JP2013216970A - Rolled copper foil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolled copper foil that is superior in etching property and flexibility and can be suitably used for an FPC (flexible printed circuit board) and so on.SOLUTION: A rolled copper foil contains copper of 99.9% or more in mass percentage. When a calculated X-ray diffraction intensity from {112} surface in a rolled surface is I{112} and a calculated X-ray diffraction intensity from {110} surface is I{110}, the rolled copper foil satisfies a relation of 2.5≤I{110}/I{112}≤6.0.

Description

  The present invention relates to a rolled copper foil suitably used for FPC (flexible printed circuit board) and the like.

The FPC (Flexible Printed Circuit Board) uses a copper foil composite made by laminating a copper foil and a resin layer, and this copper foil is bent in consideration of the etching property when forming a circuit and the use of FPC. Sex is required.
By the way, FPC is generally used in a state where a copper foil is recrystallized. When a copper foil is rolled, the crystal rotates to form a rolling texture, and the rolling texture of pure copper is said to have {112} <111> called the Copper orientation as the main orientation. And it recrystallizes when heat is applied in the process until it anneals after rolling a rolled copper foil, or is processed into a final product, ie, the process until it becomes FPC. The recrystallized structure after forming the rolled copper foil is hereinafter simply referred to as “recrystallized structure”, and the rolled structure before being heated is simply referred to as “rolled structure”. The recrystallized structure greatly depends on the rolled structure, and the recrystallized structure can also be controlled by controlling the rolled structure.
For this reason, techniques for improving the flexibility by developing the Cube orientation of {001} <100> after recrystallization of the rolled copper foil have been proposed (for example, Patent Documents 1 and 2).

Japanese Patent No. 3856616 Japanese Patent No. 4716520

However, when the Cube orientation of the copper foil is developed too much, there is a problem that the etching property is lowered. This is not a single crystal even if the Cube texture develops, but it is a mixed grain state in which grains with large Cube orientation have small grains with other orientations. Is considered to change. Particularly, as the L / S width of the circuit becomes narrower (fine pitch), the etching property becomes a problem. If the Cube orientation is developed too much, the copper foil becomes too soft and the handling property may be inferior.
In order to adjust the degree of development of the Cube orientation, there is a method of controlling the rolling structure after recrystallization in the final rolling, but the degree of Cube orientation is not developed or developed too much, and the degree of development of the Cube orientation can be adjusted. There is a problem of not being able to do enough.
Accordingly, an object of the present invention is to provide a rolled copper foil that is excellent in both etching property and flexibility.

The inventors of the present invention have developed a rolling texture of the copper foil as the ratio of the presence of the {110} plane is larger than the ratio of the {112} plane in the rolling plane in the rolling structure, and the recrystallization We found that the Cube orientation developed during annealing. As a result, in order to appropriately adjust the degree of development of the Cube orientation that improves the flexibility but decreases the etching property, the ratio of the {112} and {110} planes to be developed on the rolled surface of the copper foil is controlled, and the rolling We succeeded in improving both the etching and bending properties of copper foil.
That is, the rolled copper foil of the present invention contains 99.9% or more of copper by mass, the calculated X-ray diffraction intensity from the {112} plane on the rolled surface is I {112}, and the calculated X from the {110} plane is X When the line diffraction intensity is I {110}, 2.5 ≦ I {110} / I {112} ≦ 6.0 is satisfied.

The rolled copper foil of the present invention contains 10 to 300 mass ppm in total of one or more selected from the group consisting of Ag, Sn, Mg, In, B, Ti, Zr and Au, with the remainder being Cu and inevitable It is preferable to consist of impurities.
The rolled copper foil of the present invention preferably contains 2 to 50 ppm by mass of oxygen.
The rolled copper foil of the present invention preferably satisfies I {112} ≦ 1.0 on the rolled surface after heating at 200 ° C. for 30 minutes.
The rolled copper foil of the present invention has an X-ray diffraction intensity of {200} plane of the rolled surface of the rolled copper foil of I {200} after heating at 350 ° C. for 1 second, and the {200} plane of the pure copper powder sample. When the X-ray diffraction intensity is I ₀ {200}, it is preferable that 5.0 ≦ I {200} / I ₀ {200} ≦ 27.0 is satisfied, and 13.0 ≦ I {200} / I ₀ {200} ≦ 27.0 is satisfied. It is preferable.
The rolled copper foil of the present invention preferably has a thickness of 4 to 70 μm.

  According to the present invention, it is possible to obtain a rolled copper foil that is excellent in both etching property and flexibility and can be suitably used for an FPC (flexible printed circuit board) or the like.

It is a figure which shows typically the relationship between the tension | tensile_strength applied to copper foil in the last recrystallization annealing, and the amount of Ag in copper foil for increasing {112} surface to the rolling surface of copper foil. It is a figure which shows the optical microscope image of the etching surface of Example 5 and Comparative Example 2, respectively. It is a figure which shows a response | compatibility of a reference | standard image and etching property evaluation.

  Hereinafter, the rolled copper foil which concerns on embodiment of this invention is demonstrated. In the present invention, “%” means “% by mass” unless otherwise specified.

<Composition>
The rolled copper foil contains 99.9% or more of copper by mass ratio. Examples of such a composition include oxygen-free copper standardized by JIS-H3510 (C1011) or JIS-H3100 (C1020) or tough pitch copper standardized by JIS-H3100 (C1100). Moreover, it is preferable that the oxygen content of rolled copper foil shall be 2-50 mass ppm. When the oxygen content in the rolled copper foil is as low as 2 to 50 mass ppm, cuprous oxide is hardly present in the rolled copper foil. For this reason, when the rolled copper foil is bent, there is almost no accumulation of strain caused by cuprous oxide, so that cracks hardly occur and the flexibility is improved. The upper limit of the oxygen content contained in copper is not particularly limited, but is generally 500 ppm by mass or less, and more generally 320 ppm by mass or less.
Furthermore, you may contain 10-300 mass ppm in total of 1 type, or 2 or more types chosen from the group of Ag, Sn, Mg, In, B, Ti, Zr, and Au. When these elements are added, the {110} plane tends to increase on the rolled plane, and it becomes easy to adjust the value of I {110} / I {112} described later. If the total amount of the above elements is less than 10 ppm by mass, the effect of developing the {110} plane is small, and if it exceeds 300 ppm by mass, the conductivity decreases and the recrystallization temperature rises, after the final rolling. In the annealing, it may be difficult to recrystallize while suppressing the surface oxidation of the copper foil.

<Thickness>
The thickness of the copper foil is preferably 4 to 100 μm, and more preferably 5 to 70 μm. When the thickness is less than 4 μm, the handleability of the copper foil may be inferior, and when the thickness exceeds 100 μm, the flexibility of the copper foil may be inferior.

<{112} surface and {110} surface of the copper foil rolled surface>
The presence intensity of each surface in the rolled copper foil surface calculated from the X-ray diffraction intensity of the {200}, {220}, {111} planes is defined as the calculated X-ray diffraction intensity. When the calculated X-ray diffraction intensity of the {112} plane is I {112} and the calculated X-ray diffraction intensity from the {110} plane is I {110}, 2.5 ≦ I {110} / I {112} Satisfies ≦ 6.0. A more preferable range is 4.0 ≦ I {110} / I {112} ≦ 5.6.

  Since the X-ray diffraction has a long wavelength, the diffraction intensity of the {200}, {220}, and {111} planes of copper foil can be measured, but the diffraction peak on the {422} plane (that is, the {112} plane) Cannot be obtained. Therefore, from the X-ray diffraction results of {200}, {220}, and {111} by the positive electrode point measurement method, the calculated X-ray diffraction of {110} plane and {112} plane using the geometrical relationship of crystal orientation Find strength. Note that the diffraction intensity of the {110} plane can be directly measured assuming that it is equal to the diffraction intensity of the {220} plane, but in the present invention, the calculation calculated from the diffraction intensity of the {200}, {220}, {111} plane X-ray diffraction intensity is applied.

Specifically, the calculated X-ray diffraction intensity values of the {110} plane and {112} plane were obtained as follows.
First, positive point map measurement of {200}, {220}, {111} planes of copper foil is performed. The positive dot diagram measurement method is a method for measuring X-ray diffraction while changing the angle of a biaxial (α, β) rotation mechanism attached to a goniometer for setting a sample. Then, from the X-ray diffraction positive electrode point measurement results (positive electrode point diagrams of {200}, {220}, {111} planes of copper foil), a set of {110} planes and {112} planes using geometric relationships The degree can be calculated. This calculation can be performed by converting into an inverted pole expression using commercially available software (for example, StandardODF (manufactured by Norm Engineering Co., Ltd.)).
The degree of assembly of the {110} plane and {112} plane is first measured for the positive electrode points on the {200}, {220}, {111} planes, and then the {200}, Measure the positive point of {220} and {111} planes. Then, the degree of aggregation of the {200}, {220}, and {111} planes is normalized by the degree of aggregation of the {200}, {220}, and {111} planes of the pure copper powder standard sample, respectively. Then, the normalized dot maps of the {200}, {220}, and {111} planes converted in this way are converted into reverse pole points by the above software, and the degree of aggregation of the {110} plane and {112} plane (calculation X (Line diffraction intensity) is calculated.

The rolled copper foil of the present invention is usually manufactured by repeating cold rolling and annealing several times (usually about 2 times) after hot rolling and chamfering, and then final recrystallization annealing and then final cold rolling. can do.
Here, “final recrystallization annealing” refers to the last of the annealing before the final cold rolling. The recrystallized structure after the final recrystallization annealing is referred to as “intermediate recrystallized structure” in order to distinguish it from the above-mentioned “recrystallized structure” (recrystallized structure after becoming a rolled copper foil). First, a method for easily adjusting the intermediate recrystallized structure includes changing the annealing temperature. However, when the final recrystallization annealing temperature is simply increased, recrystallized grains with random orientations grow, and when the recrystallized grains become mixed grains (the width of the distribution of crystal grain size increases), after the final rolling As a result, it is difficult to control the value of I {110} / I {112}.
On the other hand, when the tension applied to the copper foil in the final recrystallization annealing is increased, the tension becomes the driving force, the crystal grain size in the intermediate recrystallized structure increases, and there are many {112} faces on the rolled surface. it can. However, if the tension becomes too high, the {110} plane will decrease on the rolled surface after the final rolling, so the tension range should be adjusted so that the value of I {110} / I {112} is within the above range. . Moreover, since the tension value also varies depending on the final recrystallization annealing temperature and the amount of the above-described additive elements, the tension value may be adjusted accordingly. In addition, tension | tensile_strength is the tension | tensile_strength between each roll of the entrance side of the final recrystallization annealing atmosphere at the time of charging a copper strip in the atmosphere which performs final recrystallization annealing. Since the appropriate value (absolute value) of the tension varies depending on the annealing temperature and the copper strip component, it is preferable to manage a dimensionless value obtained by dividing the tension by the material yield strength at the annealing temperature.
Conventionally, the tension value in the continuous annealing furnace is usually set in the range of 0.1 to 0.15 for the purpose of preventing deterioration of the transport roll.

FIG. 1 shows an example of adjusting the tension applied to the copper foil in the final recrystallization annealing for increasing the {112} plane on the rolled surface of the copper foil. As described above, when the tension is increased, the {112} surface increases on the rolled surface, but when the amount of the additive element (such as Ag described above) increases, the {110} surface increases on the rolled surface. If it is not hung, the ratio of {112} face does not increase on the rolled face. Therefore, a region surrounded by the two lines in FIG. 1 is a preferable range.
It is preferable that I {112} / I {100} ≦ 1.0 is satisfied on the rolled surface after heating the rolled copper foil at 200 ° C. for 30 minutes. The heating at 200 ° C. for 30 minutes simulates the heating condition of the copper foil when FPC is produced by the so-called casting method. When the copper foil is completely recrystallized by this heating and no unrecrystallized region remains, I {112} ≦ 1.0. When I {112} / I {100}> 1.0, unrecrystallized remains and the flexibility of FPC may be inferior.
It is preferable to satisfy 5.0 ≦ I {200} / I ₀ {200} ≦ 27.0 after heating the rolled copper foil at 350 ° C. for 1 second. If the {001} <100> orientation (Cube orientation) develops after recrystallization, good flexibility is obtained, so the higher I {200} / I ₀ {200} is better. If 5.0> I {200} / I ₀ {200}, the flexibility may be lowered. In particular, 13.0 ≦ I {200} / I ₀ {200} ≦ 27.0 is more preferable. It is industrially difficult to achieve I {200} / I ₀ {200}> 27.0 in balance with other characteristics, so the upper limit was set to 27.0.

<Manufacture of rolled copper foil>
A 100 mm thick ingot was cast from tough pitch copper or oxygen-free copper added with the elements shown in Table 1 and hot rolled to a thickness of 10 mm at 800 ° C. or higher to chamfer the oxide scale on the surface. . Thereafter, cold rolling and annealing were repeated to obtain a rolled plate coil having a thickness of 0.5 mm. After the final cold rolling, the copper strip was passed through a continuous annealing furnace at 700 ° C. and under the tension shown in Table 1 for final recrystallization annealing. The tension value was standardized by dividing by the yield strength under the recrystallization annealing temperature of the sample ({Tension (N / mm ² ) / proof strength under the recrystallization annealing temperature (N / mm ² )}). ). Moreover, the heating time of the copper strip in recrystallization annealing was 100 to 200 seconds. Finally, it was finished to the thickness shown in Table 1 by final cold rolling. The degree of rolling in the final cold rolling was 86 to 99%.
In addition, “Ag190ppm OFC” in the column of the composition of Table 1 is 190 mass ppm in oxygen-free copper OFC of JIS-H3510 (C1011) (Example 10) or JIS-H3100 (C1020) (other than Example 10). It means that Ag is added. “Ag 190 ppm TPC” means that 190 mass ppm of Ag was added to tough pitch copper (TPC) of JIS-H3100 (C1100). The same applies to other addition amounts.

<Crystal orientation>
Using the X-ray diffractometer (RINT-2500: manufactured by Rigaku Corporation) for the surface (rolled surface) of the copper foil after the final cold rolling, positive point measurement on the {200}, {220}, and {111} planes, respectively ( X-ray reflection average intensity). From the obtained measurement results, Standard ODF (manufactured by Norm Engineering Co., Ltd.) was used to convert to inverted poles, and the calculated X-ray diffraction intensities of the {110} plane and {112} plane were calculated.
The measurement conditions of X-ray diffraction were incident X-ray source: Cu, acceleration voltage: 30 kV, tube current: 100 mA, divergence slit: 0.5 degree, scattering slit: 4 mm, light receiving slit: 4 mm, and divergence longitudinal limiting slit: 1.2 mm . Also, after standardizing the degree of aggregation of {200}, {220}, {111} surfaces using the value of pure copper powder (X-ray reflection average intensity) obtained by X-ray diffraction on each surface under the same conditions, Converted to a pole. As the pure copper powder, fine powder copper (325 mesh) was used.

<Crystal grain size>
The crystal grain size of the copper foil immediately after the final recrystallization annealing (before the final cold rolling) was measured on the rolled surface according to the cutting method of JIS-H0501.
<I {200} / I ₀ {200}>
The copper foil after the final cold rolling was annealed at 200 ° C. for 0.5 hour and after annealing at 350 ° C. for 1 second, respectively, and the X-ray diffraction intensity of {200} plane was measured on the surface. Then, the value of pure copper powder was subjected to X-ray diffraction under the same conditions (I ₀ {200}: X-ray reflection average intensity) normalized with.
The measurement conditions for X-ray diffraction are: incident X-ray source: Cu, acceleration voltage: 25 kV, tube current: 20 mA, divergence slit: 1 degree, scattering slit: 1 degree, receiving slit: 0.3 mm, divergence longitudinal limiting slit: 10 mm, The monochrome light receiving slit was 0.8 mm. As the pure copper powder, fine powder copper (325 mesh) was used.

<Flexibility>
First, a thermoplastic polyimide adhesive was applied to a 12.5 μm thick thermosetting polyimide film and dried. Next, copper foils after the final cold rolling were laminated on both sides of the film, and then thermocompression bonded to produce double-sided CCL. For this double-sided CCL, a circuit pattern having a line / space width of 100 μm / 100 μm was formed on the copper foils on both sides by etching, and then a coverlay film having a thickness of 25 μm was coated and processed into an FPC.
This FPC was subjected to a slide bending test to evaluate the flexibility. Specifically, using a sliding tester (Applied Giken Sangyo Co., Ltd., TK-107 type), the slide radius r (mm) is r = 4 mm for Example 9, and for other examples and comparative examples r = 0.72 mm, and in all cases, the FPC was bent at a sliding speed of 120 times / minute.
When the electrical resistance of the copper foil circuit increases by 10% compared to before the test, the number of bendings is less than 150,000 times as evaluation x, and 100,000 to less than 150,000 times is evaluated as △, 150,000 times A value of ˜300,000 times was evaluated as ○, and a value exceeding 300,000 times was evaluated as ◎. If the flexibility is ◎ to Δ, it can be said that the flexibility is good.

<Etching property>
The above-mentioned double-sided CCL was etched by immersion for 1 minute in a stirred etching solution having a liquid temperature of 30 ° C. (product name: ADEKA, product name: 20% by mass solution of Tech CL-8), and the etched surface was photographed with an optical microscope. .
Of the above images, the dark portion indicates a region where the etching is made uniform. Therefore, the etching property was evaluated by comparing the photographed image with the reference image. FIG. 3 shows the correspondence between the reference image and the evaluation of etching property. The higher the area ratio of the dark part, the better the etching property, and the ◎ is the best etching property. If the etching property is A to Δ, it can be said that the etching property is good.

  The obtained results are shown in Tables 1 and 2.

As is clear from Tables 1 and 2, in each example satisfying 2.5 ≦ I {110} / I {112} ≦ 6.0, both the etching property and the flexibility of the rolled copper foil were excellent.
When Examples 1 and 2 having the same thickness and the same final recrystallization annealing condition are compared, Example 1 having a larger amount of Ag added has a larger (110) orientation, and I {110} / I {112 } Is also high. Further, in Examples 20 to 23 where 13.0> I {200} / I ₀ {200}, the flexibility is slightly lowered as compared with the other examples, but there is no practical problem.

On the other hand, compared to Example 6 in which the composition of the copper foil is the same, in Comparative Examples 1 and 4 in which the tension during the final recrystallization annealing was lowered, the (112) orientation was reduced, and I {110} / I {112 } Value exceeded 6.0 and the etching property deteriorated.
In the case of Comparative Example 2 in which the tension at the time of final recrystallization annealing is higher than that in Example 5 where the composition of the copper foil is the same, and at the time of final recrystallization annealing as compared with Example 7 where the composition of the copper foil is the same In Comparative Example 3 in which the tension was increased, the (110) orientation decreased, the value of I {110} / I {112} was less than 2.5, and the flexibility deteriorated.
In the case of Examples 1 and 6 in which the manufacturing method is the same, Example 1 in which the oxygen concentration of the copper foil is lower is more flexible.
2A and 2B are optical microscope images of the etched surfaces of Example 5 and Comparative Example 1, respectively. In Example 5 which is excellent in etching property, it turns out that there are many ratios of a dark part.

Claims (6)

It is a rolled copper foil containing 99.9% or more copper by mass,
When the calculated X-ray diffraction intensity from the {112} plane on the rolled surface is I {112} and the calculated X-ray diffraction intensity from the {110} plane is I {110},
Rolled copper foil satisfying 2.5 ≦ I {110} / I {112} ≦ 6.0.   The one or more selected from the group consisting of Ag, Sn, Mg, In, B, Ti, Zr and Au are contained in a total of 10 to 300 ppm by mass, and the balance is Cu and inevitable impurities. Rolled copper foil.   The rolled copper foil of Claim 1 or 2 which contains 2-50 mass ppm of oxygen.   The rolled copper foil according to claim 1, wherein I {112} ≦ 1.0 is satisfied on the rolled surface after heating at 200 ° C. for 30 minutes. After heating at 350 ° C. for 1 second, the {200} plane X-ray diffraction intensity of the rolled copper foil is I {200}, and the {200} plane X-ray diffraction intensity of the pure copper powder sample is I ₀ { 200}
The rolled copper foil according to claim 1, satisfying 5.0 ≦ I {200} / I ₀ {200} ≦ 27.0.   The rolled copper foil according to any one of claims 1 to 5, wherein the thickness is 4 to 70 µm.