JP2004256879A - Rolled copper foil having high elongation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolled copper foil which has high elongation when the foil is recrystallization-annealed, and further has a flat surface when etched in order to reduce the foil thickness. <P>SOLUTION: The rolled copper foil, when recrystallization-annealed, develops a texture in which the intensity (I) of a rolled face (200) determined by X-ray diffraction has such a relation with the intensity (I<SB>0</SB>) of the face (200) on the fine powder of copper determined by the X-ray diffraction, as to satisfy I<SB>(200)</SB>/I<SB>0(200)</SB><1.0. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００２９】
表１に実施例の評価結果を示す。Ｎｏ．１〜９は発明例であり、Ｎｏ．１０〜２２は成分または圧延上がりの板面方位が請求の範囲から外れる比較例である。比較例のうち、Ｎｏ．１０は無酸素銅であり、Ｎｏ．２１および２２は、Ｓｎを添加する代わりにＡｇを添加したもので、Ｎｏ．２１のＡｇ濃度は０．０２０ｍａｓｓ％、Ｎｏ．２２のＡｇ濃度は０．１４６ｍａｓｓ％である。
発明例のＮｏ１〜８は、再結晶焼鈍後における板面方位が、請求項１を満たしており、いずれも２０％以上の高い伸びが得られ、また、再結晶後の結晶粒が微細なためエッチング面の粗さが小さい。
【００３０】
一方、比較例のＮｏ．１０はＳｎを添加していないため、Ｎｏ．１１はＳｎ濃度が０．０１ｍａｓｓ％に満たないため、最終圧延後の結晶方位が規定を外れ、再結晶後に立方体集合組織が著しく発達している。このため伸びが２０％より低く、また再結晶後の結晶粒が粗大なためエッチング面の粗さが大きい。Ｓｎの代わりにＡｇを添加したＮｏ．２１および２２、また、Ｓｎを添加しても、最終圧延後の結晶方位が規定を満たしていないＮｏ．１３〜２０についても、同様の結果になっている。
【００３１】
Ｎｏ．１２はＳｎ濃度が０．２ｍａｓｓ％を超えたため、伸びが高くエッチング面の粗さも小さいが、導電率が８０％を下回り、高導電性が求められるコイルなどの用途には不適当である。
なお、圧延上がりの板面方位には、上述した圧延条件のほか、圧延機自体の特性（構造、剛性等）も影響を及ぼす。また、厚み、幅、機械的特性、表面粗さ等の材料要因も影響を及ぼす。したがって、圧延上がりの板面方位は、圧延条件によって、一義的に決定されるものではないが、参考までに、厚みとＳｎ濃度が同等である発明例Ｎｏ．４と比較例Ｎｏ．１６について、圧延条件を対比すると、次の通りであった。
・圧延ロールの直径（ｍｍ）… Ｎｏ．４：５０、Ｎｏ．１６：５０。
・１パスあたりの加工度（％）… Ｎｏ．４：４３．７、Ｎｏ．１６：６８．３。
・圧延張力（ＭＰａ）… Ｎｏ．４：１００、Ｎｏ．１６：１５０。
・圧延油の温度（℃）… Ｎｏ．４：３０、Ｎｏ．１６：２５。
【００３２】
【発明の効果】
本発明の銅箔は、再結晶焼鈍が施した際に、高い伸びを発現する。このため極細線のコイル、フレキシブルプリント回路基板、過酷な曲げ加工を必要とする微小部品等の用途として好適である。また、減肉のためのエッチング処理を施したときに平滑な表面が得られるので、ファインピッチ加工のために減肉エッチング処理を施されるフレキシブルプリント回路基板等に対しては、特に好適である。[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolled copper foil having high elongation and a method for manufacturing the same, and a flexible printed circuit board (Flexible Printed Circuit), a flexible wiring member such as a multilayer flexible printed circuit board, and a small motor. The present invention provides a rolled copper foil having a high elongation suitable for a coil material such as a foil-wound coil for a transformer, a foil-wound coil for a transformer, and a wire covering material.
[0002]
[Prior art]
FPCs are frequently used in electronic circuits of electronic devices. FPCs are characterized by their flexibility, and are used as wiring for movable parts, and are also used as space-saving wiring materials because they can be folded and stored in electronic devices. . The FPC is obtained by forming a copper wiring pattern on a copper-clad laminate obtained by attaching a copper foil to a resin film of polyimide or the like by etching.
[0003]
In recent years, electronic devices have become thinner and more compact, and more severe bending deformation has been applied to FPCs. There are two types of FPCs, three-layer copper-clad laminates and two-layer copper-clad laminates. In a three-layer material, an adhesive is used to bond a copper foil and a resin film, whereas in a two-layer material, a polyimide film and a copper foil are integrated without using an adhesive. For this reason, the two-layered material is thinner than the three-layered plate, and is excellent in bendability by being thin. Therefore, a two-layered material tends to be used for an FPC particularly requiring flexibility.
The two-layer material is manufactured by a “casting method” in which a varnish containing a polyamic acid, which is a precursor of a polyimide resin, is applied on a copper foil and cured by heating, and a “laminating method” in which the copper foil is directly laminated on a polyimide film. And so on. The copper foil is recrystallized and softened by the heat history in this manufacturing process. In order to further improve the bendability of the two-layered material, it is required that the copper foil, which is a constituent material of the copper-clad laminate, increase the elongation after recrystallization and improve the bendability.
[0004]
In addition, the width and spacing of copper wiring in FPC are becoming smaller. In order to make such copper wiring finer, it is essential to make the copper foil thinner. That is, the thickness of the copper foil conventionally used for the flexible substrate has been mainly 18 μm or 12 μm, but recently a copper foil having a thickness of 9 μm or thinner has been required. However, it is difficult to manufacture a rolled copper foil having a thickness of 10 μm or less in an industrially stable manner, and it is also difficult to handle the copper foil in the process of manufacturing a copper-clad laminate. Therefore, for example, a flexible board having a copper circuit thickness of 6 μm may be manufactured by a process in which a copper-clad laminate is first manufactured using 12 μm copper foil, and the thickness of the copper foil is reduced to 6 μm by etching. Many. It is required that the surface of the copper foil be uniformly etched for this etching treatment (hereinafter, thinning etching). The reason for this is that if the etching proceeds unevenly, irregularities will occur on the surface after etching. Therefore, when applying a resist to the copper foil surface prior to circuit etching (hereinafter, circuit etching), the gap between the copper foil and the resist film will be lost. This is because air bubbles are generated in the liquid crystal and the circuit shape after etching deteriorates.
[0005]
Improvement of the elongation of the copper foil is required for uses other than FPC. For example, a laminated material in which a copper foil is laminated on a synthetic resin material and adhered is used for an electric wire covering material. The elongation of the copper foil decreases as the thickness decreases. Even when using copper foil annealed at a temperature equal to or higher than the softening point to increase elongation, when a very thin copper foil is wound around an electric wire as a wire covering material, there is a problem that the copper foil is cracked and breaks. .
Conventionally, the material of the copper foil for the above applications is mainly tough pitch copper (oxygen content 100 to 500 mass ppm) or oxygen-free copper (oxygen content 10 mass ppm or less), and the ingot is hot-rolled and then cold-rolled. And the intermediate annealing is repeated, and processed into a foil having a thickness of 9 to 35 μm by final rolling. In order to obtain higher elongation when annealing the rolled copper foil, in the copper foil manufacturing process, various conditions of the intermediate annealing are changed, and it is attempted to adjust the rolling degree after the final annealing. However, when the thickness of the copper foil was 10 μm or less, it was difficult to obtain an elongation exceeding 10%.
[0006]
On the other hand, a copper foil in which elongation is enhanced by adding 0.05 to 0.35% by mass of Ag to tough pitch copper has been proposed (for example, see Patent Document 1). However, even in the copper foil obtained by this method, the elongation when the copper foil having a thickness of 8 μm is annealed does not exceed 10%.
When pure copper is recrystallized and annealed, a cubic texture ((100) plane, [001] orientation) develops. By increasing the workability in the final rolling and reducing the crystal grain size in the annealing immediately before the final rolling in the copper foil manufacturing process, the cubic texture is further developed after the recrystallization annealing. Even in a copper foil obtained by adding a small amount of Ag to tough pitch copper, a tendency to develop a cubic texture by the same manufacturing process is recognized. As the degree of development of the cubic texture increases, the tensile strength and elongation of the foil simultaneously decrease. Focusing on the morphology of the crystal grains after recrystallization annealing, the copper foil in which the cubic texture has developed becomes coarse recrystallized grains that are rounded and elongated in the rolling direction.
[0007]
[Patent Document 1]
JP-A-11-140564 [0008]
[Problems to be solved by the invention]
An object of the present invention is to provide a rolled copper foil capable of obtaining a high elongation when the foil is subjected to recrystallization annealing and further obtaining a smooth surface when subjected to an etching treatment for reducing the thickness.
[0009]
[Means for Solving the Problems]
The present inventors made an ingot obtained by adding a trace element to oxygen-free copper, perform cold rolling and intermediate annealing after hot rolling, and finally finish the foil by cold rolling, and a thickness of 18 μm or less. Was produced. In this process, the types and amounts of the added elements, the rolling conditions, and the like were variously changed, and the effects of these conditions on elongation after recrystallization annealing were examined. As a result, it has been found that in a copper foil obtained by adding Sn to oxygen-free copper, high elongation is obtained when the foil is recrystallized and annealed. In the copper foil from which high elongation was obtained, the degree of development of the cube orientation, which is a recrystallization texture of pure copper, was extremely low.
[0010]
Therefore, the present inventors focused on the relationship between the crystal orientation and the elongation of the rolled copper foil subjected to the recrystallization annealing, and accumulated and analyzed the data. As a result, they found that the copper foil in which the degree of assembling of the (200) plane on the rolled surface was suppressed to a predetermined level had better elongation after recrystallization annealing than the conventional copper foil. In other words, they found a way to improve elongation in ultra-thin copper foil.
[0011]
Since the Young's modulus of a metal crystal changes depending on the crystal orientation, the elastic deformation behavior of the metal material changes depending on the crystal orientation. Further, since a metal crystal has a unique slip plane and slip direction, the plastic deformation behavior of the metal material also changes depending on the crystal orientation. Although the details of the mechanism by which the degree of cubic orientation affects the elongation of the material are not clear, it seems that the deformation behavior of the metallic material is related to the dependence on the crystal orientation.
Furthermore, the present inventors have found that it is not enough to add Sn only to sufficiently suppress the degree of aggregation of the (200) plane, and also controls the crystal orientation before recrystallization annealing (final rolling). I knew it was necessary.
[0012]
In addition, the present inventors have proposed a copper foil to which Sn is added for a copper-clad laminate in Japanese Patent Application No. 2002-50700. However, the present invention relates to a case where the copper foil is used in a rolled-up structure state. , The composition of copper foil, the structure, etc. are optimized. On the other hand, in the present invention, when the rolled copper foil is used after recrystallization annealing, the component and the structure are optimized mainly for the purpose of increasing the elongation after recrystallization.
On the other hand, since the growth rate of the recrystallized grains oriented in the cubic orientation is extremely high, the recrystallized grains become coarse in a copper foil in which a cubic texture develops during recrystallization annealing. Therefore, when the development of the cubic texture is suppressed, the crystal grains become finer. Due to the refinement of the crystal grains, the effect of smoothing the etched surface when the thinning etching was performed was also obtained. The unevenness of the etched surface is generated in units of crystal grains due to the difference in orientation between adjacent crystal grains. When the crystal grains become finer, the pitch of the unevenness is reduced, and the surface is smoothed.
[0013]
The present inventors have proposed, in Japanese Patent Application No. 2001-395774, to extremely develop a cubic texture for smoothing a thinned etched surface. This is intended to eliminate the difference in orientation between adjacent crystal grains. The etching surface smoothing according to the present invention utilizes a different mechanism.
That is, the present invention
(1) By performing recrystallization annealing, the intensity (I) of the (200) plane of the rolled surface determined by X-ray diffraction is changed to the intensity (I ₀ ) of the (200) plane determined by X-ray diffraction of fine copper powder. )
I ₍₂₀₀₎ / I0 ₍₂₀₀₎ <1.0
Rolled copper foil, characterized by the development of a texture that is
(2) 0.01 to 0.2 mass% of Sn is contained, the sum of Sn and Cu is 99.9% or more, and (111), (200), and (200) of the rolled surface obtained by X-ray diffraction 220), the intensity (I) of the (311) plane is different from the intensity (I ₀ ) of each plane obtained by X-ray diffraction of fine powder copper.
0.01 <I ₍₁₁₁₎ / I0 ₍₁₁₁₎ <0.1
0.15 <I ₍₂₀₀₎ / I0 ₍₂₀₀₎ <1.0
2.5 <I ₍₂₂₀₎ / I0 ₍₂₂₀₎ <5.5
0.2 <I ₍₃₁₁₎ / I0 ₍₃₁₁₎ <0.6
Rolled copper foil,
(3) The rolled copper foil according to claim 1 or 2, wherein the thickness is 20 µm or less, and an elongation of 20% or more is obtained after recrystallization annealing.
[00014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the reasons for limiting each element constituting the present invention will be described.
(1) Crystal orientation after recrystallization annealing The crystal orientation of the copper foil subjected to recrystallization annealing is as follows:
I ₍₂₀₀₎ / I0 ₍₂₀₀₎ <1.0
With this relationship, a high elongation can be obtained, and the etched thinned surface is smoothed. Here, I _(hkl) and I _{0 (hkl)} are the X-rays of the (hkl) plane measured by using an X-ray diffractometer on the rolled surface of copper foil and fine powder copper (random orientation sample), respectively. This is the integral value of the intensity.
[0015]
(2) When Sn is added to the copper material Cu, the stacking fault energy decreases, and the development of the (200) cubic texture is suppressed. However, if the Sn concentration is less than 0.01 mass%, the above crystal orientation cannot be obtained after recrystallization annealing even if the crystal orientation after rolling is adjusted as described below. On the other hand, when Sn exceeds 0.2 mass%, the electrical conductivity is less than 80%, and it is not suitable for applications requiring high electrical conductivity.
[0016]
On the other hand, there are two types of Cu serving as a base to which Sn is added: oxygen-free copper having an oxygen concentration of 0.005 mass% or less and tough pitch copper having an oxygen concentration of 0.02 to 0.05 mass%. In the present invention, Sn is added to oxygen-free copper. When Sn is added to tough pitch copper, Sn and oxygen form a compound, so when the copper foil is pulled, breakage starts from these particles, and high elongation cannot be expected. According to JIS-H3100 (1999), the composition of oxygen-free copper C1020 is defined as Cu being 99.6 mass% or more.
[0017]
(3) Crystal orientation after final rolling In order to obtain the above crystal orientation after recrystallization annealing, in the final rolling (before recrystallization annealing), four main surfaces of the copper alloy ((220), (111) ), (200) and (311))
0.01 <I ₍₁₁₁₎ / I0 ₍₁₁₁₎ <0.1
0.15 <I ₍₂₀₀₎ / I0 ₍₂₀₀₎ <1.0
2.5 <I ₍₂₂₀₎ / I0 ₍₂₂₀₎ <5.5
0.2 <I ₍₃₁₁₎ / I0 ₍₃₁₁₎ <0.6
Need to be adjusted. Unless adjusted to this range, even if 0.01 mass% or more of Sn is added, a desired crystal orientation cannot be obtained after recrystallization annealing.
[0018]
(4) Thickness of foil The thickness of the foil obtained by final rolling was set to 20 μm or less, and more preferably 5 to 18 μm. When the thickness of the foil is less than 5 μm, handling becomes difficult such as wrinkling or tearing when processing into various parts. On the other hand, when the thickness exceeds 20 μm, it becomes difficult to adopt the material for a coil or the two-layer CCL which requires a reduction in size.
[0019]
(5) If the elongation of 20% or more is obtained stably, it can be judged that the elongation is clearly improved compared to the conventional copper foil, and the design of parts is changed, and the copper foil is applied to a new use. Becomes possible. In addition, the temperature of the recrystallization annealing of the Sn-containing copper foil according to the present invention is preferably approximately in the range of 350 to 450 ° C. If the temperature is lower than this temperature, an unrecrystallized region exists, and if the temperature is higher than this temperature, crystal grains become coarse, and in any case, a desired elongation cannot be obtained.
[0020]
(6) Manufacturing process The manufacturing process for obtaining the crystal orientation after the final annealing is not particularly limited. However, in order to increase the strength of the finished roll, after the ingot is hot-rolled, cold rolling and annealing are repeated, and finally, in a process of finishing the foil by cold rolling, the working degree of the last cold rolling is set to 85. % Or more, and the crystal grain size obtained by annealing just before the last cold rolling is preferably 20 μm or less. The cold rolling degree (R) is defined as t ₀ before rolling, and t after rolling,
_{R = (t 0 -t) /} t 0 × 100 (%)
Is defined by
[0021]
【Example】
Hereinafter, an embodiment of the present invention will be described with reference to Examples. A predetermined amount of Sn is added to molten copper whose O concentration has been reduced to 5 mass ppm or less by carbon deoxidation, and the components shown in Table 1 have a thickness of 200 mm and a width of 600 mm. Of copper ingots. After hot rolling the ingot, annealing and cold rolling were repeated, and finally, a foil having a predetermined thickness was finished by cold rolling at a working ratio of 90%. The recrystallization annealing before the final rolling was performed under the condition that the crystal grain size was about 15 μm. The crystal grain size after annealing was measured by a cutting method in a cross section perpendicular to the rolling direction.
[0022]
In order to change the crystal orientation after the final rolling, the diameter of the rolling roll, the degree of rolling per pass, the rolling tension, and the temperature of the rolling oil were variously changed. The following trends were observed in these rolling conditions and the orientation of the sheet surface after rolling.
-If the diameter of the rolling roll is increased, the strength of the (311) plane decreases.
-If the rolling degree per pass is increased, the strength of the (200) plane decreases.
-When the rolling oil temperature is lowered, the strength of the (111) plane increases.
-If the rolling tension is increased, the strength of the (220) plane increases.
First, the half-softening temperature when the annealing time was 30 minutes was determined for the copper foil after the final rolling. Then, annealing was performed at a temperature 50 ° C. higher than the half-softening temperature for 30 minutes to recrystallize the copper foil. Here, the semi-softening temperature refers to the annealing when the tensile strength is intermediate between the value before annealing and the value after complete softening (in the present embodiment, the value after annealing at 500 ° C. for 30 minutes). Temperature.
[0023]
The following evaluation was performed about the above-mentioned copper foil sample.
(1) Sheet plane orientation after rolling The integrated value (I) of the strength of the (111), (200), (220) and (311) planes was determined by X-ray diffraction on the surface of the copper foil after rolling. This value was divided by the integral value (I ₀ ) of each surface strength of the fine powder copper measured in advance to calculate the value of I / I ₀ . In the measurement of the integrated value of the peak intensity, a Co tube was used, and 2θ (θ was a diffraction angle) was performed in the following range.
(111): 48-53 °
(200): 57-62 °
(220): 86-91 °
(200): 108-113 °
Similarly, for the sample after recrystallization annealing, the integrated intensity ratio I / I ₀ of the (200) plane was determined.
[0024]
(2) Grain size after recrystallization Regarding the sample after recrystallization annealing, the rolled surface is chemically polished after mirror polishing, and is completely formed by a line segment of a predetermined length according to a cutting method (JIS H 0501 (1999)). The crystal grain size was determined by a method of counting the number of crystal grains cut into pieces.
[0025]
(3) Elongation The elongation of the sample after recrystallization annealing was determined by a tensile test.
As a tensile test piece, a strip having a width of 12.7 mm and a length of 150 mm was used, the tensile speed was fixed at 50 mm / min, and the elongation after breaking was measured. The gauge length for elongation measurement was 50 mm.
[0026]
(3) Conductivity With respect to the sample after the recrystallization annealing, the specific resistance was measured using a constant voltage DC potentiometer, and the conductivity (IACS%) was obtained. The same test specimen as the tensile test specimen was used.
[0027]
(4) Etching test An aqueous solution of sodium persulfate having a temperature of 50 ° C. and a concentration of 100 g / L was sprayed onto the surface of the sample at a pressure of 2 kg / cm 2, and the sample was etched in the depth direction so that the thickness became half. Thereafter, the maximum height (Ry) of the surface was determined using a contact roughness meter according to JIS B0601 (1999). The reference length was 0.8 mm, and the measurement was performed in a direction parallel to the rolling direction. The measurement of Ry was performed five times at different locations, and the maximum value of the five measurements was obtained.
[0028]
[Table 1]

[0029]
Table 1 shows the evaluation results of the examples. No. Nos. 1 to 9 are invention examples. Nos. 10 to 22 are comparative examples in which the component or the plane orientation after rolling is out of the claims. Among the comparative examples, No. No. 10 is oxygen-free copper; In Nos. 21 and 22, Ag was added instead of Sn. The Ag concentration of No. 21 was 0.020 mass%. The Ag concentration of No. 22 is 0.146 mass%.
In Nos. 1 to 8 of the invention examples, the sheet plane orientation after recrystallization annealing satisfies claim 1, and all have high elongation of 20% or more, and the crystal grains after recrystallization are fine. The roughness of the etched surface is small.
[0030]
On the other hand, in Comparative Example No. No. 10 did not contain Sn, and In No. 11, since the Sn concentration was less than 0.01 mass%, the crystal orientation after final rolling was out of the specified range, and the cubic texture was remarkably developed after recrystallization. Therefore, the elongation is lower than 20%, and the roughness of the etched surface is large because the crystal grains after recrystallization are coarse. No. 3 containing Ag instead of Sn. Nos. 21 and 22, and even when Sn was added, the crystal orientation after final rolling did not satisfy the regulation. Similar results are obtained for 13 to 20.
[0031]
No. Sample No. 12 has a high elongation and a small roughness of the etched surface because the Sn concentration exceeds 0.2 mass%, but has an electric conductivity of less than 80% and is unsuitable for applications such as coils requiring high electric conductivity.
Note that, in addition to the above-described rolling conditions, the characteristics (structure, rigidity, and the like) of the rolling mill itself also affect the orientation of the sheet surface after rolling. Material factors such as thickness, width, mechanical properties, and surface roughness also have an effect. Therefore, although the sheet orientation after rolling is not uniquely determined by the rolling conditions, for reference, the invention example No. having the same thickness and Sn concentration is referred to. 4 and Comparative Example No. 4. The rolling conditions of No. 16 were as follows.
-Rolling roll diameter (mm) ... No. 4:50, no. 16:50.
-Degree of processing per pass (%) ... No. 4: 43.7, No. 16: 68.3.
-Rolling tension (MPa) ... No. 4: 100, no. 16: 150.
-Temperature of rolling oil (° C) ... 4:30, no. 16:25.
[0032]
【The invention's effect】
The copper foil of the present invention exhibits high elongation when subjected to recrystallization annealing. For this reason, it is suitable for use as a coil of a fine wire, a flexible printed circuit board, and a micro component requiring severe bending. In addition, since a smooth surface is obtained when an etching process for thinning is performed, it is particularly suitable for a flexible printed circuit board or the like that is subjected to a thinning etching process for fine pitch processing. .

Claims (3)

By performing recrystallization annealing, the strength (I) of the (200) plane obtained by X-ray diffraction of the rolled surface is different from the intensity (I ₀ ) of the (200) plane obtained by X-ray diffraction of the fine powder copper. ,
I ₍₂₀₀₎ / I0 ₍₂₀₀₎ <1.0
Rolled copper foil characterized by the development of texture It contains 0.01 to 0.2 mass% of Sn, the total of Sn and Cu is 99.9% or more, and further, (111), (200), (220), The intensity (I) of the (311) plane is different from the intensity (I ₀ ) of each plane obtained by X-ray diffraction of fine copper powder.
0.01 <I ₍₁₁₁₎ / I0 ₍₁₁₁₎ <0.1
0.15 <I ₍₂₀₀₎ / I0 ₍₂₀₀₎ <1.0
2.5 <I ₍₂₂₀₎ / I0 ₍₂₂₀₎ <5.5
0.2 <I ₍₃₁₁₎ / I0 ₍₃₁₁₎ <0.6
A rolled copper foil, characterized in that: The rolled copper foil according to claim 1, wherein the rolled copper foil has a thickness of 20 μm or less and has an elongation of 20% or more after recrystallization annealing.