WO2015076272A1

WO2015076272A1 - Anodized aluminum alloy member having excellent heat resistance

Info

Publication number: WO2015076272A1
Application number: PCT/JP2014/080547
Authority: WO
Inventors: 高田　悟; 角王飯沼; 範洋慈幸
Original assignee: 株式会社神戸製鋼所
Priority date: 2013-11-19
Filing date: 2014-11-18
Publication date: 2015-05-28
Also published as: JP2015120971A; JP6190791B2

Abstract

An anodized aluminum alloy member according to the present invention comprises a base material and an anodic oxide coating film formed on the surface of the base material, wherein the base material comprises an aluminum alloy that containing, in % by mass, 0.02 to 4.0% inclusive of Cu, 0.05% or less of Si and 0.05% or less of Fe, the number of particles of an intermetallic compound which exist in the anodic oxide coating film and have a maximum length of 4 μm or more is 40 particles per 1 mm² on an arbitrary cross section of the anodic oxide coating film, and at least a part of the anodic oxide coating film has such a composite coating film structure that the surface of the part is coated or modified with an insulating material. The anodized aluminum alloy member according to the present invention has both high insulation performance and good heat-dissipating performance and also has excellent heat resistance (cracking resistance at higher temperatures).

Description

Anodized aluminum alloy member with excellent heat resistance

The present invention relates to an anodized aluminum alloy member useful for an insulating member for electronics. For example, it relates to an anodized aluminum alloy member applied to an insulating member for a semiconductor or liquid crystal such as a CPU (Central Processing Unit), a power device, an LED (Light Emitting Diode), a solar cell, etc. The present invention relates to an anodized aluminum alloy member capable of suppressing the occurrence of cracks at a higher temperature while simultaneously achieving high voltage resistance, large volume resistivity) and good heat dissipation.

For example, members that are applied to semiconductors and liquid crystals, such as CPUs (Central Processing Units), power devices, LEDs (Light Emitting Diodes), and solar cells, generate a lot of heat from these elements. At the same time, heat dissipation is required to be good. As materials for members that require such characteristics (hereinafter referred to as “insulating members”), alumina (Al ₂ O ₃ ), silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN), etc. Ceramics have been used. However, these materials are very expensive and may be cracked because they are ceramics.

As a material with low cost, high insulation and good heat dissipation, a substrate with an insulating layer coated with a resin containing a filler having high insulation and good heat dissipation on the surface of the metal substrate, and an anodized film as an insulating layer Attempts have been made.

As for insulation, the volume resistivity (electrical resistivity) must be large and the withstand voltage must be high. From the viewpoint of heat dissipation, the thinner the film itself, the better the heat dissipation. Therefore, the withstand voltage per unit film thickness (voltage value when a predetermined current flows: hereinafter referred to simply as “withstand voltage”). High) is desirable. In addition, the insulation module manufacturing process using an insulating member may be exposed to a high temperature atmosphere, and therefore has heat resistance (high temperature crack resistance) so that cracks do not occur at high temperatures. It is also important.

The use of an aluminum alloy member (anodized film-treated aluminum alloy member) in which an anodized film is formed on the surface of an aluminum alloy as an insulating member has also been studied. Various techniques for improving the characteristics of the anodized film-treated aluminum alloy member have been proposed so far.

As such a technique, for example, Patent Document 1 discloses a technique for improving the voltage resistance of a member by increasing the purity of an aluminum alloy used as a metal substrate to reduce the number of intermetallic compounds in the substrate. Proposed. However, in such an anodized aluminum alloy member, there is a concern that cracks may occur in the anodized film at high temperatures, resulting in a decrease in insulation.

On the other hand, Patent Document 2 proposes a metal substrate with an insulating layer for solar cells, in which the withstand voltage is improved by reducing metal Si in the aluminum alloy as much as possible. Also in this technique, only the anodic oxide film is formed on the surface of the base material, and there is a problem that the leakage current tends to increase on the high voltage side and the insulating property tends to decrease.

Japanese Unexamined Patent Publication No. 2002-241992 Japanese Unexamined Patent Publication No. 2010-283342

The present invention has been made by paying attention to the circumstances as described above, and its purpose is to achieve both high insulation (high voltage resistance, large volume resistivity) and good heat dissipation, as well as heat resistance ( An object of the present invention is to provide an anodized aluminum alloy member excellent in high temperature crack resistance).

The anodized aluminum alloy member of the present invention that has achieved the above object is, in mass%, Cu: 0.02% to 4.0%, Si: 0.05%, Fe: 0.05% A maximum length existing in the anodic oxide film, which is composed of a base material made of an aluminum alloy satisfying the following (hereinafter also referred to as “aluminum alloy base material”) and an anodic oxide film formed on the surface of the base material. A composite film structure in which the number of intermetallic compounds having a thickness of 4 μm or more per 1 mm ^{2 in} an arbitrary cross section is 40 or less, and at least a part of the anodized film is coated or surface-modified with an insulator. It is characterized by becoming.

In the anodized aluminum alloy member of the present invention, the aluminum alloy preferably further contains, by mass%, Mg: more than 3.5% and 6.5% or less. It is also a preferable requirement that the number of intermetallic compounds per 1 mm ² is 15 or less.

The thickness D of the anodized film is preferably 8 μm or more and 150 μm or less. The thickness d of the insulator from the surface of the anodized film is 10 μm or less, and the ratio (D / d) of the thickness D of the anodized film to the thickness d of the insulator is 2 or more. Is preferred.

The anodized film is preferably formed of (a) an anodizing solution containing at least oxalic acid, or (b) an anodizing solution containing at least oxalic acid and phosphoric acid.

Examples of the insulator include silicon oxide, siloxane resin, polysilazane, silicon nitride, zirconium oxide, titanium oxide, titanium nitride, aluminum oxide, and a compound containing aluminum nitride, or these compounds And compounds containing at least one of the basic skeletons and containing a hydrophobic group.

In the anodized aluminum alloy member of the present invention, it is preferable that the contact angle with water at the surface portion of the composite coating structure is 75 ° or more.

For example, in a power module insulation / heat dissipating structure, as a preferred embodiment of the anodized aluminum alloy member of the present invention, a composite film structure (an anodized film coated with an insulator) necessary for insulation is necessary for insulation. Therefore, it is desirable that only one surface necessary for insulation has a composite film structure. Because the anodized film is formed by dipping in a solution and subjecting it to electrolytic treatment, a film is basically formed on the entire surface of the member, but the part necessary for insulation is basically one side, Another reason is that it hinders heat dissipation.

That is, it is sufficient that only the part necessary for insulation has a composite coating structure. For example, in a composite member having a composite coating structure on one side, a structure in which a semiconductor element is placed on the side without the composite coating structure is (1) A semiconductor element is bonded to a portion of the aluminum alloy substrate surface that is not coated with the anodized film and the insulator, or (2) the anodized film and the insulator are formed on the surface of the aluminum alloy substrate. For example, the semiconductor element may be in contact with an uncoated portion with copper or a copper alloy, or aluminum or an aluminum alloy interposed therebetween. Further, as a structure in which the cooling part is placed on the side having no composite film structure, the aluminum alloy member of the present invention is used for the cooling structure, and the composite film structure of the present invention is arranged on the aluminum alloy member. That is, (3) The surface of the aluminum alloy substrate is configured such that the cooling solution is in contact with a portion where the anodized film and the insulator are not coated.

According to the present invention, the chemical composition of an aluminum alloy used as a base material and the size and number of intermetallic compounds present in the anodized film are appropriately defined, and at least a part of the anodized film is coated with an insulator. Alternatively, an anodized aluminum alloy member having high insulation, good heat dissipation, and heat resistance (high temperature crack resistance) can be realized by forming a composite film structure with a surface modification. Such anodized aluminum The alloy member is extremely useful as an insulating member applied to semiconductors such as CPU (Central Processing Unit), power devices, LEDs (Light Emitting Diode), solar cells, and liquid crystals.

The present inventors aim to realize an anodized aluminum alloy member that has both high insulation (high voltage resistance, large volume resistivity) and good heat dissipation, and also has high temperature crack resistance. Considered from various angles. As a result, the chemical composition of the aluminum alloy used as the base material and the size and number of intermetallic compounds present in the anodized film should be properly specified, and at least a part of the anodized film should be covered or surface-modified with an insulator. The present invention has been completed by finding that the composite film structure can have these characteristics. Hereinafter, each requirement prescribed | regulated by this invention is demonstrated.

The aluminum alloy used as a substrate in the present invention contains a predetermined amount of Cu, and the reason for limiting the range of this component is as follows. In the following, each chemical component amount (%) means mass%. In the present specification, the percentage based on mass (% by mass) is the same as the percentage based on weight (% by weight).

(Cu: 0.02% to 4.0%)
Cu is an element effective for improving the heat resistance (high-temperature crack resistance) of the anodized film, and its performance is further improved particularly when Mg coexists. From such a viewpoint, it is necessary to contain Cu by 0.02% or more. The Cu content is preferably 0.03% or more. Further, when Mg is not included in the components of the aluminum alloy, the Cu content is preferably 0.1% or more, and more preferably 0.5% or more.

Cu is an element that improves the strength. By increasing the strength, the thickness of the base material can be reduced, so that heat dissipation is improved (reducing thermal resistance: reducing obstacles to heat conduction). Can do. However, if the Cu content is excessive and exceeds 4.0%, the strength becomes too high and rolling becomes difficult. The Cu content is preferably 3.0% or less.

The basic components in the aluminum alloy of the present invention are as described above, and the balance is Al and unavoidable impurities, but Si and Fe in the unavoidable impurities must be suppressed as follows. Further, it can be allowed to contain Mg, Cr, Zn or the like as required.

(Si: 0.05% or less, Fe: 0.05% or less)
Fe produces an Al—Fe intermetallic compound, Si produces an Mg—Si intermetallic compound, and these intermetallic compounds cause a decrease in voltage resistance. In order to make it below a predetermined value, it is necessary to suppress both to 0.05% or less. In order to obtain higher voltage resistance, it is preferable to make each 0.02% or less.

(Mg: more than 3.5% and 6.5% or less)
Mg is an element that improves the strength of the base material. By increasing the strength, the thickness of the base material can be reduced, so that heat dissipation can be increased (heat resistance can be reduced). Moreover, the higher the Mg content in the aluminum alloy, the faster the film formation rate of the anodized film, and the lower the production cost. For these reasons, the Mg content in the aluminum alloy is desirably contained in excess of 3.5%, more preferably 3.6% or more. However, if the Mg content is excessive and exceeds 6.5%, rolling cracks are likely to occur in the aluminum alloy, which makes rolling difficult. The Mg content is more preferably 6.0% or less.

(Cr: 0.02% to 0.1%)
Similarly to Mg, Cr is an element effective for improving the strength (by refining of recrystallized grains). In order to exhibit such an effect, it is preferable to contain Cr 0.02% or more. The Cr content is more preferably 0.03% or more, and still more preferably 0.04% or more. However, if the Cr content is excessive and exceeds 0.1%, the crystallized product size becomes coarse. The Cr content is more preferably 0.08% or less, still more preferably 0.07% or less.

(Zn: 0.5% or less)
There is no problem even if an element such as Zn that dissolves uniformly in the aluminum alloy does not affect the voltage resistance. In the case of Zn, if it exceeds 0.5%, Zn precipitation nuclei become large, and the grain boundary part is etched deeply by pre-etching to form defects, so that the surface state is not suitable for surface treatment. The Zn content is more preferably 0.3% or less. The lower limit of the Zn content is not particularly defined, but if the content is less than 0.002%, an extremely expensive aluminum alloy ingot is required, so 0.002% or more is preferable. .

(Size and number of intermetallic compounds present in the anodized film)
The factors that lower the voltage resistance are that the intermetallic compound present in the aluminum alloy is not dissolved during the anodizing treatment, but is taken into the anodized film in a substantially metallic state, and the anode formed by dissolution It is a void in the oxide film. Intermetallic compounds that are not dissolved during anodization treatment and remain in the anodized film remain in the anodized film because the surface area per unit mass decreases as the size increases, and it takes time to dissolve. The possibility increases.

In addition, some of the voids formed by melting the intermetallic compound in the aluminum alloy during anodic oxidation are filled with an insulator in the subsequent insulator introduction process, or a part of the inner surface of the void is covered or surfaced. Since the modification is performed, a decrease in withstand voltage at this portion is suppressed. For this reason, the conditions that do not greatly affect the voltage resistance without completing the dissolution are that the size (maximum length) of the intermetallic compound present in the anodized film is 4 μm or more, and the number is arbitrary. It is necessary to make it 40 or less (40 pieces / mm ² ) per 1 mm ^{2 in} cross section. If this requirement is satisfied, sufficient voltage resistance can be exhibited. In order to further improve the voltage resistance, the number is preferably 15 pieces / mm ² or less (more preferably 10 pieces / mm ² or less). The intermetallic compound to be measured in the present invention is an Al—Fe based intermetallic compound, an Mg—Si based intermetallic compound, or non-solid solution Cu.

(Anodized film)
The anodized aluminum alloy member of the present invention is obtained by forming an anodized film on the entire surface or a part (including one surface) of the base material made of the aluminum alloy as described above. It is preferable to use an anodizing solution containing at least oxalic acid or an anodizing solution containing at least oxalic acid and phosphoric acid. This is because high temperature crack resistance can be improved by forming an oxalic acid-based film on the aluminum alloy substrate.

That is, examples of the general anodizing solution include organic acids such as oxalic acid and formic acid, and inorganic acids such as phosphoric acid, chromic acid, and sulfuric acid, but withstand voltage resistance while significantly reducing the occurrence of cracks at high temperatures. From the viewpoint of improving the quality, it is preferable to use an anodizing solution containing at least oxalic acid. The oxalic acid concentration in the anodizing solution may be appropriately controlled so that the desired action and effect can be effectively exhibited. However, it is preferably controlled in the range of about 10 to 40 g / L. (More preferably about 15 to 35 g / L).

Further, by containing phosphorus (P) in the anodic oxide film, the insulator (or a precursor thereof) covers at least a part of the surface of the anodic oxide film (including coating by filling micropores), or It becomes easy to have a composite film structure with surface modification. However, it is difficult to thicken an anodic oxide film containing phosphorus. For these reasons, by using the mixed acid of oxalic acid and phosphoric acid, that is, an anodizing treatment solution containing at least oxalic acid and phosphoric acid, a predetermined thickness can be ensured and a high resistivity is ensured while ensuring a withstand voltage. Realization is possible. If the phosphoric acid concentration in the treatment liquid is too high, it is difficult to increase the thickness of the film. The lower limit of the concentration of P is sufficient if P is included even slightly. Alternatively, P may be introduced into the film by immersing it in a phosphoric acid solution after forming the anodized film with a solution containing an oxalic acid solution.

The temperature (liquid temperature) at the time of anodizing treatment may be set within a range where productivity is not lost and the dissolution of the film does not occur remarkably, and is generally preferably 0 ° C. to 50 ° C.

Specifically, the voltage (electrolysis voltage) during the anodizing treatment is preferably about 5 to 150 V (more preferably 15 to 120 V). Alternatively, the current density of the current that flows during the anodizing treatment is preferably 100 A / dm ² or less (more preferably 30 A / dm ² or less, still more preferably 5 A / dm ² or less). However, since these conditions relate to the composition of the electrolytic treatment solution to be used, the temperature at which the anodic oxidation treatment is performed, the chemical component composition described, and the like, these conditions may be set as appropriate.

The thickness of the anodized film to be formed is an important factor responsible for withstand voltage, and may be adjusted according to specifications, but is preferably 8 μm or more (more preferably 15 μm or more) from the viewpoint of withstand voltage. From the viewpoint of heat resistance (high temperature crack resistance) and heat dissipation, the thickness of the anodic oxide film to be formed is preferably 150 μm or less, more preferably 100 μm or less.

(Composite film structure of anodized film and insulator)
In the anodized aluminum alloy member of the present invention, at least a part of the anodized film has a composite film structure in which the surface is coated or surface-modified with an insulator. Such a composite film structure means that an insulating material covers or modifies at least a part of the surface of the anodic oxide film in which fine pores are present (including coating by filling micropores). A structure in which an insulator is laminated on the anodized film is also included.

By using a composite film structure of an anodized film and an insulator, the large surface area of the surface of the anodized film where micropores exist can be reduced by filling the micropores. Further, although the surface resistance is lowered due to the adhesion of moisture, the adhesion moisture can be reduced by coating or surface modification with an insulator. That is, the volume resistivity can be improved.

Also, since the structure is such that the fine pores of the anodized film are filled with an insulator, it has the effect of making the film stress in the compressing direction, and therefore acts advantageously from the viewpoint of heat resistance. The lamination on the anodized film is desired to be as thin as possible from the viewpoint of reducing the thermal resistance (reducing the obstacle of heat transfer). For these reasons, the thickness of the insulator is desirably 10 μm or less, and more preferably 5 μm or less.

From the viewpoint of volume resistivity, it is necessary for the insulator to cover or modify at least a part of the surface of the anodized film, and at least a part of the pores are filled, covered, or surface-modified. It is more desirable. As an evaluation method, element identification in a micropore by EDX etc. is mentioned. More preferably, at least a part of the fine holes is filled with an insulating material, coated, or surface-modified, and the thickness on the anodized film is 0.001 μm or more. When the thermal conductivity of the insulator is lower than the thermal conductivity of the anodized film, the ratio of the thickness D of the anodized film to the thickness d of the insulator (D / d) should be set to 2 or more. Is preferable (more preferably 5 or more). From the standpoint of increasing the volume resistivity, the upper limit value of this ratio (D / d) is not particularly defined since it is sufficient that the insulator covers and / or modifies at least part of the anodized film. However, from the viewpoint of coating and surface modification, it is preferably set to 100,000 or less (more preferably 50000 or less).

As an insulator used in the present invention, from the viewpoint of volume resistivity, the insulator itself preferably has a high volume resistivity, and more preferably has little moisture adsorption. Further, from the viewpoint of heat resistance, heat resistance is preferable. The insulator used in the present invention is not particularly defined. For example, silicon oxide (SiO ₂ or the like), siloxane resin (siloxane-based SOG or the like), polysilazane (including heat-treated material), silicon nitride (Si ₃₎ N ₄ etc.), zirconium oxide (ZrO ₂ etc.), titanium oxide (TiO ₂ etc.), titanium nitride (TiN etc.), aluminum oxide (Al ₂ O ₃ ), aluminum nitride (AlN etc.), etc. A compound containing at least one of these, or a compound containing at least one of the basic skeletons of these compounds, etc. can be appropriately selected and used. These compounds may contain organic substances, organic components, and the like. For example, in order to prevent adhesion of moisture, it is preferable to include a hydrophobic group (hydrophobic functional group) such as a fluoro group and an alkyl group.

From the standpoint of preventing moisture adhesion, the surface portion of the composite film structure in which at least a part of the anodized film is coated or surface-modified with an insulating material has a water contact angle of 75 ° or more. It is preferable that A high contact angle means that the surface portion of the composite film structure is hydrophobized, the amount of water present in the surface portion can be reduced, and the electrical resistance at the surface portion can be increased. As a result, the volume resistivity can be further increased. Increasing the contact angle is achieved by including a hydrophobic group such as a fluoro group or an alkyl group in the insulator as described above. This contact angle is more preferably 85 ° or more, and still more preferably 95 ° or more. The upper limit of the contact angle is not particularly limited, but is about 160 ° or less (particularly 130 ° or less).

When introducing an insulator with a large molecular weight, it is difficult to introduce it into the micropores existing on the surface of the anodized film. Therefore, after introducing an insulator with a low molecular weight into the micropore in the form of a precursor, a method such as heat treatment To increase the molecular weight. However, there is no inconvenience even if the precursor does not react completely and remains on the anodized film (including the inside of the fine pores). Further, for example, when the basic skeleton is changed by silica conversion in the heat treatment process, such as polysilazane, it is not necessary to completely change the compound. .

As the method of forming the insulator, the above-mentioned various substances are applied to chemical vapor phase methods such as CVD, electrochemical processes such as dip coating, spin coating, spray coating, roll coating, screen coating electroless wet process, and electrodeposition. Can be adopted. Further, the compound thus introduced may be polymerized by heat treatment, ultraviolet irradiation, etc., and chemical bonding with the anodized film may be promoted.

For example, in the case of forming siloxane-based SOG (spin-on-glass) as an insulator by a wet process, a siloxane polymer having a Si—O—Si bond (siloxane bond) is spin-coated on the surface of the anodized film, and then predetermined What is necessary is just to dry and heat in atmosphere. Alternatively, polysilazane having a Si—N bond and having a basic unit of (—R ¹ SiR ² —NR ³ ) [R ¹ , R ² , R ³ are H or an alkyl group] is spin-coated on the surface of the anodized film. Then, it may be dried and heated in a predetermined atmosphere (see Examples below).

The composite anodic oxide film / insulator composite film structure produced as described above is preferably thin from the viewpoint of improving heat dissipation, and thick from the viewpoint of increasing insulation. In order to make these characteristics compatible, it is recommended that the withstand voltage per unit film thickness is high. For these reasons, the withstand voltage per unit film thickness is preferably 50 V / μm or more, and more preferably 60 V / μm or more.

(Insulation module structure)
The anodized aluminum alloy member of the present invention is characterized in that an anodized film and an insulator are formed on at least a part of an aluminum alloy used as a base material. That is, the entire surface of the aluminum alloy base material may have a composite film structure of this anodized film and insulator, but it is sufficient that a part of the aluminum alloy base material has this structure.

From the viewpoint of mounting a semiconductor element, for example, a member having a composite film structure on one side is manufactured, and the semiconductor element is directly bonded to the aluminum alloy side without the composite film structure, or via a copper (including copper alloy) material. Can be joined. Solder or brazing material can be used for joining at this time, but the method is not particularly specified. The copper material refers to copper or a copper alloy, and a clad material of aluminum and copper (including copper alloy) or a copper foil (copper alloy) may be formed by a dry process or plating. It is not specified. Further, the device may be arranged directly on the composite film structure side or via a copper material. Moreover, when arrange | positioning a semiconductor element directly to a composite-film structure, the said insulator can also be used instead of an adhesive agent.

From the viewpoint of cooling, for example, when producing a member having a composite film structure on one side, the composite film structure can also be formed directly on the aluminum alloy of the cooling base material. Further, the side of the composite film structure can be joined to the cooling side, and the joining method is not limited, but the insulator can be used for joining with the cooler.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, and can be implemented with modifications within a range that can meet the above and the following purposes. These are all included in the technical scope of the present invention.

The aluminum alloy having the chemical composition shown in Table 1 below is subjected to homogenization heat treatment at a temperature of 500 ° C. at a temperature of 500 ° C., and cold-rolled until the plate thickness reaches 1.5 mm, by a conventional method. Then, annealing was performed at a temperature of 350 ° C., a 45 mm × 45 mm × 1.5 mm ^t base material was cut out, and the surface was ground by 50 μm to prepare a sample. In Table 1, “-” indicates no addition (below the measurement limit).

The sample (base material) cut out as described above was immersed in a 50 ° C.-15% NaOH aqueous solution for 2 minutes as a degreasing step, and then washed with water. Next, as a desmutting step, the sample that had undergone the above degreasing step was immersed in a 40 ° C.-20% nitric acid solution for 2 minutes and then washed with water to clean the surface.

Next, after each sample was anodized under the conditions shown in Table 2 below (treatment liquid type, treatment liquid concentration, treatment liquid temperature, electrolytic voltage) to produce an anodic oxide film having a predetermined thickness. Then, it was washed with water and dried to obtain various anodized aluminum alloy members having an anodized film formed on the surface of the substrate.

The surface of the obtained anodized aluminum alloy member was coated with a siloxane polymer or polysilazane as a raw material to form an insulator. At this time, in the sample using the siloxane polymer, spin coating was performed with a siloxane polymer in which 15% by mass of methyl groups in total were bonded to Si atoms of the Si—O—Si bond (siloxane bond), and 350 ° C. (nitrogen atmosphere). ) For 1 hour to form an insulator (siloxane-based SOG) on the anodized film. The film thickness was adjusted by diluting the chemical solution (using IPA) and adjusting the spin coating conditions, and increasing the film thickness by repeating the above steps several times. In a sample using polysilazane, a compound in which two methyl groups are bonded to Si atoms constituting the monomer unit in all monomer units and one methyl group is further bonded to N atoms is diluted with butyl acetate. Thereafter, spin coating was performed, and heating was performed at 200 ° C. (atmospheric atmosphere) for 0.5 hour to form an insulator on the anodized film.

The thickness d of the insulator was estimated from the cross section SEM of the sample. Further, when the micropores of the anodized film and the elements present on the film surface were investigated by EDX analysis, Si was not detected in the sample in which the insulator was not formed (Trial No. 7), but siloxane or polysilazane was added. From the sample used as a raw material, Si was detected from the micropores and the coating surface.

After anodizing under various conditions, the size and number of intermetallic compounds in the anodized film, the occurrence of high temperature cracks on the insulator surface, and the thickness D of the anodized film are measured by the following methods. In addition, the obtained anodized aluminum alloy member (formed with an insulator) (Test Nos. 1 to 10, but Test No. 7 does not form an insulator) was contacted with water by the following method. The corners, volume resistivity and withstand voltage (average withstand voltage) were evaluated. These results are shown in the following Table 3 together with the ratio (D / d) of the thickness D of the anodized film to the thickness d of the insulator (in Table 3, “−” means unmeasured).

[Measurement of size and number of intermetallic compounds in anodized film]
The surface of the anodized film was observed with a scanning electron microscope (SEM) over 20 fields of view in a reflected electron image with a magnification of 1000 times. If the part that appears whiter than the mother phase and the part that appears blacker than the mother phase is the object of measurement and cannot be judged as a depression on the anodic oxide film, the element is analyzed by EDX to determine whether it is an intermetallic compound. Judgment was made. The maximum length was determined by image processing, the number of intermetallic compounds having a maximum length of 4 μm or more was measured, and the number per unit area (number density) was calculated.

[Evaluation of high temperature cracks on insulator surface]
The occurrence of high-temperature cracks was evaluated by visually observing the surface of the composite coating structure with a microscope (magnification: 200 times) after heating each sample in an atmospheric furnace at 350 ° C. for 5 minutes. . And when the clear crack existed on the anodic oxide film surface, the high temperature crack resistance was judged as bad (x), and when the crack was not visible, the high temperature crack resistance was judged as good (◎).

[Measurement of thickness D of anodized film]
The thickness D of the anodized film was measured using an eddy current film thickness meter. In the measurement, the same part was measured five times, the average value was taken as the thickness of the part, the sample was measured at five places (so that the whole measurement was possible), and the average was taken as the thickness D of the anodized film.

[Measurement of contact angle with water]
About 0.5 microliters of pure water is dropped on the surface on which the insulator is formed (however, for test No. 7, the surface on which the anodized film is formed), and a contact angle measuring device (trade name, manufactured by Kyowa Interface Science Co., Ltd.) The contact angle with water was measured using “CA-05”.

[Measurement of volume resistivity]
After confirming the high-temperature crack resistance and confirming that there was no crack, the sample was stored for 7 days in an environment of 50% humidity and 25 ° C., and then φ3 mm of gold was deposited on the sample to form an electrode. Advantest R8340A Using a digital ultra-high resistance / microammeter, the + terminal is connected to the gold electrode, the-terminal is connected to the aluminum alloy substrate, and a DC voltage (DC voltage) of 500 V is applied, and the current flowing at that time is measured. Thus, the volume resistivity (Ωcm) of each sample was obtained. The volume resistivity (test No. 7) of the anodized film is 2.3 × 10 ⁹ (2.3E9) Ωcm, and the volume resistivity is not sufficient. A volume resistivity of 1.0 × 10 ¹² (1E12) Ωcm or more, which is improved by 3 digits or more, is assumed to be a good volume resistivity, and 1.0 × 10 ¹² (1E12) Ωcm or more, 1.0 × 10 ¹³ (1E13) ) Less than Ωcm was accepted (◯), and 1.0 × 10 ¹³ (1E13) Ωcm or more was judged as excellent (◎) [less than 1.0 × 10 ¹² (1E12) Ωcm was rejected (×)].

[Measurement of average withstand voltage]
The withstand voltage of each sample was measured by using a withstand voltage tester (“GPT-9802”, trade name: Instec Co., Ltd., DC mode), connecting the + terminal to the gold electrode probe and contacting it on the anodized film. The-terminal is connected to an aluminum alloy substrate, a DC voltage (DC voltage) is gradually applied, and the voltage (average value at 10 measured points) when a current of 1 mA or more flows is defined as the average withstand voltage. did. In measurement, in order to avoid creeping discharge, measurement was performed while N ₂ gas was blown onto the gold electrode.

The withstand voltage (V / μm) per unit thickness was determined by dividing the measured average withstand voltage by the thickness (total thickness) of the hybrid structure. When the withstand voltage per unit film thickness is high, the film thickness for producing the specified withstand voltage can be reduced, and the heat dissipation can be improved. Therefore, this value passes 50 V / μm or more (◯), 60 V / μm or more was considered excellent (() [less than 50 V / μm is rejected (×)].

From these results, it can be considered as follows. First, test no. Examples 1 to 6 are examples that satisfy the requirements defined in the present invention, and it can be seen that good voltage resistance is exhibited without cracks occurring at high temperatures. Moreover, the volume resistivity also shows a high value.

In contrast, test no. Examples 7 to 10 are examples that do not satisfy the requirements defined in the present invention, and any of the characteristics is deteriorated. That is, test no. 7 is an anodized aluminum alloy member which does not form an insulator having a composite structure, has a small contact angle with water, and has a volume resistivity of 2.3 × 10 ⁹ (2.3E9) Ωcm. It is low.

Test No. Nos. 8 and 10 are those using an aluminum alloy with insufficient Cu content (not added) as a base material, and the high temperature crack resistance is deteriorated (voltage resistance and volume resistivity are not measured). ). Test No. No. 9 uses an aluminum alloy containing excess Si and Fe as a base material, and the number of intermetallic compounds is increased due to excess Si and Fe, resulting in insufficient voltage resistance.

Although the invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on a Japanese patent application filed on November 19, 2013 (Japanese Patent Application No. 2013-239177), which is incorporated by reference in its entirety.

Claims

A base material made of an aluminum alloy satisfying Cu: 0.02% or more and 4.0% or less, Si: 0.05% or less, Fe: 0.05% or less by mass%, and formed on the surface of the base material. An anodized film,
The number per 1 mm 2 in an arbitrary cross section of an intermetallic compound having a maximum length of 4 μm or more present in the anodized film is 40 or less,
An anodized aluminum alloy member characterized in that at least a part of the anodized film has a composite film structure whose surface is covered or modified with an insulator.
The anodized aluminum alloy member according to claim 1, wherein the aluminum alloy further contains, by mass%, Mg: more than 3.5% and not more than 6.5%.
The anodized aluminum alloy member according to claim 1, wherein the number of intermetallic compounds per 1 mm 2 is 15 or less.
The anodized aluminum alloy member according to claim 1, wherein a thickness D of the anodized film is 8 μm or more and 150 μm or less.
The thickness of the said insulator from the said anodic oxide film surface is 10 micrometers or less, and ratio (D / d) of the thickness D of the said anodic oxide film and the thickness d of the said insulator is 2 or more. Anodized aluminum alloy member.
The anodized aluminum alloy member according to claim 1, wherein the anodized film is formed of an anodizing solution containing at least oxalic acid.
The anodized aluminum alloy member according to claim 1, wherein the anodized film is formed of an anodizing solution containing at least oxalic acid and phosphoric acid.
The insulator is a compound containing at least one of silicon oxide, siloxane resin, polysilazane, silicon nitride, zirconium oxide, titanium oxide, titanium nitride, aluminum oxide, and aluminum nitride, or of these compounds The anodized aluminum alloy member according to claim 1, wherein the anodized aluminum alloy member is a compound containing at least one of basic skeletons and containing a hydrophobic group.
The anodized aluminum alloy member according to claim 1, wherein a contact angle with water at a surface portion of the composite film structure is 75 ° or more.
The anodized aluminum alloy member according to any one of claims 1 to 9, wherein a semiconductor element is bonded to a portion of the substrate surface that is not covered with the anodized film and the insulator.
10. The semiconductor device according to claim 1, wherein a semiconductor element is in contact with a portion of the base material surface not covered with the anodized film and the insulator with copper or a copper alloy, or aluminum or an aluminum alloy interposed therebetween. The anodized aluminum alloy member according to any one of the above items.
The anodized aluminum alloy member according to any one of claims 1 to 9, wherein a cooling solution is in contact with a portion of the substrate surface where the anodized film and the insulator are not coated. .