish yellow, or a hue (H) of 5GY-10YR, a value of color (V) of 1-7 and a chroma (C) of 0.2-12 in the Munsell system. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a magnesium-based metal heat radiating member excellent in heat energy absorbability and heat radiability used in electronic devices such as personal computers and mobile phones having electronic components such as a CPU that generates heat in a main body, and a method for manufacturing the same.

Conventionally, an electronic device having a liquid crystal display device or the like has a built-in circuit board on which electronic components that generate heat during CPU operation are mounted, and various heat malfunctions may occur due to this heat generation. Heat dissipation measures have been taken.

As conventional heat radiating members, metals such as aluminum plates and copper plates, and heat radiating sheets such as carbon fibers have been frequently used. However, these heat radiating materials have low emissivity expressed by heat absorption in the infrared region, particularly in the far infrared region, so that the heat radiating action in a small area is not sufficient. It was. Magnesium-based materials are considered to be useful as heat sinks because they have the same thermal conductivity as other metals and are lightweight, but because of their high activity, they are susceptible to oxidative corrosion and reflect heat on the surface. The rate of heat dissipation is large, the heat absorption into the magnesium material is slow, and the heat dissipation effect is not exerted as expected. Coating is generally performed to prevent oxidative corrosion of the material. However, when the coating is performed, heat absorption is further deteriorated, and there is a problem that an effect as a heat sink becomes insufficient.

On the other hand, various attempts have been made to devise the structure and installation location of heat sinks such as conventionally known aluminum materials, copper materials, or carbon fibers (for example, Patent Document 1 or Patent Document 2), but attempts to improve the materials themselves. There are very few references.
JP-A-11-95871 JP 2000-151164 A

However, if the heat sink material itself is improved, there is an advantage that the structural design, the arrangement location, etc. can be freely selected. The present invention provides a heat sink material that can efficiently absorb and dissipate heat from a heating element while maintaining its original thermal conductivity by changing the surface of a lightweight magnesium material to one with good heat absorption. Objective.

In the infrared or far infrared region of 4 μm or more and less than 25 μm, the present invention has a surface absorption layer having a maximum emissivity of 0.85 or more and a surface roughness Ra of 5 μm or less when the temperature of the object to be measured is 100 ° C. And a heat dissipating material made of magnesium or a magnesium alloy having excellent heat release properties and a method for producing the same.

Production of a heat sink material having such maximum emissivity is performed by subjecting magnesium or a magnesium alloy material to a spark discharge type anodizing treatment in an electrolytic solution containing a metal compound, and containing 50% or more of MgO and a metal oxide. By forming a porous structure film, the maximum emissivity is 0.85 or more and the surface roughness Ra is 5 μm or less when the temperature of the object to be measured is 100 ° C. in the far infrared region where the wavelength is 4 μm or more and less than 25 μm. This is achieved by using a magnesium-based material in which the surface layer is formed.

Further, the heat dissipation material of the present invention is formed by subjecting magnesium or a magnesium alloy material to spark discharge type or non-spark discharge type anodizing treatment to form a porous structure film, and then color treatment, incident angle and measurement angle. In a Munsell display with a glossiness of 0 to 70% and a hue of green, blue, purple and reddish at 85 °, the hue (H) is 5 GY to 10 YR, the lightness (V) is 1 to 7, and the saturation ( C) forms a surface layer in the range of 0.2 to 12, and has a maximum emissivity of 0.85 or more when the temperature of the object to be measured is 100 ° C. in the far infrared region having a wavelength of 4 μm or more and less than 25 μm. It can be manufactured by using a magnesium-based material having a surface layer with a surface roughness Ra of 5 μm or less.

The measurement method of the maximum emissivity is a method of measuring thermal radiation when the temperature of an object to be measured is heated to 100 ° C. in a far infrared region having a wavelength of 4 μm or more and less than 25 μm. The ratio at this time represents the ratio of thermal radiation at the measurement wavelength when the black body is set to 1 (the value when all the light is absorbed) at each wavelength. For reference, reflectance + emissivity = 1. The larger the emissivity value, the better the heat absorption.

In order to produce the heat-dissipating material of the present invention by spark discharge type anodizing treatment, an alkali or alkaline earth metal phosphate, borate, silicate, fluoride salt, bifluoride salt or hydroxide is used. 0.2-7 mol / liter of one or more types, fluoride salt, bifluoride salt, manganate, permanganate, sulfate, and zinc, cobalt, chromium, indium, tungsten as film additives An electrolytic solution containing at least 0.01 to 5 mol / liter of a metal oxide of titanium, molybdenum, iridium, iron, or a cyclic or chain organic compound containing an alcohol group, a carboxyl group, a sulfone group, or the like The above-mentioned electrolysis conditions were performed by performing anodizing treatment while generating spark discharge at a bath temperature of 0 to 60 ° C., a current density of 0.5 to 20 A / dm ² , and a voltage of 20 V or more. A magnesium metal material having a surface with a pinel structure can be formed. In addition, the waveform of the power supply used here is one alternating wave with a frequency of 70 Hz to 2 KHz, a PR wave with 140 to 4000 times / second, or one inverted wave with a positive side of 70 to 2000 / second and a negative side of 70 to 2000 / second It is preferable to use a combination of two or more.

Specific examples of the alkali, alkaline earth metal phosphate, borate, silicate, or hydroxide used here include H ₃ PO ₄ , Na ₃ PO ₄ , Na ₂ HPO ₄ , and NaH _{2. PO 4, Na 4 P 2 O} 6, Na 2 H 2 P 2 O 6, Na 4 P 2 O 7, Na 2 H 2 P 2 O 7, Na 5 P 3 O 10, K 3 PO 4, K 2 HPO ₄ , Phosphate of KH ₂ PO ₄ , K ₄ P ₂ O ₇ , K ₆ (PO ₃ ) ₆ , NaBO ₂ , Na ₂ B ₄ O ₇ , NaBo ₃ , KBO ₂ , K ₂ B ₄ O ₇ Examples thereof include silicates such as acid salts, Na ₂ SiO ₃ , Na ₄ SiO ₄ , K ₂ SiO ₃ , K ₂ SiO _{7, and} K ₂ Si ₄ O ₉ , and hydroxides such as NaOH, KOH, and BaOH.

When manufacturing the heat dissipation material of the present invention by subjecting it to spark discharge type anodization, the electrolyte used therein contains manganese, zinc, cobalt, chromium, indium, tungsten, titanium, molybdenum, iridium, iron, niobium compounds. In this case, a magnesium-based material having a surface layer with a maximum emissivity of 0.85 or more and a surface roughness Ra of 5 μm or less can be obtained without applying a coloring treatment to the formed porous structure film. Of course, this material can be colored.

The surface layer formed here is 50% or more of MgO depending on the anodic oxidation conditions, and Al, Mn, Si, Co, Ti, Ir, Cr, V, W derived from an alloy or electrolyte component as other components. , Mo, Zr, Zn, In, and other various metal oxides. This film has a porous structure and has a thickness of 1 to 80 μm. _MgO · _AL 2 _O Specific examples of the coating components _{3, MgO · SiO 2, MgO} · AL 2 O 3 · SiO 2, MgO · MnO 2, MgO · AL 2 O 3, MgO · V 2 O 3, MgO · _{V 2 O 3 · AL 2 O} 3, MgO · Zn 2 O · Co 2 O 4, MgO · ZnO · AL 2 O 3, MgO · MoO 2, MgO · B 2 O 3, MgO · TiO 2, MgO · AL ₂ O ₃ · _{TiO 2,} but _{MgO · W 2 O 5 · AL} 2 O 3, MgO · W 2 O 5, MgO · AL 2 O 3 · ZrO 2 · SiO 2, MgO · InO 3 and the like, in particular MgO _{· AL 2 O 3, MgO ·} SiO 2, MgO · AL 2 O 3 · SiO 2, MgO · MnO 2, etc. _{MgO · AL 2 O 3 · MnO} 2 is preferred.

In order to produce the heat dissipating material of the present invention by non-spark discharge type anodizing treatment, an alkali or alkaline earth metal carbonate, bicarbonate, silicate, silicofluoride salt, borofluoride salt or hydroxide is used. Using one or more kinds of electrolytes and an electrolytic solution containing the above-mentioned film additive as necessary, the electrolytic conditions are sparked at a bath temperature of 10 to 80 ° C., a current density of 0.05 to 5 A / dm ² and a voltage of 1 to 30 V. A magnesium metal material having the surface of the porous structure can be formed by performing anodizing treatment without causing discharge. As the power supply waveform used here, a DC wave, a pulsating wave, a pulse wave, a PR wave, an inverted wave, and an AC wave having a frequency of 20 Hz to 2 KHz are used. Two or more of these may be used in combination.

Specific examples of the film additive include KF and NH ₄ F as fluoride, NH ₄ FHF, NaFHF and KFHF as bifluoride, and K ₂ MnO ₄ , Na ₂ MnO ₄ and Na as manganate. ₃ MnO _4, etc., KMnO ₄ , NaMnO ₄ , Mg (MnO ₄ ) ₂ , Ca (MnO ₄ ) ₂ , etc. as permanganate, and Na ₂ SiO ₃ , Na ₄ SiO ₄ , K ₂ as silicate compounds For example, SiO ₂ , Na ₂ SiF ₆ , MgSiF ₆ , (NH ₄ ) ₂ SiF ₆ such as silicofluoride, and Na ₂ SO ₄ , K ₂ SO ₄ , AL ₂ (SO ₄ ) ₃ , MgSO ₄ , NaNO _3, KNO _3, etc., _AL 2 _O 3 as a metal _{oxide, H 3 BO 3, SiO 2} , TiO, TiO 2, Ti 2 O _{, VO, V 2 O 3,} VO 2, Mo 2 O 3, Mo 2 O 5, ZrO, SnO, WO, W 2 O 3, W 2 O 5, NbO, NbO 2, MnO, Mn 3 O 4, Mn ₂ O ₄ , MnO ₂ , Mn ₂ O ₇ , Ir ₂ O ₃ , IrO ₂ , IrO, CrO, CrO ₂ , Cr ₂ O ₃ , Cr ₂ O ₅ , CoO, Co ₂ O ₃ , Co ₃ O ₄ , In ₂ O ₃ , In ₂ O, Zn ₂ O, ZrO, etc., and these are also used as metal oxide salts. Examples of the organic compound include (CH ₂ OH) ₂ , (CH ₂ CH ₂ OH) O, (CH ₂ OH) ₂ CHOH and other alcohols, (COOH) ₂ , (CH ₂ CH ₂ COOH) ₂ , [CH (OH ) COOH] ₂ , C ₆ H ₄ (OHCOOH), C ₆ H ₅ COOH, C ₆ H ₄ (COOH) ₂ Any carboxylic acid or salt thereof, C ₆ H ₄ (SO ₃ H · COOH), C ₆ H ₃ An organic compound having a sulfone group such as (COOH.OH.SO ₃ H) is used. These film additives may be used alone or in combination. In particular, when an inorganic compound and an organic carboxylic acid are used in combination, liquid management becomes easy, which is preferable.

The film formed by non-spark discharge type anodizing treatment has a white or gray hue, so it is colored to give a Munsell display with a yellowish hue of green, blue, purple and red. Then, the hue (H) is 5 GY to 10 YR, the lightness (V) is 1 to 7, and the saturation (C) is the surface layer in the range of 0.2 to 12.

The surface layer formed here contains 50% or more of Mg (OH) ₂ and MgO and MgO + Mg (OH) ₂ as other components depending on the anodic oxidation conditions. This film has a porous structure and has a thickness of 1 to 80 μm.

The magnesium metal material used in the present invention can be widely applied, pure magnesium system, magnesium-aluminum system, magnesium-aluminum-zinc system, magnesium-aluminum-silicon system, magnesium-zirconium-rare earth-silver system, magnesium-zinc -Zirconium series, magnesium-zinc series, magnesium-rare earth-zirconium series, magnesium-aluminum-rare earth series, magnesium-yttrium-rare earth series, magnesium-calcium-zinc series, etc. are all available.

The obtained magnesium material has a surface layer with a maximum emissivity in the far-infrared region of 4 to 25 μm of 0.85 or more and a surface roughness of Ra5 or less, and the color tone is green, blue, purple and red. In Munsell display, the hue (H) is 5 GY to 10 YR, the lightness (V) is 1 to 7, and the saturation (C) is 0.2 to 12. The general surface roughness of this material has a smoothness in the range of Ra 0.8 to 2.0 and is excellent as an external part. Moreover, the corrosion resistance is 3 to 5 times that of conventional products.

On the other hand, HAE, which is a representative example of an alkaline anodic oxide film, has a dark brown color from natural color, has an emissivity of 0.8, has a surface roughness of Ra10.8, and has a rough surface like a brick, It cannot be used as an external part. On the other hand, DOW17, which is a representative example of acidic bath anodization, has a dark green color due to natural coloration and an emissivity of 0.7. However, the surface roughness is Ra 7.6, and the surface is as rough as HAE, so it cannot be used as an external part. Further, when no anodizing treatment is performed, the surface oxidation corrosion is remarkable and the heat sink cannot be used for a long time. In addition, the emissivity when the clear coating treatment is applied to prevent oxidation of the surface is about 0.1 or less, and the emissivity can be improved to about 0.9 by applying black coating, Since it is thick, the thermal conductivity is poor, and the effect is inferior to that of conventionally known aluminum plates and copper plates when considering a series of cycles as heat absorption, heat conduction, and heat radiation as a heat sink.

The heat dissipating material of the present invention has excellent heat energy absorbability, conductivity, heat dissipating property, and is lightweight, corrosion resistant, and smooth. It is excellent as a heat dissipating member for use in electronic devices having electronic components, particularly small electronic devices.

Hereinafter, embodiments of the present invention will be specifically described.

After roughing both sides of a magnesium alloy AZ91D die-cast material with a plate thickness of 1 mm and 30 x 30 x t5 mm, and finishing with a diamond tool, the dimensional accuracy is 3.5 ± 0.001 mm and the surface roughness Ra is 0.3 μm. It was. After degreasing and acid-treating this sample, NaOH: 3 ± 0.05 mol / liter, Na ₂ HPO ₄ ; 0.3 mol / liter, Na ₂ SiO ₃ as a film additive: 0.25 mol / liter, and tartaric acid Sodium: 0.3 mol / liter, KF: 0.2 mol / liter of electrolyte added with an AC waveform at a liquid temperature of 24 ± 2 ° C. and 1000 Hz, current density of 1-2 A / dm ² , spark discharge starting voltage The spark discharge type anodizing treatment was performed at about 45 V, final voltage 85 V, and electrolysis time 50 minutes. After washing with water, the dye was treated with black dye (SANDOZ: Deep / Black / MLW: 10 g / L) at 60 ° C. for 20 minutes, followed by sealing and sealing. When the cross section of this film was observed with an electron microscope (JSM-T20 manufactured by JEOL Ltd.), the film thickness was about 20 to 25 μm. When the emissivity was measured in the far-infrared region of 4 to 25 μm at 100 ° C. by FTIR, the emissivity was 0.85 or more in the wavelength region of 8 μm or more. The total emissivity in the entire measurement region was 0.88, and the surface roughness was Ra 1.1 μm. Here, the total emissivity is an integral average value of emissivities at each wavelength in the entire measurement region of 4 to 25 μm.

(Comparative Example 1) The same die casting material, pretreatment and electrolytic solution as in Example 1 were used. However, as the electrolysis conditions, a DC power source was used, the current density was 2.0 ± 0.5 A / dm ² , and the spark discharge starting voltage was 46V. After the anodizing treatment, dyeing and sealing treatment were performed in the same manner as in Example 1. A gray anodic oxide film having an uneven surface with a thickness of 15 to 20 μm was obtained. When the emissivity of this sample was measured in the same manner as in Example 1, the total emissivity was 0.83 in the all-infrared measurement region of 4 to 25 μm. However, the surface roughness is Ra 8.7, and the surface is uneven and cannot be used as a heat sink product.

(Comparative Example 2) The same die casting material, pretreatment and electrolytic solution as in Example 1 were used. As the electrolysis conditions, an AC power source was used, the frequency was 50 Hz, the current density was 2.0 ± 0.5 A / dm ² , and the spark discharge start voltage was 52V. The obtained sample was sealed to obtain a white anodic oxide film having a thickness of 17 to 32 μm. When the emissivity of this sample was measured in the same manner as in Example 1, it did not show 0.85 or more in the far infrared measurement region of 4 to 25 μm, and the total emissivity was 0.2. The surface roughness was Ra 9.6, and the surface was remarkably uneven, and was a glossy porcelain surface. This is not suitable as a heat dissipation material.

The same material and pretreatment as in Example 1 were performed, and the treatment was performed under the same electrolytic conditions as in Example 1 in a solution obtained by adding 15 g / L of KMnO _{4 to} the electrolytic solution of Example 1. The same sealing was performed without performing a coloring treatment after electrolysis. The film thickness was about 20-25 μm. When the emissivity was measured in the far-infrared region of 4 to 25 μm at 100 ° C. by FTIR, the emissivity was 0.9 at all wavelengths of 18 μm or more. The total emissivity in the entire measurement region was 0.87, and the surface roughness was Ra 1.3 μm.

(Comparative Example 3) The same die-cast material as in Example 2 was used, the same pretreatment was applied, and the same electrolytic solution was used, except that a 50 Hz AC power source was used as the electrolysis condition, and the current density was 2.0 ± 0.5 A. / dm ^2, except that the spark discharge starting voltage 48V performs anodization in the second embodiment the same, sealing treatment was carried out in the same manner as in example 2. A brown anodic oxide film having an uneven surface with a thickness of 15 to 30 μm was obtained. This sample showed a total emissivity of 0.82 in the far infrared measurement region of 4 to 25 μm. However, the surface roughness was Ra 11.2, and the unevenness was so severe that it could not be used.

The magnesium material of the present invention can be used as a heat radiating plate component of various electronic components as a lightweight material having a large heat radiating effect inside a precision machine product.

Claims (5)

Magnesium with excellent thermal radiation, having a surface layer with a maximum emissivity of 0.85 or more and a surface roughness of Ra of 5 μm or less when the temperature of the object to be measured is 100 ° C. in the far infrared region where the wavelength is 4 μm or more and less than 25 μm Or heat dissipation material made of magnesium alloy Glossiness is 0 to 70% (incident angle, measurement angle 85 °), color tone is green, blue, purple and reddish yellow, and in Munsell display, hue (H) is 5 GY to 10 YR, brightness (V) is 1 to 7. The magnesium alloy heat dissipation material according to claim 1, wherein the saturation (C) is in the range of 0.2-12. Magnesium or magnesium alloy material is subjected to spark discharge type anodizing treatment to form a porous film having a thickness of 0.5 to 80 μm containing 50% or more of MgO and a derivative or oxide from the alloy or electrolyte. This is colored, the gloss is 0-70% (incident angle, measurement angle 85 °), the color tone is green, blue, purple and reddish yellow, and the hue (H) is 5GY to 10YR in Munsell display. In the far-infrared region where the lightness (V) is in the range of 1 to 7, the saturation (C) is in the range of 0.2 to 12, and the wavelength is 4 μm or more and less than 25 μm, the maximum radiation when the temperature of the object to be measured is 100 ° C. A method for producing a heat dissipation material made of magnesium or a magnesium alloy having excellent thermal radiation, comprising a surface layer with a surface ratio of 0.85 or more and a surface roughness Ra of 5 μm or less Using an electrolyte containing magnesium or a magnesium alloy material containing one or a combination of two or more of manganese, zinc, cobalt, chromium, indium, tungsten, titanium, molybdenum, iridium, iron, and zirconium compounds, and having a frequency of 70 Hz or more Spark discharge type using an AC wave, a PR wave of 140 to 4000 times / second, or a power supply waveform combining one or two or more inversion waves of 70 to 2000 / second on the positive side and 70 to 2000 / second on the negative side Anodized to form a porous type film with a thickness of 0.5 to 80 μm containing 50% or more of MgO and a metal oxide, and in the far infrared region with a wavelength of 4 μm to less than 25 μm It has excellent thermal radiation by forming a surface layer with a maximum emissivity of 0.85 or more and a surface roughness Ra of 5 μm or less when the temperature is 100 ° C. Preparation of thermally conductive material made of magnesium or a magnesium alloy Non-spark discharge type anodizing treatment of magnesium or magnesium alloy material, and a porous type structure film having a thickness of 0.5 to 50 μm containing 50% or more of Mg (OH) ₂ and a derivative from the alloy or electrolyte Formed, and subjected to a coloring treatment, with a glossiness of 0 to 70% (incident angle, measurement angle of 85 °), a hue of green, blue, purple, and reddish yellow, and in Munsell display, the hue (H) is 5GY 10YR, brightness (V) is 1-7, saturation (C) is in the range of 0.2-12, and in the far infrared region where the wavelength is 4 μm or more and less than 25 μm, the temperature of the object to be measured is 100 ° C. A method for producing a heat dissipation material made of magnesium or a magnesium alloy having excellent thermal radiation, comprising a surface layer having a maximum emissivity of 0.85 or more and a surface roughness Ra of 5 μm or less