JP2013227668A - Surface roughening-treated copper foil, method for producing the same and circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide surface roughening-treated copper foil for a circuited board, particularly, for a flexible printed wiring board whose adhesive properties on adhesion with an insulating film is excellent, and also, having excellent flexibility after adhesion at high temperature with an insulating film, and a circuit board such as a flexible printed wiring board (FPC) having excellent flexibility.SOLUTION: Surface roughening-treated copper foil is obtained by applying a surface roughening treatment layer to at least one side of untreated copper foil, and, in which the endurable number of cycles on bent tests by IPC bent tests after heating at 300°C for 1 hr (IPC standards TM-650) is ≥11,000 times, the average crystal grain size in the cross-section is ≥0.5 μm, and a surface area ratio (the surface after the roughening treatment/the surface before the roughening treatment) is 1.1 to 5.0. The 0.2% proof stress of the surface roughening-treated copper foil after heating at 300°C for 1 hr is ≤160 N/mm.

Description

  The present invention relates to a surface-roughened copper foil having excellent bending resistance, flexibility, and heat resistance. Particularly, the present invention relates to a circuit board excellent in heat resistance and flexibility, such as a flexible printed wiring board (hereinafter abbreviated as FPC). It relates to a surface roughened copper foil suitable for use.

Recent FPCs are usually divided into two types. One is a pattern in which a copper foil is attached to an insulating film (polyimide, polyester, etc.) with an adhesive resin and etched to give a pattern. This type of FPC is usually called a three-layer FPC. On the other hand, another type is an FPC in which an insulating film (polyimide, liquid crystal polymer, etc.) and a copper foil are directly laminated without using an adhesive. This is usually called a two-layer FPC.
The main applications of FPC are for flat panel displays such as liquid crystal displays and plasma displays, or for internal wiring of cameras, AV equipment, personal computers, computer terminal equipment, HDDs, mobile phones, car electronics equipment, and the like. Since these wirings are used in places where they are bent and attached to equipment or repeatedly bent, one of the important characteristics of FPC copper foil is that it is excellent in flexibility.

There are roughly two types of copper foil for FPC. One is a rolled copper foil obtained by rolling a copper ingot produced by casting into a foil shape. Another is electrolytic copper foil.
These untreated copper foils are surface treated.

Since the copper foil for FPC is required to be flexible as described above, conventionally, the use ratio of the rolled copper foil has been high. This is because the rolled copper foil is characterized in that it is annealed at a relatively low temperature of 120 to 160 ° C. that is heated in the bonding process of the copper foil and the polyimide during FPC production, softens, and has high flexibility and elongation.
However, the rolled copper foil is more expensive than the electrolytic copper foil, and in particular, the cost increases dramatically as the thickness becomes 12 μm or 9 μm. This is because when making a thin object, a thick copper foil is repeatedly rolled over and over. Moreover, the width of the copper foil manufactured by rolling is as narrow as about 600 mm normally, and there exists a fault that productivity at the time of FPC manufacture is bad.

On the other hand, the electrolytic copper foil is cheaper than the rolled copper foil, and it is possible to produce a copper foil having a width of 1,000 mm or more, which has an advantage of excellent productivity at the time of FPC production. The electrolytic copper foil produced by the conventional production method is not annealed or softened even when heated to 200 ° C. or higher as compared with the rolled copper foil, has poor flexibility, and has limited use as a copper foil for FPC. It was.
Development of a copper foil excellent in bendability has been made to eliminate such drawbacks of the electrolytic copper foil (see Patent Document 1), and the bendability of the electrolytic copper foil has been raised to a level equivalent to that of the rolled copper foil.

  On the other hand, there are remarkable technological innovations in electronic devices in recent years, and while devices are becoming more compact, FPCs used in these devices are also rapidly increasing in number of pins and in fine pitches. In order to satisfy such a demand and improve the reliability, a copper foil having a longer bending life has been required.

  As described above, a circuit is formed on a copper clad laminate (hereinafter abbreviated as CCL) in which copper foil is pasted on the characteristics required for FPC or on an insulating film (polyimide, polyester, liquid crystal polymer, etc.) The characteristic required for the printed wiring board to be is a surface-roughened copper foil excellent in bending resistance, flexibility and heat resistance.

Both the rolled copper foil and the electrolytic copper foil used for FPC are subjected to a roughening treatment in which copper particles are adhered to at least the surface of the copper foil that adheres to the film in order to increase the adhesive strength with the insulating film. The surface is subjected to galvanization and chromate treatment to prevent rust and heat discoloration.
In the case of electrolytic copper foil, the M surface is usually roughened, and the S surface is not normally roughened, but is galvanized or chromated to prevent rust or heat discoloration. ing.

At the time of CCL production, an insulating film is laminated on the roughened surface by thermo-compression (three-layer FPC) or directly on the roughened surface without using an adhesive resin. Create a CCL by double-layer FPC).
A circuit is formed on the prepared CCL by an etching method, and an insulating film cover lay is adhered to the circuit side to form an FPC.

  The FPC produced in this way is used by being bent and mounted or repeatedly bent. Therefore, the copper foil for FPC needs to be excellent in flexibility.

  In addition, as an evaluation test method for bendability, there are a bend resistance test described in JIS C 5016-1994, a bend resistance test described in IPC standard TM-650, and the like. Among them, the bending resistance test described in the IPC standard TM-650 is said to be a test method close to an actual bending mode in which FPC is used, and is generally used. The bendability test of the surface roughened copper foil in this specification is measured by the test method described in this IPC standard TM-650.

When the bending test of the FPC is performed by the bending resistance test as described above, a crack enters the copper foil surface as the number of bending increases, and the copper foil eventually breaks starting from the crack.
When the process of cracks is observed in detail, cracks first enter from the grain boundaries of the roughening treatment as shown in the schematic diagram of FIG. 2, and the cracks progress inside the copper foil by repeating the bending, as shown in FIG. This leads to the breaking of the foil.

  When this phenomenon was analyzed, the roughened particles applied in the roughening treatment were dense on the surface of the foil as fine crystals, and the toughness was low. As a result, a crack was generated (see FIG. 2), and it was obtained that the fracture started from the crack as the starting point as bending was repeated.

JP 2010-236058 A JP-A-6-237078

Based on the above view, the present invention has been intensively studied for the purpose of further increasing the bending life of the conventional electrolytic copper foil, and the present invention has been completed.
An object of this invention is to provide the copper foil for flexible printed wiring boards which is excellent in the adhesiveness which adhere | attaches with an insulating film, and is excellent in the bending resistance after adhesion | attachment with an insulating film.
Another object of the present invention is to provide a circuit board, particularly a copper foil for a flexible printed wiring board, and a method for producing the same, which are excellent in adhesiveness to be bonded to an insulating film and excellent in bending resistance after bonding to the insulating film. To do.

  The surface-roughened copper foil of the present invention is a copper foil in which a surface-roughened layer is applied to at least one surface of an untreated copper foil, and the IPC bending test (IPC) after heating the copper foil at 300 ° C. for 1 hour. According to standard TM-650), the number of bending resistances is 11000 times or more, the average crystal grain size of the cross section is 0.5 μm or more, and the surface area ratio (surface area after roughening treatment / surface area before roughening treatment) is 1.1 to 5.0.

The surface-roughened copper foil of the present invention preferably has a 0.2% proof stress of 160 N / mm ² or less after heating at 300 ° C. for 1 hour.

  On the surface roughening layer, a surface protective layer containing at least one of Ni, Zn, Cr, Co, Mo, P alone, an alloy thereof, or a hydrate thereof is formed. Preferably it is.

The surface roughened copper foil of the present invention has a method of producing a surface roughened copper foil having a number of bending resistances of 11,000 times or more according to an IPC bending test (IPC standard TM-650) after heating at 300 ° C. for 1 hour, and an average crystal grain size of the cross section. A method for producing a surface-roughened copper foil having a surface area ratio (surface area after roughening / surface area before roughening) of 1.1 to 5.0 at 0.5 μm or more, which is an untreated copper foil at least one side of, thiourea-based additive is a surface roughening treatment with 0.001mmol / L~0.1mmol / L the added electrolyte, manufacturing method of a copper foil having at least one side surface roughened layer of It is.

  The circuit board of the present invention is a circuit board obtained by attaching a film to the surface roughened copper foil of the present invention.

The surface-treated copper foil of the present invention is excellent in adhesiveness for adhering to an insulating film, and has a surface roughening treatment for a circuit board, particularly for a flexible printed wiring board, which has excellent bending resistance after adhesion to an insulating film at a high temperature. Copper foil can be provided.
Moreover, this invention can provide the manufacturing method of the copper foil for flexible printed wiring boards which is excellent in the adhesiveness which adhere | attaches with an insulating film, and is excellent in the bending resistance after adhesion | attachment with an insulating film at high temperature.
Furthermore, this invention can provide circuit boards, such as a flexible printed wiring board (FPC) excellent in bending resistance.

FIG. 1 is a schematic view for explaining the surface-treated copper foil of the present invention. FIG. 2 is a schematic view showing a starting point where a crack is generated in the surface-treated copper foil. FIG. 3 is a schematic view showing a fractured state of the surface-treated copper foil. It is a schematic diagram explaining the measuring method of the average space | interval of a roughening particle | grain, and an average particle diameter.

The present invention provides a surface treatment comprising a granular or columnar crystal structure on at least one surface of an electrolytic copper foil and a rolled copper foil (hereinafter sometimes referred to as an untreated copper foil or simply a copper foil) that have not been subjected to a surface treatment. A copper foil for a circuit board (for example, a flexible printed wiring board) provided with a layer.
In the present invention, the untreated electrolytic copper foil may be either an electrolytic copper foil or a rolled copper foil, and any copper foil can be used as long as the crystal grains are coarsened by the recrystallization treatment after the foil formation.

FIG. 1 is a schematic diagram for explaining the crystal structure of a surface-treated copper foil, and FIG. 1 (a) shows a state in which roughened particles 2 are adhered by subjecting the untreated copper foil 1 to a surface treatment. . When the roughened surface-treated copper foil is recrystallized, the roughened surface-treated copper foil is roughened by a normal roughening method as shown in FIG. Chemical particles 2 do not recrystallize.
As shown in FIG. 1 (c), the surface-treated copper foil of the present invention is recrystallized after the roughening treatment, so that the roughened particles are recrystallized together with the copper foil, and the crystal structure is coarsened. Surface roughening particles are integrated.
Thus, the copper foil body and the surface roughening particles are integrated to coarsen the crystal structure. Therefore, even if the copper foil is repeatedly bent and stress is concentrated on the concave portion of the rough surface, the crystal structure is coarsened and the toughness is improved, cracks are hardly generated, and the bending resistance is excellent. It is assumed that the surface-treated copper foil is excellent in adhesiveness with the insulating substrate.

Copper foil that has been surface-treated by the usual roughening treatment method does not recrystallize or is difficult to recrystallize, so even if the crystal structure of the copper foil body is recrystallized and coarsened, the roughened particles on the surface become coarse No (see Figure 1 b). Therefore, even if recrystallization treatment is applied to such a surface-treated copper foil, it cannot be expected to improve the bending resistance. The surface-roughened particles are recrystallized together with the copper foil body by the recrystallization treatment, and the crystal structure is coarsened, whereby an electrolytic copper foil having good bending resistance can be obtained for the first time.
In addition, the normal roughening processing method said here is the method performed by burnt plating processing in the bath which has copper sulfate as a main component and added the inorganic additive. Typical examples of inorganic additives include metal ions of Fe, W, Mo, Co, Ni, and Cr.

In order to apply particles whose crystal structure is coarsened by recrystallization treatment, it is possible to perform surface treatment with a copper sulfate electrolytic solution to which a thiourea additive is added. By recrystallizing the surface-treated copper foil in this way, the crystal structure of the surface-treated particles becomes coarse, and becomes a coarse crystal structure together with the copper foil body.
In addition, the said roughening method is an example and in this invention, it is not limited to the copper foil surface-roughened by the said roughening method.

Depending on the plating treatment in which the copper foil is subjected to a surface treatment, the copper crystal structure formed may become a columnar crystal structure depending on the composition of the plating solution. However, as plating applied to the untreated electrolytic copper foil, columnar structure plating is not suitable when bending resistance is required. The reason is that, when a bending stress is applied to the copper foil, in the case of a columnar crystal structure, a crack is generated along the columnar crystal grain boundary and the probability of fracture is high.
However, columnar roughened particles having a crystal structure may sometimes be formed into a granular crystal structure by recrystallizing the roughened particles. In such a case, the columnar crystal structure can be first roughened and then recrystallized to form a granular crystal structure. Therefore, a surface treatment for forming a columnar crystal structure is also effective.

The copper foil of the present invention preferably has a surface roughness Rz (surface roughness) of at least one surface of the surface-treated copper foil of 0.5 to 5.0 μm and a surface area ratio (after roughening treatment). Surface area / surface area before roughening treatment) of 1.1 to 5.0.
The surface roughness Rz of the surface-treated copper foil is set to 0.5 to 5.0 μm because, when Rz is 0.5 μm or less, a sufficient anchoring effect cannot be obtained with the insulating film attached to the copper foil surface. This is because the adhesiveness is poor, and when Rz is 5.0 μm or more, root residue tends to occur during etching when forming the wiring, and the etching factor decreases, which is not preferable.
In addition, the surface-treated copper foil has a surface area ratio of 1.1 to 5.0 times because, when the surface area ratio is 1.1 times or less, a sufficient anchoring effect cannot be obtained with the insulating film, and adhesion This is because if the surface is 5.0 times or more, the roughness of the rough surface is large and cracks may be generated from the rough surface.

  The recrystallization treatment in the present invention can be performed by a general recrystallization treatment method, for example, a heat treatment method for an arbitrary time. Moreover, the heat history at the time of manufacturing FPC can also be used as the recrystallization process. For example, as a heat history for laminating with a polyimide film, a typical 300 ° C., 1 hour can be selected and recrystallized. Is possible.

The copper foil of the present invention preferably has a 0.2% proof stress of 160 N / mm ² or less after heating at 300 ° C. for 1 hour. 0.2
This is because when the% proof stress is 160 / mm ² or more, the toughness is poor and the flexibility is lowered. The lower limit is about 100 N / mm ² .

In the surface treatment method of the present invention, electrolytic treatment is performed with a copper sulfate electrolyte containing a thiourea compound.
The addition amount of the thiourea compound is 0.1 mmol / L or less, preferably 0.001 to 0.1 mmol / L. When the addition amount is more than 0.1 mmol / L, the crystal structure of the roughened particles is not coarsened and softening characteristics are not exhibited, which is not preferable. When the addition amount is less than 0.001 mmol / L, the effect as an additive is not exhibited, and the roughened particles are not electrodeposited uniformly.

The surface roughened layer thus formed is recrystallized at 250 to 350 ° C. Therefore, by recrystallizing at 250 to 350 ° C., the crystal structure of the copper foil body and the surface roughened layer can be integrated. It is also possible to recrystallize by heating (for example, 300 ° C. × 1 hour) at the time of manufacturing a copper-clad laminate (both two-layer structure and three-layer structure) having a high lamination temperature as in the case of lamination with a polyimide substrate. .
As described above, the copper foil whose crystal structure has been coarsened by recrystallization hardly cracks the copper foil even when bending stress is applied to the FPC, and the number of times of bending leading to bending fracture of the copper foil increases. Compared to the roughened copper foil prepared by the conventional method, the roughened copper foil prepared by the method of the present invention increases the number of bendings after heating (300 ° C., 1 hour) by at least 10% as described later. To do.

  In the present invention, the number of times of bending resistance by the IPC bending test (IPC standard TM-650) after heating the surface-roughened layer of the copper foil at 300 ° C. for 1 hour is 11,000 times or more. The bending resistance is 11,000 times or more, which is excellent in bending resistance. The surface of the copper foil is recrystallized, the crystal structure becomes coarse, and even when bending stress is applied to the copper foil, it is difficult to crack and the copper foil is bent. This is because the number of times of bending leading to breakage increases. In the crystal structure that does not recrystallize even when heat-treated, cracks enter from the grain boundaries on the surface as shown in FIGS. 2 and 3. For example, surface-treated copper that has been roughened with a roughening solution containing an inorganic additive. The foil cannot provide bending resistance of 11,000 times or more.

From the viewpoint of material mechanics, the present invention pays attention to the fact that when the copper foil is repeatedly bent, the largest stress is applied to the outermost layer of the copper foil, and cracks are first generated from the grain boundary of the outermost layer. In order to suppress this, a grain boundary recrystallized by heating was formed in the outermost layer. When the crystal grains are coarsened after heating (average particle diameter of 0.5 μm or more), the toughness is improved and a surface-treated copper foil having excellent bending resistance is obtained.
Thus, by forming the grain boundary recrystallized by heating in the outermost layer, the outermost layer has a crystal grain size of 0.5 μm or more and a surface-treated copper foil having a bending resistance of 11,000 times or more.
As described above, the FPC product using the copper foil of the present embodiment can ensure long-term reliability and a long service life as compared with an FPC product that is required to have increasingly strict flexibility in the future.

By providing a surface protective layer on the surface of the surface roughened copper foil of the present invention, the surface of the roughened layer can be rusted and heat resistance can be increased.
The surface protective layer is preferably provided on the surface roughening treatment layer as well as the surface not subjected to the roughening treatment.
As the surface protective layer, it is preferable to apply a layer containing at least one of Ni, Zn, Cr, Co, Mo, P alone, an alloy thereof, or a hydrate thereof.

Hereinafter, the present invention will be described in more detail with reference to examples.
For the copper foil to be roughened (untreated copper foil), an electrolytic copper foil (thickness = 7 μm, hereinafter referred to as electrolytic copper foil A) conforming to the production method of Japanese Patent Application Laid-Open No. 2008-138847, Electrolytic copper foil (thickness = 7 μm, hereinafter referred to as electrolytic copper foil B) conforming to the production method and commercially available rolled copper foil (thickness = 7 μm, tough pitch copper, azurol foil) were used.

<Examples 1-5>
As the untreated copper foil, electrolytic copper foil A was used, and the surface was roughened under the following conditions.
In the surface roughening treatment, the M surface was plated to a thickness of 2 μm using a plating solution of surface treatment bath composition 1.
Electrolytic bath composition 1:
Cu = 787-2360 mmol / L
H ₂ SO ₄ = 205~2050mmol / L
Cl = 424-1410 mmol / L
Thiourea = 0.001 to 0.1 mmol / L
Electrolysis conditions:
Current density = 20-60 A / dm ²
Bath temperature: 40-60 ° C
Next, the surface-treated copper foil was recrystallized by heating at 300 ° C. for 1 hour.

<Example 6>
The untreated copper foil used electrolytic copper foil A, and was surface-treated under the following conditions.
In the surface treatment, plating was performed on the M surface to a thickness of 2 μm using a plating solution of surface treatment bath composition 2.
Electrolytic bath composition 2:
Cu = 787-2360 mmol / L
H ₂ SO ₄ = 205~2050mmol / L
Cl = 424-1410 mmol / L
Ethylenethiourea = 0.01mmol / L
Electrolysis conditions:
Current density = 20-60 A / dm ²
Bath temperature: 40-60 ° C
Next, the surface-treated copper foil was recrystallized by heating at 300 ° C. for 1 hour.

<Example 7>
The untreated copper foil used electrolytic copper foil A, and was surface-treated under the following conditions.
In the surface treatment, plating was performed on the M surface to a thickness of 2 μm using a plating solution of surface treatment bath composition 3.
Electrolytic bath composition 3:
Cu = 787-2360 mmol / L
H ₂ SO ₄ = 205~2050mmol / L
Cl = 424-1410 mmol / L
Thiosemicarbazide urea = 0.01mmol / L
Electrolysis conditions:
Current density = 20-60 A / dm ²
Bath temperature: 40-60 ° C
Next, the surface-treated copper foil was recrystallized by heating at 300 ° C. for 1 hour.

<Example 8>
The untreated copper foil used electrolytic copper foil B and was surface-treated under the following conditions.
In the surface treatment, plating was performed on the M surface to a thickness of 2 μm using a plating solution of surface treatment bath composition 4.
Electrolytic bath composition 4:
Cu = 787-2360 mmol / L
H ₂ SO ₄ = 205~2050mmol / L
Cl = 424-1410 mmol / L
Thiourea = 0.01mmol / L
Electrolysis conditions:
Current density = 20-60 A / dm ²
Bath temperature: 40-60 ° C
Next, the surface-treated copper foil was recrystallized by heating at 300 ° C. for 1 hour.

<Example 9>
Rolled copper foil was used for untreated copper foil, and surface treatment was performed under the following conditions.
In the surface treatment, plating was performed on the M surface to a thickness of 2 μm using a plating solution of surface treatment bath composition 5.
Electrolytic bath composition 5:
Cu = 787-2360 mmol / L
H ₂ SO ₄ = 205~2050mmol / L
Cl = 424-1410 mmol / L
Thiourea = 0.01mmol / L
Electrolysis conditions:
Current density = 20-60 A / dm ²
Bath temperature: 40-60 ° C

Next, the surface-treated copper foil was recrystallized by heating at 300 ° C. for 1 hour.

<Comparative Example 1>
The same electrolytic copper foil A as in Example 1 was used, and surface treatment was performed under the following conditions.
In the surface treatment, plating was performed on the M surface to a thickness of 2 μm using a plating solution of surface treatment bath composition 6.
Electrolytic bath composition 6:
Cu = 787-2360 mmol / L
H ₂ SO ₄ = 205~2050mmol / L
Cl = 424-1410 mmol / L
Electrolysis conditions:
Current density = 20-60 A / dm ²
Bath temperature: 40-60 ° C
Next, the surface-treated copper foil was recrystallized by heating at 300 ° C. for 1 hour.

<Comparative Examples 2-4>
The untreated copper foil used electrolytic copper foil A, and was surface-treated under the following conditions.
In the surface treatment, plating was performed on the M surface to a thickness of 2 μm using a plating solution of surface treatment bath composition 7.
Electrolytic bath composition 7:
Cu = 787-2360 mmol / L
H ₂ SO ₄ = 205~2050mmol / L
Cl = 424-1410 mmol / L
Inorganic additive (iron sulfate heptahydrate) = 0.001 to 0.1 mmol / L
Electrolysis conditions:
Current density = 20-60 A / dm ²
Bath temperature: 40-60 ° C
Next, the surface-treated copper foil was recrystallized by heating at 300 ° C. for 1 hour.

<Comparative Example 5>
The untreated copper foil used electrolytic copper foil B and was surface-treated under the following conditions.
In the surface treatment, plating was performed on the M surface to a thickness of 2 μm using a plating solution of surface treatment bath composition 8.
Electrolytic bath composition 8:
Cu = 787-2360 mmol / L
H ₂ SO ₄ = 205~2050mmol / L
Cl = 424-1410 mmol / L
Inorganic additive (iron sulfate heptahydrate) = 0.01 mmol / L
Electrolysis conditions:
Current density = 20-60A / dm2
Bath temperature: 40-60 ° C
Next, the surface-treated copper foil was recrystallized by heating at 300 ° C. for 1 hour.

<Comparative Example 6>
Untreated copper foil was rolled copper foil and surface treated under the following conditions.
In the surface treatment, plating was performed on the M surface to a thickness of 2 μm using a plating solution having a surface treatment bath composition 9.
Electrolytic bath composition 9:
Cu = 787-2360 mmol / L
H ₂ SO ₄ = 205~2050mmol / L
Cl = 424-1410 mmol / L
Inorganic additive (iron sulfate heptahydrate) = 0.01 mmol / L
Electrolysis conditions:
Current density = 20-60 A / dm ²
Bath temperature: 40-60 ° C
Next, the surface-treated copper foil was recrystallized by heating at 300 ° C. for 1 hour.

<Measurement of crystal grain size of roughened particles>
The cross section of the copper foil which performed the recrystallization heat processing created in Examples 1-9 and Comparative Examples 1-6 was image | photographed with the scanning electron microscope, and 100 roughening particles were selected at random. The average value of the lengths in the longitudinal direction of the crystal grains contained in the selected roughened particles was calculated. The results are shown in Table 1.

<Creation of flexural resistance test specimen>
The copper foil subjected to the recrystallization heat treatment shown in Examples 1 to 9 and Comparative Examples 1 to 6 was subjected to bending resistance of line / space = 1.5 mm / 1.0 mm described in JIS C 5016-1994. Sex samples were prepared.

<Bend resistance test (IPC flex test)>
The copper foil subjected to the recrystallization heat treatment shown in Examples 1 to 9 and Comparative Examples 1 to 6 was used as a bending resistance evaluation test piece (FPC), and the FPC high-speed bending tester SEK-31B2S manufactured by Shin-Etsu Engineering Co., Ltd. was used. The bending resistance was measured under the conditions specified in IPC standard TM-650 (bending speed 1500 times / min, stroke length 20.0 mm, curvature radius 1, 0 mm). In the measurement, the circuit resistance was measured over time, and the number of times until breakage was counted.
The results are shown in Table 1.

<Measurement of 0.2% yield strength>
The copper foil subjected to the recrystallization heat treatment shown in Examples 1 to 9 and Comparative Examples 1 to 6 was cut into test pieces having a length of 6 inches and a width of 0.5 inches, and measured using a tensile tester. did. The results are shown in Table 1.

<Uniform adhesion of roughened particles>
The copper foil surface shown in Examples 1-9 and Comparative Examples 1-6 was image | photographed with the scanning electron microscope, the average space | interval between roughening particles was computed by the method shown in FIG. Was measured.
A diagonal line is drawn on the photograph taken as shown in FIG.
Next, as shown in FIG. 4B, the diagonal lines were divided at 20 μm intervals, and the number of coarse particles hitting or contacting the lines and the particle diameter thereof were measured.
The average size of the measured roughened particles was calculated.
The total value of the particle diameters of the roughened particles was subtracted from 20 μm, and the value was divided by (number of roughened particles−1) to calculate an average interval.
The average interval between the roughened particles calculated by this method is 0.5 μm or less, and the condition for determining that the roughened particles are electrodeposited without gaps is ○, and the average interval is larger than 0.5 μm. The condition for determining that there was unevenness in the adhesion of particles was determined as x, and the results are also shown in Table 1.

<Method for measuring surface area ratio>
By measuring the surface area of the 50 μm × 50 μm region of the copper foil surface subjected to the roughening treatment shown in Examples 1 to 9 and Comparative Examples 1 to 6 with a laser microscope, and dividing by the apparent area of 2500 μm ^2. Calculated. The results are also shown in Table 1.

<Measurement method of peel strength>
To the copper foils shown in Examples 1 to 9 and Comparative Examples 1 to 6, Nikaflex CISV-2525 (polyimide film 25 μm, adhesive thickness 25 μm) manufactured by Nikkan Kogyo Co., Ltd., 300 ° C., 40 kg / cm ² , Lamination was performed for 1 hour, and an FR4 substrate was attached to the laminated surface. The sample affixed to the base material was inserted into an etching machine, and a 10 mm wide test piece was created. Thereafter, the copper foil was peeled off by 40 mm in the 90-degree direction with a peel tester, and the average peel strength was measured.

As shown in Table 1, Examples 1 to 9, which are embodiments of the present invention, are obtained by recrystallizing the roughened particle crystal and the copper foil main body crystal structure into a unified roughened particle after the roughening treatment. The crystal grain size is increased, and the bending resistance exceeds 11,000 times. Moreover, the 0.2% yield strength after heating at 300 ° C. for 1 hour is also 160 N / mm ² or less, and the roughened particles are uniformly attached. Therefore, the surface roughened copper foil is excellent in adhesion to the insulating film, and can provide a circuit board having excellent bending resistance after adhesion to the insulating film.

On the other hand, Comparative Example 1 was inferior in uniformity of the roughened particles because no additive was added to the roughened electrolytic solution, and a satisfactory result could not be obtained.
In Comparative Examples 2 to 6, iron sulfate heptahydrate was used as an additive, but the recrystallization of the roughened particles was insufficient, and therefore the bending resistance was poor, and a satisfactory copper foil could not be obtained.

  The surface area ratio particularly affects the adhesive strength (peel strength) with polyimide. The surface area ratio and the peel strength were examined by subjecting the untreated copper foil surface to a roughening treatment, heat treatment, and recrystallization of the roughened surface. In the range of 5 to 3.5 (substantially in the range of 1.1 to 5.0), the peel strength tends to increase as the surface area ratio increases. It was confirmed that the peel strength was not affected by the particle size.

1 Copper foil body 2 Roughened particles

Claims (6)

  A copper foil having a surface-roughened layer on at least one surface of an untreated copper foil, and the number of bending resistances measured by an IPC bending test (IPC standard TM-650) after heating the copper foil at 300 ° C. for 1 hour is 11 Surface roughening treatment with an average surface grain size of 0.5 μm or more and a surface area ratio (surface area after roughening treatment / surface area before roughening treatment) of 1.1 to 5.0 Copper foil. The surface-roughened copper foil according to claim 1, wherein the 0.2% yield strength after heating at 300 ° C for 1 hour is 160 N / mm ² or less.   On the surface roughening layer, a surface protective layer containing at least one of Ni, Zn, Cr, Co, Mo, P alone, an alloy thereof, or a hydrate thereof is formed. The surface-roughened copper foil according to claim 1 or 2.   The number of times of bending resistance by the IPC bending test (IPC standard TM-650) after heating at 300 ° C. for 1 hour is 11000 times or more, the average crystal grain size of the surface is 0.5 μm or more, and the surface area ratio (after roughening treatment) Surface area / surface area before roughening treatment) is a method for producing a surface roughened copper foil having a surface roughness of 1.1 to 5.0, wherein at least one surface of the untreated copper foil has a thiourea-based additive of 0.001 mmol. / L-The manufacturing method of the surface roughening copper foil which manufactures the copper foil which carries out surface roughening process with the electrolyte solution added to 0.1 mmol / L, and has a surface roughening process layer at least on one side.   A surface protective layer containing at least one or more of Ni, Zn, Cr, Co, Mo, P alone, an alloy thereof, or a hydrate thereof is formed on the surface roughening treatment layer. Item 5. A method for producing a surface-roughened copper foil according to Item 4.   A film is affixed on the surface roughened copper foil manufactured by the surface roughened copper foil in any one of Claims 1-3, or the surface roughened copper foil manufactured by the manufacturing method of the surface roughened copper foil of Claim 4 or 5. A circuit board.

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