JP2019214793A - Rolled copper foil, copper-clad laminate, flexible printed wiring board, electronic equipment, and method for manufacturing rolled copper foil - Google Patents

Abstract

To provide a rolled copper foil which has excellent bendability and handleability, and can make productivity of a copper-clad laminate and a flexible printed wiring board excellent; a copper-clad laminate; a flexible printed wiring board; electronic equipment; and a method for manufacturing the rolled copper foil.SOLUTION: A rolled copper foil is a rolled copper foil after final rolling and before recrystallization. An area AT is 20% or more and 45% or less with respect to the surface area of the copper foil, when the area AT is the total of areas A, in which A is the area of regular hexagon in which a distance between each side and a measurement point a is 100 nm, with the measurement point a being the center of the regular hexagon, whose an average value of orientation angle differences between a crystal orientation obtained by irradiating a measurement point a of a metal structure of crystal on a copper foil surface with an electron beam, and a crystal orientation obtained by irradiating a plurality of adjacent measurement points positioned around the measurement point a so as to be separated by 200 nm with an electron beam is 1.5° or more and less than 2.0°.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a rolled copper foil, a copper-clad laminate, a flexible printed wiring board, an electronic device, and a method for producing a rolled copper foil.

  An electronic device is generally composed of a plurality of electronic boards, and a flexible printed wiring board for electrically connecting the electronic boards is provided between the electronic boards. The flexible printed wiring board usually includes an insulating substrate and copper wiring formed on the surface of the substrate. A flexible printed wiring board that connects electronic substrates is subjected to tensile stress and compressive stress due to the difference in thermal expansion and contraction between the two substrates, so that good flexibility and the like are required. Characteristics required for such a flexible printed wiring board include a good bending property represented by MIT flexibility and a high cycle flexibility represented by IPC bending property. Copper foil and copper-resin substrate laminates have been developed (Patent Documents 1 to 3).

JP 2010-10087A JP 2009-111203 A JP 2007-207812 A

  Copper foil used for flexible printed wiring boards is becoming thinner year by year, and currently 18 μm or less is mainstream, and copper foil having a thickness of single μm is also commercialized. In the case of a rolled copper foil, as the thickness is reduced, the workability of rolling is inevitably increased, and a state in which strain is accumulated inside. Further, by making the layer thin, a shear band is easily introduced, and the accumulation of strain is further increased.

  When the accumulation of strain increases, the copper foil becomes hard and breaks immediately, resulting in reduced handling. Further, when the accumulation of the strain increases, the strain accumulated by the heat applied when the copper-clad laminate is manufactured is released, but at this time, the copper foil is easily wrinkled.

  In addition, when a shear band is introduced, crystal grains having a {111} plane parallel to the rolling surface are likely to appear at the location of the shear band after recrystallization. This is not preferable because the Young's modulus is increased and the flexibility is impaired, or it becomes a starting point of a crack in a bending test or a bending test. In addition, it is known that when a copper foil to which a small amount of an element such as Ag is added is used, the flexibility and the like are improved. Becomes noticeable.

  Therefore, the present invention provides a copper-clad laminate, a rolled copper foil having a good productivity of a flexible printed wiring board, a copper-clad laminate, a flexible printed wiring board, an electronic device, It is an object to provide a method for producing a rolled copper foil.

  The present inventors, as a result of intensive studies, by controlling the angle difference of the crystal orientation in the crystal of the rolled copper foil, bending and handling, and, when used for copper-clad laminates, flexible printed wiring boards Has been found to be able to improve the productivity of the product.

  The present invention completed on the basis of the above findings is, in one aspect, a rolled copper foil after final rolling, and before recrystallization, and irradiates an electron beam to a measurement point a of the metal structure of the crystal on the copper foil surface. The average value of the azimuthal angle difference between the obtained crystal orientation and the crystal orientation obtained by irradiating a plurality of adjacent measurement points located around the measurement point a with a distance of 200 nm from the electron beam is 1.5. The center of the measurement point a is not less than 2.0 ° and less than 2.0 °, the area of the regular hexagon in which the distance between the measurement point a and each side is 100 nm is defined as the area A, and the sum of the areas A is defined as the area AT. Then, the AT is a rolled copper foil in which the AT is 20% or more and 45% or less with respect to the surface area of the copper foil.

  In one embodiment of the rolled copper foil of the present invention, the AT is at least 20% and at most 30% based on the surface area of the copper foil.

  In another embodiment, the rolled copper foil of the present invention is a rolled copper foil after final rolling, and before recrystallization, and irradiates an electron beam to the measurement point b of the metal structure of the crystal on the copper foil surface. The average value of the azimuth angle difference between the obtained crystal orientation and the crystal orientation obtained by irradiating the electron beam to a plurality of adjacent measurement points located at a distance of 200 nm around the measurement point b is 0.3 °. The area of a regular hexagon in which the distance between the measurement point b and each side is 100 nm is defined as the area B, and the total of the areas B is defined as the area BT. In this case, the BT is a rolled copper foil having a surface area of 20% or more and 50% or less with respect to the surface area of the copper foil.

  In still another embodiment of the rolled copper foil of the present invention, the BT is at least 30% and at most 50% of the surface area of the copper foil.

  In still another embodiment, the rolled copper foil of the present invention has a thickness of 3 μm or more and 15 μm or less.

  In still another embodiment, the rolled copper foil of the present invention is Ag, Zn, Zr, Cr, Ti, and at least one selected from the group consisting of Sn in a total of 10 mass ppm or more and 500 mass ppm or less. Including.

  In still another aspect, the present invention is a copper-clad laminate manufactured using the rolled copper foil of the present invention.

  In still another aspect, the present invention is a flexible printed wiring board manufactured using the copper-clad laminate of the present invention.

  In another aspect, the present invention is an electronic device manufactured using the flexible printed wiring board of the present invention.

In another aspect of the present invention, the temperature T (K) and the time t (second) after the final rolling are:
T = 473t- ^C (However, -0.03≤C≤-0.02)
This is a method for producing a rolled copper foil in which heat treatment is performed at T and t that satisfy the following.

  According to the present invention, a copper-clad laminate, a rolled copper foil having good productivity of a flexible printed wiring board, a copper-clad laminate, a flexible printed wiring board, an electronic device, A method for producing a rolled copper foil can be provided.

It is a schematic diagram showing the measurement aspect of the crystal orientation of a rolled copper foil. It is explanatory drawing of the 180 degree bending test which concerns on an Example.

(Structure of rolled copper foil)
As the material of the rolled copper foil that can be used in the present invention, tough pitch copper (JIS-H3100 C1100) or oxygen-free copper (JIS-H3100 C1020, JIS-H3510 C1011) can be used.
Furthermore, a copper alloy foil based on tough pitch copper and oxygen-free copper can also be used. The copper alloy foil based on tough pitch copper and oxygen-free copper is specifically, Ag, Zn, Zr, Cr, Ti, and at least one selected from the group consisting of Sn in a total of 10 mass ppm. A copper alloy foil containing at least 500 mass ppm is given.
In this specification, “copper foil” includes a copper alloy foil, and a copper foil formed of “tough pitch copper” and “oxygen-free copper” includes a copper alloy foil based on tough pitch copper and oxygen-free copper. Is also included.

  The rolled copper foil of the present invention is a rolled copper foil after final rolling and before recrystallization, and preferably has a thickness of 3 μm or more and 15 μm or less. If the thickness of the rolled copper foil after the final rolling and before recrystallization is less than 3 μm, the handling of the copper foil will be poor, and if it exceeds 15 μm, the fine pitch property will be reduced. Further, when the thickness of the copper foil is reduced, a fine pitch having a circuit width of 40 μm or less tends to be formed with good linearity, and the tendency is particularly remarkable when the thickness is 12 μm or less. For this reason, the thickness of the rolled copper foil is more preferably 3 to 12 μm.

  The rolled copper foil of the present invention has a crystal orientation obtained by irradiating the measurement point a of the crystal structure of the crystal on the copper foil surface with an electron beam, and a plurality of adjacent measurement points 200 nm apart from the measurement point a. The distance between the measurement point a and each side is centered on the measurement point a in which the average value of the azimuth angle difference from the crystal orientation obtained by irradiating the point with an electron beam is 1.5 ° or more and less than 2.0 °. Is 100 nm, the area of a regular hexagon is defined as area A, and the total of area A is defined as area AT, AT is controlled to 20% or more and 45% or less with respect to the surface area of the copper foil.

  The rolled copper foil of the present invention has a crystal orientation obtained by irradiating the measurement point b of the crystal structure of the crystal on the surface of the copper foil with an electron beam, and a plurality of adjacent measurement points located 200 nm apart from the measurement point b. The center of the measurement point b where the average value of the azimuth angle difference with the crystal orientation obtained by irradiating the point with an electron beam is 0.3 ° or more and less than 0.9 °, and the measurement point b and each side When the area of a regular hexagon having a distance of 100 nm is defined as area B and the total area B is defined as area BT, it is preferable that BT is controlled to 20% or more and 50% or less with respect to the surface area of the copper foil.

  As for the measurement point a, specifically, the measurement point a of the crystal structure of the crystal on the copper foil surface is first determined. The measurement point a has a crystal orientation obtained by irradiating the electron beam and a crystal orientation obtained by irradiating the electron beam to six adjacent measurement points located at a distance of 200 nm around the measurement point a. Is between 1.5 ° and less than 2.0 °. Note that an adjacent measurement point in which the azimuth angle difference between the measurement point and the crystal orientation of the adjacent measurement point is 2.0 ° or more is determined to be a crystal grain boundary, and is not considered in calculating the average value of the azimuth angle difference. . Therefore, for example, when it is determined that two of the six adjacent measurement points are crystal grain boundaries, the crystal orientation obtained by irradiating the electron beam at the measurement point and the remaining four points other than the crystal grain boundary are obtained. The average value of the azimuthal angle difference between the crystal orientation of the adjacent measurement point and the crystal orientation obtained by irradiating the electron beam at the measurement point with the crystal orientation obtained by irradiating the adjacent measurement point with the electron beam It becomes the average value of the angle difference.

  Regarding the measurement point b, specifically, the measurement point b of the crystal structure of the crystal on the copper foil surface is determined. The measurement point b has a crystal orientation obtained by irradiating the electron beam and a crystal orientation obtained by irradiating the electron beam to six adjacent measurement points located at a distance of 200 nm around the measurement point b. Is between 0.3 ° and less than 0.9 °.

  FIG. 1 is a schematic diagram illustrating a measurement mode of the crystal orientation of the rolled copper foil of the present invention. First, measurement points are determined. In FIG. 1 (hereinafter referred to as measurement point 1). A regular hexagon having the measurement point 1 as the center and the distance between the measurement point 1 and each side being 100 nm is determined. Adjacent measurement points (measurement points 2 to 7) are located around the measurement point 1 at a distance of 200 nm from each other. Then, the crystal orientations obtained by irradiating the measurement points 1 to 7 with an electron beam are measured, and the azimuth angle difference between the measurement point 1 and the measurement points 2 to 7 is obtained. When the average value of the azimuth angle differences thus obtained is not less than 1.5 ° and less than 2.0 °, the measurement point 1 is defined as the measurement point a, and the area of the regular hexagon centered on the measurement point a is defined as the area. A. When the average value of the azimuth angle difference is 0.3 ° or more and less than 0.9 °, the measurement point 1 is defined as a measurement point b, and the area of a regular hexagon centered on the measurement point b is defined as an area B.

  Further, for these adjacent measurement points (measurement points 2 to 7), similarly to the measurement point 1, a regular hexagon having a distance of 100 nm from each side with respect to each center is determined. When the regular hexagons are sequentially determined in this manner, the metal structure of the copper foil is filled with a plurality of regular hexagons that are in contact with each other as shown in FIG. Then, for each measurement point, whether the measurement point is a or b is determined in the same manner as described above, and the area A or B is obtained. When the total area A at each measurement point obtained in this way is defined as area AT, AT is 20% or more and 45% or less with respect to the surface area of the copper foil. When the total area B at each measurement point is defined as area BT, BT is preferably 20% or more and 50% or less with respect to the surface area of the copper foil.

  The above-described measurement of the crystal orientation may be performed by a so-called KAM (Kernel Average Misorientation) value of EBSP (Electron Backscattering Pattern) in steps of 200 nm. Locations where the azimuth angle difference is 2 ° or more are omitted because they are crystal grain boundaries. Although the KAM value greatly changes depending on the step interval for measuring the EBSP, the KAM value does not gradually change as the step interval is shortened. In the case of the rolled copper foil of the present invention, the KAM value becomes almost constant if it is 200 nm or less. For this reason, a KAM value measured in 200 nm steps can be used.

  The smaller the ratio of the area AT, the less the accumulation of strain in the copper foil. When the AT is less than 20% of the surface area of the copper foil, the amount of strain accumulation is small and the handleability is improved. It becomes uneven. On the other hand, if the AT exceeds 45% of the surface area of the copper foil, the accumulation of strain is too large, and the handling property is significantly deteriorated. The ratio of the area AT is preferably 20% or more and 30% or less with respect to the surface area of the copper foil. When the ratio of the area AT is 30% or less, the effect of improving the handleability is increased.

  The smaller the ratio of the area BT, the less the accumulation of strain in the copper foil. When the BT is less than 20% of the surface area of the copper foil, the amount of strain accumulation is small and the handleability is improved. It becomes uneven. On the other hand, if BT exceeds 50% of the surface area of the copper foil, recrystallization becomes difficult or the recrystallized particle size becomes uneven. The ratio of the area BT is preferably 30% or more and 50% or less with respect to the surface area of the copper foil. When the ratio of the area BT is 30% or more, the effect of improving the handleability is increased.

  The rolled copper foil of the present invention preferably contains at least 10 mass ppm and not more than 500 mass ppm of one or more selected from the group consisting of Ag, Zn, Zr, Cr, Ti and Sn. By including 10 mass ppm or more in total of one or more selected from the group consisting of Ag, Zn, Zr, Cr, Ti and Sn, the flexibility of the copper foil is improved. In addition, since an element other than copper is included, strain easily accumulates, and handling properties may be deteriorated. Therefore, one or two selected from the group consisting of Ag, Zn, Zr, Cr, Ti, and Sn. It is preferred that the total of the species or more be 500 ppm by mass or less.

(Production method of rolled copper foil)
In the production process of rolled copper foil, electrolytic copper is used as a raw material for pure copper, alloy elements are added as necessary, and then cast to produce an ingot having a thickness of 100 to 300 mm. After hot-rolling this ingot to a thickness of about 5 to 20 mm, cold rolling and annealing are repeated to finish the ingot to a predetermined thickness by cold rolling. At this time, rolling is performed so that the final rolling degree is 90% or more. The final rolling degree is the total degree of rolling for rolling to the thickness of the product after annealing accompanied by recrystallization. When the final rolling degree is 90% or more, the flexibility and bendability of the copper foil are improved. Subsequently, after the final rolling, the temperature T (K) and the time t (second) are:
T = 473t- ^C (However, -0.03≤C≤-0.02)
The heat treatment is performed at T and t satisfying the following. The heat treatment is performed without recrystallization and at a temperature of 1/2 to 3/4 of the recrystallization temperature. The heat treatment time is preferably from 1 to 30 hours. A higher temperature of the heat treatment has an effect of reducing the accumulation of strain in the copper foil, and the effect of improving the handleability is great, but if the temperature is too high, the recrystallization partially deteriorates and the handleability becomes worse. I will. That is, by performing such a heat treatment, the ratio of the area AT and BT of the rolled copper foil of the present invention can be controlled.

(Copper clad laminates, flexible printed wiring boards and electronic equipment)
The copper-clad laminate of the present invention is configured by subjecting the rolled copper foil of the present invention to recrystallization or the like, if necessary, and then bonding an insulating substrate thereto. Further, the flexible printed wiring board according to the present invention can be manufactured by processing a rolled copper foil portion of the copper-clad laminate of the present invention to form a wiring pattern. That is, a flexible printed wiring board according to the present invention includes an insulating substrate and a wiring pattern formed on a surface of the insulating substrate. The insulating substrate used here is not particularly limited as long as it has good flexibility and bendability that can be applied to a flexible printed wiring board. Examples thereof include a polyimide film, a liquid crystal polymer film, and polyethylene naphthalate. Is mentioned. The thickness of the insulating substrate is preferably 12 to 50 μm. If the thickness is less than 12 μm, handling becomes poor, and if it is more than 50 μm, flexibility decreases. The wiring pattern is formed using the above-described rolled copper foil for a flexible printed wiring board. The shape of the wiring pattern is not particularly limited, and may be any shape.

  The copper-clad laminate can be manufactured by laminating a rolled copper foil and an insulating substrate such as a polyimide film or a liquid crystal polymer film having good flexibility and bendability.

  In the case of a polyimide film, in the case of a polyimide film, a thermoplastic polyimide adhesive is applied to a thermosetting polyimide film, dried, laminated with a copper foil, and thermocompressed. As a pressure bonding method, there is a method of performing vacuum hot pressing or a method of laminating using a hot roll. In the case of a polyimide film, a copper-clad laminate is prepared by applying a polyimide precursor to a copper foil, drying and curing.

  The process for producing a flexible printed wiring board from a copper-clad laminate may be performed by a method well known to those skilled in the art. For example, an etching resist is applied only to a portion required as a wiring pattern on a copper foil surface of a copper-clad laminate, and unnecessary copper foil is removed by spraying an etching solution onto the copper foil surface to form a circuit pattern. . Next, a flexible printed wiring board is produced by exposing and removing the etching resist to expose the wiring pattern.

  Various electronic devices can be manufactured by providing the flexible printed wiring board between two electronic substrates and electrically connecting them. The electronic device is not particularly limited, and examples thereof include a liquid crystal display, a car navigation, a mobile phone, a game machine, a CD player, a digital camera, a television, a DVD player, an electronic organizer, an electronic dictionary, a calculator, a video camera, and a printer. Can be

  EXAMPLES Hereinafter, examples of the present invention will be described, but these are provided for better understanding of the present invention, and are not intended to limit the present invention.

Tough pitch copper: TPC (Examples 1-3, 16, Comparative Examples 2, 4) (JIS-H3100 C1100), oxygen-free copper: OFC (Examples 4-15, 17-29, Comparative Examples 1, 3, 5) (JIS-H3100 C1020) was added with the elements shown in Table 1 to produce an ingot. In addition, in Examples 1-7, the ingot was produced using tough pitch copper and oxygen-free copper as they were without using any additional element. Next, the produced ingot was processed into a plate having a thickness of 7 mm by hot rolling, and after removing oxides by surface grinding, cold rolling, annealing, and pickling were repeated. Thereafter, cold rolling was performed to the thickness described in Table 1. At this time, rolling was performed so that the final rolling degree was 90% or more. After the final rolling, as a heat treatment without recrystallization, the temperature T (K) and the time t (second)
T = 473t- ^C (T, t and C are described in Table 1)
The heat treatment was performed so as to satisfy the following.

(Measurement of the ratio of AT and BT)
The KAM value was calculated for each of the copper foils prepared as described above using an electron microscope JEOL FE-SEM and EBSP using analysis software manufactured by TSL. Thus, the area of 500 μm × 500 μm on the copper foil surface was measured, and the above-mentioned area AT and area BT on the measurement surface were determined, and the ratio to the surface area of the copper foil was calculated. The area AT and the area BT were determined by measuring about 625 crystal grains in the range of 500 μm × 500 μm on the surface of the copper foil and calculating the average.

(Handling)
The two rolls heated to 300 ° C. were nipped at a nip pressure of 100 kgf / cm, during which the copper foil was passed through at a tension-free rate of 2 m / min. At this time, the case where wrinkles did not disappear was evaluated as x, the case where wrinkles were reduced by adjusting the line tension was evaluated as ○, and the case where wrinkles did not occur was evaluated as ◎.

(Bendability)
For each copper foil, a test piece was cut into a 12.7 mm x 100 mm strip so that the rolling direction was the longitudinal direction. This test piece S1 was bent in a U-shape at the center so that both ends in the longitudinal direction were aligned with each other, and turned in an inverted C-shape so that the longitudinal direction became horizontal, a compression tester (Shimadzu Corporation) (AGS-5kN) (FIG. 2 (a)). Specifically, the test piece S1 is placed on the pedestal 12 of the compression tester, and the crosshead 11 above the test piece S1 is lowered at a load of 98 kN (10 kgf) at a speed of 50 mm / min. After 5 seconds, the test piece S1 was completely crushed (the number of times the test piece S1 was completely crushed was defined as the number of bendings). Thereafter, the crosshead 11 was raised, and the test piece S2 whose U-shaped portion was crushed was taken out. The test piece S3 was changed in direction so that the longitudinal direction was up and down (FIG. 2B). Each of the test pieces S2 and S3 has a protruding bent portion C whose U-shaped portion is crushed. The outer surface of the bent portion C was observed to check for cracks. If no crack is found, the test piece S3 is placed on the pedestal 12 of the compression tester with the bent portion C facing upward, and the crosshead 11 above the bent portion C is subjected to the same load and speed as described above. The test piece S3 was completely crushed by holding for 5 seconds after applying a load (FIGS. 2C and 2D). Thereafter, the crosshead 11 was raised, and the test piece S4 in which the bent portion C was crushed and became almost flat was taken out. The test piece S4 is used as a test piece S1 until the number of times of bending is three times, and the presence or absence of cracks is checked with a CCD camera. Those that did not crack even after being bent three times were rated as ○, and those that broke were rated as ×.
Table 1 shows the measurement conditions and results.

(Evaluation)
In Examples 1 to 29, AT was 20% or more and 45% or less with respect to the surface area of the copper foil, and the handling property and the bending property were good.
In Comparative Examples 1, 3, and 5, the AT was more than 45% with respect to the surface area of the copper foil, and the handling property was poor.
In Comparative Examples 2 and 4, the AT was less than 20% of the surface area of the copper foil, and the bendability was poor.

11 Crosshead 12 Pedestal S1 Specimen S2 Specimen S3 Specimen S4 Specimen C Bent

Claims (10)

  After the final rolling, and the rolled copper foil before recrystallization, the crystal orientation obtained by irradiating the measurement point a of the crystal structure of the crystal on the copper foil surface with an electron beam, and around the measurement point a A plurality of adjacent measurement points located at a distance of 200 nm are irradiated with an electron beam. The center of the measurement point a having an average value of the azimuth angle difference from the crystal orientation of 1.5 ° or more and less than 2.0 ° is centered. When the area of a regular hexagon in which the distance between the measurement point a and each side is 100 nm is defined as the area A, and the total of the areas A is defined as the area AT, the AT is 20% of the surface area of the copper foil. A rolled copper foil of at least 45% inclusive.   The rolled copper foil according to claim 1, wherein the AT is at least 20% and at most 30% based on the surface area of the copper foil.   After the final rolling, and the rolled copper foil before recrystallization, the crystal orientation obtained by irradiating the measurement point b of the crystal structure of the crystal on the copper foil surface with an electron beam, and around the measurement point b A plurality of adjacent measurement points located at a distance of 200 nm are irradiated with an electron beam, and the average value of the azimuthal angle difference from the crystal orientation obtained from the measurement point b is 0.3 ° or more and less than 0.9 °. When the area of the regular hexagon in which the distance between the measurement point b and each side is 100 nm is defined as the area B and the total of the areas B is defined as the area BT, the BT is 20% of the surface area of the copper foil. The rolled copper foil according to claim 1, which is at least 50%.   The rolled copper foil according to any one of claims 1 to 3, wherein the BT is at least 30% and at most 50% of the surface area of the copper foil.   The rolled copper foil according to any one of claims 1 to 4, having a thickness of 3 µm or more and 15 µm or less.   Rolling according to any one of claims 1 to 5, comprising one or more selected from the group consisting of Ag, Zn, Zr, Cr, Ti and Sn in a total amount of 10 mass ppm or more and 500 mass ppm or less. Copper foil.   A copper-clad laminate produced using the rolled copper foil according to any one of claims 1 to 6.   A flexible printed wiring board produced using the copper-clad laminate according to claim 7.   An electronic device manufactured using the flexible printed wiring board according to claim 8. After the final rolling, the temperature T (K) and the time t (second)
T = 473t- ^C (However, -0.03≤C≤-0.02)
A method for producing a rolled copper foil, wherein a heat treatment is performed at T and t that satisfy the following.

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