JP2011021260A - Aluminum substrate and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum substrate which has an adhesion oxide film only on one surface, is used as a coated plate, an adhesive plate and a laminate plate, and is excellent in resin adhesion. <P>SOLUTION: In the method of manufacturing the aluminum substrate 6, the aluminum substrate 6 is arranged between a pair of opposed electrodes 7, 10 so that the aluminum substrate 6 is not electrically connected to both electrode plates, and the surface of the substrate is in parallel to surfaces of the electrodes. Wherein, an electrolytic treatment is performed in an electrolyte 9 of an alkaline aqueous solution of pH 9-13 and 35-85°C, at 4-50 A/dm<SP>2</SP>current density for 5-20 sec while making the potential of one electrode plate higher than that of another electrode plate and changing the potential at the cycle of 20-100 Hz. The aluminum substrate is manufactured by the method. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a surface-treated aluminum substrate, and more particularly, to an aluminum substrate having an adhesive oxide film only on one side and excellent in resin adhesion used as a coating plate, an adhesive plate, and a laminate plate.

  An aluminum plate or an aluminum alloy plate (hereinafter referred to as “aluminum substrate”) is lightweight and has appropriate mechanical properties, and has excellent characteristics such as aesthetics, moldability, and corrosion resistance. Widely used in various containers, structural materials, machine parts, etc.

  In recent years, paying attention to the high thermal conductivity of an aluminum substrate, the use as a printed wiring board is rapidly increasing. That is, with the recent reduction in size and weight of electrical / electronic devices, printed wiring boards are required to have more multilayers, higher integrations and higher densities than conventional ones. A substrate using a conventional insulator cannot dissipate heat generated from electronic components mounted at high density, resulting in circuit instability. On the other hand, by adopting an aluminum substrate having excellent thermal conductivity as the substrate, the electronic components can be cooled by the substrate itself, and the performance of the entire circuit can be improved.

  In general, a printed wiring board using an aluminum substrate is made by attaching a metal foil such as a copper foil to an aluminum substrate. At that time, epoxy resins and polyimide resins are used as adhesives. As an effective technique for improving the adhesion between these resins and the aluminum substrate surface, the aluminum substrate is subjected to AC electrolysis in an alkaline bath. There has been proposed a method of treating and forming an adhesive oxide film on the surface thereof.

For example, in Patent Document 1, an aluminum substrate provided with a through hole is subjected to electrolytic treatment for 8 to 30 seconds with an AC waveform at an electric quantity of 80 to 250 C / dm ² using an alkaline solution having a bath temperature of 40 to 90 ° C. A method of laminating a circuit body on this aluminum substrate after filling a hole with resin and filling the hole is shown.

In Patent Document 2, the aluminum or aluminum alloy plate is subjected to a surface roughening treatment so that the center line average roughness (Ra) is 0.5 to 5 μm, and further has a pH of 9 to 13 and a bath temperature of 35 to 85 ° C. at a current density of 4~50A / dm ² in an alkaline aqueous solution, the time quantity of electricity becomes to exceed 80C / dm ^2, subjected to AC electrolytic treatment, and characterized by forming an oxide film having a thickness of 500~5000Å A printed wiring board manufacturing method is shown.

Japanese Patent Laid-Open No. 09-18140 Japanese Patent No. 2630858

However, the conventional techniques as described above have the following problems.
That is, in the prior art, since the electrolytic treatment is performed by directly connecting to the aluminum substrate, the aluminum substrate itself becomes an electrode. For this reason, the adhesive oxide film is generated on the entire area where the aluminum substrate is in contact with the electrolyte, that is, on both surfaces of the plate.

  On the other hand, in some printed wiring boards, there is a product in which copper foil is bonded to only one surface of an aluminum substrate, while the other surface is left an aluminum substrate. In such products, in order to protect the aluminum substrate in the copper foil etching process for circuit formation and to prevent scratches on the aluminum substrate during transportation, the back surface of the aluminum substrate prior to the copper foil bonding process A masking film is once applied to. The masking film is generally composed of a film composed of a vinyl chloride resin and the like and an adhesive such as an acrylic resin having a low adhesive strength so that it can be easily peeled off. If an adhesive oxide film is formed on both sides of the substrate, even the masking film that has only been temporarily adhered will stick firmly, and in some cases, the adhesive will adhere to the back of the aluminum substrate when the masking film is peeled off. It remained in trouble, such as remaining.

  As a result of repeated studies to solve the above-mentioned problems, the inventors of the present invention do not impair the performance of the adhesive oxide film based on the prior art, and an aluminum base material formed only on a specific surface thereof, In addition, the inventors have found a method for producing the same and made the present invention.

  That is, the present invention is the aluminum substrate having an oxide film on both sides according to claim 1, wherein the oxide film on one surface is an adhesive oxide film having an overall thickness of 10 to 500 nm, An aluminum comprising a barrier layer and a pore structure on the surface side, the pore structure having small holes with a diameter of 5 to 30 nm branched into the inside, and the oxide film on the other surface being a peelable oxide film substrate.

  According to the present invention, in claim 2, the peelable oxide film is (1) a thickness of less than 10 nm or more than 500 nm; (2) no pore structure; (3) a pore structure. Or (4) having a pore structure and having a branched structure, the diameter of the small hole is less than 5 nm or more than 30 nm. It was supposed to satisfy.

According to a third aspect of the present invention, an aluminum substrate that is not connected to both electrode plates is disposed between a pair of opposing electrode plates so that the substrate surface is parallel to both electrode plate surfaces, and the temperature is 35 to 13 at pH 9-13. In an electrolytic solution of an alkaline aqueous solution at ˜85 ° C., the potential of one electrode plate is made higher than that of the other electrode plate and changed at a cycle of 20 to 100 Hz, and the maximum current density is 4 to 50 A / dm. ² and the manufacturing method of the aluminum substrate which is electrolytically treated for 5 to 60 seconds.

According to the present invention, in claim 4, the periodic change in potential is at least one selected from the group consisting of a sine wave, a rectangular wave, a trapezoidal wave, and a triangular wave, and the time indicating the minimum current density is 80% of one period. It was as follows. Further, in the present invention, the difference between the maximum current density and the minimum current density is 2 A / dm ² or more.

  According to the present invention, it is possible to provide an aluminum substrate provided with an adhesive oxide film having a pore structure on one surface and a peelable oxide film on the other surface, and a method for producing the same.

It is a schematic diagram which shows the structure of the aluminum substrate which concerns on this invention. It is a front view which shows the electrolytic device of the aluminum substrate which concerns on this invention. It is a top view which shows the electrolytic device of the aluminum substrate which concerns on this invention. It is a front view which shows the conventional electrolytic device of the aluminum substrate.

Hereinafter, details of the present invention will be described in order.
A. Adhesive oxide film structure on aluminum substrate surface An adhesive oxide film is formed on one surface of the aluminum substrate according to the present invention. In the present invention, “adhesion” refers to, for example, the performance at which the peeled area ratio is 25% or less in the heat-resistant adhesion evaluation described below. The thickness of this oxide film is 10 to 500 nm. When the film thickness is less than 10 nm, the resin adhesion is insufficient because the thickness of the pore structure described later is not sufficient. When the film thickness exceeds 500 nm, the oxide film itself is liable to cause cohesive failure and the resin adhesion is lowered.

  As shown in FIG. 1, the adhesive oxide film 1 is composed of a barrier layer 3 on the aluminum substrate 2 side and a pore structure 4 on the surface side. The barrier layer is a layer of a dense oxide film having a thickness of 3 to 30 nm. This barrier layer imparts corrosion resistance to the aluminum substrate and also provides a strong bond between the aluminum substrate and the pore structure via the barrier layer. On the surface of the oxide film, a pore structure 4 composed of small holes 41 having a diameter of 5 to 30 nm is formed. The pore structure 4 refers to a structure composed of small holes formed over the entire surface of the oxide film 1. This structure increases the contact area between the adhesive and the oxide film interposed between the two when forming a resin layer or the like on the oxide film, and increases the adhesion between the oxide film and the resin layer, etc. It is important. When the diameter of the small hole is less than 5 nm, the contact area with the adhesive or the like is not ensured, and the resin adhesion is lowered. On the other hand, when the thickness exceeds 30 nm, cohesive failure is likely to occur due to the loss of the strength of the oxide film itself, and the resin adhesion also decreases.

  The pore structure 4 extends over the entire surface of the oxide film and reaches the barrier layer 3 in the depth direction. The pore structure 4 has a structure branched in the depth direction. In FIG. 1, the branch point is indicated by 5. This is because when the pore structure 4 is branched inside, the contact area between the adhesive or the like and the oxide film increases, and a kind of anchor effect is exhibited. Specifically, in the process in which the oxide film 1 is formed and grown, the pore structure 4 is not necessarily formed perpendicular to the depth direction, but is formed in various directions. As a result, the small holes merge and branch. It is a structure. The branch point 5 is particularly effective for adhesion when it is formed in a region deeper than 5 nm from the outermost surface of the oxide film. In general, the pore structure in a normal anodic oxide film called anodized is only formed straight in the depth direction, and is greatly different from the present invention in that it does not have a branched structure.

  Although there is no particular limitation on the area of the small holes 41 of the pore structure 4 on the oxide film surface, the apparent area of the oxide film surface (expressed by multiplication of length and width without considering minute irregularities on the surface). The area is preferably 25 to 75%. Further, the depth of the pore structure from the surface of the oxide film is preferably 50% or more of the total thickness of the oxide film.

B. With respect to the peelable oxide film structure on the surface of the aluminum substrate, a peelable oxide film is formed on the surface of the aluminum substrate opposite to that on which the adhesive oxide film is formed. In the present invention, the term “peelability” refers to a performance that can be easily peeled off by hand when the masking film is peeled off by hand. In order to make this oxide film have low adhesion, any one or more of the above characteristics of the adhesion oxide film should be satisfied. That is, (1) the thickness is less than 10 nm or more than 500 nm; (2) it does not have a pore structure; (3) it does not have a branched structure even if it has a pore structure; 4) Even if it has a pore structure and has a branched structure, it is achieved if the diameter of the small hole is less than 5 nm or exceeds 30 nm. When it does not have a pore structure, it is particularly excellent in releasability capable of temporary adhesion. The above (2) to (4) do not hold redundantly, but (1) and (2), (1) and (3), and (1) and (4) overlap. There is a case.

C. About the manufacturing method of an aluminum substrate Although the aluminum substrate which concerns on this invention has the above predetermined pore structures, it is manufactured with the following manufacturing methods. That is, an aluminum substrate that is not connected to both electrode plates is disposed between a pair of opposing electrode plates so that the substrate surface is parallel to both electrode plate surfaces, and an alkaline aqueous solution having a pH of 9 to 13 and a temperature of 35 to 85 ° C. In the electrolyte solution, the potential of one electrode plate is made higher than the potential of one electrode plate, and is changed at a cycle of 20 to 100 Hz, and the maximum current density is 4 to 50 A / dm ² , for 5 to 60 seconds. Examples of the method include electrolytic treatment.

  Conventionally, an apparatus as shown in FIG. 4 is used in electrolytic treatment represented by various alumite treatments. In this method, the aluminum base plate to be treated is used as one electrode 6 and a current is directly passed between the counter electrode 7. In the figure, 8 is an AC power source, and 9 is an electrolytic solution. On the other hand, as shown in FIGS. 2 and 3, the present invention does not connect to the aluminum substrate 6 that is the material to be processed, and therefore does not actively flow current to the aluminum substrate itself. Instead, a pair of opposing electrode plates 7 and 10 are prepared, and the aluminum substrate 6 is disposed so that the substrate surface 61 of the aluminum substrate 6 is parallel to the electrode plate surfaces 71 and 101 of both the electrode plates 7 and 10. . As a result, the aluminum substrate surface 61 is perpendicular to the direction of the current flowing between the two electrode plates 7, 10, whereby charges are indirectly supplied to the aluminum substrate surface. At this time, if the aluminum substrate surface 61 is not perpendicular to the direction of current, the surface of the aluminum substrate 6 to be processed is not sufficiently exposed to the current flowing between the electrode plates 7 and 10, and indirect charge supply is performed. Therefore, the target oxide film is not formed. In FIG. 2, one electrode plate 7 is connected to ground (earth) or a function generator at 11. The other electrode plate 10 is applied with a potential changed at a cycle of 20 to 100 Hz above the potential of one electrode plate. In addition to such an arrangement, an adhesive oxide film can be formed only on one surface of the aluminum substrate by satisfying an electrolysis condition described later.

  Examples of the alkaline aqueous solution used as the electrolyte include aqueous solutions of phosphates such as sodium phosphate, potassium hydrogen phosphate, sodium pyrophosphate, potassium pyrophosphate and sodium metaphosphate; alkalis such as sodium hydroxide and potassium hydroxide. Metal hydroxide aqueous solution; ammonium hydroxide aqueous solution; and mixtures thereof. As described later, since it is necessary to maintain the pH of the electrolytic solution in a specific range, an aqueous solution of a phosphate capable of obtaining a buffer effect is preferable. Note that a surfactant may be added to the alkaline aqueous solution in order to improve the dirt removing ability. The electrolyte concentration in the electrolytic solution is appropriately selected so as to obtain a desired electrolytic solution resistance, but is usually 0.01 to 0.5 mol / liter.

  The pH of the electrolytic solution is 9 to 13, preferably 9.5 to 12. If the pH is less than 9, the alkaline etching power of the electrolytic solution is weak, so that the oxide film becomes an irregular film and the formation of the predetermined pore structure and barrier layer becomes incomplete. On the other hand, if the pH exceeds 13, the alkaline etching force becomes excessive, so that the oxide film is difficult to grow, and the formation of a predetermined pore structure and barrier layer is also inhibited.

  Electrolyte temperature is 35-85 degreeC, Preferably it is 40-70 degreeC. When the electrolyte temperature is less than 35 ° C., the alkaline etching power is insufficient, so that the predetermined pore structure of the oxide film and the formation of the barrier layer become incomplete, and when it exceeds 85 ° C., the alkaline etching power becomes excessive, the oxide film. Is difficult to grow, and the formation of a predetermined pore structure and barrier layer is also inhibited.

  In the electrolytic treatment of the present invention, the oxide film having a predetermined pore structure needs to be formed only on one surface of the aluminum substrate. The thickness of the oxide film is controlled by the quantity of electricity, that is, the product of the current density and the electrolysis time. Basically, the thickness of the oxide film increases as the quantity of electricity increases. The predetermined pore structure is formed by passing a current having an appropriate frequency. Therefore, the electrolytic treatment conditions must be as follows.

  First, it is necessary to periodically change the potential of the electrolytic treatment with respect to the potential of one electrode plate with the potential of the other electrode plate being higher than that. This is achieved, for example, by grounding (grounding) one electrode plate and applying a positive potential that periodically changes to the other electrode plate. By applying such a potential, a current flowing in only one direction and periodically changing in amount flows between both electrode plates. By exposing the aluminum substrate between the two electrode plates, electric charge is supplied only to the surface of the aluminum substrate on the higher potential side, and an adhesive oxide film is formed on the surface. In the potential between the electrode plates, one side is negative and one side is positive. For example, when alternating voltage is applied between both electrode plates, the direction of the current is periodically reversed. Electric charges are evenly supplied to both surfaces, and as a result, an adhesive oxide film is formed on both surfaces.

  The period for changing the potential is 20 to 100 Hz. If it is less than 20 Hz, the direct current element increases as the electrolytic treatment, and as a result, the diameter of the pores having the pore structure becomes too small, less than 5 nm. On the other hand, when the frequency exceeds 100 Hz, the change in current is too fast and coarse pores are formed, so that a small hole diameter of 30 nm or less cannot be achieved. The waveform, the minimum voltage, and the maximum voltage may be arbitrarily changed within one period.

Current density in the aluminum substrate, the maximum value in the periodic variation of the current is required to be 4~50A / dm ^2. The current density in the aluminum substrate is the current value divided by the area of the aluminum substrate through which the current passes. When this current density does not reach 4 A / dm ² during the periodic change, the film formation reaction becomes incomplete and a predetermined pore structure cannot be obtained. On the other hand, when the maximum current density exceeds 50 A / dm ² , the current density becomes excessive, so that it is difficult to control the oxide film shape, and a predetermined pore structure cannot be stably obtained. Although there are various factors such as power supply voltage, distance between electrode plates, electrode plate area, and electrolyte resistance to control the current density, it is the easiest and most reliable to control the power supply voltage as technical common sense. It is.

  The electrolysis time is 5 to 60 seconds. This is because if the treatment time is less than 5 seconds, the formation of the oxide film is too rapid, and the predetermined pore structure is not sufficiently formed, resulting in an oxide film composed of amorphous aluminum oxide. On the other hand, if it exceeds 60 seconds, the oxide film is redissolved and a predetermined pore structure cannot be obtained, and productivity is also lowered, which is not preferable.

  In order to change the voltage periodically, a function generator or the like is used. In order to obtain a good oxide film, for example, a sine wave, a rectangular wave, a trapezoidal wave, or a triangular wave can be used as a waveform that can be easily obtained by a function generator.

Furthermore, if the difference between the maximum current density and the minimum current density is 2 A / dm ² or more in one cycle current density, the effect of periodically changing the current is sufficiently exhibited, and the adhesion oxide film is more stable. Can be formed.

In addition, in order to confirm the structure of the oxide film in the present invention, it is necessary to observe the cross section by magnifying it about 50,000 to 100,000 times. For this purpose, cross-sectional TEM observation is preferably used. It is done. Cross-sectional TEM observation is performed by processing an observation object into a thin piece with an ultramicrotome or the like.
As a material of the aluminum substrate used in the present invention, pure aluminum or an aluminum alloy is used, and can be appropriately selected according to required characteristics. As the aluminum alloy, 1000 series, 3000 series, 5000 series, 6000 series and the like are particularly preferably used. As the aluminum substrate, an aluminum plate having a thickness of usually 0.1 to 2.0 mm is preferably used.

  Hereinafter, preferred embodiments of the present invention will be specifically described based on examples and comparative examples.

Examples 1-19 and Comparative Examples 1-13
As the aluminum substrate, a JIS 5052 alloy plate measuring 100 mm long × 100 mm wide × 1.0 mm thick was used. An aluminum substrate was disposed between a pair of opposing electrode plates so that they were not connected to each other so that the substrate surface was parallel to both electrode plate surfaces and subjected to electrolytic treatment. As the electrolytic solution, an alkaline aqueous solution mainly composed of sodium pyrophosphate having the pH and temperature shown in Table 1 was used. The electrolyte concentration of the alkaline aqueous solution was 0.05 mol / liter. A graphite plate was used for both electrodes.

  Electrolytic treatment was carried out under the electrolytic conditions shown in Table 2. One electrode potential was always kept constant at 0 V, and the potential of the other electrode was periodically changed in a range of 0 V or more. The “potential (V)”, “period (Hz)”, and “waveform” shown in Table 2 are the application characteristics to the other electrode. The aluminum substrate surface facing the other electrode plate was referred to as the “front surface”, and the aluminum substrate surface facing the electrode plate whose potential was always 0 V was referred to as the “back surface”. However, in Comparative Example 1, an aluminum substrate as a sample is not disposed between a pair of electrodes, an aluminum substrate is used as an electrode whose potential changes periodically in a range of 0 V or higher, and the graphite plate is always kept at 0 V. Was used as this counter electrode. And the surface which faced the counter electrode among this aluminum substrate was made into the "front surface", and the other side was made into the "back surface". Further, in Comparative Example 2, there is no distinction between “front side” and “back side”.

  The front and back surfaces of the electrolytically treated aluminum substrate were observed with a cross-sectional TEM to examine the thickness of the oxide film, the small pore diameter, and the presence or absence of a branched structure. The results are shown in Table 3. In Table 3, “None” with respect to the small hole diameters on the front and back surfaces means that no pore structure was formed.

  A masking film (film substrate: vinyl chloride resin, adhesive: acrylic resin) is first applied to the back surface of the aluminum substrate subjected to the electrolytic treatment, and then an epoxy resin adhesive of 20 μm is applied to the front surface. After coating to a thickness and laminating an electrolytic copper foil having a thickness of 35 μm thereon, a printed wiring board sample was prepared by performing thermocompression bonding at 165 ° C. for 90 minutes with a hot press.

The following evaluation was performed on the samples thus prepared.
(Heat resistance adhesion test)
The sample was cut into a size of 55 mm × 25 mm and subjected to moisture absorption treatment in an autoclave at 121 ° C. for 16 hours. Subsequently, it floated on a 260 degreeC molten solder bath for 30 second, and the heat resistant adhesiveness of the aluminum substrate with respect to resin was evaluated by the area ratio from which copper foil peeled. Judgment criteria are as follows.
A: Peeling area ratio 0%
○: Peeling area ratio exceeding 0% and 10% or less △: Peeling area ratio exceeding 10% and 25% or less ×: Peeling area ratio exceeding 25% and 50% or less XX: Peeling area ratio exceeding 50%

(Masking film removability test)
The masking film still attached to the back surface of the sample was peeled off by hand, and the ratio of the area occupied by the adhesive remaining on the aluminum substrate to the adhesive coating area of the aluminum substrate was measured. Judgment criteria are as follows.
○: Occupied area ratio of remaining adhesive is 5% or less ×: Occupied area ratio of remaining adhesive exceeds 5%

Comprehensive evaluation of heat-resistant adhesion and masking film removability is as follows.
◎: Heat-resistant adhesion is ◎, masking film removability is ○
○: heat-resistant adhesion is ○, masking film removability is ○
Δ: heat resistant adhesion is Δ, masking film removability is ○
X: heat-resistant adhesion is x or xx, or masking film removability is x
◎, ○, and Δ were accepted, and x was rejected. The results are shown in Table 4.

  As is apparent from Table 4, Examples 1 to 19 of the invention satisfy the requirements of the invention, so that the heat-resistant adhesion on the front surface and the removability of the masking film on the back surface are good, and the overall evaluation is acceptable. On the other hand, since Comparative Examples 1 to 13 did not satisfy the requirements of the present invention, the heat-resistant adhesion on the front surface or the masking film removability on the back surface was poor, and the overall evaluation was unacceptable.

Specifically, in Comparative Example 1, since an aluminum substrate was connected and directly acted as an electrode, an adhesive oxide film was formed on both surfaces of the aluminum substrate. As a result, the masking film removability on the back surface was inferior, and the overall evaluation was unacceptable.
In Comparative Example 2, since the aluminum substrate was disposed in parallel with the direction of current, no charge was supplied to the substrate surface, and no pore structure was formed on the front surface. As a result, the heat-resistant adhesion on the front side was inferior and the overall evaluation was unacceptable.
In Comparative Example 3, although not connected to the aluminum substrate, an adhesive oxide film was formed on both surfaces of the aluminum substrate because a sine wave that changed from positive to negative was applied to the other electrode plate potential. As a result, the masking film removability on the back surface was inferior, and the overall evaluation was unacceptable.
In Comparative Example 4, since the pH of the electrolytic solution was too high, the oxide film thickness was too thin due to excessive etching during electrolysis, and the pore structure branched to the front surface was not formed. As a result, the heat-resistant adhesion on the front side was inferior and the overall evaluation was unacceptable.
In Comparative Example 5, since the pH of the electrolyte was too low, etching during electrolysis was insufficient and the oxide film became indefinite, and no pore structure was formed on the front surface. As a result, the heat-resistant adhesion on the front side was inferior and the overall evaluation was unacceptable.
In Comparative Example 6, since the temperature of the electrolytic solution was too low, etching during electrolysis was insufficient and the oxide film became indefinite, and no pore structure was formed on the front surface. As a result, the heat-resistant adhesion on the front side was inferior and the overall evaluation was unacceptable.
In Comparative Example 7, since the temperature of the electrolytic solution was too high, the oxide film thickness was too thin due to excessive etching during electrolysis, and the pore structure branched to the front surface was not formed. As a result, the heat-resistant adhesion on the front side was inferior and the overall evaluation was unacceptable.
In Comparative Example 8, since the potential between the electrodes did not change periodically, no pore structure was formed on the front surface. As a result, the heat-resistant adhesion on the front side was inferior and the overall evaluation was unacceptable.
In Comparative Example 9, since the current frequency was too low, the pore structure branched to the front surface was not formed. As a result, the heat-resistant adhesion on the front side was inferior and the overall evaluation was unacceptable.
In Comparative Example 10, since the frequency of the current was too high, the small hole diameter of the pore structure with the branched front surface was too large. As a result, the heat-resistant adhesion on the front side was inferior and the overall evaluation was unacceptable.
In Comparative Example 11, since the maximum current density was too low and the electrolysis time was too long, the oxide film formed on the front surface was indefinite, and no pore structure was obtained on the front surface. As a result, the heat-resistant adhesion on the front side was inferior and the overall evaluation was unacceptable.
In Comparative Example 12, since the current density was too high and the electrolysis time was too short, the pore structure branched to the front surface was not formed. As a result, the heat-resistant adhesion on the front side was inferior and the overall evaluation was unacceptable.
In Comparative Example 13, as in Comparative Example 1, since the wire was connected to the aluminum substrate and directly acted as an electrode, an adhesive oxide film was formed on both surfaces of the aluminum substrate. However, since the electrolysis time is too long, the thickness of the oxide film on both sides exceeds 500 nm. As a result, although the masking film removability on the back surface was excellent, the heat-resistant adhesion on the front surface was inferior and the overall evaluation was unacceptable.

  As described above, since an aluminum substrate made according to the claims of the present invention has an adhesive oxide film having a pore structure only on one side, the printed circuit board in which copper foil is bonded only to one side of the aluminum substrate is used. It can be used suitably.

DESCRIPTION OF SYMBOLS 1 ... Oxide film 2 ......... Aluminum substrate 3 ... Barrier layer 4 ... Pore structure 41 ... Small hole 5 ... Branch point 6 ... Aluminum substrate 61 ... Aluminum substrate surface 7 ... Electrode plate 71 ... Electrode plate surface 8 ... Power supply 9 ... Electrolyte 10 ... Electrode plate 101 ... Electrode plate surface 11 ... Ground

Claims (5)

  An aluminum substrate provided with an oxide film on both sides, the oxide film on one side being an adhesive oxide film having an overall thickness of 10 to 500 nm, comprising an aluminum substrate side barrier layer and a surface side pore structure The aluminum substrate is characterized in that the pore structure has a small hole with a diameter of 5 to 30 nm branched into the inside, and the oxide film on the other surface is a peelable oxide film.   The peelable oxide film (1) has a thickness of less than 10 nm or more than 500 nm; (2) has no pore structure; (3) has a branched structure even if it has a pore structure. Or (4) having a pore structure and having a branched structure, the diameter of the small hole is less than 5 nm or more than 30 nm. Aluminum substrate. An aluminum substrate that is not connected to both electrode plates is disposed between a pair of opposing electrode plates so that the substrate surface is parallel to both electrode plate surfaces, and electrolysis of an alkaline aqueous solution at a pH of 9 to 13 and a temperature of 35 to 85 ° C. In liquid, with respect to the potential of one electrode plate, the potential of the other electrode plate is increased and changed at a cycle of 20 to 100 Hz, and electrolysis is performed at a maximum current density of 4 to 50 A / dm ² for 5 to 60 seconds. A method of manufacturing an aluminum substrate to be processed.   The periodic change of the potential is at least one selected from the group consisting of a sine wave, a rectangular wave, a trapezoidal wave, and a triangular wave, and the time showing the minimum current density is 80% or less in one period. The manufacturing method of the aluminum substrate of description. The method for producing an aluminum substrate according to claim 4, wherein a difference between the highest current density and the lowest current density is 2 A / dm ² or more.

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