JP4716520B2 - Rolled copper foil - Google Patents

Description

  The present invention relates to a copper foil having excellent flexibility suitable for a flexible printed circuit board (FPC) for bending.

  In recent years, a flexible printed circuit board (FPC) in which a copper foil is laminated on a resin substrate has been widely used for mounting electronic components. Since the FPC has flexibility, it is often used for electrical connection of movable parts such as electric devices, and the copper foil constituting the FPC is required to be flexible.

For this reason, a technique for improving the flexibility by smoothing the copper foil surface has been reported (see Patent Document 1). According to this technology, when the flexibility is improved, the cube orientation, which is the recrystallized texture of copper, develops, and the strength (I) of the 200 plane obtained by X-ray diffraction is X-ray diffraction of fine powder copper. It is described that the relationship of I / I ₀ > 40 is satisfied with respect to the strength (I ₀ ) of 200 planes obtained in ( ₁ ).
Further, as a rolled copper foil having excellent flexibility, one having I / I ₀ > 20 with respect to I ₀ of the rolled surface after annealing at 200 ° C. for 30 minutes is disclosed (see Patent Document 2). ).
On the other hand, a rolled copper foil having a thickness of 20 μm or less that achieves I / I ₀ > 50 by performing recrystallization annealing at a temperature higher by 50 ° C. than the semi-softening temperature in order to improve the thinning etching property has been reported (Patent Document). 3).

Japanese Patent Laid-Open No. 2001-58203 JP 2002-167632 A Japanese Patent Laid-Open No. 2003-193211

When manufacturing CCL (Copper Clad Laminate: copper clad laminate) using copper foil, resin is generally weaker to heat than copper, and therefore heat treatment conditions at a low temperature or for a short time are required. Specifically, for 3-layer CCL that uses an adhesive to bond the copper foil and resin film, heat treatment conditions are typically about 140 ° C for about 1 hour, and for 3-layer CCL that does not use an adhesive at 350 ° C for about 10 minutes. Is.
However, in the case of the techniques described in Patent Documents 2 and 3, the orientation of the 200 plane is adjusted by annealing for 30 minutes at around 200 ° C. (the semi-softening temperature of the tough pitch copper foil is about 120 to 130 ° C.). There is a risk of thermal effects on the resin. On the other hand, in the case of the techniques described in Patent Documents 2 and 3, when the heat treatment is performed at a low temperature for a short time, the structure of 200 planes is not sufficiently obtained and the flexibility is not improved.
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a rolled copper foil capable of improving the flexibility by orienting the structure on the 200 plane even by annealing for a short time.

In order to achieve the above object, the rolled copper foil of the present invention is made of tough pitch copper (JIS-C1100) or oxygen-free copper (JIS-C1011) specified in JIS , and is a rolled surface after annealing at 350 ° C. for 10 minutes. When the intensity of the (200) plane obtained by X-ray diffraction is I and the intensity of the (200) plane obtained by X-ray diffraction of fine powder is I ₀ , I / I _O ≧ 65 It is characterized by.

The rolled copper foil of the present invention contains 0.5% by mass or less of one or more selected from the group of Ag, Sn, and Mg, the balance is made of Cu and inevitable impurities, and the rolled surface after annealing at 350 ° C. for 10 minutes is used. When the intensity of the (200) plane obtained by X-ray diffraction is I and the intensity of the (200) plane obtained by X-ray diffraction of fine powder is I ₀ , I / I _O ≧ 65 Features.

In the present invention, it is preferable that at least one mass selected from the group consisting of Ag, Sn and Mg is contained in an amount of 0.1% by mass or more and I / I _O ≧ 70. When viewed from a cross section in the rolling parallel direction, the number of shear bands intersecting the center line in the thickness direction is preferably 100 or less per observation region having a length 100 times the thickness. It was preferable that the degree of processing in the final rolling step was 95% or more.

  According to the present invention, it is possible to improve the flexibility by orienting the structure on the 200 plane even by short-time annealing.

  Hereinafter, embodiments of the rolled copper foil according to the present invention will be described. In the present invention, “%” and “ppm” mean mass% and mass (mass) ppm, respectively, unless otherwise specified.

<Composition>
Rolled copper foil according to the first invention consists of tough pitch copper of standards JIS (JIS-C1100) or oxygen-free copper (JIS-C 1011).
In the first invention, the conductivity can be improved by the above composition .

The rolled copper foil according to the second invention contains at least 500 mass ppm of one or more selected from the group consisting of Ag, Sn and Mg, with the balance being Cu and inevitable impurities. When Ag, Sn, or Mg is added, the orientation to the (200) plane is likely to be strong, and I / _IO described later can be set to 65 or more, and the flexibility can be improved.
When the total concentration of one or more selected from the group of Ag, Sn, and Mg exceeds 500 mass ppm, the brass-type texture becomes a stable orientation, so that a cubic orientation texture ((200) orientation) that contributes to bending develops. No, I / I _O is less than 65. On the other hand, the lower limit of the total concentration of these elements is about the analysis level of the elements, and it is sufficient that these elements are included even in a slight amount.
In particular, when the total concentration is in the range of 100 to 500 mass ppm, I / I _O ≧ 70 can be achieved, and the flexibility can be further improved.

<I / I _O >
It is described in Patent Documents 2 and 3 that the flexibility improves when the orientation of the copper foil on the rolled surface is increased to the (200) plane. Here, when the strength of the (200) plane obtained by X-ray diffraction of the rolled surface is I, and the strength of the (200) plane obtained by X-ray diffraction of fine powder copper (random orientation) is I ₀ , The higher the I / I _O value, the stronger the (200) plane orientation.
In general, it is said that a rolling workability of 60% or more is necessary to form a rolling texture. In the present invention, it is necessary to increase the workability of the final rolling.
However, as described in Patent Documents 2 and 3, if the recrystallization annealing condition is around 200 ° C. (the semi-softening temperature of the tough pitch copper foil is about 120 to 130 ° C.) for 30 minutes, the rolling degree is increased. Therefore, it is easy to strengthen the orientation to the (200) plane, but in the case of short-time annealing (350 ° C. for 10 minutes) as in the present invention, it is possible to simply increase the degree of rolling to the (200) plane. It is difficult to strengthen the orientation of The reason for this is the influence of the shear band generated in rolling at a high workability, which will be described later.
In addition, when rolling at a high degree of work, recrystallization of the material may occur due to processing heat during rolling, but when a large number of the above-mentioned shear bands occur in the material, recrystallization becomes non-uniform and uniform rolling aggregation Since the development of the tissue is inhibited, it is still difficult to increase the degree of (200) orientation after annealing.

Therefore, in the present invention, by suppressing the development of the shear band as described below, even if the recrystallization annealing is performed at 350 ° C. for 10 minutes, the I / I _O can be made 65 or more, (200) Flexibility can be improved by increasing the degree of orientation. When I / I _O is less than 65, the degree of (200) orientation does not increase and the flexibility does not improve. Preferably, I / I _O is 70 or more.

<Shear band>
In order to develop a recrystallized texture by annealing, the rolled texture before annealing needs to be developed uniformly. Here, the metal material undergoes slip deformation when rolled, but when deformed at a high degree of work, non-uniform deformation due to plastic instability occurs and shear bands occur. The shear band refers to a thin planar structure inclined by 30 to 60 degrees with respect to the rolled plate surface. (For example, "Iron and Steel" 70th year (1984) No.15 P.18)
The shear band has a crystal orientation almost similar to that of the surrounding matrix, but has a dense cell structure and recrystallization nucleation is likely to occur. Therefore, in a material with a developed shear band, recrystallization occurs unevenly between the shear band and the matrix, and as a result, the development of the recrystallized texture is hindered.
Thus, even if the rolling degree is increased unnecessarily, the degree of orientation to the (200) plane decreases due to the development of the shear band, and the orientation to the (200) plane cannot be increased by short-time annealing.

As described in Patent Documents 2 and 3, when sufficient annealing is performed at 200 ° C. (or semi-softening temperature + 50 ° C.) for 30 minutes, the shear band disappears regardless of the number of occurrences, Grows until recrystallized grains become uniform equiaxed grains. For this reason, there is no influence of the shear band, and the degree of orientation to the (200) plane increases. However, the heat treatment time generally performed in the two-layer CCL processing step is about 10 minutes, and annealing for as long as 30 minutes is not realistic.
Therefore, even if the material has a high degree of orientation to the (200) plane by annealing at 200 ° C for 30 minutes, if the number of shear bands after rolling is large, it is uniform in short-time annealing (350 ° C for 10 minutes) A recrystallized structure cannot be obtained, and the (200) orientation degree cannot be increased to improve the flexibility. This is because if the number of shear bands is large, the shear bands will not disappear after 10 minutes of short-term annealing.
In order to obtain sufficient flexibility, after annealing at 350 ° C. for 10 minutes, the shear band is 30 or less / (100 times the copper foil thickness), preferably 20 or less / (100 times the copper foil thickness). There must be. Thus, in order to suppress the number of shear bands, the number of shear bands after rolling needs to be 100 or less / (100 times the copper foil thickness).
Here, “/ (100 times the thickness of the copper foil)” means 100 or less per observation region having a length 100 times the thickness, which will be described in detail later.

As described above, in the present invention, the orientation to the (200) plane is successfully strengthened by short-time annealing by increasing the rolling degree while suppressing the development of the shear band.
As a method for suppressing the development of the shear band, the viscosity of the rolling oil during cold rolling can be reduced. In general, the rolling oil cools the rolling roll and reduces the rolling resistance by forming an oil film between the roll and the material. The oil film also plays a role of transmitting the rolling load from the roll to the material. Therefore, in general, rolling is performed under the condition that the oil film thickness is increased in order to facilitate rolling.
However, when the oil film thickness is thick, the material surface is deformed without being constrained in the oil film, so that a shear band is easily developed. The higher the rolling oil viscosity, the larger the rolling roll diameter, and the higher the rolling speed, the thicker the oil film, so that the shear band is likely to develop. Further, if the surface roughness of the rolling roll is rough, the oil film is locally thick and the shear band is easily developed. In addition, the shear band develops as the degree of work increases, and when the rolling degree reaches 90% or more, the shear band develops dramatically. When adding a degree of rolling greater than 95%, the shear band increases the foil thickness. To penetrate.
For this reason, as a method for suppressing the development of the shear band, rolling is performed with a thin oil film thickness, that is, the viscosity of the rolling oil is lowered, the rolling roll diameter is reduced, and the rolling speed is reduced. Moreover, you may make the surface roughness of a rolling roll small, or make a workability small.

  However, in the present invention, in order to increase the degree of (200) orientation, it is necessary to increase the degree of processing, and from the viewpoint of productivity, the rolling speed is preferably as fast as possible. Therefore, it is preferable to reduce the viscosity of the rolling oil, to reduce the rolling roll diameter, and to reduce the surface roughness of the rolling roll so as to uniformly control the oil film thickness during rolling and suppress the development of the shear band. . Specifically, the viscosity of the rolling oil is 6 cSt or less, preferably 4 to 5 cSt, the diameter of the rolling roll is 40 mm to 150 mm, and the surface roughness of the rolling roll is about Ra ≦ 0.05 μm, so that even at high workability, the shear band Can be obtained.

In the final cold rolling, it is possible to carry out rolling under the above conditions in all passes, but it is preferable to carry out under the above rolling conditions in a pass with a working degree of 80% or more. This is because the rolling conditions described above deteriorate the rolling performance, and if rolling is performed under the above conditions in all passes, the number of passes increases in the rolling to the target thickness, and the productivity tends to decrease. Because there is. For example, in a pass up to a processing degree of 90%, using a rolling oil having a high viscosity and using a rolling roll having a large surface roughness, large processing can be taken and high productivity can be maintained.
However, the present invention is not limited to the above rolling conditions, and other methods (for example, control of the rolling temperature) may be adopted as long as the development of the shear band can be suppressed.

As described above, in the present invention, for example, by controlling the rolling oil flow rate and temperature, and the crystal grain size before rolling, recrystallization during processing is suppressed and the occurrence of shear bands is reduced, and the texture is developed. Let Thereby, even if it anneals for a short time (350 degreeC for 10 minutes), the orientation to (200) plane becomes strong.
According to the second aspect of the present invention, the effect of suppressing recrystallization during processing can be further exhibited by adding one or more selected from the group consisting of Ag, Sn, and Mg.

<Identification of shear band>
In the shear band, a structure formed by intensive shear deformation on the rolling surface and a surface inclined by 30 to 60 degrees due to plastic instability due to strong processing appears on the observation surface. Therefore, the shear band is observed as a discontinuous surface of the rolled structure. Since the crystal orientation of the shear band portion is not different from the parent phase, the shear band cannot be defined by crystal orientation measurement.
On the other hand, since the shear band extends in the depth direction, it can be specified by observing the cross section of the material. Therefore, when the cross section in the rolling parallel direction of the copper foil after the final rolling is observed, a discontinuous portion of the rolled structure inclined by 30 to 60 degrees is defined as a shear band. Specifically, an image of a microscope (metal microscope, scanning electron microscope (SEM), scanning ion microscope (SIM)) of the above-mentioned cross section is obtained, and the rolling surface and a line inclined by 30 to 60 degrees are obtained by image analysis or visual observation. It can be determined as a shear band. The cross-section processing of the copper foil is preferably performed by FIB or CP, but a method such as mechanical polishing may be used. In addition, it is preferable to use SIM for cross-sectional observation because the crystal orientation contrast appears strongly.

In the present invention, among the shear bands determined as described above, the number of shear bands intersecting with the center line in the thickness direction of the foil is preferably 100 or less per observation region 100 times the thickness. .
FIG. 1 shows a SIM image of a structure as viewed from a cross section in the rolling parallel direction. In this figure, a line connecting two arrows represented by symbol Sh is a shear band.
FIG. 2 is a schematic view of a copper foil cross section showing a shear band of the copper foil cross section. In this figure, the square frame R corresponds to the SIM image of FIG. When the thickness of the foil is t, the observation region reaches a length of t × 100 along the rolling parallel direction. The significant shear band Sh is a line whose one end reaches the copper foil surface and the other end intersects the center line C in the thickness direction of the foil, and other shear bands (not reaching the copper foil surface or center In the present invention, the shear band that does not intersect the line C is not counted as a shear band because the influence on the development of the recrystallized texture is small. Within the observation region, if the number of significant shear bands is 100 or less, the development of recrystallized texture is not hindered because there are few shear bands, and the orientation to the (200) plane becomes stronger. .

(Manufacturing)
The copper foil of this invention can be manufactured as follows, for example. First, an ingot is produced by melting a composition in which electrolytic copper or oxygen-free copper is used as a main raw material and adding the above chemical components and the like as necessary in a melting furnace. A rolled copper foil is obtained by sequentially performing, for example, homogenization annealing, hot rolling, cold rolling, annealing, cold rolling, and annealing on the ingot. Cold rolling is preferably performed at a workability of 90% or more, for example, and more preferably 95% or more.

  EXAMPLES Next, although an Example is given and this invention is demonstrated further in detail, this invention is not limited to these.

1. Sample preparation Each element of the composition shown in Table 1 is added to electrolytic copper and melted in vacuum to cast an ingot. This is homogenized and annealed at a temperature of 800 ° C for 3 hours. Thereafter, hot rolling was performed. Further, the surface was cut and cold-rolled to prepare a copper foil sample having a plate thickness of 17 μm. The total rolling work degree of cold rolling, the viscosity of the rolling oil, the roughness (Ra) and the diameter of the rolled work roll (WR) were set to the values shown in Table 1.

<Evaluation>
(1) Number of shear bands The cross section in the rolling parallel direction of the copper foil sample after final rolling was mechanically polished to obtain a cross-sectional image by a scanning ion microscope (SIM). The observation area of this image is visually observed as a length 100 times the thickness in the rolling parallel direction, and as shown in FIG. 1 and FIG. 2, among the lines inclined by 30 to 60 degrees with the rolling surface (discontinuous portion of the rolling structure) The number of lines intersecting the center line in the thickness direction of the foil was counted.
The number of shear bands is as follows: a sample as-rolled, a sample obtained by annealing a sample after rolling in an Ar atmosphere at 350 ° C. for 10 minutes, and a sample obtained by annealing in the air at 50 ° C. higher than the semi-softening temperature of the sample for 30 minutes. Was counted for each.
The semi-softening temperature was determined as the annealing temperature when the tensile strength after annealing reached an intermediate value between the tensile strength after rolling and the tensile strength after annealing at 300 ° C for 30 minutes and completely softening. .
(2) Calculation of I / I _O The strength of the (200) plane obtained by X-ray diffraction (RINT2000, Rigaku Co., Ltd.) on the rolled surface of the copper foil sample is I, and fine powder copper (Random orientation Kanto Science Co., Ltd.) I / I 2 _O was calculated by measuring the intensity of the (200) plane obtained by X-ray diffraction of 325 mesh) as I ₀ . The higher I / I _{O, the} stronger the orientation to the (200) plane and the better the flexibility.
In addition, calculation of I / I 2 _O of each sample was performed after annealing for 10 minutes at 350 ° C., and after annealing for 30 minutes at a temperature 50 ° C. higher than the semi-softening temperature.

(3) Flexibility After applying polyimide (U varnish A varnish A) on the copper foil surface and drying in the atmosphere for 30 minutes at 130 ° C, a cure heat treatment in an Ar atmosphere at 350 ° C for 10 minutes is performed. It went and produced the resin copper foil laminated material. The laminated material was etched with ferric chloride to form a bending test circuit pattern, which was used as a bending sample.
This sample was evaluated by the same method as that performed in the example of Japanese Patent Laid-Open No. 2000-212661 (see paragraphs 0034 and 0035 of FIG. 1 and FIG. 1). However, at the time of bending, the copper foil surface was set to the bending inner side.
The change in the electrical resistance of the sample during the bending test was measured, and the flexibility was evaluated by the number of bendings until the electrical resistance increased by 10% from the initial value. The evaluation criteria were ◯ when the number of bendings was 30000 times or more and x when less than 30000.

  The obtained results are shown in Tables 1 and 2.

As is apparent from Tables 1 and 2, in each example, the number of shear bands is 100 or less / (100 times the copper foil thickness) even when rolled, and 350 ° C. × 10 minutes. Even after short-time recrystallization annealing, the I / I _O was 65 or more and the flexibility was good.
In particular, in Examples 2 to 7 in which Ag, Sn, or Mg was added as an additive element, I / _IO was improved to 70 or more, which was superior to that of Example 1 of the pure copper type.

On the other hand, in the case of Comparative Examples 3 to 5 and 7 to 9 in which the rolling oil viscosity is higher than that in the Examples, in the case of Comparative Example 2 in which the roughness of the rolled work roll is higher than that in the Examples, the diameter of the rolled work roll is higher than that in the Examples. In Comparative Example 2, the number of shear bands after rolling exceeded 100 / (100 times the copper foil thickness). As a result, in the case of these comparative examples, I / I _O was less than 65 in short-time recrystallization annealing at 350 ° C. for 10 minutes, and annealing was performed for a long time (30 minutes at 50 ° C. higher than the semi-softening temperature). For the first time, I / I _O increased to over 65.
Further, in the case of Comparative Example 1 in which the rolling oil viscosity is higher than that of the example and the roughness of the rolled work roll is higher than that of the example, the I / I even when annealed for a long time (30 ° C. higher than the semi-softening temperature for 30 minutes). _O remained below 65.

In the case of Comparative Example 10 in which the rolling degree is lower than that of the example, the number of shear bands after rolling was as small as 100 or less / (100 times the copper foil thickness), but because of the low degree of working, annealing was performed for a long time (half I / I _O remained below 65 even after 30 minutes at 50 ° C. above the softening temperature.
In the case of Comparative Example 11 in which the added amount of Ag exceeded 500 mass%, the number of shear bands after rolling increased beyond 100 / (100 times the copper foil thickness) and annealed for a long time (50 ° C. above the semi-softening temperature). Even at high temperature (30 minutes), I / I _O remained below 65.

Since the shear bands disappear in the process of growing the recrystallized grains, the number of shear bands in the examples and comparative examples was 0 when annealing was performed for 30 minutes at a softening temperature of + 50 ° C.
On the other hand, in each comparative example, the flexibility was inferior, but in each comparative example, the number of unrolled shear bands was larger than in the examples, and I / I _O after annealing at 350 ° C. for 10 minutes. Also, it was low compared to the examples. From this, it is understood that the flexibility is correlated with the number of shear bands as rolled and I / _IO after annealing at 350 ° C. for 10 minutes.

It is a figure which shows the SIM image of a structure | tissue when it sees from the cross section of a rolling parallel direction. It is a schematic diagram of the copper foil cross section which shows the shear band of a copper foil cross section.

Explanation of symbols

t Copper foil thickness C Thickness center line Sh (significant) shear band

Claims (5)

It consists of tough pitch copper (JIS-C1100) or oxygen-free copper (JIS-C1011) that conforms to JIS, and the strength of the (200) plane obtained by X-ray diffraction after annealing for 10 minutes at 350 ° C is I. A rolled copper foil, wherein I / I _O ≧ 65 when the strength of the (200) plane obtained by X-ray diffraction of fine powder copper is I ₀ . One or more kinds selected from the group of Ag, Sn and Mg are contained in an amount of 500 mass ppm or less, and the balance consists of Cu and inevitable impurities, and the rolling surface after annealing at 350 ° C. for 10 minutes was determined by X-ray diffraction (200) the intensity of the surface and I, when the strength of that determined by X-ray diffraction (200) plane of the finely powdered copper was I _0, rolled copper foil, which is a I / I _O ≧ 65. The rolled copper foil according to claim 2, comprising 100 mass ppm or more selected from the group consisting of Ag, Sn and Mg, wherein I / I _O ≥70.   The number of shear bands intersecting with the center line in the thickness direction when viewed from the cross section in the rolling parallel direction is 100 or less per observation region having a length 100 times the thickness. Rolled copper foil according to crab.   The rolled copper foil according to any one of claims 1 to 4, wherein the rolled copper foil is manufactured with a working degree in the final rolling step of 95% or more.