JP6845382B1 - Surface-treated copper foil, copper-clad laminate, and printed wiring board - Google Patents

Abstract

Provided is a surface-treated copper foil having fine wiring workability and excellent adhesion to a resin substrate. A surface-treated copper foil having a roughened surface on its surface, the minimum autocorrelation length Sal of the roughened surface is 1.0 μm or more and 8.5 μm or less, and the root mean square height Sq is 0. It is 10 μm or more and 0.98 μm or less.

Description

The present invention provides a surface-treated copper foil suitable for a printed wiring board (particularly, a printed wiring board having a high-density wiring circuit (fine pattern)) and the like, and a surface-treated copper foil having excellent adhesion to a resin substrate. The present invention relates to a copper-clad laminate and a printed wiring board using a surface-treated copper foil.

As the copper foil used for the copper-clad laminate and the printed wiring board, the electrolytic copper foil obtained by peeling the copper foil deposited on the drum of the electrolytic precipitation device from the drum is used. The electric field precipitation start surface (hereinafter referred to as "drum surface") of the electrolytic copper foil peeled from the drum is relatively smooth, and is the opposite surface, that is, the electrolytic precipitation end surface (hereinafter referred to as "precipitation surface"). (Note) generally has irregularities. A resin substrate is placed on the precipitation surface of the electrolytic copper foil and thermocompression bonded to produce a copper-clad laminate. Generally, the precipitation surface is roughened by roughening to obtain a resin substrate. The adhesiveness of the is improved.

Recently, a copper foil with a resin, in which an adhesive resin such as an epoxy resin is previously attached to the roughened surface of the copper foil and the adhesive resin is used as an insulating resin layer in a semi-cured state (B stage), is used for forming a surface circuit. It is used as a copper foil of the above, and the side of the insulating resin layer is heat-bonded to the insulating substrate to manufacture a printed wiring board (particularly a build-up wiring board). In the build-up wiring board, it is required to highly integrate various electronic components, and in response to this, the wiring pattern is also required to have a high density, and the wiring pattern of fine line width and line pitch, so-called fine. Printed wiring boards with patterns are being sought after. For example, in a multilayer board used for a server, a router, a communication base station, an in-vehicle board, etc., or a multilayer board for a smartphone, a printed wiring board having high-density ultrafine wiring (hereinafter referred to as "high-density wiring board") is used. It is required.

The high-density wiring board of AnyLayer (connecting layers with a laser via with a high degree of freedom of arrangement) is mainly used for the main board of smartphones, but in recent years, fine wiring has progressed, and the line width and line spacing have been improved. Wiring with a pitch (hereinafter referred to as “L & S”) of, for example, 30 μm or less is required.
However, as the wiring becomes finer, the problem of moisture absorption deterioration in which the adhesion between the wiring and the resin is lowered due to the influence of the moisture absorbed by the resin of the high-density wiring board has become apparent. In particular, in recent smartphones, the increase in heat generation accompanying the increase in power consumption tends to accelerate the deterioration of moisture absorption, and it is not easy to maintain the adhesion between the wiring and the resin.

Patent Document 1 discloses a copper foil having excellent adhesion to a highly heat-resistant resin by sharpening the shape of the roughened particles, but roughening the sharpened shape during etching for wiring formation. Since the particles tend to remain undissolved (root residue), there is a risk that the fine wiring workability will be insufficient.
Patent Document 2 discloses a copper foil having a small drum surface roughness and excellent fine wiring workability, but since measures against moisture absorbed by the resin substrate are not taken, it is used in a high temperature and high humidity environment. However, there is a risk that the adhesion between the copper foil and the resin substrate may decrease.
Patent Document 3 discloses a copper foil having excellent high-frequency characteristics in which the steepness of change in the uneven shape of the surface is controlled. However, a high-density wiring board having fine wiring with L & S of, for example, 30 μm or less is produced. In this case, the adhesion between the copper foil and the resin substrate in a high temperature and high humidity environment may decrease.

Japanese Patent Publication No. 2010 No. 236058 Japanese Patent Publication No. 76601, 2018 International Publication No. 2018/1989905

An object of the present invention is to provide a surface-treated copper foil having fine wiring workability and excellent adhesion to a resin substrate. Another object of the present invention is to provide a copper-clad laminate having fine wiring processability and a printed wiring board capable of forming high-density ultrafine wiring.

The surface-treated copper foil according to one aspect of the present invention is a surface-treated copper foil having a roughened surface on the surface, and the minimum autocorrelation length Sal of the roughened surface is 1.0 μm or more and 8.5 μm. The gist is that the root mean square height Sq is 0.10 μm or more and 0.98 μm or less.
Further, it is a gist that the copper-clad laminate according to another aspect of the present invention includes a surface-treated copper foil according to the above aspect and a resin substrate laminated on the roughened surface of the surface-treated copper foil. And.
Furthermore, it is a gist that the printed wiring board according to another aspect of the present invention includes a copper-clad laminate according to the other aspect.

The surface-treated copper foil of the present invention has fine wiring workability and is excellent in adhesion to a resin substrate. Further, the copper-clad laminate of the present invention has fine wiring workability. Further, the printed wiring board of the present invention can form high-density ultrafine wiring.

It is a figure explaining the method of manufacturing the electrolytic copper foil using an electrolytic precipitation apparatus.

An embodiment of the present invention will be described. The embodiments described below show an example of the present invention. In addition, various changes or improvements can be added to the present embodiment, and the modified or improved forms may be included in the present invention.
The surface-treated copper foil according to the embodiment of the present invention is a surface-treated copper foil having a roughened surface on the surface, and the minimum autocorrelation length Sal of the roughened surface is 1.0 μm or more. It is 5 μm or less, and the root mean square height Sq is 0.10 μm or more and 0.98 μm or less.

From such a configuration, the surface-treated copper foil of the present embodiment has fine wiring workability compatible with a high-density wiring board, adherence to a resin substrate in a normal state, and high temperature and high humidity. Excellent adhesion under environment (for example, after pressure cooker test). Therefore, the surface-treated copper foil according to the present embodiment can be suitably used for manufacturing a copper-clad laminate or a printed wiring board. By using the surface-treated copper foil of the present embodiment, it is possible to manufacture a copper-clad laminate having fine wiring processability. Further, by using the surface-treated copper foil of the present embodiment, it is possible to manufacture a printed wiring board having high-density ultrafine wiring. In the present invention, the "normal state" means a state in which the surface-treated copper foil is placed at room temperature and normal humidity (for example, temperature 23 ± 2 ° C., humidity 50 ± 5% RH).

The minimum autocorrelation length Sal is a value defined by ISO25178, and the shortest in-plane distance (unless otherwise specified) at which the surface shape autocorrelation function (see Equation 1 below) decays to the correlation value s. It is defined as (the shortest distance at which s decays from 1 to 0.2) and can be measured, for example, by a three-dimensional white light interference microscope or a laser microscope. In the copper foil, the minimum autocorrelation length Sal can be used as an index of the steepness of the change in the uneven shape of the surface caused by the waviness of the surface of the copper foil. That is, it can be said that the smaller the value of the minimum autocorrelation length Sal, the steeper the change in the uneven shape of the surface because the height difference changes in a shorter distance.

The root mean square height Sq is a value defined by ISO25178 and is defined as a standard deviation of the distance from the mean plane as expressed by the following equation 2, for example, a three-dimensional white light interference type microscope or a laser microscope. Can be measured by. The root mean square height Sq represents the variation in the unevenness of the surface shape caused by the roughened shape or the like in the copper foil. Note that z (x, y) in Equations 1 and 2 indicates the coordinates in the height direction in the x, y coordinates.

The surface-treated copper foil of the present embodiment will be described in more detail below.
As a result of diligent studies, the present inventors have determined that the moisture absorption phenomenon in a high temperature and high humidity environment in the pressure cooker test (hereinafter referred to as "PCT") includes moisture absorption from the surface of the resin substrate and copper foil. There are two types, moisture absorption from the interface of the resin substrate, and the contribution of moisture absorption from the interface between the copper foil and the resin substrate is large in reducing the adhesion between the resin substrate and the copper foil after PCT. I found that. When moisture invades the interface between the copper foil and the resin substrate, the chemical components that enhance the adhesion such as the coupling agent are hydrolyzed, and the oxide film grows on the surface of the copper foil due to the influence of the moisture. It is considered that the bonding force at the interface between the copper foil and the resin substrate is reduced, and the adhesion between the copper foil and the resin substrate is reduced.

Since the waviness of the roughened surface of the surface-treated copper foil having the minimum autocorrelation length Sal of 1.0 μm or more and 8.5 μm or less has a moderately steep change, the interface between the surface-treated copper foil and the resin substrate The diffusion rate of water in is slowed down. Therefore, the interface between the surface-treated copper foil and the resin substrate is kept normal even in a high-temperature and high-humidity environment (for example, after PCT), so that the adhesion between the surface-treated copper foil and the resin substrate is maintained high. Cheap.

When the minimum autocorrelation length Sal of the roughened surface of the surface-treated copper foil exceeds 8.5 μm, the waviness is gentle, so that the diffusion rate of moisture at the interface between the surface-treated copper foil and the resin substrate is high, and the temperature and humidity are high. In an environment, the adhesion between the surface-treated copper foil and the resin substrate may decrease. On the other hand, if the minimum autocorrelation length Sal of the roughened surface of the surface-treated copper foil is less than 1.0 μm, the swell changes excessively steeply, so that the interface between the surface-treated copper foil and the resin substrate Gap is easy to form. Then, in a high-temperature and high-humidity environment, moisture tends to accumulate in the gaps, so that the adhesion between the surface-treated copper foil and the resin substrate may decrease.

Further, in a high-density wiring board, in order to achieve both adhesion between the surface-treated copper foil and the resin substrate in a high-temperature and high-humidity environment and fine wiring workability, the wavy shape of the roughened surface of the surface-treated copper foil is required. At the same time, it is necessary to control the roughness of fine irregularities.
If the minimum autocorrelation length Sal of the roughened surface of the surface-treated copper foil is 1.0 μm or more and 8.5 μm or less, and the root mean square height Sq is 0.10 μm or more and 0.98 μm or less, the high temperature is high. Surface treatment in a humid environment Adhesion between the copper foil and the resin substrate and fine wiring workability are compatible at a high level.

The surface-treated copper foil having a root mean square height Sq of 0.10 μm or more and 0.98 μm or less on the roughened surface has an appropriate height of fine irregularities, so that the surface is formed when wiring is formed by etching. The treated copper foil melts stably, and it is easy to obtain a pattern with a high etching factor (that is, the cross-sectional shape of the wiring tends to be close to a rectangle).

When the root mean square height Sq of the roughened surface of the surface-treated copper foil exceeds 0.98 μm, locally high protrusions of the surface-treated copper foil are formed on the resin substrate when the wiring is formed by etching. Undissolved residue (that is, root residue occurs) and the etching factor may decrease. If the root mean square height Sq of the roughened surface of the surface-treated copper foil is less than 0.10 μm, the fine irregularities are too small. Adhesion may decrease.

The minimum autocorrelation length Sal of the roughened surface is preferably 1.3 μm or more and 6.5 μm or less, and more preferably 1.7 μm or more and 5.7 μm or less. The root mean square height Sq of the roughened surface is preferably 0.21 μm or more and 0.72 μm or less, and more preferably 0.28 μm or more and 0.54 μm or less.

Further, the ten-point average roughness Rz of the roughened surface measured by using a contact type surface roughness measuring machine is preferably 1.2 μm or more and 3.8 μm or less. When the ten-point average roughness Rz of the roughened surface is within the above range, the effect of improving the adhesion in the normal state is achieved by the anchor effect.

Further, the surface-treated copper foil of the present embodiment can be produced by roughening the surface of the electrolytic copper foil to obtain a roughened surface, but the surface to be roughened may be a drum surface. It may be a precipitation surface. For example, if the drum surface of the electrolytic copper foil is subjected to a roughening treatment, the roughened surface is formed on the drum surface of the electrolytic copper foil.

The surface-treated copper foil according to the present embodiment will be described in more detail below. First, an example of a method for producing a surface-treated copper foil will be described.
(1) Method for producing electrolytic copper foil The electrolytic copper foil can be produced, for example, by using an electrolytic precipitation device as shown in FIG. The electrolytic precipitation device of FIG. 1 polishes an insoluble anode 104 made of titanium coated with a platinum group element or an oxide thereof, a titanium cathode drum 102 provided facing the insoluble anode 104, and a cathode drum 102. It is provided with a buff 103 that removes an oxide film formed on the surface of the cathode drum 102.

An electrolytic solution 105 (sulfuric acid-copper sulfate aqueous solution) is supplied between the cathode drum 102 and the insoluble anode 104, and a direct current is applied between the cathode drum 102 and the insoluble anode 104 while rotating the cathode drum 102 at a constant speed. Energize. As a result, copper is deposited on the surface of the cathode drum 102. The electrolytic copper foil 101 is obtained by peeling the precipitated copper from the surface of the cathode drum 102 and continuously winding it.

In the production of the electrolytic copper foil, an additive may be added to the electrolytic solution 105. Various additives can be used, and examples thereof include ethylenethiourea, polyethylene glycol, tetramethylthiourea, and polyacrylamide. Here, by increasing the addition amounts of ethylene thiourea and tetramethyl thiourea, the tensile strength of the electrolytic copper foil under normal conditions and the tensile strength of the electrolytic copper foil measured at room temperature after heating at 220 ° C. for 2 hours are improved. Can be done.

Molybdenum may be added to the electrolytic solution 105. By adding molybdenum, the etchability of the copper foil can be improved. Normally, in electrolytic precipitation, the copper concentration of the electrolytic solution 105 (the concentration of only copper of copper sulfate that does not consider the sulfuric acid content) is 13 to 72 g / L, the sulfuric acid concentration of the electrolytic solution 105 is 26 to 133 g / L, and the electrolytic solution. The liquid temperature of 105 is 18 to 67 ° C., the current density is 3 to 67 A / dm ² , and the processing time is 1 second or more and 1 minute 55 seconds or less.

(2) Surface treatment of electrolytic copper foil <Waviness processing>
The swelling process is a process performed to adjust the minimum autocorrelation length Sal and the root mean square height Sq of the surface of the copper foil. In order to set the minimum autocorrelation length Sal of the roughened surface of the surface-treated copper foil within the above numerical range, it is necessary to control the undulation shape of the surface of the electrolytic copper foil by the swell processing.

As an example of the swell processing treatment, PR (periodic reverse) electrolysis using a solution containing a high concentration of phosphoric acid, sulfuric acid or the like as an electrolytic bath can be mentioned. In PR electrolysis, copper is melted by an anodic reaction with a reverse current (negative current), so that an adhesive layer having a different electric resistance from that of the electrolytic bath is formed near the surface of the copper foil. When a forward current (positive current) is applied, the thickness of the adhesive layer becomes thinner at the convex part of the swell compared to the concave part of the swell, and the electrical resistance becomes smaller, so the plating current is selectively concentrated on the convex part. However, it is considered that a steep swell shape can be obtained.

Another example of the waviness processing is pulse electrolysis in which a reverse current pulse current is passed through a copper foil using a copper sulfate solution containing a polymer such as a water-soluble acrylic polymer, guar gum, or polyethylene oxide as an electrolytic bath. Be done. It is considered that the polymer adheres to the convex portion of the swell and then the pulse current of the reverse current having a high current density flows, so that the concave portion of the swell is selectively dissolved and a steep swell shape can be obtained.

<Roughening process>
For the purpose of improving the adhesion to the resin substrate, the surface of the electrolytic copper foil that has been subjected to the waviness processing treatment is roughened to obtain a roughened surface. By applying the roughening treatment to the surface of the electrolytic copper foil, the root mean square height Sq of the roughened surface of the surface-treated copper foil can be set in the above numerical range.
As an example of roughening treatment, a copper sulfate solution is added by nitrogen gas bubbling in a copper sulfate solution to which a metal such as cobalt (Co), iron (Fe), molybdenum (Mo), tin (Sn), or nickel (Ni) is added. There is a method of performing electroplating on the electrolytic copper foil while stirring the above. The type of metal added to the copper sulfate solution may be one type or two or more types.

When the roughening treatment is performed by electrolytic plating as described above, roughened particles are formed on the surface of the copper foil to form a roughened surface, but the roughened surface of the surface-treated copper foil is three or more roughened particles. May include aggregates that have aggregated. Since this agglomerate has a complicated shape, the presence of the agglomerate on the roughened surface further suppresses the diffusion of water at the interface between the surface-treated copper foil and the resin substrate, and the surface-treated copper in a high-temperature and high-humidity environment. The decrease in adhesion between the foil and the resin substrate is further suppressed. When the agglomerate is composed of three or more coarsened particles, the convex portion made of the agglomerate is higher than the periphery of the agglomerate, and the uneven shape of the roughened surface changes sharply. It is considered that the diffusion of water at the interface between the surface-treated copper foil and the resin substrate is further suppressed.

<Formation of nickel layer, zinc layer, chromate treatment layer>
In the surface-treated copper foil according to the present embodiment, a nickel layer and a zinc layer may be further formed in this order on the roughened surface formed by the roughening treatment.
The zinc layer prevents deterioration of the resin substrate and surface oxidation of the surface-treated copper foil due to the reaction between the surface-treated copper foil and the resin substrate when the surface-treated copper foil and the resin substrate are thermocompression-bonded. It also works to improve the adhesion between the surface-treated copper foil and the resin substrate. Further, the nickel layer prevents the zinc in the zinc layer from being thermally diffused into the surface-treated copper foil when the surface-treated copper foil and the resin substrate are thermocompression-bonded. That is, the nickel layer functions as a base layer of the zinc layer for effectively exerting the above-mentioned functions of the zinc layer.

These nickel layers and zinc layers can be formed by applying a known electrolytic plating method or electroless plating method. Further, the nickel layer may be formed of pure nickel or a phosphorus-containing nickel alloy.
Further, if a chromate treatment is further performed on the zinc layer, an antioxidant layer is formed on the surface of the surface-treated copper foil, which is preferable. As the chromate treatment to be applied, a known method can be used, and examples thereof include the method disclosed in Japanese Patent Application Laid-Open No. 60-86894. An excellent antioxidant function can be imparted to the surface-treated copper foil by adhering a chromium oxide of about 0.01 to 0.3 mg / dm ^{2 and its hydrate in terms of the amount of chromium.}

<Silane treatment>
The chromate-treated surface may be further subjected to surface treatment (silane treatment) using a silane coupling agent. By surface treatment using a silane coupling agent, a functional group having a strong affinity with an adhesive is imparted to the surface of the surface-treated copper foil (the surface on the joint side with the resin substrate), so that the surface-treated copper foil and the resin Adhesion with the manufacturing substrate is further improved, and rust resistance and moisture absorption and heat resistance of the surface-treated copper foil are further improved.

Various silane coupling agents can be used. For example, vinyl-based silanes, epoxy-based silanes, styryl-based silanes, methacryloxy-based silanes, acryloxy-based silanes, amino-based silanes, ureido-based silanes, chloropropyl-based silanes, Examples thereof include silane coupling agents such as mercapto-based silanes, sulfide-based silanes, and isocyanate-based silanes.

These silane coupling agents are usually used as an aqueous solution having a concentration of 0.001% by mass or more and 5% by mass or less. The silane treatment can be performed by applying this aqueous solution to the surface of the surface-treated copper foil and then heating and drying it. The same effect can be obtained by using a titanate-based or zirconate-based coupling agent instead of the silane coupling agent.

(3) Method for manufacturing copper-clad laminate and printed wiring board First, a surface-treated copper foil is placed on one or both surfaces of an electrically insulating resin substrate made of glass epoxy resin, polyimide resin, or the like. At that time, the roughened surface of the surface-treated copper foil is opposed to the resin substrate. Then, while heating the stacked resin substrates and surface-treated copper foil, pressure is applied in the stacking direction to join the resin substrate and surface-treated copper foil to obtain a copper-clad laminate with or without a carrier. Be done. Since the surface-treated copper foil according to the present embodiment has high tensile strength, it can be sufficiently supported without a carrier.

Next, the copper foil surface of the copper-clad laminate _{is irradiated with, for example, a CO 2} gas laser to make holes. That is, the surface of the copper foil on which the laser absorption layer is formed _{is irradiated with a CO 2} gas laser to perform a drilling process to form a through hole penetrating the surface-treated copper foil and the resin substrate. Then, if a circuit such as a high-density wiring circuit is formed on the surface-treated copper foil by a conventional method, a printed wiring board can be obtained.

〔Example〕
Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.
(A) Electrolytic Copper Foil A special electrolytic copper foil WS manufactured by Furukawa Electric Co., Ltd. was used as a raw material copper foil for producing the surface-treated copper foils of Examples 1 to 15 and Comparative Examples 1 to 5. The ten-point average roughness Rz of the drum surface of the electrolytic copper foil is 0.9 μm, and the ten-point average roughness Rz of the precipitated surface is 1.0 μm. These ten-point average roughness Rz are measured using a contact-type surface roughness measuring machine described later.

(B) Waviness processing First, the drum surface or the precipitation surface (see Table 1) of the electrolytic copper foil was subjected to a swell processing treatment. As the waviness processing treatment, PR electrolysis using an electrolytic bath containing copper sulfate and phosphoric acid, or pulse electrolysis using an electrolytic bath containing copper sulfate, sulfuric acid and a polymer was performed. In Comparative Examples 1 to 3, the electrolytic copper foil was not subjected to the waviness processing treatment, and the roughening treatment, which was the next step, proceeded as it was.

The concentrations of copper and phosphoric acid in the electrolysis bath of PR electrolysis are as shown in Table 1. Further, as the polymer in the electrolytic bath of pulse electrolysis, a water-soluble acrylic polymer (manufactured by Toa Synthetic Co., Ltd.), guar gum (manufactured by Sansho Co., Ltd.), or polyethylene oxide (manufactured by Sumitomo Seika Chemical Co., Ltd.) was used. The concentrations of copper, sulfuric acid, water-soluble acrylic polymer, guar gum, and polyethylene oxide in the electrolytic bath of pulse electrolysis are as shown in Table 1. Copper sulfate pentahydrate was added to the electrolysis bath for PR electrolysis and the electrolysis bath for pulse electrolysis, and Table 1 shows the concentration as metallic copper.

Table 1 shows the conditions of PR electrolysis and pulse electrolysis, that is, the surface (treated surface) subjected to the waviness processing treatment, the electrolysis conditions, the treatment time, and the temperature of the electrolytic bath. In the electrolytic conditions in Table 1, Ion1 represents the pulse current density of the first stage, Ion2 represents the pulse current density of the second stage, ton1 represents the pulse current application time of the first stage, and ton2 represents the second stage. Represents the pulse current application time of.

(C) Roughing Treatment Next, the surface of the electrolytic copper foil that had been subjected to the waviness processing was subjected to a roughening treatment with the surface as a roughened surface to produce a surface-treated copper foil. Specifically, the surface of the electrolytic copper foil was electroplated to electrodeposit fine copper particles as a roughening treatment to obtain a roughened surface in which fine irregularities were formed by the copper particles. The plating solution used for electroplating contains cobalt or iron together with copper sulfate and sulfuric acid, and the copper concentration, sulfuric acid concentration, cobalt concentration, and iron concentration are as shown in Table 2. Although copper sulfate pentahydrate was added to the plating solution, Table 2 shows the concentration as metallic copper.
Table 2 shows the conditions of electroplating, that is, the surface (treated surface) subjected to the roughening treatment, the current density I, the treatment time, the temperature of the plating bath, and the presence or absence of nitrogen gas bubbling in the plating bath.

(D) Formation of Nickel Layer (Underground Layer) Next, by electroplating the roughened surface of the surface-treated copper foil under the Ni plating conditions shown below, the nickel layer (Ni adhesion amount 0.33 mg / dm). ² ) was formed. The plating solution used for nickel plating contains nickel sulfate, ammonium persulfate ((NH ₄ ) ₂ S ₂ O ₈ ), and boric acid (H ₃ BO ₃ ), and has a nickel concentration of 7.5 g / L and ammonium persulfate. The concentration is 40.0 g / L and the boric acid concentration is 19.5 g / L. The temperature of the plating solution is 28.5 ° C., the pH is 3.8, the current density is 1.8 A / dm ² , and the plating treatment time is 1 second to 2 minutes.

(E) Formation of Zinc Layer (Heat Resistant Treatment Layer) Further, a zinc layer (Zn adhesion amount 0.10 mg / dm ² ) was formed by electroplating on the nickel layer under the Zn plating conditions shown below. The plating solution used for zinc plating contains zinc sulfate heptahydrate and sodium hydroxide, and has a zinc concentration of 1 to 30 g / L and a sodium hydroxide concentration of 25 to 220 g / L. The temperature of the plating solution is 5 to 60 ° C., the current density is 0.1 to 10 A / dm ² , and the plating treatment time is 1 second to 2 minutes.

(F) Formation of Chromate Treatment Layer (Rust Prevention Treatment Layer) Further, by electrolytic plating on the zinc layer under the Cr plating conditions shown below, a chromate treatment layer (Cr adhesion amount 0.03 mg / dm ² ) is formed. Formed. The plating solution used for chromium plating contains chromic anhydride (CrO ₃ ) and has a chromium concentration of 2.2 g / L. The temperature of the plating solution is 15 to 45 ° C., the pH is 2.5, the current density is 0.3 A / dm ² , and the plating treatment time is 1 second to 2 minutes.

(G) Formation of silane coupling agent layer Further, the following treatment was carried out to form a silane coupling agent layer on the chromate-treated layer. That is, methanol or ethanol was added to the aqueous solution of the silane coupling agent to adjust the pH to a predetermined pH to obtain a treatment liquid. This treatment liquid was applied to the chromate treatment layer of the surface-treated copper foil, held for a predetermined time, and then dried with warm air to form a silane coupling agent layer.

(H) Evaluation As described above, the surface-treated copper foils of Examples 1 to 15 and Comparative Examples 1 to 5 were produced, respectively. The foil thickness of these surface-treated copper foils is as shown in Table 3. Various evaluations were performed on each of the obtained surface-treated copper foils.

[Etching factor]
A resist pattern having an L & S of 30/30 μm was formed on the surface-treated copper foils of Examples 1 to 15 and Comparative Examples 1 to 5 obtained as described above by a subtractive method. Then, etching was performed to form a wiring pattern. A dry resist film was used as the resist, and a mixed solution containing copper chloride and hydrochloric acid was used as the etching solution. Then, the etching factor (Ef) of the obtained wiring pattern was measured.

The etching factor is a value represented by the following equation when the foil thickness of the copper foil is H, the bottom width of the formed wiring pattern is B, and the top width of the formed wiring pattern is T.
Ef = 2H / (BT)
In this example and the comparative example, those having an etching factor of 2.5 or more were regarded as non-defective products, and those having an etching factor of less than 2.5 were regarded as defective products.

If the etching factor is small, the verticality of the side wall in the wiring pattern will be lost, and in the case of a fine wiring pattern with a narrow line width, there is a risk of short-circuiting or disconnection due to undissolved copper foil between adjacent wiring patterns. There is a risk of tying. In this test, the bottom width B and top width T are measured with a microscope for the wiring pattern when the just etch position (the position of the end of the resist and the position of the bottom of the wiring pattern are aligned), and the etching factor. Was calculated. The results are shown in Table 3.

[Adhesion under normal conditions]
A resin substrate was joined to the roughened surface of the surface-treated copper foil to obtain a copper-clad laminate. As the resin substrate, EI-6765 manufactured by Sumitomo Bakelite Co., Ltd., which is a commercially available FR4 (Flame Retardant Type 4) resin, was used, and the curing temperature at the time of joining was 170 ° C., and the curing time was 2 hours.
The surface-treated copper foil of the produced copper-clad laminate was etched to form a circuit wiring having a width of 1 mm to obtain a printed wiring board, and this printed wiring board was used as a sample for measuring adhesion.

Next, the resin substrate side of the measurement sample was fixed to a stainless steel plate with double-sided tape, and the circuit wiring was pulled in the 90 degree direction at a speed of 50 mm / min to peel off, and the adhesion (kN / m) was measured. The measurement was performed 5 times, and the average value of the obtained 5 measured values was taken as the adhesion under normal conditions. The adhesion was measured using a universal material testing machine (Tencilon manufactured by A & D Co., Ltd.). In this example and the comparative example, the case where the adhesion under the normal condition was 0.6 kN / m or more was regarded as a good product, and the case where the adhesion was less than 0.6 kN / m was regarded as a defective product. The results are shown in Table 3.

[Adhesion in high temperature and high humidity environment]
Adhesion in a high temperature and high humidity environment was measured using a measurement sample similar to the above measurement sample used in the measurement of adhesion under normal conditions. First, using a pressure cooker tester, the measurement sample was held in an environment of a temperature of 121 ° C., a humidity of 100% RH, and an atmospheric pressure of 2 atm for 48 hours to perform PCT. Next, the adhesion (kN / m) of the measurement sample after PCT was measured in the same manner as the measurement of the adhesion in the normal state. The measurement was performed 5 times, and the average value of the obtained 5 measured values was taken as the adhesion after PCT. In this example and the comparative example, the case where the adhesion after PCT was 0.2 kN / m or more was regarded as a good product, and the case where it was less than 0.2 kN / m was regarded as a defective product. The results are shown in Table 3.

[Measurement of minimum autocorrelation length Sal, root mean square height Sq]
Using BRUKER's three-dimensional white light interference type microscope Wyko Contour GT-K, the surface shape of the roughened surface of the surface-treated copper foils of Examples 1 to 15 and Comparative Examples 1 to 5 was measured and shape analysis was performed. , The minimum autocorrelation length Sal and the root mean square height Sq were determined. The surface shape was measured at any 5 points on each surface-treated copper foil, and shape analysis was performed at each of the 5 points to obtain the minimum autocorrelation length Sal and the root mean square height Sq at each of the 5 points. Then, the average value of the obtained results at the five locations was taken as the minimum autocorrelation length Sal and the root mean square height Sq of each surface-treated copper foil.

The shape analysis was performed by a VSI measurement method (vertical scanning interferometry) using a high resolution CCD camera. The conditions are that the light source is white light, the measurement magnification is 10 times, the measurement range is 477 μm × 357.8 μm, the Lateral Sample is 0.38 μm, the speed is 1, the Backscan is 10 μm, the Length is 10 μm, the Threat is 3%, and the Term Statistic. (Cylinder and Tilt), Data Restore (Measurement: legacy, iterations 5), Static Filter (Filter Size: 3, Filter Type: Median), Fourier Filter (High Filter) Data processing was performed after filtering 12.5 mm ^-1). The results are shown in Table 3.

[Measurement of 10-point average roughness Rz]
For the roughened surfaces of the surface-treated copper foils of Examples 1 to 15 and Comparative Examples 1 to 5, the ten-point average roughness Rz (μm) was measured according to the provisions of JIS B 0601: 1994. The measurement was performed at any five points for each surface-treated copper foil, and the average value thereof was taken as a ten-point average roughness Rz. Further, as a measuring device, a contact type surface roughness measuring machine surf coder SE1700 manufactured by Kosaka Laboratory Co., Ltd. was used. The measurement conditions were a measurement length of 4.8 mm, a sampling length of 4.8 mm, and a cutoff value of 0.8 mm. The results are shown in Table 3.

[Aggregate]
Using a scanning electron microscope, SEM images of the roughened surfaces of the surface-treated copper foils of Examples 1 to 15 and Comparative Examples 1 to 5 were photographed in three fields (length 13.9 μm, width 18.6 μm) at a magnification of 5000 times. Then, it was confirmed whether or not there was an agglomerate in which three or more of the roughened particles were aggregated. The results are shown in Table 3.

As can be seen from Table 3, the surface-treated copper foils of Examples 1 to 15 have a large etching factor (Ef) and have fine wiring workability, as well as adhesion under normal conditions and after PCT. The adhesion was excellent.

101 Electrolyzed copper foil 102 Cathode drum 104 Insoluble anode 105 Electrolyzed solution

Claims (8)

A surface-treated copper foil having a roughened surface on its surface, the minimum autocorrelation length Sal of the roughened surface is 1.0 μm or more and 8.5 μm or less, and the root mean square height Sq is 0. . Surface-treated copper foil of 10 μm or more and 0.98 μm or less. The surface-treated copper foil according to claim 1, wherein the roughened surface is formed on a drum surface of the electrolytic copper foil. The first or second aspect of the present invention, wherein the minimum autocorrelation length Sal of the roughened surface is 1.3 μm or more and 6.5 μm or less, and the root mean square height Sq is 0.21 μm or more and 0.72 μm or less. Surface treated copper foil. Any one of claims 1 to 3 in which the minimum autocorrelation length Sal of the roughened surface is 1.7 μm or more and 5.7 μm or less, and the root mean square height Sq is 0.28 μm or more and 0.54 μm or less. The surface-treated copper foil described in. The surface-treated copper foil according to any one of claims 1 to 4, wherein the roughened surface includes an agglomerate in which three or more of the roughened particles are agglomerated. The surface-treated copper according to any one of claims 1 to 5, wherein the ten-point average roughness Rz of the roughened surface measured using a contact-type surface roughness measuring machine is 1.2 μm or more and 3.8 μm or less. Foil. A copper-clad laminate comprising the surface-treated copper foil according to any one of claims 1 to 6 and a resin substrate laminated on the roughened surface of the surface-treated copper foil. A printed wiring board including the copper-clad laminate according to claim 7.

Images