JP2015120971A - Anodized aluminum alloy member having excellent heat resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anodized aluminum alloy member applied even to an insulation member concerning a semiconductor and a liquid crystal, reconciling high insulation properties (high voltage resistance and high volume resistance) and satisfactory heat radiation properties and further excellent in heat resistance (high temperature crack resistance).SOLUTION: Provided is an anodized aluminum alloy member composed of: an aluminum alloy base material satisfying 0.02 to 4.0% Cu, 0.05% or lower of Si and 0.05% or lower of Fe; an anodization film thereof; and a film in which at least a part of the anodization film is coated or surface-modified with an insulator, and also, the number of intermetallic compounds with the maximum length of 4 μm or higher is 40 pieces or lower per mmof the optional cross-section.

Description

  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 related to 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 at the same time achieving both 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.

  With respect to insulation, the volume resistivity (electrical resistivity) must be large and the voltage resistance 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”) Is high). 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 proposes a technique for reducing the number of intermetallic compounds in the base material and improving the voltage resistance of the member by increasing the purity of the aluminum alloy used as the metal base material. Has been. 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 that has improved withstand voltage properties 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 Patent Laid-Open No. 2002-241992 JP 2010-283342 A

  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 Cu: 0.02% or more and 4.0% or less (meaning mass%, the same applies to chemical components), Si: 0.05 %, Fe: 0.05% or less of an aluminum alloy base material and an anodized film formed on the surface of the base material, the maximum length existing in the anodized film is 4 μm or more The number of intermetallic compounds per 1 mm ^{2 in} an arbitrary cross section is 40 or less, and at least a part of the anodized film has a composite film structure in which the surface is coated or modified with an insulator. It is characterized by.

In the anodized aluminum alloy member of the present invention, the aluminum alloy of the base material preferably further contains Mg: more than 3.5% and not more than 6.5%. Furthermore, 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 preferably 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 preferably 2 or more.

  The anodized film is preferably formed by (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 a 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 the surface of the aluminum alloy substrate where the anodized film and the insulator are not coated, or (2) the anodized film and the insulator are coated on the surface of the aluminum alloy substrate. For example, the semiconductor element may be configured to be in contact with copper or a copper alloy, or aluminum or an aluminum alloy in a portion that is not formed. 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 a semiconductor such as a CPU (Central Processing Unit), a power device, an LED (Light Emitting Diode), a solar cell, and a liquid crystal.

  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 base material in the present invention contains a predetermined amount of Cu. The reason for limiting the range of this component is as follows.

(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. Preferably it is 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 becomes excessive and exceeds 4.0%,
The strength becomes too high and rolling becomes difficult. The upper limit with preferable Cu content is 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, it is desirable that the Mg content in the aluminum alloy exceeds 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 upper limit with more preferable Mg content is 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. More preferably, it is 0.03% or more, and further preferably 0.04% or more. However, if the Cr content is excessive and exceeds 0.1%, the crystallized product size becomes coarse. The upper limit with more preferable Cr content is 0.08% or less, More preferably, it is 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. More preferably, it is 0.3% or less. The lower limit of Zn 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 significantly affect the withstand voltage without completing the dissolution are those in which the size (maximum length) of the intermetallic compound present in the anodized film is 4 μm or more, and the number is arbitrary cross section. in is required to be 1 mm ² 40 per (40 / mm ²⁾ or less. 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). In addition, the intermetallic compound made into the measuring object by this invention is an Al-Fe type intermetallic compound, a Mg-Si type 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 the 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 effect can be effectively exhibited, but is generally preferably controlled in the range of 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 anodic oxide film surface (including coating by filling micropores) or the surface. It becomes easy to become a modified composite film structure. 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. When the concentration of phosphoric acid in the treatment solution is too high, it is difficult to increase the thickness of the film. Therefore, the phosphoric acid is preferably 150 g / L or less (more preferably 100 g / L or less) with respect to the oxalic acid. 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.

  What is necessary is just to set the temperature (liquid temperature) at the time of performing an anodizing process in the range which does not lack productivity, and the melt | dissolution of a membrane | film | coat does not generate | occur | produce significantly, and it is preferable to set it as 0 to 50 degreeC in general.

Specifically, the voltage (electrolytic 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 voltage resistance, and may be adjusted according to specifications, but is preferably 8 μm or more (more preferably 15 μm or more) from the viewpoint of voltage resistance. From the viewpoint of heat resistance (high temperature crack resistance) and heat dissipation, it is preferably 150 μm or less, and 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 coating structure has a composite coating structure in which at least a part of the surface of the anodic oxide coating on which porous micropores exist are coated or surface-modified with an insulator (including coating by filling micropores). And a structure in which an insulator is laminated on the anodic oxide film.

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

  In addition, since the structure is such that the fine holes of the anodized film are filled with an insulator, it has the effect of making the film stress in the compressing direction, which is advantageous 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. More desirably, at least a part of the fine pores is filled, covered, or coated. Is surface modification. 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 the insulator used in the present invention, the volume resistivity of the insulator itself is high from the viewpoint of volume resistivity, more preferably, moisture adsorption is low, and from the viewpoint of heat resistance, the heat resistance is low. Although it is preferable that it 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 product), silicon nitride (Si ₃ N ₄ or the like) , Zirconium oxide (such as ZrO ₂ ), titanium oxide (such as TiO ₂ ), titanium nitride (such as TiN), aluminum oxide (Al ₂ O ₃ ), aluminum nitride (such as AlN), and the like. A compound containing at least one of the above, or a compound containing at least one of the basic skeletons of these compounds 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 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, and a compound in which the basic skeleton of the precursor and the basic skeleton after the treatment are mixed may be used. .

  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, when forming a 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 anodic oxide film, and then predetermined. What is necessary is just to dry and heat in atmosphere. Alternatively, a polysilazane having a Si—N bond and having a basic unit of (—R ¹ SiR ² —NR ³ ) [R ¹ , R ² , R ³ is 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 film structure of the anodic oxide film and the insulator manufactured 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 substrate. 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 copper foil (copper alloy) may be formed by a dry process or plating. Not what you want. 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 be directly formed 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, each of the above samples is anodized under the conditions shown in Table 2 below (treatment liquid type, treatment liquid temperature, electrolytic voltage) to produce an anodized film having a predetermined thickness, and after the anodization treatment 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.

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

  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 (Test No. 7), but siloxane and polysilazane were 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, with respect to the obtained anodized aluminum alloy member (in which an insulator was formed) (Test Nos. 1 to 10), the contact angle to water, the volume resistivity, and the voltage resistance (average voltage resistance) were measured by the following methods. ) Was evaluated. These results are shown in the following Table 3 together with the ratio (D / d) of the thickness D of the anodic oxide 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) in a reflected electron image with a magnification of 1000 times for 20 fields or more. If the portion that appears whiter than the parent phase and the portion that appears blacker than the parent phase is the object of measurement and cannot be determined to be a depression on the anodized film, it is possible to determine whether the portion is an intermetallic compound by elemental analysis using EDX. 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]
Approximately 0.5 microliters of pure water is dropped on the surface on which the insulator is formed, and the contact angle with water is measured using a contact angle measuring device (trade name “CA-05 type” manufactured by Kyowa Interface Science Co., Ltd.). did.

[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]
With respect to the withstand voltage of each sample, a withstand voltage tester (“GPT-9802”, trade name: Instec Co., Ltd., DC mode) is used, the + terminal is connected to the gold electrode probe, and contacted on the anodized film. The terminal is connected to the aluminum alloy substrate, a DC voltage (direct current 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. A high withstand voltage per unit film thickness can reduce the film thickness for producing the specified withstand voltage and improve heat dissipation. Therefore, this value passes 50V / μm or more (◯), 60V / Μm or more was regarded as excellent ()) [less than 50 V / μm is rejected (×)].

  From these results, it can be considered as follows. First, test no. Nos. 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. 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 use an aluminum alloy whose Cu content is insufficient (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 increases due to the excess of Si and Fe, resulting in insufficient voltage resistance.

Claims (12)

Cu: 0.02% or more and 4.0% or less (meaning of mass%, the same applies to chemical components), Si: 0.05% or less, Fe: 0.05% or less,
It is composed of an anodized film formed on the surface of this substrate,
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 excellent in heat resistance, 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 of the base material further contains Mg: more than 3.5% and not more than 6.5%. The anodized aluminum alloy member according to claim 1 or 2, wherein the number of intermetallic compounds per 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.   5. The anode according to claim 4, wherein the thickness 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. Oxidized aluminum alloy member.   The anodized aluminum alloy member according to any one of claims 1 to 5, 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 any one of claims 1 to 7, wherein the anodized aluminum alloy member is a compound containing at least one of the basic skeletons and containing a hydrophobic group.   The anodized aluminum alloy member according to any one of claims 1 to 8, 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 surface of the aluminum alloy substrate where the anodized film and the insulator are not covered.   10. The semiconductor element according to claim 1, wherein a semiconductor element is in contact with a portion of the surface of the aluminum alloy substrate that is not coated with an anodized film and an 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.   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 surface of the aluminum alloy base material that is not covered with an anodized film and an insulator.