JP5778460B2 - Rolled copper foil, method for producing the same, and copper-clad laminate - Google Patents

Description

  The present invention relates to a rolled copper foil suitable for a copper-clad laminate, a method for manufacturing the same, and a copper-clad laminate, for example, used in flexible printed circuits (FPCs).

A flexible wiring board (FPC) is formed by laminating a resin layer and a copper foil, and is preferably used for repeated bending portions. As a copper foil used for such FPC, a rolled copper foil excellent in flexibility is widely used. As a method for improving the flexibility of the rolled copper foil, a technique for developing a cubic texture after recrystallization annealing (Patent Document 1) and a technique for increasing the proportion of crystal grains penetrating in the thickness direction of the copper foil (patent) Reference 2) has been reported.
However, when manufacturing the FPC using these copper foils, if the surface (rolled surface) is etched to improve the adhesion to the coverlay, a depression with a diameter of about 20 μm will be generated on the surface (rolled surface). There is. This is attributed to the fact that the crystal orientation is controlled so that the cubic structure develops after the recrystallization annealing, and therefore crystal grains having different properties exist in the uniform structure. Since the etching rate of the metal differs depending on the crystal plane to be etched, the crystal grains are etched deeper than the surroundings, resulting in a large depression. This indentation causes the circuit etchability to deteriorate, or causes the appearance to be judged to be defective by appearance inspection and decreases the yield.

  Therefore, mechanical polishing is performed on the surface (rolled surface) of the copper foil before or after rolling to give strain, and this is used as a work-affected layer and is nonuniform on the surface (rolled surface) after recrystallization. There has been reported a technique (Patent Document 3) in which crystal grains are clustered and crystal grains having different properties alone do not exist.

Japanese Patent No. 3009383 JP 2006-117977 JP 2009-280855

  However, in the case of the technique described in Patent Document 3, there is a problem that a thin copper foil is broken by mechanical polishing or productivity is lowered. In addition, since the work-affected layer generated by mechanical polishing is as thin as 3 μm or less, there is a possibility that the work-affected layer itself may be scraped off due to excessive mechanical polishing. Is difficult. Furthermore, various equipment for mechanical polishing is required separately from rolling equipment for producing copper foil.

  That is, the present invention has been made to solve the above-described problems, and an object thereof is to provide a rolled copper foil having excellent flexibility and surface etching characteristics, a method for producing the same, and a copper-clad laminate. .

  As a result of various studies, the inventors of the present invention have made the final pass of the finish cold rolling of the copper foil material a low degree of processing, so that the outermost layer of the rolled copper foil has a stable processing structure different from the rolling texture. It was found that it can be formed. By recrystallizing this processed structure, non-uniform crystal grains are clustered on the surface of the copper foil (rolled surface), and the generation of a recess having a diameter of about 20 μm is suppressed.

That is, the rolled copper foil of the present invention comprises (A) tough pitch copper standardized to JIS-H3100 (C1100), (B) oxygen-free copper standardized to JIS-H3100 (C1020), and (C) Sn as an additive element from 100 to 100 500 ppm by mass and / or 100 to 200 ppm by mass of Ag, the balance being the tough pitch copper or the oxygen-free copper, or (D) Sn, Ag, In, Ti, Zn, Zr, It contains a total of 20 to 500 ppm by mass of one or more elements composed of Fe, P, Ni, Si, Ag, Te, Cr, Nb, and V, and the balance is the tough pitch copper or the oxygen-free copper. Rsm is the average length of contour curve elements specified in JIS-B0601 with I (200) / I0 (200) of 50 or more after annealing at 200 ° C for 0.5 hour and measured with a stylus type surface roughness meter When measured in the rolling parallel direction The ratio (RsmTD / RsmRD) of the measured value RsmRD and the value RsmTD measured in the direction perpendicular to the rolling (RsmTD / RsmRD) is 2.0 or more. When the area ratio occupied by the crystal grains is 20% or more and the length in the rolling direction is 0.5 mm in the rolling parallel cross section by SEM observation, the area ratio occupied by the crystal grains straddling the copper foil thickness center and having a major axis of 20 μm or less Is 20% or less of the observation field.
Here, I (200) / I0 (200) means the integrated intensity I (200) of the (200) plane diffraction peak of the sample in 2θ / θ measurement by X-ray diffraction method, and 2θ / θ measurement by X-ray diffraction method. Is a value divided by the integrated intensity I0 (200) of the (200) plane diffraction peak of the copper powder at, and is a value used as an index of the degree of assembly in the cube orientation. In other words, the above-mentioned rule that I (200) / I0 (200) is 50 or more indicates that the cube orientation is developed to a certain level or more.

On one surface of the copper foil (rolled surface) after removing 2 to 5% of the copper foil thickness by etching, a concave portion with a major axis exceeding 20 μm is observed when seven fields of 0.5 mm square of the surface (rolled surface) are observed. The number is preferably 0.5 pieces / mm ² or less.

  The method for producing a rolled copper foil of the present invention is a method for producing the rolled copper foil, wherein the copper foil material is cold-rolled at a final cold rolling degree of 97% or more, and in the final pass of the final cold rolling Cold rolling is performed at a pass degree of 2% or more and less than 10%.

Copper-clad laminate of the present invention, ing by laminating the rolled copper foil and a resin layer according to claim 1 or 2.

  According to the present invention, it is possible to stably obtain a rolled copper foil having excellent flexibility and excellent surface etching characteristics.

It is a figure which shows the method of measuring the surface (rolling surface) shape and processed structure of the rolled copper foil which concerns on embodiment of this invention. It is a figure which shows the optical microscope of the surface (rolling surface) after the etching of the sample of the comparative example 1. FIG.

  Hereinafter, the rolled copper foil which concerns on embodiment of this invention is demonstrated.

<Ingredient composition>
As the component composition of the copper foil, tough pitch copper (TPC) or oxygen-free copper (OFC) specified in JIS can be suitably used. Further, Sn as an additive element may be contained in an amount of 100 to 500 ppm by mass and / or Ag may be contained in an amount of 100 to 200 ppm by mass, and the remainder may be made of tough pitch copper or oxygen-free copper.
Further, it contains 20 to 500 ppm by mass in total of one or more elements consisting of Sn, Ag, In, Ti, Zn, Zr, Fe, P, Ni, Si, Ag, Te, Cr, Nb, and V as additive elements. The balance may be tough pitch copper or oxygen-free copper.
In addition, since the rolled copper foil used for FPC is requested | required of flexibility and the surface is etched, the thickness of the rolled copper foil is preferably 20 μm or less. Oxygen-free copper is standardized by JIS-H3100 (C1020), and tough pitch copper is standardized by JIS-H3100 (C1100).

<Crystal orientation>
The rolled copper foil of the present invention needs to have I (200) / I0 (200) of 50 or more after annealing at 200 ° C. for 0.5 hour. Annealing the rolled copper foil at 200 ° C for 0.5 hours produces a recrystallized structure. When I (200) / I0 (200) = 50, the cube texture (200) develops after the recrystallized annealing and the rolled copper This is an index for improving the flexibility of the foil. Therefore, a rolled copper foil whose I (200) / I0 (200) is less than 50 after annealing at 200 ° C. for 0.5 hour is not suitable as a highly flexible material in the first place.
As a method of setting I (200) / I0 (200) to 50 or more after annealing at 200 ° C. for 0.5 hour, the method described in Patent Document 1 can be employed. For example, the annealing immediately before the final cold rolling is performed under the condition that the average grain size of recrystallized grains obtained by this annealing is 5 to 20 μm, and the rolling degree in the final cold rolling is 90% or more. The annealing conditions can be carried out by heating at a temperature of 500 to 800 ° C. depending on the temperature for 5 to 600 seconds when annealing is performed in a continuous annealing furnace, and when annealing is performed in batches, It is carried out by heating at a temperature of 130 to 500 ° C. for 1 to 24 hours.

<Surface (rolled surface) shape>
As described later, the rolled copper foil of the present invention can be produced by lowering the degree of finish cold rolling, thereby forming a processed structure different from the rolled texture on the outermost layer of the rolled copper foil. The And by recrystallizing this processed structure, it becomes easy to cluster non-uniform crystal grains on the surface (rolled surface) of the copper foil, and the generation of a recess having a diameter of about 20 μm is suppressed.
In the rolled copper foil of the present invention, the shape of the surface (rolled surface) in which the generation of the dents is thus suppressed is defined as follows.

First, the value measured in the rolling parallel direction when the average length of the contour curve element defined in JIS-B0601 measured with a stylus type surface roughness meter is Rsm on the copper foil surface (rolled surface) after final rolling. The ratio (RsmTD / RsmRD) between RsmRD and the value RsmTD measured in the direction perpendicular to the rolling needs to be 2.0 or more. When finish cold rolling (skin pass) is performed at the above-described low degree of processing, streaky irregularities along the rolling direction L are generated on the surface (rolled surface) as shown in FIG. In this case, if the unevenness along the rolling direction L is small, the unevenness along the rolling perpendicular direction n is large, and (RsmTD / RsmRD) is 2.0 or more, finish cold rolling (skin pass) is performed at a low workability. it is conceivable that.
When (RsmTD / RsmRD) is less than 2.0, the skin pass at low workability has not been performed or the skin pass is insufficient, and a work structure different from the rolling texture should be sufficiently formed on the outermost layer of the rolled copper foil. Is difficult. The upper limit of (RsmTD / RsmRD) is not particularly specified, but is usually about 3.5.

<Processing organization>
And the difference between the processed structure of the outermost layer of the rolled copper foil and the rolled texture inside the rolled copper foil is defined by the surface ratio (rolled surface) of the rolled copper foil and the area ratio of crystal grains having a major axis of 20 μm or less inside. .
That is, as shown in FIG. 1, after annealing at 200 ° C. for 0.5 hour, in the region S within 0.5 mm square of the rolled copper foil surface (rolled surface) D, the area ratio occupied by crystal grains having a major axis of 20 μm or less is 20% or more. Furthermore, when the length in the rolling direction of 0.5 mm (symbol ML in FIG. 1) is observed by SEM in the rolling parallel section C, the area ratio occupied by crystal grains straddling the copper foil thickness center O and having a major axis of 20 μm or less is 20% or less of the observation field. In this way, when the rolled copper foil is etched by making the grains on the rolled copper foil surface (rolled surface) finer than the grains inside the rolled copper foil (reducing coarse grains having a major axis exceeding 20 μm). In addition, since a large number of fine crystals are dissolved at random, it is possible to suppress the coarse particles from being selectively dissolved to generate a dent having a diameter of about 20 μm.

Here, in FIG. 1, the rolling (parallel) direction is L, the rolling perpendicular direction (direction perpendicular to L) is N, and the thickness direction is T. The rolling parallel section C is a section parallel to the rolling (parallel) direction L and perpendicular to the rolling surface (parallel to T). The observation visual field V is a rectangular region represented by (rolled copper foil thickness t) × (rolling direction length ML) in the rolling parallel section C. Moreover, the copper foil thickness center O is a line passing through a thickness portion that is ½ of the thickness t of the rolled copper foil, and is parallel to the rolling surface.
The area ratio occupied by crystal grains having a major axis of 20 μm or less is determined as follows. First, in the observation visual field V, when crystal grains straddling the copper foil thickness center O are extracted, four crystal grains g1 to g4 are extracted as shown in FIG. Among these crystal grains g1 to g4, crystal grains having a major axis of 20 μm or less are g1, g2, and g4. Therefore, the area ratio is determined by {(total area of crystal grains g1, g2, g4) / (area of observation field of view V)} × 100. In addition, the area of the observation visual field V is represented by t × ML.

In the area S within 0.5 mm square of the rolled copper foil surface (rolled surface), the area ratio occupied by crystal grains having a major axis of 20 μm or less (area ratio of crystal grains having a major axis of 20 μm or less on the surface (rolled surface)) is less than 20%. If the area ratio occupied by crystal grains straddling the copper foil thickness center O and having a major axis of 20 μm or less (area ratio of crystal grains having a major axis of 20 μm or less inside) exceeds 20% of the observation field, rolled copper The crystal grains on the foil surface (rolled surface) are not sufficiently fine compared to the crystal grains inside the rolled copper foil, and when the rolled copper foil is etched, coarse grains on the surface (rolled surface) are selectively dissolved. An indentation with a diameter of about 20μm occurs.
In addition, I (200) / I0 (200) of the above-mentioned rolled copper foil, the surface ratio (rolled surface), and the area ratio of the crystal grains having a major axis of 20 μm or less are obtained after annealing the rolled copper foil at 200 ° C. for 0.5 hour. Value. And this annealing assumes the heat treatment at the time of lamination (simulation) in the process of laminating a rolled copper foil and a resin layer and manufacturing a copper clad laminated board (CCL). The area ratio of crystal grains having a major axis of 20 μm or less in the I (200) / I0 (200), surface (rolled surface) and inside is within the above range.

As described above, finish cold rolling (skin pass) is performed at a low workability so that (RsmTD / RsmRD) is 2.0 or more, and the surface of the rolled copper foil (rolled surface) and the inside of the crystal grains with a major axis of 20 μm or less By defining the difference in area ratio as described above, it is possible to suppress the occurrence of a depression having a diameter of about 20 μm by randomly dissolving a large number of fine crystals when the rolled copper foil is etched. Preferably, on one surface (rolled surface) of the copper foil after removing 2 to 5% of the copper foil thickness by etching, when the 0.5 mm square of the surface (rolled surface) is observed in seven visual fields, the major axis is 20 μm. The number of recesses exceeds 0.5 / mm ² . In addition, in the case of CCL manufactured using copper foil, resin is laminated | stacked on the single side | surface of copper foil, and this surface is not etched. Therefore, a concave portion is defined when one side of the rolled copper foil is etched by 2 to 5%.

Next, the manufacturing method of the rolled copper foil of this invention is demonstrated. First, a copper ingot having the above-described component composition is cast and hot-rolled. Thereafter, annealing and cold rolling are repeated to obtain a rolled sheet. The rolled sheet is annealed and recrystallized, and finally cold-rolled to a predetermined thickness to obtain a foil. At this time, the rolled sheet (copper foil material) is cold-rolled at a final cold rolling degree of 97% or higher, and cold rolled at a final pass of the final cold rolling of 2% or higher and lower than 10%. Apply. The final pass of final cold rolling corresponds to the final pass of finish rolling.
In the final pass of final cold rolling, the grain size on the surface of the rolled copper foil (rolled surface) is compared with the grain size inside the rolled copper foil by reducing the degree of one-pass processing to 2% or more and less than 10%. Can be made fine (reducing coarse grains having a major axis exceeding 20 μm), and the occurrence of a depression having a diameter of about 20 μm is suppressed as described above. On the other hand, in the final pass of the final cold rolling, if the degree of processing of one pass is 10% or more, it becomes too strong and the crystal grains on the surface of the rolled copper foil (rolled surface) are larger than the crystal grains inside the rolled copper foil. When the rolled copper foil is not sufficiently fine, coarse grains on the surface (rolled surface) are selectively dissolved to generate a dent having a diameter of about 20 μm. In the final pass of the final cold rolling, if the degree of processing for one pass is less than 2%, the processing becomes insufficient, and the crystal grains on the surface of the rolled copper foil (rolled surface) are compared with the crystal grains inside the rolled copper foil. And not fine enough.

There is no particular limitation on the method of performing cold rolling at a final pass of the final cold rolling of 1 pass processing degree of 2% or more and less than 10%, and if it is a commonly used rolling method, wet rolling using rolling oil, Any of dry rolling without using rolling oil may be used. Further, the final pass of the final cold rolling may be one pass, and may be a plurality of passes (final pass and previous pass) in accordance with the properties of the material to be rolled and the performance of the rolling mill.
In addition, the workability r of final cold rolling is defined by r = (t ₀ -t) / t ₀ (t: thickness after rolling, t ₀ : thickness before rolling).

  First, a copper ingot having the composition shown in Table 1 was manufactured and hot-rolled to a thickness of 10 mm. Then, annealing and cold rolling were repeated to obtain a rolled plate coil. The rolled plate was passed through a continuous annealing furnace at 750 ° C. and recrystallized. Then, it finally cold-rolled to the thickness of Table 1, and obtained copper foil. In addition, the processing degree of the final pass of final cold rolling was set as shown in Table 1.

<Rsm>
Measure the surface (rolled surface) of the obtained copper foil with a stylus type surface roughness meter (Surfcoder SE-3400 manufactured by Kosaka Laboratories) and measure the average length Rsm of the contour curve element specified in JIS-B0601 did. Rsm was measured along the rolling direction (RsmRD) and the direction perpendicular to the rolling direction (RsmTD), and the ratio (RsmTD / RsmRD) was calculated.

<Area ratio occupied by crystal grains having a major axis of 20 μm or less>
An optical microscope image of 0.5 mm square was photographed at three locations on the surface of the obtained copper foil (rolled surface), and the area ratio occupied by crystal grains having a major axis of 20 μm or less in the field of view was measured by image analysis. The average value was calculated. The major axis of the crystal grain means the diameter of the smallest circle (the smallest circumscribed circle of the crystal grain) surrounding the crystal grain.
Similarly, SEM (scanning electron microscope) images were taken at three locations in the rolling parallel section of 0.5 mm in the rolling direction length (observation field of view V), and the major diameter was 20 μm or less across the copper foil thickness center. Grains were extracted. And the area ratio which this crystal grain occupied to the observation visual field was measured by image analysis, and the average value of three places was computed. The major axis of the crystal grain is defined as described above.

<Orientation degree of 200 planes>
The obtained copper foil was annealed at 200 ° C. for 0.5 hour, and then the integral value (I) of (200) plane strength obtained by X-ray diffraction of the rolled surface was obtained. This value is divided by the integral value (I0) of the (200) plane strength of finely powdered copper (325 mesh, heated after heating at 300 ° C for 1 hour in a hydrogen stream), and I (200) / The value of I0 (200) was calculated. In addition, when I (200) / I0 (200) was 50 or more, the evaluation of the degree of orientation was good (◯), and less than 50 was rated as x. It is known that when I (200) / I0 (200) is 50 or more, cubic crystals grow and the flexibility is improved.

<Indentation on copper foil surface (rolled surface) after etching>
The obtained copper foil was annealed at 200 ° C. for 0.5 hour, then immersed in an etching solution (20% by mass solution of TECHKA CL-8 manufactured by ADEKA) for 2 minutes while being etched, etched and washed. The surface (rolled surface) was observed with an optical microscope. Seven fields of observation of a 0.5 mm square observation surface were evaluated, and a case where a depression (concave portion) having a major axis exceeding 20 μm was observed was evaluated as x, and a case where a concave portion having a major axis exceeding 20 μm was not observed was evaluated as “Good”. The major axis of the recess means the diameter of the smallest circle that surrounds the contour of the recess (the minimum circumscribed circle of the contour of the recess).
Here, if one recess having a major axis exceeding 20 μm is seen for 7 fields of view of 0.5 mm square, it is calculated that 0.57 / mm ² exists on the surface (rolled surface) (= 1 / (0.5 × 0.5 × 7)). Therefore, when the above evaluation is ○ (that is, when there are no dents whose major axis exceeds 20 μm), the number of concaves whose major axis exceeds 20 μm is 0.5 / mm ² or less (specifically, 0) on the surface (rolling surface). / mm ² ).
On the other hand, when the evaluation is x, the above-described calculation indicates that there are 0.57 or more recesses / mm ² on the surface (rolled surface).

  The obtained results are shown in Table 1.

  As is clear from Table 1, the final cold rolling work degree is 97% or more, and the final cold rolling final pass degree is 2% or more and 10% so that (RsmTD / RsmRD) ≧ 2.0. In the case of each example adjusted to less than, after annealing at 200 ° C. for 0.5 hour, the area ratio occupied by crystal grains having a major axis of 20 μm or less within 0.5 mm square of the surface (rolled surface) is 20% or more, and the rolling parallel section When the length in the rolling direction was 0.5 mm, the area ratio of the crystal grains having a major axis of 20 μm or less among the crystal grains straddling the copper foil thickness center was 20% or less. And even if it etched after annealing at 200 degreeC for 0.5 hour, the hollow exceeding a diameter of 20 micrometers did not generate | occur | produce on the surface (rolling surface). In each example, I (200) / I0 (200) was 50 or more after annealing at 200 ° C. for 0.5 hour.

In Comparative Examples 1 and 3, where the final pass of the final cold rolling is 10%, after annealing at 200 ° C for 0.5 hour, the crystal grains with a major axis of 20μm or less within 0.5mm square of the surface (rolled surface) The area ratio occupied by became less than 20%. Then, when the sample after annealing at 200 ° C. for 0.5 hour was etched, a depression exceeding 20 μm in diameter was generated on the surface (rolled surface). Since Comparative Examples 1 and 3 had different final thicknesses, the distribution of rolling passes before the final pass of final cold rolling was different, and the values of (RsmTD / RsmRD) were different. That is, in the case of Comparative Example 3, the final cold rolling is performed at a working degree of 10% or more until the final pass, and the foil thickness is thin, so the oil film equivalent in the final pass is increased, and the roughness anisotropy is increased. Since it became smaller, the value of (RsmTD / RsmRD) became less than 2.
In the case of Comparative Example 2 in which the workability of the final cold rolling was less than 97%, after annealing at 200 ° C. for 0.5 hour, I (200) / I0 (200) was less than 50 and the degree of orientation was inferior.
FIG. 2 shows an optical microscope image of a depression on the surface (rolled surface) of the sample of Comparative Example 1. It can be seen that a depression exceeding 20 μm in diameter has occurred on the surface.

Claims (4)

(A) Tough pitch copper standardized to JIS-H3100 (C1100), (B) oxygen-free copper standardized to JIS-H3100 (C1020), (C) containing 100 to 500 ppm by mass of Sn as an additive element, and / or Containing 100 to 200 ppm by mass of Ag, and the balance is Sn, Ag, In, Ti, Zn, Zr, Fe, P, Ni, Si, Ag as the tough pitch copper or oxygen-free copper, or (D) additive element , Te, Cr, Nb, V contains a total of one or more elements of 20 to 500 ppm by mass, the balance consists of the tough pitch copper or the oxygen-free copper,
Rsm is the average length of contour curve elements specified in JIS-B0601 with I (200) / I0 (200) of 50 or more after annealing at 200 ° C for 0.5 hour and measured with a stylus type surface roughness meter When the ratio of the value RsmRD measured in the rolling parallel direction to the value RsmTD measured in the direction perpendicular to the rolling (RsmTD / RsmRD) is 2.0 or more,
After annealing at 200 ° C for 0.5 hour, the area ratio of the crystal grains with the major axis of 20μm or less in the 0.5mm square of the surface (rolled surface) is 20% or more, and the rolling parallel length of 0.5mm is observed by SEM In this case, the rolled copper foil has an area ratio occupied by crystal grains having a major axis of 20 μm or less straddling the copper foil thickness center and 20% or less of the observation field. On one surface of the copper foil (rolled surface) after removing 2 to 5% of the copper foil thickness by etching, a concave portion with a major axis exceeding 20 μm is observed when seven fields of 0.5 mm square of the surface (rolled surface) are observed. The rolled copper foil according to claim 1, which is 0.5 pieces / mm ² or less. The method for producing a rolled copper foil according to claim 1 or 2, wherein the copper foil material is cold-rolled at a final cold-rolling degree of 97% or more, and in the final pass of the final cold-rolling, the degree of one-pass processing is 2. A method for producing a rolled copper foil, which is subjected to cold rolling of not less than 10% and less than 10%. A copper-clad laminate obtained by laminating the rolled copper foil according to claim 1 or 2 and a resin layer .