阅读说明：本技术 表面处理铜箔、覆铜层叠板以及印刷电路板 (Surface-treated copper foil, copper-clad laminate, and printed wiring board ) 是由 高泽亮二 佐藤章 中崎竜介 于 2020-06-02 设计创作，主要内容包括：本发明提供一种表面处理铜箔,其具有微细布线加工性,并且与树脂制基板的密合性优异。该表面处理铜箔是在表面具有利用粗化处理而形成的粗化面的表面处理铜箔,其中,粗化面的最小自相关长度Sal为1.0μm以上且8.5μm以下,均方根高度Sq为0.10μm以上且0.98μm以下。(The invention provides a surface-treated copper foil, which has fine wiring processability and excellent adhesion with a resin substrate. The surface-treated copper foil has a roughened surface formed by roughening treatment on the surface, wherein the roughened surface has a minimum autocorrelation length Sal of 1.0 to 8.5 [ mu ] m, and a root-mean-square height Sq of 0.10 to 0.98 [ mu ] m.)

1. A surface-treated copper foil having a roughened surface formed by roughening treatment on the surface thereof, wherein,

the minimum autocorrelation length Sal of the roughened surface is 1.0 to 8.5 [ mu ] m, and the root-mean-square height Sq is 0.10 to 0.98 [ mu ] m.

2. The surface-treated copper foil according to claim 1,

the roughened surface is formed on the drum surface of the electrolytic copper foil.

3. The surface-treated copper foil according to claim 1 or 2,

the minimum autocorrelation length Sal of the roughened surface is 1.3 to 6.5 [ mu ] m, and the root-mean-square height Sq is 0.21 to 0.72 [ mu ] m.

4. The surface-treated copper foil according to any one of claims 1 to 3,

the minimum autocorrelation length Sal of the roughened surface is 1.7-5.7 μm, and the root-mean-square height Sq is 0.28-0.54 μm.

5. The surface-treated copper foil according to any one of claims 1 to 4,

the roughened surface has an aggregate in which three or more roughened particles are aggregated.

6. The surface-treated copper foil according to any one of claims 1 to 5,

The roughness Rz of the roughened surface measured by a contact surface roughness measuring instrument is 1.2 μm or more and 3.8 μm or less in ten points.

7. 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.

8. A printed circuit board comprising the copper-clad laminate according to claim 7.

Technical Field

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

Background

As the copper foil used for the copper-clad laminate and the printed wiring board, an electrolytic copper foil obtained by peeling a copper foil deposited on a drum of an electrolytic deposition apparatus from the drum is used. The electrolytic copper foil peeled off from the drum has a relatively smooth electric field deposition starting surface (hereinafter referred to as "drum surface"), and an electrolytic deposition finishing surface (hereinafter referred to as "deposition surface") on the opposite side generally has irregularities. The copper-clad laminate is produced by disposing a resin substrate on the deposition surface of the electrolytic copper foil and performing hot pressing, and the deposition surface is usually roughened by roughening treatment to improve adhesion to the resin substrate.

Recently, a printed wiring board (particularly a build-up circuit board) has been manufactured by bonding an adhesive resin such as an epoxy resin to a roughened surface of a copper foil in advance, using a copper foil with a resin, which is formed by using the adhesive resin as a semi-cured (B-stage) insulating resin layer, as a copper foil for forming a surface circuit, and thermocompression bonding one side of the insulating resin layer of the copper foil to an insulating substrate. In the build-up wiring board, it is desired to highly integrate various electronic components, and in response to this, higher density wiring patterns are also required, and the wiring patterns are gradually becoming printed wiring boards requiring fine line widths and line-to-line pitches, so-called fine patterns. For example, a multilayer substrate used for a server, a router, a communication base station, a vehicle-mounted substrate, or the like, or a multilayer substrate for a smartphone is required to have a printed wiring board having a high-density ultrafine wiring (hereinafter referred to as a "high-density circuit board").

A high-density circuit board having an arbitrary layer (AnyLayer) which connects layers by laser via holes having a high degree of freedom of arrangement is mainly used for a main board of a smartphone, but in recent years, fine wiring has been advanced, and wiring having a line width and a pitch between lines (hereinafter referred to as "L & S") of 30 μm or less, respectively, is required.

However, the problem of deterioration due to moisture absorption is evident in that the adhesion between the wiring and the resin is reduced due to the influence of moisture absorbed by the resin of the high-density circuit board because of the miniaturization of the wiring. In particular, in recent smartphones, heat generation increases with an increase in power consumption, and moisture absorption deterioration tends to be accelerated, and it is difficult to maintain adhesion between wiring and resin.

Patent document 1 discloses a copper foil having excellent adhesion to a highly heat-resistant resin by making the shape of roughening particles sharp, but when etching is performed for forming wiring, the roughening particles having a sharp shape are likely to be dissolved and remain (root portion remains), and there is a possibility that fine wiring processability may become insufficient.

Patent document 2 discloses a copper foil having a small roughness of the drum surface and excellent fine wiring processability, but since there is no measure against moisture absorbed by a resin substrate, there is a possibility that the adhesion between the copper foil and the resin substrate may be reduced in a high-temperature and high-humidity environment.

Patent document 3 discloses a copper foil excellent in high-frequency characteristics in which the steepness of the change in the surface roughness is controlled, but in the case of manufacturing a high-density circuit board having fine wirings each having an L & S of 30 μm or less, for example, the adhesion between the copper foil and a resin substrate in a high-temperature and high-humidity environment may be reduced.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 236058 2010

Patent document 2: japanese patent laid-open publication No. 76601 2018

Patent document 3: international publication No. 2018/198905

Disclosure of Invention

Problems to be solved by the invention

The present invention addresses the problem of providing a surface-treated copper foil that has fine-wiring processability and has excellent adhesion to a resin substrate. Further, the present invention has a technical problem of providing a copper-clad laminate having fine wiring processability and a printed wiring board capable of forming high-density ultrafine wiring.

Means for solving the problems

A surface-treated copper foil according to one aspect of the present invention is a surface-treated copper foil having a roughened surface formed by roughening treatment on a surface thereof, and the surface-treated copper foil is characterized in that: the minimum autocorrelation length Sal of the roughened surface is 1.0 to 8.5 μm, and the root-mean-square height Sq is 0.10 to 0.98 μm.

In addition, another aspect of the present invention provides a copper-clad laminate including: a resin substrate comprising the surface-treated copper foil according to the above aspect and a roughened surface laminated on the surface-treated copper foil.

Further, another aspect of the present invention provides a printed circuit board including: the copper-clad laminate according to the other aspect is provided.

Effects of the invention

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

Drawings

Fig. 1 is a diagram illustrating a method for manufacturing an electrolytic copper foil using an electrolytic deposition apparatus.

Detailed Description

One embodiment of the present invention will be explained. The embodiment described below is an example of the present invention. In addition, various modifications or improvements may be added to the present embodiment, and such modifications or improvements may be included in the present invention.

The surface-treated copper foil according to one embodiment of the present invention has a roughened surface formed by roughening treatment on the surface, wherein the roughened surface has a minimum autocorrelation length Sal of 1.0 μm or more and 8.5 μm or less and a root mean square height Sq of 0.10 μm or more and 0.98 μm or less.

With this configuration, the surface-treated copper foil of the present embodiment has a workability that can cope with fine wiring of a high-density circuit board, and is excellent in adhesion to a resin substrate in a normal state and adhesion under a high-temperature and high-humidity environment (for example, after a pressure cooker test). Therefore, the surface-treated copper foil of the present embodiment can be preferably used for manufacturing a copper-clad laminate and a printed wiring board. When the surface-treated copper foil of the present embodiment is used, a copper-clad laminate having fine wiring processability can be produced. Further, by using the surface-treated copper foil of the present embodiment, a printed wiring board having high-density ultrafine wiring can be manufactured. In the present invention, the term "normal state" means a state in which the surface-treated copper foil is left under normal temperature and humidity (for example, a temperature of 23. + -. 2 ℃ C., a humidity of 50. + -. 5% RH).

The minimum autocorrelation length Sal is a value specified in ISO25178, and is defined as the shortest distance in a plane (unless otherwise specified, s is the shortest distance in which s decays from 1 to 0.2) at which the autocorrelation function (see the following formula 1) of the surface shape decays to a correlation value s, and can be measured, for example, by a three-dimensional white light interference microscope or a laser microscope. The minimum autocorrelation length Sal can be used as an index of the steepness of the change in the surface roughness caused by the undulation or the like of the surface of the copper foil in the copper foil. That is, the smaller the value of the minimum autocorrelation length Sal, the shorter the distance the step changes, so it can be said that the change in the surface roughness is steep.

The root mean square height Sq is a value specified in ISO25178, and is defined as a standard deviation of a distance from an average surface as shown in the following formula 2, and can be measured by, for example, a three-dimensional white light interference type microscope or a laser microscope. The root mean square height Sq represents unevenness of surface shape due to roughened shape or the like in the copper foil. In addition, z (x, y) in equations 1 and 2 represents coordinates in the height direction in x and y coordinates.

The surface-treated copper foil of the present embodiment will be described in further detail below.

As a result of intensive studies, the present inventors have found that the phenomenon of moisture absorption in a high-temperature and high-humidity environment in a pressure cooker test (hereinafter, referred to as "PCT") includes both moisture absorption from the surface of a resin substrate and moisture absorption from the interface between a copper foil and the resin substrate, and that the contribution of moisture absorption from the interface between the copper foil and the resin substrate to the reduction in adhesion between the resin substrate and the copper foil after the PCT is large. It can be considered that: when moisture penetrates into the interface between the copper foil and the resin substrate, chemical components such as a coupling agent that improve the adhesion are hydrolyzed, or an oxide film grows on the surface of the copper foil due to the influence of moisture, whereby 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 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 moderately steep fluctuations, the diffusion rate of moisture at the interface between the surface-treated copper foil and the resin substrate is slow. 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 (e.g., after PCT), and thus the adhesion between the surface-treated copper foil and the resin substrate is easily maintained in a high state.

When the minimum autocorrelation length Sal of the roughened surface of the surface-treated copper foil exceeds 8.5 μm, the waviness is gentle, and therefore the diffusion rate of moisture at the interface between the surface-treated copper foil and the resin substrate is high, and there is a possibility that the adhesion between the surface-treated copper foil and the resin substrate is reduced in a high-temperature and high-humidity environment. 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 waviness changes steeply in excess, and therefore, a gap is easily formed at the interface between the surface-treated copper foil and the resin substrate. Therefore, moisture is likely to accumulate in the gap under a high-temperature and high-humidity environment, and thus the adhesion between the surface-treated copper foil and the resin substrate may be reduced.

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

When the minimum autocorrelation length Sal of the roughened surface of the surface-treated copper foil is 1.0 to 8.5 μm and the root-mean-square height Sq is 0.10 to 0.98 μm, the adhesion between the surface-treated copper foil and the resin substrate and the fine wiring processability in a high-temperature and high-humidity environment can be achieved at a high level.

Since the surface-treated copper foil having a roughened surface with a root mean square height Sq of 0.10 μm or more and 0.98 μm or less has a suitably uniform height of fine irregularities, the surface-treated copper foil is stably dissolved when forming a wiring by etching, and a pattern having a high etching factor (that is, the cross-sectional shape of the wiring is likely to be a nearly rectangular shape) is easily obtained.

If the root mean square height Sq of the roughened surface of the surface-treated copper foil exceeds 0.98 μm, the locally high convex portions of the surface-treated copper foil may dissolve and remain on the resin substrate (that is, root residue may occur) when the wiring is formed by etching, and the etching factor may be lowered. When 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 therefore, the adhesion between the surface-treated copper foil and the resin substrate in a normal state or in a high-temperature and high-humidity environment may be reduced.

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 to 0.72 μm, more preferably 0.28 to 0.54 μm.

Further, the ten-point average roughness Rz of the roughened surface measured by a contact surface roughness measuring instrument 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 by the anchor effect (anchor effect) is exhibited.

Further, the surface-treated copper foil of the present embodiment can be produced by roughening the surface of the electrolytic copper foil to form a roughened surface, and the roughened surface may be a drum surface or a precipitation surface. For example, if the drum surface of the electrolytic copper foil is roughened, the roughened surface is formed on the drum surface of the electrolytic copper foil.

The surface-treated copper foil of the present embodiment will be described in further detail below. First, an example of a method for producing a surface-treated copper foil will be described.

(1) Method for manufacturing electrolytic copper foil

The electrolytic copper foil can be produced, for example, by using an electrolytic deposition apparatus shown in FIG. 1. The electrolytic deposition apparatus of FIG. 1 comprises: an insoluble anode 104 made of titanium coated with a platinum group element or an oxide thereof; a titanium cathode drum 102 disposed opposite to the insoluble anode 104; and a polishing wheel 103 for polishing the cathode drum 102 to remove the oxide film generated 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 the cathode drum 102 is rotated at a constant speed. Thereby, copper is precipitated on the surface of the cathode drum 102. The deposited copper was peeled off from the surface of the cathode drum 102 and continuously wound up, thereby obtaining an electrolytic copper foil 101.

In the production of the electrolytic copper foil, an additive may be added to the electrolytic solution 105. As the additive, various additives can be used, and examples thereof include: ethylene thiourea, polyethylene glycol, tetramethyl thiourea, polyacrylamide, and the like. Here, by increasing the amount of ethylene thiourea or tetramethyl thiourea added, the tensile strength of the electrodeposited copper foil in the normal state and the tensile strength of the electrodeposited copper foil measured at room temperature after heating at 220 ℃ for 2 hours can be improved.

Molybdenum may be added to the electrolytic solution 105. By adding molybdenum, the etching properties of the copper foil can be improved. In general, in electrolytic deposition, the copper concentration of the electrolyte 105 (the concentration of copper alone without taking sulfuric acid components into consideration in copper sulfate) is 13 to 72g/L, the sulfuric acid concentration of the electrolyte 105 is 26 to 133g/L, the liquid temperature of the electrolyte 105 is 18 to 67 ℃, and the current density is 3 to 67A/dm²The treatment time is 1 second to 1 minute and 55 seconds.

(2) Surface treatment of electrolytic copper foil

< relief processing >

The relief processing is 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 to the above numerical range, it is necessary to control the undulation shape of the surface of the electrolytic copper foil by the undulation processing.

An example of the undulation treatment is PR (periodic reverse) electrolysis using a solution containing phosphoric acid, sulfuric acid, or the like at a high concentration as an electrolytic bath. In PR electrolysis, copper is dissolved out by an anodic reaction under a reverse current (negative current), whereby an adhesive layer having a resistance different from that of an electrolytic bath is formed near the surface of the copper foil. It can be considered that: when a forward current (positive current) flows, the thickness of the adhesive layer is reduced at the raised portions of the undulations and the resistance is reduced as compared with the raised portions of the undulations, so that the plating current selectively concentrates on the raised portions and a steep undulation shape is obtained.

Another example of the waving treatment is pulse electrolysis in which a pulse current of a reverse current is passed through a copper foil using a copper sulfate solution to which a polymer such as a water-soluble acrylic polymer, guar gum, or polyethylene oxide is added as an electrolytic bath. It can be considered that: by passing a pulse current of a reverse current of high current density after the polymer adheres to the undulating convex portions, the undulating concave portions are selectively dissolved, and a steep undulating shape is obtained.

< roughening treatment >

The surface of the electrodeposited copper foil subjected to the undulation treatment is roughened to form a roughened surface for the purpose of improving adhesion to the resin substrate. 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 set to the above numerical range.

As an example of the roughening treatment, there is a method of electroplating an electrolytic copper foil in a copper sulfate solution to which metals such as cobalt (Co), iron (Fe), molybdenum (Mo), tin (Sn), nickel (Ni) and the like are added while stirring the copper sulfate solution by bubbling nitrogen gas. The kind of the metal added to the copper sulfate solution may be one kind, or two or more kinds.

When the roughening treatment is performed by the electroplating as described above, the roughened particles are formed on the surface of the copper foil to form a roughened surface, and the roughened surface of the surface-treated copper foil may have an aggregate in which three or more roughened particles are aggregated. Since the shape of the aggregate is complicated, 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 decrease in adhesion between the surface-treated copper foil and the resin substrate in a high-temperature and high-humidity environment is further suppressed. It can be considered that: when the aggregate is composed of three or more roughened particles, the protrusions composed of the aggregate are higher than the periphery of the aggregate, and the change in the roughness of the roughened surface becomes steep, so 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 of 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 functions as follows: when the surface-treated copper foil is thermocompression bonded to a resin substrate, deterioration of the resin substrate and surface oxidation of the surface-treated copper foil due to reaction between the surface-treated copper foil and the resin substrate are prevented, and adhesion between the surface-treated copper foil and the resin substrate is improved. The nickel layer prevents thermal diffusion of zinc in the zinc layer into the surface-treated copper foil when the surface-treated copper foil is thermocompression bonded to the resin substrate. That is, the nickel layer functions as a base layer of the zinc layer for effectively exhibiting the above-described functions of the zinc layer.

The nickel layer and the zinc layer can be formed by applying a known electroplating method or electroless plating method. Further, the nickel layer may be formed of pure nickel or a phosphorus-containing nickel alloy.

Further, it is preferable to further perform chromate treatment on the zinc layer because an antioxidation 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, and for example, a method disclosed in Japanese patent laid-open No. Sho 60-86894 can be mentioned. By making the amount of chromium 0.01 to 0.3mg/dm ²The chromium oxide and the hydrate thereof adhere to the surface-treated copper foil, and thus the surface-treated copper foil can be provided with an excellent antioxidant function.

< silane treatment >

The chromate-treated surface may be further subjected to a surface treatment (silane treatment) using a silane coupling agent. Since the surface of the surface-treated copper foil (the surface on the side to be bonded to the resin substrate) is provided with a functional group having a strong affinity for the adhesive by surface treatment using a silane coupling agent, the adhesion between the surface-treated copper foil and the resin substrate is further improved, and the rust resistance and moisture absorption heat resistance of the surface-treated copper foil are also further improved.

As the silane coupling agent, various silane coupling agents can be used, and examples thereof include: and silane coupling agents such as vinyl silane, epoxy silane, styrene silane, methacryloxy silane, acryloxy silane, amino silane, ureido silane, chloropropyl silane, mercapto silane, sulfide silane, and isocyanate silane.

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

(3) Method for manufacturing copper-clad laminate and printed circuit 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. In this case, the roughened surface of the surface-treated copper foil is opposed to the resin substrate. Then, when the resin substrate and the surface-treated copper foil are joined to each other by applying a pressure in the laminating direction while heating the resin substrate and the surface-treated copper foil, a copper-clad laminate with or without a carrier can be obtained. The surface-treated copper foil of the present embodiment has high tensile strength and therefore can sufficiently cope with the use of no carrier.

Next, the surface of the copper foil of the copper-clad laminate is irradiated with CO, for example₂And (5) gas laser to open holes. That is, the surface of the copper foil on which the laser light absorption layer is formed is irradiated with CO₂The gas laser beam performs a hole-forming process for forming a through hole penetrating the surface-treated copper foil and the resin substrate. Then, a printed wiring board can be obtained by forming a circuit such as a high-density wiring circuit on the surface-treated copper foil by a conventional method.

[ example ]

The present invention will be described in more detail below with reference to examples and comparative examples.

(A) Electrolytic copper foil

As the raw material copper foil used for producing the surface-treated copper foils of examples 1 to 15 and comparative examples 1 to 5, a special electrolytic copper foil WS manufactured by Kogawa electric industries Co., Ltd was used. The ten-point average roughness Rz of the drum surface of the electrolytic copper foil was 0.9 μm, and the ten-point average roughness Rz of the deposition surface was 1.0 μm. These ten-point average roughness Rz are measured by using a contact surface roughness measuring machine described later.

(B) Relief machining treatment

First, the bump surface or the deposition surface (see table 1) of the electrolytic copper foil was subjected to a waving treatment. As the undulation 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 is performed. In comparative examples 1 to 3, the electrolytic copper foil was subjected to roughening treatment as the next step without performing the roughening treatment.

[ Table 1]

The concentrations of copper and phosphoric acid in the bath for PR electrolysis are shown in table 1. In addition, as the polymer in the electrolytic bath for pulse electrolysis, a water-soluble acrylic polymer (manufactured by Toyo Synthesis Co., Ltd.), guar gum (manufactured by Sanchang Co., Ltd.), or polyethylene oxide (manufactured by Sumitomo Seiko Seisaku-Sho Co., Ltd.) was used. The concentrations of copper, sulfuric acid, water-soluble acrylic polymer, guar gum, and polyethylene oxide in the electrolytic bath for pulse electrolysis are shown in table 1. In addition, copper sulfate pentahydrate was added to the PR electrolysis bath and the pulse electrolysis bath, but the concentrations of metal copper are shown in table 1.

The conditions of PR electrolysis and pulse electrolysis, i.e., the surface subjected to the undulation treatment (treated surface), electrolysis conditions, treatment time, and temperature of the electrolytic bath are shown in Table 1. Under the electrolysis conditions in table 1, Ion1 represents the pulse current density in the first stage, Ion2 represents the pulse current density in the second stage, ton1 represents the pulse current application time in the first stage, and ton2 represents the pulse current application time in the second stage.

(C) Roughening treatment

Next, the surface of the electrolytic copper foil subjected to the undulation processing is roughened to form a roughened surface, thereby producing a surface-treated copper foil. Specifically, a roughened surface having fine irregularities formed by copper particles is formed by performing electroplating in which fine copper particles are electrodeposited on the surface of an electrolytic copper foil as roughening treatment. The plating solution used for the electroplating contained copper sulfate and sulfuric acid, and contained cobalt or iron, and the copper concentration, sulfuric acid concentration, cobalt concentration, and iron concentration are shown in table 2. In addition, copper sulfate pentahydrate was added to the plating solution, but the concentration of metallic copper is shown in table 2.

The plating conditions, that is, the surface subjected to roughening treatment (treated surface), the current density I, the treatment time, the temperature of the plating bath, and the presence or absence of nitrogen bubbling in the plating bath are shown in table 2.

[ Table 2]

(D) Formation of a Nickel layer (base layer)

Next, the roughened surface of the surface-treated copper foil was plated under Ni plating conditions shown below to form a nickel layer (Ni deposition amount: 0.33 mg/dm)²). The plating solution for nickel plating contains nickel sulfate and ammonium persulfate ((NH)₄)₂S₂O₈) Boric acid (H)₃BO₃) The concentration of nickel is 7.5g/L, the concentration of ammonium persulfate is 40.0g/L, and the concentration of boric acid is 19.5 g/L. Further, the plating bath was at a temperature of 28.5 ℃ and a pH of 3.8, and the current density was 1.8A/dm²The plating treatment time is 1 second to 2 minutes.

(E) Formation of Zinc layer (Heat-resistant treatment layer)

Further, the nickel layer was electroplated under the following Zn plating conditions to form a zinc layer (Zn deposition amount: 0.10 mg/dm)²). The plating solution for galvanizing contains zinc sulfate heptahydrate and sodium hydroxide, wherein the concentration of zinc is 1-30 g/L, and the concentration of sodium hydroxide is 25-220 g/L. In addition, the temperature of the plating solution is 5-60 ℃, and the current density is 0.1-10A/dm²The plating treatment time is 1 second to 2 minutes.

(F) Formation of chromate treatment layer (rust-preventive treatment layer)

Further, the zinc layer was subjected to electroplating under the following Cr plating conditions to form a chromate treatment layer (Cr deposition amount: 0.03 mg/dm)²). The bath for chromium plating contains chromic anhydride (CrO) ₃) The chromium concentration was 2.2 g/L. In addition, the temperature of the plating solution is 15-45 ℃, the pH value is 2.5, and the current density is 0.3A/dm²The plating treatment time is 1 second to 2 minutes.

(G) Formation of silane coupling agent layer

Further, the following treatment was performed to form a silane coupling agent layer on the chromate treatment layer. That is, methanol or ethanol was added to the silane coupling agent aqueous solution to adjust the pH to a predetermined value, thereby obtaining a treated solution. The treatment liquid was applied to a chromate treatment layer of a surface-treated copper foil, and after being held for a predetermined time, the chromate treatment layer was dried by hot air, thereby forming a silane coupling agent layer.

(H) Evaluation of

As described above, the surface-treated copper foils of examples 1 to 15 and comparative examples 1 to 5 were produced. The foil thickness of these surface-treated copper foils is shown in table 3. The obtained surface-treated copper foils were subjected to various evaluations.

< 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 having an L & S of 30/30 μm was formed by a subtractive process (CVD). Then, a wiring pattern is formed by etching. As the resist, a dry resist film was used, and as the etching solution, a mixed solution containing copper chloride and hydrochloric acid was used. Then, the etching factor (Ef) of the resulting wiring pattern was measured.

The etching factor is a value expressed by the following equation, where H represents the foil thickness of the copper foil, B represents the bottom width of the formed wiring pattern, and T represents the top width of the formed wiring pattern.

Ef＝2H/(B-T)

In the present example and the comparative example, the case where the etching factor was 2.5 or more was regarded as a good product, and the case where the etching factor was less than 2.5 was regarded as a defective product.

If the etching factor is small, the vertical property of the side wall in the wiring pattern collapses, and in the case of a fine wiring pattern having a narrow line width, a copper foil is left dissolved between adjacent wiring patterns, which may cause a short circuit or a disconnection. In this test, the bottom width B and the top width T were measured with a microscope for the wiring pattern at the position of the etch-in-place (just etch) (the position of the end of the resist was aligned with the position of the bottom of the wiring pattern), and the etching factor was calculated. The results are shown in Table 3.

[ sealing property at Normal State ]

A resin substrate is bonded to the roughened surface of the surface-treated copper foil to produce a copper-clad laminate. As the resin substrate, commercially available EI-6765 manufactured by Sumitomo Bakelite of FR4(Flame Retardant Type 4) series resin was used, and the curing temperature and the curing time at the time of bonding were 170 ℃ and 2 hours, respectively.

The surface-treated copper foil of the produced copper-clad laminate was subjected to etching to form a circuit wiring having a width of 1mm to produce a printed wiring board, and the 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 a double-sided tape, and the circuit wiring was pulled and peeled in a 90-degree direction at a speed of 50 mm/min to measure the adhesion (kN/m). The measurement was performed five times, and the average of the five obtained measurement values was defined as the adhesion in the normal state. The adhesion was measured using a universal testing machine (TENSILON, manufactured by a & D). In the examples and comparative examples, good products were obtained when the adhesion in the normal state was 0.6kN/m or more, and defective products were obtained when the adhesion was less than 0.6 kN/m. The results are shown in Table 3.

[ adhesion under high temperature and high humidity Environment ]

The adhesion under a high-temperature and high-humidity environment was measured using the same measurement sample as the above-described measurement sample used for measuring the adhesion under normal conditions. First, a PCT was performed by holding a sample for measurement at 121 ℃, 100% RH, and 2atm for 48 hours using a pressure cooker tester. 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 five times, and the average of the five obtained measurement values was defined as the adhesion after PCT. In the examples and comparative examples, the adhesion after PCT was 0.2kN/m or more and the adhesion after PCT was 0.2kN/m or less, respectively, and the adhesion was regarded as a defective product. The results are shown in Table 3.

[ measurement of minimum autocorrelation Length Sal, root mean Square height Sq ]

The surface shapes of the roughened surfaces of the surface-treated copper foils of examples 1 to 15 and comparative examples 1 to 5 were measured using a three-dimensional white light interference microscope Wyko ContourGT-K by BRUKER, and subjected to shape analysis to determine the minimum autocorrelation length Sal and the root mean square height Sq. The surface shape was measured at any five positions of each surface-treated copper foil, and the five positions were subjected to shape analysis to determine the minimum autocorrelation length Sal and the root-mean-square height Sq of each of the five positions. Then, the average values of the results obtained at five places were 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 (Vertical Scanning Interferometry) measurement method (Vertical Scanning Interferometry) using a high-resolution CCD (Charge Coupled Device) camera. The conditions were: the light source is white light, the measurement magnification is 10 times, the measurement range is 477 μm × 357.8 μm, the Lateral Sampling (Lateral Sampling) is 0.38 μm, the speed (speed) is 1, the reverse scan (Backscan) is 10 μm, the Length (Length) is 10 μm, the Threshold (Threshold) is 3%, the term Removal (term Removal) (Cylinder and Tilt), the Data recovery (Data Restore) (method: leave-on, iteration (iteration) 5), the statistical Filter (statistical Filter) (Filter Size 3, Filter Type Median (Median), the Fourier Filter (High-Frequency Pass-through), the Fourier Filter (Fourier Filter) Frequency 12. High-Frequency Cutoff (Gaussian) is 12. fig. ^-1) And after the filtering processing, performing data processing. The results are shown in Table 3.

[ measurement of Ten-Point average roughness Rz ]

The roughened surfaces of the surface-treated copper foils of examples 1 to 15 and comparative examples 1 to 5 were treated in accordance with JIS B0601: 1994 specifies a ten point average roughness Rz (. mu.m). The measurement was performed at any five positions of each surface-treated copper foil, and the average value thereof was taken as ten-point average roughness Rz. Further, as a measuring device, a contact surface roughness measuring device Surfcorder SE1700 manufactured by osaka research, ltd. The measurement conditions were a measurement length of 4.8mm, a sampling length of 4.8mm, and a cutoff (cutoff) value of 0.8 mm. The results are shown in Table 3.

[ aggregate ]

Three visual fields (13.9 μm in vertical direction and 18.6 μm in horizontal direction) of 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 at a magnification of 5000 times using a scanning electron microscope, and it was confirmed whether or not there was an aggregate in which three or more roughened particles aggregated. The results are shown in Table 3.

[ Table 3]

As is clear from table 3, the surface-treated copper foils of examples 1 to 15 had large etching factors (Ef), and had excellent adhesion in the normal state and adhesion after PCT, in addition to having fine wiring processability.

Description of the reference numerals

101: electrolytic copper foil; 102: a cathode drum; 104: an insoluble anode; 105: and (3) an electrolyte.