Surface-treated copper material, copper-clad laminate, method for manufacturing surface-treated copper material, and method for manufacturing copper-clad laminate

Abstract

To improve retention property of adhesion force between a surface of a surface-treated copper material and a resin part joined to the surface after exposed to a high-temperature environment for a long time.SOLUTION: A surface-treated copper material includes an oxidized surface including a cuprous oxide and a copper oxide. In the oxidized surface, the total of thickness (T1) of the cuprous oxide and thickness (T2) of the copper oxide is 1 nm or more and 40 nm or less which is determined by continuous electrochemical reduction analysis and a ratio (T2 / T1) of the thickness (T2) of the copper oxide to the thickness (T1) of the cuprous oxide is 1 or more and 9 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a surface-treated copper material, a copper-clad laminate, a method for producing a surface-treated copper material, and a method for producing a copper-clad laminate. [Background technology]

[0002] Copper-clad laminates, which are formed by laminating an insulating layer and a copper layer, are used, for example, as materials for manufacturing flexible printed wiring boards. Such copper-clad laminates are manufactured, for example, by laminating a copper foil and a resin sheet that constitutes the insulating layer.

[0003] Patent Documents 1 and 2 disclose techniques for increasing the peel strength between the copper layer and the resin layer serving as an insulating layer in a copper-clad laminate by roughening the surface of the copper foil used in the manufacture of the copper-clad laminate through an oxidation-reduction treatment. Patent Document 1 discloses a method for manufacturing a copper-clad laminate using a copper foil having a roughened surface in which the thickness of the copper oxide is 1 nm to 20 nm and the thickness of the cuprous oxide is 15 nm to 70 nm, as determined by continuous electrochemical reduction analysis. Patent Document 2 discloses a method for manufacturing a copper-clad laminate using a copper foil having a roughened surface in which the thickness of the cuprous oxide is 71 nm to 300 nm and the thickness of the copper oxide is 0 nm to 20 nm, as determined by continuous electrochemical reduction analysis. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6178035 [Patent Document 2] Japanese Patent Application Publication No. 2019-218602 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, with the increasing use of the Internet of Things (IoT), electronic devices such as sensors tend to be used in a variety of environments. For example, millimeter waves used in sensors are highly stable against light, weather, and the environment, and are therefore used in millimeter wave radars in automobiles and are also expected to be used in even harsher environments. As such, electronic devices in recent years are sometimes used in harsher environments, and this has led to a demand for improved environmental resistance for electronic devices.

[0006] For example, flexible printed wiring boards mounted on electronic devices used in harsh environments are required to maintain adhesion between the copper layer and the resin layer even after long-term exposure to high-temperature environments. The copper-clad laminates manufactured by the methods described in Patent Documents 1 and 2 have room for improvement in terms of maintaining adhesion after long-term exposure to high-temperature environments. [Means for solving the problem]

[0007] The surface-treated copper material that solves the above-mentioned problems is a surface-treated copper material having an oxidized surface containing cuprous oxide and copper oxide, wherein the oxidized surface has a total thickness (T1) of the cuprous oxide and a thickness (T2) of the copper oxide determined by continuous electrochemical reduction analysis of 1 nm or more and 40 nm or less, and a ratio (T2 / T1) of the thickness of the copper oxide (T2) to the thickness (T1) of the cuprous oxide is 1 or more and 9 or less.

[0008] In the surface-treated copper material, the thickness (T1) of the cuprous oxide on the oxidized surface is preferably 0.1 nm or more and 20 nm or less. In the surface-treated copper material, the thickness (T2) of the copper oxide on the oxidized surface is preferably 0.9 nm or more and 36 nm or less.

[0009] The copper clad laminate that solves the above problem comprises a copper layer made of the above surface-treated copper material, and an insulating resin layer laminated on the oxidized surface of the copper layer. In the copper-clad laminate, the resin constituting the insulating resin layer preferably contains a thermoplastic resin.

[0010] In the copper-clad laminate, the thermoplastic resin is preferably at least one selected from polyimide, liquid crystal polymer, polyether ether ketone, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and polytetrafluoroethylene.

[0011] A method for producing a surface-treated copper material that solves the above-mentioned problems includes a surface treatment step of forming an oxidized surface containing cuprous oxide and copper oxide on the surface of a copper material, and in the surface treatment step, the surface of the copper material is oxidized so that the sum of the thickness (T1) of the cuprous oxide and the thickness (T2) of the copper oxide, as determined by continuous electrochemical reduction analysis, is 1 nm or more and 40 nm or less, and the ratio (T2 / T1) of the thickness (T2) of the copper oxide to the thickness (T1) of the cuprous oxide is 1 or more and 9 or less.

[0012] A method for manufacturing a copper-clad laminate that solves the above problem is a method for manufacturing a copper-clad laminate that includes a copper layer and an insulating resin layer laminated on the surface of the copper layer, and includes a lamination step of laminating and bonding an insulating resin to the oxidized surface of the surface-treated copper material. [Effects of the Invention]

[0013] According to the present invention, the adhesion between the surface of a surface-treated copper material and a resin portion bonded to the surface is improved after exposure to a high-temperature environment for a long period of time. DETAILED DESCRIPTION OF THE INVENTION

[0014] An embodiment of the present invention will be described below. <Surface-treated copper material> The surface-treated copper material of this embodiment is a copper material having a specific oxidized surface.

[0015] The form of the surface-treated copper material is not particularly limited. Examples of the form of the surface-treated copper material include foil and plate. Examples of foil-shaped surface-treated copper materials include rolled copper foil and electrolytic copper foil. The thickness of the foil-shaped or plate-shaped surface-treated copper material can be appropriately set depending on the application of the surface-treated copper material. For example, when used in a flexible printed wiring board, the thickness of the surface-treated copper material is, for example, 2 μm to 105 μm, preferably 2 μm to 70 μm. When used in semiconductor manufacturing equipment, thermoelectric conversion components, etc., the thickness of the surface-treated copper material is, for example, 100 μm to 1000 μm, preferably 300 μm to 700 μm.

[0016] The oxidized surface of the surface-treated copper material may be on only one side of the surface-treated copper material, or on two or more sides of the surface-treated copper material. For example, when the surface-treated copper material is in the form of a foil or a plate, one side of the surface-treated copper material may be an oxidized surface, or both sides of the surface-treated copper material may be oxidized surfaces.

[0017] An oxidized surface is a surface where a first parameter and a second parameter based on the thickness of cuprous oxide (T1) and copper oxide (T2), respectively, fall within specific ranges, as determined by sequential electrochemical reduction analysis (SERA).

[0018] The first parameter is the sum of the thickness of the cuprous oxide (T1) and the thickness of the copper oxide (T2). The first parameter is 1 nm or more and 40 nm or less. The first parameter is preferably 1.2 nm or more, and more preferably 1.5 nm or more. The first parameter is preferably 35 nm or less, and more preferably 20 nm or less.

[0019] The second parameter is the ratio (T2 / T1) of the thickness of the copper oxide (T2) to the thickness of the cuprous oxide (T1). The second parameter is 1 or more and 9 or less. The second parameter is preferably 1.2 (55 / 45) or more, more preferably 1.5 (60 / 40) or more, and even more preferably 3 or more. The second parameter is preferably 8.1 (89 / 11) or less, more preferably 7.3 (88 / 12) or less, and more preferably 6 or less. Among these, it is particularly preferable that the second parameter is 3 or more and 6 or less.

[0020] The thickness (T1) of the cuprous oxide is, for example, 0.1 nm or more, preferably 0.2 nm or more, and more preferably 0.3 nm or more. The thickness (T1) of the cuprous oxide is, for example, 20 nm or less, preferably 15 nm or less, and more preferably 5 nm or less.

[0021] The thickness (T2) of the copper oxide is, for example, 0.9 nm or more, preferably 1.0 nm or more, and more preferably 1.2 nm or more. The thickness (T2) of the copper oxide is, for example, 36 nm or less, preferably 20 nm or less, and more preferably 15 nm or less.

[0022] The continuous electrochemical reduction analysis for determining the thickness of cuprous oxide (T1) and copper oxide (T2) can be performed using a commercially available measuring device such as the QC-100 manufactured by ECI Technology, Inc. An example of a method for determining the thickness of cuprous oxide (T1) and copper oxide (T2) based on the continuous electrochemical reduction analysis will be described below.

[0023] A circular area of ​​0.16 cm in diameter on the surface-treated copper material to be measured is isolated by a ring gasket, and an electrolyte is poured into it and saturated with nitrogen. The electrolyte is, for example, a boric acid buffer solution of pH 8.4 prepared with pure water to contain 6.18 g / L of boric acid and 9.55 g / L of sodium tetraborate decahydrate. A current density of 150 μA / cm is applied to the area. 2A voltage of -0.35 to -0.60 V (CuO) and -0.60 to -0.85 V (CuO) are applied, and the reduction reaction times (seconds) that appear at these voltages are measured. Based on the measured reduction reaction times, the thickness of CuO (T1) and the thickness of CuO (T2) are calculated using the following formula.

[0024] T1(nm)=0.001236×current density(μA / cm 2 ) x reduction time (seconds) T2(nm)=0.000639×current density(μA / cm 2 ) x reduction time (seconds) The oxidized surface of the surface-treated copper material may have a rust-preventive layer. The rust-preventive layer may be a layer typically applied to copper materials. The rust-preventive layer is preferably an organic rust-preventive layer, more preferably an organic rust-preventive layer containing at least one of a triazole-based rust inhibitor and a silane coupling-based rust inhibitor. Examples of triazole-based rust inhibitors and silane coupling-based rust inhibitors include compounds described in Patent Document 2.

[0025] <Method of manufacturing surface-treated copper materials> The method for producing a surface-treated copper material includes a surface treatment step of forming the above-mentioned oxidized surface on the surface of the copper material. Examples of the surface treatment performed in the surface treatment step include a heat treatment in which the surface of the copper material is heated in an oxidizing atmosphere, and an oxidation-reduction treatment in which an oxidation treatment and a reduction treatment are sequentially performed on the surface of the copper material. Note that, from the viewpoint of reducing the environmental load caused by waste liquids, it is preferable that the surface treatment step be a heat treatment that does not use various treatment liquids that require post-treatment.

[0026] The heat treatment is a process in which the surface of the copper material is heated in an oxidizing atmosphere using a heating device. As the heating device, for example, a known heating device such as a far-infrared heating furnace or a blower furnace can be used. The heating device is preferably equipped with a mechanism that can make the temperature inside the furnace uniform.

[0027] The heating temperature in the heat treatment is, for example, 150°C or higher and 200°C or lower. The heating time in the heat treatment is, for example, 120 seconds or more and 1200 seconds or less. Examples of the oxidizing atmosphere in the heat treatment include air, oxygen, ozone, and carbon dioxide.

[0028] When heat treatment is used as the surface treatment step, the first and second parameters can be adjusted by adjusting, for example, the heating temperature, heating time, and the composition of the oxidizing atmosphere.

[0029] The process of forming an oxidized surface by heat treatment can be thought of as follows: In the first stage, which is the initial stage of heat treatment, a reaction occurs in which cuprous oxide present on the surface of the copper material is oxidized to copper oxide. Then, as the material is heated further, a second stage occurs in which a reaction occurs in which the inner copper is oxidized to cuprous oxide, and a reaction occurs in which either or both of the inner copper and cuprous oxide are oxidized to copper oxide.

[0030] Therefore, the first parameter, which is the sum of the thickness of the cuprous oxide (T1) and the thickness of the copper oxide (T2), increases as the degree of progress of the second-stage reaction increases. Therefore, when the first parameter is increased, the degree of progress of the second-stage reaction can be increased, and when the first parameter is decreased, the degree of progress of the second-stage reaction can be decreased or the heat treatment can be terminated during the first stage.

[0031] Furthermore, in the second-stage reaction, cuprous oxide is oxidized to copper oxide, while copper oxide accumulates as it is. Therefore, the second parameter, which is the ratio (T2 / T1) of the thickness of copper oxide (T2) to the thickness of cuprous oxide (T1), increases as the total amount of copper oxide increases. Therefore, increasing the second parameter simply increases the progress of the second-stage reaction, and decreasing the second parameter simply decreases the progress of the second-stage reaction. Note that, when the heat treatment is terminated midway through the first stage, increasing the second parameter simply increases the progress of the first-stage reaction, and decreasing the second parameter simply decreases the progress of the first-stage reaction.

[0032] The degree of progress of the second stage reaction is increased by increasing the heating temperature, lengthening the heating time, and increasing the oxygen-richness of the oxidizing atmosphere. If the heat treatment is terminated during the first stage, the heating time is shortened. The degree of progress of the first stage is increased by further increasing the heating temperature and increasing the oxygen-richness of the oxidizing atmosphere under the condition of shortening the heating time. Utilizing this tendency, the heat treatment is performed so that the first parameter and the second parameter are each within the above-mentioned specific ranges.

[0033] In the oxidation-reduction treatment, first, an oxidation treatment is performed on a specific surface of a copper material, thereby obtaining an oxidation-treated copper material in which a copper compound containing copper oxide is formed on the specific surface. Next, a reduction treatment is performed on the specific surface of the oxidation-treated copper material, thereby converting a portion of the copper oxide contained in the copper compound on the specific surface to cuprous oxide, thereby obtaining a surface-treated copper material in which a copper compound containing cuprous oxide and copper oxide is formed on the specific surface. The oxidation treatment and reduction treatment are not particularly limited, and conventionally known methods, such as a wet method using an oxidation treatment solution and a reduction treatment solution disclosed in Patent Document 2, can be applied.

[0034] When an oxidation-reduction treatment is used as the surface treatment step, the above-mentioned first and second parameters can be adjusted, for example, by adjusting the time of the oxidation treatment and the reduction treatment. For example, as the treatment time of the oxidation treatment is increased, the first parameter, which is the sum of the thickness of the cuprous oxide (T1) and the thickness of the copper oxide (T2), tends to increase. Furthermore, as the treatment time of the reduction treatment is increased, the second parameter, which is the ratio (T2 / T1) of the thickness of the copper oxide (T2) to the thickness of the cuprous oxide (T1), tends to decrease. Taking advantage of this tendency, the oxidation-reduction treatment is performed so that the first and second parameters are each within the above-mentioned specific ranges.

[0035] The surface treatment step may be carried out continuously on copper material continuously supplied from a film roll or the like, or may be carried out batchwise for each predetermined unit. <Copper-clad laminate> A copper clad laminate is a laminate including a copper layer and an insulating resin layer laminated on the copper layer.

[0036] The copper layer is a layer made of a surface-treated copper material, at least one surface of which is the above-mentioned oxidized surface, and the thickness of the copper layer is the same as the thickness of the surface-treated copper material. The insulating resin layer is a layer laminated and bonded to the surface of the copper layer formed by the oxidized surface of the surface-treated copper material. The resin constituting the insulating resin layer is not particularly limited, and known resins used for flexible printed wiring boards, or substrates for semiconductor manufacturing equipment and thermoelectric conversion members can be used.

[0037] Examples of resins that can be used to form the insulating resin layer include polyimide (PI), liquid crystal polymer (LCP), polyether ether ketone (PEEK), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polytetrafluoroethylene (PTFE), tetrafluoroethylene-ethylene copolymer (ETFE), polyamideimide (PAI), cycloolefin polymer (COP), polyphenylene sulfide (PPS), and syndiotactic polystyrene (SPS). The insulating resin layer can be formed of one type of resin or a combination of two or more types.

[0038] Furthermore, the insulating resin layer preferably contains a thermoplastic resin. In this case, when the copper layer and the insulating resin layer are joined, the thermoplastic resin contained in the insulating resin layer is softened and penetrates into the fine uneven structure formed on the oxidized surface of the copper layer, thereby improving the adhesion between the copper layer and the insulating resin layer based on the anchor effect. In this case, among the above resins, it is particularly preferable to use at least one thermoplastic resin selected from polyimide (PI), liquid crystal polymer (LCP), polyether ether ketone (PEEK), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and polytetrafluoroethylene (PTFE).

[0039] The thickness of the insulating resin layer is not particularly limited and can be appropriately set depending on the application of the copper-clad laminate. The thickness of the insulating resin layer is, for example, 1 μm or more and 1000 μm or less, preferably 5 μm or more and 200 μm or less, and more preferably 12.5 μm or more and 100 μm or less.

[0040] The insulating resin layer may have a single layer structure or a laminated structure in which a plurality of resin layers are laminated. The insulating resin layer may be provided on only one surface of the copper layer, or on both surfaces of the copper layer. When the insulating resin layer is provided on both surfaces of the copper layer, it is preferable that both surfaces of the copper layer are oxidized surfaces.

[0041] <Method of manufacturing copper clad laminate> Next, a method for manufacturing a copper clad laminate will be described. The method for manufacturing a copper-clad laminate includes a lamination step of laminating and bonding an insulating resin to the oxidized surface of the surface-treated copper material. Examples of the lamination step include a process of thermocompression bonding a resin film made of an insulating thermoplastic resin, a process of applying a molten insulating resin to the oxidized surface of the surface-treated copper material and solidifying it, and a process of adhering an insulating resin film to the oxidized surface of the surface-treated copper material via a resin adhesive. Below, we will specifically explain the thermocompression bonding process as an example.

[0042] The thermocompression bonding treatment involves superposing a resin film on the oxidized surface of the surface-treated copper material, and then using a heating and pressing device to heat the surface-treated copper material and the resin film while applying a predetermined pressure. The thermocompression bonding treatment may be performed continuously on the surface-treated copper material and the resin film continuously supplied from a film roll or the like, or may be performed batchwise for each predetermined unit.

[0043] The heating temperature in the thermocompression bonding process is, for example, 300° C. to 400° C. The heating time in the thermocompression bonding process is, for example, 1 minute to 30 minutes. In the thermocompression bonding process, the pressure applied to the surface-treated copper material and the resin film is, for example, 2 MPa to 12 MPa.

[0044] The heating and pressing device is not particularly limited as long as it satisfies the above conditions, and examples of the heating and pressing device include a heat press having a flat heating and pressing section, a vacuum batch press, a multi-stage press, a heated roll press, and a double belt press in which heating and pressing are performed between belts.

[0045] Next, the operation and effects of this embodiment will be described. (1) The surface-treated copper material is used as a component of an article having a resin portion bonded to the oxidized surface of the surface-treated copper material. An example of such an article is a copper-clad laminate having a copper layer and an insulating resin layer laminated on the surface of the copper layer.

[0046] The surface-treated copper material has an oxidized surface containing cuprous oxide and copper oxide, in which the sum of the thickness of the cuprous oxide (T1) and the thickness of the copper oxide (T2) determined by continuous electrochemical reduction analysis is 1 nm or more and 40 nm or less, and the ratio (T2 / T1) of the thickness of the copper oxide (T2) to the thickness of the cuprous oxide (T1) is 1 or more and 9 or less.

[0047] By setting the sum of the thickness of the cuprous oxide (T1) and the thickness of the copper oxide (T2) on the oxidized surface of the surface-treated copper material and the ratio (T2 / T1) within the above-mentioned specific ranges, the adhesive strength of the bonded portion of an article formed by bonding a resin portion to the oxidized surface of the surface-treated copper material can be increased. In addition, even after the article is exposed to a high-temperature environment for a long period of time, the adhesive strength of the bonded portion can be prevented from decreasing, and the adhesive strength can be suitably maintained.

[0048] (2) The ratio (T2 / T1) of the thickness of the copper oxide (T2) to the thickness of the cuprous oxide (T1) is 3 or more and 6 or less. In this case, the effect of (1) above is remarkably obtained. (3) The thickness (T1) of the cuprous oxide on the oxidized surface is 0.1 nm or more and 20 nm or less. In this case, the effect of (1) above is remarkably obtained.

[0049] (4) The thickness (T2) of the copper oxide on the oxidized surface is 0.9 nm or more and 36 nm or less. In this case, the effect of (1) above is significantly obtained. (5) The resin constituting the insulating resin layer includes a thermoplastic resin.

[0050] In this case, the thermoplastic resin contained in the insulating resin layer softens and penetrates into the fine uneven structure formed on the oxidized surface of the copper layer, thereby improving the adhesion between the copper layer and the insulating resin layer based on the anchor effect.

[0051] (6) The thermoplastic resin constituting the insulating resin layer is at least one selected from the group consisting of polyimide, liquid crystal polymer, polyether ether ketone, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and polytetrafluoroethylene. In this case, the effect of (5) above can be significantly obtained.

[0052] (7) A method for producing a surface-treated copper material includes a surface treatment step of forming an oxidized surface containing cuprous oxide and copper oxide on the surface of the copper material. The surface treatment step is a heat treatment in which the surface of the copper material is heated in an oxidizing atmosphere so that the sum of the thickness of the cuprous oxide (T1) and the thickness of the copper oxide (T2) determined by continuous electrochemical reduction analysis is 1 nm or more and 40 nm or less, and the ratio (T2 / T1) of the thickness of the copper oxide (T2) to the thickness of the cuprous oxide (T1) is 1 or more and 9 or less.

[0053] According to the above-mentioned method, an oxidized surface can be formed in which the sum and ratio of the thickness of cuprous oxide and copper oxide are within a specific range without using various treatment solutions that require post-treatment, such as the oxidizing treatment solution and reducing treatment solution used in wet oxidation-reduction treatment. This reduces the environmental impact of wastewater generated during the production of surface-treated copper materials.

[0054] Furthermore, it is difficult to form a roughened surface on thick copper materials, such as copper materials with a thickness of 100 μm or more, used in semiconductor manufacturing equipment, thermoelectric conversion components, etc., using the methods disclosed in Patent Documents 1 and 2. According to the above configuration, a surface with high adhesive strength to resin can be formed even on thick copper materials.

[0055] Furthermore, according to the above-described configuration, by subjecting the surface of the copper material on which the rust-preventive layer is formed to the heat treatment, the surface on which the rust-preventive layer is formed can be made into an oxidized surface, i.e., an oxidized surface can be formed after the rust-preventive layer is formed.

[0056] The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0057] The use of the surface-treated copper material of the above embodiment is not limited to copper-clad laminates formed by laminating an insulating resin layer on the surface-treated copper material. The surface-treated copper material of the above embodiment can be applied to all components of articles having a resin portion bonded to the oxidized surface of the surface-treated copper material. In this case, the resin bonded to the oxidized surface of the surface-treated copper material is not limited to an insulating resin.

[0058] A copper clad laminate may be produced by successively carrying out a surface treatment step of forming an oxidized surface on the surface of a copper material, and a lamination step of laminating and bonding an insulating resin onto the oxidized surface of the surface-treated copper material obtained by the surface treatment step.

[0059] The copper clad laminate may have layers other than the copper layer and the insulating resin layer. [Example]

[0060] Next, the embodiment will be described more specifically with reference to examples and comparative examples. (Examples 1 to 7 and Comparative Examples 1 to 4) Copper foil was placed in a blast oven set at a predetermined temperature and subjected to heat treatment for a predetermined time, thereby producing surface-treated copper materials in Examples 1 to 7 and Comparative Examples 1 to 4. As shown in Table 1, the surface-treated copper materials in each example differed in the type and thickness of the copper foil used, as well as the temperature and time of the heat treatment. HCL-02Z or C1020 foil manufactured by Hitachi Metals Neomaterial was used as the copper foil. Comparative Example 1 was a copper foil that was not subjected to heat treatment.

[0061] (Continuous electrochemical reduction analysis) Measurement samples cut from the surface-treated copper materials of each Example and Comparative Example were immersed in a butyl cellosolve solution for 20 minutes, and then ultrasonically cleaned in a 2-propanol solution for 5 minutes to remove foreign matter. The thicknesses (T1) of cuprous oxide (CuO) and copper oxide (CuO) on the oxidized surface of the test samples were then measured by continuous electrochemical reduction analysis (SERA) using a measuring device (QC-100 manufactured by ECI Technology).

[0062] First, a circular area with a diameter of 0.16 cm on the test sample was isolated with a ring gasket, and the area was filled with electrolyte and saturated with nitrogen. The electrolyte was a borate buffer solution with a pH of 8.4, prepared with pure water to contain 6.18 g / L of boric acid and 9.55 g / L of sodium tetraborate decahydrate. Then, a current density of 150 μA / cm was applied. 2 The reduction reaction times (seconds) occurring at -0.35 to -0.60 V (CuO) and -0.60 to -0.85 V (CuO) were measured.

[0063] Based on the measured reduction reaction time, the CuO thickness (T1) and CuO thickness (T2) were calculated using the following formula. Furthermore, the total thickness (T1 + T2) and thickness ratio (T2 / T1) were calculated from the calculated CuO thickness (T1) and CuO thickness (T2). The results are shown in Table 1.

[0064] T1(nm)=0.001236×current density(μA / cm 2 ) x reduction time (seconds) T2(nm)=0.000639×current density(μA / cm 2 ) x reduction time (seconds)

[0065] [Table 1] By varying the temperature and time during the heat treatment, surface-treated copper materials of Examples 1 to 7 and Comparative Examples 1 to 4 were obtained, each having an oxidized surface with a different first parameter, the total thickness (T1+T2), and a different second parameter, the thickness ratio (T2 / T1). Note that Comparative Example 2 corresponds to the experimental example disclosed in the Examples section of Patent Documents 1 and 2, since the thickness of the cuprous oxide was greater than the thickness of the copper oxide. Furthermore, visual observation of the oxidized surfaces of the surface-treated copper materials obtained in each example revealed no discoloration or uneven heating.

[0066] (Test Examples 1 to 12) Copper-clad laminates of Test Examples 1 to 12, each comprising a copper layer made of the surface-treated copper material and a resin layer made of the resin film, were produced by laminating a 25 μm-thick resin film on the oxidized surface of the surface-treated copper material of each Example and Comparative Example and then thermocompression bonding using a batch press. The combinations of the surface-treated copper material and the resin film and the types of resin film in each Test Example are shown in Table 2. Details of the types of resin films and thermocompression bonding conditions shown in Table 2 are as follows.

[0067] PI-A: Polyimide film (Ube Industries, Ltd., Upilex-VT) LCP: Liquid crystal polymer film (CTZ manufactured by Kuraray Co., Ltd.) PI-B: Polyimide film (Kapton AENC manufactured by Toray DuPont Co., Ltd.) Condition 1: Maximum temperature 330°C, pressure 106 kg / cm 2 , heating time 30 minutes Condition 2: Maximum temperature 305°C, pressure 106 kg / cm 2 , heating time 10 minutes (Evaluation of Adhesion) After production, the copper-clad laminates of each test example were stored at room temperature and pressure and then cut into 10 mm wide strips to prepare test samples. The peel strength between the copper layer and the resin layer of the test samples was measured using "Method A" (90° peeling method, where the resin layer is peeled at a 90° angle to the surface of the copper layer on which the resin layer is laminated) as specified in JIS C6471. The measured value was taken as the normal peel strength. The results are shown in Table 2.

[0068] Next, the copper-clad laminates of the test examples, which had a peel strength of 1.0 N / mm or more under normal conditions, were exposed to a high-temperature environment at 150°C for 1,000 hours and then cut into 10 mm-wide strips to prepare test samples. The peel strength between the copper layer and the resin layer of the test samples obtained from the copper-clad laminates after the exposure treatment was measured using the same method as above. The measured value was taken as the peel strength after high-temperature exposure, and the peel strength retention rate before and after the exposure treatment was calculated using the following formula. The results are shown in Table 2.

[0069] Retention rate (%) = (peel strength after high temperature exposure / peel strength under normal conditions) x 100

[0070] [Table 2] As shown in Table 2, Test Examples 1 to 7 used the surface-treated copper materials of Examples 1 to 7, which had a total thickness (T1 + T2) of 1 nm or more and 40 nm or less and a thickness ratio (T2 / T1) of 1 or more and 9 or less. The peel strengths of Test Examples 1 to 7 in the normal state were higher than those of Test Examples 8 and 12, which used the surface-treated copper material of Comparative Example 1. In addition, the peel strength retention rates of Test Examples 1 to 7 were 60% or more. Among Test Examples 1 to 7, Test Examples 1 to 4, which used the surface-treated copper materials of Examples 1 to 4, which had a thickness ratio (T2 / T1) of 3 or more and 6 or less, had a high retention rate of 70% or more. Furthermore, these effects were obtained even when the type and thickness of the copper foil and the type of resin were changed, and therefore are considered to be effects independent of the type and thickness of the copper foil and the type of resin.

[0071] In Test Examples 9 and 11, which used the surface-treated copper materials of Comparative Examples 2 and 4, in which the total thickness (T1 + T2) was within the above range and the thickness ratio (T2 / T1) was outside the above range, the peel strength in the normal state was similar to that of Test Examples 1 to 7, but the peel strength retention rate was almost zero. From these results, it is considered that in order to maintain peel strength even after exposure to high temperatures, it is important to form an oxidized surface so that it contains more copper oxide than cuprous oxide.

[0072] Furthermore, Test Example 10, which used the surface-treated copper material of Comparative Example 3, in which the total thickness (T1+T2) and the thickness ratio (T2 / T1) were both outside the above ranges, had a lower peel strength in the normal state than Test Examples 1 to 7, and the heat treatment did not improve the peel strength. It is believed that the oxidized surface of the surface-treated copper material of Comparative Example 3 used in Test Example 10 became structurally fragile due to the formation of excessive copper oxide.

Claims

1. A surface-treated copper material having an oxidized surface containing cuprous oxide and copper oxide, The oxidized surface is characterized in that the sum of the thickness (T1) of the cuprous oxide and the thickness (T2) of the copper oxide, as determined by continuous electrochemical reduction analysis, is 1 nm or more and 13.6 nm or less, and the ratio (T2 / T1) of the thickness (T2) of the copper oxide to the thickness (T1) of the cuprous oxide is 3 or more and 6 or less.

2. 2. The surface-treated copper material according to claim 1, wherein the thickness (T1) of the cuprous oxide on the oxidized surface is 0.1 nm or more.

3. 3. The surface-treated copper material according to claim 1, wherein the thickness (T2) of the copper oxide on the oxidized surface is 0.9 nm or more.

4. A copper clad laminate comprising a copper layer made of the surface-treated copper material according to any one of claims 1 to 3 and an insulating resin layer laminated on the oxidized surface of the copper layer.

5. The copper clad laminate according to claim 4 , wherein the resin constituting the insulating resin layer includes a thermoplastic resin.

6. The thermoplastic resin is at least one selected from polyimide, liquid crystal polymer, polyether ether ketone, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and polytetrafluoroethylene. The copper clad laminate according to claim 5.

7. A surface treatment step of forming an oxidized surface containing cuprous oxide and copper oxide on the surface of a copper material, In the surface treatment step, the surface of the copper material is oxidized so that the sum of the thickness (T1) of the cuprous oxide and the thickness (T2) of the copper oxide, as determined by continuous electrochemical reduction analysis, is 1 nm or more and 13.6 nm or less, and the ratio (T2 / T1) of the thickness of the copper oxide (T2) to the thickness (T1) of the cuprous oxide is 3 or more and 6 or less.

8. A method for manufacturing a copper clad laminate comprising a copper layer and an insulating resin layer laminated on a surface of the copper layer, A method for producing a copper clad laminate, comprising a lamination step of laminating and bonding an insulating resin to the oxidized surface of the surface-treated copper material according to any one of claims 1 to 3.

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