TW201437434A - Electrolytic copper foil and process for producing same - Google Patents

Abstract

An electrolytic copper foil (1) characterized by comprising copper crystal grains (3) and, present inside the copper crystal grains (3) or at the boundaries thereamong, inclusions (5) having an average diameter of 0.5-100 nm, wherein the inclusions comprise an inorganic compound and/or an organic compound, the inorganic compound comprising an oxide of at least one metallic element selected from the group consisting of tungsten, molybdenum, titanium, and tellurium and the organic compound comprising at least one thiourea-based organic compound selected from the group consisting of thiourea, ethylenethiourea, tetramethylthiourea, and 1,3-dimethyl-2-thiourea.

Description

Electrolytic copper foil and method of manufacturing same Field of invention

The present invention relates to an electrolytic copper foil used for a negative electrode current collector or the like of a high capacity lithium ion secondary battery using an alloy negative electrode active material.

Background of the invention

Electrolytic copper foil has been used for rigid printed wiring boards, flexible printed wiring boards, electromagnetic shielding materials, battery current collectors, and the like.

In the field of flexible printed wiring boards (hereinafter referred to as "FPC") which are bonded to polyimide film in these fields, as a hard disk drive (hereinafter referred to as "HDD") suspension material or tape automatic combination (hereinafter referred to as "TAB") material, it is required to increase the strength of the copper foil.

With the development of high-capacity HDDs, most of the suspensions mounted on HDDs have been converted from conventionally used wire-type suspensions to wire-integrated types that ensure stable buoyancy and positional accuracy of floating heads with respect to memory media. Suspension.

The wiring integrated suspension is divided into the following three types, namely: (1) FSA (flex suspension assembly) suspension, which processes the flexible printed substrate and uses a bonding agent to make it fit; 2) CIS (circuit Integrated suspension, line-integrated cantilever method, suspension processing on the precursor of polyimine resin, ie, lysine, to form polyimine, and then electroplating on the obtained polyimine , thereby forming a type of wiring; (3) TSA (trace suspension assembly) suspension, processing a three-layer laminate composed of a stainless foil-polyimine resin-copper foil into a laminate by etching Specifies the type of shape.

Among them, since the TSA suspension suspends the high-strength stainless foil and the copper foil, the flying wire can be easily formed, and the shape processing has a high degree of freedom of processing, is inexpensive, and has high dimensional accuracy, and is therefore widely used.

The laminate system formed by the TSA method is made of a material having a thickness of about 12 to 30 μm in a stainless foil, a thickness of about 5 to 20 μm in a polyimide layer, and a thickness of about 7 to 14 μm in a copper foil.

When producing a laminate, first, a polyimide-containing resin precursor liquid is applied onto a stainless foil as a substrate. After coating, the solvent is removed by preheating, and then heat treatment is performed to form a polyimide, and then the copper foil is superposed on the polyimide layer of the polyamidimide resin at a temperature of about 300 ° C. After lamination by heating and pressure bonding, lamination was carried out to obtain a laminate comprising a stainless steel layer-polyimine layer-copper layer.

Under the heating of about 300 ° C, the size of the stainless foil is substantially unchanged. However, when the conventional electrolytic copper foil is used, the electrolytic copper foil is annealed at a temperature of about 300 ° C, and recrystallization occurs, and dimensional change occurs after softening. Therefore, the laminated body is warped after lamination, and the dimensional accuracy of the product is lowered.

In order to prevent the laminate from being lifted after lamination, it is required to provide a copper foil having a dimensional change as small as possible during heating.

As a copper foil which satisfies this requirement, a rolled copper alloy foil has been conventionally used. The rolled copper alloy foil is less likely to be annealed at a temperature of about 300 ° C, and the dimensional change during heating is small, and the mechanical strength is also less changed.

The rolled copper alloy foil refers to a copper alloy containing at least one or more elements other than copper such as tin, zinc, iron, nickel, chromium, phosphorus, zirconium, magnesium, or antimony as a main component of copper. Foiled foil. Depending on the type and combination of the elements, one of the rolled copper alloy foils is less likely to be annealed under heating at about 300 ° C, and tensile strength, 0.2% endurance, elongation, and the like are not substantially changed.

For example, Cu-0.2mass%Cr-0.1mass%Zr-0.2mass%Zn (Cu-2000ppmCr-1000ppmZr-2000ppmZn) such rolled copper alloy foils can be applied to HDD suspension materials in addition to the TSA suspension.

In addition, the TAB material is also required to have high strength in copper foil, similar to the TSA suspension and the HDD suspension material.

In the TAB product, a plurality of terminals of the IC chip are directly combined with inner leads (flying wires) disposed at the device holes located at almost the center of the product.

In this case, a combination device (welding machine) can be used to apply a certain bonding pressure by instantaneous energization heating. At this time, the inner lead obtained by etching the electrolytic copper foil may be stretched due to the bonding pressure, resulting in an excessive elongation.

By increasing the strength of the electrolytic copper foil, internal leads are less likely to be slack and broken. Therefore, if the strength of the electrolytic copper foil is too small, the following problems occur due to plastic deformation, that is, the inner lead is slack and severely broken.

On the other hand, when the surface of the copper foil is made low in thickness, when the TAB wiring is formed by etching, it is possible to prevent the wiring sidewall from being excessively thinned by over-etching, and etching can form a thin line. The reason for this is as follows: Generally, the wiring of HDD and TAB is formed by heating a laminated copper foil on a polyimide substrate, and then applying a protective film to form a protective film. At this time, if the surface roughness of the copper foil is coarse, the copper foil is caught on the surface of the polyimide, and when the trapped portion is removed by etching, the side walls of the wiring are excessively etched, resulting in a narrow line width. In order to avoid this, it is desirable to achieve a low thickness of the surface of the copper foil.

Therefore, in order to make the line width of the inner lead thinner, the electrolytic copper foil to be used is required to have a rough surface having a low thickness and a high strength.

In this case, it is also required that the copper foil or the copper alloy foil has a high strength in a normal state (25 ° C, 1 atm, the same below), and is also high in strength after heating.

For TAB, a two-layer FPC in which a copper foil and a polyimide layer are bonded or a three-layer FPC in which a copper foil, a polyimide layer, and a binder layer are bonded is used. When a three-layer FPC is bonded to a copper foil with a polyimide, it is bonded at a temperature of about 180 ° C using an epoxy-based adhesive. Further, two layers of FPC using a polyimide pigment adhesive were bonded at a temperature of about 300 °C.

In the past, high-strength electrolytic copper foils have high mechanical strength under normal conditions due to the use of organic additives. Even when heated at about 180 ° C, the mechanical strength is basically It does not change, but when it is heated at about 300 ° C, annealing occurs and recrystallization is performed, so that it softens rapidly and the mechanical strength is remarkably lowered.

It is known that the use of an organic additive to achieve high strength is that organic molecules derived from an additive taken up in the copper foil during electrolysis hinder recrystallization. In the past, high-strength foils were recrystallized at around 300 ° C due to the decomposition temperature of organic molecules. Currently, the industry is investigating the use of inorganic additives with higher decomposition temperatures.

For example, Patent Document 1 discloses a method of producing an electrolytic copper foil by adding tungsten or a tungsten compound to a sulfuric acid acidic copper sulfate electrolyte, further adding a gel, and a chloride ion of 20 to 120 mg/L, and using the electrolytic solution thus obtained. . According to this document, as a result, a copper foil having a heating elongation of 3% or more at 180 ° C, a large rough surface roughness, and a small occurrence of pinholes can be produced.

Patent Document 2 describes an electrolytic copper foil containing silver (Ag).

This document states that an electrolytic copper foil is produced by using a sulfuric acid acidic copper sulfate electrolyte to which a silver salt of a predetermined concentration of silver ions is added, whereby silver eutectoid is present in the electrolytic copper foil.

Patent Document 3 describes a dispersion-strengthened electrolytic copper foil in which copper is present as fine crystal grains and SnO _{2 is} dispersed as ultrafine particles.

According to the description in Patent Document 3, the sulfuric acid acidic copper sulfate electrolyte contains an organic additive such as copper ions, sulfate ions, tin ions, and polyethylene glycol, and is subjected to bubbling treatment using an oxygen-containing gas to form SnO in the electrolytic solution. ₂ ultrafine particles, and the above dispersion-strengthened electrolytic copper foil was obtained using the electrolytic solution.

Prior technical literature Patent literature

Patent Document 1: Japanese Patent No. 3238278

Patent Document 2: Japanese Patent No. 3943214

Patent Document 3: Japanese Patent Laid-Open Publication No. 2000-17476

Summary of invention

Therefore, the inventors of the present invention added a tungsten or tungsten compound to a sulfuric acid-copper sulfate electrolyte according to Patent Document 1, and then added a colloidal ion with a chloride ion of 20 to 120 mg/L, and repeatedly performed an electrodeposition experiment using the obtained electrolyte to confirm According to the method described in Patent Document 1, a target copper foil, that is, a copper foil having a heating elongation at 180 ° C of 3% or more, a large rough surface, and a small occurrence of pinholes can be produced.

However, after analyzing the copper foil, it was confirmed that the electrolytic copper foil contained almost no tungsten, and the strength was extremely lowered after heating at 300 ° C (refer to Comparative Example 4 described later).

In the same manner as the electrolytic copper foil using the organic additive, the electrolytic copper foil described in Patent Document 2 is also significantly reduced in mechanical strength when heated at a high temperature of about 300 ° C (see Comparative Example 14 to be described later).

The problem of the dispersion-strengthened electrolytic copper foil in which SnO _{2 is} dispersed in Patent Document 3 is that not only the manufacturing cost is increased by the bubbling treatment, but also the particle diameter of the SnO ₂ fine particles is relatively large, resulting in a low electrical conductivity (refer to the following description). Comparative Example 13).

Therefore, the conventional method has a problem that it is impossible to provide an electrolytic copper foil which has a large mechanical strength in a normal state when it is used as a battery negative electrode current collector or a wiring board material, and is difficult to reduce mechanical strength at the time of high-temperature heating.

The present invention has been made in view of the above problems, and an object thereof is to provide an electrolytic copper foil having a high mechanical strength in a normal state. Furthermore, an electrolytic copper alloy foil in which mechanical properties are hardly deteriorated when heated at a high temperature of about 300 ° C is provided.

The inventors have conducted intensive studies and found that the nano inclusions containing organic or inorganic compounds are dispersed in the copper foil, and the particle size of the nano inclusions is within a predetermined range, and the mechanical strength under normal conditions can be obtained. Electrolytic copper alloy foil.

In particular, it has been found that the nano-inclusion formed of the inorganic compound is dispersed in the copper foil, and an electrolytic copper alloy foil having a small thermal deterioration of mechanical strength when heated at about 300 ° C can be obtained.

The present invention has been completed based on the above findings.

In order to achieve the above object, the following invention is provided.

(1) An electrolytic copper foil characterized in that an inclusion having an average particle diameter of 0.5 to 100 nm is present in a grain boundary between copper crystal grains or copper crystal grains, and the inclusion contains an inorganic compound and/or an organic compound. The inorganic compound contains an oxide selected from one or more metal elements selected from the group consisting of tungsten, molybdenum, titanium, and niobium, and the organic compound contains a compound selected from the group consisting of thiourea, ethyl thiourea, and tetramethyl thiourea. One or more thiourea organic compounds in the group consisting of 3-dimethyl-2-thiourea and 1,3-diethyl-2-thiourea.

(2) The electrolytic copper foil according to (1), wherein the crystal grains have an average particle diameter of 100 to 600 nm.

(3) The electrolytic copper foil according to (1) or (2), wherein the inclusions have an average particle diameter of 0.5 to 50 nm.

(4) The electrolytic copper foil according to (3), wherein the inclusions have an average particle diameter of 0.5 to 20 nm.

(5) The electrolytic copper foil according to any one of (1) to (4) wherein the inclusion contains an inorganic compound, and the content of the metal element in the electrolytic copper foil is 10 to 2610 ppm.

(6) The electrolytic copper foil according to any one of (1) to (4) wherein the chlorine content in the electrolytic copper foil is less than 1 ppm.

(7) An electrode for a non-aqueous electrolyte secondary battery, comprising: a current collector comprising the electrolytic copper foil according to any one of (1) to (6); and a surface formed on the surface of the current collector And an electrode active material layer having an electrode active material.

(8) A nonaqueous electrolyte secondary battery using the electrode for a nonaqueous electrolyte secondary battery according to (7).

(9) A method for producing an electrolytic copper foil, comprising adding an aqueous solution containing an inorganic compound and/or an aqueous solution containing an organic compound to a sulfuric acid-copper sulfate-based electrolytic solution containing sulfuric acid and copper sulfate, and using the electrolytic solution An electrolytic solution containing the inorganic compound is prepared by electrolysis, and the aqueous solution containing the inorganic compound is an aqueous solution obtained by dissolving a salt of at least one metal element selected from the group consisting of tungsten, molybdenum, titanium, and niobium. The aqueous solution contains a selected from the group consisting of thiourea, ethyl thiourea, tetramethyl An aqueous solution of one or more thiourea organic compounds in the group consisting of thiourea, 1,3-dimethyl-2-thiourea, and 1,3-diethyl-2-thiourea.

(10) The method for producing an electrolytic copper foil according to (9), wherein the electrolyte solution has a chloride ion concentration of less than 3 mg/L.

According to the present invention, an electrolytic copper foil having a high mechanical strength in a normal state can be provided. In addition, the normal state here is a state in which the electrolytic copper foil is produced and placed under normal temperature and normal pressure (25 ° C, 1 atm) before the heat treatment. Further, mechanical strength means tensile strength, 0.2% endurance, and the like.

1‧‧‧electrolytic copper foil

3‧‧‧ grain

5‧‧‧ inclusions

13‧‧‧X-ray source

14‧‧‧ incident X-rays

15‧‧ ‧Shutter

17‧‧‧ Monochromator

19‧‧‧1st pinhole

21‧‧‧2 pinhole

23‧‧‧Attenuator

25‧‧‧3rd pinhole

27‧‧‧ sample

29‧‧‧Transmission of X-rays

31‧‧‧scatter X-ray

33‧‧‧Block stopper

35‧‧‧Detector

Fig. 1 is a schematic view showing the configuration of an electrolytic copper foil 1 according to the present embodiment.

Fig. 2 is a TEM image (under focus image) of the electrolytic copper foil containing W before the heat treatment.

Fig. 3 is a TEM image (under focus image) of the electrolytic copper foil containing W after heat treatment.

Fig. 4 is a high-resolution STEM image (HAADF-STEM image) of the electrolytic copper foil containing W after heat treatment.

Figure 5 is a HAADF-STEM image of a copper foil containing both ethyl thiourea and tungsten.

Fig. 6 is a TEM image (under-focus image) of a copper foil containing no W.

Fig. 7(a) is a schematic view of a device of SAXS (USAXS), Fig. 7(b) is a view showing a case of measuring scattered X-rays, and Fig. 7(c) is a view showing measurement of transmitted X-rays. Diagram of the situation.

Fig. 8(a) is a view showing the results of SAXS measurement before and after firing of the electrolytic copper foil containing W, and Fig. 8(b) shows the pre-baking and firing of the electrolytic copper foil containing Mo. Fig. 8(c) is a view showing the results of SAXS measurement before and after firing of the electrolytic copper foil containing W and TU (thiourea).

Fig. 9 shows the results of one-dimensional SAXS measurement before firing of the electrolytic copper foil containing W.

Fig. 10(a) is a view showing a fitting result of SAXS measurement of an electrolytic copper foil containing W before firing, and Fig. 10(b) is a view showing a particle size distribution measured by SAXS.

Fig. 11 (a) is a view showing XAFS measurement results in the vicinity of the W absorption end of the electrolytic copper foil containing W before firing, and Fig. 11 (b) is a XAFS measurement in the vicinity of the Mo absorption end of the electrolytic copper foil containing Mo before firing. The graph of the result.

Form for implementing the invention (electrolytic copper foil)

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

Fig. 1 is a view showing an electrolytic copper foil 1 according to an embodiment of the present invention. The electrolytic copper foil 1 has a large number of crystal grains 3 of copper, and has inclusions 5 inside the crystal grains 3 or at grain boundaries between the crystal grains 3.

The crystal grains 3 are preferably fine crystal grains of a base material, that is, copper, and the average particle diameter is preferably from 100 to 600 nm. Further, the average particle diameter of the crystal grains 3 herein means the average number of the long axis lengths of the respective particles. The shape of the crystal grain 3 is a substantially spherical shape, and the longitudinal axis of the long axis and the short axis The inch ratio is about 0.5~2.0. The polished surface of the copper foil can be observed by SIM (scanning ion microscopy), and the observed image is subjected to image processing to calculate the average grain size of the crystal grains 3.

The inclusions 5 are fine particles containing an organic compound and/or an inorganic compound, and are not alloyed with copper, which is a base material, but are present as fine particles in the copper foil. The average particle diameter (diameter) of the inclusions 5 is 0.5 to 100 nm, preferably 0.5 to 50 nm, and preferably 0.5 to 20 nm.

The inorganic compound contained in the inclusion 5 preferably contains one or more metal elements selected from the group consisting of tungsten, molybdenum, titanium, and niobium, and more preferably these metal oxides. These metals exist as oxides in a liquid having a pH of 4 or less.

Regarding the metal present as an oxide in an acidic solution of pH 4 or lower, for example, in the potential-pH diagram shown by M. Pourbaix, Atlas of electrochemical equilibria in aqueous solutions. Pergamon Press (1966), in pH below 4, The metal component in which the oxide is present is a metal component in which the added metal component is detected as a solid particle when the particle size distribution of the electrolytic solution to which the metal component is actually added is measured by DLS (Dynamic Light Scattering).

The organic compound contained in the inclusion 5 preferably contains a compound selected from the group consisting of thiourea, ethyl thiourea, tetramethyl thiourea, 1,3-dimethyl-2-thiourea, and 1,3-diethyl-2- More than one thiourea organic compound in the group consisting of thiourea.

The inclusion 5 contained in the electrolytic copper foil 1 may contain only an organic compound, may contain only an inorganic compound, or may contain an organic compound and an inorganic compound. Both. When the fine particles of the inorganic compound are not thermally decomposed when heated at 300 ° C, the fine particles having the inorganic compound are used as the inclusions 5, and the deterioration of the strength of the electrolytic copper foil after heating can be suppressed.

The content (intake amount) of the metal constituting the inclusion 5 in the electrolytic copper foil is preferably 10 to 2610 ppm in terms of metal. Further, it is preferably 15 to 2610 ppm, preferably 80 to 2610 ppm, preferably 100 to 2500 ppm, more preferably 110 to 2460 ppm, and particularly preferably 210 to 2460 ppm. If the content is too small, the heat resistance effect is lowered. For example, the tensile strength after heating at 300 ° C is lowered, and it is 80% or less of the normal tensile strength. On the other hand, if the content is too large, the effect of improving the tensile strength cannot be further improved, and the electrical conductivity is lowered. In particular, when the metal constituting the inclusion 5 is tungsten, the tungsten content in the electrolytic copper foil is preferably 280 to 2,460 ppm. The reason for this is that if it is in this range, the ratio of the tensile strength to the normal tensile strength after heating at 300 ° C for 1 hour (hereinafter referred to as "300 ° C × 1 H") exceeds 80%.

Then, the chlorine content (intake amount) in the electrolytic copper foil is less than 1 ppm. When the chlorine content of the electrolytic copper foil is 1 ppm or more, the intake amount of the metal oxide is extremely reduced, and the effect of improving the tensile strength and heat resistance is lowered. Further, a chlorine content of less than 1 ppm also includes a case where chlorine is not present, i.e., the chlorine content is 0 ppm.

(Manufacturing method of electrolytic copper foil)

The electrolytic copper foil according to the present embodiment can be produced by the following production method.

An organic compound such as thiourea or an inorganic compound fine particle is added to the aqueous copper sulfate solution, and the copper sulfate aqueous solution is further used to electrically analyze the copper to produce an electrolytic copper foil.

When the electrolytic copper foil containing an inorganic compound is produced, first, hydrochloric acid or a water-soluble chlorine-containing compound is added to a mixed liquid of the copper sulfate aqueous solution and the metal metal salt aqueous solution to prepare a electrolyte having a chloride ion concentration of 3 mg/L or less. . Thereafter, an electrolytic copper foil was produced by electrical analysis using the above electrolytic solution.

Electrolyte composition

As the electrolytic solution, a copper sulfate-containing aqueous solution adjusted to have a copper ion concentration of 50 to 200 g/L, a free sulfate ion concentration of 30 to 400 g/L, and a chloride ion concentration of 3 mg/L or less is used as a basic electrolyte composition. Here, in the present invention, the absence of chloride ions means that the chloride ion concentration is 3 mg/L or less.

Copper ions and free sulfate ions can be obtained by adjusting the aqueous copper sulfate solution in accordance with the concentration of each of the ions. Alternatively, sulfuric acid may be added to an aqueous copper sulfate solution to which a predetermined copper ion concentration is applied to adjust the ion concentration thereof.

The chloride ion can be imparted by hydrochloric acid or a water-soluble chlorine-containing compound. As the water-soluble chlorine-containing compound, for example, sodium chloride, potassium chloride, ammonium chloride or the like can be used.

2. Addition of inorganic compound inclusions

The aqueous solution of the metal salt obtained by dissolving the salt of the above metal is added to the electrolyte having a pH of 4 or less, and is preferably added to the acidic electrolyte of sulfuric acid, thereby making the metal oxygen The fine particles or ultrafine particles of the compound are dispersed in the electrolyte and are taken up into the copper foil upon electrolysis. In addition, in the present specification, "fine particles or ultrafine particles" means those having a smaller particle diameter than conventional fine particles (about 20 nm).

The metal salt is ionized in a solvent such as water (pH greater than 4 and less than 9), alkali (pH 9 or higher), or hot concentrated sulfuric acid, and may be an oxide at pH 4 or less. limit. Examples of the metal salt include a oxyacid salt of each of the metals W or Mo, and a sulfate salt when the metal is Ti. For example, a tungstate such as sodium tungstate, potassium tungstate or ammonium tungstate, or a molybdate such as sodium molybdate, potassium molybdate or ammonium molybdate, or a titanium salt such as titanium sulfate can be used.

Further, ruthenium is usually classified as a metalloid, and strictly speaking, its salt does not belong to a metal salt, but ionization occurs in a solvent, and becomes an oxide at a pH of 4 or less. For example, after cerium oxide is ionized in hot concentrated sulfuric acid, it is added to an electrolyte having a pH of 4 or less, and cerium oxide or antimony trioxide is precipitated. Further, when the aqueous solution in which the citric acid is dissolved in an alkali atmosphere is adjusted to pH 4 or lower, cerium oxide or antimony trioxide is precipitated.

The concentration of the metal element in the electrolytic solution is preferably from 1 mg/L to 500 mg/L (calculated as the metal), and more preferably from 10 mg/L to 250 mg/L (in terms of the metal). If the concentration is too low, it is difficult to sufficiently ingest the target metal into the copper foil. On the other hand, if the concentration is too high, the target metal may be excessively taken up in the copper foil, and the electrical conductivity may be lowered, or the heat resistance may be saturated, and the heat resistance may be lowered, and the tensile strength after heating may be caused. reduce. In particular, when tungsten is used as the added metal element, the concentration of the metal element in the electrolytic solution is preferably 10 to 500 mg/L, more preferably 30 to 380 mg/L.

In the present embodiment, in order to adjust to the above-mentioned predetermined chloride concentration, the water used to prepare the electrolytic solution or the aqueous metal salt solution should preferably contain no chloride ions. In view of this point of view, it is preferred to dissolve the metal salt in pure water to prepare an aqueous metal salt solution. Here, the pure water is preferably water which does not contain metal ions and chloride ions as much as possible. Specifically, water having a chloride ion concentration of 3 mg/L or less is preferred, and water having a chloride ion concentration of less than 1 mg/L is more preferred.

3. Addition of organic compound inclusions

When an organic compound is used as the inclusion, an organic additive is added simultaneously with or in place of the above aqueous solution of the metal salt. That is, an organic additive is directly added to the copper sulfate electrolyte, or an organic additive is added as an aqueous solution. As the organic additive, any one of thiourea, exoethylthiourea, tetramethylthiourea, 1,3-dimethyl-2-thiourea, and 1,3-diethyl-2-thiourea can be used. The above organic compounds. The concentration of the organic additive in the electrolyte is preferably from 3 mg/L to 100 mg/L, and preferably from 5 to 15 mg/L.

Electrolytic analysis using a copper sulfate electrolyte containing an organic additive can produce an electrolytic copper foil containing inclusions of an organic compound.

4. Manufacturing conditions

The conditions at the time of electroanalysis are as follows.

Current density 30~100A/dm ²

Temperature 30~70°C

An electrolytic copper foil having a film thickness of, for example, 12 μm can be produced under the above conditions.

Specifically, copper can be electrically analyzed from the above-mentioned electrolytic solution on a rotating titanium drum, peeled off, and continuously wound up to produce an electrolytic copper foil.

(Mechanism of adding inclusions)

The aqueous metal salt solution is added to the electrolytic solution in order to allow the metal in the copper foil to be present as an ion thereof in the aqueous solution, and to put it into the electrolytic solution. By such an input method, fine particles or ultrafine particles of metal oxide can be formed when metal ions are converted into oxides in an electrolytic solution having a pH of 4 or less. On the other hand, even if the metal salt is directly introduced into the electrolytic solution, fine particles or ultrafine particles of the metal oxide cannot be formed, and thus the effect of improving the tensile strength and the heat resistance cannot be obtained.

The chloride ion in the electrolyte is suppressed to a low concentration of 3 mg/L in order to prevent chlorine from adsorbing on the surface of the copper when the fine particles or ultrafine particles of the metal oxide are precipitated, thereby hindering the fine particles or ultrafine particles of the metal oxide. Adsorption. When the concentration of the chloride ion is higher than 3 mg/L, the amount of metal in the electrolytic copper foil is reduced, and the effect of improving tensile strength and heat resistance is drastically lowered.

(the obstacle effect of the difference)

In the case of the copper foil, the metal material is recrystallized after heating to a temperature higher than the recrystallization temperature, and the crystal grains become coarse, and as a result, the strength is lowered. Here, the starting point of the recrystallization process is the movement (motion) of the difference row (an unstable state such as a lattice defect). In the electrolytic copper foil of the present invention, fine particles or ultrafine particles of metal oxide are dispersed to the mother phase Inside, thereby hindering the movement of the particles or the difference between the ultrafine particles. Therefore, the difference in the copper foil becomes difficult to move, and the strength of the copper foil becomes high.

In addition, the movement of the difference row requires higher energy (heat), so if the copper foil is not heated at a higher temperature, softening does not occur. That is, the heat resistance of the copper foil is improved by hindering the movement of the difference row.

In the present application, this case is referred to as "the barrier effect of the difference row is high".

(Foil thickness of electrolytic copper foil)

The foil thickness of the electrodeposited copper foil of the present embodiment is not particularly limited, and can be adjusted according to the foil thickness required for the intended use. For example, when used in a flexible printed wiring board (FPC), the foil thickness can be adjusted to 3 to 20 μm. On the other hand, when used for a negative electrode current collector for a lithium ion secondary battery, the foil thickness may be adjusted to 5 to 30 μm.

(physical properties of electrolytic copper foil)

The electrical conductivity of the electrolytic copper foil of the present embodiment is preferably 55% IACS or more, more preferably 65% IACS or more, and particularly preferably 70% IACS or more. The upper limit of the conductivity is not particularly limited, and sometimes exceeds 100% IACS.

The value of the tensile strength of the electrodeposited copper foil according to the present embodiment in a normal state is preferably 500 MPa or more, more preferably 600 MPa or more. The upper limit of the tensile strength in the normal state is not particularly limited, but is usually 1100 MPa or less.

After the electrolytic copper foil of the present invention is subjected to heat treatment at 300 ° C, the ratio of the tensile strength measured at normal temperature to the value of the tensile strength under normal conditions is preferably 50%. Above, more than 80% is better, and the ratio is more than 90%. The upper limit of the ratio is not particularly limited, and sometimes exceeds 100% (i.e., the tensile strength increases after heating).

(Mechanism for improving mechanical strength)

In metal materials, the relationship between mechanical strength and grain follows the Hall-Petch rule. In this rule, the smaller the crystal grains, the higher the mechanical strength. Actually, the electrolytic copper foil to which no additive is added has a crystal grain size of several tens of μm, and its mechanical strength under normal conditions is about 200 MPa. On the other hand, the electrolytic copper foil of the present invention has a crystal grain of 100 to 600 nm and a mechanical strength of 800 MPa or more. Even if the strengthening of the electrolytic copper foil of the present invention is not due to the crystal grain size, it can be said that the electrolytic copper foil follows the above rule to some extent.

However, if the copper foil itself is fired, the crystal grains grow and become coarse. As a result, the problem of the strength of the electrolytic copper foil is lowered. Therefore, in the electrodeposited copper foil of the present embodiment, inclusions are dispersed, and the pinning effect (pin fixing effect) for suppressing crystal growth is as follows.

(the pinning effect of inhibiting crystal growth)

The thermal deterioration of the mechanical strength at a high temperature of 300 ° C is still small because the crystal grains of copper as the mother phase are not coarsened. As mentioned above, it is well known that mechanical strength and grain size generally follow the Hall-Page rule. It is generally believed that the reason why the crystal grains of copper do not grow during the heating process is the pinning effect of the inclusions.

According to the Gibbs-Thomson formula, the grain growth ability can be approximated by the formula (1).

△G=4σV/D‧‧‧(1)

ΔG: grain growth ability, σ: grain boundary energy, D: grain diameter, V: molar volume. On the other hand, according to the Zener-Smith model, the resistance of grain growth can be approximated by the equation (2).

△G _pin =πdσnV/2‧‧‧(2)

ΔG _pin : resistance to grain growth, σ: grain boundary energy, d: inclusion diameter, V: molar volume, n: number of inclusions per unit area. In order to suppress grain growth, ΔG = ΔG _{pin is required} . That is, it is desirable that the formula (3) is established in a state in which the pinning effect appears.

D=8/πdn‧‧‧(3)

Since the grain size of the copper as the mother phase is 100 to 600 nm on average, the size of the precipitate is 0.5 to 100 nm, and the density of the precipitate is 1.0 × 10 ¹⁶ to 1.0 × 10 ¹⁹ /cm ³ , so that a sufficient nail can be expected. Tie effect. The area shown below is the pinning effect.

The size of the precipitate: 0.5~20nm→ can best exert the pinning effect, and can inhibit the growth of the grain at high temperature.

The size of the precipitate: 20~50nm→ can exert the pinning effect, but it can not completely inhibit the crystal growth. However, the reduction in mechanical strength before and after firing can be controlled to a maximum of about 80%.

The size of the precipitate: 50 to 100 nm → the pinning effect can be exerted, but a large amount of crystal grains are observed to be coarse. The reduction in mechanical strength before and after firing is up to 60%.

The number density of precipitates: (A) 1.0 × 10 ¹⁸ ~ 1.0 × 10 ¹⁹ / cm ³ → The pinning effect is most exerted, and the growth of crystal grains can be suppressed at a high temperature.

The number density of precipitates: (B) 1.0 × 10 ¹⁷ ~ 1.0 × 10 ¹⁸ / cm ³ → The pinning effect can be exerted, but the crystal growth cannot be completely suppressed. However, the reduction in mechanical strength before and after firing can be controlled to a maximum of about 80%.

The number density of precipitates: (C) 1.0 × 10 ¹⁶ - 1.0 × 10 ¹⁷ / cm ³ → The pinning effect was exerted, but a large amount of crystal grains were observed to be coarse. The reduction in mechanical strength before and after firing is up to 60%.

Therefore, the combination of the size of the precipitate of 0.5 to 20 nm and the number density of precipitates (A) of 1.0 × 10 ¹⁸ to 1.0 × 10 ¹⁹ /cm ³ can maximize the pinning effect.

According to the above theoretical investigation and experimental results, the relationship between the size of the precipitate and the number density and mechanical strength is shown in Table 1.

(as the persistence of pinned inclusions)

If the inclusions with the pinning effect are burnt out and decomposed, the effect will also be lost. The inclusions of organic compounds may decompose due to heating. However, the inorganic compound does not lose heat in the temperature range of 300 °C. In fact, the electrolytic copper alloy foil containing tungsten was WO ₃ before and after firing, and was not changed. Furthermore, the standard generating energy of the oxide of W is lower than that of Cu, so in the heating environment of 300 ° C, Cu does not take off the oxygen of WO ₃ . It is assumed that a ternary oxide such as CuWO ₄ is formed. However, the crystal structure of the above substance is different from Cu and does not exist in a solid solution, and therefore, the pinning effect continues.

(Effect of this embodiment)

Since the electrolytic copper foil according to the present embodiment has inclusions in the crystal grains or grain boundaries of the copper, the mechanical strength in the normal state is high.

In the present embodiment, the electrolytic copper foil having inclusions of inorganic compounds in the crystal grains or at the grain boundaries of the copper is subjected to heat treatment at 300 ° C, and the inclusions are not pyrolyzed, and the crystal grains are prevented from being coarsened. The tensile strength value after heat treatment at 300 ° C is high.

(better embodiment)

A preferred embodiment of the present invention is an electrolytic copper foil containing tungsten and the remainder being composed of copper and unavoidable impurities.

Here, the inclusion of tungsten means that fine particles or ultrafine particles as tungsten oxide are dispersed in the base material.

The content of tungsten in the electrolytic copper foil is preferably in the range of 10 to 2610 ppm, more preferably in the range of 280 to 2460 ppm. Here, the tungsten content in the electrolytic copper foil means that the tungsten component contained as the fine particles or ultrafine particles of the tungsten oxide is converted into the content of the metal tungsten. If the tungsten content is too small, the effect of addition is substantially not apparent. On the other hand, if the amount of addition of tungsten is too large, the effect of addition is saturated, and although the cost is high, the effect of improving physical properties is not obtained.

That is, the mechanical strength of the electrolytic copper foil having a tungsten content of less than 10 ppm after heating at 300 ° C for 1 hour is almost the same as that of the case where tungsten is not contained.

As the amount of tungsten added increases, the decrease in strength after heating at 300 ° C × 1 H becomes small, but if the content is increased to a certain extent, the effect becomes saturated.

In addition, the unit "ppm" for indicating the content of the component means "mg/kg". In addition, 0.0001 mass% = 1 ppm.

The electrodeposited copper foil of the preferred embodiment can be obtained by electrolyzing a copper sulfate-based electrolyte solution containing copper ions and tungsten oxide formed from a tungsten salt at pH 4 or lower at pH 4 or lower.

The tungsten salt contained in the electrolytic solution may be dissolved in a sulfuric acid-copper sulfate solution, and examples thereof include sodium tungstate, ammonium tungstate, and potassium tungstate.

In the electrolytic solution of the preferred embodiment, the electrolytic copper foil is electrically analyzed in the electrolyte having a low chloride ion concentration, and the tungsten oxide formed by the tungsten salt in the electrolyte having a pH of 4 or less is electrically analyzed. It is taken up in an electrolytic copper foil as a tungsten oxide (mainly WO ₃ and a part of W ₂ O ₅ , possibly including WO ₂ ). Here, the tungsten oxides are dispersed as fine particles or ultrafine particles in copper as a base material.

That is, the electrodeposited copper foil of the preferred embodiment is formed by electrolysis from a sulfuric acid-copper sulfate electrolyte having a low chloride ion concentration and an electrolyte containing tungsten oxide. It is generally believed that in the sulfuric acid-copper sulfate electrolyte containing tungsten oxide, the tungsten oxide is passed from the tungsten salt to the tungstate ion (WO ₄ ^2- or WO ₅ ^{2- ,} etc.), and finally formed into fine particles or ultrafine particles. .

When electrolytic copper is electrolyzed by a tungsten oxide-containing sulfuric acid-copper sulfate electrolyte having a low chloride ion concentration to form an electrolytic copper foil, fine particles or ultrafine particles of tungsten oxide are adsorbed to the grain boundary, and the crystal nucleus The growth is suppressed, the crystal grains become fine, and an electrolytic copper foil having a large mechanical strength in a normal state is formed.

The fine particles or ultrafine particles of the tungsten oxide present in the electrolytic copper foil are not combined with or absorbed by the internal copper crystals, and are retained as fine particles or ultrafine particles of tungsten oxide.

Even if the electrolytic copper foil containing tungsten oxide is heated at a high temperature of about 300 ° C, the tungsten oxide can prevent the fine crystals of copper from being recrystallized by heat to cause coarsening of crystal grains.

Therefore, the electrodeposited copper foil of the preferred embodiment has an excellent characteristic that the electrolytic copper foil produced by using the sulfuric acid-copper sulfate electrolyte containing an organic additive does not have the mechanical strength of the normal state, and is about 300 ° C. The decrease in mechanical strength after heating at a high temperature is also small.

Copper was electrolyzed from a sulfuric acid-copper sulfate-based electrolytic solution on a rotating titanium drum, and after peeling off, the copper was continuously wound up to produce an electrolytic copper foil. The surface of the copper foil in contact with the electrolyte is called a rough surface, and the surface in contact with the titanium roller is called a glossy surface.

The rough surface roughness of the electrolytic copper foil according to the preferred embodiment varies depending on the application, but is preferably Rz ≦ 2.5 μm. The shiny surface is a replica of the titanium roller, Rz=0.5~3.0μm. In addition, Rz here means Rz (10-point average roughness) measured by the implementation of JISB0601-1994.

It is considered that when an organic compound is used as an inclusion, the organic additive added to the sulfuric acid-copper sulfate electrolyte solution forms a compound together with copper and chlorine in the electrolytic solution. When copper is electrolyzed by the electrolytic solution to form an electrolytic copper foil, the copper-organic additive-chlorine compound is adsorbed to the inside of the crystal grain or the grain boundary, and the growth of the crystal nucleus is suppressed, and the crystal grains become fine. An electrolytic copper foil having a large mechanical strength in a normal state is formed.

However, it is generally believed that the inclusions contained in the electrolytic copper foil are copper-organic additives-chlorine compounds, so copper will be combined with or absorbed by the internal copper crystals, and the substances present in the electrolytic copper foil will only leave organic additives. And chlorine, these organic additives and chlorine will decompose when exposed to high temperatures of about 300 ° C, resulting in a decrease in mechanical strength.

It is considered that the reason why the tensile strength is lowered after heating at a high temperature of about 300 ° C is that the inclusion compound existing in the grain boundary as described above is an organic compound, and the organic compound is liable to be decomposed by heating at about 300 ° C. Therefore, the mechanical strength will decrease.

On the other hand, the electrolytic copper foil of the preferred embodiment is an electrolytic copper foil formed by electrolytically analyzing an electrolytic solution containing tungsten oxide from a sulfuric acid-copper sulfate electrolyte having a low chloride ion concentration.

The tungsten component passes through a tungstate ion (WO ₄ ^2- or WO ₅ ^{2- ,} etc.) in a sulfuric acid-copper sulfate electrolyte to form a tungsten oxide (mainly WO ₃ , a part of W ₂ O ₅ , possibly including WO ₂ ) The particles or ultrafine particles continue to exist in the electrolytic copper foil in the form of fine particles or ultrafine particles. As a result, the growth of the crystal nucleus of copper can be suppressed, and the crystal grains of copper become fine, and the electrolytic copper foil having a large mechanical strength in a normal state can be obtained.

Therefore, it is generally considered that the electrolytic copper foil of the preferred embodiment uses fine particles or ultrafine particles of tungsten oxide as inclusions, and unlike the copper-organic additive-chlorine compound, tungsten does not combine or be absorbed by internal copper crystals. Rather, it continues to exist as fine particles or ultrafine particles of tungsten oxide in the interior or grain boundaries of the grains.

Therefore, even if exposed to a high temperature of about 300 ° C, the tungsten oxide particles or ultrafine particles will remain in the grain or in the grain boundary, preventing the fine crystallization of copper from recrystallization due to heat, making the crystal coarse. .

Therefore, in the preferred embodiment, the mechanical strength is large under normal conditions, and the mechanical strength is reduced even after heating at a high temperature of about 300 ° C, and is superior to the electrolytic copper foil using an organic compound as an inclusion. .

(Use of electrolytic copper foil)

The electrodeposited copper foil of the present invention can be suitably used for various applications such as a flexible printed wiring board (FPC) and a negative electrode current collector for a lithium ion secondary battery.

As described above, it is required to have a low thickness for the FPC, and it is necessary to have a strength of a certain value or more after pouring or heat laminating the polyimide.

Further, when it is used for a negative electrode current collector for a lithium ion secondary battery, when polyimide is used as a binder, the negative electrode is subjected to heat treatment in order to harden the polyimide. After heating, the copper foil softens, and if the hardness becomes too small, the active material is charged and discharged. The expansion and contraction stress is applied to the copper foil, sometimes causing the copper foil to deform. In more serious cases, the copper foil may break. Therefore, the copper foil for a negative electrode collector must have a certain value or more after heating.

As described above, in either of the flexible printed wiring board (FPC) and the negative electrode current collector for a lithium ion secondary battery, in order to achieve the heating effect of the polyimide, it is necessary to heat at a temperature of about 300 °C. Therefore, after the copper foil is heated at a temperature of about 300 ° C × 1 H, it is necessary to have a strength of a certain value or more.

In the electrolytic copper foil of the present invention, the criteria for the level of conformity of these mechanical properties are expressed as follows for each item. The tensile strength under normal conditions is TS ≧ 500 MPa, the 0.2% proof stress is YS ≧ 300 MPa, and the elongation is El ≧ 2%. The tensile strength after heating at 180 ° C was TS ≧ 310 MPa, the 0.2% proof stress was YS ≧ 200 MPa, and the elongation was El ≧ 1.5%. The tensile strength after heating at 300 ° C × 1 H was TS ≧ 280 MPa, the 0.2% proof stress was YS ≧ 150 MPa, and the elongation was El ≧ 2.5%. Further, the ratio of the tensile strength after heating at 300 ° C × 1 H to the tensile strength under normal conditions was 60% or more.

Example

Hereinafter, the present invention will be specifically described using examples and comparative examples, but the present invention is not limited thereto.

[Example 1: No organic additive]

As the sulfuric acid-copper sulfate electrolyte, the following bath was used as the basic bath composition.

Cu=50~150g/L

H ₂ SO ₄ =20~200g/L

As the additive A1, sodium tungstate was dissolved in the following amount to prepare an aqueous solution, and this aqueous solution was added to the electrolytic solution of the above basic bath to obtain an electrolytic solution 1.

Sodium tungstate = 1mg/L~500mg/L (converted to tungsten)

In addition, the above amount means "sodium tungstate equivalent to the amount of tungsten metal of 1 mg/L to 500 mg/L" (the same applies hereinafter).

In Table 2, which will be described later, as the above-mentioned Example 1, when sodium tungstate as the additive A1 is added in the following seven levels, the results are shown in Examples 1-1 to 1-7.

Example 1-1 sodium tungstate = 260 mg / L (converted to tungsten)

Example 1-2 sodium tungstate = 150 mg / L (converted to tungsten)

Example 1-3 sodium tungstate = 100 mg / L (converted to tungsten)

Example 1-4 sodium tungstate = 50 mg / L (converted to tungsten)

Example 1-5 sodium tungstate = 30 mg / L (converted to tungsten)

Example 1-6 sodium tungstate = 20 mg / L (converted to tungsten)

Example 1-7 Sodium tungstate = 10 mg / L (converted to tungsten)

The chloride ion concentration was 0 mg/L (no addition at all).

Using any of the electrolytic solutions 1 having different tungsten concentrations, electrodeposition was carried out under the following conditions to produce a tungsten-containing electrolytic copper foil having a thickness of 12 μm.

Current density = 30~100AA/dm ²

Temperature = 30~70°C

The surface roughness of the rough surface (M surface) was measured for each of the obtained electrolytic copper foils; the tensile strength (TS), 0.2% proof stress (YS) and elongation (El) under normal conditions were 180 ° C. ×1 H tensile strength after heating, 0.2% proof stress and elongation, tensile strength after heating at 300 ° C × 1 H, 0.2% endurance and elongation; and W content in copper foil. These results are shown in Table 2.

Here, the surface roughness of the rough surface (M surface) is measured in accordance with JIS B0601-1994, and is expressed as Ra (arithmetic mean roughness) and Rz (ten point average thickness).

Further, tensile strength, 0.2% proof stress, and elongation (elongation at break) were measured in accordance with JIS Z2241-1880.

Regarding the W content in the copper foil, an electrolytic copper alloy foil of a certain mass was dissolved with an acid, and then W in the solution was analyzed by ICP emission spectroscopy to calculate the amount of W contained in the electrolytic copper alloy foil. The results are shown in Table 2 as the W content (ppm).

Regarding the criteria for the acceptable level of mechanical properties of the copper foil of the present embodiment, each measurement item is as follows. The rough surface roughness (M surface roughness) was Ra ≦ 0.5 μm and Rz ≦ 2.5 μm. The tensile strength under normal conditions is TS ≧ 500 MPa, the 0.2% proof stress is YS ≧ 300 MPa, and the elongation is El ≧ 2%. The tensile strength after heating at 180 ° C was TS ≧ 310 MPa, the 0.2% proof stress was YS ≧ 200 MPa, and the elongation was El ≧ 1.5%. The tensile strength after heating at 300 ° C × 1 H was TS ≧ 280 MPa, the 0.2% proof stress was YS ≧ 150 MPa, and the elongation was El ≧ 2.5%. Further, the ratio (%) of the tensile strength after heating at 300 ° C × 1 H to the tensile strength under normal conditions was 50% or more.

[Example 2: Ammonium tungstate]

As the sulfuric acid-copper sulfate electrolyte, the following bath was used as the basic bath composition.

Cu=80~120g/L

H ₂ SO ₄ =80~120g/L

As the additive A2, ammonium tungstate was dissolved in the following addition amount to prepare an aqueous solution, and this aqueous solution was added to the electrolytic solution of the above basic bath to obtain an electrolytic solution 2.

Example 2 Ammonium Tungstate = 150 mg / L (converted to tungsten)

The chloride ion concentration was 0 mg/L (no addition at all).

Using this electrolytic solution 2, electrolysis was carried out under the following conditions to produce a tungsten-containing electrolytic copper foil having a thickness of 12 μm.

Current density = 50~100AA/dm ²

Temperature = 50~70°C

The surface roughness of the rough surface (M surface) was measured for the obtained electrolytic copper foil; the tensile strength, the 0.2% proof stress and the elongation under normal conditions, and the tensile strength after heating at 180 ° C × 1 H, 0.2% endurance and elongation, tensile strength, 0.2% endurance and elongation after heating at 300 ° C × 1 H; and W content. These results are shown in Table 2.

[Example 3: Potassium tungstate]

As the sulfuric acid-copper sulfate electrolyte, the following bath was used as the basic bath composition.

Cu=80~120g/L

H ₂ SO ₄ =80~120g/L

As the additive A3, potassium tungstate was dissolved in the following addition amount to prepare an aqueous solution, and this aqueous solution was added to the electrolytic solution of the above basic bath to obtain an electrolytic solution 3.

Example 3 Potassium Tungstate = 150 mg / L (converted to tungsten)

The chloride ion concentration was 0 mg/L (no addition at all).

Using this electrolytic solution 3, electrolysis was carried out under the following conditions to produce a tungsten-containing electrolytic copper foil having a thickness of 12 μm.

Current density = 50~100A/dm ²

Temperature = 50~70°C

The surface roughness of the rough surface (M surface) was measured for the obtained electrolytic copper foil; the tensile strength, the 0.2% proof stress and the elongation under normal conditions, and the tensile strength after heating at 180 ° C × 1 H, 0.2% endurance and elongation, tensile strength, 0.2% endurance and elongation after heating at 300 ° C × 1 H; and W content. These results are shown in Table 2.

[Comparative Example-1]

In the same manner as in Example 1, except that the amount of W added was changed to a low concentration and sodium tungstate = 3 mg/L (in terms of tungsten), an electrolytic copper foil having a thickness of 12 μm and a W content of 5 ppm was produced.

The surface roughness of the rough surface (M surface) was measured for the obtained electrolytic copper foil; the tensile strength, the 0.2% proof stress and the elongation under normal conditions, and the tensile strength after heating at 180 ° C × 1 H, 0.2% endurance and elongation, tensile strength, 0.2% endurance and elongation after heating at 300 ° C × 1 H; and W content. These results are shown in Table 2. In addition, the table shows the tensile strength as the tensile strength.

[Comparative Example 2]

As the sulfuric acid-copper sulfate-based electrolyte, the following bath was used as the basic bath composition, and no additive was added.

Cu=80~120g/L

H ₂ SO ₄ =80~120g/L

Using this electrolytic solution, electrolysis was carried out under the following conditions to produce an electrolytic copper foil having a thickness of 12 μm.

Current density = 50~100A/dm ²

Temperature = 50~70°C

The surface roughness of the rough surface (M surface) was measured for the obtained electrolytic copper foil; the tensile strength, the 0.2% proof stress and the elongation under normal conditions, and the tensile strength after heating at 80 ° C × 1 H, 0.2% endurance and elongation, tensile strength, 0.2% endurance and elongation after heating at 300 ° C × 1 H; and W content. These results are shown in Table 2.

[Comparative Example 3]

As the sulfuric acid-copper sulfate electrolyte, the following bath was used as the basic bath composition.

Cu=80~120g/L

H ₂ SO ₄ =80~120g/L

An electrolytic solution was obtained by adding sodium tungstate as the additive A1 and hydrochloric acid as the additive B to the basic bath in the following amounts.

Sodium tungstate = 10mg/L~100mg/L (converted to tungsten)

Chloride ion (CL ^- ) = 20mg / L ~ 100mg / L

Using this electrolytic solution, electrolysis was carried out under the following conditions to produce an electrolytic copper foil having a thickness of 12 μm.

Current density = 50~100A/dm ²

Temperature = 50~70°C

The surface roughness of the rough surface (M surface) was measured for the obtained electrolytic copper foil; the tensile strength, the 0.2% proof stress and the elongation under normal conditions, and the tensile strength after heating at 180 ° C × 1 H, 0.2% endurance and elongation, tensile strength, 0.2% endurance and elongation after heating at 300 ° C × 1 H; and W content. These results are shown in Table 2.

[Comparative Example 4]

As the sulfuric acid-copper sulfate electrolyte, the following bath was used as the basic bath composition.

Cu=80~120g/L

H ₂ SO ₄ =80~120g/L

An electrolytic solution was obtained by adding sodium tungstate as the additive A1, hydrochloric acid as the additive B, and the gel as the additive C to the basic bath in the following amounts.

Sodium tungstate = 10mg/L~100mg/L (converted to tungsten)

Chloride ion (CL ^- ) = 20mg / L ~ 100mg / L

Glue = 2~10mg/L

Using this electrolytic solution, electrolysis was carried out under the following conditions to produce an electrolytic copper foil having a thickness of 12 μm.

Current density = 50~100AA/dm ²

Temperature = 50~70°C

The surface roughness of the rough surface (M surface) was measured for the obtained electrolytic copper foil; the tensile strength, the 0.2% proof stress and the elongation under normal conditions, and the tensile strength after heating at 180 ° C × 1 H, 0.2% endurance and elongation, tensile strength, 0.2% endurance and elongation after heating at 300 ° C × 1 H; and W content. These results are shown in Table 2.

The surface roughness of the tungsten-containing electrolytic copper foil of Examples 1-1 to 1-7 and Example 2 and Example 3 is very small, and the mechanical strength under normal conditions is large, after heating at 180 ° C × 1 H and after 300 ° C The decrease in mechanical strength after heating of ×1 H is small, for example, the tensile strength is maintained at a value of 300 MPa or more.

Further, when the tungsten content is changed to 500 ppm or less, there is a tendency that the mechanical strength is proportionally decreased as the content becomes small, and the embodiment 1-7 can also be used. It is clear that when the tungsten content is 10 ppm or more, for example, the tensile strength in a normal state is 500 MPa or more.

The electrolytic copper foil containing 5 ppm of tungsten of Comparative Example 1 and the electrolytic copper foil of Comparative Example 2 completely free of tungsten were substantially the same. If the tungsten content is too small, the effect of adding tungsten is low, and as a result, mechanical properties are inferior to the examples.

In Comparative Example 3, an electrolytic copper foil obtained by adding tungsten and a chloride ion of more than 3 mg/L to the electrolytic solution was insufficient in mechanical strength under normal conditions, and the mechanical strength was lowered after heating at 300 ° C × 1 H. Further, the amount of W in the copper foil was measured, and as a result, the lower limit (1 ppm (=0.0001 mass%)) or less was detected.

From this, it is understood that if chloride ions are contained in the electrolytic solution, precipitation of tungsten is suppressed.

Comparative Example 4 was produced based on Patent Document 1 (Japanese Patent No. 3238278), and was prepared by adding a gel to the electrolytic solution of Comparative Example 3.

The thickness of the rough surface of the electrolytic copper foil is large, and the mechanical strength under normal conditions is also small, and the mechanical strength is lowered after heating at 300 ° C × 1 H. Further, the amount of W in the copper foil was measured, and as a result, the detection limit was equal to or less.

When the electrolyte contains more than 3 mg/L of chloride ions, it suppresses the electrical analysis of a metal such as tungsten which is difficult to form an alloy with copper. For example, it is confirmed from the effect of addition of an organic additive such as a rubber, and the rough surface roughness is large. Electrolytic copper foil, but does not form an electrolytic copper alloy foil.

As described above, the inventors confirmed in the research conducted for realizing the present invention that the tungsten oxide produced from the tungsten salt is present in the sulfuric acid-copper sulfate electrolyte and contains chlorine at a concentration higher than 3 mg/L. In the case of a compound ion, tungsten is not eutectoid in the electrolyzed copper.

[Examples 11 to 21: Use of W, Mo, Ti, Te]

In Examples 11 to 21 and Comparative Example 11, as the sulfuric acid-copper sulfate-based electrolytic solution, the following bath was used as the basic bath composition.

Cu=80~120g/L

H ₂ SO ₄ =80~120g/L

An aqueous solution obtained by dissolving various metal salt compounds (various metal sources) and sodium chloride (chloride ion source) described in Table 3 as an additive was added to the basic bath, and the concentration of the metal salt described in Table 3 was adjusted. The chloride ion concentration was obtained to obtain an electrolyte.

Electrolytic analysis was carried out using any of the various electrolytic solutions under the following conditions to produce electrolytic copper foil having a thickness of 12 μm.

Current density = 50~100A/dm ²

Temperature = 50~70°C

Comparative Example 12 was prepared as follows based on Patent Document 2 (Japanese Patent Laid-Open Publication No. 2000-17476). Will contain CuSO ₄ . The electrolytes of 5H ₂ O, H ₂ SO ₄ and SnSO _{4 were} subjected to bubbling treatment in air, and were prepared by CuSO ₄ . 5H ₂ O=250g/L, H ₂ SO ₄ =50g/L, SnO ₂ fine particles or ultrafine particles=3g/L, SnSO ₄ =10g/L, polyethylene glycol as polyether=0.001~0.1g/ The electrolyte composed of L. Using this electrolytic solution, electrolysis was carried out under the conditions of a current density = 10 A/dm ² and a bath temperature = 50 ° C to produce an electrolytic copper foil having a thickness of 12 μm.

Comparative Example 13 was prepared as follows based on Patent Document 3 (Japanese Patent No. 3943214). An electrolyte solution obtained by adding 50 ppm of silver ions to a sulfuric acid acidic copper sulfate solution having a copper ion concentration of 70 to 120 g/L and a sulfate ion concentration of 50 to 120 g/L. Using this electrolytic solution, electrolysis was carried out under the conditions of a current density of 120 A/dm ² and an electrolyte temperature of 57 ° C to produce an electrolytic copper foil having a thickness of 12 μm.

As a reference example, a commercially available Cu-0.015-0.03 Zr rolled copper alloy foil (trade name: HCL-02Z, manufactured by Hitachi Cable Co., Ltd.) having a thickness of 12 μm was used.

With respect to the obtained electrodeposited copper foil of each of the examples and the comparative examples and the rolled copper alloy foil of the reference example, the tensile strength (TS) in the normal state and the tensile strength after heating at 300 ° C × 1 H were measured as follows. , the ratio, conductivity (EC), chlorine content, and metal content.

The tensile strength was measured in accordance with JIS Z2241-1880. When the value of the tensile strength of the copper foil in the normal state is 500 MPa or more, it is judged to be good, and when it is less than 500 MPa, it is judged to be bad. Further, in a more ideal condition, the ratio of the tensile strength of the copper foil after heat treatment at 300 ° C for 1 hour (300 ° C × 1 H) to the value of the tensile strength under normal conditions is 80. When it is more than %, it is judged to be good, and when it is less than 80%, it is judged to be bad.

The conductivity was measured by a 4-terminal method (current-voltage method) in accordance with JIS K6271. When the conductivity of the copper foil was 65% IACS or more, it was judged to be excellent, and when it was 50% IACS or more, it was judged to be good, and when it was less than 50% IACS, it was judged to be bad.

Regarding the content of metal such as W in the copper foil and Cl, the electrolytic copper foil of a certain mass is dissolved with an acid, and the amount of metal such as W in the obtained solution is calculated by ICP emission spectrometry. Further, the content of chlorine in the obtained solution was determined by a silver chloride titration method (detection limit: 1 ppm).

These results are shown in Table 3.

As the metal oxide, Examples 11 to 17 were oxide fine particles or ultrafine particles of tungsten (W), Examples 18 and 21 were oxide fine particles or ultrafine particles of Mo (Mo), and Example 19 was titanium (Ti). In the example 20, the oxide fine particles or the ultrafine particles of cerium (Te) were respectively taken up into the electrolytic copper foil, and the content thereof was in the range of 10 to 2610 ppm in terms of each metal. Therefore, it has a normal tensile strength of up to 500 MPa or more, and the maintenance strength of the tensile strength after heating by 300 ° C × 1 H is also 50% or more. The electrical conductivity is also 55% or more.

In particular, the metal element contents of Examples 11 to 14, 18, 19, and 20 were in the range of 100 to 2,500 ppm. Therefore, it has a normal tensile strength of up to 500 MPa or more, and the maintenance strength of the tensile strength after heating by 300 ° C × 1 H is also more than 80%. The conductivity is also as high as 65% or more.

In particular, in Examples 11 to 14, 17 containing tungsten, the tungsten content is 280 to 2,460 ppm, and the tensile strength is as high as 600 MPa or more, and the tensile strength after heating at 300 ° C × 1 H is also maintained. More than 80%. The conductivity is also as high as 65% or more. The same applies to Examples 1-1 to 1-5, 2, and 3.

Example 16 only ingested less than 100 ppm of tungsten oxide fine particles or ultrafine particles, and Example 21 ingested only less than 100 ppm of molybdenum oxide fine particles or ultrafine particles, which was low in content. Therefore, although the tensile strength under normal conditions is sufficiently high, the tensile strength after heating at 300 ° C × 1 H is lowered.

In Example 15, the intake amount of tungsten oxide fine particles or ultrafine particles exceeded 2,500 ppm. Therefore, although both tensile strength and heat resistance are improved, the electrical conductivity is less than 65%.

In Example 17, the chloride ion content in the electrolytic solution was 3 ppm. No chlorine was detected in the electrolytic copper foil, but the results were not inferior to Examples 11 to 14.

Further, Example 13 is a test example in which the metal (W) content is different from that of the above Example 1-1. It is generally believed that the effect of inclusions is saturated due to the high metal content, and the experimental results are the same in the two test cases.

Further, in the SIMS (Secondary Ion Mass Spectrometry) analysis, the chlorine content of the electrolytic copper foil was measured. The measurement conditions for SIMS analysis are: primary ions: Cs ⁺ (5kV, 100nA), secondary (detection) ions: copper (Cu) ⁶³ Cu-. Chlorine (Cl) ³⁵ Cl-, sputtering zone: 200 μm × 400 μm. Since the surface of the electrolytic copper foil was affected by the dirt and the oxide film, sputtering and removal were performed from the surface to the depth direction of 2 μm, and measurement was started, and the analysis was performed at a depth of 4 μm. The intensity ratio was calculated from the average of the intensities of the respective measured elements and the copper strength, and compared with the standard sample, and it was confirmed that the chlorine content in the electrolytic copper foil of each example was less than 1 ppm. It is generally estimated that the amount of tungsten increases due to the low chlorine content, which plays a role in improving heat resistance.

In Comparative Example 11, the electrolytic copper foil contained 2 ppm of chlorine. Therefore, the content of the oxide fine particles or the ultrafine particles of tungsten (W) in the electrolytic copper foil is small, and the tensile strength is also low as compared with Examples 11 to 21.

In Comparative Example 12, the electrolytic copper foil contained 6 ppm of chlorine. Therefore, tungsten (W) was not detected in the electrolytic copper foil. The tensile strength was also lower than those of Examples 11 to 21.

Comparative Example 13 is a test example produced based on Patent Document 2 (Japanese Patent Laid-Open Publication No. 2000-17476). Cu-Sn is also known as a rolled alloy. Even if the electrolytic copper foil of Comparative Example 13 is compared with the Cu-Sn rolled alloy, various characteristic values and manufacturing costs are not advantageous. Further, in the sulfuric acid acidic electrolyte, tin oxide (SnSO ₄ ) which is not an oxide is forcibly oxidized into SnO ₂ fine particles or ultrafine particles by oxygen bubbling, so that it is not only costly in production but also generated in the electrolytic solution. The oxide in the copper foil is more than 20 nm, and the particle diameter is larger than that of tungsten or the like, so the conductivity is also low.

Comparative Example 14 is a test example produced based on Patent Document 3 (Japanese Patent No. 3943214). In the electrolytic copper foil of Comparative Example 14, after Ag and Cu were solid-solved, they were taken in as metal Ag. Therefore, the ratio of the tensile strength after heating at 300 ° C × 1 H to the tensile strength under normal conditions is compared with the embodiment of the present invention in which the metal is taken up as fine particles or ultrafine particles of the oxide to enhance precipitation. (%) is poor.

The reference example is Cu-0.015~0.03 Zr rolled copper alloy foil. From this, it is understood that the electrolytic copper foil of the present invention has mechanical properties and electrical conductivity equal to or higher than those of the rolled copper alloy foil.

[Examples 31 to 38: Use of thiourea organic matter]

In Examples 31 to 38, as the sulfuric acid-copper sulfate-based electrolytic solution, the following bath was used as the basic bath composition.

CuSO ₄ =200~500g/L

H ₂ SO ₄ =80~120g/L

NaCl=0~55mg/L

An aqueous solution obtained by dissolving various metal salt compounds (various metal sources) and organic components described in Table 3 as an additive was added to the base bath, and the metal salt concentration and the organic substance concentration described in Table 3 were adjusted to obtain an electrolytic solution. Further, the concentration of the metal salt compound means the concentration contained as a metal.

Electrolytic analysis was carried out using any of the various electrolytic solutions under the following conditions to produce electrolytic copper foil having a thickness of 12 μm.

Current density = 30~100AA/dm ²

Temperature = 30~75°C

The tensile strength (TS) in the normal state of the obtained electrolytic copper foil of each of the obtained examples was measured in the same manner as in the other examples, and the tensile strength measured at room temperature after heating at 300 ° C × 1 H, and the like. Ratio, and metal content. These results are shown in Table 3.

In Examples 31 to 35, only the organic component was added. In Examples 31 to 35, the electrolytic copper foil does not contain a metal, but contains an organic component as an inclusion, so that it has a high tensile strength of more than 700 MPa in a normal state. However, since the inclusions are organic components, Therefore, compared with Examples 36 to 38 containing metal fine particles, the tensile strength retention rate measured at room temperature after heating at 300 ° C for 1 hour was low.

In Examples 36 to 38, both a metal salt compound and an organic component were added. In Examples 36 to 38, the electrolytic copper foil contained 98 to 280 ppm of metal and had inclusions having a particle diameter of 5.8 to 6.1, so that it had a high tensile strength of more than 700 MPa in a normal state. Further, since the inclusions were metal oxides, the tensile strength retention rate measured at room temperature after heating at 300 ° C for 1 hour was high.

Example 38 only ingested less than 100 ppm of tungsten oxide fine particles or ultrafine particles, which was low in content. Therefore, although the tensile strength under normal conditions is sufficiently high, the tensile strength measured at room temperature after heating at 300 ° C × 1 H is lowered.

Further, according to the measurement results of the average particle diameter of the inclusions described later, in the examples in which only the metal salt compound was added, the average particle diameter of the inclusions was about 1 nm. However, in Examples 31 to 35, the inclusions derived from the organic component had an average particle diameter of more than 10 nm and a relatively large particle diameter. Further, in Examples 36 to 38, both metal oxide fine particles and the like and inclusions derived from the organic component were contained, and the average particle diameter was about 5 nm.

(SIM observation of the die)

Further, after observing the electrolytic copper foils of the respective examples by SIM (scanning ion microscopy), it was found that the average grain size of the crystal grains of copper in any of the electrolytic copper foils was 100 to 600 nm, and the shape of the crystal grains of the copper was substantially The spherical shape has an aspect ratio of the long axis to the short axis of about 0.5 to 2.0.

[TEM observation]

In order to confirm the inclusion of inclusions, a copper foil sample (Example 1-1) to which W was added was subjected to TEM (Transmission Electron Microscopy) observation. Further, in the case of producing a TEM sample, a FIB (Focused Ion Beam) method using an acceleration voltage of a Ga ion beam of 30 kV was used. Thereafter, in order to remove the damage of the sample surface by FIB, an Ar ion beam of 1 kV was irradiated for 30 minutes while cooling the surface of the sample with liquid nitrogen. The TEM observation results of the copper foil before the firing treatment are shown in Fig. 2 . Use the TOPCON system 002BF to shoot under-focus images. The focus value is changed from the positive focus position to -300 nm. If observed at the under-focus position, it is observed that the influence of the edge of the inclusions forms a Fresnel pattern, which emphasizes the inclusions. Since it is not a positive focus, the size of the inclusions observed is larger than its own size, and a large number of inclusions of several nm in size are observed. It is observed that the inclusions indicated by the arrows are relatively large.

Fig. 3 is a view showing a TEM image of a copper foil obtained by firing a copper foil according to Example 1-1 at 300 °C. An under-focus image of the same condition as in Figure 2. The inclusions were observed to be larger than the copper foil before firing. Observe that the inclusions shown by the arrows in the figure are relatively Big. Although it is generally considered that inclusions will agglomerate by firing, such large inclusions exert a stronger pinning effect, and thus it is expected to be a high-strength, high-resistance copper foil.

Figure 4 shows a high resolution STEM image. Here, the High Angle Annular Dark Field-Scanning Transmission Electron Microscopy (HAADF-STEM) image was obtained using the aberration correction STEM 2100F manufactured by JEOL Ltd. Inclusions formed by W atoms having different contrasts were observed in the Cu lattice image. Its size is 1~2nm.

Figure 5 shows a HAADF-STEM image of a copper foil containing both ethyl thiourea and tungsten. Here, inclusions were observed in the crystal grains of a size of several nm to 10 nm and at the crystal interface. The inclusions present at the crystal interface exert a pinning force to prevent the grains from becoming fat, and the inclusions located in the grains, even if they are crystallized by firing or the like, will exert a pinning force to prevent crystallization. Further hypertrophy.

Fig. 6 shows a TEM image of a copper foil containing no W, and no inclusions were observed. The multi-angle observation was carried out, and the inclusions of Figs. 2, 3, 4, and 5 were not observed. From this fact, it is understood that inclusions are successfully formed in the copper foil of the embodiment of the present invention by adding a metal such as W.

[Small angle X-ray scattering measurement]

The small-angle X-ray scattering system directly measures the size and shape of an object in the internal sample, the distribution of nanometer atoms, molecules, and fluctuations. By using this measurement method, the average particle diameter, size distribution, and number density of the microparticles shown in the TEM observation can be calculated.

SAXS was applied to a copper foil sample (Example 1-1) to which W was added, a copper foil sample to which Mo was added (Example 18), and a copper foil sample (Example 36) to which W and TU (thiourea) were added (Example 36) Small angle X-ray scattering, and USXS (ultra small angle X-ray scattering). In the SAXS (USAXS) measurement, the industry using Spring-8 (super photonring 8 GeV, high-intensity radiation device) was measured by the beam line BL19B2.

Fig. 7(a) is a schematic diagram showing the optical axis of the SAXS (USAXS) measurement. The incident X-rays 14 generated from the X-ray source 13 having the shutter 15 are irradiated to the sample 27 through the monochromator 17, the first pinhole 19, the second pinhole 21, and the third pinhole 25. The incident X-rays 14 that are illuminated from the sample 27 produce transmitted X-rays 29 that pass through the sample 27 and scattered X-rays 31 that are scattered by the sample 27. The detector 35 is disposed at the rear end of the optical axis to detect the transmitted X-rays 29 or the scattered X-rays 31.

When the scattered X-rays 31 are measured by the detector 35, as shown in FIG. 7(b), the incident X-rays 14 are irradiated to the sample 27 without passing through the attenuator 23, and the X-rays 29 are shielded and transmitted by the beam blocker 33, and are utilized. The detector 35 measures the scattered X-rays 31.

When the X-rays 29 are transmitted by the detector 35, as shown in FIG. 7(c), after the intensity of the incident X-rays 14 is weakened by the attenuator 23, the incident X-rays 14 are irradiated to the sample 27 without using the beam blocker 33. The shield transmits X-rays 29, and the transmitted X-rays 29 are measured by the detector 35.

The distance from the sample 27 to the detector 35 is set to L. The position at which the transmitted X-rays 29 passing through the sample 27 reach the detector 35 is set to 0, and similarly, the position at which the scattered X-rays 31 scattered from the sample 27 at the angle θ reaches the detector 35 is set to A. If AO = r, then tan θ = r / L, θ can be calculated. Then, the horizontal axis of the data of SAXS and USAXS is represented by the formula (4), and is denoted by q (nm ^-1 ).

q=4πsinθ/λ‧‧‧(4)

λ is the wavelength at which X-rays are incident. For the measurement, λ = 0.068 nm, and the distance from the sample to the detector L = 4.2 m (SAXS), L = 42 m (USAXS). The range of the measurement was q = 0.05 to 4 (nm ^-1 ). The detector uses a semiconductor two-dimensional detector PILATUS. After the SAXS measurement was performed, the intensity map of the two-dimensional X-rays was examined, and it was confirmed that there was no anisotropy, and then one-dimensionalization was performed. Fig. 8(a) is a view showing an electrolytic copper foil containing W, Fig. 8(b) is a view showing an electrolytic copper foil containing Mo, and Fig. 8(c) is an electrolytic copper containing W+TU (thiourea). In the figure of the foil, A in the figure indicates a copper foil after firing, and B in the figure indicates a copper foil before firing, and C in the figure indicates a pure copper foil. The vertical axis represents the intensity of X-rays, and the horizontal axis represents SAXS data as q. As can be seen from the figure, the pure copper foil is compared with the electrolytic copper foil, and the X-ray intensity is different between q=0.4 and 2. This indicates that inclusions of 10 nm or less were present in the electrolytic copper foil.

Regarding the electrolytic copper foil containing W, it is generally considered that the fine particles are WO ₃ as a result of TEM observation and XAFS measurement. Figure 9 is a subtraction of the SAXS intensity of a pure copper foil from the SAXS data of an electrolytic copper foil containing W, thereby extracting the X-ray scattering from WO ₃ . Further, in the figure, D represents pure copper before firing, and E in the figure indicates before firing, and F in the figure indicates pure copper. Using this extracted data, in order to calculate the number density of WO ₃ , the scattering cross-sectional area was calculated from the scattered X-rays, and fitting was performed. The measured X-ray scattering intensity I(q) has a relationship with the scattering cross-sectional area dΣ/dΩ(q) having the formula -(5).

Φ ₀ is the intensity of the straight beam, η is the correction term of the detector, S is the irradiation area, T is the transmittance, and D is the thickness. Basically, Φ ₀ , η, and S are constant values, so Φ ₀ ‧ η ‧ S = A = const is the device inherent value.

Regarding A, glassy carbon measured by a device having Φ ₀ , η , and S determined in advance was measured by SPring-8-BL19B2 to calculate A. The symbols S, C, and N of the formula - (5) are abbreviations of Sample, Cell, and Noise, respectively. In the present application, Sample is an electrolytic copper alloy foil, and Cell is a pure copper foil. The scatter cross-sectional area is calculated from the formula -(5) to obtain the formula -(6).

On the other hand, the cross-sectional area of the scattering is represented by the formula -(7).

dΣ/dΩ(q) is the scattering cross-sectional area, Δρ2 is the atomic scattering factor, dN is the particle number density, V is the particle volume, F is the particle shape factor, and N(r) is the particle size distribution function. According to the results of TEM observation, the shape factor of the particles is a sphere (formula-(8)).

The variable cross-sectional area d Σ / d Ω (q) calculated from the scattered X-ray intensity is fitted using the variable q and using the formula -(6). As a result, as shown in FIG. 10( a ), the inclusions contained in the electrodeposited copper foil containing W have an average particle diameter (radius) of about 0.8 nm and an average particle diameter (diameter) of about 1.6 nm. The distribution of the particles is centered on a radius of 0.8 nm, and the distribution (volume distribution f(R)) shown in Fig. 10(b) is taken. In addition, in the figure, D represents pure copper before firing, and G in the figure represents a spherical model.

The same measurement was carried out for each of the examples and the comparative examples, and the average particle diameter (diameter) of the inclusions contained in the electrolytic copper foil was measured.

Further, by the absolute value of the strength, it was found that the electrolytic copper foil of Example 1-1 containing about 1900 ppm had a number density of 3.0 × 10 ¹⁸ /cm ³ in the WO ₃ particles. From this fact, it was confirmed that inclusions having a desired size and a number of densities were successfully formed in the copper foil of the embodiment of the present invention by adding a metal such as W.

[XAFS measurement]

As one of the analysis methods using X-rays, XAFS (X-ray Absorption Fine Structure) is well known, that is, X-rays are irradiated to a sample while changing X-ray energy, according to the obtained X-rays. The absorption spectrum is used to analyze the chemical binding state and the electronic state in the sample. As a method for obtaining an X-ray absorption spectrum, there is a transmission method for calculating an X-ray absorption spectrum from an incident X-ray intensity and a transmitted X-ray intensity, and a fluorescence X-ray intensity generated from the sample as the X-ray absorption is performed. Fluorescent method.

When an additive element such as a metal material is used as an analysis target, the amount of addition is a small amount, and it is difficult to obtain an XAFS spectrum by a transmission method. At this time, the above-described fluorescent method is an effective method. The fluorimetry method is characterized in that XAFS measurement can be performed even with elements of a trace component by obtaining an X-ray irradiation area from the optical axis system.

The purpose of this measurement is to understand the chemical bonding state and electronic state of W and Mo in the high-strength copper foil. The W and Mo in the copper foil are trace amounts, and it is difficult to obtain the XAFS spectrum by the transmission method, so the fluorescence method is selected. In the measurement, the industry using the SPring-8 uses the beam line BL14B2. The measured X-ray energy range is 10000~10434eV and 19960~20600eV. In the former energy range, there is a L3-absorption end (10207 eV) of W, and a K-absorbing end of M (20000 eV) exists in the energy range of the latter.

A copper foil containing 2,500 ppm of W and 200 ppm of Mo was prepared in the same manner as in Example 11 except that 250 mg/L of tungstic acid (IV) sodium (in terms of metal) and 20 mg/L of sodium molybdate (IV) were used. It is used for the determination. Further, for comparison, W foil, WO ₃ , Mo foil, and MoO _{3 were prepared} . As a result, it was found that the state of W in the electrolytic copper foil was WO ₃ (Fig. 11 (a)). Further, Mo is in an oxidized state and is MoO ₃ (Fig. 11(b)). Further, in the figure, H denotes a W foil, and in the figure, I denotes WO ₃ , and in the figure, J denotes a copper foil, and in the figure, K denotes a Mo foil, and in the figure, L denotes MoO ₃ .

As described above, the electrolytic copper foil according to the examples contained particulate inclusions of WO ₃ or MoO _{3 having} an average particle diameter of 0.8 nm before the heat treatment at 300 ° C × 1 H.

Hereinabove, the preferred embodiments of the present invention have been described with reference to the drawings, but the present invention is not limited to the related examples. It is to be understood that those skilled in the art can devise various modifications and alterations within the scope of the technical scope of the present invention, and such modifications or modifications are of course also within the technical scope of the present invention.

1‧‧‧electrolytic copper foil

3‧‧‧ grain

5‧‧‧ inclusions

Claims (10)

An electrolytic copper foil characterized in that an inclusion having an average particle diameter of 0.5 to 100 nm is present in a grain boundary between copper crystal grains or copper crystal grains, and the inclusion contains an inorganic compound and/or an organic compound, and the inorganic substance The compound contains an oxide selected from the group consisting of one or more metal elements selected from the group consisting of tungsten, molybdenum, titanium, and niobium, and the organic compound contains a compound selected from the group consisting of thiourea, ethyl thiourea, tetramethyl thiourea, and 1,3- One or more thiourea organic compounds in the group consisting of dimethyl-2-thiourea and 1,3-diethyl-2-thiourea. The electrolytic copper foil according to claim 1, wherein the crystal grains have an average particle diameter of 100 to 600 nm. The electrolytic copper foil according to claim 1, wherein the inclusions have an average particle diameter of 0.5 to 50 nm. The electrolytic copper foil according to claim 3, wherein the inclusions have an average particle diameter of 0.5 to 20 nm. The electrolytic copper foil according to claim 1, wherein the inclusion contains an inorganic compound, and the content of the metal element in the electrolytic copper foil is 10 to 2610 ppm. The electrolytic copper foil according to claim 1, wherein the chlorine content in the electrolytic copper foil is less than 1 ppm. An electrode for a non-aqueous electrolyte secondary battery, comprising: a current collector comprising the electrolytic copper foil according to any one of claims 1 to 6; and an electrode active material formed on the surface of the current collector The electrode active material layer. A nonaqueous electrolyte secondary battery using the electrode for a nonaqueous electrolyte secondary battery according to claim 7. A method for producing an electrolytic copper foil, comprising adding an aqueous solution containing an inorganic compound and/or an aqueous solution containing an organic compound to a sulfuric acid-copper sulfate-based electrolytic solution containing sulfuric acid and copper sulfate, and performing electrolysis using the electrolytic solution. The aqueous solution containing the inorganic compound is an aqueous solution obtained by dissolving a salt of at least one metal element selected from the group consisting of tungsten, molybdenum, titanium, and niobium, and the aqueous solution containing the organic compound is produced. Containing one selected from the group consisting of thiourea, ethyl thiourea, tetramethyl thiourea, 1,3-dimethyl-2-thiourea, and 1,3-diethyl-2-thiourea An aqueous solution of the above thiourea organic compound. The method for producing an electrolytic copper foil according to claim 9, wherein the chloride ion concentration in the electrolyte solution is less than 3 mg/L.