Metal-filled microstructure and method for manufacturing a metal-filled microstructure

Abstract

The present invention addresses the problem of providing a metal-filled microstructure and a method for manufacturing a metal-filled microstructure in which it is possible to reduce cost. This metal-filled microstructure has an insulating substrate, a plurality of penetrating paths penetrating in the thickness direction of the insulating substrate, and a plurality of conduction paths penetrating in the thickness direction of the insulating substrate. The insulating substrate is a valve-metal anodic oxide film. The plurality of conduction paths are configured from an electroconductive substance filling the interior of some of the plurality of penetrating paths. The number of conduction paths is less than 70% of the number of penetrating paths across all view fields for 20 discretionary view fields when 12 μm2 is deemed to be one view field.

Description

[Technical Field]

[0001] This invention relates to a metal-filled microstructure and a method for manufacturing a metal-filled microstructure. [Background technology]

[0002] Metal-filled microstructures, in which conductive materials such as metals are filled into multiple through-holes in an insulating substrate, are one of the fields that have attracted attention in nanotechnology in recent years, and are expected to have applications such as anisotropic conductive materials. Anisotropic conductive members are widely used as electrical connection members for electronic components such as semiconductor elements, and as test connectors for functional testing, because they can be inserted between electronic components such as semiconductor elements and circuit boards and an electrical connection between the electronic components and the circuit board can be obtained simply by applying pressure. In particular, electronic components such as semiconductor devices are undergoing significant downsizing. Conventional methods such as wire bonding, which directly connects wiring boards, flip-chip bonding, and thermocompression bonding cannot adequately guarantee the stability of electrical connections between electronic components. Therefore, anisotropic conductive materials are attracting attention as electronic connection materials.

[0003] Examples of metal-filled microstructures that can be used as such anisotropic conductive members include, for example, Patent Document 1, "1 × 10 6 ~1 × 10 10 / mm 2 A microstructure is described as being made of an insulating substrate having micropore through-holes with a pore diameter of 10 to 500 nm at a density, wherein the inside of the micropore through-holes is filled with metal to a filling rate of 80% or more ([Claim 1]). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2009-283431 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The inventors of the present invention investigated the metal-filled microstructure described in Patent Document 1 and found that it has a high metal filling rate and there is room for cost reduction.

[0006] Therefore, the object of the present invention is to provide a metal-filled microstructure and a method for manufacturing a metal-filled microstructure that can reduce costs. [Means for solving the problem]

[0007] As a result of diligent research to achieve the above objectives, the inventors of the present invention discovered that costs can be reduced by providing conductive passages filled with a conductive material inside a specific proportion of the multiple through-passages that penetrate the thickness direction of an insulating substrate, and thus completed the present invention. In other words, we found that the above problem can be solved by the following configuration.

[0008] [1] Having an insulating substrate, a plurality of through-passages penetrating the insulating substrate in the thickness direction, and a plurality of guide passages penetrating the insulating substrate in the thickness direction, The insulating substrate is an anodized film of valve metal. Multiple conduits are composed of conductive material filled inside some of the multiple through passages. The number of guide channels is 12 μm. 2 A metal-filled microstructure in which, across any 20 fields of view (with each field of view considered as one), the number of through-paths is less than 70%. [2] The metal-filled microstructure according to [1], wherein the surface of the insulating substrate is covered with a metal different from the valve metal. [3] The metal-filled microstructure according to [1] or [2], wherein the valve metal is aluminum. [4] A metal-filled microstructure according to any one of [1] to [3], wherein the conductive material is copper. [5] A method for manufacturing a metal-filled microstructure described in [1], comprising: An anodic oxidation treatment step of performing anodic oxidation treatment on one surface of the valve metal substrate to form an anodic oxidation film having micropores present in the thickness direction and a barrier layer present at the bottom of the micropores on one surface of the valve metal substrate; After the anodic oxidation treatment step, a metal filling step of performing electrolytic plating to fill the inside of the micropores with metal; The anodic oxidation treatment step is a step of performing anodic oxidation treatment multiple times; A method for manufacturing a metal-filled microstructure, wherein the voltage in any one of the anodic oxidation treatments performed after the second time is 2 times or more the maximum value of the voltage in the anodic oxidation treatment performed before the anodic oxidation treatment. [6] The method for manufacturing a metal-filled microstructure according to [5], wherein the multiple anodic oxidation treatments in the anodic oxidation treatment step are two anodic oxidation treatments.

Advantages of the Invention

[0009] According to the present invention, it is possible to provide a metal-filled microstructure and a method for manufacturing a metal-filled microstructure that can reduce costs.

Brief Description of the Drawings

[0010] [Figure 1] FIG. 1 is a schematic cross-sectional view showing one step of an example of the method for manufacturing a metal-filled microstructure of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view showing one step of an example of the method for manufacturing a metal-filled microstructure of the present invention. [Figure 3] FIG. 3 is a schematic cross-sectional view showing one step of an example of the method for manufacturing a metal-filled microstructure of the present invention. [Figure 4] FIG. 4 is a schematic cross-sectional view showing one step of an example of the method for manufacturing a metal-filled microstructure of the present invention. [Figure 5] FIG. 5 is a schematic cross-sectional view showing one step of an example of the method for manufacturing a metal-filled microstructure of the present invention. [Figure 6]FIG. 6 is a schematic cross-sectional view showing one step of an example of a method for manufacturing a metal-filled fine structure of the present invention.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In this specification, a numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value.

[0012] [Metal-filled fine structure] The metal-filled fine structure of the present invention has an insulating substrate, a plurality of through-holes penetrating in the thickness direction of the insulating substrate, and a plurality of conduction paths penetrating in the thickness direction of the insulating substrate. Also, in the metal-filled fine structure of the present invention, the insulating substrate is an anodic oxide film of valve metal. Furthermore, in the metal-filled fine structure of the present invention, the plurality of conduction paths are composed of a conductive substance filled inside a part of the plurality of through-holes, and the number of conduction paths is less than 70% of the number of through-holes in any 20 fields of view when taking 12 μm as one field of view. 2 as the total number of any 20 fields of view when taking 12 μm as one field of view.

[0013] FIGS. 1 to 6 are schematic cross-sectional views showing an example of a method for manufacturing a metal-filled fine structure of the present invention in the order of steps. Note that FIG. 6 is also a schematic cross-sectional view showing an example of the metal-filled fine structure of the present invention.

[0014] Here, the metal-filled fine structure 20 shown in FIG. 6 has an anodic oxide film 14, a plurality of conduction paths 12a penetrating in the thickness direction Dt of the anodic oxide film 14, and a plurality of conduction paths 16 formed by filling a conductive substance inside a part of the plurality of through-holes 12a.

[0015] [Insulating substrate] As described above, the insulating substrate of the metal-filled microstructure of the present invention is an anodic oxide film of valve metal. Here, specific examples of valve metals include aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth, and antimony. Of these, aluminum is preferred because it has good dimensional stability and is relatively inexpensive. Therefore, it is preferable to use an aluminum substrate to form an anodic oxide film, which is an insulating substrate, and to manufacture a metal-filled microstructure.

[0016] Aluminum substrates are not particularly limited, and specific examples include: pure aluminum plates; alloy plates mainly composed of aluminum and containing trace amounts of other elements; substrates in which high-purity aluminum is deposited onto low-purity aluminum (e.g., recycled material); substrates in which high-purity aluminum is coated onto the surface of silicon wafers, quartz, glass, etc., by methods such as deposition or sputtering; and resin substrates laminated with aluminum.

[0017] The aluminum substrate, specifically the surface that will undergo the anodizing treatment described later, preferably has an aluminum purity of 99.5% by mass or higher, more preferably 99.9% by mass or higher, and even more preferably 99.99% by mass or higher. When the aluminum purity is within the above range, the regularity of the arrangement of the through-pathways is sufficient.

[0018] Furthermore, it is preferable that the surface of the aluminum substrate that will undergo the anodizing treatment described later be subjected to heat treatment, degreasing treatment, and mirror finishing treatment in advance. Here, the heat treatment, degreasing treatment, and mirror finishing treatment can be performed in the same manner as those described in paragraphs

[0044] to

[0054] of Japanese Patent Application Publication No. 2008-270158.

[0019] In the present invention, for reasons of good handling properties, the thickness of the insulating base material is preferably 1 to 1000 μm, more preferably 5 to 500 μm, and even more preferably 10 to 300 μm.

[0020] <Through-hole> The through-holes of the metal-filled fine structure of the present invention are preferably composed of micropores provided penetrating in the thickness direction of the anodic oxide film of the valve metal. Also, the density of the above through-holes is preferably 2 million or more per mm 2 and more preferably 10 million or more per mm 2 even more preferably 50 million or more per mm 2 and particularly preferably 100 million or more per mm 2 is particularly preferred. Also, the average opening diameter of the above through-holes is preferably 5 to 500 nm, more preferably 20 to 400 nm, even more preferably 40 to 200 nm, and particularly preferably 50 to 100 nm.

[0021] <Conductive path> The conductive paths of the metal-filled fine structure of the present invention are composed of a conductive substance and are preferably composed of a metal filled in micropores (through-holes) provided penetrating in the thickness direction of the anodic oxide film of the valve metal. The above metal preferably has a material with an electrical resistivity of 10 3 Ω·cm or less, and specific examples thereof preferably include gold (Au), silver (Ag), copper (Cu), aluminum (Al), magnesium (Mg), nickel (Ni), zinc (Zn), etc. Among them, from the viewpoint of electrical conductivity, Cu, Au, Al, and Ni are preferable, Cu and Au are more preferable, and Cu is even more preferable.

[0022] In the present invention, as described above, the number of conductive paths is 12 μm 2In any 20 fields of view, with each field of view considered as one field of view, the number of through-paths is less than 70%, preferably between 20% and 70%, and more preferably between 30% and 70%. Here, the size of one field of view is 12 μm. 2 This is a region that is 4 μm wide and 3 μm long. Furthermore, the 20 fields of view are 12 μm fields arbitrarily selected from among 20 consecutive image regions taken at magnifications ranging from 40,000 to 70,000 times using a Field Emission Scanning Electron Microscope (FE-SEM) on the cross-section of the metal-filled microstructure. 2 This refers to the total of 20 fields of view, each consisting of a region (1 field of view) measuring (4 μm horizontally and 3 μm vertically).

[0023] Furthermore, in the present invention, as shown in Figures 5 and 6, the guide passage is preferably columnar, and its diameter is preferably 5 to 500 nm, more preferably 20 to 400 nm, even more preferably 40 to 200 nm, and particularly preferably 50 to 100 nm.

[0024] In the present invention, for the sake of good handling, it is preferable that the surface of the insulating substrate (the part indicated by reference numeral 14a in Figures 5 and 6) is covered with a metal different from the valve metal, and it is more preferable that both the surface and back surface of the insulating substrate (the part indicated by reference numeral 14b in Figures 5 and 6) are covered with a metal different from the valve metal. Here, examples of metals different from the valve metal include, for example, gold (Au), silver (Ag), copper (Cu), aluminum (Al), magnesium (Mg), nickel (Ni), zinc (Zn), and the like.

[0025] Furthermore, the thickness of the coating (coating layer) made of a metal different from the valve metal is preferably 2 to 50 μm, and more preferably 5 to 20 μm.

[0026] [Method for manufacturing metal-filled microstructures] The present invention provides a method for manufacturing a metal-filled microstructure (hereinafter referred to as "the manufacturing method of the present invention") which comprises an anodizing step of applying an anodic oxidation treatment to one surface of a valve metal substrate to form an anodic oxide film on one surface of the valve metal substrate having micropores present in the thickness direction and a barrier layer present at the bottom of the micropores, and a metal filling step of applying an electroplating treatment after the anodizing step to fill the inside of the micropores with metal. Herein, the manufacturing method of the present invention is a process in which the anodic oxidation treatment step is performed multiple times, and the voltage in any of the anodic oxidation treatments performed from the second time onward (hereinafter also abbreviated as "specific anodic oxidation treatment") is twice or more the maximum voltage of the anodic oxidation treatment performed before the specific anodic oxidation treatment. Furthermore, it is preferable that the manufacturing method of the present invention includes a barrier layer removal step after the anodic oxidation step to remove the barrier layer. Furthermore, the manufacturing method of the present invention may include a substrate removal step after the metal filling step, in which the valve metal substrate is removed.

[0027] Next, an overview of each step in the manufacturing method of the present invention will be explained using Figures 1 to 6, and then each processing step will be described in detail.

[0028] As shown in Figures 1 and 2, in the anodizing process, an anodizing treatment is applied to one side surface 10a of the valve metal substrate 10, forming an anodic oxide film 14 on one side surface 10a of the valve metal substrate 10, which has micropores 12 in the thickness direction Dt and a barrier layer 13 at the bottom of the micropores 12. Next, as shown in Figure 3, an additional anodic oxidation treatment (specific anodic oxidation treatment) is performed to grow micropores in the thickness direction Dt at the bottom of some of the micropores 12, and then a barrier layer 13a is formed. Next, as shown in Figure 4, in the barrier layer removal process, the barrier layer 13 is removed, reducing the thickness of the barrier layer 13a, and the first metal 15 is formed at the bottom of the micropore 12 from which the barrier layer 13 was removed. Next, as shown in Figure 5, in the metal filling process, the second metal is filled into the micropore in which the first metal 15 is formed at the bottom to form a guide passage 16. Next, as shown in Figure 6, in the substrate removal process, the valve metal substrate 10 and the barrier layer 13a are removed to obtain the metal-filled microstructure 20.

[0029] [Valve metal substrate] The valve metal substrate used in the manufacturing method of the present invention can be a valve metal substrate as described above in the section on insulating substrates, and among these, an aluminum substrate is preferred.

[0030] [Anodizing process] The above-described anodizing process involves applying an anodizing treatment to one side surface of the valve metal substrate to form an anodic oxide film on one side surface of the valve metal substrate, the film having micropores present in the thickness direction and a barrier layer present at the bottom of the micropores. Furthermore, the above-described anodizing process is a process in which multiple anodizing treatments are performed, and the voltage applied in any of the anodizing treatments performed from the second time onward (specific anodizing treatment) is at least twice the maximum voltage applied in the anodizing treatment performed before the specific anodizing treatment.

[0031] The multiple anodic oxidation processes performed in the above-described anodic oxidation step can be carried out using conventionally known methods as long as they satisfy the voltage relationship described above. However, from the viewpoint of increasing the regularity of the micropore arrangement and ensuring the anisotropic conductivity of the metal-filled microstructure, it is preferable to use self-ordering methods or constant-voltage treatment. Here, the self-ordering method and constant voltage treatment for anodic oxidation can be performed in the same manner as the treatments described in paragraphs

[0056] to

[0108] and [Figure 3] of Japanese Patent Application Publication No. 2008-270158.

[0032] In the manufacturing method of the present invention, it is preferable that the multiple anodic oxidation treatments in the above anodic oxidation treatment step consist of two anodic oxidation treatments, namely a first anodic oxidation treatment and a second anodic oxidation treatment (specific anodic oxidation treatment).

[0033] The first and second anodizing treatments can be carried out, for example, by applying an electric current to an aluminum substrate as the anode in a solution with an acid concentration of 1 to 10% by mass. The solutions used in the first and second anodizing treatments are preferably acidic solutions, with sulfuric acid, phosphoric acid, chromic acid, oxalic acid, sulfamic acid, benzenesulfonic acid, amidosulfonic acid, glycolic acid, tartaric acid, malic acid, citric acid, and the like being more preferred, and among these, sulfuric acid, phosphoric acid, and oxalic acid being particularly preferred. These acids can be used individually or in combination of two or more.

[0034] The conditions for the first and second anodizing processes vary depending on the electrolyte used and cannot be determined definitively, but generally, the electrolyte concentration is 0.1-20% by mass, the liquid temperature is -10-30°C, and the current density is 0.01-20 A / dm². 2 Preferably, the voltage is 3 to 300V, the electrolysis time is 0.5 to 30 hours, the electrolyte concentration is 0.5 to 15% by mass, the liquid temperature is -5 to 25°C, and the current density is 0.05 to 15 A / dm². 2 Preferably, the voltage is 5-250V, the electrolysis time is 1-25 hours, the electrolyte concentration is 1-10% by mass, the liquid temperature is 0-20℃, and the current density is 0.1-10A / dm 2 Furthermore, a voltage of 10-200V and an electrolysis time of 2-20 hours are preferred. As mentioned above, the voltage in the second anodizing treatment is to be at least twice the voltage in the first anodizing treatment.

[0035] The processing time for the first anodizing treatment and the second anodizing treatment is preferably 0.5 minutes to 16 hours, more preferably 1 minute to 12 hours, and even more preferably 2 minutes to 8 hours.

[0036] In addition to performing the first and second anodizing treatments under a constant voltage, methods in which the voltage is intermittently or continuously varied can also be used. In this case, it is preferable to gradually decrease the voltage. This makes it possible to lower the resistance of the anodized film and create fine micropores in the anodized film, which is preferable in that it improves uniformity, especially when sealing the pores by electrodeposition.

[0037] [Barrier layer removal process] The above barrier layer removal process is an optional process performed after the above anodic oxidation process to remove at least a portion of the barrier layer of the anodic oxide film. The method for removing the barrier layer is not particularly limited and includes, for example, a method of electrochemically dissolving the barrier layer at a potential lower than the potential in the final anodic oxidation treatment applied in the above anodic oxidation process (hereinafter also referred to as "electrolytic removal treatment"); a method of removing the barrier layer by etching (hereinafter also referred to as "etching removal treatment"); and a combination of these methods (in particular, a method of removing the remaining barrier layer by etching after performing electrolytic removal treatment); etc.

[0038] <Electrolytic removal treatment> The above-mentioned electrolytic removal treatment is not particularly limited as long as it is performed at an electrolytic potential lower than the potential (electrolytic potential) in the final anodic oxidation treatment performed in the above-mentioned anodic oxidation treatment process. In the present invention, the electrolytic dissolution treatment can be performed by lowering the electrolytic potential at the end of the final anodic oxidation treatment in the anodic oxidation treatment step, for example, thereby enabling the anodic oxidation treatment step and the barrier layer removal step to be carried out continuously.

[0039] The above-mentioned electrolytic removal treatment can employ the same electrolyte and treatment conditions as the conventionally known anodic oxidation treatment described above, except for the electrolytic potential. In particular, as mentioned above, when the anodic oxidation process and the barrier layer removal process are performed consecutively, it is preferable to use the same electrolyte solution for both processes.

[0040] In the electrolytic removal process described above, it is preferable to continuously or gradually (in a stepwise manner) lower the electrolytic potential to a potential lower than the electrolytic potential in the final anodic oxidation process applied in the anodic oxidation step described above. Here, the step size when gradually lowering the electrolytic potential is preferably 10V or less, more preferably 5V or less, and even more preferably 2V or less, from the viewpoint of the barrier layer's withstand voltage. Furthermore, from the viewpoint of productivity and other factors, the voltage drop rate when continuously or stepwise lowering the electrolytic potential is preferably 1 V / sec or less, more preferably 0.5 V / sec or less, and even more preferably 0.2 V / sec or less.

[0041] <Etching removal process> The above etching removal treatment is not particularly limited, but may be a chemical etching treatment using an acidic aqueous solution or an alkaline aqueous solution, or it may be a dry etching treatment.

[0042] (Chemical etching treatment) Removing the barrier layer by chemical etching can selectively dissolve only the barrier layer, for example, by immersing the structure after the final anodic oxidation treatment in the above anodic oxidation process in an acidic or alkaline aqueous solution, filling the inside of the micropores with the acidic or alkaline aqueous solution, and then bringing the surface of the micropore opening side of the anodic oxide film into contact with a pH buffer solution.

[0043] When using an aqueous acid solution, it is preferable to use an aqueous solution of an inorganic acid such as sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid, or oxalic acid, or a mixture thereof. Furthermore, the concentration of the aqueous acid solution is preferably 1 to 10% by mass. The temperature of the aqueous acid solution is preferably 15 to 80°C, more preferably 20 to 60°C, and even more preferably 30 to 50°C. On the other hand, when using an alkaline aqueous solution, it is preferable to use an aqueous solution of at least one alkali selected from the group consisting of sodium hydroxide, potassium hydroxide, and lithium hydroxide. Furthermore, the concentration of the alkaline aqueous solution is preferably 0.1 to 5% by mass. The temperature of the alkaline aqueous solution is preferably 10 to 60°C, more preferably 15 to 45°C, and even more preferably 20 to 35°C. Specifically, for example, a 50 g / L phosphoric acid aqueous solution at 40°C, a 0.5 g / L sodium hydroxide aqueous solution at 30°C, or a 0.5 g / L potassium hydroxide aqueous solution at 30°C are preferably used. Furthermore, as the pH buffer, a buffer corresponding to the acidic aqueous solution or alkaline aqueous solution described above can be used as appropriate.

[0044] Furthermore, the immersion time in the acidic or alkaline aqueous solution is preferably 5 to 120 minutes, more preferably 8 to 120 minutes, even more preferably 8 to 90 minutes, and particularly preferably 10 to 90 minutes. Among these, 10 to 60 minutes is preferred, and 15 to 60 minutes is more preferred.

[0045] (Dry etching process) For dry etching, it is preferable to use a gas species such as a Cl2 / Ar mixed gas.

[0046] In the manufacturing method of the present invention, the barrier layer removal process is preferably a process of removing the barrier layer of the anodic oxide film using an alkaline aqueous solution containing a metal M1 that has a higher hydrogen overpotential than aluminum. By using an alkaline aqueous solution containing metal M1, which has a higher hydrogen overpotential than aluminum, a metallic layer made of metal M1 is formed at the bottom of the micropore from which the barrier layer has been removed. Here, hydrogen overvoltage refers to the voltage required for hydrogen to be generated. For example, the hydrogen overvoltage of aluminum (Al) is -1.66V (Journal of the Chemical Society of Japan, 1982, (8), pp. 1305-1313). Examples of metals M1 with a hydrogen overvoltage higher than that of aluminum, and their hydrogen overvoltage values, are shown below. <Metal M1 and hydrogen (1N H2SO4) overpotential> ·Platinum (Pt): 0.00V ·Gold (Au): 0.02V ·Silver (Ag): 0.08V Nickel (Ni): 0.21V ·Copper (Cu):0.23V ·Tin (Sn): 0.53V Zinc (Zn): 0.70V

[0047] The method for removing the barrier layer using such an alkaline aqueous solution containing metal M1 is not particularly limited, and for example, a method similar to the chemical etching treatment described above can be used.

[0048] [Metal filling process] The above metal filling process is a process in which, after the above anodic oxidation process, an electroplating process is performed to fill the inside of the micropore with metal.

[0049] <Metal> The above-mentioned metals are similar to those used for the conductive passages described above.

[0050] <Filling method> Methods for filling the inside of the micropore with the above-mentioned metal include, for example, methods similar to those described in paragraphs

[0123] to

[0126] and [Figure 4] of Japanese Patent Publication No. 2008-270158.

[0051] In the manufacturing method of the present invention, it is preferable to use an electroplating method as a method for filling the inside of the micropore with the above metal, and for example, an electroplating method or an electroless plating method can be used. In conventional electroplating methods used for coloring and other applications, it is difficult to selectively deposit (grow) metal in pores with a high aspect ratio. This is thought to be because the deposited metal is consumed within the pores, and the plating does not grow even if electrolysis is performed for a certain period of time or longer. Therefore, in the manufacturing method of the present invention, when filling with metal by electroplating, it is necessary to provide a pause time during pulse electrolysis or constant potential electrolysis. The pause time must be 10 seconds or more, and preferably 30 to 60 seconds. Furthermore, it is desirable to apply ultrasound to promote agitation of the electrolyte. Furthermore, the electrolysis voltage is usually 20V or less, preferably 10V or less, but it is preferable to measure the deposition potential of the target metal in the electrolyte used in advance and perform constant potential electrolysis within that potential + 1V. When performing constant potential electrolysis, it is desirable to use a device that can also perform cyclic voltammetry, and potentiostat devices from companies such as Solartron, BAS, Hokuto Denko, and IVIUM can be used.

[0052] Conventional known plating solutions can be used as the plating solution. Specifically, when precipitating copper, an aqueous solution of copper sulfate is generally used, with a preferred concentration of 1 to 300 g / L, and more preferably 100 to 200 g / L. Furthermore, adding hydrochloric acid to the electrolyte can accelerate precipitation. In this case, a hydrochloric acid concentration of 10 to 20 g / L is preferred. Furthermore, when depositing gold, it is preferable to use a sulfuric acid solution of tetrachlorogold and perform plating by alternating current electrolysis.

[0053] Furthermore, since electroless plating requires a long time to completely fill pores consisting of high-aspect-ratio micropores with metal, it is preferable to fill the metal using electrolytic plating in the manufacturing method of the present invention.

[0054] In the manufacturing method of the present invention, it is preferable to use a treatment method that combines AC electroplating and DC electroplating in this order as the electroplating treatment method. In this AC electroplating method, for example, a voltage is applied after being modulated sinusoidally at a predetermined frequency. Note that the waveform used for voltage modulation is not limited to a sine wave; for example, a square wave, triangular wave, sawtooth wave, or inverted sawtooth wave can also be used. Furthermore, the DC electroplating method can appropriately utilize the processing methods described above in the electroplating method.

[0055] [Substrate removal process] The above substrate removal step is an optional step to remove the valve metal substrate after the above metal filling step. The method for removing the valve metal substrate is not particularly limited, but preferred methods include removal by dissolution.

[0056] <Dissolution of valve metal substrate> For dissolving the valve metal substrate, it is preferable to use a processing solution that does not easily dissolve the anodic oxide film but easily dissolves the valve metal. The dissolution rate of such a processing solution in the valve metal is preferably 1 μm / min or more, more preferably 3 μm / min or more, and even more preferably 5 μm / min or more. Similarly, the dissolution rate in the anodic oxide film is preferably 0.1 nm / min or less, more preferably 0.05 nm / min or less, and even more preferably 0.01 nm / min or less. Specifically, the treatment solution preferably contains at least one metal compound having a lower ionization tendency than the valve metal, and has a pH of 4 or less or 8 or more, more preferably 3 or less or 9 or more, and even more preferably 2 or less or 10 or more.

[0057] Such treatment solutions are preferably based on an acid or alkaline aqueous solution and contain compounds of manganese, zinc, chromium, iron, cadmium, cobalt, nickel, tin, lead, antimony, bismuth, copper, mercury, silver, palladium, platinum, or gold (e.g., chloroplatinic acid), their fluorides, or their chlorides. In particular, an acidic aqueous solution base is preferred, and blending with chlorides is also preferred. In particular, treatment solutions obtained by blending hydrochloric acid aqueous solution with mercury chloride (hydrochloric acid / mercury chloride) and treatment solutions obtained by blending hydrochloric acid aqueous solution with copper chloride (hydrochloric acid / copper chloride) are preferred from the viewpoint of treatment latitude. The composition of such a treatment solution is not particularly limited; for example, a bromine / methanol mixture, a bromine / ethanol mixture, aqua regia, etc., can be used.

[0058] Furthermore, the acid or alkali concentration of such a treatment solution is preferably 0.01 to 10 mol / L, and more preferably 0.05 to 5 mol / L. Furthermore, the processing temperature using such a processing solution is preferably -10°C to 80°C, and more preferably 0°C to 60°C.

[0059] Furthermore, the dissolution of the valve metal substrate is carried out by bringing the valve metal substrate, after the metal filling process, into contact with the processing liquid described above. The method of contact is not particularly limited, and examples include immersion and spraying. Among these, the immersion method is preferred. The contact time at this time is preferably 10 seconds to 5 hours, and more preferably 1 minute to 3 hours.

[0060] [Other processing steps] <Pore diameter enlargement treatment> The manufacturing method of the present invention may include a step of performing a pore size enlargement treatment after the anodic oxidation treatment step and before the metal filling treatment step by DC electrolysis, from the viewpoint of improving the soundness of the filling in DC electrolytic plating. Here, the pore size enlargement process is a process (pore size enlargement process) that enlarges the diameter of micropores (pore diameter) present in the anodic oxide film formed by the anodic oxidation process described above. Furthermore, the pore size enlargement treatment can be carried out by bringing the valve metal substrate with the anodic oxide film, after the anodizing treatment process described above, into contact with an acidic aqueous solution or an alkaline aqueous solution. The method of contact is not particularly limited, and examples include immersion and spraying methods.

[0061] <Formation of a metal coating layer> As described above, in the metal-filled microstructure of the present invention, it is preferable that the surface of the insulating substrate is coated with a metal different from the valve metal. Here, the method for forming a coating (coating layer) with a metal different from the valve metal is not particularly limited, but when providing a metal coating layer on one side surface of an insulating substrate, for example, it can be formed by continuing the electroplating treatment method in the metal filling process described above even after the metal has been filled into the through-passage. Furthermore, when a metal coating layer is to be provided on the front and back surfaces of the insulating substrate, it can be formed by first providing a metal coating layer on the surface of the insulating substrate using the method described above, then removing the valve metal substrate using the substrate removal process described above, and finally performing electroplating on the exposed insulating substrate and the surface of the conduit. [Examples]

[0062] The present invention will be described in more detail below based on the following examples. The materials, amounts used, proportions, processing content, processing procedures, etc., shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following examples.

[0063] [Example 1] <Fabrication of aluminum substrates> A molten metal was prepared using an aluminum alloy containing Si:0.06 mass%, Fe:0.30 mass%, Cu:0.005 mass%, Mn:0.001 mass%, Mg:0.001 mass%, Zn:0.001 mass%, and Ti:0.03 mass%, with the remainder being Al and unavoidable impurities. After molten metal treatment and filtration, an ingot with a thickness of 500 mm and a width of 1200 mm was produced by DC (Direct Chill) casting. Next, the surface was milled to an average thickness of 10 mm using a milling machine, then it was heated to 550°C for approximately 5 hours until the temperature dropped to 400°C, at which point it was rolled into a 2.7 mm thick sheet using a hot rolling mill. Furthermore, after heat treatment at 500°C using a continuous annealing machine, the material was cold-rolled to a thickness of 1.0 mm to obtain an aluminum substrate conforming to JIS 1050 material. After making this aluminum substrate 1030 mm wide, the following processes were performed on it.

[0064] <Electropolishing Treatment> The above aluminum substrate was subjected to electrolytic polishing using an electrolytic polishing solution with the following composition under the conditions of a voltage of 25V, a liquid temperature of 65°C, and a liquid flow rate of 3.0 m / min. A carbon electrode was used as the cathode, and a GP0110-30R power supply (manufactured by Takasago Seisakusho Co., Ltd.) was used. The electrolyte flow rate was measured using a vortex flow monitor FLM22-10PCW (manufactured by AS ONE Corporation). (Electrolytic polishing liquid composition) • 85% by mass phosphoric acid (reagent manufactured by Wako Pure Chemical Industries, Ltd.) 660 mL ·Pure water 160mL ·Sulfuric acid 150mL • Ethylene glycol 30mL

[0065] <Anodizing process> Next, the aluminum substrate after electropolishing was subjected to a first anodic oxidation treatment under the conditions shown in Table 1 below. Next, the voltage was gradually reduced to less than 1 / 5 of the voltage used in the first anodizing treatment, held at that voltage for 10 minutes, and then further reduced to 0V. The voltage reduction rate was set to 2V / min. Next, a second anodic oxidation treatment was performed under the conditions shown in Table 1 below to form an anodic oxide film with the total thickness shown in Table 1 below. For both the first and second anodizing treatments, a stainless steel electrode was used as the cathode, and a GP0110-30R power supply (manufactured by Takasago Seisakusho Co., Ltd.) was used. A NeoCool BD36 (manufactured by Yamato Scientific Co., Ltd.) was used as the cooling device, and a Pair Stirrer PS-100 (manufactured by EYELA Tokyo Rikakikai Co., Ltd.) was used as the stirring and heating device. Furthermore, the electrolyte flow rate was measured using a vortex flow monitor FLM22-10PCW (manufactured by AS ONE Corporation).

[0066] <Barrier layer removal process (processing conditions 1)> Next, the barrier layer was removed by immersing the sample in an alkaline aqueous solution containing Zn as metal M1, which has a higher hydrogen overpotential than aluminum, specifically a saturated sodium hydroxide aqueous solution (bath temperature 25°C) for 2 minutes.

[0067] <Metal filling process (processing conditions 1)> Next, an electroplating process was performed using an aluminum substrate as the cathode and platinum as the cathode. Specifically, metal-filled microstructures in which copper is packed inside micropores were fabricated by using a copper plating solution with the following composition and applying constant current electrolysis. Here, constant current electrolysis was performed using a plating apparatus manufactured by Yamamoto Plating Testing Equipment Co., Ltd., with a power supply (HZ-3000) manufactured by Hokuto Denko Co., Ltd. After confirming the deposition potential by performing cyclic voltammetry in the plating solution, the treatment was carried out under the conditions shown below. (Composition and conditions of copper plating solution) ·Copper sulfate 100g / L ·Sulfuric acid 50g / L Hydrochloric acid 15g / L • SPS (Bis(3-sulfopropyl) disulfide) 0.004 g / L ·Temperature 25℃ ·Current density 10A / dm 2

[0068] <Substrate removal process> Next, the aluminum substrate was dissolved and removed by immersion in a mixed solution of copper chloride and hydrochloric acid to fabricate a metal-filled microstructure.

[0069] [Example 2] Metal-filled microstructures were fabricated in the same manner as in Example 1, except that the conditions for the first and second anodizing treatments were changed to those shown in Table 1 below.

[0070] [Example 3] A metal-filled microstructure was fabricated in the same manner as in Example 1, except that the conditions for the first and second anodizing treatments were changed to those shown in Table 1 below, and the metal filling process was carried out under the conditions shown below. <Metal filling process (processing conditions 2)> (1) AC electroplating Next, a bath containing 0.1 mol / L aluminum sulfate aqueous solution with 0.1 mol of zinc sulfate was prepared and heated to 30°C. A carbon electrode was used as the counter electrode, and electrolysis was performed for 5 minutes using a 50 Hz sine wave (peak voltage 25 V). After the AC electrolysis was completed, the sample was thoroughly rinsed with water. (2) DC electrolytic plating After the AC electroplating described in (1) above, DC electroplating was performed under the same conditions as the metal filling treatment (treatment condition 1) in Example 1.

[0071] [Example 4] A metal-filled microstructure was fabricated in the same manner as in Example 3, except that the pore size enlargement process described below was performed between the AC electrolytic plating and DC electrolytic plating in the metal-filling process. <Pore diameter enlargement process> Next, the sample was immersed in a potassium hydroxide aqueous solution (0.01 mol / L, 25°C) for 20 minutes. After the treatment, it was thoroughly rinsed with water.

[0072] [Comparative Example 1] Except for changing the conditions for the first anodizing treatment to those shown in Table 1 below, and omitting the second anodizing treatment, a metal-filled microstructure was fabricated in the same manner as in Example 1.

[0073] Each metal-filled microstructure fabricated in Examples 1-4 and Comparative Example 1 was machined in the thickness direction using a focused ion beam (FIB), and surface images (magnification 50,000x) of its cross-section were taken using a FE-SEM. Using the captured images, 12 μm 2 The number of conduits in any 20 fields of view, with each field of view considered as one, was examined, and the ratio to the total number of through-passages was calculated. The results are shown in Table 1 below.

[0074] Furthermore, for each metal-filled microstructure fabricated in Examples 1-4 and Comparative Example 1, a coating layer made of a metal different from the valve metal was formed on the front and back surfaces of the insulating substrate as an evaluation sample. Here, the coating layer on the surface of the insulating substrate was formed by doubling the processing time in the metal filling step in each example and comparative example, and continuing the process even after the metal had been filled into the inside of the through-passage. Furthermore, the coating layer on the back surface of the insulating substrate was formed by removing the aluminum substrate in the substrate removal process, and then applying the electroplating treatment in the metal filling process described in each example and comparative example to the surface of the exposed conductive passages on the exposed insulating substrate, using the surface of the conductive passages as electrodes.

[0075] [evaluation] [Without coating layer] <Cost> Regarding cost, the average filling rate was used as an indicator, representing the ratio of the amount of metal required to fill all penetrations. The following evaluation criteria were used so that a lower filling rate would result in greater cost reduction. The results are shown in Table 1 below. 1: 80% or more 2: 70-80% 3: 60-70% 4:55~60% 5:50~55% 6:45~50% 7:40~45% 8:35~40% 9:30~35% <Handling> Regarding handling ease, the decrease in hydrophilicity due to contamination (change in contact angle) after storage in the atmosphere for one day was used as an indicator, and the following evaluation criteria were used. The results are shown in Table 1 below. A: Contact angle change is within 10 degrees (small impact of contamination) B: Contact angle change of 10 degrees or more (easily contaminated)

[0076] [With coating layer] <Cost> Cost was evaluated using the same criteria as above, but without the coating layer. The results are shown in Table 1 below. <Coverage> Regarding the coating quality, the condition of the coating layer was visually inspected using an optical microscope at 10x magnification and evaluated according to the following criteria. The results are shown in Table 1 below. A: When preparing the sample for evaluation, the entire surface was uniformly coated with twice the processing time. B: During the preparation of the evaluation sample, areas where the surface layer was not partially covered were observed even with twice the processing time.

[0077] [Table 1]

[0078] From the results shown in Table 1, the number of guide channels is 12 μm. 2 It was found that the cost increases if the number of through-paths exceeds 70% of the total number of through-paths in any 20 fields of view, with each field of view considered as one field of view (Comparative Example 1). In contrast, the number of guide channels is 12 μm. 2 It was found that costs can be reduced if the number of through-paths is less than 70% of the total number of through-paths in any 20 fields of view, with each field of view considered as one field of view (Examples 1-4). [Explanation of Symbols]

[0079] 10 Valve metal substrate 10a surface 12 micropore 12a Passageway 13, 13a Barrier layer 14. Anodized film 14a surface 14b Reverse side 15 The first metal 16 Conduit 20 Metal-filled microstructure Dt thickness direction

Claims

1. A method for manufacturing a metal-filled microstructure, The metal-filled microstructure comprises an insulating substrate, a plurality of through-paths penetrating the insulating substrate in the thickness direction, and a plurality of guide passages penetrating the insulating substrate in the thickness direction. The insulating substrate is an anodized film of valve metal. The plurality of passages are made of copper that is filled inside some of the passages of the plurality of through passages. The number of the aforementioned guide passages is 12 μm ２ In any 20 fields of view, where one field of view is defined as such, the number of through-paths is 20% or more but less than 70% in the entire field of view, and the metal-filled microstructure is such that An anodizing process involves applying an anodizing treatment to one side surface of a valve metal substrate to form an anodized film on the one side surface of the valve metal substrate having micropores present in the thickness direction and a barrier layer present at the bottom of the micropores. The process includes a metal filling step in which, after the anodic oxidation step, electroplating is performed to fill the inside of the micropore with metal, The aforementioned anodic oxidation treatment process is a process of performing multiple anodic oxidation treatments. A method for manufacturing a metal-filled microstructure, wherein the voltage applied in any subsequent anodic oxidation treatment is at least twice the maximum voltage applied in the anodic oxidation treatment preceding the aforementioned treatment.

2. The method for manufacturing a metal-filled microstructure according to claim 1, wherein the multiple anodic oxidation treatments in the anodic oxidation treatment step consist of two anodic oxidation treatments.

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