TW201733797A - Copper foil, copper-clad laminate, flexible printed circuit board and electronic machine which are hard to generate wrinkles at the time of lamination with a resin layer even though the thickness itself is thin - Google Patents

Abstract

The present invention provides a copper foil, a copper-clad laminate, a flexible printed circuit board and an electronic machine, which are hard to generate wrinkles at the time of lamination with a resin layer even though the thickness itself is thin. A copper foil having a thickness of 3 to 8[mu]m and containing copper of 99.90 mass% or more is provided, whose average length Wsm of the waviness curve element is 2.5 to 20.0 mm, where the waviness curve is obtained by cutting off the short wavelength and the long wavelength components from a cross-sectional curve S of a surface having a length L of 50 mm along the TD (transverse direction) direction in accordance with JIS-B 0601 (2013) under conditions that contour curve filter [lambda]c=2 mm and contour curve filter [lambda]f=25 mm.

Description

Copper foil, copper clad laminate, and flexible printed circuit board and electronic equipment

The present invention relates to a copper foil suitable for use in a copper clad laminate manufactured by a lamination method and a cast method, a copper clad laminate using the same, a flexible printed circuit board, and an electronic device.

A flexible wiring board (FPC) for an electronic device is formed by laminating a copper foil and a resin to produce a copper clad laminate (CCL) and forming a circuit on the copper foil portion of the CCL. A method of producing a CCL is a lamination method in which a resin film having a thermoplastic resin and a copper foil are thermally welded (Patent Document 1), a casting method in which a resin varnish is applied to a copper foil to cure a resin (Patent Document 2), and a double belt. Press method (Patent Document 3) and the like.

The double belt pressing method uses the double belt pressing device 100 shown in Fig. 1. The double belt press apparatus 100 is provided with two seamless steel strips 102a and 102b, and each of the belts 102a and 102b is placed between the inlet roll 120 and the exit roll 122.

When the belts 102a and 102b are brought into close contact with each other, the copper foil 2 and the resin film 4 on the side of the inlet roller 120 are drawn between the belts 102a and 102b, and laminated and heat-pressed in the belts 102a and 102b. The rear exits from the side of the exit roller 122.

By arranging the heating and pressing device 110 and the cooling and pressing device 112 between the respective belts 102a and 102b, The copper foil 2 and the resin film 4 can be thermocompression bonded to manufacture CCL.

In recent years, the flexible wiring board has been required to be reduced in size and thickness. In other words, the copper clad laminate (CCL) substrate or the copper foil for the copper clad laminate used for the substrate as the substrate is also thinner than ever before.

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2005-305729

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2009-286095

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2011-230308

In addition, if the thickness of the copper foil of the copper clad laminate is thin, wrinkles are likely to occur when the copper foil and the resin are laminated, resulting in a decrease in productivity or yield.

In particular, a casting method in which a resin varnish is applied to a copper foil, and if wrinkles are formed in the copper foil, manufacturing becomes difficult. Further, in the lamination method, heat welding is performed using a heating roll, and when tension is applied to the copper foil between the rolls, wrinkles are likely to occur in parallel with the tension direction.

Accordingly, an object of the present invention is to provide a copper foil, a copper-clad laminate, a flexible printed circuit board, and an electronic device which are less likely to wrinkle when laminated with a resin layer even if the thickness thereof is thin.

The present inventors have found that the reason why wrinkles are formed when a thin copper foil and a resin layer are laminated to produce CCL is related to the surface properties of the copper foil.

The surface profile of the copper foil is a height profile (cross-sectional curve) of the surface measured by a roughness meter. However, in the copper foil, a profile of a surface having a length of about 0.1 to 5 mm is generally obtained, and the profile curve is obtained from the profile curve. Indicators such as surface roughness.

However, the results of studies conducted by the present inventors have clarified that the surface property (corrugation curve) obtained from the profile curve of the long-distance copper foil surface has a great relationship with the wrinkles generated when it is bonded to the resin.

That is, the rolled copper foil of the present invention contains a copper foil having a mass ratio of 99.90% or more and a thickness of 3 to 8 μm, which is characterized by 50 mm in the TD direction in accordance with JIS-B0601 (2013). When the profile curve of the surface of the length is cut off by the contour curve filter λ c=2 mm and the contour curve filter λ f=25 mm to obtain the ripple curve, the average length Wsm of the ripple curve element is 2.5~20.0mm.

Preferably, the maximum height ripple Wz of the ripple curve is 0.00010 to 0.00200 mm.

The copper foil of the present invention is preferably a rolled copper foil containing a total of one or more additive elements selected from the group consisting of Ag, Zn, Sn, and P in an amount of 10 to 2000 ppm by mass.

Preferably, a plating layer composed of one or more elements selected from the group consisting of Cu, Ni, Zn, and Co is formed on one surface or both surfaces.

Preferably, when the long-wavelength component is cut off from the profile curve by λ c=0.25 mm to obtain a roughness curve, the arithmetic mean roughness Ra calculated from the roughness curve is 0.01 to 0.1 μm; the maximum height roughness is obtained. Rz is 0.1 to 0.8 μm.

The copper clad laminate of the present invention comprises the above copper foil and a resin layer.

In the flexible printed circuit board of the present invention, the copper-clad laminate is used for the copper The foil is formed into a circuit.

The electronic device of the present invention is obtained by using the above-described flexible printed circuit board.

According to the present invention, it is possible to obtain a copper foil which is less likely to wrinkle when laminated with a resin layer even if its thickness is thin.

2‧‧‧The surface of copper foil

L‧‧‧ Length of 50mm along the TD direction

S‧‧‧ section curve

Fig. 1 is a view showing the configuration of a double belt pressing device 100.

Fig. 2 is a view showing a method of measuring a profile curve in the TD direction of the surface of the copper foil.

Hereinafter, the rolled copper foil according to the embodiment of the present invention will be described. In the present invention, the term "%" means mass% unless otherwise specified. The rolled copper foil according to the embodiment of the present invention is useful for a copper clad laminate produced by laminating a resin layer such as a resin film, and can be applied to the above-described casting method or double belt method.

<composition>

The rolled copper foil contains copper in a mass ratio of 99.90% or more. Examples of such a composition include refined copper standardized by JIS-H3100 (C1100) or oxygen-free copper standardized by JIS-H3100 (C1020). The rolled copper foil preferably contains copper in a mass ratio of 99.90 to 99.999%, and contains oxygen in a range of 0 to 500 ppm by mass.

Moreover, the above-mentioned refined copper or oxygen-free copper may also contain 10 to 2000 masses in total. One or more additive elements selected from the group consisting of Ag, Zn, Sn, and P in an amount of ppm. By adding these additional elements, the ratio of the {100} orientation in which the bending property or the bendability is improved is increased.

When the total amount of the above elements is less than 10 ppm by mass, the bendability of the copper foil may be lowered. When the total amount of the above elements exceeds 2000 ppm by mass, the decrease in electrical conductivity may be remarkable.

In particular, if these additive elements are contained in an amount of 10 to 500 ppm by mass, the bending property or the bendability can be further improved. Further, when these additive elements are contained in an amount of 500 to 2,000 ppm by mass, they become hard, and wrinkles are less likely to occur in the production of CCL.

<thickness>

The thickness of the copper foil was set to 3 to 8 μm. Copper foil having a thickness of less than 3 μm is difficult to manufacture. Further, since the thickness of the copper foil exceeds 8 μm, it is less likely to cause wrinkles which are a problem in the present invention, and therefore it is outside the target.

<plating layer>

A plating layer made of one or more elements selected from the group consisting of Cu, Ni, Zn, and Co may be formed on one surface or both surfaces of the copper foil.

When such a plating layer is laminated with a resin to produce CCL, the adhesion to the resin is improved, and it is usually a roughened plating layer.

<surface properties of copper foil>

According to JIS-B0601 (2013), the profile curve of the surface from the length of 50 mm in the TD direction is a short-wavelength and long-wavelength component under the condition of a contour curve filter λ c = 2 mm and a profile curve filter λ f = 25 mm. When the ripple curve is obtained by the cutoff, the average length Wsm of the ripple curve element is 2.5 to 20.0 mm.

Here, the TD (Transverse Direction) direction is a direction at right angles to the MD direction (machine direction). In the case of rolling a copper foil, the TD direction is rolled in a right angle direction.

Further, as shown in Fig. 2, a profile curve S indicating a height profile was measured along the length L of the surface of the copper foil 2 which was 50 mm in the TD direction. Further, in the case where the plating layer is formed on one surface of the copper foil, the profile curve S of the surface of the copper foil which is not plated is measured. In the case where the plating layer is formed on both surfaces of the copper foil, first, the arithmetic mean roughness Ra is measured on the surfaces of the two plating layers by the following method, and the profile S of the surface having a small Ra is measured.

The profile curve is based on the "primary profile" described in "3.1.5" of JIS-B0601-2013.

Then, the "corrugation curve" is obtained in the following manner. First, the self-section curve is removed by a low-pass filter to remove the wavelength profile curve filter λ c: 2 mm (where λ c is defined in JIS-B0601-2013 "3.1.1.2" "Defining the roughness component and the ripple component. The filter of the boundary") is the composition of the short surface roughness. Further, since the curve is removed by the high-pass filter from the contour curve filter λ f: 25 mm (where λ f is defined in JIS-B0601-2013 "3.1.1.3", "Defining the ripple component and the longer wavelength The filter of the boundary of the component") has a long surface roughness component and a ripple curve is obtained.

The average length Wsm of the corrugated curve elements is based on "mean width of the profile elements" described in JIS-B0601-2013 "4.3.1".

The maximum height ripple Wz of the corrugated curve element is the "maximum height of profile" described in JIS-B0601-2013 "4.1.3".

The roughness curve is the "roughness profile" described in JIS-B0601-2013 "3.1.6".

The arithmetic mean roughness Ra is based on the "arithmetical mean deviation of the assessed profile" described in JIS-B0601-2013 "3.1.6".

The maximum height roughness Rz is the "maximum height of profile" described in JIS-B0601-2013 "4.1.3".

By obtaining the profile curve S from the surface of the length L of 50 mm in the TD direction, the shape of the copper foil which is the cause of the wrinkles can be detected.

The reason why the contour curve filter λ c = 2 mm is set is that surface irregularities having a wavelength of less than 2 mm are not associated with wrinkles. Further, the reason why the contour curve filter λ f = 25 mm is that the surface unevenness such as a wavelength exceeding 25 mm can be regarded as a measurement unevenness which is not caused by the surface shape of the copper foil. Further, surface irregularities such as wavelengths exceeding 25 mm are not associated with wrinkles.

Further, by managing the average length Wsm of the corrugated curve elements to 2.5 to 20.0 mm, it becomes less likely to wrinkle the copper foil when it is bonded to the resin, thereby improving productivity or yield.

When the CCL is produced using a thin copper foil, the laminated copper foil is sandwiched between a pair of heating rolls, and the double-belt pressed copper foil 2 is sandwiched between the respective belts 102a and 102b (see FIG. 1). Hot crimping. At this time, if the copper foil has a moderate corrugation, a gap will occur between the heating roller or each of the belts 102a, 102b and the copper foil, and this gap becomes a passage of air. Therefore, it is considered that when the force of wrinkles in the copper foil acts during thermocompression bonding, the copper foil moves from the gap and disperses the force, so that it is difficult to become wrinkles.

Thus, if it is a copper foil having a corrugation of a moderate length, wrinkles are suppressed, but it is recognized. Whether the period of the corrugation is small or large, no wrinkle suppression effect is produced.

That is, the Wsm does not have a small corrugation such as 2.5 mm, and the wrinkle suppressing effect is small, and the Wsm is more likely to cause wrinkles when it exceeds 20.0 mm.

Preferably, the maximum height ripple Wz of the ripple curve is 0.00010 to 0.00200 mm.

It is considered that if Wz is a moderate height within the range, a gap may occur between the heating roller or each of the belts 102a and 102b and the copper foil for the same reason as described above, and wrinkles may occur in the copper foil during thermocompression bonding. When the force acts, the copper foil moves from this gap to disperse the force, making it difficult to become wrinkles.

As described above, in the case of a copper foil having a corrugation of a moderate height, wrinkles are suppressed, but it is considered that the height of the corrugations is not small or large, and wrinkles are not suppressed.

That is, Wz does not have a small corrugation such as 0.00010 mm, and the wrinkle suppressing effect is small, and when Wz exceeds 0.00200 mm, wrinkles are likely to occur.

Preferably, when the long-wavelength component is cut off from the above-mentioned cross-sectional curve S by λ c=0.25 mm to obtain a roughness curve, the arithmetic mean roughness Ra calculated from the roughness curve is 0.01 to 0.1 μm, and the maximum height roughness Rz It is 0.1~0.8μm.

When Ra or Rz does not reach the above range, the surface of the copper foil may be too smooth and the adhesion to the resin layer may be lowered. When Ra or Rz exceeds the above range, Ra or Rz exceeds 10% with respect to the thickness of the copper foil (3 to 8 μm), so that the thickness of the copper foil is lowered, and it is not suitable for CCL or FPC use. Happening.

Further, since Ra and Rz are also calculated based on the above-described cross-sectional curve S, Ra and Rz are values along the TD direction.

The rolled copper foil of the present invention can usually be repeatedly subjected to hot rolling and surface grinding. The second (usually about 2 times) cold rolling and annealing, followed by the final recrystallization annealing, and then the final cold rolling to produce the desired foil thickness. Further, after the copper foil is degreased, in order to ensure adhesion to the resin layer, rough plating is performed on one side (the layer of the resin layer), and further rustproof treatment is performed to coat the copper layer. board.

Furthermore, the higher the degree of processing in the final cold rolling step, the lighter the relaxation annealing, but the more easily the recrystallized grains become larger. From this point of view, the degree of processing of the final cold rolling step is usually 95% or more and 99.9% or less, preferably 96% or more and 99% or less.

Further, it may be an electrolytic copper foil.

The copper clad laminate of the present invention is formed of a copper foil having the above characteristics on both sides of a resin layer or a single-layer layer. The resin layer is not particularly limited as long as it has characteristics applicable to a printed wiring board or the like, and for example, a polyester film or a polyimide film, a liquid crystal polymer (LCP) film, or Teflon (registered trademark) can be used. A film, a polyethylene terephthalate film, a polyethylene naphthalate film, or the like is used for FPC use.

The resin layer itself may also be a plurality of layers. Further, a paper substrate phenol resin, a paper substrate epoxy resin, a synthetic fiber cloth substrate epoxy resin, a glass cloth-paper composite substrate epoxy resin, a glass cloth-glass non-woven composite substrate epoxy resin, and a glass can be used. Cloth substrate epoxy resin, etc., used for rigid PWB applications.

When a method of laminating a copper foil and a resin is used for a rigid PWB application, a method of preparing a prepreg in which a resin is impregnated into a substrate such as a glass cloth and hardening the resin to a semi-hardened state is prepared, and the copper foil is overlapped. In the prepreg and heat and pressure. In the case of FPC, a copper clad laminate can be produced by laminating a copper foil via an adhesive followed by a resin layer such as a polyimide film or by laminating a copper foil under high temperature and high pressure without using an adhesive.

For example, as a condition for lamination processing, as disclosed in Japanese Patent Laid-Open No. 2011-148192 As described above, it can be produced by a method in which a polyimide film having a thermoplastic polyimide having an adhesive force applied in advance is superposed on a copper foil, and is pressed by a heating roll or the like. A method called a lamination method, or a method in which a liquid resin is applied to a copper foil and dried on a copper foil is called a casting method. The flexible copper clad laminate obtained by such a method is called a double-layer flexible copper clad laminate. Further, a three-layer flexible copper clad laminate obtained by bonding a copper foil and a polyimide film to an adhesive such as an epoxy resin may be used.

The thickness of the resin (layer) is not particularly limited, and generally about 9 to 50 μm is used. Further, a thicker 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, but is, for example, 150 μm.

The copper clad laminate of the present invention can be used for various flexible printed substrates (printed wiring boards (PWB)). The printed wiring board is not particularly limited. For example, from the viewpoint of the number of layers of the conductor pattern, it can be applied to a single-sided PWB, a double-sided PWB, or a multilayer PWB (three or more layers); and from the viewpoint of the type of the insulating substrate material. In other words, it can be applied to rigid PWB, flexible PWB (FPC), and rigid-flexible PWB.

[Example 1]

<Manufacture of rolled copper foil>

An ingot having a thickness of 100 mm was cast as a raw material by using copper or oxygen-free copper to which an element having the composition shown in Table 1 was added, and hot rolling was performed at 800 ° C or higher to a thickness of 10 mm, and the surface scale was surface-polished. Then, cold rolling and annealing were repeatedly performed to obtain a rolled plate ring having a thickness of 0.5 mm.

Then, cold rolling was carried out to a thickness of 20 μm, and rolling was performed by a calender roll having a Wsm of a ceramic sintered body and having a Wsm of an axial surface of 2.5 to 20 mm. The Ra of the surface of the rolling roll in the above direction was set to 0.04 to 0.1 μm.

Further, Comparative Examples 1 and 3 were subjected to cold rolling to a thickness of 20 μm, and a super-hard roll was used for the calender roll, and finally processed into a final thickness. The Ra of the super-hard roll of Comparative Example 3 was set to 0.03 μm.

In Comparative Example 2, a calender roll having a Wsm of a surface of the ceramic sintered body and having a Wsm of more than 20 mm in the above-described direction was used for the cold rolling after the thickness of 20 μm. The Ra in the above direction of the calender roll was set to 0.04 to 0.1 μm.

In addition, "OFC-100 ppmAg" in the column of the composition of Table 1 means that 100 mass ppm of Ag is added to the oxygen-free copper OFC of JIS-H3100 (C1020). In addition, "TPC-200 ppm Ag" means that 200 mass ppm of Ag is added to refined copper (TPC) of JIS-H3100 (C1100). The same is true for other additions.

<surface properties of copper foil>

For the obtained copper foil (unplated) surface, as shown in Fig. 2, a profile curve was measured using a three-dimensional shape measuring machine (manufactured by Ens, product name: single trigger 3D shape measuring machine VR-3200) S. Then, Wsm and Wz are obtained by the software built in the measuring machine.

The profile curve S, the ripple curve, and the roughness curve were obtained in the above manner in accordance with JIS-B0601 (2013). Wsm and Wz are also obtained in the above manner in accordance with JIS-B0601 (2013).

Ra and Rz were measured using a contact surface roughness meter (manufactured by Otaru Research Institute, product name: SE-3400). Ra and Rz were calculated in the above manner in accordance with JIS-B0601 (2013).

<thickness of copper foil>

It is measured by the gravimetric method using IPC-TM-650 as a guideline.

<Whether or not wrinkles are formed when laminating>

Using a hot roll laminator, the copper foil was superposed on both sides of the polyimide film and transported to 1 pair. The heating rolls were thermocompression bonded and laminated to form a double-sided double-sided copper clad laminate. The heating temperature of the rolls was set to 350 ° C, and the pressure of the rolls and the conveying speeds and tension values of the copper foil and the polyimide film were set to be the same.

The front and back copper foils in the double-sided double-sided copper clad laminate after thermocompression bonding were visually observed for wrinkles, and were evaluated on the following basis. When the evaluation is ◎ or ○, it is possible to effectively suppress wrinkles during lamination.

◎: no wrinkles were formed on the copper foil on either the front side or the back side

○: According to the light irradiation method, a shallow wrinkle that can be visually confirmed is produced on either the front side or the back side.

×: Regardless of the method of irradiating light, at least one of the front side and the back side is made to have a wrinkle that can be visually confirmed

<bending>

First, the following roughening treatment is performed on one side of the copper foil (International Patent Publication 2013108414).

Roughening plating: ternary copper-cobalt-nickel alloy plating

Composition of plating bath: Cu10~20g/L, Co1~10g/L, Ni1~10g/L

Plating bath pH: 1~4

Plating temperature: 40~50°C

Plating current density: 20~30A/dm ²

Plating electrolysis time: 1~5 seconds

Then, the roughened surface of the copper foil was superposed on both sides of a commercially available polyimide film of 12.5 μm (UPILEX-VT manufactured by Ube Industries, Ltd.), and then laminated. A double-sided CCL is produced by thermocompression bonding. In this CCL, after all the copper foils of one side were removed by etching, a circuit pattern having a circuit width of 0.3 mm and a space width of 0.3 mm was formed by etching on the copper foil on the opposite side. Then, a cover film having a thickness of 25 μm was coated on the circuit to be processed into an FPC.

For this FPC, a sliding bending test was performed to evaluate the bendability. Specifically, the sliding radius r (mm) was set to r = 4 mm in Example 9 using a slide tester (TK-107 model manufactured by Applied Technology Co., Ltd.), and r was set in other examples and comparative examples. = 0.72 mm, in either case, the FPC was bent at a sliding speed of 120 times/min.

The evaluation was based on the following criteria. When the evaluation is ◎ or ○, the flexibility is excellent.

◎: Compared with before the test, the bending resistance of the circuit of the copper foil increased by 5% when the number of bending times was 100,000 times or more.

○: The number of bends when the resistance of the circuit of the copper foil is increased by 10% is 100,000 times or more as compared with that before the test.

×: The number of bends when the resistance of the circuit of the copper foil is increased by 10% is less than 100,000 times compared with before the test.

<Adhesiveness>

A double-sided CCL was produced in the same manner as the method for evaluating the above bendability. For this CCL, after all the copper foils of one side were removed by etching, the following circuit pattern was formed on the copper foil of the opposite side. Then, the adhesion was evaluated according to the method A of "peeling strength of copper foil" prescribed in JIS-C6471 (1995). Further, the size of the double-sided CCL and the circuit pattern formed on the copper foil are in accordance with Fig. 4 of JIS-C6471 (1995).

The evaluation was based on the following criteria. When the evaluation is ○, the flexibility is excellent.

○: 0.7kN/m or more

×: not up to 0.7kN/m

The results obtained are shown in Table 1.

As can be seen from Table 1, in the case of each of the examples in which Wsm is 2.5 to 20.0 mm, wrinkles of the copper foil in the lamination process during the production of CCL can be suppressed even when the thickness is thin. Moreover, CCL is also excellent in flexibility and adhesion.

In particular, in the case of Examples 1 to 16 in which Wz was 0.00010 to 0.00200 mm, it was possible to further effectively suppress wrinkles of the copper foil in the lamination process as compared with the other examples.

On the other hand, in the case of Comparative Examples 1 and 3 in which Wsm was less than 2.5 mm and Comparative Example 2 in which Wsm exceeded 20.0 mm, wrinkles were remarkably generated in the copper foil in the lamination process at the time of CCL production.

Further, in the case of Comparative Example 3, Ra and Rz did not reach the predetermined range, and the surface of the copper foil was too flat, and the adhesion was also lowered.

2‧‧‧The surface of copper foil

L‧‧‧ Length of 50mm along the TD direction

S‧‧‧ section curve

TD‧‧ transverse

MD‧‧‧ portrait

Claims (10)

A copper foil comprising a copper foil having a mass ratio of 99.90% or more and a thickness of 3 to 8 μm, which is characterized by a surface having a length of 50 mm from the TD direction in accordance with JIS-B0601 (2013). When the profile curve is λ c=2 mm and the profile curve filter λ f=25 mm, the short-wavelength and long-wavelength components are cut off to obtain a ripple curve. The average length Wsm of the ripple curve element is 2.5 to 20.0 mm. . The copper foil of claim 1, wherein the maximum height ripple Wz of the corrugation curve is 0.00010 to 0.00200 mm. The copper foil of the first aspect of the invention is a rolled copper foil containing a total of one or more additive elements selected from the group consisting of Ag, Zn, Sn, and P in an amount of 10 to 2000 ppm by mass. The copper foil of the second aspect of the invention is a rolled copper foil, which contains a total of one or more additive elements selected from the group consisting of Ag, Zn, Sn, and P in an amount of 10 to 2000 ppm by mass. The copper foil according to any one of claims 1 to 4, wherein a plating layer composed of one or more elements selected from the group consisting of Cu, Ni, Zn, and Co is formed on one or both sides. . The copper foil according to any one of claims 1 to 4, wherein, when the long-wavelength component is cut off from the profile curve by λ c = 0.25 mm, a roughness curve is obtained, and the roughness curve is calculated. The arithmetic mean roughness Ra is 0.01 to 0.1 μm, and the maximum height roughness Rz is 0.1 to 0.8 μm. The copper foil according to claim 5, wherein the arithmetic mean roughness Ra calculated from the roughness curve is obtained by cutting off the long wavelength component from the profile curve by λ c = 0.25 mm 0.01~0.1μm; the maximum height roughness Rz is 0.1~0.8μm. A copper clad laminate obtained by laminating a copper foil and a resin layer according to any one of claims 1 to 7. A flexible printed circuit board formed by forming a circuit using the copper clad laminate of claim 8 in the copper foil. An electronic machine using the flexible printed circuit board of claim 9 of the patent application.