CN111526674A

CN111526674A - Rolled copper foil, copper-clad laminate, flexible printed board, and electronic device

Info

Publication number: CN111526674A
Application number: CN202010316854.6A
Authority: CN
Inventors: 冠和树; 青岛一贵
Original assignee: JX Nippon Mining and Metals Corp
Current assignee: JX Nippon Mining and Metals Corp
Priority date: 2015-06-05
Filing date: 2015-06-05
Publication date: 2020-08-11
Also published as: CN106304689A

Abstract

The invention relates to a rolled copper foil, a copper-clad laminate, a flexible printed board and an electronic device. [ problem ] to provide a rolled copper foil, a copper-clad laminate, a flexible printed board, and an electronic device, which are excellent in both etching properties and bending properties. [ solution ] A rolled copper foil comprising 99.9% or more by mass of copper, wherein the proportion of crystal grains having an angle difference of 10 degrees or less between the surface and { 102 } is 1% or more and 50% or less after heat treatment under any one of conditions of 350 ℃ x 1 second, 350 ℃ x 20 minutes, or 200 ℃ x 30 minutes.

Description

Rolled copper foil, copper-clad laminate, flexible printed board, and electronic device

This application is a divisional application of chinese application having application number 201510301876.4 (application date is 2015, 6/5), entitled "rolled copper foil, copper-clad laminate, flexible printed circuit board, and electronic device".

Technical Field

The present invention relates to a rolled copper foil suitable for use in FPC (flexible printed circuit) or the like, a copper-clad laminate, a flexible printed circuit, and an electronic device.

Background

As a method of wiring a movable portion of an electronic device or a portion having space restrictions, an FPC (flexible printed circuit) can be used. As the FPC, a copper-clad laminate in which a copper foil and a resin layer are laminated can be used.

The FPC is used after being bent in the device, but the bending radius of the FPC is reduced with the miniaturization of the device, and the improvement of the bending property of the FPC is required. In addition, in consideration of the future popularization of wearable terminals, the FPC is also required to have improved fatigue characteristics. Further, with the miniaturization of FPC wiring, the copper foil is required to be etchable in forming a circuit.

However, the FPC is generally used in a state where the copper foil is recrystallized. When the copper foil is rolled, the crystal is rotated to form a rolled assembly structure. Further, when heat is applied in a step of rolling the rolled copper foil and then annealing or processing the rolled copper foil to a final product, in other words, a step of forming an FPC, recrystallization occurs. Hereinafter, the recrystallized structure after the rolled copper foil is referred to as "recrystallized structure" and the rolled structure before the application of heat is referred to as "rolled structure". The recrystallized structure is significantly affected by the rolled structure, and the control of the rolled structure also allows the control of the recrystallized structure.

Thus, the following techniques are proposed: a technique has been developed for improving bendability by orienting Cube, i.e., (200) plane ({ 100 }), as a recrystallized structure of a rolled copper foil (for example, patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 11-286760.

Disclosure of Invention

Problems to be solved by the invention

However, when the Cube orientation of the copper foil excessively progresses, there is a problem that the etching property is lowered. This is considered because: the Cube texture does not become a single crystal even when it develops, but is in a mixed crystal grain state in which small crystal grains of other orientations exist in the Cube-oriented large crystal grains, and the etching rate changes depending on the crystal grains of each orientation. In particular, the shorter the L/S width of the circuit (fine pitch), the more the problem of etching property occurs. When Cube orientation excessively progresses, the copper foil may become too soft and poor in handling properties.

Therefore, a technique for improving bendability without developing Cube orientation is desired. Note that Cube orientation is a recrystallized assembly orientation of pure copper.

Accordingly, an object of the present invention is to provide a rolled copper foil having excellent etching properties and excellent bending properties, a copper-clad laminate, a flexible printed circuit board, and an electronic device.

Means for solving the problems

The present inventors have focused on { 102 } of a rolled copper foil as a method for improving bendability without developing Cube orientation. When { 102 } is developed on the surface of the sheet, the etching properties equivalent to those of conventional electrolytic copper foil whose Cube orientation is not developed can be secured, and the bendability and bendability can be improved. The reason why { 102 } improves the bendability and the bendability is considered to be that the orientation is low in young's modulus, though not to the extent of Cube orientation. In addition, {100} means (100) plane or (100) orientation.

That is, the rolled copper foil of the present invention contains 99.9% or more of copper by mass, and when heat-treated under any of conditions of 350 ℃x1 second, 350 ℃x20 minutes, or 200 ℃x30 minutes, the proportion of crystal grains having an angular difference of 10 degrees or less from { 102 } on the surface is 1% or more and 50% or less.

The rolled copper foil of the present invention preferably contains 1 or 2 or more selected from Ag, Sn, Zn, Ni, Ti and Zr in a total amount of 10 to 300 mass ppm, and the balance is Cu and unavoidable impurities.

The copper-clad laminate of the present invention is obtained by laminating the rolled copper foil on both surfaces or one surface of a resin layer, and in at least one of the rolled copper foils, the proportion of crystal grains having an angle difference of 10 degrees or less from { 102 } on the surface is 1% or more and 50% or less.

The flexible printed board of the present invention is obtained by forming a circuit on the rolled copper foil using the copper-clad laminate.

The electronic device of the present invention is formed using the flexible printed circuit board.

Effects of the invention

According to the present invention, a rolled copper foil having excellent etching properties and bending properties can be obtained.

Drawings

FIG. 1 is a schematic diagram of a test method for 180 DEG tight bending.

FIG. 2 is a schematic representation of a bend test method.

Detailed Description

The rolled copper foil according to the embodiment of the present invention will be described below. In the present invention,% represents mass% unless otherwise specified. The rolled copper foil according to the embodiment of the present invention is useful for an application in which a copper-clad laminate is produced by laminating the copper foil with a resin, and then a portion other than a circuit portion is removed by etching to produce an FPC.

< composition >

The rolled copper foil contains 99.9% or more of copper by mass. Examples of such a composition include oxygen-free copper defined in JIS-H3510 (C1011) or JIS-H3100 (C1020), tough pitch copper defined in JIS-H3100 (C1100), or phosphorus deoxidized copper defined in JIS-H3100 (C1201 and C1220). The upper limit of the oxygen content contained in copper is not particularly limited, but is generally 500 mass ppm or less, and more generally 320 mass ppm or less.

Further, the alloy may contain 1 or 2 or more elements selected from Ag, Sn, Zn, Ni, Ti and Zr in a total amount of 10 to 300 ppm by mass. In order to develop { 102 }, it is necessary to develop { 112 } in the intermediate annealing (annealing before final cold rolling) of the rolled copper foil, and when these elements are added, the range of conditions for developing { 112 } by the intermediate annealing is widened, so that { 102 } can be developed more reliably, and the production is easy. If the total amount of the above elements is less than 10 mass ppm, the effect of { 112 } development by the intermediate annealing is small, and if it exceeds 300 mass ppm, the conductivity may decrease and the recrystallization temperature may increase, making it difficult to suppress surface oxidation of the copper foil and to recrystallize it in the annealing after the final rolling.

< thickness >

The thickness of the copper foil is preferably 4 to 100 μm, and more preferably 5 to 70 μm. If the thickness is less than 4 μm, the handling properties of the copper foil may be poor, and if the thickness exceeds 100 μm, the flexibility of the copper foil may be poor.

< 102 on the surface of copper foil >

After heat treatment under any one of conditions of 350 ℃ C. × 1 second, 350 ℃ C. × 20 minutes, or 200 ℃ C. × 30 minutes, the proportion of crystal grains having an angle difference of 10 degrees or less between the surface of the rolled copper foil and { 102 } is 1% or more and 50% or less. The "surface" of the rolled copper foil means a surface obtained by polishing the outermost surface by 0.5 to 2 μm by electrolytic polishing.

Here, etching (especially soft etching) is affected by the plane orientation of crystal grains on the surface of the copper foil. The bendability and the bendability are also caused by applying the maximum strain to the surface of the copper foil. This defines the degree of { 102 } development on the copper foil surface (rolled surface). However, when an oxide layer, a rust preventive layer, or the like is present on the surface of the copper foil and it is necessary to remove them, the surface after removal is regarded as the surface of the copper foil. In general, it is considered that when the thickness of the surface of the copper foil is removed by 1 μm or less, the plane orientation can be measured, and there is no difference in orientation between before and after the removal.

Further, crystal grains having an angle difference of 10 degrees or less from { 102 } can be defined as described above because they are regarded as a plane orientation in the vicinity of { 102 }. When the angle difference from { 102 } exceeds 10 degrees, the difference from { 102 } becomes large.

In general, when a rolled copper foil is shipped and manufactured in a state of a "rolled structure", a recrystallized aggregate structure is formed by recrystallization at the time of bonding with a resin layer. Therefore, in order to evaluate the bendability, and etching properties of the copper-clad laminate, it is necessary to target the "recrystallized structure" of the rolled copper foil. On the other hand, the recrystallized structure is not only dependent on the rolled structure, but also greatly varies depending on the temperature condition at the time of recrystallization.

Therefore, in a typical manufacturing method of a copper-clad laminate, the thermal history to which a rolled copper foil is subjected is reproduced in a simulated manner under any of conditions of 350℃ × 1 second, 350℃ × 20 minutes, or 200℃ × 30 minutes, and the state of the copper foil recrystallized in the copper-clad laminate is shown.

Therefore, the heat treatment itself was performed under only any one of the 3 conditions, and was not performed for the same sample 2 times for 350℃ × 20 minutes after performing the heat treatment for 350℃ × 1 second. The proportion of the crystal grains is 1% to 50% both when the heat treatment is performed at 350 ℃ for 1 second and when the heat treatment is performed at 350 ℃ for 20 minutes, for example.

When the crystal grain ratio of the angle difference between the { 102 } and the plane orientation of the copper foil surface, which is within 10 degrees, is 1% or more, { 102 } progresses, and the bendability and bendability of the copper-clad laminate are improved. On the other hand, it is industrially difficult to make the proportion of the above crystal grains more than 50%.

The plane orientation of the surface of the copper foil was measured by EBSD (Electron Back Scattering diffraction). EBSD can measure the crystal orientation near the sample surface with a resolution of the order of nm, and can calculate the change in local crystal orientation (local orientation difference) from the measurement data. From these data, the proportion of crystal grains having an angle difference of 10 degrees or less from { 102 } is calculated.

In regard to EBSD, increasing the measurement area is not preferable because the measurement interval becomes wider and coarse data is obtained. In addition, {100} increases the particle size to about 100 μm when it progresses over the rolled surface, but even in this case, the measurement area is set to 4mm²So that a sufficient number of grains are present in the measurement area. The interval between the measurement points is set to 1 μm or less. At this time, it is difficult to measure 4mm by one measurement²All areas of, thus for random decimationThe obtained part was measured several times to make the total measurement area 4mm²And (4) finishing.

The rolled copper foil of the present invention can be produced to a desired foil thickness by repeating cold rolling and annealing a plurality of times (usually about 2 times) after hot rolling and surface shaving, followed by final recrystallization annealing and final cold rolling. After degreasing the copper foil, one surface (the surface laminated with the resin layer) may be roughened and then subjected to an anti-corrosion treatment to ensure adhesion with the resin layer, and the copper foil may be used for a copper-clad laminate.

The "final recrystallization annealing" refers to the final annealing among the anneals before the final cold rolling.

Here, in order to make { 102 } on the surface of the copper foil progress as described above, the annealing conditions were adjusted so that the integral diffraction intensity ratio (I (200)/I) of X-ray diffraction indicating the degree of crystal development of {100} on the surface of the sheet after the "final recrystallization annealing" and before the final cold rolling was achieved₀(200) In the range of 2 to 10. Intensity (I/I)₀) The intensity (I (200)) of the integrated diffraction intensity of the rolled surface obtained by X-ray diffraction and the integrated diffraction intensity (I (200)) of the surface (200) obtained by X-ray diffraction of fine copper powder₀(200) The ratio) represents the degree of development of the cube organization.

(I (200)/I) above₀(200) Less than 2), the { 200 } will be gathered in the copper foil finally obtained after the final cold rolling, and therefore the { 102 } on the surface of the copper foil will not develop. This is because of (I/I) of the final recrystallization annealing stage₀) Hour(s) and thereafter (I (200)/I) in the case of final cold rolling₀(200) Increased {100} proportion, and { 102 } will not evolve.

On the other hand, the above-mentioned (I (200)/I)₀(200) When the orientation exceeds 10, the orientation of the copper foil surface is randomly approximated, and { 102 } does not progress. This is because (I (200)/I) before the final cold rolling₀(200) When the grain size exceeds 10), orientation which is randomly close to each other when final cold rolling is performed thereafter, and { 102 } does not progress.

As(I (200)/I after the final recrystallization annealing and before the final cold rolling₀(200) 2 to 10) in the temperature raising step, the final recrystallization annealing can be performed at a temperature of 600 ℃ or higher, and the passage time of 200 to 500 ℃ in the temperature raising step is controlled to 5 to 60 seconds. When the passing time is less than 5 seconds, (I (200)/I₀(200) Less than 2, passage time of more than 60 seconds, (I (200)/I)₀(200) ) exceeds 10. The cooling process after the "final recrystallization annealing" is performed by temporarily raising the temperature does not affect the { 102 } generation.

In addition, in order to develop the { 102 } orientation of the copper foil surface, the final cold rolling degree eta is controlled to 2.8 to 3.7. When η is less than 2.8, { 102 } will not progress because the copper foil surface is randomly oriented in the near-field. When η exceeds 3.7, {100} aggregation occurs, and { 102 } on the copper foil surface does not progress.

Note that η = ln (a/B) indicates the cross-sectional area of A, B before cold rolling and after final cold rolling.

The copper-clad laminate of the present invention is obtained by laminating a rolled copper foil having the above-described characteristics on both surfaces or one surface of a resin layer. The resin layer is not particularly limited as long as it has properties applicable to printed wiring boards and the like, and for example, paper base phenolic resins, paper base epoxy resins, synthetic fiber cloth base epoxy resins, glass cloth and seed paper composite base epoxy resins, glass cloth and seed glass non-woven fabric composite base epoxy resins, glass cloth base epoxy resins and the like can be used in rigid PWB applications. In addition, for FPC applications, polyester films, polyimide films, Liquid Crystal Polymer (LCP) films, teflon (registered trademark) films, polyethylene terephthalate films, polyethylene naphthalate films, and the like can be used.

The resin layer itself may be a multilayer.

When a resin layer having low heat resistance such as polyethylene terephthalate is bonded to a copper foil, the copper foil in the "rolled structure" state may not have the "recrystallized structure" depending on the thermocompression bonding conditions at the time of bonding. In this case, the copper foil may be recrystallized by any of the heat treatments 350 ° c. × 1 second, 350 ° c. × 20 minutes, or 200 ° c. × 30 minutes described above, the proportion of crystal grains having an angle difference of 10 degrees or less from { 102 } may be adjusted to 10% or more, and then the copper foil may be bonded to a resin layer to produce a copper-clad laminate.

Further, depending on the configuration of the FPC, only the copper foil on one surface of the copper-clad laminate may be severely bent or bent. For such applications, copper foils may be laminated on both sides of the resin layer of the copper-clad laminate, the copper foil of the present invention may be used on the side of one copper foil to which severe bending conditions are applied, and another copper foil (e.g., an inexpensive electrolytic copper foil) may be laminated on the other side.

As a method for laminating a rolled copper foil and a resin, in the case of rigid PWB applications, the following methods can be mentioned: a method of preparing a prepreg in which a base material such as glass cloth is impregnated with a resin and the resin is cured to a semi-cured state, and laminating a copper foil on the prepreg and heating and pressing the same is provided. In the case of FPC, a copper foil may be bonded to a resin layer such as a polyimide film with an adhesive or may be laminated and bonded under high temperature and high pressure without using an adhesive to produce a copper-clad laminate. In the case of FPC, a copper-clad laminate can be produced by applying a polyimide precursor to a rolled copper foil, followed by drying and curing.

The thickness of the resin (layer) is not particularly limited, and generally about 9 to 50 μm is used. In addition, a resin having a thickness of 50 μm or more may be used. The upper limit of the thickness of the resin is not particularly limited, and is, for example, 150. mu.m.

The copper-clad laminate of the present invention can be used for various flexible printed boards (printed wiring boards (PWBs)). The printed wiring board is not particularly limited, and can be applied to, for example, a single-sided PWB, a double-sided PWB, a multilayer PWB (3 layers or more); from the viewpoint of the kind of insulating substrate material, the present invention can be applied to rigid PWBs, flexible PWBs (fpcs), rigid and seeding flexible PWBs.

Examples

< production of rolled copper foil >

Tough pitch copper or oxygen-free copper to which elements having compositions shown in Table 1 were added was used as a raw material, an ingot having a thickness of 100mm was cast, hot-rolled at 800 ℃ or higher to a thickness of 10mm, and the surface of the oxide scale was shaved. Thereafter, cold rolling and annealing were repeated to obtain a rolled sheet coil having a thickness of 0.5 mm. After the subsequent cold rolling, final recrystallization annealing was performed using the conditions of table 1. Finally, the steel sheet was finished to a predetermined thickness by final cold rolling at the degree of working shown in Table 1 (the thickness of examples 9, 6 and 13 was 9 μm, the thickness of example 7 was 18 μm, and the thickness of other examples and comparative examples 1 to 4 was 12 μm).

In the column of the composition in Table 1, "OFC +30 ppmAg" means that 30ppm by mass of Ag was added to oxygen-free copper OFC in accordance with JIS-H3100 (C1020). In addition, "TPC +200 ppmAg" is Ag added in an amount of 200 mass ppm to Tough Pitch Copper (TPC) in JIS-H3100 (C1100). The same applies to other amounts.

The X-ray diffraction intensity of the {100} plane was measured on the surface of the copper foil after the final recrystallization annealing and before the final cold rolling. Then, the value (I) of the pure copper powder thus obtained was used by X-ray diffraction under the same conditions₀(200): x-ray reflection mean intensity).

The measurement conditions for X-ray diffraction were as follows: incident X-ray source: cu, acceleration voltage: 25kV, tube current: 20mA, divergent slit: 1 degree, scattering slit: 1-degree, light-receiving slit: 0.3mm, diverging longitudinal limiting slit: 10mm, and the monochrome light receiving slit was set to 0.8 mm. Fine copper powder (325 mesh) was used as the pure copper powder.

< crystal orientation >

The final cold-rolled copper foil was subjected to each heat treatment shown in table 1, and then the surface was slightly electropolished to measure EBSD of the surface. The measurement area was set to 4mm in total as described above². The proportion of crystal grains having an angular difference of 10 degrees or less between the plane orientation of the surface and { 102 } was calculated using Analysis software (OIM Analysis by TSL SOLUTIONS LTD) attached to the EBSD apparatus.

The heat treatment at 350 ℃ for 1 second was not considered to be performed at 350 ℃ for 1 second, because the time required for the heat treatment was short even when the copper foil was simply placed in a furnace at 350 ℃. Thus, the copper foil was held between 2 stainless steel plates (SUS 410/thickness 5mm Ra 0.1, Rz 0.6) heated to 350 ℃ for 1 second as heat treatment at 350 ℃ for 1 second.

The heat treatments at 350 ℃ x 20 minutes and 200 ℃ x 30 minutes were performed by leaving the copper foil in a furnace at 350 ℃ and 200 ℃ for a predetermined time.

< production of copper-clad laminate >

The rolled copper foils of the examples and comparative examples in table 1 were laminated with a resin layer by the laminating method shown in table 2, to produce a copper-clad laminate. The rolled copper foil of table 1 was used before the heat treatment of table 1.

With respect to the thickness of the resin layer, example 3 was set to 50 μm; examples 8, 12, 19 were set to 35 μm; in other examples and comparative examples 1 to 4, the thickness was set to 25 μm. Among the resin layers, polyimide and epoxy are thermosetting, and liquid crystal polymer is thermoplastic. The term "polyimide/epoxy" refers to a multilayer resin layer obtained by laminating a polyimide layer and an epoxy layer, and the epoxy layer side is bonded to the copper foil as an adhesive layer as shown in the laminating method "C" described later.

In table 2, when the copper foil is laminated on both sides, the copper foil is laminated on both sides of the resin layer.

In table 2, the lamination method "a" means: a commercially available laminate of a polyimide film or a liquid crystal polymer film having a thermoplastic property and a copper foil was placed between 2 stainless steel plates (SUS 410) heated to 350 ℃, and the laminate was pressed and held for 1 second. The "polyimide film having" thermoplastic properties means: since a typical polyimide film is thermosetting and does not adhere to a substrate even when heat is applied, a polyimide film having a thermoplastic polyimide with a thickness of about 2 μm is added to the surface of the substrate of the polyimide film in advance.

The laminating method "B" is to coat a commercially available polyimide precursor varnish on a copper foil and to dry and cure it. Drying temperature 200 ℃ for 3 minutes, curing 350 ℃ for 30 minutes.

In the laminating method "C", a commercially available epoxy adhesive is applied to a commercially available polyimide film, and then the film is dried to evaporate a solvent in the epoxy adhesive, and further a copper foil is bonded thereto, and then the adhesive is cured (cure). Drying temperature 200 ℃ for 3 minutes, curing 200 ℃ for 30 minutes.

The following evaluation was performed on the obtained copper-clad laminate.

< crystal orientation >

Similarly to the rolled copper foil, the proportion of crystal grains having an angular difference of 10 degrees or less between the plane orientation of the surface and { 102 } was measured with respect to the copper foil surface of the copper-clad laminate. When copper foils were laminated on both sides of the copper-clad laminate, any one of the copper foil surfaces was arbitrarily measured.

< bendability >

The following bending properties and flexural properties were evaluated for samples with a small number of cycles until the test piece was cracked, and for samples with a large number of cycles, using the bending properties.

The 180 ° close bending of the copper-clad laminate was repeated, and the number of times until the copper foil was broken was measured. The surface of the copper foil (curved outer surface) after each bending was observed by a CCD camera for the presence or absence of fracture. A sample which did not break even after being bent 3 times was rated as "O" and a broken sample was rated as "X".

The 180 ° tight bending was performed as shown in fig. 1. First, the test piece was cut into a short strip of 12.7mm × 100mm so that the rolling direction of the copper foil became the longitudinal direction. The test piece S1 was bent in a U-shape at the center portion so that both ends in the longitudinal direction overlapped each other, and horizontally formed in an inverted C-shape so that the longitudinal direction became horizontal, and was attached to a compression tester (universal tester AGS-5kN manufactured by shimadzu) (fig. 1 (a)). Specifically, the test piece S1 was placed on the base 12 of the compression tester, the slider 11 above the test piece S1 was lowered at a speed of 50 mm/min under a load of 98kN (10 kgf), and the load was applied thereto and then held for 5 seconds, thereby completely crushing the test piece S1. Thereafter, the slider 11 was raised, and the test piece S2 with the crushed U-shaped portion was taken out and changed in direction so that the longitudinal direction thereof was vertical to be the test piece S3 ((b) of fig. 1). The test pieces S2 and S3 each had a bent portion C with a U-shaped portion crushed.

Then, the test piece S3 was placed on the base 12 of the compression testing machine with the bent portion C facing upward, the slider 11 above the bent portion C was lowered at the same load and speed as described above, and was held for 5 seconds after the load was applied, thereby completely crushing the test piece S3 (fig. 1 (C) and (d)). Thereafter, the slider 11 is raised, and the test piece S4 in which the bent portion C is crushed and almost flat is taken out, and the bent outer surface Sk of a predetermined region around the bent portion C is observed to determine whether or not there is a fracture ((e) of fig. 1).

< flexibility >

After etching the copper foil of the copper-clad laminate to form a predetermined circuit, a bending test was performed using an IPC (american society for printed circuit industry) bending test apparatus shown in fig. 2. The resistance of the circuit portion was measured in a sliding bending test, and a sample that did not break when the resistance value increased by 15% from the initial state and bent more than 10000 times was evaluated as "o", and a sample that broke before the resistance value increased by 15% from the initial state or at the time of 15% increase was evaluated as "x".

The IPC bending test apparatus has a structure in which a vibration conductive member 3 is coupled to a vibration driver 4, and a test piece 1 is fixed to the apparatus at a total of 4 points of a portion of a screw 2 and a tip portion of the screw 3 indicated by an arrow. When the vibrating portion 3 is driven up and down, the middle portion of the test piece 1 is bent into a hairpin shape with a predetermined radius of curvature r.

The test conditions are as follows: width of test piece: 12.7mm, test piece length: 200mm, test piece orientation: the test piece was taken so that the longitudinal direction thereof was parallel to the rolling direction, and the curvature radius r: 1.5mm, vibration stroke: 25mm, vibration speed: 1500 times/min

When the copper foil is formed on one surface of the copper-clad laminate, the copper foil faces a curved inner surface having a radius of curvature r in fig. 2. When copper foils are laminated on both surfaces of the copper-clad laminate, the surface of the copper foil on which the crystal orientation is measured is etched to form a circuit, and the copper foil on the opposite surface is completely removed by etching. The circuit surface is a curved inner surface having a radius of curvature r in fig. 2.

The etchability was determined by the following circuit linearity and half-etchability. In the case where copper foils are laminated on both surfaces of the copper-clad laminated sheet, the surface of the copper foil on which the crystal orientation is measured is etched.

For circuit linearity, after a long short stripe circuit pattern was formed on the surface of a copper foil of a copper-clad laminate by masking in the width direction to a width of 50 μm and in the length direction, a short stripe circuit having a width of 50 μm was formed on the surface of the copper foil by spray etching using iron chloride at 60 ℃. The circuit width in the width direction was measured by SEM at a pitch of 5 μm in the longitudinal direction of the circuit. In the measurement of 100 points at the above pitch, a case where 3 σ of the normal distribution of the circuit width is within ± 2 μm is regarded as o.

For half etching, etching was performed with a mixed aqueous solution of sodium persulfate (40g/L) and sulfuric acid (20g/L) until the thickness of the copper foil reached half of the initial thickness, the Cross Section was cut with CP (Cross Section Polisher), and then the thickness of the Cross Section was measured with SEM at a pitch of 5 μm along the direction of the etched surface. For the measurement of 100 points at the above-mentioned pitch, a case where 3 σ of the normal distribution of the thickness is within ± 2 μm is regarded as o.

Regarding the evaluation of the etching properties, a case where both the circuit linearity and the half-etching properties were "o" was designated as a comprehensive evaluation, and a case where either the circuit linearity or the half-etching properties were not "o" was designated as a comprehensive evaluation.

The results are shown in tables 1 and 2.

It can be understood from tables 1 to 2 that: in each of the examples, the proportion of crystal grains having an angular difference of 10 degrees or less between the plane orientation of the copper foil surface and { 102 } is 1% or more and 50% or less, and the copper-clad laminate is excellent in all of bendability, bendability and etching properties.

When the copper foil before being laminated on the copper-clad laminate of each example was subjected to heat treatment at 350 ℃x1 second, 350 ℃x20 minutes, or 200 ℃x30 minutes, the proportion of crystal grains having an angular difference of 10 degrees or less between the surface orientation and { 102 } was 1% or more and 50% or less.

On the other hand, in the case of comparative examples 1 and 2 in which the passage time at 200 to 500 ℃ exceeds 60 seconds in the temperature rise process in the final recrystallization annealing of the copper foil, (I (200)/I)₀(200) More than 10, the copper foil surface is randomly oriented in a close manner, { 102 } does not progress, and the proportion of crystal grains having an angular difference of 10 degrees or less between the plane orientation of the copper foil surface and { 102 } is less than 1%. Therefore, in comparative examples 1 and 2, the bendability and the bendability were poor.

In the case of comparative examples 3 and 4 in which the copper foil had a final cold rolling degree η exceeding 3.7, the X-ray diffraction intensity ratio (I (200)/I) after the final recrystallization annealing was₀(200) Less than 2), the { 102 } orientation of the copper foil surface does not progress in the {100} aggregate of the finally obtained copper foil surface, and the proportion of crystal grains having an angular difference of 10 degrees or less between the { 102 } orientation of the copper foil surface is less than 1%. Therefore, in comparative examples 3 and 4, the bending property and the bendability were good, but the etching property was poor.

Claims

1. A rolled copper foil comprising 99.9% by mass or more of copper,

after heat treatment under any condition of 350 ℃ X1 second, 350 ℃ X20 minutes or 200 ℃ X30 minutes, the proportion of crystal grains having an angle difference of 10 degrees or less between the surface and { 102 } is 1% or more and 50% or less.

2. The rolled copper foil according to claim 1, wherein the copper foil contains 10 to 300 ppm by mass of 1 or 2 or more selected from Ag, Sn, Zn, Ni, Ti and Zr in total, and the balance is Cu and unavoidable impurities.

3. A copper-clad laminate comprising the rolled copper foil according to claim 1 or 2 laminated on both or one side of a resin layer,

in at least one of the rolled copper foils, the proportion of crystal grains having an angle difference of 10 degrees or less from { 102 } on the surface is 1% or more and 50% or less.

4. A flexible printed board obtained by forming a circuit on the rolled copper foil using the copper-clad laminate according to claim 3.

5. An electronic device using the flexible printed board according to claim 4.