JP2003193211A - Rolled copper foil for copper-clad laminate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide rolled copper foil which is used as copper foil most suitable for a flexible printed wiring board to be subjected to ultra-fine-pitch processing and by which smooth surface can be obtained when etching treatment for thickness reduction is applied. <P>SOLUTION: The rolled copper foil is recrystallized and temper-rolled copper foil in which the (200) plane diffraction intensity (I) determined by applying X-ray diffraction to the rolling surface of rolled copper foil of ≤20 μm thickness and the (200) plane diffraction intensity (I<SB>0</SB>) determined by applying X-ray diffraction to fine copper powder under the conditions identical with those for the rolled copper foil satisfy the relation of I/I<SB>0</SB>>50. The above recrystallized structure can be obtained by subjecting rolled copper foil having recrystallized structure of ≤20 μm grain size to finish rolling at ≥90% draft. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolled copper foil used as a conductive material for a flexible substrate which is subjected to extremely fine pitch processing. More specifically, the present invention relates to a recrystallized tempered or rolled finished rolled copper foil for a copper clad laminate of rolled copper foil.

[0002]

2. Description of the Related Art Printed wiring boards are often used in electronic circuits of electronic equipment. The printed wiring board is roughly classified into a hard laminated board (rigid board) and a flexible laminated board (flexible board) depending on the type of resin as a base material. Flexible substrates are used for wiring of movable parts because of their excellent flexibility, and are also used as space-saving wiring materials because they can be stored in a bent state in electronic equipment. In addition, since the substrate itself is thin, it can be used for semiconductor package interposers or liquid crystal displays (LC
It is also used as an IC tape carrier for D).

Polyimide is often used as the resin that is the base material of the flexible substrate to which the present invention relates, and copper is generally used as the conductive material from the viewpoint of conductivity. Flexible substrates include three-layer flexible substrates and two-layer flexible substrates due to their structure. The three-layer flexible substrate has a structure in which a resin film such as polyimide and a copper foil serving as a conductive material are bonded together with an adhesive such as epoxy resin or acrylic resin. On the other hand, the two-layer flexible substrate has a structure in which a resin such as polyimide and a copper foil which is a conductive material are directly bonded.

Copper foil is classified into electrolytic copper foil and rolled copper foil according to the manufacturing method. Electrolytic copper foil is manufactured by electrolytically depositing copper on a titanium or stainless steel drum from a copper sulfate plating bath, and rolled copper foil is manufactured by plastic working with rolling rolls. The present invention relates to the latter. After the foil is manufactured, on one surface of the copper foil, in order to improve the adhesiveness with the resin, Cu, Cu-N
A roughening treatment is performed to form particles of i, Cu-Co, etc. by electroplating. This is to improve adhesiveness by a so-called anchor effect, in which unevenness is formed on the surface of the copper foil and the copper foil is made to dig into the resin to obtain mechanical adhesive strength.

A printed wiring board is manufactured by etching a copper foil of a flexible substrate to form various wiring patterns, connecting electronic components with solder, and mounting them. In recent years, as electronic devices have become smaller, lighter, and more sophisticated, the demand for high-density mounting on printed wiring boards has increased, and the width and spacing of copper wiring have become smaller and smaller. In order to promote finer pitches for such copper wiring, it is essential to thin the copper foil. That is,
Conventionally, the thickness of copper foil used for flexible substrates is
18 μm or 12 μm was the mainstream, but it has come to be required for copper foil of 9 μm or thinner.

However, both the electrolytic copper foil and the rolled copper foil are
It is difficult to industrially manufacture a product having a thickness of 10 μm or less. This is because, for example, there is a problem that the frequency of holes (pinholes) penetrating the copper foil increases significantly when the thickness is 10 μm. Also, when the thickness of the copper foil is less than 10 μm, the copper foil and the resin film are bonded with an adhesive (three-layer substrate) or the resin layer is formed on the copper foil in the manufacturing process of the flexible substrate. (Two-layer substrate) is also difficult. This is because the thinner the copper foil is, the more easily the copper foil is deformed and wrinkles are generated on the copper foil, or the copper foil is cut, making it difficult to handle.

Therefore, for example, for a flexible substrate having a Cu circuit thickness of 9 μm, a flexible substrate using a copper foil of 18 μm or 12 μm is first manufactured, and the thickness of the copper foil is reduced to 9 μm by etching with an oxidizing acid. Often manufactured by the process of meat. In response to this etching process (hereinafter, referred to as “thinning etching”), it is required that the etching progresses uniformly on the surface of the copper foil. When the etching progresses unevenly, unevenness occurs on the surface after etching, and when the resist is applied to the copper foil surface prior to the etching of the circuit (hereinafter referred to as "circuit etching"), the gap between the copper foil and the resist film is increased. This is because bubbles are generated in the surface and the circuit shape after etching deteriorates.

On the other hand, in order to achieve a fine pitch, it is also desired that the surface roughness of the copper foil on the joint surface between the resin and the copper foil is small. This is because if the roughness of the copper foil is large, an etching residue will remain in the resin when the circuit is etched, and the linearity of the circuit after etching will decrease and the circuit width will become uneven. Furthermore, in electronic devices such as personal computers and mobile communications, the frequency of electrical signals has increased, but when the frequency of electrical signals exceeds 1 GHz, the effect of the skin effect, in which current flows only on the surface of the conductor, becomes noticeable. The effect that the current transmission path changes due to the unevenness of and the impedance increases cannot be ignored. From this point as well, it is desired that the surface roughness of the copper foil is small.

Since the surface of the electrolytic copper foil is formed by electrodeposited copper particles and the surface of the rolled copper foil is formed by contact with a rolling roll, the surface roughness of the rolled copper foil is smaller than that of the electrolytic copper foil. small. This difference in roughness remains even after the roughening process. In recent years, electrolytic copper foils with reduced surface roughness have also been developed, but the roughness of rolled copper foils has not yet been reached, and even if the roughness can be reduced on average, it is abnormal. The problem remains that a portion with a large roughness locally occurs due to electrodeposition. As described above, the rolled copper foil is more advantageous than the electrolytic copper foil in terms of surface roughness.

However, the rolled copper foil has a problem that in the thickness reduction etching, the etching progresses unevenly and large irregularities are generated on the surface after the etching. On the other hand, the surface unevenness of the electrolytic copper foil after the thinning etching is smaller than that of the rolled copper foil, which is practically no problem. For this reason, rolled copper foil has the advantage that it has a smaller surface roughness than electrolytic copper foil, but electrolytic copper foil was mainly used for the application of flexible substrates to which thinning etching treatment is applied.

[0011]

DISCLOSURE OF THE INVENTION The present invention provides a copper foil which is suitable for a flexible substrate which is subjected to extremely fine pitch processing, and which has a smooth surface when subjected to an etching treatment for thinning. Intended to provide foil.

[0012]

The inventors of the present invention have found that the unevenness produced when the surface of a rolled copper foil is subjected to thinning etching is caused by the following reasons. Rolled copper foil is composed of many crystal grains, and the crystal orientation differs depending on each crystal grain. Since the etching rate of copper changes depending on the crystal orientation, a step is created in each crystal grain. At the boundaries (grain boundaries) of each crystal grain, the arrangement of atoms is disturbed and the density of atoms is low, so the etching rate is higher than that in the crystal grains, and therefore a groove is formed at the grain boundaries. When a large inclusion (a phase different from copper) exists, the inclusion and copper have different etching rates, so that the inclusion remains unmelted to form a protrusion, or the inclusion melts before copper to form a recess. Or

Therefore, in order to reduce the surface unevenness, it is effective to align the crystal orientations of the respective crystal grains. Also, with respect to the grain boundaries between crystal grains having close orientations, the disorder of the atomic arrangement is small, so it is effective to align the crystal orientations. It is effective to prevent the formation of large inclusions.

It is known that when recrystallization annealing is performed on copper rolled with a high degree of workability, a cubic orientation develops as a recrystallization texture. The cubic orientation is the crystal <001>
The direction is parallel to the rolling direction, the rolling surface normal, and the width direction. In this case, the rolling surface (etching surface) is (1
The (00) plane is oriented. The abundance ratio of crystal grains having a cubic orientation increases as the cubic orientation develops, and when the cubic orientation is extremely developed, most of the crystal grains exhibit the cubic orientation. In this case, since the respective crystal grains are oriented in the same direction, the disorder of the atoms at the crystal grain boundaries becomes extremely small, and the texture structure appears as if it were a single crystal. In the present invention, attention was paid to the extreme development of the cubic orientation of the copper foil as a means for smoothing the surface after the thinning etching.

It is known that a copper foil having a developed cubic texture has excellent high cycle fatigue properties, and it has been proposed to use this kind of copper foil for a flexible substrate to which bending deformation is repeatedly applied ( Patent No. 3009383).
However, there has been no attempt to apply this type of copper foil to a flexible substrate that is subjected to extremely fine pitch circuit etching after thinning etching.

Furthermore, as a result of studying the relationship between the surface properties of the copper foil and the smoothness of the thinned etching surface, it was found that it is effective to disperse the starting points of corrosion on the surface. This measure was particularly effective when an etchant having a weak corrosive power was used.

When copper is cold-rolled, crack-like depressions may occur on the surface after rolling. This depression has a shape extending in a direction orthogonal to the rolling direction, and the free deformation of the copper surface due to the rolling oil film is involved in its formation, so it is sometimes called an oil pit. Conventionally, in the case of a flexible substrate, the presence of a dent tends to be disliked because the dent becomes a starting point of crack generation and reduces the flexibility (Japanese Patent Laid-Open No. 2001-58203). However, it has been clarified that, for thin-wall etching, this recess serves as the starting point of corrosion and smoothes the etched surface. The flexible substrate to which the present invention is applied is mainly of a type that is housed in an electronic device in a bent state and is not further bent and deformed. Even if bending deformation occurs, since the copper foil after the thickness reduction etching is very thin, the strain generated at the outer circumference of the bending portion is small, and thus sufficient bending property can be secured.

The present invention has been made based on the above findings. (1) Diffraction of (200) plane obtained by X-ray diffraction of a rolled surface of a rolled copper foil having a thickness of 20 μm or less. intensity (I) is a diffraction intensity of the fine powder of copper was determined by X-ray diffraction under the same conditions as rolled copper foil (200) plane (I ₀₎ to I /
A recrystallized tempered rolled copper foil excellent in uniform etching thinning property, characterized in that I ₀ > 50, (2) By rolling at a temperature higher than the semi-softening temperature by 50 ° C, / I ₀
> 50 (where I is the diffraction intensity of the (200) plane obtained by X-ray diffraction of the rolled surface of the rolled copper foil, and I ₀ is the fine copper powder under the same conditions as the rolled copper foil under X-rays). A rolled copper foil with a rolling finish characterized by being capable of inducing a recrystallized structure represented by (diffraction intensity of (200) plane obtained by diffracting), Is 20 μm
A rolled copper foil having the following recrystallized structure is formed by finish rolling with a workability of 90% or more.
(2) Rolled copper foil with a rolled thickness of 20 μm or less as described,
(4) Cu, Ag, O, H, and tough pitch copper whose total content of elements other than rare gas elements is 40 mass ppm or less
Recrystallization tempered or rolled rolled copper foil as described in (1), (2) or (3), (5) The total amount of elements other than Cu, Ag, O, H and rare gas elements is 20 mass ppm or less None (1), (2) or (3) recrystallized tempered or rolled finished rolled copper foil consisting of oxygen copper, (6) containing 100 to 700 mass ppm Ag, and C
The total amount of elements other than u, Ag, O, H and rare gas elements is 4
A recrystallized heat-treated or roll-finished rolled copper foil according to (1), (2), or (3), which is made of tough pitch copper having a content of 0 mass ppm or less. (7) Contains 100 to 700 mass ppm Ag, Cu, Ag, O,
The total amount of elements other than H and rare gas elements is 20 mass ppm
(1) consisting of oxygen-free copper which is, (2) or (3) recrystallized temper or rolled finish rolled copper foil, (8) rolled surface of rolled copper foil having a thickness of 20 μm or less X The diffraction intensity (I) of the (200) plane obtained by line diffraction is the diffraction intensity (I ₀ ) of the (200) plane obtained by X-ray diffraction of fine copper powder under the same conditions as the rolled copper foil. ), I / I ₀ > 50,
Furthermore, the angle between the [100] direction of the crystal and the rolling direction (θ)
Recrystallization tone with excellent uniform wall thickness reduction, characterized in that the ratio (α) of the crystals whose angle is within 10 ° (θ ≦ 10 °) to the total number of crystals is 60% or more (α ≧ 60%) Quality rolled copper foil, (9) I / I ₀ > 50 (where I means X-ray diffraction of the rolled surface of the rolled copper foil by annealing the rolled texture at a temperature 50 ° C higher than the semi-softening temperature. Is the diffraction intensity of the (200) plane, and I ₀ is the diffraction intensity of the (200) plane obtained by X-ray diffraction of fine copper powder under the same conditions as the rolled copper foil) and α ≧ 60% (where α is the crystal
The angle between the [100] direction and the rolling direction forms a recrystallized structure represented by the ratio of the crystals within 10 ° to the total number of crystals, and the rolled finished rolled copper foil, (1
0) Rolling processing structure, the crystal grain size is a rolled copper foil having a recrystallized structure of 20μm or less, is formed by finish rolling at a processing degree of 90% or more (9) thickness Is a rolled copper foil with a rolling finish of 20 μm or less, (11) where α is
80% or more (α ≧ 80%), recrystallized tempered or rolled finished rolled copper foil according to (8), (9) or (10), (12) Cu, Ag, O, H And tough pitch copper whose total content of elements other than rare gas elements is 30 mass ppm or less
(8), (9), (10) or (11) recrystallized temper or rolled finish rolled copper foil, (13) Cu, Ag, O, H and the total amount of elements other than rare gas elements is 20 mass ppm (8), (9), consisting of oxygen-free copper that is the following, (10) or (11) recrystallized temper or rolled finished rolled copper foil, (14) 100-700 mass ppm Ag
And tough pitch copper containing Cu, Ag, O, H and the total amount of elements other than rare gas elements is 40 mass ppm or less.
(8), (9), (10) or (11) recrystallized tempered or rolled finished rolled copper foil, (15) containing 100 to 700 mass ppm Ag, Cu, Ag, O, H and noble gases (8), (9), (1
0) or (11) recrystallized temper or rolled finished rolled copper foil, (16) crack-like depressions extending in the direction orthogonal to the rolling direction are dispersed on the surface, and the depressions have the following size and shape. (1) to (15), wherein the recrystallized tempered or rolled finished rolled copper foil,
0.2 ≦ D ≦ 2, W / D ≦ 15, N ≧ 500, L ≦ 50 (D: Depth of recess (μm), W: Width of recess in rolling direction (μm), N:
Dimple frequency (number / mm ² ), L: Distance between adjacent dimples (μm) (17) The number of inclusions with a thickness of more than 5 μm detected by microscopic observation of the cross section parallel to the rolling surface , 0.5 pieces / mm
^The recrystallized tempered or rolled finished rolled copper foil according to any one of (1) to (16), which is less than ² .
(18) After attaching the copper foil to the resin film, etching is performed so that the thickness of the copper foil is 10 μm or less, and then the width of 3
A recrystallized tempered or rolled rolled copper foil according to any one of (1) to (17), characterized in that it is used for a laminated plate having an electrode lead of 0 μm or less formed by etching, (19) The recrystallized tempered or rolled finished rolled copper foil according to (18), which is used as a material for a two-layer flexible laminate, is provided.

The reasons for limiting the inventions (1) to (19) will be described below. (1) Cube Texture Patent No. 3009383 has a (200) plane (equivalent to the (100) plane) in which the cubic texture is oriented in the rolling plane from the viewpoint of improving flexibility.
Is defined as the degree of. That is, the diffraction intensity (I) of the (200) plane on the rolled surface of the copper foil was measured using X-ray diffraction, and the diffraction intensity (I ₀ ) of the (200) plane of powdered copper (random orientation) was measured under the same conditions. When the ratio of these is I / I ₀ > 20, the condition is that satisfactory flexibility can be obtained. On the other hand, in order to obtain a satisfactory thinning etching property, I / I
_0> 20, is insufficient, there is a need to develop cubic texture to a level of I / I _0> 50. More preferably I
A level of / I ₀ > 60 is desired. The I / I ₀ value defines the ratio of the (100) plane oriented to the rolled surface. If this condition is satisfied, the etching rate in the depth direction will be equal for each crystal grain (Invention (1), (2), (8), (9)).

In the invention (8), the step of the crystal grain boundary caused by etching is also a problem. That is, even if the (100) plane is oriented on the rolling surface, the crystal may rotate around the normal to the rolling surface. If such rotation occurs, the disorder of the atomic arrangement at the crystal grain boundaries is large. Then, the grain boundary is selectively etched with respect to the inside of the grain, and a groove is formed at the grain boundary. Therefore, in order to suppress this rotation, the [10
The angle between the [0] direction and the rolling direction was defined. That is,
If the angle between the [100] direction and the rolling direction is within 10 ° (θ ≦ 10 °), the percentage of the number of crystals is 60% or more (α
≧ 60%) reduces the step of the crystal grain boundary,
By setting the above (α ≧ 80%), almost no step of the crystal grain boundary is recognized. A more desirable ratio is 90% or more (Invention (11)).

The angle formed by the [100] direction and the rolling direction is 10 °
The ratio of the crystals within is EBSP (Electron Backscattering
Pattern) method. In the EBSP method, an electron beam is incident on the sample surface and the Kikuchi pattern is obtained from the reflected electrons generated at this time. By analyzing this Kikuchi pattern, the crystal orientation at the electron beam incident position can be known. The orientation distribution of the sample surface is measured by two-dimensionally scanning the electron beam on the sample surface and measuring the crystal orientation at a predetermined pitch (Naoya Ishibashi: Material Science, Vol.37, No.3).
(2000), pp.116-122).

(2) Recrystallization annealing Since the cubic texture of copper develops when it is refined into a recrystallization texture, it is necessary to perform a heat treatment for recrystallizing the copper foil before the thinning etching. There is (Invention (1),
(8)). In a three-layer flexible substrate, an adhesive made of a thermosetting resin such as epoxy is used to bond a copper foil and a resin film such as polyimide. To cure this adhesive, heat treatment is performed at a temperature of 130 to 170 ° C for several hours to several tens of hours. It suffices to refine the copper foil into a recrystallized structure by this heat treatment. There are several manufacturing methods for a two-layer flexible substrate. One of them is the casting method, in which a varnish containing polyamic acid, which is a precursor of a polyimide resin, is applied on a copper foil and heat-cured to form a copper foil. Form a polyimide film on the foil. In this work hardening treatment, heating is performed at a temperature of about 300 ° C for several tens of minutes to several hours.
It suffices to refine the copper foil into a recrystallized structure by this heat treatment.

On the other hand, it is possible to anneal the copper foil to prepare a recrystallized structure before or after the step of forming the resin film. When copper foil is annealed and recrystallized, cubic oriented grains are formed at the initial stage of recrystallization. afterwards,
Even if annealing is continued, the degree of cubic texture development does not change. The degree of cubic orientation development does not depend on the annealing temperature. A typical recrystallized texture of rolled copper foil can be obtained by annealing the rolled copper foil at a temperature 50 ° C higher than the semi-softening temperature. Here, the semi-softening temperature is an annealing temperature at which the tensile strength becomes an intermediate value between the value before annealing and the value after complete recrystallization when annealed for a predetermined time.

(3) Rolling Work Structure that Develops Cubic Orientation In order to manufacture a copper foil in which a cubic texture develops when recrystallized and annealed, the working structure in rolling is important. The rolling structure of copper (alloy) has (110) [112] as the main orientation,
Further, the rolling structure which can obtain I / I ₀ > 50 described in the above item (1) is a feature of the present invention. In order to obtain such a rolling work structure, it is effective to raise the final rolling workability and reduce the crystal grains by recrystallization annealing before the final rolling (Invention (3)). For example, it is effective to set the final rolling degree to 90% or more and the grain size before final rolling to 20 μm or less.

(4) Composition that develops cubic orientation In the present invention, a method for stably obtaining a sharper cubic orientation is studied from the viewpoint of alloy components, and the rolling workability and the grain size before final rolling are examined. In addition to the optimization of, it was discovered that controlling the total amount of impurities in Cu and adding an appropriate amount of Ag to Cu are effective. For pure copper processed into copper foil,
There are two types: tough pitch copper with an oxygen concentration of 100 to 500 mass ppm (hereinafter mass ppm is referred to as ppm) and oxygen-free copper with an oxygen concentration of 10 ppm or less. Both tough pitch copper and oxygen-free copper can be used as the material for the copper foil of the present invention.

As a result of investigating the relationship between the total amount of impurities and the degree of cubic orientation development, in tough pitch copper, the impurities were 40 ppm.
If it exceeds, the development of the cubic orientation is hindered (Invention (4)),
In oxygen-free copper, when the impurities exceeded 20 ppm, the development of cubic orientation was inhibited (Invention (5)). In this way, tough pitch copper has a larger allowable amount of impurities than oxygen-free copper, but in tough pitch copper, the impurities precipitate as oxides, and the amount of solid solution impurities that contribute to the inhibition of cubic orientation decreases. Here, the glow discharge mass spectrometry (GD-M
S) was used for semi-quantitative analysis of all elements with an atomic weight of 3 (Li) or higher, and the concentrations of the elements detected at concentrations of 0.1 ppm or higher were added. VG9000 made by VG Elemental
A double focusing GDMS was used and Ar was used as the discharge gas. As will be described later, Ag contributes to the development of the cubic orientation, so Ag was excluded from the target of the prescribed impurities. Further, O is also excluded from the target of the impurity regulation because it has the effect of making the impurities harmless as described above. Furthermore, H and H
Noble gas elements such as e and Ar (abbreviated as “gas” below) are also excluded from the target of impurity regulation because they are unrelated to the development of cubic orientation.

The effect of adding Ag on the cubic orientation development is that the Ag concentration is 100 to 700 ppm in both tough pitch copper and oxygen-free copper.
Was observed at a higher level in the range of. Patent No.
As described in No. 2505480, it has been known that the addition of a large amount of Ag to Cu suppresses the development of cubic texture, but the addition of an appropriate amount of Ag sharpens the cubic orientation in the past. Not reported. The conventional purpose of adding Ag to Cu is to impart heat resistance to Cu (Japanese Patent Laid-Open No. 2000-212661).
Etc.) and imparting elongation (Japanese Patent Laid-Open No. 11-140564). Ordinary tough pitch copper and oxygen-free copper contain about 10 ppm Ag, but it is possible to further develop the cubic texture by adding a trace amount of Ag. Even if the total amount added is less than 100 ppm, there is some effect, and by adding more than 100 ppm, a higher effect can be obtained. However, when Ag exceeds 700 ppm, the degree of cubic orientation development decreases, and Ag is more expensive than Cu, which is also disadvantageous in terms of raw material cost (inventions (6), (7), (14), (1
Five)). It should be noted that even if a small amount of Ag is added to Cu, there is no problem in characteristics and it is effective for the development of cubic texture, although it is slight, so in the present invention, Ag of less than 100 ppm may be contained. Possible (Inventions (4), (5), (12), (13)).

When selecting the material of the copper foil, it is necessary to pay attention to the softening temperature. The normal softening temperature of oxygen-free copper is higher than that of tough pitch copper, and the addition of Ag increases the softening temperature. When the copper foil is recrystallized in the step of forming the resin film, it is important to adjust the components so that it recrystallizes according to the heat history at that time. In addition, if the final rolling degree is increased to develop a cubic texture, the softening temperature may decrease and softening may occur during storage at room temperature.
Ingredients can be adjusted to prevent this room temperature softening.
For example, a method using oxygen-free copper with a controlled amount of impurities (Japanese Patent Laid-Open No. 2000-212660) and a method using tough pitch copper with an appropriate amount of Ag added (Japanese Patent Laid-Open No. 2000-212661) have been proposed.

(5) Inclusions When inclusions (phases different from copper) are present, the etching rates of the inclusions and copper are different, so that the inclusions remain unmelted to form protrusions, or the inclusions precede copper. It melts and forms a recess. Therefore, the frequency of large inclusions is regulated. In the case of the present invention, the thickness of inclusions becomes a problem. The inclusions are observed on a cross section parallel to the rolling direction after mirror polishing.
When the number of inclusions having a thickness of more than 5 μm is 0.5 pieces / mm ² or more, the adverse effect caused by the unevenness due to the inclusions cannot be ignored (Invention (17)). The inclusions include crystallized substances generated during casting, precipitates generated during casting or heat treatment, refractory substances caught in the molten metal during melting, and foreign substances pushed into the material surface during rolling.

(6) Surface texture When the copper is cold-rolled, crack-like depressions formed on the surface are used as the starting points of corrosion to obtain a smooth etched surface.
For that purpose, it is important to uniformly disperse the small dents with high frequency. The conditions are as follows (Invention (1
6)). 0.2 ≦ D ≦ 2, W / D ≦ 15, N ≧ 500, L ≦ 50 (D: Depth of depression (μm), W: Width of depression in rolling direction (μm), N: Frequency of depression (pieces / mm ² ), L: Distance between adjacent depressions (μm))

FIG. 1 shows a typical form of the depression. Moreover, FIG. 2 is a surface profile of the same sample. The unevenness on the surface is measured in the direction parallel to the rolling direction using the unevenness SEM described later. Fig. 2 shows the definition of the width (W) of the recess in the rolling direction and the depth (D) of the recess. D is
If it is smaller than 0.2 μm, it does not act as a starting point of corrosion. D is 2
If it is larger than μm, concavity and convexity on the etching surface will become large. The sharper the dent morphology, the greater the effect as the starting point of corrosion, and the W / D must be 15 or less. Moreover, in order to obtain an effective effect, the frequency of depressions (N) is 500 / mm ²
The maximum distance (L) between adjacent depressions is 50.
It is necessary to disperse evenly so that the particle size becomes less than μm.

(7) Use of copper foil, etc. The thinning of the copper foil by etching is carried out for the purpose of making the circuit of the flexible substrate fine pitch. That is, the copper foil of the present invention is a copper foil suitable for fine pitch applications. In particular, copper foil with a thickness of 10 μm or less (invention (1
After thinning etching in 8)), it produces a remarkable effect when forming electrode leads with a width of 30 μm or less. The two-layer flexible substrate is thinner than the three-layer flexible substrate because it has no adhesive layer and is therefore advantageous for high-density mounting. By using the copper foil of the present invention in a two-layer flexible substrate to form a fine pitch circuit, higher density mounting becomes possible. Hereinafter, the present invention will be described with reference to examples.

[0033]

Example 1 A 200 mm thick tough pitch copper ingot was prepared by adding Ag to a content of 180 to 230 ppm and adjusting the O concentration in the range of 150 to 200 ppm. The grade of electrolytic copper used as the raw material was adjusted so that the total concentration of impurities other than Cu, Ag, O, H, and noble gases was 40 ppm or less. 900 this ingot
Hot rolling was performed from ℃ to obtain a plate with a thickness of 10 mm. After that, cold rolling and annealing are repeated, and finally cold rolling is performed to a thickness of 18 μm.
Processed into copper foil. In the final annealing before cold rolling, the crystal grain size was adjusted to the range of 10 to 15 μm. In the final cold rolling,
The workability was changed variously. The rolling degree (R) is defined by the following equation. R = (t ₀ −t) / t ₀ × 100 (t ₀ : thickness before rolling, t:
Thickness after rolling) This copper foil was a rolled finished copper foil according to the invention (2), and was annealed at a temperature higher by 50 ° C than the semi-softening temperature to recrystallize. The annealing time in this case was 30 minutes. The following evaluations were performed on the recrystallized copper foil.

X-ray diffraction: The integrated value (I) of the diffraction intensity of the (200) plane in the rolled surface was obtained. (200) of finely powdered copper (sample with random orientation) whose value was measured in advance
The value of I / I ₀ was calculated by dividing by the integrated value of the diffraction intensity of the surface (I ₀ ). In addition, the integral value of the peak intensity was measured using a Co tube for both foil and fine copper powder, 2θ = 57 to 63 ° (θ is the diffraction angle)
It went in the range of.

EBSP: The sample surface was electrolytically polished in phosphoric acid to obtain a mirror surface. After that, TSL's OIM (Orientation Imag
ing Micrograph), the surface of a sample of 0.25 mm × 0.3 mm was measured at intervals of 1 μm, and the ratio of crystals whose angle between the [100] direction and the rolling direction was within 10 ° to the total number of crystals (hereinafter α And asked).

Etching test: temperature 50 ° C., concentration 100 g / L
An aqueous solution of sodium persulfate was sprayed onto the surface of the sample at a pressure of 2 kg / cm ² , and the thickness was reduced by approximately 9 μm. Then, according to JIS B0601, the maximum height (Ry) of the surface was obtained using a contact roughness meter. The reference length was 0.8 mm and the measurement was performed in the direction parallel to the rolling direction. The measurement of Ry changes the place 5
The maximum value of the measured values of 5 times was calculated.

[0037]

[Table 1]

Table 1 shows I / I ₀ and α value of the (200) plane and Ry of the etched surface. The cubic orientation tends to develop as the final rolling reduction increases. The Ry data in Table 1 is shown in FIG. 3 in relation to I / I ₀ . In the range of I / I ₀ <50, Ry is a high value exceeding 3 μm. When Ry> 3 μm, bubbles were generated quite frequently between the resist film and the copper foil, making it impossible to form a circuit by etching. From the vicinity of I / I ₀ = 50, as I / I ₀ increases
Ry drops to a level below 3 μm. Circuit etching is possible if Ry ≤ 3 μm, but in terms of manufacturing yield and ease of manufacturing, it is desirable that Ry be as small as possible.
In the range of I / I ₀ > 60, there is considerable variation in Ry value, and there is no longer any tendency for Ry to decrease monotonically with increasing I / I ₀ . Therefore, it can be said that increasing I / I ₀ to 60 is sufficient.

FIG. 4 shows the relationship between the α value and Ry. I / I ₀
The data is stratified according to the level of. There is a good correlation between α value and Ry. α ≧ 60% (ie inventions (8), (9))
With Ry ≤ 3 μm, circuit etching becomes possible. α ≧
At 80% (invention (11)), Ry ≦ 2 μm, and at this level of Ry, circuit etching can be performed with almost no problems. In the range of α ≧ 90%, Ry ≦ 1.5 μm. This Ry value is close to the Ry value of the surface before etching (Fig. 2
(See), it means that the ideal etching was performed. In addition, in the data of I / I ₀ > 60 (○) in FIG.
It can be seen that the variation in Ry observed in the range of I / I ₀ > 60 in FIG.

Example 2 Tough pitch copper containing various concentrations of Ag (O concentration: 150-
200 ppm) and oxygen-free copper (O concentration: 2-5 ppm) ingots were melted. The total concentration of impurities other than Cu, Ag, O, H and noble gases was adjusted to the range of 7 to 12 ppm. The thickness of the ingot is 150mm. This ingot was hot-rolled from 850 ° C to obtain a 12 mm thick plate. After that, cold rolling and annealing were repeated, and finally cold rolling was applied to form a copper foil with a thickness of 12 μm. The final rolling workability of tough pitch copper is set to 2 levels of 99.2% and 95.2%, and the final rolling workability of oxygen-free copper is 9
It was set to 9.2%. In the final annealing before cold rolling, the grain size was adjusted to the range of 10 to 15 μm. Among the copper foils, the one having an Ag content within the range of 100 to 700 ppm corresponds to the rolled finished copper foil according to the inventions (6) and (14). This copper foil was annealed at a temperature higher by 50 ° C. due to the semi-softening temperature and recrystallized. The annealing time in this case was 30 minutes. For the recrystallized copper foil, the I / I ₀ value and α value of the (200) plane were measured by the above-described measurement method.

[0041]

[Table 2]

[0042]

[Table 3]

The measurement results of the I / I ₀ value and α value of the (200) plane are shown in Table 2 and Table 3, respectively. The data are also shown in FIGS. 5 and 6, respectively. Both I / I ₀ value and α value are Ag
It gradually increases with the addition of Ag, and increases sharply when Ag exceeds 100 ppm, and shows a substantially constant high value at Ag = 150 to 600 ppm. When Ag exceeds 700 ppm, I /
Both I ₀ value and α value decrease sharply.

As shown in Tables 2 and 3, when Ag is 5000 ppm, both the I / I ₀ value and the α value show extremely low values, and the characteristic of pure copper is that the cubic orientation develops as a recrystallization texture. Completely lost. The higher the rolling degree, the more developed the cubic orientation. Further, the tough pitch copper has a more developed cubic orientation than the oxygen-free copper, but as described later, the effect of impurities impeding the development of the cubic orientation is that the tough pitch copper is smaller.

Example 3 Tough pitch copper without addition of Ag, content of 180 to 230 p
Cu, Ag, O, H, and H were measured for tough pitch copper with Ag added to pm, oxygen-free copper without Ag, and oxygen-free copper with Ag added to 180-230 ppm. The total concentration of elements other than rare gas (hereinafter referred to as “impurity concentration”) was changed variously. O concentration of tough pitch copper is 150
The oxygen concentration of oxygen-free copper was adjusted to the range of up to 200 ppm and the oxygen concentration of oxygen-free copper to the range of 1 to 5 ppm. Even if Ag was not added, 7 to 15 ppm of Ag was mixed from the raw material electrolytic copper.

A 225 mm thick ingot is melted and melted at 875 ° C.
Was hot-rolled into a plate with a thickness of 9 mm. After that, cold rolling and annealing were repeated, and finally, cold rolling with a workability of 98.8% was performed to obtain a copper foil with a thickness of 18 μm. In the final annealing before cold rolling, the grain size was adjusted to the range of 10 to 15 μm. Of these copper foils, tough pitch copper added with Ag corresponds to invention (9) cited as (14), oxygen-free copper added with Ag corresponds to invention (9) referred to as (15), and either Is also a rolled foil. These copper foils were annealed and recrystallized at a temperature 50 ° C. higher than the semi-softening temperature. The annealing time in this case was 30 minutes. The I / I ₀ value and α value of the (200) plane of the recrystallized copper foil were measured. Each measuring method is described above.

[0047]

[Table 4]

Table 4 shows the measurement results of the I / I ₀ value and α value of the (200) plane. The concentrations of S, Fe, As, Sb, Bi, Pb, Se, Te, Cd and Sn, which are general impurities contained in electrolytic copper which is a raw material of copper foil, are shown. The total impurities are Cu, Ag, O,
Of the elements other than H and noble gases, it is the value obtained by adding the concentrations of the elements detected at a concentration of 0.1 ppm or more.
Concentrations of elements other than S, Fe, As, Sb, Bi, Pb, Se, Te, Cd, Sn are also included. As such elements, there were Al, Si contained in refractories and P added as a deoxidizer.
Fig. 7 shows the relationship between the total amount of impurities and the I / I ₀ value and α value.
It shows in FIG.

Tough pitch copper (FIG. 7): Impurity concentration is 40 p
If it is pm or less, an I / I ₀ value exceeding 50 is obtained regardless of whether Ag is added or not (Inventions (4) and (6)). 20 impurities
In the range of ppm or less, I / I is almost constant with respect to the impurity concentration.
_A value of ₀ has been obtained. The range of the impurity concentration at which an α value of 60 or more is obtained is 40 ppm or less when Ag is added (invention (1
2)), 30 ppm or less without adding Ag (Invention (14)). The range of impurity concentration that can obtain α value of 80 or more is Ag
22 ppm or less when added, 14 ppm when no Ag is added
It is the following. Further, unlike the I / I ₀ value, the α value monotonically increases as the impurity concentration decreases. That is, when the amount of impurities is small, the α value increases even if the I / I ₀ values are the same. This behavior causes the variation of the α value in FIG. 3 described above.

Oxygen-free copper (FIG. 8): If the impurity concentration is 20 ppm or less, I exceeds 50 regardless of whether Ag is added or not.
/ I ₀ value is obtained (Invention (13)). The range of the impurity concentration with which the α value of 60 or more is obtained is 20 ppm or less (Invention (13), (15)) both with and without addition of Ag. The range of the impurity concentration that can obtain an α value of 80 or more is 15 ppm or less when Ag is added, and 8 ppm or less when Ag is not added. Compared to FIG. 7, it can be seen that oxygen-free copper is more sensitively affected by impurities than tough pitch.

Example 4 With respect to a copper foil having a thickness of 18 μm and containing 250 to 300 ppm of Ag, the form and frequency of inclusions were variously changed. As a method of increasing inclusions, methods such as increasing the oxygen concentration and adding an active metal were adopted. The final rolling degree was 99.1%, and the grain size before final cold rolling was adjusted to the range of 15 to 20 μm. Apply these copper foils at a temperature 50 ° C above the semi-softening temperature
It was annealed for a minute and recrystallized.

A cross section parallel to the rolling direction was mirror-polished, and the number of inclusions having a width in the thickness direction of more than 5 μm was measured using a scanning electron microscope. The observation area was 10 mm ² . Further, thinning etching was performed under the same conditions as in Example 1, and the etching surface was observed using an electron beam three-dimensional roughness analyzer ERA-8000 manufactured by Elionix Co., Ltd. Was measured.

[0053]

[Table 5]

The evaluation results are shown in Table 5. Inclusions with a thickness of more than 5 μm may cause protrusions with a height of more than 2 μm on the surface after etching. In the process of forming a circuit by the next etching process, when a resist was applied to the etching surface, bubbles were generated around this protrusion. Etching of such an abnormal portion caused a disconnection of the circuit or a short circuit of the circuit, which reduced the manufacturing yield of the flexible substrate. When the generation of bubbles was remarkable, the etching process itself became impossible. The frequency of inclusions whose thickness exceeds 5 μm
When it was less than 0.5 / mm ^2, the abnormal rate due to inclusions during circuit etching decreased to a negligible level (Invention (17)).

Example 5 A tough pitch copper ingot having a thickness of 200 mm was prepared by adding Ag of 450 to 500 ppm and adjusting the O concentration in the range of 150 to 200 ppm. 20 pp total concentration except Cu, Ag, O, H and noble gases
The quality of the electrolytic copper used as the raw material was adjusted so that it would be less than m. This ingot was hot-rolled from 750 ℃, and the thickness was 10 mm.
Got the plate. After that, cold rolling and annealing were repeated, and finally, a test rolling machine was used to perform cold rolling with a workability of 96.4% to a thickness of 12
It was processed into a copper foil of μm. In this final rolling, the workability of the final pass was set to 30%, the rolling speed was set to 80 m / min, the viscosity of the rolling oil was set to 10 cSt, and the occurrence of surface dents was changed by changing the diameter of the rolling roll used. Changed to. In the final annealing before cold rolling, the grain size was 10 to 15 μm.
Adjusted to the range. This copper foil was annealed at a temperature 50 ° C. higher than the semi-softening temperature and recrystallized. The annealing time in this case was 30 minutes. The I / I ₀ value of the (200) plane after recrystallization was in the range of 60 to 65, and the α value was in the range of 85 to 90.

For each sample, using an electron beam three-dimensional roughness analyzer ERA-8000 manufactured by Elionix Co., Ltd., 0.2 ≦ D ≦ 2, W / D ≦ 15 (D: depth of depression ( μm), W: width of the depression in the rolling direction (μm)). In addition, the distance between adjacent depressions was measured and the largest distance (L) was obtained. Next, to each sample, an aqueous solution of sodium persulfate having a temperature of 30 ° C. and a concentration of 50 g / L was injected at a pressure of 1.5 kg / cm ² ,
About 6 μm was etched in the depth direction. Since this etching solution has a weaker corrosive power than the etching solution used in Example 1, it is likely to be affected by the surface depression. After that, JIS B0601
Then, the maximum height (Ry) of the surface was obtained using a contact roughness meter. The standard length was 0.8 mm, and the measurement was performed 5 times at different locations in the direction parallel to the rolling direction, and the maximum value of the 5 measurements was obtained.

[0057]

[Table 6]

Table 6 shows the evaluation results. From Nos. 1 to 5, it can be seen that Ry decreases as the number of depressions increases. No.6
Shows an example in which the amount of rolling oil dropped is reduced, and the distribution of the oil film between the roll and the rolled material is non-uniform, and the distribution of depressions is localized. As a result, No. 6 has no Ry lowering effect. On the other hand, rolling was performed under the same conditions as No. 4 using rolling oil with a high viscosity of 20 cSt, and cavities with a maximum D of 2.7 μm were introduced at a frequency of 1560 / mm ² , and Ry = 3.02 μm.
On the contrary, the unevenness became large. It should be noted that such an influence of the depression was not recognized under the etching conditions of Example 1.

[0059]

According to the present invention, when a surface of a rolled copper foil is etched, a smooth surface can be obtained. Therefore, this copper foil is suitable for a flexible substrate on which fine pitch processing is performed.

[Brief description of drawings]

FIG. 1 is an SEM image of the surface of a copper foil in which dents have occurred.

FIG. 2 is an uneven profile on the surface of a copper foil.

FIG. 3 is a graph showing the relationship between the I / I ₀ of the (200) plane and the maximum height of the surface after etching.

FIG. 4 is a graph showing the relationship between the maximum height and the ratio (α (%)) of crystals in which the angle between the <100> orientation and the rolling direction is within 10 °.

FIG. 5 is a graph showing the influence of Ag concentration on I / I ₀ of a (200) plane.

[Fig. 6] Angle of Ag concentration <100> direction and rolling direction is 1
It is a graph which shows the ratio (alpha (%)) of the crystal which is within 0 degree.

FIG. 7 is a graph showing the influence of the impurity concentration on I / I ₀ of the (200) plane.

FIG. 8 is a graph showing the proportion (α (%)) of crystals in which the angle between the <100> direction of the impurity concentration and the rolling direction is within 10 °.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // C22F 1/00 613 C22F 1/00 613 622 622 661 661A F term (reference) 4E002 AA08 AD13 BC05 CB01 CB03 4E351 AA04 AA16 BB01 DD04 DD54 GG20

Claims (19)

[Claims] 1. The diffraction intensity (I) of the (200) plane obtained by performing X-ray diffraction on the rolled surface of a rolled copper foil having a thickness of 20 μm or less has the same fine copper powder condition as that of the rolled copper foil. Recrystallized tempered rolled copper excellent in uniform etching thinning property, characterized in that I / I ₀ > 50 with respect to the diffraction intensity (I ₀ ) of the (200) plane determined by X-ray diffraction under Foil. 2. The rolling structure has an I / I ₀ > 50 (where I is determined by X-ray diffraction of the rolled surface of the rolled copper foil by annealing at a temperature 50 ° C. higher than the semi-softening temperature). Recrystallization represented by the (200) plane diffraction intensity, and I ₀ is the (200) plane diffraction intensity obtained by X-ray diffraction of fine copper powder under the same conditions as the rolled copper foil. A rolled copper foil having a rolled finish, which is capable of inducing a structure. 3. The rolling structure has a crystal grain size of 20 μm.
The rolled copper foil having a thickness of 20 μm or less according to claim 2, which is formed by finish rolling a rolled copper foil having the following recrystallization structure at a working ratio of 90% or more. 4. The recrystallized tempered or rolled finished rolled copper foil according to claim 1, wherein the tough pitch copper has a total amount of elements other than Cu, Ag, O, H and rare gas elements of 40 mass ppm or less. . 5. The recrystallized heat-treated or rolled-finished rolled copper according to claim 1, comprising oxygen-free copper having a total amount of elements other than Cu, Ag, O, H and rare gas elements of 20 mass ppm or less. Foil. 6. Cu, A containing 100 to 700 mass ppm of Ag
The total amount of elements other than g, O, H and rare gas elements is 40mass.
The recrystallized tempered or rolled finished rolled copper foil according to claim 1, 2 or 3, which is made of tough pitch copper having a sppm or less. 7. Cu, A containing 100 to 700 mass ppm of Ag
The total amount of elements other than g, O, H and rare gas elements is 20mass.
The recrystallized heat-treated or roll-finished rolled copper foil according to claim 1, comprising oxygen-free copper having a sppm or less. 8. The diffraction intensity (I) of the (200) plane obtained by X-ray diffracting the rolled surface of a rolled copper foil having a thickness of 20 μm or less shows that the fine copper powder has the same condition as the rolled copper foil. I / I ₀ > 50 with respect to the diffraction intensity (I ₀ ) of the (200) plane obtained by X-ray diffraction below, and the angle (θ) formed by the [100] direction of the crystal and the rolling direction is The ratio (α) to the total number of crystals within 10 ° (θ ≦ 10 °) is 60% or more (α ≧ 60
%) A recrystallized temper rolled copper foil with excellent uniform etching thinning property. 9. I / I ₀ > 50 (where I is determined by X-ray diffraction of the rolled surface of the rolled copper foil) by annealing the rolled structure at a temperature 50 ° C. higher than the semi-softening temperature. (2
Is the diffraction intensity of the (00) plane, and I ₀ was obtained by X-ray diffraction of fine copper powder under the same conditions as the rolled copper foil (200).
Surface diffraction intensity) and α ≧ 60% (where α is
A rolled-finished rolled copper foil capable of inducing a recrystallized structure represented by (ratio to the total number of crystals of a crystal in which the angle formed by the [100] direction of the crystal and the rolling direction is within 10 °). 10. The rolling structure has a crystal grain size of 20 μm.
A rolled copper foil having a thickness of 20 μm or less according to claim 9, which is formed by finish rolling a rolled copper foil having a recrystallization structure of m or less at a workability of 90% or more. Rolled copper foil. 11. The recrystallized tempered or rolled finished rolled copper foil according to claim 8, 9 or 10, wherein the α is 80% or more (α ≧ 80%). 12. The alloy according to claim 8, 9, 10 or 11 comprising tough pitch copper in which the total amount of elements other than Cu, Ag, O, H and rare gas elements is 30 mass ppm or less. Crystal-conditioned or rolled rolled copper foil. 13. The recrystallized temper or rolled finish according to claim 8, 9, 10 or 11, which is made of oxygen-free copper having a total amount of elements other than Cu, Ag, O, H and rare gas elements of 20 mass ppm or less. Rolled copper foil. 14. Cu containing 100 to 700 mass ppm of Ag,
The total amount of elements other than Ag, O, H and rare gas elements is 40 ma
10. A tough pitch copper having a ss ppm or less,
The recrystallized tempered or rolled finished rolled copper foil according to 10 or 11. 15. Cu containing 100 to 700 mass ppm of Ag,
The total amount of elements other than Ag, O, H and rare gas elements is 20 ma
11. An oxygen-free copper containing less than ss ppm.
Alternatively, the recrystallized tempered or rolled finished rolled copper foil according to item 11. 16. The crack-shaped depressions extending in the direction orthogonal to the rolling direction are dispersed on the surface, and the depressions have the following dimensions and shapes. Recrystallized tempered or rolled finished rolled copper foil described. 0.2 ≦ D ≦ 2, W / D ≦ 15, N ≧ 500, L ≦ 50 (D: Depth of depression (μm), W: Width of depression in rolling direction (μm), N: Frequency of depression (pieces / mm ² ), L: Distance between adjacent depressions (μm)) 17. The number of inclusions having a thickness of more than 5 μm, which is detected by observing the structure of a section parallel to the rolled surface, is 0.5 /
The recrystallized heat-treated or rolled finished rolled copper foil according to any one of claims 1 to 16, characterized in that it is less than mm ² . 18. A laminate used for laminating copper foil with a resin film, etching the copper foil to a thickness of 10 μm or less, and then forming electrode leads with a width of 30 μm or less by etching. The recrystallized tempered or rolled finished rolled copper foil according to any one of claims 1 to 17, which is characterized by the above-mentioned. 19. The recrystallized tempered or rolled finished rolled copper foil according to claim 18, which is used as a material for a two-layer flexible laminate.