JP2014077182A - Rolled copper foil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolled copper foil capable of inhibiting the formation of surface unevenness on soft-etching or half-etching occasions.SOLUTION: The provided rolled copper foil is a rolled copper foil having a primary surface constituted by multiple crystal faces, scheduled to be used past a recrystallization step, and having the following characteristics: in a case where, after a recrystallization step of heating for 30 min by elevating the temperature to 200°C so as to induce the recrystallization of all particles of the rolled copper foil, the area ratio, with respect to the primary surface, of the (200) face on the primary surface obtained based on the EBSP (Electron Backscatter Diffraction Pattern) method is defined as R, the Ris below 20%, and the maximal dimension of the multiple crystal faces constituting the primary surface is 100 μm or below.

Description

  The present invention relates to a rolled copper foil, and more particularly to a rolled copper foil used for a flexible printed wiring board.

  A flexible printed circuit (FPC) has bending characteristics and bending characteristics, and is used as a wiring material for movable parts such as a hinge part and a slide part of a mobile phone. Further, the FPC is used as a bent wiring material in order to reduce the size and space of a smartphone.

  The FPC is manufactured, for example, by bonding a copper foil and a base material such as a synthetic resin, and performing surface processing such as etching on the copper foil to form a wiring.

  As a copper foil used for FPC, for example, there is a rolled copper foil. The rolled copper foil is manufactured by subjecting a copper material to rolling such as cold rolling, and has a crystal structure distorted by rolling. Although the rolled copper foil is hard due to the distorted crystal structure, it has low bending characteristics and bending characteristics, but it exhibits excellent bending characteristics and bending characteristics when heated and recrystallized. In the case of using a rolled copper foil for FPC, heating is performed when the rolled copper foil and the base material are bonded together, and the recrystallization of the rolled copper foil is simultaneously performed by this heating.

  By the way, in the rolled copper foil used for FPC, the required characteristics differ between the one surface bonded to the base material and the other surface to which the resist or the like adheres. One surface is required to have an adhesive force with a base material, and surface treatment such as roughening treatment is performed. The other surface is required to have resist adhesion or the like, and surface treatment such as soft etching is performed. According to the soft etching, the resist adhesion is improved by removing the oxide film formed on the surface of the rolled copper foil and flattening the surface. Thus, in a rolled copper foil, a separate process is given by the surface.

  However, in the above-described soft etching, a concave portion may be formed on the surface of the rolled copper foil. This phenomenon is called dishdown, and dishdown impairs the surface flatness of the rolled copper foil and reduces resist adhesion. The dishdown indicates that the etching does not progress uniformly in the thickness direction of the surface of the rolled copper foil, that is, the etching rate on the surface of the rolled copper foil is different. The difference in etching rate is caused by a plurality of crystal planes on the surface of the rolled copper foil having different crystal orientations.

  The rolled copper foil having dishdown on the surface has low resist adhesion, so that the etching solution may easily penetrate between the rolled copper foil and the photoresist, and it may be difficult to form a predetermined wiring. Even if the predetermined wiring can be formed, the concave portion on the surface of the rolled copper foil may be erroneously recognized as a disconnection or the like in the wiring inspection by image processing, and the yield may be reduced.

  As a method for suppressing the unevenness of the surface of the rolled copper foil by this soft etching, for example, Patent Document 1 proposes a method of forming a copper plating layer having a thickness for performing soft etching on the rolled copper foil. Yes. For example, Patent Document 2 proposes a method of forming a layer having a random crystal orientation or an amorphous layer on the surface of a rolled copper foil. Further, for example, Patent Document 3 proposes a method of suppressing etching non-uniformity by aligning the crystal orientation on the surface of the rolled copper foil.

JP 2009-188369 A JP 2009-231309 A Japanese Patent No. 4662834

  However, in patent document 1 and patent document 2, since a copper plating layer and an amorphous layer are newly formed with respect to the surface of a rolled copper foil, a manufacturing process will increase and manufacturing cost will increase. Patent Document 3 proposes to align the crystal orientation of the surface of the rolled copper foil, but it is difficult to make the crystal structure of the surface of the rolled copper foil produced by rolling close to a single crystal. It is. That is, in Patent Documents 1 to 3, it is difficult to fundamentally solve dishdown.

  This invention is made | formed in view of such a problem, The objective is to provide the rolled copper foil in which the formation of the recessed part of a surface is suppressed in the case of an etching.

According to a first aspect of the invention,
A rolled copper foil having a main surface composed of a plurality of crystal planes to be used through a recrystallization step, wherein the temperature is raised to 200 ° C. so that all particles of the rolled copper foil are recrystallized. after recrystallization heating 30 minutes Te, when obtained from EBSP (Electron Backscatter Diffraction Pattern) method to said main surface, in the main surface (200) plane area ratio of the _{R (200),} wherein _{R ( 200)} is less than 20%, and a rolled copper foil in which the maximum dimension of the plurality of crystal faces constituting the main surface is 100 μm or less is provided.

According to a second aspect of the invention,
A rolled copper foil having a main surface composed of a plurality of crystal planes to be used through a recrystallization step, obtained from an EBSP (Electron Backscatter Diffraction Pattern) method for the main surface, When the area ratio of the (220) plane is R ₍₂₂₀₎ and the area ratio of the (200) plane to the main surface is R ₍₂₀₀₎ , the R ₍₂₂₀₎ is 20% or more and 50% or less. A rolled copper foil that satisfies the formula R ₍₂₂₀₎ / R ₍₂₀₀₎ ≧ 10 is provided.

According to a third aspect of the invention,
After the recrystallization step of heating to 200 ° C. and heating for 30 minutes so that all particles of the rolled copper foil are recrystallized, the R ₍₂₀₀₎ is less than 20% and constitutes the main surface. A rolled copper foil of a second aspect is provided in which the maximum dimension of the plurality of crystal planes is 100 μm or less.

According to a fourth aspect of the invention,
There is provided a rolled copper foil according to any one of the first to third aspects, which is for a flexible printed wiring board and has a thickness of 7 μm or more and 50 μm or less.

According to a fifth aspect of the present invention,
There is provided the rolled copper foil according to any one of the first to fourth aspects, wherein the tensile strength after the recrystallization step of heating to 200 ° C. and heating for 30 minutes is 180 N / mm ² or more.

  According to the present invention, a rolled copper foil is obtained in which formation of concave portions on the surface is suppressed during etching.

It is a figure for demonstrating the correlation with the area ratio of a (200) plane, and the largest dimension of a crystal plane. It is a flowchart which shows the manufacturing process of the rolled copper foil which concerns on this embodiment.

  As described above, since the etching rate varies depending on the crystal orientation of the crystal plane formed on the surface of the rolled copper foil, a recess is formed on the surface of the rolled copper foil. In this regard, the present inventor has intensively studied the relationship between crystal orientation and etching rate. As a result, the (200) plane of the plurality of crystal planes has a slower etching rate than the other crystal planes, and the crystal grains adjacent to the crystal grains having the (200) plane may be relatively concave. I understood. Moreover, it has been found that when a large crystal plane is included on the surface of the rolled copper foil, recesses are easily formed. Therefore, the present inventor has further studied by paying attention to the area ratio of the (200) plane on the surface of the recrystallized rolled copper foil and the size of the crystal plane. And it discovered that dishdown in rolled copper foil can be suppressed by making the area ratio of a (200) plane and the magnitude | size of a crystal plane into a predetermined range. Further, in the rolled copper foil before recrystallization, when the recrystallization is performed by setting the area ratio of the (220) plane that changes to the (200) plane during recrystallization and the (200) plane to a predetermined range, respectively. It was found that a rolled copper foil that hardly causes dishdown can be obtained. The present invention has been made based on the above findings.

[First embodiment of the present invention]
Below, the rolled copper foil which concerns on the 1st Embodiment of this invention is demonstrated. First, the structure of the rolled copper foil which concerns on this embodiment is demonstrated.

(Outline of rolled copper foil)
The rolled copper foil which concerns on this embodiment is a plate-shaped copper foil provided with the rolling surface as a main surface, for example. As shown in the manufacturing method described later, this rolled copper foil is subjected to a hot rolling process on the ingot of the raw material, and after the cold rolling process and the annealing process are repeated, the final cold rolling process is performed. It is a rolled copper foil having a predetermined thickness.

  The copper material that is a raw material of the rolled copper foil is not particularly limited, and pure copper such as oxygen-free copper (OFC) or tough pitch copper can be used. As the copper material, in addition to pure copper such as tough pitch copper, it is also possible to use an alloy obtained by adding a small amount of elements such as Sn, Ag, Zr, Fe, Co, and Ni to pure copper.

  The rolled copper foil of the present embodiment is subjected to a final cold rolling process so as to have a predetermined final processing degree, and the thickness is 7 μm or more and 50 μm or less. This rolled copper foil is used, for example, for wiring materials such as FPC that require flexibility. The rolled copper foil exhibits excellent bending characteristics and bending characteristics due to recrystallization of the crystal structure in the heating step.

Finishing degree of bending property of the rolled copper foil, an important factor for expressing the bending characteristics, the final cold thickness of rolled copper foil after rolling and T _A, the final cold rolling step prior to the processing target the thickness of the object (sheet of copper) in case of the T _B, is determined by the following equation (1).
Final processing degree (%) = [(T _B −T _A ) / T _B ] × 100 (1)
When using rolled copper foil for FPC, it is preferable that the final degree of processing is 80% or more and less than 99%. If it is less than 80%, since the amount of strain applied to the rolled copper foil is small, it is difficult to recrystallize the copper foil in the FPC manufacturing process. On the other hand, if it is 99% or more, recrystallization occurs due to the processing heat during the cold rolling process, and the strain in the rolled copper foil is released. Therefore, it is difficult to apply a predetermined amount of strain to the rolled copper foil. Become.

(Rolled structure of rolled copper foil)
A predetermined crystal structure is formed on the rolled copper foil, and the crystal structure is composed of a plurality of crystal grains. The rolled copper foil after the final cold rolling process is produced by being pulled by a predetermined rolling tension and rolled by a predetermined rolling load, so that the crystal grains are elongated and deformed in the rolling direction. . Due to the deformation of the crystal grains, the crystal structure of the rolled copper foil after the final cold rolling process is a fibrous rolled structure.

  The crystal grains constituting the rolled structure are oriented in a predetermined crystal orientation. Crystal grains oriented in a predetermined crystal orientation appear as predetermined crystal planes on the main surface (rolled surface) of the rolled copper foil. Since the rolled structure is composed of a plurality of crystal grains, a plurality of crystal planes appear on the rolled surface of the rolled copper foil, and each crystal plane has a different crystal orientation. That is, the rolled surface of the rolled copper foil is composed of a plurality of crystal planes having different crystal orientations.

Examples of the plurality of crystal planes include (200) plane, (220) plane, (111) plane, (113) plane, and (123) plane. Each of these crystal planes appears at a predetermined ratio (area ratio) on the main surface of the rolled copper foil, and each of the (200) plane and (220) plane has a predetermined area ratio. Here, the area ratio indicates a ratio of a specific crystal plane appearing on the main surface, and indicates a ratio of the area of the specific crystal plane on the main surface. The area ratio of the specific crystal plane is obtained by the following formula (2).

The crystal grains oriented in the (200) plane are crystal grains having a normal vector whose angle formed by the normal vector of the rolled surface and the normal vector of the (200) plane is within 15 degrees. Among the plurality of crystal planes, the (200) plane has a low etching rate and causes non-uniform etching of the main surface. The crystal orientation of the crystal grains oriented in the (200) plane does not change by recrystallization.
The crystal grains oriented in the (220) plane are crystal grains having a normal vector whose angle formed by the normal vector of the rolled surface and the normal vector of the (220) plane is within 15 degrees. Crystal grains oriented in the (220) plane tend to become crystal grains oriented in the (200) plane by recrystallization. The crystal grains whose orientation changes to the (200) plane by recrystallization are easily recrystallized from the crystal grains oriented to the (200) plane to easily form coarse crystal grains.

(Recrystallized structure of rolled copper foil)
The rolled structure of the rolled copper foil after the final cold rolling step is heated to release the strain caused by rolling, and the crystal grains are recrystallized to form a recrystallized structure. In the recrystallized structure of the rolled copper foil, crystal grains grow by recrystallization, and larger crystal grains are formed as compared with the rolled structure. Further, during recrystallization, the crystal orientation of the crystal grains changes, and the crystal plane appearing on the main surface of the rolled copper foil also changes. As the crystal face changes, the area ratio of the crystal face on the main surface also changes. Specifically, among the plurality of crystal planes, the (220) plane changes to the (200) plane by recrystallization. Further, the (200) plane does not change the crystal orientation due to recrystallization and remains after heating. For this reason, in the recrystallized structure, the area ratio of the (220) plane decreases as compared with the rolled structure, while the area ratio of the (200) plane increases.
In this way, the rolled structure of the rolled copper foil is recrystallized by heating, and the crystal orientation of the crystal grains changes and the crystal grains grow to a large size, thereby changing to a recrystallized structure. Due to this change in crystal structure, the rolled copper foil exhibits bending characteristics and bending characteristics.

(Configuration of rolled copper foil)
The rolled copper foil of the present embodiment has a configuration in which the recrystallized structure that is recrystallized by heating is suppressed from generating dishdown, and the (200) plane area ratio and crystal that are the cause of dishdown The size of the surface is in a predetermined range.
That is, the rolled copper foil of the present embodiment is a rolled copper foil having a main surface composed of a plurality of crystal planes to be used through a recrystallization step, and all the particles of the rolled copper foil are regenerated. After the recrystallization step of heating to 200 ° C. and heating for 30 minutes so as to crystallize, the area ratio of the (200) plane on the main surface obtained from the EBSP (Electron Backscatter Diffraction Pattern) method for the main surface is R _{(200 )} And R ₍₂₀₀₎ is less than 20%, and the maximum dimension of a plurality of crystal faces constituting the main surface is 100 μm or less.

  The area ratio is calculated by the above formula (2). The area of a specific crystal plane such as the (200) plane or (220) plane is determined by the EBSP (Electron Backscatter Diffraction Pattern) method (high resolution crystal orientation analysis method) using an FE-SEM (Field Emission Scanning Electron Microscope). Measured.

  In the EBSP method, an electron beam is incident on the sample surface (rolled surface of the rolled copper foil), and the crystal orientation at the electron beam incident position is determined by analyzing the Kikuchi pattern obtained from the reflected electrons generated at this time. Is. By scanning an electron beam on the sample surface in two dimensions and measuring the crystal orientation at every predetermined pitch, the distribution of crystal orientation on the sample surface can be measured, and the measurement result can be obtained as a crystal orientation map. According to the EBSP method, the measurement region is wider than that of the X-ray diffraction method and the like, and the crystal orientation of a plurality of crystal grains (crystal planes) can be measured.

From the crystal orientation map obtained by the EBSP method, the total area of specific crystal planes can be calculated, and the area ratio of specific crystal planes can be calculated by the above equation (2).
Moreover, the dimension of a crystal plane can be measured from the obtained crystal orientation map. The size of the crystal plane indicates the size of the crystal plane where the crystal grains appear on the main surface of the rolled copper foil, and is an index of the size of the crystal grains. Specifically, based on the crystal orientation map, the dimensions in the rolling direction and the width direction of one crystal face are measured, and the average value is taken as the dimension of the crystal face. Then, the respective dimensions of the plurality of crystal planes constituting the main surface are measured, and the maximum dimension of the crystal plane is calculated.

  In the rolled copper foil of this embodiment, the area ratio of the (200) plane obtained by the EBSP method is less than 20% in the recrystallized structure after the recrystallization process by heating. According to this configuration, the etching rate is slow, the area ratio of the (200) plane that causes dishdown is small, and uniform irregularities are formed by crystals other than the (200) plane. When the area ratio of the (200) plane is 20% or more, the area of the (200) plane occupying the main surface is large, and it becomes difficult to suppress local recesses generated on the surface of the rolled copper foil by etching.

  Further, the maximum dimension of the plurality of crystal planes constituting the main surface is 100 μm or less. That is, the dimension of the largest crystal plane among the plurality of crystal planes is 100 μm or less. In the recrystallized structure, when the maximum size of the crystal plane exceeds 100 μm, the crystal grains are coarse, and thus local unevenness may occur during etching, although not as much as the recess in the (200) plane. This unevenness reduces the adhesion to the photoresist as well as the recess on the (200) plane.

  Here, the correlation between the area ratio of the (200) plane and the maximum dimension of the crystal plane will be described. In the recrystallized structure, an increase in the area ratio of the (200) plane indicates that the (220) plane or the like changes to the (200) plane and recrystallization is promoted. The crystal grains grow by recrystallization and become large crystal grains. That is, as the area ratio of the (200) plane increases, the size of the crystal grains tends to increase. This correlation is shown in FIG. FIG. 1 is a diagram for explaining the correlation between the area ratio of the (200) plane and the maximum dimension of the crystal plane. In FIG. 1, the horizontal axis indicates the area ratio of the (200) plane, and the vertical axis indicates the maximum dimension of the crystal plane. FIG. 1 shows that the maximum dimension of the crystal plane increases as the area ratio of the (200) plane in the recrystallized structure of the rolled copper foil increases. And when the area ratio of the (200) plane is 20% or more, it is shown that the maximum dimension of the crystal plane tends to exceed 100 μm.

  Thus, in the recrystallized structure after the recrystallization process of the rolled copper foil, the area ratio of the (200) plane can be suppressed to a predetermined value or less, and the size of the crystal plane can be suppressed to a predetermined value or less. It is possible to obtain a rolled copper foil in which the formation of concave portions on the surface due to the above is suppressed.

Moreover, in the recrystallized structure after the recrystallization process of the rolled copper foil, since the area ratio of the (200) plane can be suppressed to a predetermined numerical value or less, a tensile strength of 180 N / mm ² or more can be obtained.

[Second Embodiment of the Present Invention]
In the first embodiment described above, the rolled copper foil in which the recrystallized structure that has been heated and recrystallized has a predetermined configuration has been described. However, in the second embodiment, the rolled structure before recrystallization has a predetermined structure. The rolled copper foil which becomes a structure is demonstrated. Hereinafter, differences from the first embodiment will be described.

  As described above, the (220) plane existing in the rolled copper foil before recrystallization is oriented to the (200) plane by recrystallization. Further, the (200) plane existing in the rolled copper foil before recrystallization remains as the (200) plane after recrystallization. That is, in the rolled copper foil, the (220) plane is oriented to the (200) plane by the recrystallization step, and the area ratio of the (200) plane increases. As the area ratio of the (200) plane increases, it becomes difficult to suppress dishdown.

In this respect, in the rolled copper foil of this embodiment, the rolled structure before being heated and recrystallized increases the area ratio of the (200) plane by recrystallization, and the area ratio of the (200) plane. Is a predetermined range.
That is, the rolled copper foil of the present embodiment is a rolled copper foil having a main surface composed of a plurality of crystal planes to be used through a recrystallization process, and is an EBSP (Electron Backscatter Diffraction Pattern) for the main surface. ) When the area ratio of the (220) plane to the main surface obtained from the method is R ₍₂₂₀₎ and the area ratio of the (200) plane to the main surface is R ₍₂₀₀₎ , R ₍₂₂₀₎ is 20% or more. It is 50% or less, and satisfies the relational expression R ₍₂₂₀₎ / R ₍₂₀₀₎ ≧ 10.

  In the present embodiment, the area ratio of the (220) plane oriented to the (200) plane by recrystallization accompanying heating is set to 20% or more and 50% or less. According to this configuration, it is possible to suppress an increase in the area ratio of the (200) plane that occurs when the rolled copper foil is recrystallized, and to suppress the occurrence of dishdown when the rolled copper foil is etched. When the area ratio of the (220) plane is less than 20%, the recrystallization itself hardly progresses when heated, so that the crystal structure of the rolled copper foil is a mixed grain of the rolled structure and the recrystallized structure. Since the etching rate is different between the rolled structure and the recrystallized structure, dishdown tends to occur as a result. Further, if the rolled structure remains, it becomes difficult to obtain sufficient bending characteristics of the rolled copper foil. On the other hand, when it exceeds 50%, grain growth is promoted by recrystallization, so that coarse crystal grains of 100 μm or more are generated, and when etched, irregularities are generated on the surface of the rolled copper foil.

In the present embodiment, it satisfies the (220) plane of the area ratio _{R (220)} and (200) plane of the area ratio _{R (200)} is a relational expression _{R (220) / R (200} ) ≧ 10. That is, the area ratio of the (200) plane formed by the rolling process and included in the rolled copper foil before recrystallization is 1/10 or less of the area ratio of the (220) plane. According to this configuration, it is possible to suppress the crystal growth of crystal grains oriented in the (200) plane and to suppress the formation of coarse crystal grains.

  In this way, in the rolled structure of the rolled copper foil before recrystallization, by setting the area ratio of the (220) plane and the (200) plane within a predetermined numerical range, the (200) plane in the recrystallized structure after recrystallization. An increase in the area ratio can be suppressed. That is, it is possible to obtain a rolled copper foil in which the formation of surface irregularities by etching is suppressed.

  Moreover, when the rolled copper foil of this embodiment is heated and recrystallized, it is preferable that the (200) plane area ratio is less than 20%, and the maximum dimension of the plurality of crystal planes is 100 μm or less. According to this configuration, in the recrystallized structure after recrystallization, it is possible to further suppress the area ratio of the (200) plane that becomes a recess by etching and further suppress the formation of coarse crystal grains due to recrystallization.

[Method for producing rolled copper foil]
Next, the manufacturing method of the rolled copper foil of the 1st, 2nd embodiment mentioned above is demonstrated using FIG. FIG. 2 is a flowchart showing a process for producing a rolled copper foil according to an embodiment of the present invention.

(Ingot preparation step S10)
As shown in FIG. 2, first, casting is performed using pure copper such as oxygen-free copper (OFC) or tough pitch copper as a raw material to prepare an ingot. The ingot is formed in a plate shape having a predetermined thickness and a predetermined width, for example. Pure copper such as oxygen-free copper or tough pitch copper as a raw material may be a dilute copper alloy to which a predetermined additive is added in order to adjust various properties of the rolled copper foil. As the additive, for example, elements such as Sn, Ag, Zr, Fe, Co, and Ni can be used.

  Note that the composition of the ingot is maintained substantially as it is in the rolled copper foil after the final cold rolling step S40 described later, and when an additive is added to the ingot, the ingot and the rolled copper foil Have substantially the same additive concentration.

(Hot rolling process S20)
Next, hot rolling is performed on the prepared ingot to produce a cake (plate material) having a thickness smaller than a predetermined thickness after casting.

(Repetition step S30)
Subsequently, a repetitive step S30 in which the cold rolling step S31 and the annealing step S32 are repeatedly performed a predetermined number of times on the plate material having a predetermined thickness is performed. Specifically, work hardening is eased by subjecting a plate material that has been cold-rolled and work hardened to an annealing treatment to anneal the plate material. By repeating this a predetermined number of times, a copper strip (hereinafter also referred to as a dough) having a predetermined thickness is manufactured. When adding the additive etc. which adjust heat resistance to a copper material, the temperature conditions of an annealing process are changed suitably according to the heat resistance of a copper material.

  In addition, in the repetition process S30, the annealing process S32 in the middle of the repetition is referred to as an “intermediate annealing process”. Further, the annealing step S32 performed at the end of the repetition, that is, immediately before the final cold rolling step S40 described later is referred to as a “final annealing step” or a “dough annealing step”.

  In the dough annealing step performed at the end of the repeating step S30, the dough annealing process is performed on the dough described above to obtain an annealed dough. Also in the dough annealing step, the temperature condition is appropriately changed according to the heat resistance of the copper material. At this time, it is preferable that the dough annealing process is performed under a temperature condition that can sufficiently relieve the processing distortion caused by each process described above, for example, a temperature condition substantially equivalent to a complete annealing treatment.

(Final cold rolling process S40)
Next, the final cold rolling step S40 is performed. In the final cold rolling step S40, cold rolling is performed a plurality of times on the annealed dough obtained in the repeating step S30. At this time, cold rolling is performed at a final degree of processing of 80% or more and less than 99% so that a rolled copper foil that exhibits high bending characteristics when heated is obtained. That is, the degree of work per one time (one pass) is adjusted so that the final degree of work falls within the above numerical range, and cold rolling is performed a plurality of times. The degree of processing per pass is defined according to the final degree of processing. The thickness of the workpiece before the n-th cold rolling is T _Bn, and the thickness of the workpiece after rolling is T _An . Then, the degree of processing per pass (%) = [(T _Bn −T _An ) / T _Bn ] × 100.

  In a rolling process such as a final cold rolling process, a copper material such as an annealed dough is drawn into a gap between a pair of rolls facing each other and is drawn out to the opposite side to reduce the thickness. Since the copper material is unwound at a predetermined speed on the entrance side before being drawn into the roll, a predetermined tension (unwinding side tension) is applied to the copper material, and the tension in the direction opposite to the direction in which the material is rolled. Tension is applied. On the other hand, on the exit side after being pulled out from the roll, the copper material is wound up at a predetermined speed. Therefore, a predetermined tension (winding side tension) is applied to the copper material, and the tensile tension in the direction in which the material is rolled. It takes. In the rolling process, the unwinding side tension and the winding side tension are appropriately adjusted to adjust the rolling tension applied to the copper material. In addition, the rolling load of the roll into which the copper material is drawn is adjusted as appropriate.

  In the final cold rolling process, the distortion of the crystal structure of the produced rolled copper foil is adjusted by appropriately adjusting the rolling tension and rolling load as rolling conditions. By adjusting the strain, the crystal plane formed on the rolled surface is changed, and the area ratio is appropriately changed.

  Here, the difference of the rolling structure | tissue by rolling conditions is demonstrated.

  As the rolling conditions, for example, when adjusting the rolling tension by increasing the unwinding side tension and the winding side tension of the copper material or increasing the rolling load, the rolled microstructure of the rolled copper foil is α-fiber. There is a tendency to become a crystal structure called. α-fiber is a rolled structure that appears well when pure copper is rolled, and {112} <111> mainly appears on the rolled surface. Although α-fiber is recrystallized by a heating process, the recrystallized structure of α-fiber is relatively strongly affected by the crystal orientation of the rolled structure. For this reason, the recrystallized structure of α-fiber becomes a crystal structure in which the crystal grains are fine and do not include coarse crystal grains when crystal grains having a relatively random crystal orientation grow.

  On the other hand, as the rolling conditions, for example, when the winding side tension is increased with respect to the unwinding side tension of the copper material or when the rolling load is reduced, the crystal structure of the rolled copper foil is a rolling structure called β-fiber. Tend to be. β-fiber is a rolled structure in which each of the Cu orientation {112} <111> and the S orientation {123} <634> changes continuously in addition to the Brass orientation {110} <112>. Compared with the above-mentioned α-fiber, β-fiber tends to form coarse crystal grains oriented in the (200) plane with the crystal grains oriented in the (200) plane as nuclei.

Therefore, in the present embodiment, in the final cold rolling step, the rolling condition is appropriately adjusted to form a rolled structure in which a large amount of α-fiber is present. That is, the area ratio of the (220) plane is 20% or more and 50% or less, and the area ratio R _{(220) of the (220} ) plane and the area ratio R _{(200) of the} (200) plane are related to the relational expression R _{(220 )} / R ₍₂₀₀₎ A rolled copper foil that satisfies ≧ 10 is manufactured.

(Surface treatment step S50)
Finally, a predetermined surface treatment is performed on the obtained rolled copper foil. In the rolled copper foil used for FCP, one surface serves as an adhesive surface with the base material, and the other surface serves as a surface to which a photoresist is applied. The surface to be bonded to the base material is subjected to a roughening process to secure an adhesive force to the base material, thereby forming a roughened surface. The roughened surface is further subjected to various surface treatments in order to stabilize the adhesive properties such as heat resistance and chemical resistance and the etching properties in terms of adhesion to the substrate. The surface to which the photoresist is applied is a glossy surface. Since the glossy surface is required to have heat discoloration resistance, solder wettability, resist adhesion, solubility during soft etching, surface uniformity, etc., a predetermined treatment is performed. The rolled copper foil which concerns on this embodiment is manufactured by the above.

[Method for manufacturing flexible printed circuit board]
Next, the manufacturing method of the flexible printed wiring board (FPC) using the rolled copper foil which concerns on one Embodiment of this invention is demonstrated.

  In the rolled copper foil to be used, the area ratio of the (220) plane is 20% to 50%, and the area ratio of the (220) plane and the (200) plane satisfies the above relational expression.

(Lamination process)
First, the rolled copper foil according to the present embodiment is cut into a predetermined size and bonded to an FPC base material made of a resin such as polyimide to form a copper-clad laminate. When bonding the copper foil, the copper foil may be bonded via an adhesive, or may be directly bonded without using an adhesive. When an adhesive is used, the adhesive is cured by heat treatment, and the rolled copper foil and the base material are brought into close contact with each other to be integrated. When an adhesive is not used, the rolled copper foil and the substrate are brought into direct contact with each other by heating / pressurizing treatment. The heating conditions in the heat treatment can be appropriately selected according to the curing temperature of the adhesive or the base material, and for example, the temperature is raised to 200 ° C. and held for 30 minutes.

  By the heat treatment in the bonding process, the rolled structure of the rolled copper foil is recrystallized to become a recrystallized structure. That is, the bonding process of the rolled copper foil also serves as the recrystallization process of the rolled copper foil. A rolled copper foil having a recrystallized structure becomes a rolled copper foil having excellent bending characteristics and bending characteristics.

  In the recrystallization step, heating is performed so that all particles of the rolled copper foil are recrystallized. The rolled copper foil has a (200) plane area ratio of less than 20% and a maximum dimension of a plurality of crystal planes of 100 μm or less by the recrystallization process.

  It should be noted that, since the bonding process also serves as a recrystallization process, the rolled copper foil can be handled in the work-hardened state after the cold rolling process until the rolled copper foil is bonded to the FPC substrate. It is possible to prevent deformation such as elongation, wrinkling, and folding when the foil is bonded to the base material.

(Soft etching process)
Next, soft etching is performed on the surface of the recrystallized rolled copper foil, and the oxide film formed on the surface of the rolled copper foil is removed. At the time of soft etching, the recrystallized structure of the rolled copper foil has an area ratio of (200) plane of less than 20% and a maximum dimension of a plurality of crystal planes of 100 μm or less. That is, in the recrystallized structure of the rolled copper foil, the area ratio of the (200) plane having a high etching rate is low, and fine crystal grains are formed. For this reason, in the rolled copper foil, surface unevenness due to the difference in etching rate is difficult to be formed.

(Surface machining process)
Next, surface processing is performed on the rolled copper foil of the copper-clad laminate. In the surface processing, a wiring forming process for forming copper wiring or the like on the rolled copper foil by using a technique such as etching, and surface treatment such as plating to improve the connection reliability between the copper wiring and other electronic members. A surface treatment process to be performed and a protective film forming process for forming a protective film such as a solder resist so as to cover a part of the copper wiring to protect the copper wiring and the like are performed.

  In the wiring formation step, for example, a photoresist is formed on the rolled copper foil. However, since the surface of the rolled copper foil has few concave portions due to soft etching, the adhesion between the rolled copper foil and the photoresist is high. As a result, when the wiring is formed by etching, the penetration of the etching solution can be suppressed and the wiring can be formed with high accuracy.

  By the above, FPC using the rolled copper foil which concerns on this embodiment is manufactured.

[Other Embodiments of the Present Invention]
As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, It can change variously in the range which does not deviate from the summary.

  For example, in the above-described embodiment, the case where pure copper is used as the copper material of the rolled copper foil has been described. However, an additive may be appropriately contained according to adjustment of various characteristics such as heat resistance.

  In the above-described embodiment, the process of laminating the copper foil also serves as the heating process (recrystallization process) of the rolled copper foil in manufacturing the FPC, but the recrystallization process is separate from the laminating process. It may be performed as a process.

  Moreover, in embodiment mentioned above, although rolled copper foil was used for FPC use, the use of rolled copper foil is not limited to this, It uses for the use which requires the outstanding bending characteristic and bending characteristic. Can do. The rolled copper foil can be used, for example, as a negative electrode material for a lithium ion secondary battery.

  Moreover, although the case where the soft etching process was provided was demonstrated in embodiment mentioned above, before forming a rolled copper foil in wiring, you may provide the half etching process which makes thickness of a rolled copper foil thin.

  Next, examples of the rolled copper foil according to the present invention will be described.

(Examples 1 and 2, Comparative Examples 1 to 4)
In this example, rolled copper foil was produced by appropriately changing rolling conditions, and the rolled copper foil was heated and recrystallized, and then the presence or absence of dishdown was confirmed. And generation | occurrence | production of dishdown by the characteristic of the rolled copper foil before recrystallization or the characteristic of the rolled copper foil after recrystallization was evaluated. Specifically, it was performed as shown below.

<Manufacture of rolled copper foil>
First, after hot rolling was performed on the ingot, cold rolling and annealing were repeated to prepare a copper material (annealed fabric) made of tough pitch copper having a thickness of 50 μm. Thereafter, the annealed dough was subjected to a final cold rolling process, and the rolled oil was removed to produce the rolled copper foils (thickness 10 μm) of Examples 1 and 2 and Comparative Examples 1 to 4. As rolling conditions in the final cold rolling process, as shown in Table 1 below, the unwinding tension and the winding tension were 100 N / mm ² and the rolling load was 50 t, respectively. Further, the degree of processing of each pass was set to 40% to 10%, and the number of passes was appropriately changed to 0, 5 to 7. In Comparative Example 4, the number of passes was set to 0, which indicates that the final cold rolling process was not performed and the annealed dough was left as it was. In addition, as a roll (work roll) used for rolling, a roll having a diameter of 120 mm was used.

<Evaluation of properties before recrystallization>
Next, the characteristics before recrystallization were evaluated about the rolled copper foil manufactured above. As characteristic before recrystallization rolled copper foil, the area ratio of (220) plane in the main surface of the rolled copper foil _{R (220)} and (200) plane of the area ratio _{R (200)} is measured, the ratio _{R (220 )} / R ₍₂₀₀₎ was calculated. In measurement, the oxide film formed on the surface (rolled surface) of the rolled copper foil was removed by a flat milling apparatus, and the surface was analyzed by SEM-EBSP (Scanning Electoron Microscope-Electron BackScattering Pattern). For analysis by EBSP, a scanning electron microscope SU-70 (manufactured by Hitachi High-Technologies) and OIM (manufactured by TSL) were used. As analysis conditions, a magnification of 200 times, an inclination of 70 degrees, an analysis region of 100 μm × 100 μm, and a measurement pitch of 0.3 μm, crystal orientation maps on the main surface of each rolled copper foil were obtained. Based on the obtained crystal orientation map, the crystal orientation of each crystal face was calculated, R ₍₂₂₀₎ and R ₍₂₀₀₎ were measured, and the ratio R ₍₂₂₀₎ / R ₍₂₀₀₎ was calculated. The results are shown in Table 2 below.

As shown in Table 2, in the rolled copper foils of Examples 1 and 2, the area ratio R ₍₂₂₀₎ of the (220) plane is in the range of 20% to 50% before recrystallization, and R ₍₂₂₀₎ / R ₍₂₀₀₎ was confirmed to be 10 or more.
On the other hand, in the rolled copper foils of Comparative Examples 1 to 4, the area ratio R ₍₂₂₀₎ of the (220) plane is outside the range of 20% to 50% before recrystallization, or R ₍₂₂₀₎ / R _(200). Was confirmed to be less than 10.

<Evaluation of properties after recrystallization>
Next, after heating up the rolled copper foil manufactured above to 200 degreeC in air | atmosphere, it hold | maintained for 30 minutes and recrystallized. This simulates the thermal load of the recrystallization process (heat treatment process) performed in the bonding process described above. About the recrystallized rolled copper foil, the characteristic after recrystallization was evaluated. As characteristics after recrystallization of the rolled copper foil, the area ratio R _{(200) of} the ₍₂₀₀₎ plane, the maximum dimension of the crystal plane, the occurrence of dishdown, and the presence or absence of non-recrystallized particles were evaluated. Each evaluation method will be described below.

(1) Area ratio R of ₍₂₀₀₎ plane ₍₂₀₀₎
Similarly to the evaluation of the properties before recrystallization, the area ratio R ₍₂₀₀₎ of the (200) plane of the recrystallized rolled copper foil was measured by the EBSP method. As analysis conditions, the magnification was 200 times, the inclination was 70 degrees, the analysis area was 400 μm × 400 μm, and the measurement pitch was 3 μm.

(2) Maximum dimension of crystal plane The maximum dimension of a crystal plane is based on the crystal orientation map obtained by the EBSP method, and the dimensions of the crystal plane in the rolling direction and the width direction are measured. The surface dimensions were taken. Then, the dimensions of the plurality of crystal planes were respectively measured, and the maximum crystal plane dimension among the plurality of crystal planes was obtained as the maximum dimension of the crystal plane.

(3) Dishdown
The presence or absence of dishdown was confirmed by soft-etching the surface of the rolled copper foil after recrystallization to confirm the occurrence of dishdown. Specifically, the surface of the recrystallized rolled copper foil was etched by 1 μm using a perhydrosulfuric acid-based etching solution, and the surface of the rolled copper foil after being washed with water and dried was observed with a metal microscope.

(4) Presence / absence of non-recrystallized particles The presence / absence of non-recrystallized particles is measured based on the crystal orientation map information obtained by the EBSP method, that is, a region where the crystal grain size is 3 μm or less. A region that could not be analyzed with high reliability at a pitch of 3 μm was selected, and this region was confirmed by performing EBSP analysis at a measurement pitch of 0.3 μm again. The determination criteria were that the crystal grains at this time extend in the rolling direction and that the crystal orientation consists of the rolling texture described above.

These evaluation results are shown in Table 2. According to Table 2, rolling characteristics of Examples 1 and 2 in which the area ratio of the (200) plane was 20% to 50% and R ₍₂₂₀₎ / R ₍₂₀₀₎ was 10 or more as the characteristics before recrystallization. The copper foil had a small (200) plane area ratio after recrystallization, and it was confirmed that coarse crystal grains (crystal grains having a maximum dimension of 100 μm or more) were not formed. Moreover, the occurrence of dishdown was not confirmed. Moreover, the particle | grains which were not recrystallized were not confirmed, but it was confirmed that all the particles are the recrystallized state.

In contrast, in Comparative Example 1 and Comparative Example 2 in which the area ratio of the (220) plane exceeded 50% as a characteristic before recrystallization, grain growth after recrystallization was remarkable, resulting in an area of (200) plane. The ratio was high and formation of coarse crystal grains was confirmed. In Comparative Examples 1 and 2, the occurrence of dishdown was confirmed. In Comparative Examples 1 and 2, particles that were not recrystallized were not confirmed, and it was confirmed that all particles were recrystallized.
In Comparative Example 3, since recrystallization occurred due to processing heat during rolling, R ₍₂₂₀₎ / R ₍₂₀₀₎ was less than 10 as the characteristics before recrystallization. As a result, after the recrystallization, the area ratio of the (200) plane was high and coarse crystal grains were formed, so that the occurrence of dishdown was confirmed. In Comparative Example 3, it was confirmed that all particles were recrystallized.
In Comparative Example 4, there was no problem with the area ratio of the (200) plane after recrystallization and R ₍₂₂₀₎ / R ₍₂₀₀₎ , but the occurrence of dishdown was confirmed. Moreover, the particle | grains which were not recrystallized were confirmed and it confirmed that recrystallization was not fully accelerated | stimulated. As can be seen from the confirmed non-recrystallized particles, the area ratio of the (220) plane is low as the characteristics before recrystallization, and recrystallization is not promoted. It is thought that it became. As a result, it is considered that dishdown occurred due to the difference in etching rate between the rolled structure and the recrystallized structure.

(Examples 3-6, Comparative Examples 5-7)
In Examples 3 to 6 and Comparative Examples 5 to 7, Example 1 except that the rolling speed was 400 m / min, the unwinding tension and the winding tension were appropriately changed and the cold rolling was fixed to 7 passes. A rolled copper foil was produced in the same manner as described above. Each rolling condition is shown in Table 3 below.

  About the manufactured rolled copper foil, the characteristic before recrystallization was evaluated similarly to Example 1. FIG. Moreover, the manufactured rolled copper foil was recrystallized similarly to Example 1, and the characteristic after the recrystallization was evaluated. The evaluation results are shown in Table 4 below.

According to Table 4, since the rolled copper foils of Examples 3 to 6 had good characteristics before recrystallization and good characteristics after recrystallization, the occurrence of dishdown was not confirmed.
In Comparative Examples 5 and 6, the occurrence of dishdown was confirmed even though the properties of the rolled copper foil before recrystallization were good. This is because the rolling structure in the rolled copper foil has changed due to the influence of the winding tension, and the grain growth has increased during the recrystallization, and as a result, the characteristics after recrystallization of the rolled copper foil have deteriorated. It is done.
In Comparative Example 7, although the area ratio R ₍₂₀₀₎ of the (200) plane was 50% or less as a characteristic before recrystallization, recrystallization occurred during rolling and R ₍₂₂₀₎ / R _{( 200)} was less than 10. As a result, the characteristics after recrystallization deteriorated and the occurrence of dishdown was confirmed.

(Examples 7 and 8, Comparative Examples 8 to 11, Reference Examples 1 and 2)
In Examples 7 and 8, Comparative Examples 8 to 11 and Reference Examples 1 and 2, the rolling conditions were 400 m / min, the rolling load was changed as appropriate, and cold rolling was fixed to 7 passes. A rolled copper foil was produced in the same manner as in Example 1. Each rolling condition is shown in Table 5 below.

  About the manufactured rolled copper foil, the characteristic before recrystallization was evaluated similarly to Example 1. FIG. Moreover, the manufactured rolled copper foil was recrystallized similarly to Example 1, and the characteristic after the recrystallization was evaluated. The evaluation results are shown in Table 6 below.

According to Table 6, since the rolled copper foils of Examples 7 and 8 had good characteristics before recrystallization and good characteristics after recrystallization, the occurrence of dishdown was not confirmed.
In Comparative Examples 8 to 10, the occurrence of dishdown was confirmed although the properties before recrystallization of the rolled copper foil were good. This is because the rolling structure in the rolled copper foil is changed by the rolling load, and the grain growth becomes severe during recrystallization, and as a result, the characteristics after recrystallization of the rolled copper foil are considered to be deteriorated.
In Comparative Example 11, although the area ratio R ₍₂₀₀₎ of the (220) plane was 50% or less as a characteristic before recrystallization, recrystallization occurred during rolling and R ₍₂₂₀₎ / R _{( 200)} was less than 10. As a result, the characteristics after recrystallization deteriorated and the occurrence of dishdown was confirmed.
According to Reference Examples 1 and 2, it was confirmed that dishdown did not occur even when the area ratio R ₍₂₀₀₎ of the (200) plane was 20% or more as the characteristics after recrystallization.

  From the above, the occurrence of dishdown may not be confirmed in the rolled copper foil, but it is confirmed that the occurrence of dishdown is suppressed by having a predetermined configuration as the characteristic before recrystallization or the characteristic after recrystallization. It was done.

Claims (5)

A rolled copper foil having a main surface composed of a plurality of crystal faces to be used through a recrystallization step,
After the recrystallization step of heating to 200 ° C. and heating for 30 minutes so that all the particles of the rolled copper foil are recrystallized,
When the area ratio of the (200) plane on the main surface obtained from the EBSP (Electron Backscatter Diffraction Pattern) method on the main surface is R ₍₂₀₀₎ , the R ₍₂₀₀₎ is less than 20%,
The rolled copper foil, wherein a maximum dimension of the plurality of crystal planes constituting the main surface is 100 μm or less. A rolled copper foil having a main surface composed of a plurality of crystal faces to be used through a recrystallization step,
The area ratio of the (220) plane to the main surface, obtained from an EBSP (Electron Backscatter Diffraction Pattern) method for the main surface, is R _(220), and the area ratio of the (200) plane to the main surface is R _(200). When
Said R ₍₂₂₀₎ is 20% or more and 50% or less, and satisfy | fills relational expression R ₍₂₂₀₎ / R ₍₂₀₀₎ > = 10. After the recrystallization step of heating to 200 ° C. and heating for 30 minutes so that all the particles of the rolled copper foil are recrystallized,
R ₍₂₀₀₎ is less than 20%,
The rolled copper foil according to claim 2, wherein a maximum dimension of the plurality of crystal faces constituting the main surface is 100 μm or less. It is an object for flexible printed wiring boards, and thickness is 7 micrometers or more and 50 micrometers or less, The rolled copper foil in any one of Claims 1-3 characterized by the above-mentioned. The rolled copper foil according to any one of claims 1 to 4, wherein a tensile strength after a recrystallization step of heating to 200 ° C and heating for 30 minutes is 180 N / mm ² or more.

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