KR102638749B1 - Surface treated copper foil, copper clad laminate and printed wiring board - Google Patents

Abstract

A surface-treated copper foil having fine wiring processability and excellent adhesion to a resin substrate is provided. A surface-treated copper foil having a roughened surface on the surface through roughening treatment, wherein 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 0.10 μm or more and 0.98 μm or less.

Description

Surface treated copper foil, copper clad laminate and printed wiring board

The present invention provides a surface-treated copper foil excellent in fine wiring processability and adhesion to a resin substrate suitable for printed wiring boards (particularly printed wiring boards with high-density wiring circuits (fine patterns)), and a copper-clad laminate using the surface-treated copper foil. and printed wiring boards.

As copper foil used for copper-clad laminates and printed wiring boards, electrolytic copper foil obtained by peeling the copper foil deposited on the drum of an electrolytic deposition device from the drum is used. The electric field deposition start surface (hereinafter referred to as “drum surface”) of the electrolytic copper foil peeled from the drum is relatively smooth, and the opposite side, the electrolytic deposition end surface (hereinafter referred to as “precipitation surface”), is generally uneven. has. A copper-clad laminate is manufactured by placing a resin substrate on the deposited surface of the electrolytic copper foil and heat-pressing it, but generally, the deposited surface is roughened and roughened to improve adhesion to the resin substrate.

Recently, an adhesive resin such as an epoxy resin is previously adhered to the roughened surface of copper foil, and the resin-coated copper foil, which uses the adhesive resin as an insulating resin layer in a semi-cured state (B stage), is used as a copper foil for forming a surface circuit. Therefore, the side of the insulating resin layer is thermocompressed to an insulating substrate to manufacture a printed wiring board (particularly a build-up wiring board). In build-up wiring boards, it is desired to highly integrate various electronic components, and correspondingly, higher density wiring patterns are required, and wiring patterns with fine line widths and line pitches, so-called fine pattern printed wiring boards, are required. For example, in multilayer boards used in servers, routers, communication base stations, vehicle-mounted boards, etc., and multilayer boards for smart phones, printed wiring boards with high-density ultra-fine wiring (hereinafter referred to as “high-density wiring boards”) are required.

High-density wiring boards of AnyLayer (connecting layers with laser vias with a high degree of freedom of arrangement) are mainly used in smartphone motherboards, but in recent years, finer wiring has progressed, and line widths and pitches between lines (hereinafter referred to as “L&S”) are used. For example, wiring of 30㎛ or less is required.

However, as wiring becomes finer, the problem of moisture absorption deterioration, in which the adhesion between the wiring and the resin decreases due to the influence of moisture absorbed in the resin of a high-density wiring board, is becoming more present. In particular, in recent smart phones, moisture absorption deterioration tends to accelerate due to an increase in heat generation accompanying an increase in power consumption, making it difficult to maintain adhesion between wiring and resin.

Patent Document 1 discloses a copper foil that has excellent adhesion to a high heat-resistant resin by sharpening the shape of the roughened particles, but the roughened particles of the sharpened shape do not melt and tend to remain behind during etching for forming wiring (roots remain). , there was a risk that fine wiring processability would become insufficient.

Patent Document 2 discloses a copper foil with small drum surface roughness and excellent fine wiring processability, but since no measures are taken to prevent moisture absorbed by the resin substrate, the adhesion between the copper foil and the resin substrate is poor in a high temperature and high humidity environment. There was concern that this would deteriorate.

Patent Document 3 discloses a copper foil excellent in high-frequency characteristics that controls the sharpness of the change in the uneven shape of the surface. However, when L&S each produce a high-density wiring board with fine wiring of, for example, 30 μm or less, There was a risk that the adhesion between the copper foil and the resin substrate under a high temperature and high humidity environment would decrease.

Japanese Patent Laid-open Publication No. 236058, 2010 Japanese Patent Laid-open Publication No. 76601, 2018 International Publication No. 2018/198905

The object of the present invention is to provide a surface-treated copper foil that has fine wiring processability and is excellent in 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 ultra-fine wiring.

The surface-treated copper foil according to one embodiment of the present invention is a surface-treated copper foil having a roughened surface by roughening treatment on the 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 The point is that is 0.10㎛ or more and 0.98㎛ or less.

In addition, the main point of the copper-clad laminate according to another embodiment of the present invention is to include the surface-treated copper foil according to the above-described embodiment, and a resin substrate laminated on the roughened surface of the surface-treated copper foil.

In addition, the main point of the printed wiring board according to another embodiment of the present invention is to include the copper clad laminate according to the above other embodiment.

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

1 is a diagram illustrating a method of manufacturing electrolytic copper foil using an electrolytic deposition device.

(Form for carrying out the invention)

One embodiment of the present invention will be described. In addition, the embodiment described below shows an example of the present invention. In addition, various changes or improvements can be made to this embodiment, and forms to which such changes or improvements are added can also be included in the present invention.

The surface-treated copper foil according to one embodiment of the present invention is a surface-treated copper foil having a roughened surface by roughening treatment on the 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 0.10㎛ or more and 0.98㎛ or less.

From this configuration, the surface-treated copper foil of the present embodiment has fine wiring processability capable of supporting high-density wiring boards, and also has adhesion to a resin substrate in a normal state and under a high temperature and high humidity environment (for example, after a pressure cooker test). ) has excellent adhesion. Therefore, the surface-treated copper foil according to this embodiment can be suitably used for manufacturing copper-clad laminates and printed wiring boards. Using the surface-treated copper foil of this embodiment, a copper-clad laminate having fine wiring processability can be manufactured. Moreover, if the surface-treated copper foil of this embodiment is used, a printed wiring board with high-density ultrafine wiring can be manufactured. In addition, in this invention, a "normal state" means the state in which the surface-treated copper foil is placed at normal temperature and humidity (for example, temperature 23±2 degreeC, humidity 50±5%RH).

The minimum autocorrelation length Sal is a value specified in ISO 25178, and is the shortest distance within the surface at which the autocorrelation function of the surface shape (see Equation 1 below) attenuates to the correlation value s (unless otherwise specified, s is 1). It is defined as the shortest attenuation distance from 0.2 to 0.2) and can be measured, for example, by a three-dimensional white light interference microscope or laser microscope. In 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 curvature of the surface of the copper foil, etc. In other words, the smaller the value of the minimum autocorrelation length Sal, the lower the elevation difference changes over a shorter distance, so it can be said that the change in the uneven shape of the surface is steeper.

The root mean square height Sq is a value specified in ISO 25178, and is defined as the standard deviation of the distance from the average plane as shown in Equation 2 below, and is measured by, for example, a three-dimensional white light interference microscope or a laser microscope. can do. The root mean square height Sq represents the unevenness of the surface shape caused by a rough shape or the like in copper foil. Additionally, z(x, y) in equations 1 and 2 represents the height direction coordinates in the x and y coordinates.

Below, the surface-treated copper foil of this embodiment is explained in more detail.

As a result of intensive study, the present inventors have found that the moisture absorption phenomenon under 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 the interface between the copper foil and the resin substrate. There are two types of moisture absorption from, and it was discovered that moisture absorption from the interface between the copper foil and the resin substrate has a large contribution to the decrease in adhesion between the resin substrate and the copper foil after PCT. When moisture enters the interface between the copper foil and the resin substrate, chemical components that enhance adhesion, such as coupling agents, are hydrolyzed, or an oxide film grows on the surface of the copper foil under the influence of moisture, causing the interface between the copper foil and the resin substrate. It is thought that the bonding strength decreases and the adhesion between the copper foil and the resin substrate decreases.

Since the roughened surface of the surface-treated copper foil with a minimum autocorrelation length Sal of 1.0 μm or more and 8.5 μm or less has an appropriately steep change in curvature, the diffusion rate of moisture at the interface between the surface-treated copper foil and the resin substrate becomes slow. Therefore, since the interface between the surface-treated copper foil and the resin substrate is maintained normally even under a high temperature and high humidity environment (for example, after PCT), the adhesion between the surface-treated copper foil and the resin substrate is likely to be maintained in a high state.

If the minimum autocorrelation length Sal of the roughened surface of the surface-treated copper foil exceeds 8.5 μm, the curvature is gentle, so the diffusion rate of moisture at the interface between the surface-treated copper foil and the resin substrate is high, and the surface-treated copper foil is There is a risk that the adhesion to 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 curvature changes excessively sharply, so a gap is likely to form at the interface between the surface-treated copper foil and the resin substrate. Then, in a high-temperature, high-humidity environment, moisture tends to collect in the gap, so there is a risk that the adhesion between the surface-treated copper foil and the resin substrate may decrease.

In addition, in a high-density wiring board, in order to achieve both adhesion and fine wiring processability between the surface-treated copper foil and the resin substrate in a high-temperature, high-humidity environment, it is necessary to control the roughness of the fine irregularities as well as the curved shape of the roughened surface of the surface-treated copper foil.

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 adhesion between the surface-treated copper foil and the resin substrate in a high temperature and high humidity environment and fine wiring processability are achieved at a high level.

In the surface-treated copper foil whose roughened surface root mean square height Sq is 0.10 ㎛ or more and 0.98 ㎛ or less, the height of fine irregularities is appropriately adjusted, so the surface-treated copper foil is stably dissolved when forming wiring by etching, and the etching factor It is easy to obtain a high-value pattern (that is, the cross-sectional shape of the wiring is likely to be close to a rectangle).

If the root mean square height Sq of the roughened surface of the surface-treated copper foil exceeds 0.98 μm, locally high convex portions of the surface-treated copper foil remain without dissolving on the resin substrate during the formation of wiring by etching (i.e., roots remain). If this happens), there is a risk that 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, and there is a risk that the adhesion between the surface-treated copper foil and the resin substrate under normal conditions and in a high temperature and high humidity environment may decrease.

Additionally, 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. In addition, 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.

In addition, the 10-point average roughness Rz of the roughened surface measured using a contact-type surface roughness measuring device is preferably 1.2 μm or more and 3.8 μm or less. If the 10-point average roughness Rz of the roughened surface is within the above range, the effect of improving adhesion in a normal state is obtained due to the anchor effect.

In addition, the surface-treated copper foil of this embodiment can be manufactured by roughening the surface of the electrolytic copper foil to make it a roughened surface. However, the surface on which the roughening treatment is performed may be a drum surface or a precipitated surface. For example, when roughening is applied to the drum surface of the electrolytic copper foil, a roughened surface is formed on the drum surface of the electrolytic copper foil.

Below, the surface-treated copper foil according to this embodiment is explained in more detail. First, an example of a method for manufacturing surface-treated copper foil will be described.

(1) About the manufacturing method of electrolytic copper foil

Electrolytic copper foil can be manufactured using, for example, an electrolytic precipitation device as shown in FIG. 1. The electrolytic deposition device in FIG. 1 includes an insoluble anode 104 made of titanium coated with a platinum group element or its oxide, a cathode drum 102 made of titanium formed opposite the insoluble anode 104, and a cathode drum 102. It is equipped with a buff 103 that polishes and removes the oxide film formed on the surface of the cathode drum 102.

An electrolyte solution 105 (sulfuric acid-copper sulfate aqueous solution) is supplied between the cathode drum 102 and the insoluble anode 104, and while rotating the cathode drum 102 at a constant speed, the cathode drum 102 and the insoluble anode 104 are connected to each other. ), a direct current is passed between the Accordingly, copper is deposited on the surface of the cathode drum 102. The electrolytic copper foil 101 is obtained by peeling off the precipitated copper from the surface of the cathode drum 102 and continuously winding it.

In manufacturing electrolytic copper foil, additives may be added to the electrolyte solution 105. Various additives can be used; examples include ethylene thiourea, polyethylene glycol, tetramethyl thiourea, and polyacrylamide. Here, by increasing the addition amount of ethylenethiourea and tetramethylthiourea, the tensile strength of the electrolytic copper foil in the normal state and the tensile strength of the electrolytic copper foil measured at room temperature after heating at 220 ° C. for 2 hours can be improved. .

Additionally, molybdenum may be added to the electrolyte solution 105. By adding molybdenum, the etching properties of copper foil can be improved. Normally, in electrolytic precipitation, the copper concentration of the electrolyte solution 105 (concentration of copper alone, excluding the sulfuric acid content among copper sulfate) is 13 to 72 g/L, the sulfuric acid concentration of the electrolyte solution 105 is 26 to 133 g/L, and the electrolyte solution is 13 to 72 g/L. 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 to 1 minute and 55 seconds.

(2) About surface treatment of electrolytic copper foil

<Bending processing>

The bending process is a process performed to adjust the minimum autocorrelation length Sal and root mean square height Sq of the surface of the copper foil. In order to make 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 curved shape of the surface of the electrolytic copper foil by bending processing.

An example of bending processing includes PR (periodic reverse) electrolysis using a solution containing a high concentration of phosphoric acid, sulfuric acid, etc. as an electrolytic bath. In PR electrolysis, copper is dissolved by an anode reaction with a reverse current (negative current), thereby forming an adhesive layer having a different electrical resistance from that of the electrolytic bath near the surface of the copper foil. When a net current (positive current) is passed, the thickness of the adhesive layer becomes thinner and the electrical resistance decreases in the convex part of the curve compared to the concave part of the curve, so the plating current is selectively concentrated in the convex part, forming a sharp bend. I think the shape is obtained.

In addition, as another example of bending processing, a copper sulfate solution to which polymers such as water-soluble acrylic polymer, guar gum, and polyethylene oxide are added is used as an electrolytic bath, and pulse electrolysis is used to pass a reverse pulse current through the copper foil. . It is believed that after the polymer adheres to the convex portion of the curve, a pulse current of a high current density reverse current flows, thereby selectively dissolving the concave portion of the curve, thereby obtaining a sharply curved shape.

<Harmonization processing>

For the purpose of improving adhesion to the resin substrate, the surface of the electrolytic copper foil subjected to bending processing is subjected to roughening treatment to obtain a roughened surface. By roughening 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 adjusted to the above numerical range.

As an example of roughening treatment, a copper sulfate solution containing metals such as cobalt (Co), iron (Fe), molybdenum (Mo), tin (Sn), and nickel (Ni) is prepared by bubbling nitrogen gas. A method of performing electrolytic plating on electrolytic copper foil while stirring is included. There may be one type of metal added to the copper sulfate solution, or two or more types may be used.

When roughening treatment is performed by electrolytic plating as described above, roughening particles are formed on the surface of the copper foil to form a roughened surface. The roughened surface of the surface-treated copper foil may include an aggregate of three or more roughened particles agglomerated. Since this aggregate has a complex shape, if the aggregate is present on the roughened surface, the diffusion of moisture at the interface between the surface-treated copper foil and the resin substrate is further suppressed, and the diffusion of moisture at the interface between the surface-treated copper foil and the resin substrate in a high temperature and high humidity environment is prevented. The decline in adhesion is further suppressed. If the aggregate is composed of three or more roughened particles, the convex portions made of the aggregate are higher than the surroundings of the aggregate, and the change in the uneven shape of the roughened surface becomes steep, so that at the interface between the surface-treated copper foil and the resin substrate It is thought that the diffusion of moisture is further suppressed.

<Formation of nickel layer, zinc layer, and chromate treatment layer>

In the surface-treated copper foil according to this 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 due to a reaction between the surface-treated copper foil and the resin substrate and surface oxidation of the surface-treated copper foil when the surface-treated copper foil and the resin substrate are thermocompressed. It has the effect of increasing adhesion to the resin substrate. Additionally, the nickel layer prevents the zinc in the zinc layer from thermally diffusing into the surface-treated copper foil when the surface-treated copper foil and the resin substrate are thermocompressed. In other words, the nickel layer functions as a base layer for the zinc layer to effectively exhibit the above-mentioned function of the zinc layer.

Additionally, these nickel layers and zinc layers can be formed by applying a known electrolytic plating method or an electroless plating method. Additionally, the nickel layer may be formed of pure nickel or may be formed of a phosphorus-containing nickel alloy.

Additionally, additional chromate treatment on the zinc layer is preferable because an anti-oxidation layer is formed on the surface of the surface-treated copper foil. As the chromate treatment to be applied, a known method can be used, for example, the method disclosed in Japanese Patent Application Laid-Open No. 60-86894. By attaching chromium oxide and its hydrate in an amount of about 0.01 to 0.3 mg/dm ² in terms of the amount of chromium, the surface-treated copper foil can be given an excellent anti-oxidation function.

<Silane treatment>

The chromate-treated surface may be further subjected to surface treatment (silane treatment) using a silane coupling agent. Because surface treatment using a silane coupling agent imparts a functional group with strong affinity to the adhesive to the surface of the surface-treated copper foil (the surface on the bonding side with the resin substrate), the adhesion between the surface-treated copper foil and the resin substrate is improved. It also improves the rust prevention and moisture absorption heat resistance of the surface-treated copper foil.

Various silane coupling agents can be used, for example, vinyl silane, epoxy silane, styryl silane, methacryloxy silane, acryloxy silane, amino silane, ureide silane, and chloropropyl silane. Silane coupling agents such as silane, mercapto-based silane, sulfide-based silane, and isocyanate-based silane can be mentioned.

These silane coupling agents are usually used as aqueous solutions at a concentration of 0.001% by mass or more and 5% by mass or less. 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. Additionally, the same effect can be obtained by using a titanate-based or zirconate-based coupling agent instead of a silane coupling agent.

(3) About manufacturing methods of copper clad laminates and printed wiring boards

First, surface-treated copper foil is placed on one or both surfaces of an electrically insulating resin substrate made of glass epoxy resin, polyimide resin, etc. In that case, the roughened surface of the surface-treated copper foil is opposed to the resin substrate. Then, while heating the overlapping resin substrate and surface-treated copper foil, pressure in the lamination direction is applied to bond the resin substrate and surface-treated copper foil, thereby obtaining a copper-clad laminate with or without a carrier. Since the surface-treated copper foil according to this embodiment has high tensile strength, it can sufficiently cope even 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, a CO ₂ gas laser is irradiated to the surface of the copper foil on which the laser absorption layer is formed, and hole drilling processing is performed 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]

Examples and comparative examples are given below to illustrate the present invention in more detail.

(A) Electrolytic copper foil

As a raw material copper foil for manufacturing the surface-treated copper foil of Examples 1 to 15 and Comparative Examples 1 to 5, special electrolytic copper foil WS manufactured by Furukawa Electric Co., Ltd. was used. The 10-point average roughness Rz of the drum surface of this electrolytic copper foil is 0.9 μm, and the 10-point average roughness Rz of the precipitated surface is 1.0 μm. These 10-point average roughness Rz was measured using a contact-type surface roughness measuring device described later.

(B) Bending processing

First, bending processing was performed on the drum surface or precipitated surface (see Table 1) of the electrolytic copper foil. As the bending 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 addition, for Comparative Examples 1 to 3, bending processing was not performed on the electrolytic copper foil, and the roughening treatment, which was the next step, was carried out as is.

The concentrations of copper and phosphoric acid in the electrolytic bath of PR electrolysis are as shown in Table 1. In addition, as the polymer in the electrolytic bath of pulse electrolysis, water-soluble acrylic polymer (manufactured by Toagosei Co., Ltd.), guar gum (manufactured by Sansho Co., Ltd.), or polyethylene oxide (manufactured by Sumitomo Seika 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. In addition, copper sulfate pentahydrate was added to the electrolytic bath of PR electrolysis and the electrolytic bath of pulse electrolysis, and the concentration as metallic copper is shown in Table 1.

Table 1 shows the conditions of PR electrolysis and pulse electrolysis, that is, the surface on which the bending treatment was performed (treated surface), electrolysis conditions, treatment time, and electrolytic bath temperature. In the electrolysis conditions in Table 1, Ion1 represents the first-stage pulse current density, Ion2 represents the second-stage pulse current density, ton1 represents the first-stage pulse current application time, and ton2 represents the second-stage pulse current density. It represents the pulse current application time.

(C) Harmonization processing

Next, a roughening treatment was performed on the surface of the electrolytic copper foil on which the bending treatment was performed to make the surface a roughened surface, and a surface-treated copper foil was manufactured. Specifically, electroplating to deposit fine copper particles on the surface of the electrolytic copper foil was performed as a roughening treatment to obtain a roughened surface with fine irregularities formed by the copper particles. The plating solution used for electroplating contains cobalt or iron along with copper sulfate and sulfuric acid, and the copper concentration, sulfuric acid concentration, cobalt concentration, and iron concentration are as shown in Table 2. Additionally, copper sulfate pentahydrate was added to the plating solution, but the concentration as metallic copper is shown in Table 2.

Table 2 shows the conditions of electroplating, that is, the surface on which the roughening treatment was performed (treated surface), current density I, treatment time, temperature of the plating bath, and presence or absence of nitrogen gas bubbling in the plating bath.

(D) Formation of nickel layer (base layer)

Next, a nickel layer (Ni adhesion amount of 0.33 mg/dm ² ) was formed by electrolytic plating on the roughened surface of the surface-treated copper foil under the Ni plating conditions shown below. 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 the nickel concentration is 7.5 g/L and the ammonium persulfate concentration is 7.5 g/L. 40.0g/L, boric acid concentration is 19.5g/L. Additionally, the temperature of the plating solution was 28.5°C, the pH was 3.8, the current density was 1.8 A/dm ² , and the plating treatment time was 1 second to 2 minutes.

(E) Formation of zinc layer (heat-resistant treatment layer)

Additionally, a zinc layer (Zn adhesion amount of 0.10 mg/dm ² ) was formed on the nickel layer by electrolytic plating under the Zn plating conditions shown below. The plating solution used for zinc plating contains zinc sulfate heptahydrate and sodium hydroxide, and the zinc concentration is 1 to 30 g/L and the sodium hydroxide concentration is 25 to 220 g/L. Additionally, 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)

Additionally, a chromate-treated layer (Cr adhesion amount of 0.03 mg/dm ² ) was formed on the zinc layer by electrolytic plating under the Cr plating conditions shown below. The plating solution used for chrome plating contains chromic anhydride (CrO ₃ ), and the chromium concentration is 2.2 g/L. Additionally, 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

Additionally, the treatment shown below was performed to form a silane coupling agent layer on the chromate-treated layer. That is, methanol or ethanol was added to the silane coupling agent aqueous solution, the pH was adjusted to a predetermined level, and a treatment solution was obtained. This treatment liquid was applied to the chromate-treated layer of the surface-treated copper foil, kept for a predetermined period of time, and then dried with warm air to form a silane coupling agent layer.

(H) Evaluation

As described above, 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 obtained surface-treated copper foil.

[Etching factor]

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

The etching factor is a value expressed by the following equation when the copper foil thickness 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/(B-T)

In this Example and Comparative Example, products with an etching factor of 2.5 or more were considered good products, and products with an etching factor of less than 2.5 were considered defective products.

If the etching factor is small, the verticality of the side walls in the wiring pattern is broken, and in the case of fine wiring patterns with narrow line widths, undissolved copper foil remains between adjacent wiring patterns, creating a risk of short circuit or disconnection. There is a risk of being connected. In this test, the bottom width B and top width T of the wiring pattern when it is just at the etching position (the position of the end of the resist and the bottom of the wiring pattern are aligned) are measured with a microscope, and the etching factor is determined. calculated. The results are shown in Table 3.

[Adhesion in normal conditions]

A resin substrate was bonded to the roughened surface of the surface-treated copper foil to obtain a copper-clad laminate. As a resin substrate, EI-6765 manufactured by Sumitomo Bakelite Co., Ltd., a commercially available FR4 (Flame Retardant Type 4) resin, was used. The curing temperature during bonding was 170°C, and the curing time was 2 hours. .

Surface treatment of the produced copper clad laminate The copper foil was etched to form a circuit wiring with a width of 1 mm to form a printed wiring board, and this printed wiring board was used as a sample for measuring adhesion.

Next, the resin substrate side of the sample for measurement was fixed to a stainless steel plate with double-sided tape, the circuit wiring was pulled and peeled in a 90-degree direction at a speed of 50 mm/min, and the adhesion (kN/m) was measured. . The measurement was performed five times, and the average value of the five obtained measurement values was taken as the adhesion in the normal state. Adhesion was measured using a universal material tester (Tensilon, manufactured by A&D Co., Ltd.). In this Example and Comparative Example, cases where the adhesion under normal conditions was 0.6 kN/m or more were considered good products, and cases where adhesion was less than 0.6 kN/m were considered defective products. The results are shown in Table 3.

[Adhesion under high temperature and high humidity environments]

Adhesion was measured in a high-temperature, high-humidity environment using the same measurement sample as the measurement sample used in the measurement of adhesion in normal conditions. First, using a pressure cooker tester, the sample for measurement was stored for 48 hours in an environment with a temperature of 121°C, a humidity of 100% RH, and an atmospheric pressure of 2 atm, and PCT was performed. Next, the adhesion (kN/m) of the measurement sample after PCT was measured in the same manner as the measurement of adhesion in a normal state. The measurement was performed 5 times, and the average value of the 5 obtained measurement values was taken as the adhesion after PCT. In this Example and Comparative Example, cases where the adhesion after PCT was 0.2 kN/m or more were considered good products, and cases where the adhesion was less than 0.2 kN/m were considered defective products. 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 microscope Wyko ContourGT-K, the surface shape of the roughened surface of the surface-treated copper foil of Examples 1 to 15 and Comparative Examples 1 to 5 was measured, shape analysis was performed, and the minimum autocorrelation length was determined. Sal and root mean square height Sq were obtained. The surface shape was measured at five arbitrary locations on each surface-treated copper foil, shape analysis was performed at each of the five locations, and the minimum autocorrelation length Sal and root mean square height Sq were determined at each of the five locations. And the average value of the five obtained results was set as the minimum autocorrelation length Sal and root mean square height Sq of each surface-treated copper foil.

Shape analysis was performed by VSI measurement (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㎛ Removal(Cylinder and Tilt), Data Restore(Method: legacy, iterations 5), Statistic Filter(Filter Size: 3, Filter Type: Median), Fourier Filter(High Freq Pass, Fourier Filter Window: Gaussian, Frequency Cutoff: High Cutoff = 12.5 mm ^-1 ) and then data processing was performed. The results are shown in Table 3.

[Measurement of 10-point average roughness Rz]

About the roughened surface of the surface-treated copper foil of Examples 1 to 15 and Comparative Examples 1 to 5, the 10-point average roughness Rz (μm) was measured according to the provisions of JIS B 0601:1994. The measurement was performed at five arbitrary locations on each surface-treated copper foil, and their average value was taken as the 10-point average roughness Rz. In addition, as a measuring device, a contact type surface roughness measuring instrument Surf Corda SE1700 manufactured by Kosaka Kenkyusho 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.

[Agglomerates]

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 taken at a magnification of 5000 times in 3 fields (13.9 ㎛ vertically, 18.6 ㎛ horizontally), and the roughened particles were captured. It was confirmed whether three or more aggregates existed. The results are shown in Table 3.

As can be seen from Table 3, the surface-treated copper foils of Examples 1 to 15 had a large etching factor (Ef), had fine wiring processability, and were excellent in adhesion in a normal state and in adhesion after PCT.

101: Electrolytic copper foil
102: cathode drum
104: insoluble anode
105: electrolyte

Claims (8)

A surface-treated copper foil having a roughened surface by roughening treatment on the surface, wherein 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 0.10 μm or more and 0.98 μm or less. Surface-treated copper foil. According to paragraph 1,
A surface-treated copper foil in which the roughened surface is formed on the drum surface of the electrolytic copper foil. According to claim 1 or 2,
A surface-treated copper foil in which 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. According to claim 1 or 2,
A surface-treated copper foil 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. According to claim 1 or 2,
The said roughened surface is a surface-treated copper foil provided with an aggregate in which three or more roughened particles aggregated. According to claim 1 or 2,
A surface-treated copper foil having a 10-point average roughness Rz of the roughened surface measured using a contact-type surface roughness measuring device of 1.2 ㎛ or more and 3.8 ㎛ or less. A copper-clad laminate comprising the surface-treated copper foil according to claim 1 or 2, and a resin substrate laminated on a roughened surface of the surface-treated copper foil. A printed wiring board comprising the copper clad laminate according to claim 7.

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