JP2014015674A - Rolled copper foil and copper-clad laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide rolled copper foil having improved bent part deposition resistance, and a copper-clad laminate using the same.SOLUTION: The copper foil uses oxygen free copper comprising 30 to 100 ppm Sn as a base material, the area ratio of the (200) face in the main surface after heat treatment at 300°C for 5 min is 0.65 or higher, and the copper foil has a thickness t of 5 to 50 μm.

Description

  The present invention relates to a copper clad laminate in which a rolled copper foil is bonded to one side of a substrate, and in particular, a rolled copper foil with improved bending resistance of a copper foil used for bonding a substrate, and the use thereof The present invention relates to a copper-clad laminate.

  For example, a printed wiring board (FPC: Flexible Printed Circuit) is generally obtained by bonding a copper foil and a base material such as a synthetic resin by thermocompression bonding, or by applying a varnish such as a synthetic resin to the copper foil side and drying. A copper-clad laminate is formed, and then a circuit using a photoresist is printed to form a target circuit, and then unnecessary copper portions are removed by etching to form a circuit.

  Copper foils used for printed wiring boards are roughly classified into rolled copper foils and electrolytic copper foils. In particular, rolled copper foil exhibits bending characteristics superior to electrolytic copper foil, and has been generally used as a wiring material for movable parts such as hinge parts and slide parts of mobile phones.

  In recent years, mobile phones called slate-type smartphones that do not have hinges or slides have become widespread, but printed wiring boards have been increasingly bent and mounted to reduce size and space. . This is different from the conventional repeated bending in the elastic deformation region of copper foil having a relatively large bending radius (bending radius of 0.5 to 2 mm), which is so-called sliding bending, in the conventional slide portion. The bending radius is small (the bending radius is 0.5 mm or less), and the bending deformation is performed once or several times in the plastic deformation region of the copper foil.

  As described above, the bending deformation in the case where a bent portion (haze) such as a folded portion is provided on the member is generally referred to as goby folding deformation. Since it is a deformation in the plastic deformation region, it is greatly different from the knowledge about the sliding bending characteristics so far. For mounting a printed wiring board, one goby folding is sufficient, but in reality, several goby folding may be added due to handling during mounting or correction of the mounting position, and also from the viewpoint of reliability. Copper foil that can withstand several goby folds has been required.

  For example, Patent Document 1 discloses a printed wiring board that includes columnar copper crystal particles and has an elongation rate at 25 ° C. of 5% or more, which makes it difficult for the electrolytic copper foil to break. It has been reported that it can be obtained.

  Moreover, in patent document 2, it is reported that the goblet folding-proof characteristic of a rolled copper foil can be improved by making the work hardening index | exponent after 0.3 hour annealing at 350 degreeC into 0.3 or more and 0.45 or less.

JP 2007-335541 A JP 2011-136357 A

  However, the present inventors have investigated copper foils that are widely used at present, and in particular, electrolytic copper foils have been observed to break once or twice even with a thickness of 18 μm, and with one goat fold at a thickness of 12 μm. It was.

  In the rolled copper foil, breakage of the rolled copper foil was observed similarly at a thickness of 18 μm four times and at a thickness of 12 μm two times or three times. This indicates that the rolled copper foil is superior to the electrolytic copper foil with respect to the cross-fold resistance. Therefore, in patent document 1 about an electrolytic copper foil, it is thought that sufficient goblet folding resistance cannot be obtained.

  However, even with a rolled copper foil having an elongation percentage larger than that of the electrolytic copper foil, the goblet folding resistance is not sufficient. Considering that the copper foil tends to be thinner in the future, the result of the rolled copper foil with a thickness of 12 μm is not fully satisfactory.

  The anti-seize fold characteristics differ depending on the thickness of the copper foil, and it has been clarified by the present inventors that a thicker copper foil has better anti-sag fold characteristics. And the total thickness is 50 μm or less, and the copper foil thickness is not clear. That is, there is a possibility that the required anti-sag fold characteristics cannot be obtained with a copper foil having a thickness of 18 μm or 12 μm, which is currently widely used in flexible printed wiring boards.

  Thus, when using a conventional rolled copper foil, the number of goby folds when the thickness is 18 μm is 4 times, and when the thickness is 12 μm, the limit is 2 or 3 times. Further improvement has been difficult.

  Accordingly, an object of the present invention is to provide a rolled copper foil having improved sufficient bending resistance, in particular, goby folding resistance, and a copper-clad laminate using the rolled copper foil.

According to a first aspect of the invention,
The base material is oxygen-free copper containing 30 ppm or more and 100 ppm or less of Sn,
The area ratio of the (200) plane on the main surface after heat treatment at 300 ° C. for 5 minutes is 0.65 or more,
A rolled copper foil having a thickness t of 5 μm or more and 50 μm or less is provided.

According to a second aspect of the invention,
The rolled copper foil as described in the 1st aspect whose maximum valley depth Rv of at least any one of the said main surface or its back surface is 1.5 micrometers or less is provided.

According to a third aspect of the invention,
After the heat treatment at 300 ° C. for 5 minutes, and in a state of being bonded and bent on at least the surface of the polyimide film, in a goby folding test in which a load of 3 kg is applied to the bent portion,
The number of times X of bending until breakage on the peak side of the bent part is a relational expression by a bending radius Bp on the peak side of the bent part and a constant C specific to the material,
X = 65Bp-C
The rolled copper foil as described in the 2nd aspect with which the said constant C will be 6 or less is provided.

According to a fourth aspect of the invention,
In a goby folding test in which a load of 3 kg is applied to a bent portion having a bend radius of 0.125 mm on the valley side after being heat-treated at 300 ° C. for 5 minutes and bonded to both sides of a 25 μm-thick polyimide film and bent. And
The number of times of bending X until the break on the mountain side of the bent portion is a relational expression according to the thickness t,
X-1 = At
The rolled copper foil in any one of the 1st-3rd aspect with which inclination A is 0.17 or more is provided.

According to a fifth aspect of the present invention,
When the thickness t is 12 μm, the rolled copper foil according to the third or fourth aspect is provided in which the number of times X of bending until the break is 4 or more.

According to a sixth aspect of the present invention,
When the thickness t is 18 μm, there is provided the rolled copper foil according to any one of the third to fifth aspects in which the number of times of bending X until the break is 6 or more.

According to a seventh aspect of the present invention,
The rolled copper foil in any one of the 1st-6th aspect whose workability from the last annealing process is 93% or more is provided.

According to an eighth aspect of the present invention,
A copper plating layer is formed on at least one of the main surface or the back surface thereof,
The rolled copper foil in any one of the 1st-7th aspect whose maximum valley depth Rv of the said main surface in which the said copper plating layer was formed, or its back surface is 1.5 micrometers or less is provided.

According to a ninth aspect of the present invention,
The rolled copper foil according to any one of the first to eighth aspects is laminated on at least one side of the resin layer to be a base material,
There is provided a copper clad laminate in which the rolled copper foil is subjected to a heat treatment under annealing conditions.

  The present invention exhibits an excellent effect that a rolled copper foil having sufficient bending resistance and a copper-clad laminate using the rolled copper foil can be provided.

It is a figure which shows the relationship between the copper foil thickness of the conventional rolled copper foil and electrolytic copper foil, and the frequency | count of bending until a fracture | rupture. It is a figure which shows the relationship between the area ratio of the (200) plane which concerns on Examples 1-9 and Comparative Examples 1-12, and the frequency | count of bending until a fracture | rupture. It is a figure which shows the relationship between the maximum valley depth Rv which concerns on Examples 10-15 and Comparative Examples 13-17, and the frequency | count of bending until a fracture | rupture. It is a figure which shows the relationship between the area ratio of the maximum valley depth Rv / (200) surface and the constant C which concern on Examples 16-21 and Comparative Examples 18-21. It is a figure explaining the goby folding test concerning an example and a comparative example. It is a figure which shows the relationship between the bending radius Bp of the peak side in the goby folding test with respect to the rolled copper foil which concerns on one Embodiment and reference example of this invention, and the frequency | count of bending until a fracture | rupture.

<Knowledge obtained by the present inventors>
Below, copper foil and the number of goby folds will be described.

  The number of times the copper foil is repeatedly bent until the copper foil breaks due to the goby bending deformation depends on the material and thickness of the copper foil.

  FIG. 1 shows the relationship between the number of times the copper foil breaks and the thickness of the copper foil during the goby folding test of the rolled copper foil and the electrolytic copper foil.

  This goby folding test is performed on a double-sided flexible substrate (2L FCCL: 2 Layer Flexible Copper Clad Laminate, that is, a double-sided flexible copper-clad laminate), on both sides of a polyimide film having a thickness of 25 μm. A load of 3 kg is placed on the bent portion and the number of times to break is measured.

  According to this, with electrolytic copper foil, it breaks once or twice at 18 μm, and rolled copper foil has better anti-slipping properties than electrolytic copper foil, 4 times at 18 μm, 2 times or 3 times at 12 μm. Yes, this is the limit. Therefore, when it is going to obtain 4 times or more of bending times until it breaks, it is understood that the rolled copper foil requires a copper foil thickness of 18 μm or more.

The following relationship is established from FIG. 1 between the copper foil thickness (t) and the number of bending times (X) until breakage.
X-1 = At
Here, X is the number of times of bending until breakage (times), A is the slope of the graph (a constant determined by the material), and t is the copper foil thickness (μm).

  The rolled copper foil in FIG. 1 has a slope A = 0.15 from the figure, and if the slope A is increased, the number of times of bending until breakage can be increased. For example, even when the thickness of the copper foil is 12 μm, it is necessary to use a material having an inclination A = 0.17 or more in order to obtain four times of bending until breakage. In the case of a material having an inclination A = 0.27, the number of bendings is 6 times or more at a copper foil thickness of 18 μm.

  In order to obtain such a rolled copper foil, the present inventors paid attention to the crystal orientation of the rolled copper foil. And when the area ratio of the crystal | crystallization of the predetermined orientation which occupies for the rolling surface of rolled copper foil increases, it discovered that the frequency | count of bending until a fracture | rupture could be increased even if it is the same thickness.

  At the same time, the present inventors conducted further intensive studies to obtain a rolled copper foil having high goblet folding resistance. As a result, it was found that not only the crystal orientation but also the unevenness of the surface of the rolled copper foil had a great influence on the goblet folding resistance.

  The present invention is based on these findings found by the inventors.

<One Embodiment of the Present Invention>
Hereinafter, a preferred embodiment of the present invention will be described in detail.

(1) Configuration of Rolled Copper Foil The rolled copper foil according to the present embodiment is, for example, oxygen-free copper (OFC) or tough pitch copper (TPC) containing 30 ppm to 100 ppm of tin (Sn). Copper) is used as a base material. The thickness t of the rolled copper foil is, for example, 5 μm or more and 50 μm or less.

  Moreover, the rolled copper foil which concerns on this embodiment has an area ratio (henceforth (200) area ratio) of (200) plane in the rolling surface as a main surface after heat processing for 5 minutes at least 300 degreeC. It is comprised so that it may be 65 or more. Such heat treatment is, for example, annealing applied to the rolled copper foil in the manufacturing process of the flexible printed wiring board.

  In the rolled copper foil according to the present embodiment, it is preferable that the maximum valley depth Rv of at least one of the rolled surface and the back surface thereof is 1.5 μm or less. At this time, a copper plating layer may be formed on at least one of the rolled surface of the rolled copper foil or its back surface, and the maximum valley depth Rv of the rolled surface or its back surface on which at least the copper plating layer is formed is 1. It may be less than 5 μm.

  In addition, for example, a rolled copper foil used for applications such as a flexible printed wiring board is subjected to a roughening treatment on the surface, and may improve the adhesion with a resin layer serving as a base material such as a polyimide film. Also in the rolled copper foil which concerns on this embodiment, the roughening process may be given to at least any one of the rolling surface or its back surface. However, in this case, the above-mentioned maximum valley depth Rv is a value excluding the surface roughness due to the roughening treatment, that is, a value before the roughening treatment.

((200) surface area ratio)
As described above, as a result of researches focusing on the crystal orientation of the rolled copper foil, the present inventors have found that a rolled copper foil having a higher (200) area ratio has a higher number of bends until breakage. .

  Here, the (200) area ratio means that the crystal orientation of the surface (rolled surface) of the rolled copper foil is measured using SEM-EBSP (Scanning Electron Microscope-Electron Backscattering Pattern), and the (200) plane orientation is measured in the measurement region. Indicates the area ratio occupied by crystal grains having

  The rolled copper foil is annealed and softened, and the number of bendings until breakage is such that the cubic orientation, which is the crystal texture of copper, develops and the bending characteristics are improved, and the (200) area ratio in the rolled surface is 0. When it is 4 or more, the number of times of bending until breakage can be increased even with the same thickness.

  Here, in order to obtain the number of bendings of 6 times or more at a copper foil thickness of 18 μm, the (200) area ratio needs to be 0.65 or more. Moreover, even if it is 4 times or more with a copper foil thickness of 12 μm, the (200) area ratio needs to be 0.65 or more.

This is, for example, the following expression (1) derived from FIG.
X-1 = At (1)
For example, the inclination A = 0.25 or more.

  Here, as described above, the goby folding test is performed on a double-sided flexible substrate (2L FCCL) in which a rolled copper foil having the same thickness t (μm) is bonded to both sides of a 25 μm-thick polyimide film. At this time, a load of 3 kg was applied to a bent portion having a bend radius of 0.125 mm on the valley side (bent inner side), and the rupture on the mountain side (bent outer side) of the bent portion, that is, the rolled copper foil disposed on the mountain side The number of bending times X (times) until rupture is measured. At this time, the slope A of the graph given by Equation (1) is determined by the material such as the crystal orientation of the rolled copper foil, and the number of times until the predetermined material breaks (the number of goby folds) is predicted from the value of the slope A. Can do.

  That is, for example, when it is attempted to obtain four times of bending up to breakage when the rolled copper foil has a thickness of 12 μm, an inclination A = 0.17 is required. Moreover, when it is going to obtain the bending frequency | count of 6 times until a fracture | rupture in thickness 18micrometer of rolled copper foil, inclination A = 0.27 is needed. The rolled copper foil of this embodiment has an inclination A = 0.25, substantially satisfies the number of times of bending 6 times at a thickness of 18 μm, and more reliably satisfies the number of times of bending 4 times at a thickness of 12 μm.

  In the case of only oxygen-free copper or tough pitch copper, the electrical conductivity is good, but the softening temperature is as low as 200 ° C., and by adding Sn, the softening temperature becomes 250 ° C., and the heat resistance can be improved with an appropriate electrical conductivity. .

(Maximum valley depth Rv)
In addition, as described above, the inventors of the present invention have conducted research focusing on the properties of the surface of the rolled copper foil, and as a result, found that a rolled copper foil with fewer surface irregularities has a higher number of bendings until breakage. It was.

  For example, a concave portion called an oil pit is often recognized on the rolled surface of the rolled copper foil after the final cold rolling step described later. Such oil pits are generated by biting of rolling oil at the time of rolling, and are different from the unevenness caused by, for example, the roughening treatment described above.

  That is, for example, when the surface of the rolled copper foil after the roughening treatment is observed, it can be seen that irregularities due to the roughening treatment exist on the surface of the rolled copper foil, separately from the oil pits. In addition, it can be seen that the unevenness due to the roughening treatment bites into the base material side such as a polyimide film and contributes to the improvement of the adhesion. On the other hand, the oil pit does not contribute to the adhesion with the base material. It is not the unevenness caused by the roughening treatment, but the depth of the recesses such as oil pits that affect the anti-sag folding characteristics.

  According to the present inventors, including such oil pits, when there are recesses on the rolled surface of the rolled copper foil or on the back surface thereof, cracks occur in the rolled copper foil as a starting point in the goby folding test, etc. It breaks. At this time, the possibility of breakage increases regardless of whether or not the concave portion exists on the side in contact with the base material.

  In the rolled copper foil according to the present embodiment, the maximum valley depth Rv of at least one of the rolled surface and the back surface thereof is 1.5 μm or less, such a state in which such concave portions are reduced, or at least the depth is shallow. State. For this reason, generation | occurrence | production of such a crack is suppressed and a goblet folding-proof characteristic can be improved. Here, the maximum valley depth Rv is one of the surface roughnesses defined in JIS B 0601: 2001. According to JIS B 0601: 2001, the maximum valley depth Rv is the maximum value of the depth from the roughness average line obtained by the surface roughness measurement to the valley bottom.

  By the way, in above-mentioned description, Formula (1) was derived from the result of the goby folding test with respect to the double-sided flexible board which bonded the rolled copper foil on both surfaces of the polyimide film.

Here, after taking into account the knowledge about the maximum valley depth Rv, the thickness of the polyimide film, the bend radius Bp on the mountain side, and the like are incorporated as variables to obtain the following formula (2),
X = 65Bp-C (2)
Can be derived.

That is, the goblet folding test here is a flexible substrate (FCCL) in which a total of n pieces of rolled copper foil having a thickness t _Cu (μm) are bonded to one or both sides of a polyimide film having a thickness t _PI (μm). ). At this time, a load of 3 kg is applied to the bending portion of the bending radius Bv (mm) on the valley side, and the number of bending times X (times) until the fracture of the rolled copper foil arranged on the mountain side is measured. The peak-side bending radius Bp (mm) at this time is expressed by the following equation (3).
Bp = n · t _Cu (× 10 ⁻³ ) + t _PI (× 10 ⁻³ ) + Bv (3)
Here, n is the number of rolled copper foils to be bonded, and n = 1 when bonded to one side and n = 2 when bonded to both sides. In the formula (3), “× 10 ⁻³ ” is for unit conversion (μm → mm).

  At this time, the constant C in the equation (2) is a material-specific constant determined by a material such as crystal orientation of the rolled copper foil. According to the present inventors, it has been found that the constant C has a correlation with the area ratio of the (200) plane that the rolled copper foil has after heat treatment and the maximum valley depth Rv of the surface of the rolled copper foil.

  As in the above equation (2), the bending radius Bp on the peak side is proportional to the number of times of bending X until breakage. This is shown in the graph of FIG.

  FIG. 6 is a diagram showing the relationship between the peak-side bending radius Bp and the number of bendings until breakage in the goby folding test for the rolled copper foil according to the present embodiment and the reference example. The horizontal axis in FIG. 6 is the peak-side bending radius Bp (mm), and the vertical axis is the number of times of bending (times) until fracture. Further, in the figure, black rhombus (♦) marks are plots of the rolled copper foil according to the present embodiment in which the area ratio of the (200) plane is 0.92, and in the figure, the black square (■) marks are ( It is a plot of the rolled copper foil which concerns on the reference example whose area ratio of 200) plane is 0.33.

  As shown in FIG. 6, the higher the area ratio of the (200) plane, the smaller the constant C, that is, the absolute value of the intercept with the vertical axis of the graph. From the value of the constant C, it is possible to predict the number of times until the predetermined material breaks (number of goby folds). That is, for example, as described above, a rolled copper foil having a thickness of 12 μm or 18 μm is bonded to both surfaces, and the polyimide film has a thickness of 25 μm and a valley-side bending radius of 0.125 mm. If the rolled copper foil shows the constant C equivalent to the rolled copper foil of a comparison object, it can be said that their anti-strip properties are equivalent.

  In the rolled copper foil in the present embodiment, for example, the constant C is 6 or less. In addition, when it is going to obtain the bending frequency | count of 4 times until a fracture | rupture in thickness 12 micrometers of rolled copper foil, the constant C should just be 7 or less. Moreover, when it is going to obtain the bending frequency 6 times until a fracture | rupture in thickness 18micrometer of rolled copper foil, the constant C must be 6 or less. The rolled copper foil of this embodiment has a constant C of 6 or less, satisfies the number of bending times of 6 at a thickness of 18 μm, and more reliably satisfies the number of bending times of 4 at a thickness of 12 μm.

(2) Manufacturing method of rolled copper foil First, an example of manufacturing conditions for obtaining a rolled copper foil having a (200) area ratio of 0.65 or more will be described.

  These are merely examples, and do not define the method for producing the rolled copper foil of the present invention.

  In the rolled copper foil according to the present embodiment, Sn is added to oxygen free copper (OFC) or tough pitch copper (TPC) in an amount of 30 ppm to 100 ppm to form an ingot, which is hot-rolled, and then cold-rolled. Rolling and strain relief annealing are repeated to produce a thickness of 5 μm to 50 μm.

  That is, the rolled copper foil is manufactured based on an ingot obtained by melting and casting oxygen-free copper or tough pitch copper. When dissolved, add 30-100 ppm of Sn. When Sn exceeds 100 ppm, the heat resistance becomes excessively high, and the rolled copper foil does not recrystallize due to heat applied to the copper foil in the manufacturing process of the flexible printed wiring board. Since the rolled copper foil is recrystallized by heating in the manufacturing process of the flexible printed wiring board, it exhibits bending characteristics and goby folding characteristics. Therefore, excessive heat resistance is a cause of impairing FCCL characteristics.

  In the hot rolling process, the ingot is first stretched by hot rolling to a thickness of 2.5 mm to become a plate material. Then, it rolls to predetermined thickness in the repeating process which repeats cold rolling and annealing. Thereafter, in the final annealing step, the plate material is subjected to final annealing to obtain an annealed fabric. In the final cold rolling step, the annealed dough is subjected to final cold rolling. In this case, cold rolling may be repeated a plurality of times (a plurality of passes) until a target final thickness is obtained.

At this time, the degree of processing from the final annealing step is set to 93% or more to obtain a rolled copper foil. The degree of processing is defined by the following formula (4).
Degree of processing (%) = (final annealing thickness−final thickness) / final annealing thickness × 100 (4)

  In order to obtain the characteristics required in this embodiment, the degree of processing needs to be 93% or more and less than 99%. If it is less than 93%, the amount of strain applied is small, so the copper foil is difficult to soften. If the degree of work is higher than 99%, too much strain is applied, so that the rolled copper foil is recrystallized by the heat of processing during cold rolling, and the strain is released. Will decline.

  Moreover, in the above manufacturing process, an example of manufacturing conditions for obtaining a rolled copper foil having a surface maximum valley depth Rv of 1.5 μm or less will be described.

  As described above, the oil pits that contribute to the recesses on the surface of the rolled copper foil are generated regardless of the state of the crystal orientation of the rolled copper foil and the difference in material. That is, such an oil pit causes free plastic deformation in which, for example, rolling oil is caught between a roll to be rolled and a roll at the time of rolling such as a final cold rolling process, and the dough is not subjected to the restriction of the roll. Caused by.

  Therefore, for example, by adjusting the roll roughness and the viscosity of the rolling oil in the final cold rolling step, the oil pits can be reduced. In other words, by reducing the roll roughness and the viscosity of the rolling oil, the rolling oil can be prevented from entering due to the intrusion of the rolling oil into the irregularities of the roll and the fluidity of the high viscosity rolling oil being lowered. Therefore, generation | occurrence | production of an oil pit can be suppressed.

  In addition, for the recesses that have already occurred on the surface of the rolled copper foil after the final cold rolling process, including oil pits, for example, by filling the recesses with copper plating that smoothes the surface of the rolled copper foil, Can be reduced. The copper plating layer can be formed on one side or both sides of the rolled copper foil.

  In addition, as mentioned above, you may perform a roughening process to the rolled copper foil which concerns on this embodiment. The roughening treatment can be performed using various known techniques. However, even in this case, the numerical value of the maximum valley depth Rv is a value before the roughening process. That is, in the rolled copper foil according to the present embodiment, the maximum valley depth Rv is preferably 1.5 μm or less after the final cold rolling or at least after the copper plating.

  By heating the obtained rolled copper foil in the atmosphere at 300 ° C. for 5 minutes, the (200) area ratio can be 0.65 or more.

  Thereby, the rolled copper foil of this invention can be made into the rolled copper foil which has sufficient bending resistance.

  In addition, the rolled copper foil obtained as mentioned above can be used not only as an application of a printed wiring board but also as an application of a negative electrode material of a lithium ion secondary battery, for example.

(3) Manufacturing method of copper clad laminated board The above-mentioned heat processing may be performed as an annealing process in the manufacturing process of a flexible printed wiring board, for example. The manufacturing process of the flexible printed wiring board includes, for example, a manufacturing process of a flexible substrate (FCCL) as a copper-clad laminate and a circuit that forms a circuit by removing unnecessary copper foil portions by etching using a photoresist. A forming process and the like are included.

  Moreover, the manufacturing process of a copper clad laminated board is the heat processing process (annealing process) which heat-processes on the rolled copper foil which concerns on this embodiment on annealing conditions, and at least single side | surface of the resin layer used as a base material, such as a polyimide film And a laminating step of laminating the rolled copper foil.

  The heat treatment under annealing conditions is at least the requirements of the present embodiment, that is, the conditions under which the rolled copper foil is annealed to such an extent that the slope A of formula (1) and the constant C of formula (2) are satisfied. Refers to heat treatment. The combination range of the heat treatment temperature and time can be adjusted as appropriate, for example, at 300 ° C. for 1 minute to 30 minutes, and the time can be 5 minutes. Alternatively, it may be 2 minutes to 60 minutes at 270 ° C., or 10 seconds to 5 minutes at 350 ° C.

  At this time, the heat treatment step and the lamination step may be performed simultaneously. That is, for example, when the rolled copper foil is bonded to the resin layer using a thermosetting adhesive or the like, or when the rolled copper foil is bonded directly to the resin layer without using an adhesive or the like. If the pressure conditions are set to 300 ° C. or higher, for example, 5 minutes or longer, as in the above-described annealing conditions, the rolled copper foil can also be annealed.

  By the above, the rolled copper foil which concerns on this embodiment is laminated | stacked on the at least single side | surface of the resin layer used as a base material, The rolled copper foil which concerns on this embodiment which has passed through the heat processing on annealing conditions A flexible substrate (FCCL) as a laminate is manufactured.

  As described above, in the present embodiment, the degree of work is set to 93% or more, and then, for example, by heating at 300 ° C. for 5 minutes, sufficient bending resistance, more specifically, rolling having goby folding characteristics. Copper foil and copper clad laminate can be provided.

  Examples 1 to 21 will be described together with Comparative Examples 1 to 21.

(Evaluation of rolled copper foil)
Oxygen-free copper or tough pitch copper was dissolved, and if necessary, Sn was added in the amounts shown in Tables 1 and 2 below and cast to produce an ingot. After the ingot was hot-rolled, cold rolling and strain relief annealing were repeated to produce a rolled copper foil having a thickness of 6 μm to 18 μm.

  At this time, in order to change the workability, the thickness in the final annealing was appropriately changed. In the final cold rolling after the final annealing step, a roll having an axial surface roughness, that is, an arithmetic average roughness Ra of 0.1 μm or less was used. The kinematic viscosity of the rolling oil was 4 cSt to 7 cSt. Some rolled copper foils were subjected to copper plating or etching.

  More specifically, in Examples 1 to 9 and Comparative Examples 1 to 12, the amount of Sn added was changed to see the influence of the composition of the rolled copper foil. Moreover, in order to see the influence of a work degree, the work degree in the last cold rolling process was changed, respectively.

  Moreover, in Examples 10-15 and Comparative Examples 13-17, in order to see the influence of other rolling conditions, the surface roughness of the axial direction of the roll and the kinematic viscosity of the rolling oil were changed. Moreover, in order to see the influence of the surface treatment with respect to the rolled copper foil, a copper plating layer was formed on the surface in the rolled copper foil according to some examples, and the surface was etched in the rolled copper foil according to some comparative examples. .

At this time, as copper plating, after the rolled copper foil after rolling is degreased and pickled to remove the rolling oil, smooth copper using a copper plating solution having the following composition is used for the rolled copper foil. Plating was performed. For the copper plating solution, copper sulfate pentahydrate (CuSO ₄ .5H ₂ O) 200 g / L, sulfuric acid (H ₂ SO ₄ ) 100 g / L, Leveler and Brightna (CU-BRITE TH- manufactured by Sugawara Eugene Corporation) R III) was used.

  Moreover, in Examples 16-21 and Comparative Examples 18-21, in order to see the influence of the bending radius Bp of the peak side, the thickness of the rolled copper foil or the polyimide film was changed, respectively.

  The rolled copper foil which concerns on Examples 1-21 and Comparative Examples 1-21 was obtained by the above.

  The maximum valley depth Rv was measured for the rolled copper foil thus obtained. The measurement concerned was performed using Keyence Co., Ltd. laser microscope VK-8700 according to JIS B 0601: 2001. The measurement conditions were an objective lens magnification of 50 times, a cutoff condition λs = 0.25 μm, and λc = 0.8 mm.

  The obtained rolled copper foil was heated in the atmosphere at 300 ° C. for 5 minutes.

  About the rolled copper foil after this heat processing, the area ratio of (200) plane was calculated | required.

  Specifically, the oxide film on the surface was removed with a flat milling apparatus, and SEM-EBSP analysis was performed. The analysis was performed using a scanning electron microscope SU-70 manufactured by Hitachi High-Technologies and an OIM manufactured by TSL. The measurement conditions were an SEM magnification of 200 times, an inclination of 70 degrees, an analysis region of 400 μm × 400 μm, and a measurement pitch of 3 μm.

  The obtained crystal orientation was calculated by a computer, and the area ratio occupied by the (200) plane orientation in the analysis region was calculated as the (200) area ratio.

(Evaluation of flexible substrate)
A flexible substrate (FCCL) was manufactured using the rolled copper foil obtained by rolling. In manufacturing the FCCL, a roughening treatment was performed in advance on one side of the rolled copper foil. That is, the rolled copper foil after rolling was degreased and pickled to remove the rolling oil, and then roughened by electrolytic copper plating. The electrolytic copper plating solution used had a composition of copper sulfate pentahydrate (CuSO ₄ .5H ₂ O) 90 g / L and sulfuric acid (H ₂ SO ₄ ) 100 g / L. The electrolysis conditions were a liquid temperature of 30 ° C., an applied current of 45 A / dm ² , and a time of 3 seconds. The surface roughness of the rolled copper foil after the roughening treatment was 1.1 μm in terms of 10-point average roughness Rz.

  Next, the rolled copper foil and the polyimide film were bonded together to produce FCCL. In this example, Kaneka polyimide film Apical BP (thickness 25 μm) was used as a substrate, and a rolled copper foil was bonded to both sides thereof by a vacuum press. The pressing conditions were a pressure of 5 MPa, a temperature of 300 ° C., and a time of 5 minutes. By the above, FCCL which concerns on Examples 1-21 and Comparative Examples 1-21 was obtained.

  This FCCL was cut into a size of 20 mm × 20 mm and used as a sample 10 for the goby folding test shown in FIG.

  As shown in FIG. 5, in the goby folding test, the sample 10 is bent in a direction perpendicular to the rolling direction, and a load is applied between the upper and lower pressing plates 20t and 20b. This time, the load was 3 kg. Further, the specimen 10 was marked (a) so that the same place was always bent (a), and the SUS plate 20s having a thickness of 0.25 mm was sandwiched between the valley side (inner side) of the bent portion (b) was bent (that is, (B) is bent with a bending radius Bv of 0.125 mm on the valley side.) (C). With a stereomicroscope, the presence or absence of fracture of the rolled copper foil arranged on the mountain side from directly above the bent portion is observed (d). If there is no break, the bent sample 10 is opened, and after being flattened by applying a load, (e) bending is performed again. In this manner, the number of bendings until the peak-side rolled copper foil is broken is determined as the number of goby foldings.

(Evaluation results-influence of composition and processing degree)
The obtained results are shown in Tables 1 and 2. In the compositions of Tables 1 and 2, OFC and TPC represent oxygen-free copper and tough pitch copper, respectively. For example, OFC-Sn 50 ppm indicates that 50 ppm of Sn is added to oxygen-free copper.

  As above-mentioned, in Examples 1-9 and Comparative Examples 1-12, the influence of the composition of rolled copper foil was seen.

  As a result, as in Examples 1 and 2, the rolled copper foil with a thickness of 18 μm in which Sn is added to OFC at 30 ppm to 50 ppm has an (200) plane area ratio of 0.65 or more, and the number of goose folds is 6 times. It was above, and it was excellent in the goblet folding resistance.

  On the other hand, as in Comparative Examples 1 and 2, the rolled copper foil to which Sn is not added does not satisfy the area ratio of the (200) plane even when the degree of processing is increased, and the number of goose foldings is 5 or less. It is had. In addition, as in Comparative Examples 3 and 4, even when Sn is added excessively, the rolled copper foil is not sufficiently softened by the amount of heat received at the time of bonding with the polyimide film, and breaks in about one time in the goby folding test. It has been.

  Also in the rolled copper foil having a thickness of 12 μm, the one in which 50 ppm of Sn was added to the OFC as in Example 8 showed sufficient goblet folding resistance. In contrast, the TPC of Comparative Example 9 to which Sn was not added, the OFC of Comparative Example 10 or the OFC of Comparative Example 11 to which Sn was excessively added deteriorated the goblet folding resistance.

  Moreover, as above-mentioned, in Examples 1-9 and Comparative Examples 1-12, the influence of the work degree in the last cold rolling process was also seen.

  As a result, as in Examples 4 to 7, when the degree of processing was 93% or more and less than 99%, the area ratio of the (200) plane was 0.65 or more, and the goblet folding resistance was also good.

  On the other hand, in Comparative Examples 5 and 6 related to TPC without addition of Sn, as in Comparative Example 6, a sufficient (200) plane area ratio was not obtained even when the degree of processing was 93% or more, and the anti-strip fold characteristics Was not satisfactory. Even when 50 ppm of Sn is added to the OFC, when the degree of processing is less than 93% as in Comparative Example 7 or when the degree of processing is 99% or more as in Comparative Example 8, (200) The area ratio of the surface was less than 0.65, and the goblet folding resistance was also deteriorated.

  Even in the rolled copper foil having a thickness of 12 μm, in Examples 8 and 9 in which the degree of processing was 98%, sufficient goblet folding resistance was obtained. On the other hand, in Comparative Example 12 where the degree of processing was 92%, the goblet folding resistance was deteriorated.

  The graph showing the influence of the composition of the rolled copper foil and the influence of the working degree in the final cold rolling process is shown in FIG. The horizontal axis in FIG. 2 is the area ratio of the (200) plane, and the vertical axis is the number of times of bending (times) until fracture. In the figure, the white triangle mark is a rolled copper foil having a thickness of 18 μm in Examples 1 to 7, the black triangle mark is a rolled copper foil having a thickness of 18 μm in Comparative Examples 1 to 8, and the white square is a rolled copper foil having a thickness of 12 μm in Examples 8 and 9. Copper foils and black squares are rolled copper foils of Comparative Examples 9 to 12 having a thickness of 12 μm.

  As shown in FIG. 2, it can be seen that if the area ratio of the (200) plane of the rolled copper foil is 0.65 or more, sufficient bending resistance, more specifically, goby folding resistance can be obtained.

(Evaluation results-influence of other rolling conditions and surface treatment)
Moreover, as above-mentioned, in Examples 10-15 and Comparative Examples 13-17, the influence of other rolling conditions, such as the surface roughness of the axial direction of a roll and kinematic viscosity of rolling oil, was seen.

  As a result, Example 10 in which the kinematic viscosity of the rolling oil during rolling was 4 cSt and Comparative Example 13 in which the kinematic viscosity of the rolling oil during rolling was 7 cSt were compared as follows. In the case of Comparative Example 13 in which the kinematic viscosity of the rolling oil is high, the amount of rolling oil bitten by the roll during rolling increases, and many oil pits are generated. For this reason, in Comparative Example 13, although the area ratio of the (200) plane was sufficient as 0.65 or more, the number of goby folds decreased to 5. This is considered to be caused by an increase in the maximum valley depth Rv due to frequent oil pits.

  In Examples 11 and 12, rolling was performed using a roll having an arithmetic average roughness Ra of 0.06 μm or less at the time of rolling, whereas in Comparative Example 14, an arithmetic average roughness Ra of 0.10 μm and a relatively coarse roll were used. Rolled. For this reason, in Comparative Example 14, the area ratio of the (200) plane satisfied 0.65, but the maximum valley depth Rv was 1.5 or more, and the number of goby folds decreased to 5 times. Oops. This is thought to be because the amount of rolling oil bitten into the roll during rolling increased due to the surface roughness of the roll, and many oil pits were generated, as in the case of increasing the rolling oil viscosity.

  Moreover, as above-mentioned, in Examples 10-15 and Comparative Examples 13-17, the influence of the surface treatment with respect to rolled copper foil was seen.

  As a result, in Examples 13 to 15 in which the copper plating layer was formed to have a thickness of 0.3 μm on the surface of the rolled copper foil, the maximum valley depth Rv was 1.5 μm or less regardless of the rolling conditions, A high value was also obtained.

  On the other hand, in Comparative Example 15 in which the copper plating layer was similarly formed, although the maximum valley depth Rv was 1.5 or less, the area ratio of the (200) plane was sufficiently reduced because of the TPC without adding Sn. No goblet folding resistance was obtained.

  Moreover, in Comparative Examples 16 and 17, the surface of the rolled copper foil after rolling was etched. The crystal grain boundaries of the rolled copper foil were preferentially removed by the etching solution, and many depressions such as oil pits were generated. For this reason, the maximum valley depth Rv is 1.5 μm or more, and the number of goby folding is reduced.

  FIG. 3 shows a graph representing the influence of other rolling conditions and the influence of surface treatment on the rolled copper foil. The horizontal axis in FIG. 3 is the maximum valley depth Rv (μm), and the vertical axis is the number of times of bending (times) until fracture. In the figure, the white triangle mark is a rolled copper foil having a thickness of 18 μm in Examples 10 to 15 except Example 14, the black triangle mark is a rolled copper foil having a thickness of 18 μm in Comparative Examples 13 to 17 excluding Comparative Example 15, and the black square is This is an 18 μm rolled copper foil using the TCP of Comparative Example 15.

  As shown in FIG. 3, in the example in which the area ratio of the (200) plane of the rolled copper foil was 0.65 or more and the maximum valley depth Rv was 1.5 μm or less, satisfying the goby folding resistance. I understand that.

(Evaluation result-influence of the bending radius Bp on the mountain side)
Moreover, as above-mentioned, in Examples 16-21 and Comparative Examples 18-21, the influence of the bending radius Bp of the mountain side was seen.

  As a result, also in Examples 16 and 17 in which the thickness of the polyimide film was changed, the constant C of the above-described formula (2) was 6 or less, so that the good folding resistance property equivalent to the polyimide film thickness of 25 μm was obtained. Met.

  In Examples 18 and 19, the thickness of the polyimide film was 25 μm, but the bending radius Bp on the peak side was changed by changing the bending radius Bv on the valley side. Also in this case, since the constant C was 6 or less, the same excellent folding resistance characteristic as that obtained when the trough-side bending radius Bv was 0.125 mm was obtained. That is, in Example 18, the number of goby folds is 3 times even under severe conditions of the valley side bend radius Bv 0.075 mm. For example, if the bend side bend radius Bv is 0.125 mm, more goby folds are obtained. Expected to be a number of times.

  In Examples 20 and 21, the bending radius Bp on the peak side was changed by changing the thickness of the rolled copper foil to 6 μm and 9 μm, respectively. Even in this case, since the constant C was 6 or less, the same excellent folding resistance as that obtained when the rolled copper foil had a thickness of 18 μm or 12 μm was obtained.

  On the other hand, in Comparative Examples 18-21, the bending radius Bp on the peak side was changed by changing the thickness of the rolled copper foil and the polyimide film and the bending radius Bv on the valley side using TPC without adding Sn. As a result, the constant C exceeded 6 and the goblet folding characteristics deteriorated. Also in Comparative Example 18 having a polyimide film thickness of 50 μm, the number of goby folds is 6, and it is expected that the number of goby folds will be less than 6 under the condition that the thickness of the polyimide film is reduced.

(Evaluation result-constant C)
Next, from the results of Examples 1 to 21 and Comparative Examples 1 to 21, the correlation between the constant C of the above-described formula (2), the maximum valley depth Rv, and the area ratio of the (200) plane was evaluated.

  Some Examples and Comparative Examples are extracted from Examples 1 to 21 and Comparative Examples 1 to 21, and a graph showing these correlations is shown in FIG. The horizontal axis in FIG. 4 is the ratio of the maximum valley depth Rv to the area ratio of the (200) plane (maximum valley depth Rv / (200) plane area ratio), and the vertical axis is the constant C. In the figure, the white triangle mark is the rolled copper foil according to the example, and the black triangle mark is the rolled copper foil according to the comparative example.

  As shown in FIG. 4, it can be seen that the constant C is 6 or less in any of the examples in which the goby folding resistance was good. In this way, the quality of the goblet folding resistance can be determined from the value of the constant C.

10 Sample 10m Mark 20b Holding plate (bottom)
20s SUS plate 20t holding plate (top)

Claims (9)

The base material is oxygen-free copper containing 30 ppm or more and 100 ppm or less of Sn,
The area ratio of the (200) plane on the main surface after heat treatment at 300 ° C. for 5 minutes is 0.65 or more,
A rolled copper foil having a thickness t of 5 μm or more and 50 μm or less. 2. The rolled copper foil according to claim 1, wherein a maximum valley depth Rv of at least one of the main surface or the back surface thereof is 1.5 μm or less. After the heat treatment at 300 ° C. for 5 minutes, and in a state of being bonded and bent on at least the surface of the polyimide film, in a goby folding test in which a load of 3 kg is applied to the bent portion,
The number of times X of bending until breakage on the peak side of the bent part is a relational expression by a bending radius Bp on the peak side of the bent part and a constant C specific to the material,
X = 65Bp-C
The rolled copper foil according to claim 2, wherein the constant C is 6 or less. In a goby folding test in which a load of 3 kg is applied to a bent portion having a bend radius of 0.125 mm on the valley side after being heat-treated at 300 ° C. for 5 minutes and bonded to both sides of a 25 μm-thick polyimide film and bent. And
The number of times of bending X until the break on the mountain side of the bent portion is a relational expression according to the thickness t,
X-1 = At
The rolled copper foil according to any one of claims 1 to 3, wherein the slope A is 0.17 or more. 5. The rolled copper foil according to claim 3, wherein when the thickness t is 12 μm, the number of bending times X until the breakage is 4 or more. The rolled copper foil according to any one of claims 3 to 5, wherein when the thickness t is 18 µm, the number of bending times X until the breakage is 6 or more. The rolled copper foil according to any one of claims 1 to 6, wherein a working degree from the final annealing step is 93% or more. A copper plating layer is formed on at least one of the main surface or the back surface thereof,
The rolled copper foil according to any one of claims 1 to 7, wherein a maximum valley depth Rv of the main surface or the back surface thereof on which the copper plating layer is formed is 1.5 µm or less. The rolled copper foil according to any one of claims 1 to 8 is laminated on at least one side of a resin layer serving as a base material,
The copper-clad laminate, wherein the rolled copper foil is subjected to a heat treatment under annealing conditions.

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