JP2001323354A - Rolled copper foil and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] An object of the present invention is to provide a method for producing a rolled copper foil in which a cubic texture is remarkably developed when recrystallization annealing is performed. In a process for producing a copper foil, a tough pitch copper or oxygen-free copper ingot is hot-rolled, then cold-rolled and annealed repeatedly, and finally cold-rolled to a predetermined thickness. The annealing immediately before the final cold rolling was measured by X-ray diffraction on the rolled surface of the material after the annealing, when the average grain size of the recrystallized grains obtained by this annealing was 30 μm or less (200), (220) , (311) and the diffraction intensity of the (111) _{plane, 3 ≦ I (200) /} I 0 (200) ≦ 10, I (220) / I 0 (220) ≦
_{1, I (311) / I} 0 (311) ≦ 1, I (111) / I 0 (111) ≦ 1 (I (hkl): X -ray diffraction integrated intensity of the measured rolling surface (hkl) plane, I _{0 (hkl)} : X-ray diffraction integrated intensity of the (hkl) plane measured with fine powdered copper).
(2) A method for producing a rolled copper foil in which a cubic texture is remarkably developed after recrystallization annealing, wherein a rolling degree in the next final cold rolling is 93% or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rolled copper foil in which a cubic texture is remarkably developed when recrystallization annealing is performed. This copper foil is used for flexible printed circuit boards (Flexible printed circuit boards) that require high flexibility.
It is suitable for use in flexible wiring members such as t).

[0002]

2. Description of the Related Art When a copper plate or copper foil manufactured by rolling is recrystallized and annealed, a cubic texture ((100) [001] orientation) is developed. Cubic texture has various effects on the properties of copper. The advantages of the cubic texture development include low strain / high cycle fatigue properties (10% fatigue life).
⁴ times or more). From this point of view, Patent No. 3009383 uses a copper foil having a developed cubic texture as a material for a flexible printed circuit (FPC), which requires bending fatigue characteristics. As a measure to develop the cubic texture, the workability in the final rolling should be 90% or more, and the recrystallized grain size obtained by annealing before the final rolling should be 5%.
It is proposed to adjust to ~ 20 μm.

However, recently, there has been a demand for a manufacturing process capable of further developing a cubic texture. For example, in the case of copper foil for FPC, with the miniaturization of the equipment, the bending deformation given to the FPC became more severe, and a superior flex life was required for the copper foil. The thickness of copper foil is 3
The mainstream was 5 μm, but recently thinner ones of 18 μm, 12 μm, and 9 μm have been used. As the copper foil becomes thinner, even if the copper foil is manufactured by the same process, the development degree of the cubic texture is reduced.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a rolled copper foil in which a cubic texture is remarkably developed when recrystallization annealing is performed.

[0005]

The present inventor has conducted intensive studies on a manufacturing process capable of stably obtaining an extremely developed cubic texture. In this study, the final rolling degree was set to 93% or more, and the effect of the structure before final rolling (recrystallized structure obtained by annealing before final rolling) on the development of cubic texture was examined. As a result, it was found that developing a cubic texture in the recrystallized structure before the final rolling resulted in a more developed cubic texture when rolling and annealing for recrystallization.

[0006] This is because, when copper having a developed cubic texture is rolled, a band structure having a cubic orientation is formed at a high frequency in the worked structure after rolling, and when the copper is annealed, the band structure is sharpened starting from the band structure. It was speculated that this was due to the formation of a cubic texture (Yoshi Fukutomi, Taichi Kamishiro: Light Metal, Vol. 47, No. 2, pp. 123-130). It has been known that the crystal grain size before the final rolling is preferably smaller in order to develop the cube texture of the copper foil (Japanese Patent No. 3009383). It is a new finding that the degree of tissue development has a significant effect.

The present invention has been completed based on the above findings, and has optimized a method for producing a rolled copper foil in which a cubic texture is remarkably developed when recrystallization annealing is performed. That is, as a first invention, in a manufacturing process of a rolled copper foil in which tough pitch copper or oxygen-free copper ingot is hot-rolled, then cold rolling and annealing are repeated, and finally finished to a predetermined thickness by cold rolling. (1) The annealing immediately before the final cold rolling was measured by X-ray diffraction on the rolled surface of the material after the annealing when the average grain size of the recrystallized grains obtained by this annealing was 30 μm or less (200), (220), (311) and the diffraction intensity of the (111) _{plane, 3 ≦ I (200) /} I 0 (200) ≦ 10, I (220) / I 0 (220) ≦
_{1, I (311) / I} 0 (311) ≦ 1, I (111) / I 0 (111) ≦ 1 (I (hkl): X -ray diffraction integrated intensity of the measured rolling surface (hkl) plane, I _{0 (hkl)} : X-ray diffraction integrated intensity of the (hkl) plane measured with fine powdered copper).
(2) A method for producing a rolled copper foil in which a cubic texture is remarkably developed after recrystallization annealing, wherein a rolling degree in the next final cold rolling is 93% or more.

According to a second aspect of the present invention, the integrated intensity (I ₍₂₀₀₎ ) of 200 planes determined by X-ray diffraction on the rolled surface after recrystallization annealing performed after the final cold rolling is determined by the X-ray diffraction of fine copper powder. Determined by 200
For the integrated intensity of the surface (I _{0 (200)} ), I ₍₂₀₀₎ / I _0
(200) A rolled copper foil having a thickness of 18 μm or less, produced by the method of Invention 1, wherein ≧ 40. As invention 3,
A rolled copper foil manufactured by the method of Invention 1, which is a material for a flexible printed circuit board.

The present invention is effective for a copper foil having a thickness of 18 μm or less. This is because, as described above, when the copper foil becomes thinner, the degree of development of the cubic texture decreases, and particularly when the thickness becomes 18 μm or less, the conventional process (Patent No. 3009383) develops the cubic texture to a desired level. This is because it becomes difficult. If the above method is adopted, the thickness becomes 18
Even for copper foils of μm or less, after recrystallization annealing, I ₍₂₀₀₎ /
A cubic texture of I _{0 (200)} ≧ 40 can be stably obtained. A rolled copper foil in which a cubic texture is remarkably developed after recrystallization annealing is particularly suitable as a material for a flexible printed circuit board.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the reason for defining the production process of rolled copper foil in the present invention will be described below. (1) Copper foil material : Since the present invention aims to develop a cubic texture during annealing, copper whose recrystallization texture has a cubic orientation, that is, tough pitch copper (oxygen concentration
100-500 wt ppm) and oxygen-free copper (oxygen concentration 10 wt ppm)
Below) is the target of the material. On the other hand, copper containing a large amount of alloying elements is not suitable as a raw material because the action of alloying elements hinders the development of cubic orientation. However,

[0011] To prevent softening during storage at room temperature, tough pitch copper (Japanese Patent Application No. 11-9437) in which a small amount of Ag or the like is added to adjust the softening temperature to an appropriate range. Oxygen-free copper containing a small amount of alloying elements (Japanese Patent No. 1582981,
040, Japanese Patent Publication No. 62-47936, Patent No. 1849316, JP-A-63-1
40052, JP-A-63-45339, JP-A-1-319640, Patent No. 2737
954) Oxygen-free copper whose softening temperature is adjusted to an appropriate range by adjusting the amount of impurities (JP-A-1-319641, JP-A-1-19393)
2, materials such as Japanese Patent Application No. 11-9332) can be used. This means that even if the alloy element is contained, it is in a very small concentration range (0.1 wt.
% Or less) does not hinder the development of cubic texture.

(2) Final rolling work ratio: The reason for setting the work ratio to 93% or more is that if the work ratio is less than 93%, even if the annealing conditions before rolling are adjusted, cubic aggregates will not be formed even after annealing. This is because the tissue does not develop to the desired level. (3) Grain size obtained by annealing before final rolling : The reason that the average grain size of recrystallized grains is 30 μm or less is that the crystal grain size is 30 μm.
Is exceeded, the cubic texture does not develop to the desired level in annealing after rolling, even if the crystal orientation before rolling is controlled and the final rolling degree is 93% or more. In addition,
From the same point of view, Patent No. 3009383 specifies the average grain size of recrystallized grains to be 20 μm or less, but if the degree of development of cubic texture is adjusted as described below, an average grain size of 30 μm can be tolerated .

(4) Cube obtained by annealing before final rolling
Development of the _{texture: I (200) / I 0} (2 00) The reason for defining a value to 3 or more, cubic texture in annealing after rolling and the value reaches 3 or higher is to develop significantly . On the other hand, if the value of I ₍₂₀₀₎ / I0 ₍₂₀₀₎ exceeds 10, the recrystallized grains grow abnormally and the average grain size exceeds 30μm, and the development of cubic texture during annealing after rolling decreases rather That's why. _{I (220) / I 0 (} 22 0), I (311) / I 0 (311) and
The reason that each value of I ₍₁₁₁₎ / I _{0 (111)} is specified to be 1 or less is that when these values exceed 1, the cubic texture in annealing after rolling decreases in the degree of development. The I / I ₀ value as described above can be obtained by adjusting the previous rolling degree and the preceding annealing conditions. That is, I ₍₂₀₀₎ / I _{0 (200)} is increased by increasing the rolling degree and reducing the crystal grain size during annealing, and I ₍₂₂₀₎ / I _0
(220) , I ₍₃₁₁₎ / I _{0 (311)} and I ₍₁₁₁₎ / I _{0 (111)}
Can be lowered. In addition, the recrystallization annealing specified in (3) and (4) can also be performed by hot rolling.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. The tough pitch copper plate (oxygen content 250 ppm) or oxygen-free copper plate (oxygen content 2 ppm) after recrystallization annealing with a thickness of t ₀ mm and a width of 600 mm and having various crystal grain sizes and crystal orientations was used as a test material. ) Was used. After cold rolling this copper plate to a thickness of t mm, it was annealed and recrystallized. Here, the working ratio d in the cold rolling, is given by _{d = (t 0 -t) /} t 0 × 100 (%) ( where t ₀ is the thickness of the before cold rolling). The annealing for recrystallizing the rolled copper foil was performed by heating the sample at a temperature 70 ° C. higher than the half-softening temperature for 30 minutes. Here, the semi-softening temperature is the annealing temperature at which the tensile strength after annealing has an intermediate value between the tensile strength after rolling and the tensile strength after complete softening, and the annealing time is 30 minutes. This temperature was measured first.

The grain size of the copper foil before rolling was measured by a cutting method (JISH0501) at a cross section perpendicular to the rolling direction. X-ray diffraction was performed on the copper foil before rolling and the copper foil after recrystallization annealing after rolling. Furthermore, the bending life was evaluated on the assumption that the copper foil of the present invention was used as a material for FPC. The details of the X-ray diffraction and bending test methods are shown below.

(1) X-ray diffraction By X-ray diffraction, (200), (220), (311) and
The X-ray intensity of each surface of (111) and (111) was determined. This value must be
Divided by the integrated intensity of each surface of fine copper powder
I₍₂₀₀₎/ I_{0 (200)}, I₍₂₂₀₎/ I_0 (220), I₍₃₁₁₎/ I_0 
(311) And I ₍₁₁₁₎/ I_0 (111)Was determined. X-ray diffraction
Was performed using a Co tube, and the integrated value of the peak intensity was (20
0): 2θ = 57-63 °, (220): 2θ = 86-91 °, (311): 2
θ = 107-113 °, (111): 2θ = 47-55 ° (θ is the diffraction angle
Degree).

(2) Bending test Assuming that the sample was used as a copper foil for FPC, the sample was recrystallized and annealed under the above conditions, and then the bending fatigue life was measured by the apparatus shown in FIG. This device has an oscillation driver 4
The copper foil under test 1 is fixed to the apparatus at a total of four points: the screw 2 indicated by the arrow and the tip of the screw 3. When the vibrating part 3 is driven up and down, the middle part of the copper foil 1 is bent into a hairpin shape with a predetermined radius of curvature r. In this test, the number of times to break when bending was repeated under the following conditions was determined. The measurement was performed five times for the same material, and the average value was obtained. Specimen width 12.7 m
m, Specimen length: 200 mm, Specimen sampling direction: Sampling so that the longitudinal direction of the specimen is parallel to the rolling direction, radius of curvature
r: 2.5 mm, vibration stroke: 25 mm, vibration speed: 1500 times / minute

Table 1 shows the processing history and characteristics of the evaluated samples.

[0019]

[Table 1]

In the rolled copper foil according to the present invention, a remarkably developed cubic texture of I ₍₂₀₀₎ / I0 ₍₂₀₀₎ ≧ 40 is obtained by recrystallization annealing after rolling. On the other hand, No. 1 of the comparative example
Is because the I ₍₂₀₀₎ / I _{0 (200)} value obtained by annealing before rolling is less than 3, and No. 2 of the comparative example is obtained by annealing before rolling.
When the value of I ₍₂₀₀₎ / I0 ₍₂₀₀₎ exceeds 10, recrystallized grains grow abnormally, and the grain size exceeds 30 μm.
The value of I ₍₂₀₀₎ / I _{0 (200)} obtained by recrystallization annealing after rolling is reduced. No. 3 and No. 4 of the comparative examples were obtained from I ₍₂₂₀₎ / I _{0 (220)} or I _{(31 1)} / I obtained by annealing before rolling.
_{Since 0 (311)} exceeds 1, the value of I ₍₂₀₀₎ / I _{0 (200)} obtained by recrystallization annealing after rolling decreases. N in Comparative Example
In o.5, since the rolling degree is less than 93%,
In o.6, since the grain size obtained by annealing before rolling exceeds 30 μm, I ₍₂₀₀₎ / I obtained by recrystallization annealing after rolling
_{0 (200) The} value has dropped.

FIG. 2 shows the relationship between the I ₍₂₀₀₎ / I0 ₍₂₀₀₎ value and the flex life, with the data stratified by the thickness of the copper foil. I ₍₂₀₀₎
It can be seen that the higher the / I _{0 (200)} value, the longer the flex life. Note that the thinner the copper foil, the longer the flex life, but the less the strain applied to the surface of the bent portion.

[0022]

As the rolled copper foil becomes thinner, the degree of development of the cubic texture decreases. In particular, when the thickness becomes 18 μm or less, it becomes difficult to develop the cubic texture to a desired level by the conventional process. According to the method of the present invention, even when the thickness of the copper foil is 18 μm or less, the
₍₂₀₀₎ / I _{0 (200)} Cubic texture at a level of ≧ 40 can be stably obtained. A rolled copper foil in which a cubic texture is remarkably developed after recrystallization annealing is particularly suitable as a material for a flexible printed circuit board.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a bending test used for measuring a bending fatigue life.

FIG. 2 is a diagram showing the relationship between I (200) / Io (200) after rolling and recrystallization and flex life.

[Explanation of symbols]

 1. Copper foil 2. Screw 3. Vibration transmitting member 4. Oscillation driver

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Claims (3)

[Claims] In a process for producing a copper foil, a tough pitch copper or oxygen-free copper ingot is hot-rolled, cold-rolled and annealed repeatedly, and finally cold-rolled to a predetermined thickness. ) The annealing immediately before the final cold rolling was measured by X-ray diffraction on the rolled surface of the material after this annealing, when the average grain size of the recrystallized grains obtained by this annealing was 30 μm or less (200), (220) ), (311) and (diffraction intensity of 111) plane _{is, 3 ≦ I (200) /} I 0 (200) ≦ 10, I (220) / I 0 (220) ≦
_{1, I (311) / I} 0 (311) ≦ 1, I (111) / I 0 (111) ≦ 1 (I (hkl): X -ray diffraction integrated intensity of the measured rolling surface (hkl) plane, I _{0 (hkl)} : X-ray diffraction integrated intensity of the (hkl) plane measured with fine powdered copper).
(2) A method for producing a rolled copper foil in which a cubic texture is remarkably developed after recrystallization annealing, wherein a rolling degree in the next final cold rolling is 93% or more. 2. An integrated intensity (I) of 200 planes determined by X-ray diffraction on a rolled surface after recrystallization annealing performed after final cold rolling.
₍₂₀₀₎ ) is characterized by I ₍₂₀₀₎ / I _{0 (200)} ≧ 40 with respect to the integrated intensity (I _{0 (200)} ) of 200 planes obtained by X-ray diffraction of fine copper powder. A rolled copper foil having a thickness of 18 μm or less, produced by the method of claim 1. 3. A rolled copper foil manufactured by the method of claim 1, wherein the rolled copper foil is a material for a flexible printed circuit board.