WO2014104233A1

WO2014104233A1 - Low spring-back electrolytic copper foil, and circuit board and flexible circuit board using said electrolytic copper foil

Info

Publication number: WO2014104233A1
Application number: PCT/JP2013/084970
Authority: WO
Inventors: 貴広齋藤
Original assignee: 古河電気工業株式会社
Priority date: 2012-12-27
Filing date: 2013-12-26
Publication date: 2014-07-03
Also published as: TW201439379A; TWI498457B; KR20150039711A; JP5607862B1; JPWO2014104233A1; CN104321469A

Abstract

Provided is an electrolytic copper foil for flexible circuit boards, the foil being easy to handle in production/processing lines, having excellent low spring-back after the heat treatment applied in the film application process, being able to cope with reductions in the size of electrical machinery, and for which excessive coarsening of crystal grain structure is limited and fine patterning properties are excellent. An electrolytic copper foil with excellent low spring-back for which a numerical value y1, which represents rigidity and is based on a stress X1 (MPa) of a 0.2% distortion measured at normal temperature after a 300°C × 1 hour heat treatment, is less than 800 and a numerical value y2, which represents the extent of change in rigidity associated with bending and is based on the stress X1 (MPa) and a stress X2 (MPa) of a 0.4% distortion, is 1.5 or more. For the electrolytic copper foil with excellent low spring-back, it is preferable that a numerical value y3, which represents rigidity and is based on a pre-heat treatment stress X3 (MPa) of a 0.2% distortion, is 600 or more and less than 1000. y1 = (X1/0.2) y2 = (X1/0.2)/(X2/0.4) y3 = (X3/0.2)

Description

Low resilience electrolytic copper foil, wiring board and flexible wiring board using the electrolytic copper foil

The present invention relates to an electrolytic copper foil particularly excellent in low resilience and fine pattern properties. More specifically, the present invention is for a flexible wiring board excellent in low resilience and fine pattern property, in which excessive crystal coarsening is suppressed in the heat treatment applied in the film sticking step when manufacturing the flexible wiring board. The present invention relates to a suitable electrolytic copper foil.

In this specification, the definition is as follows.
“Electrolytic copper foil” represents either one or both of electrolytic copper foil and electrolytic copper alloy foil.
The “untreated” state refers to a state in which the surface is subjected to rust prevention treatment after foil formation or after foil formation, or is subjected to adhesion improving treatment such as roughening treatment as necessary, and is not subjected to heat treatment. Express.
“Low resilience” is a characteristic that can be bent with a small load and easily leads to plastic deformation.

In various electronic devices, wiring boards are used as substrates and connection materials for silicon chips and capacitors, and copper foil is generally used for the conductive layers of the wiring boards.

The copper foil of the wiring board is generally supplied in the form of a rolled copper foil or an electrolytic copper foil, and among them, an electrolytic copper foil that is highly productive and easily thinned is widely used.

At present, miniaturization of high-performance electronic devices such as information device terminals is progressing, and reduction of the internal volume of the device is an issue. Therefore, a wiring board having low resilience (hereinafter referred to as a flexible wiring board) that can be mounted efficiently and without problems in a small space in such applications has low resilience also in the copper foil as the conductive layer. Desired.

When copper foil is generally processed into the above-mentioned flexible wiring board, a heat history of around 300 ° C. is applied in a film sticking process or the like. Therefore, the low resilience described above is required in the copper foil after the thermal history is applied, and control of the characteristics is important.

It can be bent with a small load and easily leads to plastic deformation, that is, “low resilience” is a characteristic required after passing the film sticking process. A copper foil having such characteristics before the film sticking process generally tends to be wrinkled, making it difficult to handle in a production / processing line. On the other hand, even if the copper foil is excessively repulsive before the film sticking step, the foil breakage is likely to occur on the production / processing line, and handling becomes difficult.

In addition, when copper foil is used for a flexible wiring board, it is necessary to be able to form a fine pattern circuit that can cope with higher wiring density. For this purpose, the copper foil needs to have low roughness. . Further, the crystal grain structure in the copper foil needs to be fine to some extent, and the copper foil in which the crystal grain structure becomes excessively coarse by the heat treatment adversely affects the fine pattern property.

Furthermore, in order to improve fine pattern properties, it is indispensable to make the copper foil thinner. That is, the thickness of the copper foil conventionally used for flexible wiring boards has been 18 μm or 12 μm, but a copper foil of 12 μm or thinner has been demanded. In addition, the manufacturing cost of the rolled copper foil whose thickness is 18 micrometers or less becomes about 2 times higher than an electrolytic copper foil.

Patent Document 1 (Japanese Patent No. 4357548) discloses a rolled copper alloy foil excellent in bending workability by controlling crystal orientation and the like as an electrical / electronic component application such as a connector and a lead frame. However, this rolled copper alloy foil is characterized in that it does not return after bending (does not spring back). At the bending stage, its repulsive force is strong because of its high strength, and it has characteristics different from the low repulsion required by the present invention. ing.

Patent Document 2 (Japanese Patent Application Laid-Open No. 2009-242846) discloses a rolled copper alloy foil in which the repulsive force during bending is reduced by controlling the foil thickness, surface roughness, crystal orientation, and the like as a flexible wiring board application. . However, the rolled copper foil or the rolled copper alloy foil and the electrolytic copper foil of the present invention are completely different in the production method, and the required crystal structure control methods and components are also different.

Patent Document 3 (Japanese Patent Laid-Open No. 2007-320083) discloses a copper clad laminate (CCL) in which spring back is suppressed by controlling the composition of polyimide and the thickness of the copper foil layer as a flexible wiring board. However, the copper foil layer of this copper-clad laminate is only limited in thickness and does not improve the rebound itself as a crystal structure, but it is reduced by controlling the crystal structure of the copper foil layer itself. This is different from the present invention that realizes resilience.

Patent Document 4 (Patent No. 4712759) is excellent in fine pattern property by setting the surface roughness Rz of the mat surface (M surface) to 1.0 μm or less and Ra to 0.2 μm or less as a circuit board application. An electrolytic copper foil is disclosed. However, this electrolytic copper foil is characterized by excellent surface smoothness, and the low resilience required by the present invention is not a target.

Patent Document 5 (Patent No. 4,827,952) discloses an electrolytic copper foil having excellent flexibility by controlling the impurity concentration in the copper foil to be low for CCL (copper-clad laminate). However, this electrolytic copper foil can be bent with a small load, but plastic deformation is unlikely to occur as can be easily imagined from the fact that it has high flexibility that requires a wide elastic deformation region, and bending Since the amount of return later increases, the low resilience required by the present invention is not provided.

Japanese Patent No. 4357548 JP 2009-2442846 A JP 2007-320083 A Japanese Patent No. 4712759 Japanese Patent No. 4827952

The present invention is easy to handle in the production / processing line, exhibits low repulsion by the heat treatment applied in the film sticking process, or maintains low repulsion, and can cope with downsizing of electrical equipment, And it is providing the electrolytic copper foil which the excessive coarsening of a crystal grain structure is suppressed and is excellent also in fine pattern property.

In the electrolytic copper foil of the present invention, the numerical value y1 indicating the rigidity represented by Equation 1 based on the stress X1 (MPa) of 0.2% strain measured at room temperature after heat treatment at 300 ° C. for 1 hour is less than 800, and A numerical value y2 representing the degree of change in rigidity accompanying bending shown in Formula 2 based on the stress X1 (MPa) and the stress X2 (MPa) of 0.4% strain is 1.5 or more.
[Formula 1]
y1 = (X1 / 0.2) <800
[Formula 2]
y2 = (X1 / 0.2) / (X2 / 0.4) ≧ 1.5

The electrolytic copper foil preferably has a numerical value y3 indicating a rigidity represented by Equation 3 based on a stress X3 (MPa) at 0.2% strain before heat treatment (untreated) of 600 or more and less than 1000.
[Formula 3]
600 ≦ y3 = (X3 / 0.2) <1000

The electrolytic copper foil preferably has 5,000 or more crystal grains having a grain size of less than 2 μm in 300 μm square observed at room temperature after heat treatment at 300 ° C. for 1 hour.

The electrolytic copper foil preferably has a mat surface (M surface) having a surface roughness Rz of less than 3.0 μm and a shiny surface (S surface) having a surface roughness Rz of less than 3.0 μm.

The electrolytic copper foil of the present invention can be suitably used as a wiring board, and is particularly suitable for a flexible wiring board.

The electrolytic copper foil of the present invention is easy to handle in the production and processing line of the wiring board, is excellent in low resilience after the heat treatment applied in the film sticking process, and can cope with downsizing of electrical equipment, and Since both surfaces have low roughness and excessive coarsening of the crystal grain structure is suppressed, an electrolytic copper foil excellent in fine pattern property can be provided.

It is explanatory drawing which shows a drum type foil making apparatus. It is explanatory drawing which shows the measuring instrument of a resilience measurement.

In the electrolytic copper foil of the present invention, the numerical value y1 indicating the rigidity expressed by the mathematical formula 1 is less than 800 in the stress X1 (MPa) at 0.2% strain measured at room temperature after heat treatment at 300 ° C. for 1 hour, and A numerical value y2 representing the degree of change in rigidity accompanying bending shown in Formula 2 with a stress X1 (MPa) and a stress X2 (MPa) at 0.4% strain is 1.5 or more.
[Formula 1] y1 = (X1 / 0.2) <800
[Formula 2] y2 = (X1 / 0.2) / (X2 / 0.4) ≧ 1.5
If the numerical value y1 is less than 800, the rigidity is small, so that bending with a small load is possible. On the other hand, if it is 800 or more, the rigidity becomes large, so it is difficult to bend with a small load.

The numerical value y2 represents the degree of change in rigidity accompanying bending, and the larger the numerical value y2, the easier the plastic deformation occurs due to bending, and the smaller the return amount of the spring property after bending. When the numerical value of y2 is less than 1.5, plastic deformation due to bending hardly occurs, and the return amount of the spring property after bending increases.
Even if the numerical value y2 is less than 1.5, if the stress X1 and the stress X2 are small, it seems that there is no problem in low resilience, but since the plastic deformation is difficult to occur, the return amount of the spring property after bending is small. Since it becomes large, the required low resilience cannot be obtained.

In the electrolytic copper foil of the present invention, before the heat treatment (untreated), the numerical value y3 indicating the rigidity represented by the mathematical formula 3 at a stress X3 (MPa) at 0.2% strain is 600 or more and less than 1000. Features.
[Formula 3] 600 ≦ y3 = (X3 / 0.2) <1000
If the numerical value y3 indicating the rigidity is 600 or more and less than 1000, the rigidity is moderate and good handling properties are maintained. On the other hand, if the numerical value y3 is less than 600, the rigidity is too weak and wrinkles are likely to occur in the production / processing line, making handling difficult. Further, even if the numerical value y3 is 1000 or more, the rigidity is too strong, and the foil is easily cut off in the production / processing line, so that handling becomes difficult.

The electrolytic copper foil of the present invention is characterized in that the number of crystal grains having a particle size of less than 2 μm in 300 μm square observed at room temperature after heat treatment at 300 ° C. for 1 hour is 5,000 or more.
If the number of crystal grains is 5,000 or more, the crystal structure is fine and good fine pattern properties are maintained.
On the other hand, if the number of crystal grains having a grain size of less than 2 μm in a 300 μm square is less than 5,000, the crystal grain structure becomes coarse and adversely affects fine pattern properties.

The electrolytic copper foil of the present invention is characterized in that the surface roughness Rz of the M plane is less than 3.0 μm and the surface roughness Rz of the S plane is less than 3.0 μm.
If Rz is less than 3.0 μm, the surface irregularities are small and good fine pattern properties are maintained.
On the other hand, if Rz is 3.0 μm or more, the unevenness of the surface is large, and the fine pattern property is adversely affected.

Hereinafter, one embodiment of the present invention will be described in detail.
Usually, the electrolytic copper foil is made by, for example, an electrolytic foil making apparatus shown in FIG. The electrolytic foil making apparatus comprises a rotating drum-like cathode 2 (the surface is made of SUS or titanium), and an anode 1 (lead electrode or noble metal oxide-coated titanium electrode) arranged concentrically with respect to the cathode 2. While supplying the electrolytic solution 3 to the foil making apparatus, current is passed between both electrodes to deposit copper to a predetermined thickness on the surface of the cathode 2, and then the copper is peeled off from the surface of the cathode 2 in the form of foil. In addition, the surface of the untreated (before electrolytic treatment) electrolytic copper foil 4 in contact with the electrolytic solution 3 is the mat surface (M surface), and the surface in contact with the drum-like cathode 2 is the shiny surface (S surface).
In the above description, the foil manufacturing apparatus using the drum-like cathode 2 has been described. However, the copper foil may be manufactured by a foil manufacturing apparatus having a plate-like cathode.

In order to form an electrolytic copper foil with the apparatus shown in FIG. 1, a copper sulfate plating solution is used as the electrolytic solution 3. The sulfuric acid concentration of the copper sulfate plating solution is preferably 20 to 150 g / L, particularly 30 to 100 g / L. When the sulfuric acid concentration is less than 20 g / L, it becomes difficult to flow an electric current, so that practical operation becomes difficult, and the uniformity of plating and electrodeposition are also deteriorated. When the sulfuric acid concentration exceeds 150 g / L, the solubility of copper is lowered, so that a sufficient copper concentration cannot be obtained, and realistic operation becomes difficult. Also, corrosion of equipment is promoted.

The copper concentration is preferably 40 to 150 g / L, particularly 60 to 100 g / L. When the copper concentration is less than 40 g / L, it is difficult to secure a current density that allows practical operation in the production of electrolytic copper foil. Increasing the copper concentration above 150 g / L is not practical because a considerably high temperature is required.

An organic additive and chlorine are added to the copper sulfate plating solution. Organic additives to be added to the copper sulfate plating bath are two kinds of organic additives, a compound having a mercapto group and a polymer polysaccharide. A compound having a mercapto group has an effect of promoting copper electrodeposition, and a high molecular polysaccharide has an effect of suppressing copper electrodeposition. By appropriately exerting both of the promotion and suppression effects, copper electrodeposition is promoted with respect to the concave portions generated in the foil making, and copper electrodeposition is suppressed with respect to the convex portions. A smoothing effect on the precipitation surface is obtained.
In addition, the crystal structure control effect exerted by the optimum concentration of the two organic additives facilitates plastic deformation with a small bend, which is a feature of the present invention. An excessively coarse grain structure is suppressed, and an electrolytic copper foil having low roughness is obtained.
The added chlorine acts as a catalyst that effectively exhibits the effects of the two organic additives.

For the compound having a mercapto group, either MPS-Na (sodium 3-mercapto-1-propanesulfonate) or SPS-Na {bis (3-sulfopropyl) disulfide sodium} is selected. In terms of organic structure, SPS is a dimer of MPS, exhibits the same effect as an additive, and has the same required concentration.
The concentration is preferably from 0.25 ppm to 7.5 ppm, particularly preferably from 1.0 ppm to 5.0 ppm. If it is less than 0.25 ppm, it is difficult to exhibit the effect of promoting electrodeposition on the concave portions generated in the foil production, and the effect of controlling the crystal structure, which is a feature of the present invention, is also hardly exhibited. On the other hand, if it exceeds 7.5 ppm, the electrodeposition promoting effect on the convex portion becomes excessive, partial abnormal precipitation is likely to occur, it becomes difficult to produce a copper foil with a normal appearance, and the cost of the additive only increases. The improvement of physical properties cannot be expected.

The high molecular polysaccharide is HEC (hydroxyethyl cellulose), and the concentration is preferably 3.0 ppm or more and 30 ppm or less, and particularly preferably 10 ppm or more and 20 ppm or less. If it is less than 3.0 ppm, the electrodeposition suppressing effect on the convex portion is hardly exhibited, and the effect of controlling the crystal structure, which is a feature of the present invention, is hardly exhibited. On the other hand, if it exceeds 30 ppm, the generation of bubbles, which is an effect peculiar to polymer polysaccharides, becomes excessive, the supply of copper ions becomes insufficient, and it becomes difficult to produce a normal copper foil, and the organic matter in the electrolyte increases. By doing so, it causes “burn plating” to occur.

Add chlorine to the electrolyte. The chlorine concentration is preferably from 1 ppm to 20 ppm, particularly preferably from 5 ppm to 15 ppm. Chlorine acts as a catalyst that effectively exhibits the effects of the two organic additives. If the chlorine concentration is less than 1 ppm, it is difficult to exert the catalytic action described above, and it is difficult to bring out the effect of the organic additive. is not. Further, if it exceeds 20 ppm, not only the catalytic action of chlorine on the organic additive but also the influence on the electrodeposition of chlorine itself becomes large, so the effect of controlling the crystal structure by the additive which is a feature of the present invention is also exhibited. It becomes difficult.

The current density for foil production is preferably 20 to 200 A / dm ² , particularly preferably 30 to 120 A / dm ² . When the current density is less than 20 A / dm ² , production efficiency is very low in the production of electrolytic copper foil, which is not realistic. This is because, in order to increase the current density from 200 A / dm ^2, a high copper concentration, a high temperature, and a high flow rate are required, which imposes a large burden on the electrolytic copper foil manufacturing facility and is not realistic.

The electrolytic bath temperature is preferably 25 to 80 ° C, particularly 30 to 70 ° C. When the bath temperature is less than 25 ° C., it is difficult to secure a sufficient copper concentration and current density in the production of the electrolytic copper foil, which is not realistic. Further, raising the temperature from 80 ° C. is very difficult in operation and facilities and is not realistic.
The above electrolysis conditions are appropriately adjusted from the respective ranges so as not to cause problems such as copper deposition and plating burns.

Since the surface roughness immediately after the production of the electrolytic copper foil transfers the roughness of the surface of the cathode 2, it is preferable to use a cathode having a surface roughness Rz of 0.1 to 3.0 μm. By using such a cathode, since the surface roughness of the S surface immediately after the production of the electrolytic copper foil is a transfer of the cathode surface, the surface roughness Rz of the S surface can be 0.1 to 3.0 μm. . The reason why the surface roughness Rz of the S surface of the electrolytic copper foil is less than 0.1 μm is that the surface roughness Rz of the cathode is less than 0.1 μm. It is difficult to finish smoothly and is not suitable for mass production. On the other hand, when the roughness Rz of the S surface is 3.0 μm or more, the fine pattern property is lowered and the characteristics required by the present invention cannot be obtained.

The surface roughness Rz of the M surface of the electrolytic copper foil is preferably 0.05 to 3.0 μm. In order to finish the surface roughness Rz to a roughness of less than 0.05 μm, even if bright plating is performed, it is very difficult and practically impossible to manufacture. On the other hand, if the surface roughness Rz of the M-plane is 3.0 μm or more, the fine pattern property is lowered, and the characteristics required by the present invention cannot be obtained. It is more preferable that the roughness Rz of the S surface and the M surface is less than 1.5 μm.

The thickness of the electrolytic copper foil is preferably 3 μm to 210 μm. A copper foil having a thickness of less than 3 μm is not practical because of severe manufacturing conditions due to handling techniques and the like. The upper limit of the thickness is about 210 μm from the current usage state of the circuit board. This is because it is unlikely that an electrolytic copper foil having a thickness of 210 μm or more is used as a copper foil for a wiring board, and the cost merit of using the electrolytic copper foil is lost.
In the present invention, in order to improve the fine pattern property, the thickness of the foil is preferably 18 μm or less, preferably 12 μm or less.

Hereinafter, the present invention will be described based on examples, but the present invention is not limited thereto.

(1) Foil making Examples 1-8, Comparative Examples 1-6
For Examples 1 to 8 and Comparative Examples 1 to 6, (a) a copper sulfate (H ₂ SO ₄ ) plating solution having the composition shown in Table 1 was passed through an activated carbon filter for cleaning treatment, and the additives shown in Table 1 were also used. Was added to obtain a predetermined concentration, and (b) electrolytic foil formation was performed at a current density shown in Table 1 using the rotary drum type foil making apparatus shown in FIG. 1 to produce an electrolytic copper foil having a thickness of 12 μm. Note that the surface of the drum was polished with a polishing cloth before the foil formation. At that time, Examples 1-7 and Comparative Examples 1-5 were polished with # 1500 polishing cloth, and Examples 8 and 6 were polished with # 800 polishing cloth.
For Comparative Example 7, an electrolytic copper foil having a thickness of 12 μm was produced with reference to Example 6 (MPS ratio = 3, PBF ratio 15, HEC ratio 4) of Patent Document 4 (Japanese Patent No. 4712759).
For Comparative Example 8, an electrolytic copper foil having a thickness of 12 μm was produced with reference to Example 4 (copper sulfate plating solution, copper 70 g / l, sulfuric acid 50 g / l) of Patent Document 5 (Japanese Patent No. 48279952). .

(1) Preparation of measurement / test samples Untreated electrolytic copper foils of each of the Examples and Comparative Examples prepared were divided into 6 samples (Samples 1 to 6) and used for the following measurement / test.
Sample 1
First, the sample 1 was used untreated (= before heat treatment) and a tensile test was performed to measure the stress at 0.2% strain.
Samples 2 and 3
After two samples were heat-treated in a nitrogen atmosphere at 300 ° C. for 1 hour, one sample 2 was subjected to a tensile test, and stress at 0.2% strain and 0.4% strain at room temperature. The stress at the time was measured. The remaining sample 3 was used for rebound measurement.
Sample 4
The sample 4 was heat-treated at 300 ° C. for 1 hour, and then the distribution of crystal grain size was calculated by EBSD measurement at room temperature.
Sample 5
Sample 5 was used to measure surface roughness.
Sample 6
Sample 6 was used to evaluate fine pattern properties.

Details of each measurement and test are described below.
(2) Tensile test
Sample 1 was cut into a 6 inch × 0.5 inch wide test piece, and a stress at 0.2% strain was measured using a tensile tester. The tensile speed was 50 mm / min.
Sample 2 was cut into a test piece having a length of 6 inches and a width of 0.5 inches, and a stress at 0.2% strain and a stress at 0.4% strain were measured using a tensile tester. The tensile speed was 50 mm / min.
The stress at 0.2% strain at room temperature is, as the name suggests, the stress value shown at 0.2% strain at room temperature, and the stress at 0.4% strain is the same. The measurement results are shown in Table 2.

(3) Measurement of resilience The resilience was measured using the apparatus shown in FIG. The copper foil 5 to be a test piece was placed in a coiled shape, crushed until the crushing distance 7 became a specified distance, the load measured by the electronic balance 6 was measured as a repulsive load, and the resilience was evaluated. .
Specifically, the sample 3 was cut into a test piece having a length of 40 mm and a width of 15 mm, rounded with a coil length of 10 mm (= coil circumference of 10 mm), and rebound characteristics were measured under the following conditions.
Coil length: 10mm
Crushing distance: 1mm, 3mm
Measurement time: 30 seconds after crushing Measuring method: Measured with electronic balance as repulsive load In repulsive measurement, repulsive load with crushing distance of 3 mm and 1 mm for “ease of bending with small load” A sample with a value of less than 25 gf was evaluated as ◯ (passed), and a sample of 25 gf or higher was evaluated as x (failed).
Furthermore, regarding "ease of plastic deformation"
(Repulsive load with a crushing distance of 1 mm) / (Repulsive load with a crushing distance of 3 mm)
A sample having a numerical value of less than 1.05 was evaluated as ◯ (pass), and a sample of 1.05 or more was evaluated as × (fail). A small numerical value indicates that there is little difference in the repulsive load between the crushing distance of 3 mm and the crushing distance of 1 mm. That is, as the numerical value is smaller, the deformation is mainly in the plastic region than the deformation in the elastic region where the deformation amount and the repulsive load are proportional, and the return amount after bending is smaller.
The measurement results are shown in Table 2.

(4) Calculation of the number of crystal grains having a particle size of less than 2 μm by EBSD measurement The surface of the M surface of sample 4 is etched with a chemical to form a measurement surface, with measurement conditions of a field of view of 300 μm square and a step size of 0.5 μm. The number of crystal grains having a particle size of less than 2 μm was calculated. For analysis and calculation, analysis software “OIM” manufactured by TSL was used.
Regarding the number of crystal grains, a deviation of 5 ° or more was defined as a grain boundary, and the diameter of a circle having the same area as each crystal grain area was calculated as the crystal grain diameter. Table 3 shows the measurement results.

(5) Surface roughness measurement The sample 5 was used to measure the surface roughness Rz using a contact-type surface roughness meter.
The surface roughness is indicated by Rz (10-point average roughness) defined in JIS-B-0601. The reference length was 0.8 mm. When this measuring instrument is used, three measurement values of Ra, Ry, and Rz can be obtained by one measurement. In the present invention, Rz is adopted as the surface roughness. Table 3 shows the measurement results.

(6) Evaluation of Fine Pattern Properties Fine pattern properties were evaluated using Sample 6. For evaluation, after heat-pressing the M surface to a polyimide film at 300 ° C. for 1 hour, the S surface is masked with L / S (Line and Space) = 25 μm / 25 μm and etched with a copper chloride solution. The circuit pattern created in the above was used.
In the evaluation method, the circuit pattern was observed with a microscope from directly above, and the difference between the upper limit and the lower limit of the circuit width was measured at a circuit length of 100 μm. When the difference between the upper limit and the lower limit of the circuit width was less than 1 μm, ◎ (particularly good), and less than 3 μm were judged as ◯ (pass), and the others were judged as x (fail).
The results are shown in Table 3.

As is apparent from Table 2, in Examples 1 to 8, the numerical value y1 indicating the rigidity expressed by Equation 1 is less than 800 and can be bent with a small load.
Further, in Examples 1 to 8, the numerical value y2 representing the degree of change in rigidity accompanying bending shown in Expression 2 is 1.5 or more, and plastic deformation due to bending is easily caused.
Actually, in the resilience measurement, Examples 1 to 8 passed the evaluation of “ease of bending with a small load” and “ease of plastic deformation”.
Further, in Examples 1 to 6 and 8, the numerical value y3 indicating the rigidity represented by Expression 3 is 600 or more and less than 1000, and the rigidity is not too strong, so that handling in the production / processing line is easy.

In the CCL manufacturing / processing line, not only a manufacturing method in which an unprocessed copper foil and a substrate are laminated and heat-treated, but also a manufacturing method in which the copper foil is first heat-treated and then passed through the manufacturing / processing line is assumed.
In the latter case, even if the numerical value y3 indicating the rigidity at the untreated copper foil stage is 1000 or more, if the numerical value y1 indicating the rigidity after the heat treatment at 300 ° C. × 1 hour is less than 1000, handling becomes easy. . For example, in Example 7, the numerical value y3 indicating rigidity is 1000 or more. However, if heat treatment is performed at 300 ° C. for 1 hour before passing through the manufacturing / processing line, the numerical value y1 is less than 1000, so that it can be used effectively. it can.
Depending on the wiring board, the heating condition may be less than 300 ° C. In such a case, as shown in Example 6, the numerical value y1 after heat treatment at 300 ° C. × 1 hour is less than 600, and even a copper foil that is likely to have too low rigidity becomes 600 or more depending on the heating conditions. Can be used for

As is clear from Table 2, in Comparative Examples 3, 4, and 7, the numerical value y1 indicating the rigidity expressed by Equation 1 is 800 or more, so it is difficult to bend with a small load. Further, in Comparative Examples 1 to 7, since the numerical value y2 representing the degree of change in rigidity accompanying bending shown in Equation 2 is less than 1.5, plastic deformation due to bending is difficult to occur.
Actually, Comparative Examples 3, 4, and 7 were rejected because of “easiness of bending with a small load” in the resilience measurement, and Comparative Examples 1 to 8 were not acceptable in the evaluation of “ease of plastic deformation”. It has passed.
Moreover, since the numerical value y3 which shows rigidity is 1000 or more in Comparative Examples 1, 2 and 5, 6, the rigidity is too strong, and the foil breakage easily occurs in the manufacturing / processing line, so that handling becomes difficult.

As is apparent from Table 3, in Examples 1 to 5 and 7, the number of crystal grains having a particle size of less than 2 μm measured at room temperature after heat treatment at 300 ° C. for 1 hour is 5,000 or more in 300 μm square, so that Since excessive coarsening of the crystal grain structure is suppressed and the surface roughness is less than 3.0 μm, the fine pattern property is excellent.
In Example 6, the surface roughness is less than 3.0 μm, but the number of crystal grains having a grain size of less than 2 μm measured at room temperature after 300 ° C. × 1 hour heat treatment is less than 5,000. The heat treatment applied in the film sticking step or the like cannot be preferably used at about 300 ° C. However, since it is excellent in low resilience, it can be suitably used for products whose heat treatment is greatly below 300 ° C.
In Example 8, the number of crystal grains having a grain size of less than 2 μm measured at room temperature after heat treatment at 300 ° C. for 1 hour is equal to that in Example 2, but the surface roughness is 3.0 μm or more on both sides, and there are irregularities. Since it is large, the fine pattern property is inferior. However, since it has excellent low resilience, it can be effectively employed for a wiring board that does not require a fine circuit.

As is apparent from Table 3, in Comparative Examples 1 and 2, the number of crystal grains having a grain size of less than 2 μm measured at room temperature after heat treatment at 300 ° C. for 1 hour is 5,000 or more, but the surface roughness of the M-plane Is 3.0 μm or more and the unevenness is large, so that the fine pattern property is inferior.
In Comparative Example 5, the surface roughness is less than 3.0 μm, but the number of crystal grains having a grain size of less than 2 μm measured at room temperature after heat treatment at 300 ° C. for 1 hour is less than 5,000, Since the grain structure is excessively coarse, the fine pattern property is adversely affected.
Further, Comparative Example 6 has a surface roughness of 3.0 μm or more, large irregularities, and the number of crystal grains having a grain size of less than 2 μm measured at room temperature after heat treatment at 300 ° C. for 1 hour is less than 5,000. In addition, since the crystal grain structure is excessively coarse, the fine pattern property is very poor.

As is clear from the results of this example, the electrolytic copper foil of the present invention is easy to handle in the production / processing line and exhibits low resilience in the heat treatment applied in the film sticking process (stacking process with the substrate). Thus, it is possible to provide an electrolytic copper foil for a flexible wiring board that can cope with downsizing of electrical equipment, suppresses excessive coarsening of the crystal grain structure, and is excellent in fine pattern properties.
Moreover, since the electrolytic copper foil of this invention is excellent in fine pattern property, of course, it can apply also to the wiring board which does not require flexibility.

In the electrolytic copper foil of the present invention, MPS-Na or SPS-Na is added as a compound having a mercapto group in a concentration range of 0.25 ppm to 7.5 ppm, and HEC is 3.0 ppm to 30 ppm as a polymer polysaccharide. It is possible to make a foil with an acidic copper electrolytic solution to which chlorine ions are added in the range of 1 ppm to 20 ppm.
In addition, since the electrolytic copper foil of the present invention is subjected to surface treatment such as rust prevention treatment and then laminated with a film substrate as it is, it is excellent in surface smoothness, so it can be suitably used as a high-frequency flexible wiring board. Can do. Further, a roughening treatment layer for the purpose of improving the adhesion by the anchor effect can be provided on one surface. The roughening process is not an essential process as long as the target performance can be achieved.

The electrolytic copper foil of the present invention is also effective as a high-frequency wiring board by utilizing the smoothness of the surface. Since it has low resilience, it is effective as a high-frequency wiring board that requires such characteristics.
In addition, the unique characteristics of both surface smoothness, “ease of bending under small load” and “ease of plastic deformation” make it possible to provide copper foil for various materials as well as wiring boards. is there.

1: Anode 2: Cathode 3: Electrolytic solution 4: Untreated electrolytic copper foil 5: Copper foil 6: Electronic balance 7: Crushing distance

Claims

An electrolytic copper foil, the numerical value y1 indicating the stiffness represented by Formula 1 based on 0.2% strain stress X1 (MPa) measured at room temperature after heat treatment at 300 ° C. for 1 hour is less than 800, and the stress An electrolytic copper foil in which a numerical value y2 representing a degree of change in rigidity accompanying bending shown by Formula 2 based on X1 (MPa) and a stress X2 (MPa) of 0.4% strain is 1.5 or more.
[Formula 1]
y1 = (X1 / 0.2)
[Formula 2]
y2 = (X1 / 0.2) / (X2 / 0.4)
2. The electrolytic copper foil according to claim 1, wherein a numerical value y <b> 3 indicating rigidity represented by Formula 3 based on a stress X3 (MPa) of 0.2% strain before heat treatment is 600 or more and less than 1000. 3.
[Formula 3]
600 ≦ y3 = (X3 / 0.2) <1000
3. The electrolytic copper foil according to claim 1, wherein the number of crystal grains having a grain size of less than 2 μm in a 300 μm square observed at room temperature after heat treatment at 300 ° C. for 1 hour is 5,000 or more.
4. The electrolytic copper foil according to claim 1, wherein the surface roughness Rz of the M surface is less than 3.0 μm and the surface roughness Rz of the S surface is less than 3.0 μm.
A wiring board manufactured using the electrolytic copper foil according to any one of claims 1 to 4.
A flexible wiring board manufactured using the electrolytic copper foil according to any one of claims 1 to 4.