JP6360654B2 - Rolled copper foil for flexible printed wiring boards - Google Patents

Description

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

  A flexible printed wiring board (FPC) is obtained by bonding a metal as a conductive layer and a flexible insulating substrate typified by a resin film. In general, a copper foil is used for the conductive layer, and a rolled copper foil having excellent flexibility is used particularly for applications that require flexibility.

  A general FPC manufacturing process is as follows. First, the copper foil is bonded to the resin film. For joining, there are a method of imidizing by applying heat treatment to a varnish applied on a copper foil, and a method of laminating a resin film with an adhesive and a copper foil. The copper foil with a resin film joined by these steps is referred to as CCL (copper-clad laminate). Thereafter, wiring is formed by etching to complete the FPC.

  Flexibility required for rolled copper foil for FPC is becoming stricter as electronic devices become lighter, shorter, and more functional, and improvements in properties related to flexibility have been made from various viewpoints. For example, JP 2010-280191 A (Patent Document 1) is given as a prior art that focuses on the crystal grain size, and here, the shape is restored to the original shape even when bending deformation is applied at the location where the FPC is bent. A rolled copper foil that can suppress the problem of springback is disclosed.

In Patent Document 1, “the lower the density of crystals in the copper foil, that is, the larger the average crystal grain size, the easier the strain in the crystal moves when the copper foil is deformed by bending. Therefore, if the density of crystals in the copper foil is low, the tensile strength tends to be low, and thus there is a tendency to suppress springback. ”Heat treatment is performed for thermocompression bonding with the resin. In this case, a rolled copper foil that is heated at 150 ° C. or higher and 400 ° C. or lower for 1 minute or longer, has an average crystal grain size of 100 μm or more after heat treatment, and has a tensile strength of less than 150 N / mm ² has been proposed.

In Patent Document 1, the rolled copper foil is obtained by processing a copper foil material by hot rolling and cooling it as quickly as possible after hot rolling. Next, it is described that the hot-rolled copper foil material is manufactured by repeating annealing and cold rolling and processing to a desired thickness. And in thermocompression bonding with the resin, by heating at 150 ° C. or more and 400 ° C. or less for 1 minute or more, the crystals in the copper foil are recrystallized, the average crystal grain size becomes 100 μm or more, and after thermocompression bonding The tensile strength of is less than 150 N / mm ² .

  Moreover, in order to obtain the said copper foil, after manufacturing copper foil by rolling, only when heat-pressing the said copper foil to a resin film, it heats at 150 degreeC or more and 400 degrees C or less for 1 minute or more, It is described that it is important to increase the degree of processing in the final rolling process performed after the final annealing to 94% or more.

In JP 2009-292090 A (Patent Document 2), a highly flexible two-layer flexible copper paste is applied to a two-layer flexible copper paste laminate by controlling the crystal orientation and structure of the copper foil after lamination processing. A laminated board is obtained. Specifically, it is a two-layer flexible copper-clad laminate obtained by laminating a base resin and a copper foil, wherein the average crystal grain size of the cross-section of the copper foil after lamination is 20 μm or more. A two-layer flexible copper-clad laminate is described. As a method for producing the two-layer flexible copper-clad laminate, it is described that the heating conditions at the time of laminating the base resin and the copper foil are controlled. As an example, the copper foil reaches 200 ° C. When the copper foil is heated for 4 seconds or more, further kept at 200 ° C. for 30 minutes, and then cooled to room temperature, the 200-plane X-ray diffraction intensity ratio I / I ₀ measured at room temperature is 40 or more. A method for producing a two-layer flexible copper-clad laminate is described in which, after using and laminating and heating the copper foil and the base resin, post-heating is further performed at a temperature of 350 ° C. or more for 30 minutes or more. ing.

JP 2010-280191 A JP 2009-292090 A

  Thus, the improvement of the characteristic regarding the flexibility of a rolled copper foil has been performed conventionally. However, for example, in a vehicle-mounted FPC, vibration resistance is also required, and there is a demand for a rolled copper foil that is less likely to have a decrease in conductivity due to vibration. However, a conventional rolled copper foil does not have sufficient vibration resistance. .

  Then, this invention makes it one subject to provide the rolled copper foil which was excellent also in vibration resistance in addition to bending resistance. Moreover, this invention makes it another subject to provide FPC provided with such a rolled copper foil.

  The present inventor has intensively studied to solve the above problems, and the rolled copper foil obtained by a predetermined manufacturing method grows to a crystal grain size of 100 μm or more when heat-treated at 400 ° C. for 1 hour. It was found that a copper foil having such characteristics is advantageous in vibration resistance. Further, when a vibration test is performed on the rolled copper foil, a fine crack is generated over the entire surface of the vibration part, which causes stress concentration. It has been found that it has a soothing effect.

  The present invention has been completed based on the above findings. In the first aspect, when heat treatment is performed at 400 ° C. for 1 hour, the average crystal grain size of the cross section parallel to the rolling direction is 100 μm or more. It is a rolled copper foil.

  In the second aspect, the present invention is a rolled copper foil having an average crystal grain size of 100 μm or more in a cross section parallel to the rolling direction.

  In the third aspect, the present invention is a rolled copper foil having a characteristic that a shear band is formed on the surface of the vibration part after the “vibration test A” defined in the specification.

  In one embodiment of the rolled copper foil according to the third aspect of the present invention, the surface of the vibration part after the “vibration test A” defined in the specification is applied to the observation field of 10 μm × 10 μm square in the vertical direction. And 10 to 30 share bands are formed in the lateral direction.

  In one embodiment of the rolled copper foil according to the first, second and third aspects of the present invention, the thickness of the copper foil is 50 to 300 μm.

  In one embodiment of the rolled copper foil according to the first, second and third aspects of the present invention, the Cu concentration is 99.8% by mass or more, the oxygen concentration is 0.05% by mass or less, and Ag, Sn , B, Zr, and Ti have a composition with a total concentration of 0.003 to 0.03% by mass.

  In one embodiment of the rolled copper foil according to the first, second and third aspects of the present invention, the Cu concentration is 99.9% by mass or more, the oxygen concentration is less than 0.01% by mass, and Ag, Sn , B, Zr, and Ti have a composition with a total concentration of 0 to 0.03% by mass.

  In one embodiment of the rolled copper foil according to the first, second and third aspects of the present invention, it is used as a conductor material for a flexible printed wiring board.

  In one embodiment of the rolled copper foil according to the first, second and third aspects of the present invention, the flexible printed wiring board is for vehicle use.

  This invention is a flexible copper clad laminated board provided with the copper foil which concerns on this invention in the 4th side surface.

  In the fifth aspect, the present invention is a flexible printed wiring board obtained by processing the flexible copper-clad laminate according to the present invention.

  According to the present invention, a rolled copper foil excellent in vibration resistance in addition to flex resistance is provided. The rolled copper foil according to the present invention is particularly useful as a conductor layer of, for example, an in-vehicle FPC.

It is a SEM photograph which copied the shear band formed on the surface of the vibration part after carrying out vibration test A about an example of rolled copper foil concerning the present invention. The vertical and horizontal lines for counting the number of share bands are exemplarily written on the SEM photograph of FIG. It is a photograph which shows the attachment state of the loop-shaped test piece at the time of performing a vibration test.

  The copper foil base material used in the present invention is a rolled copper foil. The rolled copper foil is superior to the electrolytic copper foil in that it has high strength, can cope with an environment in which vibration continuously occurs, and has high bending resistance. In the present invention, “copper foil” includes copper alloy foil. There is no restriction | limiting in particular as a material of copper foil, What is necessary is just to select suitably according to a use or a required characteristic. The Cu concentration in the copper foil is preferably 99.8% by mass or more, more preferably 99.85% by mass or more, and more preferably 99.9% by mass or more for reasons of crystal grain growth and ensuring high conductivity. Even more preferably. However, even if the Cu concentration is too high, it leads to an increase in cost, so 99.999% by mass or less is preferable, and 99.995% by mass or less is more preferable. The oxygen concentration in the copper foil is preferably less than 0.01% by mass because, when cuprous oxide increases, it adversely affects the formation of the shear band and leads to the generation of pinholes during rolling. It is preferable that it is mass% or less, for example, can be 0.0001 mass% or more and less than 0.01 mass%. As a copper foil satisfying such conditions, for example, oxygen-free copper (OFC) standardized in JIS-H3510 or JIS-H3100 can be used.

  Also, copper alloys with addition of Sn, Ag, B, Zr, Ti, Fe, In, Te, Zn, etc., Cu—Ni—Si based copper alloys with addition of Ni, Si, etc. to oxygen-free copper, Cr Copper alloys such as Cu-Zr-based and Cu-Cr-Zr-based copper alloys to which Zr and the like are added can also be used. In particular, it is easy to grow crystal grains, strength and elongation of copper foil by adding one or more elements selected from the group consisting of Ag, Sn, B, Zr and Ti in total of 0.03% by mass or less. From the viewpoint of If the total content of Ag, Sn, B, Zr, and Ti exceeds 0.03% by mass, the strength is further improved, but the elongation is lowered and the workability may be deteriorated. More preferably, the total content of Ag, Sn, B, Zr and Ti is 0.02% by mass or less. The lower limit of the total content of Ag, Sn, B, Zr and Ti is not particularly limited, but for example, 0.001% by mass can be set as the lower limit. If the total content of Ag, Sn, B, Zr and Ti is less than 0.001% by mass, the desired effect cannot be obtained, and the content is too small to control the content. There is a case. Preferably, the lower limit of the total amount of Ag, Sn, B, Zr and Ti is 0.003% by mass or more, more preferably 0.004% by mass or more, and most preferably 0.005% by mass or more.

  Similarly, when the above copper alloy is used for the copper foil according to the invention of the present application, the oxygen concentration in the copper foil is preferably less than 0.01% by mass, and preferably 0.005% by mass or less. More preferably, when a copper alloy is used, it is acceptable that the oxygen concentration in the copper foil is somewhat high. Specifically, the oxygen concentration is allowed to be 0.05% by mass or less, and typically 0.01 to 0.03% by mass. For this reason, the tough pitch copper prescribed | regulated to JIS-H3100, for example can also be used as a copper raw material.

  There is no restriction | limiting in particular in the thickness of copper foil, What is necessary is just to select suitably according to a required characteristic. Generally, it is 1 to 300 μm, but when used as a conductor layer of a flexible printed wiring board, it is possible to obtain higher flexibility and vibration resistance when the copper foil is thinned. From such a viewpoint, the thickness of the copper foil is generally 2 to 50 μm, typically about 5 to 20 μm. However, for applications such as in-vehicle use where large current flows and heat generation due to energization is particularly disliked, copper foil is used from the viewpoint of reliably transmitting electrical signals without disconnection while ensuring conductivity and heat dissipation. Since it should be relatively thick, in such a case, the thickness is preferably 50 μm or more, and more preferably 70 μm or more. However, if the thickness is excessively large, it may be difficult to remove the conductor layer by etching. Therefore, the thickness is preferably 300 μm or less, and more preferably 150 μm or less.

  In one aspect, the rolled copper foil according to the present invention is heated at 400 ° C. for 1 hour, so that the crystal grain size of the cross section parallel to the rolling direction is 100 μm or more, preferably 110 μm or more, more preferably 120 μm or more, and even more. Preferably, it has a characteristic that it can be 130 μm or more. However, it is not necessary to extremely increase the crystal grain size, and the crystal grain size after the heat treatment is usually 180 μm or less.

  In the present invention, the average crystal grain size of the cross section parallel to the rolling direction is measured as follows. The film is cut by FIB (focused ion beam) or CP (Cross-Section Polisher) so that the entire thickness of the foil can be observed with a length of 50 μm or more in the rolling direction. Thereafter, SEM observation is performed, and the average crystal grain size is measured by the cutting method of JIS H0501.

  In another aspect, the rolled copper foil according to the present invention has a characteristic that a shear band is formed on the surface of the vibration part after the “vibration test A” defined below. It is preferable that 10 to 30 shear bands are formed in the vertical direction and the horizontal direction, respectively, and more preferably 20 to 26 are formed per 10 μm × 10 μm square observation visual field. The vibrating part refers to a looped part when the FPC test piece is set.

  When the shear band is observed with an SEM, as shown in FIG. 1, the shear band is a grid-like streak pattern that enters a direction of about 45 ° with respect to the rolling direction. In the present invention, as illustrated in FIG. 2, a stripe in the right direction of about 45 ° with respect to the rolling direction is used as a vertical shear band, and a stripe in the left direction of about 45 ° with respect to the rolling direction is used as a shear in the horizontal direction. A band. In FIG. 2, 25 shear bands and 26 shear bands are observed in a 10 μm × 10 μm square observation field of view.

“Vibration test A” is performed according to the following procedure. A polyimide film having a thickness of 50 μm is laminated on the front and back of the rolled copper foil under the lamination condition of hot pressing at 180 ° C. for 2 hours to prepare a double-sided FCCL. Then, eight circuit etchings with a length of 120 mm and a line and space of 0.3 mm × 0.3 mm were formed, and finally, a 50 μm-thick polyimide coverlay film was hot-pressed on both sides at a temperature of 180 ° C. for 1 hour. Lamination is performed to prepare an FPC test piece having a length of 150 mm and a width of 15 mm.
About the obtained FPC test piece, a vibration test is implemented based on a JIS-D1601 sweep vibration endurance test. Specifically, both ends are fixed in a loop shape with a loop dimension L = 20 mm, and a vibration test is performed at a frequency of 5 to 170 Hz / 5 min, an amplitude width of 0.6 mm, a vibration acceleration of 45 m / s ² , and a test temperature of −35 to 115 ° C. The resistance increase rate of the test piece when a constant current (1.0 mA) is applied to the test piece is recorded, and the time until the resistance increase rate of the test piece reaches 20% is measured. The test temperature was maintained at room temperature (20 ° C.) for 10 minutes, then gradually decreased to −30 ° C. over 1.5 hours, held at −30 ° C. for 10 minutes, and then increased to 115 ° C. over 1.5 hours. The cycle of holding at 115 ° C. for 10 minutes and lowering to room temperature (20 ° C.) over 1 hour is repeated. The vibration test is completed when the resistance increase rate of each test piece reaches 20%.
In addition, as shown in FIG. 3, a loop dimension refers to the distance from the fixed location of a test piece to the tip of a test piece.

  The copper foil which concerns on this invention can be manufactured as follows, for example. First, after pure copper raw materials such as electrolytic copper oxygen-free copper and tough pitch copper are melted and an alloy element is added as necessary, the molten metal is cast to produce an ingot having a thickness of about 100 to 300 mm. Adjustment of the oxygen concentration in the melting step can be performed by techniques known to those skilled in the art, such as carbon sealing of the molten metal and release to the atmosphere. Then, after performing hot rolling, annealing and cold rolling are repeated, and the copper foil base material after final cold rolling is obtained. The higher the rolling reduction here, the easier the crystal grains grow by the subsequent annealing. Therefore, the degree of rolling reduction in the final cold rolling is 80% or more, more preferably 90% or more, and still more preferably 95% or more. In addition, when manufacturing copper foil with large thickness, it exists in the tendency which cannot secure a large reduction rate in final cold rolling (because it is difficult to anneal in a state where plate thickness is thick). Therefore, in the case of a copper foil having a thickness of 35 μm or more after the final cold rolling, considering the ease of actual production, the reduction ratio of the final cold rolling is preferably 96% or less, and 95% or less. Is more preferable, and it is further more preferable to set it as 93% or less.

  Next, this copper foil base material is annealed at 400 to 500 ° C. for 1 hour or longer. Annealing is preferably performed in an inert gas atmosphere such as nitrogen or Ar for the reason of preventing oxidation. It is also possible to anneal in a vacuum. By annealing at 400 ° C. or higher for 1 hour or longer, it is possible to sufficiently grow crystal grains of the copper foil, and a copper foil in which a shear band is easily formed when vibration is applied is obtained (in the present invention). This is referred to as the formation of a Shebandan nucleus.) In the case of a copper foil having a large thickness, it is difficult to control the crystal grains inside, and thus such high temperature and long time annealing is particularly necessary. Moreover, even if the annealing temperature is too high, it is inconvenient, and by setting it to 450 ° C. or less, an effect that the crystal grain size is not coarsened more than necessary can be obtained. A longer annealing time is advantageous for appropriate growth of crystal grains and nucleation of shear bands, and it is preferable to anneal for 1 hour or longer. However, it is not necessary to anneal excessively, and the production efficiency is also lowered, so that it is preferably 2 hours or less, and more preferably 1.5 hours or less.

  A flexible copper-clad laminate (FCCL) can be manufactured by laminating and bonding the rolled copper foil after annealing on one or both sides of a flexible insulating substrate made of polyester, polyimide, or the like. As an adhesion method, an adhesive made of a thermosetting resin such as epoxy is used, and a copper foil and a polyimide resin film are bonded to each other and heat treatment is performed, or a varnish containing polyamic acid which is a precursor of a polyimide resin Is coated on a copper foil and cured by heating to form a polyimide film on the copper foil. When laminating copper foil on both sides, after forming a single-sided copper clad laminate, there are a method of crimping the copper foil layer by hot pressing, and a method of sandwiching a polyimide film between two copper foil layers and crimping by hot pressing. is there. These heat treatments are generally carried out at 100 to 250 ° C. for 30 to 150 minutes. There is also a method of laminating a copper foil and a resin with an adhesive without going through a heat treatment step.

  As described above, in the FCCL manufacturing process, heat treatment is often performed for bonding the insulating substrate and the copper foil. Therefore, the annealing process after the final cold rolling described above can be used as the heat treatment. However, since it is difficult to obtain a copper foil having the intended characteristics of the present invention under the general heat treatment conditions at the time of bonding described above, the heat treatment at the time of bonding is performed at 400 to 500 ° C. for one hour or longer. By changing to, the copper foil having the characteristics according to the present invention and the adhesion to the insulating substrate can be simultaneously performed.

  It is possible to manufacture a flexible printed wiring board (FPC) by forming wiring according to a known procedure using the FCCL according to the present invention as a material. For example, apply an etching resist to the copper foil surface of the FCCL only on the necessary part as the conductor pattern, spray the etching solution onto the copper foil surface to remove the unnecessary copper foil, form the conductor pattern, and then peel off the etching resist -The method of removing and exposing a conductor pattern is mentioned. After forming the conductor pattern, it is common to apply a protective coverlay film. Such FPCs are FPCs used for movable parts in hard disks, hinge parts and slide sliding parts of mobile phones, printer head parts, optical pickup parts, movable parts of notebook PCs, etc. in electronic and electrical equipment. To do. In particular, the FPC according to the present invention uses a relatively large thickness of copper foil and is required to have vibration resistance, especially for in-vehicle use (particularly FPC used around transmissions and engines) and automatic machine controllers (automatic transfer lines). It is suitable as an FPC for control of equipment moving on an equal rail.

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

<Manufacture of rolled copper foil>
Ingots having respective compositions shown in Table 1 in which predetermined elements were added to tough pitch copper (TPC) or oxygen-free copper (OFC) were melt cast. After this was hot-rolled, annealing and cold rolling were repeated, and the final cold rolling was performed at the rolling reduction shown in Table 1 and adjusted to the thickness shown in Table 1. Finally, annealing was performed under the conditions described in Table 1 in an Ar atmosphere to obtain each copper foil. In Comparative Example 3, special electrolytic copper foil (EDC) having a thickness of 35 μm was used, and annealing was performed in an Ar atmosphere at 400 ° C. for 1 hour.

<Manufacture of FPC>
After performing roughening treatment with electrodeposited copper particles at a thickness of 50 μm on the front and back of each obtained rolled copper foil, a polyimide film with a thickness of 50 μm is laminated on the front and back under lamination conditions of hot pressing at a temperature of 180 ° C. for 2 hours, A double-sided FCCL was made. Then, eight circuit etches with a length of 120 mm and a line and space of 0.3 mm × 0.3 mm are formed, and finally, a polyimide coverlay film with a thickness of 50 μm is hot-pressed on both sides at a temperature of 180 ° C. for 1 hour. Thus, each test piece of FPC having a length of 150 mm and a width of 15 mm was produced.

<Crystal grain size>
The average crystal grain size of the cross section parallel to the rolling direction of the copper foil was measured by the JIS H0501 cutting method by performing SEM observation according to the procedure described above after the FPC was produced.
The average crystal grain size on the surface of the copper foil was determined by peeling the polyimide film of the measurement part using an alkaline solution and an organic solvent to expose the copper foil surface after the FPC was produced, and then polishing the surface by electropolishing. Observation was performed and measurement was performed by the cutting method of JIS H0501.

<Vibration test>
About each obtained FPC test piece, the vibration test was implemented based on the JIS-D1601 sweep vibration endurance test. The above-mentioned test piece is looped with a loop dimension L = 20 mm, and both ends are fixed, and a vibration test is performed at a frequency of 5 to 170 Hz / 5 min, an amplitude width of 0.6 mm, a vibration acceleration of 45 m / s ² , and a test temperature of 35 to 115 ° C. The resistance increase rate of the test piece when a constant current (1.0 mA) was applied to the test piece was recorded, and the time until the resistance increase rate of the test piece reached 20% was measured. The test temperature was maintained at room temperature (20 ° C.) for 10 minutes, then gradually decreased to −30 ° C. over 1.5 hours, held at −30 ° C. for 10 minutes, and then increased to 115 ° C. over 1.5 hours. The cycle of holding at 115 ° C. for 10 minutes and then lowering to room temperature (20 ° C.) over 1 hour was repeated. The test apparatus used F-400BM-E04 fully automatic vibration test apparatus by Shin-Nippon Sokki Co., Ltd. and temperature-humidity test apparatus VC-500DAR (33) M3C3R by Emic Co., Ltd. were used. The vibration test was terminated when the resistance increase rate of each test piece reached 20%.

<Electrical evaluation>
The continuity of the test piece after the vibration test was measured with a tester. The case where there was continuity was indicated as ◯, and the case where there was no continuity was indicated as x. Those with an evaluation of x are considered to have been disconnected immediately after reaching a resistance increase rate of 20%.

<Share band>
The polyimide film is peeled off from the FPC test piece after the vibration test using an alkaline solution and an organic solvent, the surface of the vibrating copper foil is observed with an SEM, and the vertical and horizontal shear bands per unit area (10 μm × 10 μm) are observed. Was measured. The measurement was performed twice, and the average value was taken as the measured value.

  The results are shown in Table 1.

  The results are shown in Table 1. In Examples 1 to 16, when heat treatment was performed at 400 ° C. for 1 hour, the average crystal grain size of the cross section parallel to the rolling direction was 100 μm or more, so that the vibration resistance time was longer than that of the comparative example having the same foil thickness. Could get. And in Examples 1-16, the shear band was observed after the vibration test.

In Comparative Examples 1 to 3, tough pitch copper was used as a material, but the crystal concentration was not sufficiently developed because the oxygen concentration was too high.
In Comparative Examples 4 to 6, the annealing conditions were inappropriate, and the crystal grains did not develop sufficiently. However, when the annealing conditions were 400 ° C. × 1 hour, the average cross-sectional grain size exceeded 100 μm.
Although the comparative example 7 made the special electrolytic copper foil as a material, the crystal grain did not fully develop.

Claims (7)

When heat treatment is performed at 400 ° C. for 1 hour, the average crystal grain size of the cross section parallel to the rolling direction is 100 μm.
The rolled copper foil which has the characteristic of becoming more than m, is 50-300 micrometers in thickness, and is any one of (1)-(3) below.
(1) Oxygen-free copper (2) Cu concentration is 99.8% by mass or more, oxygen concentration is 0.05% by mass or less, and the total concentration of Ag, Sn, B, Zr and Ti is 0.003 to 0.003. Copper foil having a composition of 03% by mass (3) Cu concentration is 99.9% by mass or more, oxygen concentration is less than 0.01% by mass, and the total concentration of Ag, Sn, B, Zr and Ti is 0-0 Copper foil having a composition of 0.03% by mass The rolled copper foil whose average crystal grain diameter of a cross section parallel to a rolling direction is 100 micrometers or more, thickness is 50-300 micrometers, and is any one of (1)-(3) below.
(1) Oxygen-free copper (2) Cu concentration is 99.8% by mass or more, oxygen concentration is 0.05% by mass or less, and the total concentration of Ag, Sn, B, Zr and Ti is 0.003 to 0.003. Copper foil having a composition of 03% by mass (3) Cu concentration is 99.9% by mass or more, oxygen concentration is less than 0.01% by mass, and the total concentration of Ag, Sn, B, Zr and Ti is 0-0 Copper foil having a composition of 0.03% by mass The characteristic is that 10-30 shear bands are formed in the vertical and horizontal directions per 10 μm × 10 μm square observation field on the surface of the vibration part after the “vibration test A” defined in the specification. A rolled copper foil having a thickness of 50 to 300 μm and any one of (1) to (3) below.
(1) Oxygen-free copper (2) Cu concentration is 99.8% by mass or more, oxygen concentration is 0.05% by mass or less, and the total concentration of Ag, Sn, B, Zr and Ti is 0.003 to 0.003. Copper foil having a composition of 03% by mass (3) Cu concentration is 99.9% by mass or more, oxygen concentration is less than 0.01% by mass, and the total concentration of Ag, Sn, B, Zr and Ti is 0-0 Copper foil having a composition of 0.03% by mass The rolled copper foil as described in any one of Claims 1-3 used as a conductor material of a flexible printed wiring board.   The rolled copper foil according to claim 4, wherein the flexible printed wiring board is for in-vehicle use.   The flexible copper clad laminated board provided with the rolled copper foil as described in any one of Claims 1-5. A flexible printed wiring board obtained by processing the flexible copper-clad laminate according to claim 6.