JP7366436B2 - Surface-treated copper foil, copper-clad laminates, and printed wiring boards - Google Patents

Description

The present invention relates to a surface-treated copper foil that can be suitably used for manufacturing printed wiring boards and the like, as well as a copper-clad laminate and a printed wiring board using the surface-treated copper foil.

In recent years, with the further increase in mobile communication traffic represented by 5G communication, high-frequency signals of several GHz to 100 GHz can be transmitted to printed wiring boards installed in electronic devices that support network infrastructure. is increasing. Therefore, various improvements have been made to the surface-treated copper foil used as a material for printed wiring boards and the resin base material to which the surface-treated copper foil is bonded to reduce the transmission loss of high-frequency signals.

For example, in the case of surface-treated copper foil, in order to reduce transmission loss, it is preferable that the surface has a low roughness. However, if the surface of the surface-treated copper foil has low roughness, its adhesion to the resin base material will be low. Regarding resin base materials, in order to reduce transmission loss, a base material made of resin with a low dielectric constant and dielectric loss tangent (hereinafter sometimes referred to as "low dielectric resin") should be used. It is preferable. However, since the low dielectric resin has poor reactivity, the adhesion between the surface-treated copper foil and the resin base material becomes low. As described above, when improvements are made to reduce the transmission loss of high-frequency signals, there is a risk that the adhesion between the surface-treated copper foil and the resin base material becomes insufficient.

Furthermore, as a trend in recent years, the reliability required of printed wiring boards has become more severe in order to withstand the use of electronic devices under harsher environments than before. A typical example of the required reliability is the ability to maintain high adhesion between the surface-treated copper foil and the resin base material even when affected by moisture (hereinafter, such performance may be referred to as "moisture resistance"). ), and there is a growing demand for even better moisture resistance than before.

Various proposals have been made as techniques for improving moisture resistance. For example, Patent Document 1 discloses a technique for improving moisture resistance by introducing hydroxyl groups into the antirust treatment layer of surface-treated copper foil to strengthen the bond between the copper foil substrate and the silane coupling agent. Further, Patent Document 2 discloses a technique for improving moisture resistance by devising a rust prevention treatment layer and a silane coupling agent treatment of a surface-treated copper foil. Patent Document 3 discloses a technique for improving moisture resistance by devising a rust prevention layer of a surface-treated copper foil, treatment with a silane coupling agent, and drying conditions.

Japanese Patent Application Publication No. 7-331454 Patent No. 3103683 Japanese Patent Application Publication No. 2001-214298 Patent No. 5219952 Japanese Patent Application Publication No. 8-51281

However, in these conventional technologies, the resin base material is not a low dielectric resin base material, but a general glass epoxy base material represented by FR4 (Flame Retardant Type 4) material, so it is not an excellent material. It was easy to obtain moisture resistance. When using a surface-treated copper foil with low roughness or a base material made of a low dielectric resin, which makes it difficult to obtain high adhesion, it is difficult to obtain excellent moisture resistance using the above-mentioned conventional techniques.

In addition, increasing the amount of silane coupling agent contained in the silane coupling agent layer provided on surface-treated copper foil is an effective means for improving moisture resistance, but this alone is not enough to increase the Not only will it not be possible to meet the standard requirements, but other performance may be impaired. For example, if the amount of silane coupling agent contained in the silane coupling agent layer is large, the surface of the surface-treated copper foil may deteriorate when the surface-treated copper foil is wound and stored in a coiled state (rolled state) for a long period of time. It has recently become clear that it is susceptible to discoloration.

This is due to disruptions in the supply chain due to the effects of the recent US-China trade friction and the impact of factory suspensions caused by the new coronavirus infection, resulting in inventory retention and intentions in a different environment or situation than before. This issue has become clear due to excessive inventory. Note that the ability of the surface-treated copper foil to resist discoloration even when the surface-treated copper foil is wound into a coiled state and stored for a long period of time may be hereinafter referred to as "discoloration resistance."

An object of the present invention is to provide a surface-treated copper foil having excellent moisture resistance and discoloration resistance. Another object of the present invention is to provide a copper-clad laminate and a printed wiring board that have excellent adhesion between a surface-treated copper foil and a resin base material.

In order to solve the above problems, the present inventors focused on the state of the silane coupling agent layer provided on the surface of the surface-treated copper foil.
A silane coupling agent is generally diluted with a solvent such as water or alcohol, and applied to a metal surface in a state where it is hydrolyzed and has silanol groups present. The hydroxyl groups present on the surface of the metal and the silanol groups of the silane coupling agent undergo dehydration condensation to form metalloxane bonds, or the silanol groups of the silane coupling agents dehydrate and condense with each other to form siloxane bonds. It is known that a strong silane coupling agent layer is formed.

However, in view of the actual industrial manufacturing method of conventional surface-treated copper foil, the present inventors discovered that not all silanol groups are dehydrated and condensed when the surface-treated copper foil is completed. Ta. This tends to be more pronounced as the amount of silane coupling agent contained in the silane coupling agent layer increases. The present inventors have found that when such a conventional surface-treated copper foil and a resin base material are bonded together and heated and pressed, moisture resistance is particularly deteriorated.

The details of this are not clear, but when surface-treated copper foil and resin base material are heated and pressed with some silanol groups remaining in the silane coupling agent layer, the silanol groups undergo dehydration condensation. water is generated. Since the generated water exists at the bonding interface between the resin base material and the silane coupling agent layer, the integrity of the bond between the resin base material and the silane coupling agent layer is impaired, and the moisture resistance test This is considered to be the starting point for moisture intrusion into the bonding interface and a decrease in adhesion between the surface-treated copper foil and the resin base material. Note that the silanol groups remaining in this silane coupling agent layer are referred to as "residual silanol groups" in this specification.

In addition, if surface-treated copper foil with a large number of residual silanol groups in the silane coupling agent layer is wound and stored in a coiled state for a long period of time, dehydration condensation of the residual silanol groups will occur over time in the storage environment, so surface-treated copper foil Water may form within the foil coil. Moreover, since the surface-treated copper foils overlap and are in contact with each other in the coil of the surface-treated copper foils, there is a possibility that silanol groups may adhere to the other surface with which they are in contact. The present inventors have discovered that when the above-mentioned generation of water or adhesion of silanol groups occurs while the surface-treated copper foil in a coiled state is stored, the surface of the surface-treated copper foil tends to discolor.

As a result of intensive research based on these findings, the present inventors found that heat treatment for drying the solvent of the silane coupling agent in the formation process of the silane coupling agent layer during the production of surface-treated copper foil. It has also been found that the amount of residual silanol groups can be significantly reduced by further performing sufficient heat treatment. Surface-treated copper foil with a small amount of residual silanol groups in the silane coupling agent layer has both extremely high moisture resistance and discoloration resistance.

In addition, the present inventors also discovered that the residual silanol groups in the silane coupling agent layer can be easily removed from the surface of the surface-treated copper foil by simple washing with water. It has also been found that by comparing the amount of silicon atoms contained in the silane coupling agent layer before and after washing with water, it is possible to evaluate the amount of residual silanol groups in the silane coupling agent layer.

That is, the surface-treated copper foil according to one embodiment of the present invention includes a copper foil base and a silane coupling agent layer provided on at least one surface of the copper foil base and formed of a silane coupling agent. , the ratio of the amount M _A of silicon atoms contained in the silane coupling agent layer to the amount M _B of silicon atoms contained in the silane coupling agent layer after washing with pure water for 30 seconds M _B /M _A is 0.700 or more and 1.000 or less, and the amounts of silicon atoms M _A and M _B were measured by analyzing the surface of the silane coupling agent layer by X-ray fluorescence analysis. This is the summary.

A copper-clad laminate according to another aspect of the present invention includes the surface-treated copper foil according to the above-mentioned one aspect and a resin base material bonded to the surface-treated copper foil.
A printed wiring board according to yet another aspect of the present invention includes the surface-treated copper foil according to the other aspect.

The surface-treated copper foil according to the present invention has excellent moisture resistance and discoloration resistance. The copper-clad laminate and printed wiring board according to the present invention have excellent adhesion between the surface-treated copper foil and the resin base material.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view illustrating a surface-treated copper foil according to an embodiment of the present invention.

An embodiment of the present invention will be described. Note that the embodiment described below shows an example of the present invention. Further, various changes or improvements can be made to this embodiment, and forms with such changes or improvements can also be included in the present invention.

As shown in FIG. 1, the surface-treated copper foil according to an embodiment of the present invention is provided on a copper foil base 1 and at least one surface (only one surface in the example of FIG. 1) of the copper foil base 1, and It has a silane coupling agent layer 3 formed of a silane coupling agent. Then, the amount M _A of silicon atoms contained in the silane coupling agent layer 3 (that is, the amount M _A of silicon atoms contained in the silane coupling agent layer 3 before being washed with pure water), The ratio M _B /M _A to the amount M _B of silicon atoms contained in the silane coupling agent layer 3 after washing with water for 30 seconds is 0.700 or more and 1.000 or less. The amounts of silicon atoms M _A and M _B were measured by analyzing the surface of the silane coupling agent layer 3 by fluorescent X-ray analysis.

The amount of silicon atoms contained in the silane coupling agent layer 3 may be reduced by washing with water, but in the surface-treated copper foil according to this embodiment, the amount of silicon atoms contained in the silane coupling agent layer 3 may be reduced by washing with water as described above. few. This means that in the surface-treated copper foil according to the present embodiment, the silanol groups of the silane coupling agent are sufficiently dehydrated and condensed (that is, silane coupling with the hydroxyl groups present on the surface of the copper foil base 1). The silanol groups of the agent are dehydrated and condensed to form a metalloxane bond, and the silanol groups of the silane coupling agent are dehydrated and condensed to form a siloxane bond), and the residual silanol in the silane coupling agent layer 3 This means that the amount of groups is small.

Due to such a configuration, the surface-treated copper foil according to this embodiment has excellent moisture resistance and discoloration resistance. Therefore, the surface-treated copper foil according to this embodiment has high adhesion to the resin base material even if the surface of the copper foil base 1 has low roughness. Moreover, even when the resin base material is a base material formed of a low dielectric resin, the adhesion between the surface-treated copper foil and the resin base material is high. Therefore, the surface-treated copper foil according to this embodiment can be suitably used for manufacturing copper-clad laminates and printed wiring boards for high-frequency circuits. Moreover, the surface-treated copper foil according to this embodiment can be suitably used for manufacturing copper-clad laminates and printed wiring boards to be mounted on electronic devices used in harsh environments.

As described above, the surface-treated copper foil according to the present embodiment can be used to manufacture copper-clad laminates, printed wiring boards, and the like that have excellent adhesion between the surface-treated copper foil and the resin base material. Therefore, the surface-treated copper foil according to this embodiment can be suitably used for manufacturing copper-clad laminates, printed wiring boards, and the like.
That is, the copper-clad laminate according to the present embodiment includes the surface-treated copper foil according to the present embodiment and a resin base material bonded to the surface-treated copper foil. If the surface-treated copper foil according to this embodiment is used, a copper-clad laminate with excellent adhesion between the surface-treated copper foil and the resin base material can be manufactured.

Moreover, the printed wiring board according to this embodiment includes the copper-clad laminate according to this embodiment. By using the surface-treated copper foil and copper-clad laminate according to this embodiment, it is possible to manufacture a printed wiring board with excellent adhesion between the surface-treated copper foil and the resin base material.
Note that examples of the resin forming the resin base material include epoxy resin, polyphenylene ether, phenol resin, bis(phenoxyphenoxy)benzene, polyimide, liquid crystal polymer, and fluororesin (eg, polytetrafluoroethylene).

Below, the surface-treated copper foil according to this embodiment will be explained in more detail.
(1) About the copper foil substrate The copper foil substrate 1, which is the raw material for the surface-treated copper foil according to the present embodiment, has a ten-point average roughness Rzjis of two surfaces before it is subjected to roughening treatment to roughen the surface. It is preferable that both of them are 1.5 μm or less. This ten-point average roughness Rzjis can be measured using a contact surface roughness measuring machine according to the method specified in JIS B0601:2001. If the ten-point average roughness Rzjis of the surface is 1.5 μm or less, transmission loss tends to be small.

(2) Regarding the anti-rust treatment layer When manufacturing the surface-treated copper foil according to this embodiment, the surface of the copper foil base 1 is treated with a silane coupling agent to provide a silane coupling agent layer 3. Before applying the coupling agent treatment, one or both of a rust prevention treatment to form a rust prevention treatment layer 2 on the surface of the copper foil base 1 and a roughening treatment to roughen the surface of the copper foil base 1 may be performed. good. When both rust prevention treatment and roughening treatment are performed, the roughening treatment is performed first and then the rust prevention treatment is performed. Here, the antirust treatment layer 2 will be explained, and the roughening treatment will be described later.

As mentioned above, since the rust prevention treatment is performed before applying the silane coupling agent treatment to the surface of the copper foil base 1, the rust prevention treatment layer 2 is provided between the copper foil base 1 and the silane coupling agent layer 3. (See Figure 1). This anti-rust treatment layer 2 is made of at least two metals selected from nickel (Ni), zinc (Zn), cobalt (Co), chromium (Cr), molybdenum (Mo), and tungsten (W), either singly or in an alloy. It is preferable to contain it as

(3) Regarding the silane coupling agent layer When manufacturing the surface-treated copper foil according to this embodiment, at least one surface of the copper foil base 1 is treated with a silane coupling agent to form a layer with a silane coupling agent. A silane coupling agent layer 3 is provided. Examples of silane coupling agent treatments include the following.

A treatment solution is prepared by diluting the silane coupling agent with a solvent such as water or alcohol, and the copper foil substrate 1 is immersed in the treatment solution.The treatment solution is applied to the surface of the copper foil substrate 1. A film of the treatment liquid is formed on the surface of the copper foil substrate 1 by a method such as spraying the treatment liquid onto the surface. Then, by heat-treating the copper foil substrate 1 on which a film of the treatment liquid has been formed on the surface, the solvent of the treatment liquid is volatilized, and the copper forming the copper foil substrate 1 is reacted with the silane coupling agent. A silane coupling agent layer 3 is fixed on the surface of the base 1.

When manufacturing the surface-treated copper foil according to this embodiment, heat treatment is performed not only to volatilize the solvent of the treatment liquid but also to reduce the amount of residual silanol groups in the silane coupling agent layer 3. is important. An example of such heat treatment is a two-stage heat treatment. That is, in the first heat treatment, the solvent of the treatment liquid is volatilized, and in the second heat treatment, the silanol groups of the silane coupling agent are reacted (dehydrated and condensed) so that the amount of residual silanol groups in the silane coupling agent layer 3 is reduced. ). An example of a two-stage heat treatment is shown below.

First, the copper foil substrate 1 with a treatment liquid film formed on its surface is placed in a roll-to-roll type heating furnace and subjected to primary heat treatment. The temperature conditions for the first heat treatment are preferably 80°C or more and 120°C or less. If the temperature is 80° C. or higher, the solvent in the treatment liquid can be sufficiently dried. Further, if the temperature is 120° C. or lower, appearance abnormalities such as wrinkles are less likely to occur in the copper foil substrate 1.

The heat treatment time of the first heat treatment is preferably 5 seconds or more and 30 seconds or less. If the heat treatment time is 5 seconds or more, there is no need to perform the heat treatment at an extremely high temperature, so that appearance abnormalities such as wrinkles are less likely to occur in the copper foil substrate 1. Further, if the heat treatment time is 30 seconds or less, productivity is high and production equipment such as a heating device is likely to be practical.

Next, a second heat treatment is performed. Although the solvent of the treatment liquid is dried by the first heat treatment, the dehydration and condensation of the silanol groups is insufficient, and many residual silanol groups remain. The copper foil base 1 that has undergone the first heat treatment is wound up into a coiled state, and the copper foil base 1 in the coiled state is subjected to a second heat treatment in, for example, a batch furnace. In the second heat treatment, it is preferable to heat the copper foil substrate 1 under an inert gas atmosphere or a reducing atmosphere.

The temperature conditions for the second heat treatment are preferably 210°C or more and 300°C or less. In particular, it is important to perform the second heat treatment at a temperature higher than the maximum temperature at which the surface-treated copper foil and resin base material are laminated and hot-pressed to produce a copper-clad laminate. As mentioned above, dehydration condensation of residual silanol groups occurs when the surface-treated copper foil and the resin base material are stacked and hot-pressed, which is considered to be the cause of deterioration of moisture resistance. Therefore, by performing the second heat treatment at a temperature higher than the maximum temperature of hot pressing, it is possible to reduce the amount of residual silanol groups in the second heat treatment and suppress dehydration condensation of the remaining silanol groups during hot pressing. .

The hot press temperature of the base material made of low dielectric resin is often 190°C or more and 250°C or less. For example, in the case of MEGTRON7N, an ultra-low transmission loss and high heat-resistant multilayer board material manufactured by Panasonic Corporation, the hot press temperature is specified as a workpiece temperature of 195° C. or higher.
When the temperature of the second heat treatment is 210° C. or higher, sufficient dehydration condensation of the remaining silanol groups occurs, so that excellent moisture resistance is likely to be obtained. Further, if the temperature of the second heat treatment is 300° C. or lower, decomposition of the silane coupling agent is unlikely to occur.
The heat treatment time of the second heat treatment is preferably 60 minutes or more and 180 minutes or less. If the heat treatment time is 60 minutes or more, dehydration condensation of the remaining silanol groups is likely to occur sufficiently. Further, if the heat treatment time is 180 minutes or less, productivity is high.

It is also possible to sufficiently cause dehydration condensation of the remaining silanol groups by a method other than such two-step heat treatment. For example, there are a method of performing heat treatment at a high temperature for a long time in one stage, a method of performing heat treatment in three or more stages, a method of using a silane coupling agent that causes dehydration condensation of silanol groups to proceed at a lower temperature and a short time. In a method in which the heat treatment is performed in one step, if the temperature is too low, the dehydration condensation of the remaining silanol groups will be insufficient. On the other hand, if the temperature is too high, the silane coupling agent tends to become porous because the solvent volatilization and the dehydration condensation of the remaining silanol groups proceed simultaneously.As a result, many residual silanol groups tend to remain, and the silane coupling agent Moisture can easily penetrate into the layer.

Regardless of which method is used, it is important to ensure that any remaining silane coupling agent layer 3 remains before the surface-treated copper foil and resin base material are stacked and hot pressed to produce a copper-clad laminate. The purpose is to reduce the amount of silanol groups to a predetermined amount or less. The amount of residual silanol groups will be explained.
The amount of residual silanol groups in the silane coupling agent layer 3 is evaluated by measuring the amount of silicon atoms contained in the silane coupling agent layer 3 before and after washing with water. That is, the amount M _A of silicon atoms contained in the silane coupling agent layer 3 before washing with pure water, and the amount M A of silicon atoms contained in the silane coupling agent layer 3 after washing with pure water for 30 seconds and drying. The amount of residual silanol groups is evaluated based on the ratio M _B /M _A to the amount M _B of silicon atoms.

The larger the value of the ratio M _B /M _A is, the smaller the amount of residual silanol groups is, which means that the silanol groups of the silane coupling agent are dehydrated and condensed to form more metaloxane bonds and siloxane bonds. The ratio M _B /M _A needs to be 0.700 or more and 1.000 or less, and preferably 0.750 or more and 1.000 or less.

If the ratio M _B /M _A is 0.700 or more, the amount of residual silanol groups in the silane coupling agent layer 3 is sufficiently small, and the surface-treated copper foil has excellent moisture resistance and discoloration resistance. By definition, the ratio M _B /M _A cannot be larger than 1.000, but the closer it is to 1.000, the better the moisture resistance and discoloration resistance of the surface-treated copper foil are.

As a method of washing the silane coupling agent layer 3 with water, a method of immersing the surface-treated copper foil in pure water for 30 seconds is used. The temperature of pure water at this time is 25°C.
Note that the amounts M _A and M _B of silicon atoms contained in the silane coupling agent layer 3 were measured by analyzing the surface of the silane coupling agent layer 3 by fluorescent X-ray analysis. Further, the units of the amounts M _A and M _B of silicon atoms are "mg/dm ² ".

The amount M _A of silicon atoms contained in the silane coupling agent layer 3 before being washed with pure water is preferably 0.0020 mg/dm ² or more and 0.0276 mg/dm ² or less. When the amount M _A of silicon atoms contained in the silane coupling agent layer 3 is 0.0020 mg/dm ² or more, the effect of improving adhesion by the silane coupling agent is likely to be obtained. On the other hand, if the amount _MA of silicon atoms contained in the silane coupling agent layer 3 is 0.0276 mg/dm ² or less, appearance abnormalities such as unevenness are unlikely to occur in the surface-treated copper foil.

Silane coupling agents used for forming the silane coupling agent layer 3 include glycidoxy groups (C ₃ H ₅ O ₂ -), mercapto groups, amino groups, azole groups, acryloyl groups, vinyl groups, and epoxy groups (C Examples include silane coupling agents having at least one functional group among ₂ H ₃ O-). One type of silane coupling agent may be used alone, or two or more types may be used in combination.

Specific examples of silane coupling agents include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl )-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-vinylbenzyl-2-aminoethyl-3 -Aminopropyltrimethoxysilane, N-(p-vinylbenzyl)-N-(trimethoxysilylpropyl)ethylenediamine, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycid Xypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, Bis[3-(triethoxysilyl)propyl]disulfide, Bis[3-( triethoxysilyl)propyl]tetrasulfide, vinyltriacetoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, vinyltrichlorosilane, allyltrimethoxysilane, diallyldimethylsilane, 3-methacryloxypropyltrimethoxy Silane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercapto Propylmethyldimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, N-(1,3-dimethylbutylidene)-3-aminopropyltriethoxysilane, p-styryltrimethoxysilane, 3- Examples include ureidopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, and 3-isocyanatepropyltriethoxysilane.

As mentioned above, the silane coupling agent layer 3 can be formed using a treatment liquid in which a silane coupling agent is diluted with a solvent, but the concentration of the silane coupling agent in the treatment liquid is 1 mg/L or more and 30 mg. /L or less is preferable. If the concentration of the silane coupling agent in the treatment solution is 1 mg/L or more, a sufficient amount of the silane coupling agent can be attached to the surface of the copper foil substrate 1, so that the surface-treated copper foil and the resin substrate The adhesion of materials tends to be high. On the other hand, if the concentration of the silane coupling agent in the treatment liquid is 30 mg/L or less, abnormal appearance such as unevenness is unlikely to occur when the treatment liquid is applied to the surface of the copper foil substrate 1.

(4) Regarding roughening treatment The copper foil substrate 1 may be subjected to roughening treatment before being subjected to rust prevention treatment or silane coupling agent treatment. A typical example of roughening treatment is copper roughening plating. As the roughening plating solution for copper roughening plating, a copper sulfate plating solution can be used.

The sulfuric acid concentration of the copper sulfate plating solution is preferably 50 g/L or more and 250 g/L or less, more preferably 70 g/L or more and 200 g/L or less. If the sulfuric acid concentration of the copper sulfate plating solution is 50 g/L or more, the electrical conductivity will be high and the electrodeposition of the roughening particles onto the copper foil substrate 1 will be good. Furthermore, if the sulfuric acid concentration of the copper sulfate plating solution is 250 g/L or less, corrosion of plating equipment by sulfuric acid is unlikely to occur.

The copper concentration of the copper sulfate plating solution is preferably 6 g/L or more and 100 g/L or less, more preferably 10 g/L or more and 50 g/L or less. If the copper concentration of the copper sulfate plating solution is 6 g/L or more, the electrodeposition of the roughening particles onto the copper foil substrate 1 will be good. Further, if the copper concentration of the copper sulfate plating solution is 100 g/L or less, copper roughening plating can be performed without using a large current.

An organic additive or an inorganic additive may be added to the roughening plating solution. For example, when a high-molecular polysaccharide is added to a roughening plating solution, the diffusion-limiting current density is reduced, and roughening particles are likely to be generated even at a lower current density. Further, by adding a salt or noble metal ion that is less water soluble than copper sulfate, the number of roughened copper particles can be increased.

The current density in roughening plating is preferably 5 A/dm ² or more and 120 A/dm ² or less, more preferably 30 A/dm ² or more and 100 A/dm ² or less. When the current density is 5 A/dm ² or more, copper roughening plating does not take a long time and productivity is high. Further, if the current density is 120 A/dm ² or less, the electrodeposition of the roughening particles onto the copper foil substrate 1 will be good.

After the roughening treatment, a cover plating treatment may be performed to cover the roughened particles and improve the adhesion between the roughened particles and the copper foil substrate 1. Copper sulfate plating solution is also used when performing cover plating. Furthermore, the uniform electrodeposition of the roughening particles may be improved by repeating the roughening plating and cover plating processes multiple times.

Furthermore, the roughening treatment may be performed by a method other than roughening plating. Examples of this include roughening treatment by plating with a metal different from the copper forming the copper foil substrate 1 or alloy plating, roughening treatment by etching treatment, and oxidizing the surface of the copper foil substrate 1 with an oxidizing agent or atmosphere. Examples include roughening treatment by oxidizing the surface of the copper foil substrate 1 and then reducing it. These roughening treatments may be performed alone or in combination of two or more.

The roughening treatment may be applied to only one of the two sides of the copper foil base 1, or may be applied to both sides. The surface to be treated with a silane coupling agent later is subjected to a roughening treatment to form a roughened surface. That is, in the surface-treated copper foil according to this embodiment, the surface on which the silane coupling agent layer 3 is provided among the two surfaces of the copper foil base 1 may be a roughened surface subjected to a roughening treatment. The volume parameter Vvc of the roughened surface may be 0.10 mL/m ² or more and 0.50 mL/m ² or less.

Furthermore, in the surface-treated copper foil according to the present embodiment, one of the two surfaces of the copper foil base is a roughened surface that has been subjected to a roughening treatment, and is treated with a silane coupling agent to be treated with silane. The structure may be such that the coupling agent layer 3 is provided, and the other surface is not subjected to the roughening treatment and the silane coupling agent layer 3 is not provided. The volume parameter Vvc of the roughened surface, which is one of the surfaces, is 0.10 mL/m ² or more and 0.50 mL/m ² or less, and the other surface, which is the non-roughened surface (hereinafter referred to as The volume parameter Vmc (also referred to as "non-roughening treated surface") may be 0.12 mL/m ² or more and 0.35 mL/m ² or less.
Furthermore, in the surface-treated copper foil according to the present embodiment, the arithmetic mean height Sa of the roughened surface may be 0.05 μm or more and 0.35 μm or less.

(5) Regarding the volume parameter Vvc of the roughened surface As for the roughened surface, it is preferable that the volume parameter Vvc specified in ISO25178 is 0.10 mL/m ² or more and 0.50 mL/m ² or less. The volume parameter Vvc is the volume of the space in the core portion, which is the portion between the position of 10% and the position of 90% of the load area ratio in the load curve measured according to ISO25178.

When the height of the roughening particles on the roughening treatment surface is constant, the value of the volume parameter Vvc increases as the volume occupied by the gap space increases. The surface-treated copper foil in a coiled state has one surface and the other surface overlapping each other. Therefore, it can be understood that the volume parameter Vvc reflects the amount of air that can be held between the surface-treated copper foils in a coiled state.

The present inventors have determined that by controlling the volume parameter Vvc within the above range, dehydration condensation of residual silanol groups and discharge of moisture to the outside of the coil can be achieved when the copper foil substrate 1 in a coiled state is subjected to secondary heat treatment. It has been found that this can be carried out effectively and the moisture resistance is further improved. In addition, by controlling the volume parameter Vvc within the above range, a large amount of dry air can be contained between the surface-treated copper foils when the surface-treated copper foils are stored in a coiled state. It has been found that it is possible to prevent the formation of and effectively suppress discoloration.

If the volume parameter Vvc is 0.10 mL/m2 or ^more , the space between the surface-treated copper foils will be sufficiently large, so the copper foil base 1 in the coiled state is subjected to secondary heat treatment. In this case, the moisture generated by dehydration condensation of the remaining silanol groups is easily discharged from the coil effectively, and discoloration is less likely to occur during storage. On the other hand, if the volume parameter Vvc is 0.50 mL/m ² or less, abnormalities such as shedding of roughening particles and misalignment of the coil are unlikely to occur.

(6) Regarding the volume parameter Vmc of the non-roughened surface As for the non-roughened surface, the volume parameter Vmc defined in ISO25178 is preferably 0.12 mL/m ² or more and 0.35 mL/m ² or less. The volume parameter Vmc is the volume of the core portion which is the portion between the position of 10% load area ratio and the position of 90% in the load curve obtained by measurement according to ISO25178. When the height of the unevenness on the non-roughened surface is constant, the larger the volume occupied by the unevenness on the non-roughened surface, the larger the value of the volume parameter Vmc becomes.

By controlling the volume parameter Vmc of the non-roughened surface within the above range, the present inventors have achieved dehydration condensation of the remaining silanol groups and removal of moisture when the copper foil substrate 1 in a coiled state is subjected to the second heat treatment. It has been found that the discharge to the outside of the coil is effectively carried out and the moisture resistance is further improved. Further, by combining controlling the volume parameter Vmc of the non-roughened surface within the above range and controlling the volume parameter Vvc of the roughened surface within the above range, there is an effect of further improving moisture resistance. I found out.

If the volume parameter Vmc is 0.12 mL/m ² or more, slips and scratches are less likely to occur during transportation of the surface-treated copper foil. On the other hand, if the volume parameter Vmc is 0.35 mL/ ^m2 or less, when the surface-treated copper foil is stored in a coiled state, there is less contact between the non-roughened surface and the roughened surface, and the roughened particles is less likely to deform or fall off.

(7) Regarding the arithmetic mean height Sa of the roughened surface The arithmetic mean height Sa of the roughened surface is preferably 0.05 μm or more and 0.35 μm or less. The arithmetic mean height Sa is defined in ISO25178. When the arithmetic mean height Sa of the roughened surface is 0.05 μm or more, the adhesion between the surface-treated copper foil and the resin base material is excellent. Further, if the arithmetic mean height Sa of the roughened surface is 0.35 μm or less, transmission loss tends to be small. Therefore, if a printed wiring board is manufactured using the surface-treated copper foil according to this embodiment, the transmission loss will be small even when a high frequency signal is transmitted to the circuit of the obtained printed wiring board.

〔Example〕
The present invention will be explained in more detail by showing Examples and Comparative Examples below.
(A) Copper foil base As a copper foil base that is a raw material for manufacturing the surface-treated copper foils of Examples 1 to 18 and Comparative Examples 1 to 6, an electrolytic copper foil (double-sided glossy foil) with a thickness of 18 μm was prepared. . The Rzjis of the electrolytic deposition end surface (matte surface) of this electrolytic copper foil is 1.0 μm, and the Rzjis of the electrolytic deposition start surface (shiny surface) is 0.8 μm.

(B) Roughening treatment For Examples 1 to 17 and Comparative Examples 1 to 6, copper roughening plating was applied to the electrolytic deposition end surface of the electrolytic copper foil, and to the electrolytic deposition starting surface of the electrolytic copper foil for Example 18. A roughened copper foil was produced by performing a roughening treatment and then performing a cover plating treatment. The conditions for copper roughening plating and the conditions for cover plating are as follows.

<Conditions for copper roughening plating>
Concentration of copper sulfate pentahydrate in plating bath: 35 g/L in terms of copper (atoms)
Concentration of sulfuric acid in plating bath: 140g/L
Plating bath temperature: 27℃
Current density: 55A/dm ²
Processing time: 4 seconds

<Conditions for cover plating treatment>
Concentration of copper sulfate pentahydrate in plating bath: 120 g/L in terms of copper (atoms)
Concentration of sulfuric acid in plating bath: 90g/L
Current density: 10A/dm ²
Processing time: 6 seconds

(C) Formation of rust prevention treatment layer Next, the roughened surface is coated with nickel plating, alkali zinc plating, acid chromate treatment, Cu-Ni-Co plating, Cu-Mo plating, and Cu-W plating. By performing one or more types of treatments, a rust-proofing layer was formed on the roughened surface. See Tables 1 and 2 for the structure of the rust prevention treatment layer.

<Nickel plating conditions>
Concentration of nickel in plating bath: 40g/L
Concentration of boric acid (H ₃ BO ₃ ) in the plating bath: 5 g/L
Plating bath temperature: 20℃
Plating bath pH: 3.5
Current density: 0.2A/dm ²
Processing time: 10 seconds

<Conditions for alkaline zinc plating>
Concentration of zinc in plating bath: 5g/L
Concentration of sodium hydroxide in plating bath: 30g/L
Plating bath temperature: 25℃
Current density: 0.8A/dm ²
Processing time: 7 seconds

<Conditions for acid chromate treatment>
Concentration of chromium in plating bath: 5g/L
Plating bath temperature: 40℃
Plating bath pH: 3.2
Current density: 5A/ ^dm2
Processing time: 4 seconds

<Cu-Ni-Co plating conditions>
Copper concentration in plating bath: 15g/L
Concentration of nickel in plating bath: 13g/L
Cobalt concentration in plating bath: 10g/L
Concentration of sulfuric acid in plating bath: 20g/L
Plating bath temperature: 25℃
Current density: 10A/dm ²
Processing time: 2 seconds

<Cu-Mo plating conditions>
Copper concentration in plating bath: 45g/L
Molybdenum concentration in plating bath: 0.5g/L
Concentration of sulfuric acid in plating bath: 100g/L
Plating bath temperature: 27℃
Current density: 10A/dm ²
Processing time: 4 seconds

<Cu-W plating conditions>
Copper concentration in plating bath: 45g/L
Concentration of tungsten in plating bath: 0.5g/L
Concentration of sulfuric acid in plating bath: 100g/L
Plating bath temperature: 27℃
Current density: 7A/dm ²
Processing time: 4 seconds

(D) Silane coupling agent treatment Finally, a silane coupling agent treatment was performed, and a silane coupling agent layer was laminated on the rust prevention treatment layer to obtain a surface-treated copper foil. To be more specific, the electrolytic copper foil with the anti-rust treatment layer is immersed in a treatment solution obtained by diluting the silane coupling agent with a solvent, and then heat-treated to form a silane cup on the anti-corrosion layer. A ring agent layer was laminated. The type of silane coupling agent and the concentration of the silane coupling agent in the treatment liquid are as shown in Tables 1 and 2.

The silane coupling agent described as "glycidoxy" in Tables 1 and 2 is the silane coupling agent KBM-403 (3-glycidoxypropyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd. Furthermore, the silane coupling agent described as "amino A" in Table 1 is the silane coupling agent KBM-903 (3-aminopropyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd. Furthermore, the silane coupling agent described as "acryloyl" in Tables 1 and 2 is the silane coupling agent KBM-5103 (3-acryloxypropylmethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd.

Furthermore, the silane coupling agent described as "mercapto" in Tables 1 and 2 is the silane coupling agent KBM-803 (3-mercaptopropyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd. Furthermore, the silane coupling agent described as "vinyl" in Tables 1 and 2 is the silane coupling agent KBM-1003 (vinyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd. Furthermore, the silane coupling agent described as "epoxy" in Tables 1 and 2 is the silane coupling agent KBM-303 (2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd. It is. Furthermore, the silane coupling agent described as "amino B" in Table 2 is the silane coupling agent KBM-603 (N-(2-aminoethyl)-3-aminopropyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd. ).

The details of the heat treatment in the silane coupling agent treatment are as follows. First, an electrolytic copper foil with a treatment liquid film formed on its surface was placed in a roll-to-roll heating furnace to undergo primary heat treatment and dry the solvent. The conditions (temperature and time) of the first heat treatment are as shown in Tables 1 and 2.
Next, the electrolytic copper foil that had undergone the first heat treatment was wound up into a coil, and the coiled electrolytic copper foil was subjected to a second heat treatment in a batch furnace. The second heat treatment was performed under a reducing atmosphere. The conditions (temperature and time) for the second heat treatment are as shown in Tables 1 and 2.

(E) Measurement of the amount of silicon atoms contained in the silane coupling agent layer By analyzing the surface of the silane coupling agent layer of the surface-treated copper foil by fluorescent X-ray analysis, the amount of silicon atoms contained in the silane coupling agent layer was determined. The amount of silicon atoms contained in the material was measured. For this measurement, a scanning X-ray fluorescence spectrometer ZSX Primus IV manufactured by Rigaku Co., Ltd. was used, and the amount of silicon atoms was quantified using a calibration curve obtained using a standard sample with a known amount of silicon atoms. .

Moreover, this measurement was performed before and after washing with water. Specifically, first, the surface-treated copper foil that had not been washed with pure water was analyzed to obtain the amount _MA of silicon atoms contained in the silane coupling agent layer. Next, the surface-treated copper foil after measuring the amount of silicon atoms M _A was washed with pure water for 30 seconds, dried, and then analyzed. Silane coupling of the surface-treated copper foil after washing with pure water for 30 seconds The amount M _B of silicon atoms contained in the agent layer was obtained. Then, the ratio M _B /M _A was calculated. The results are shown in Tables 1 and 2.

(F) Measurement of volume parameters Vvc, Vmc and arithmetic mean height Sa The volume parameter Vvc and arithmetic mean height Sa of the roughened surface of the surface-treated copper foil and the volume parameter Vmc of the non-roughened surface were measured by Co., Ltd. Measurement was performed according to ISO25178 using confocal laser microscopes VK-X1050 and VK-X1000 manufactured by Keyence. The results are shown in Tables 1 and 2. The numerical values shown in Tables 1 and 2 are the average values of the measured values at three arbitrary points for each of Vvc, Vmc, and Sa.

The objective lens magnification of the confocal laser microscope is 100 times, the scan mode is laser confocal, the measurement size is 2048 x 1536, the measurement quality is High Precision, and the pitch is 0.08 μm.
Further, calculations of Vvc, Vmc, and Sa were performed under the filter processing and calculation conditions shown below.
Image processing: Smoothing processing, 3×3, median S filter: None F-operation: Plane tilt correction L filter: 0.025 μm
Area to be calculated: 100μm x 100μm
Load area ratio in load curve: 10% and 90%

(G) Moisture resistance evaluation A resin base material was placed on the silane coupling agent layer of the surface-treated copper foils of Examples 1 to 18 and Comparative Examples 1 to 6, and heated and pressed at a maximum temperature of 210°C. A copper-clad laminate was produced using the following methods. The resin base material used was MEGTRON7N, an ultra-low transmission loss, high heat-resistant multilayer board material manufactured by Panasonic Corporation. The obtained copper-clad laminate was subjected to copper chloride etching to produce a printed wiring board having circuit wiring with a width of 1 mm.

The obtained printed wiring board was heated in boiling water for 5 hours, and a peel test was conducted within 2 hours after wiping off the moisture. This peel test was conducted based on the method specified in JIS C6481:1996. That is, using a Tensilon tester manufactured by Toyo Seiki Seisakusho Co., Ltd., the circuit wiring part (copper foil part) of the printed wiring board was pulled in a 90 degree direction at a speed of 50 mm/min at room temperature to test the resin base material. It was peeled off from. Moisture resistance was evaluated based on the obtained peel strength.

The results are shown in Tables 1 and 2. The evaluation criteria for moisture resistance are as follows.
AA (pass): Peel strength is 0.60 N/mm or more A (pass): Peel strength is 0.55 N/mm or more and less than 0.60 N/mm B (pass): Peel strength is 0.50 N/mm or more and 0. Less than 55 N/mm C (fail): Peel strength is less than 0.50 N/mm

(H) Evaluation of color fastness The surface-treated copper foils (width 600 mm, length 2000 m) of Examples 1 to 18 and Comparative Examples 1 to 6 were wound to form a coil at a constant temperature of 70°C and relative humidity 80% RH. An accelerated long-term storage test was conducted under a constant humidity environment. Visual confirmation was performed every 24 hours over a length of 3 m from the outer periphery of the coil, and the length of time until obvious discoloration was observed was measured.

The results are shown in Tables 1 and 2. The evaluation criteria for color fastness are as follows.
AA (pass): No obvious discoloration was observed after 360 hours.
A (pass): Clear discoloration was observed after 240 hours or more and less than 360 hours.
B (pass): Clear discoloration was observed after 168 hours or more and less than 240 hours.
C (fail): Clear discoloration was observed in less than 168 hours.

As can be seen from Tables 1 and 2, the surface-treated copper foil of each example has a ratio M _B /M _A in the range of 0.700 to 1.000, so it has excellent moisture resistance and excellent color fastness. It had both sexes.
On the other hand, the surface-treated copper foil of Comparative Example 1 was the same as Example 2 except that it was not subjected to secondary heat treatment, but the ratio M _B /M _A was less than 0.700. . Therefore, since it has a large amount of residual silanol groups, it has poor moisture resistance and can be said to be a conventional copper foil for general high-frequency circuits.

The surface-treated copper foil of Comparative Example 2 was the same as Example 3 except that the second heat treatment was not performed, but the ratio M _B /M _A was less than 0.700. Therefore, since it had a large amount of residual silanol groups, it had poor discoloration resistance.
The surface-treated copper foil of Comparative Example 3 had a ratio M _B /M _A of less than 0.700 because the temperature and time of the second heat treatment were low and short. Therefore, since it had a large amount of residual silanol groups, it was inferior in moisture resistance and discoloration resistance.

The surface-treated copper foil of Comparative Example 4 was obtained by subjecting the roughening-treated copper foil to the silane coupling agent treatment and heat treatment described in Examples 2-8 of Patent Document 4. The copper foil described in Patent Document 4 is a copper foil for a lithium ion battery current collector, but it differs from the above in that the organic film thickness is measured before and after the cleaning operation of the copper foil treated with a silane coupling agent. It is similar to the surface-treated copper foil according to this embodiment. Comparative Examples 4 and 5 are simple combinations of the content disclosed in Patent Document 4 and existing copper foil for printed wiring boards.

The surface-treated copper foil of Comparative Example 4 had a ratio M _B /M _A of less than 0.700. Therefore, since it had a large amount of residual silanol groups, it was inferior in moisture resistance and discoloration resistance. This is presumed to be because the heating conditions for the heat treatment were insufficient, resulting in a large number of residual silanol groups. The organic coating thickness measurement by X-ray photoelectron spectroscopy described in Patent Document 4 calculates the organic coating thickness from the relationship not only with silicon atoms but also with carbon atoms, so A quantitative comparison cannot be made with the measurement of the ratio M _B /M _A.

The surface-treated copper foil of Comparative Example 5 was the same as Comparative Example 4 except that it was subjected to nickel plating, alkali zinc plating, and acid chromate treatment as antirust treatments, but the ratio M _B /M _A was 0. It was less than .700. Therefore, since it had a large amount of residual silanol groups, it was inferior in moisture resistance and discoloration resistance.

The surface-treated copper foil of Comparative Example 6 was obtained by subjecting the roughened copper foil to the rust prevention treatment, silane coupling agent treatment, and heat treatment described in Example 1 of Patent Document 5. The ratio M _B /M _A was less than 0.700. Therefore, since it had a large amount of residual silanol groups, it was inferior in moisture resistance and discoloration resistance.

Although Patent Document 5 states that the moisture resistance is good, the resin base material used is a general glass epoxy base material and is not used for high frequency circuits, so the roughening treatment is also different from the conventional roughening treatment. It is assumed that a roughening treatment has been applied. Furthermore, the heating time in boiling water when evaluating moisture resistance was also shorter than in the above Examples and Comparative Examples. Therefore, the surface-treated copper foil of Comparative Example 6 cannot solve the problems to be solved by the present invention.

1... Copper foil base 2... Antirust treatment layer 3... Silane coupling agent layer

Claims (9)

comprising a copper foil base and a silane coupling agent layer provided on at least one surface of the copper foil base and formed of a silane coupling agent,
The ratio of the amount M _A of silicon atoms contained in the silane coupling agent layer to the amount M _B of silicon atoms contained in the silane coupling agent layer after washing with pure water for 30 seconds M _B /M _A is 0.700 or more and 1.000 or less,
The amounts M _A and M _B of the silicon atoms are measured by analyzing the surface of the silane coupling agent layer by X-ray fluorescence analysis,
Of the two surfaces of the copper foil substrate, the surface on which the silane coupling agent layer is provided is a roughened surface that has been subjected to a roughening treatment, and the volume parameter Vvc of the roughened surface is 0.10 mL/ m ² or more and 0.50 mL/m ² or less, and the volume parameter Vvc is a core portion that is a portion between a load area ratio position of 10% and a position of 90% in a load curve obtained by measurement according to ISO 25178. The volume of space is surface treated copper foil. A rust prevention treatment layer is provided between the copper foil base and the silane coupling agent layer, and the rust prevention treatment layer contains at least two metals selected from nickel, zinc, cobalt, chromium, molybdenum, and tungsten. The surface-treated copper foil according to claim 1, containing the copper foil alone or as an alloy. The surface-treated copper foil according to claim 1 or 2, wherein the amount M _A of the silicon atoms is 0.0020 mg/dm ² or more and 0.0276 mg/dm ² or less. One of the two surfaces of the copper foil substrate is a roughened surface that has been subjected to a roughening treatment, and the silane coupling agent layer is provided, and the volume parameter of the roughened surface is Vvc is 0.10 mL/m ² or more and 0.50 mL/m ² or less, the other side is not subjected to roughening treatment, and the silane coupling agent layer is not provided, and the volume is The surface-treated copper foil according to any one of claims 1 to 3, wherein the parameter Vmc is 0.12 mL/m ² or more and 0.35 mL/m ² or less. The surface-treated copper foil according to any one of claims 1 to 4, wherein the arithmetic mean height Sa of the roughened surface is 0.05 μm or more and 0.35 μm or less. The surface-treated copper foil according to any one of claims 1 to 5, wherein the ratio M _B /M _A is 0.750 or more and 1.000 or less. Claims 1 to 6 , wherein the silane coupling agent is a silane coupling agent having at least one functional group selected from a glycidoxy group, a mercapto group, an amino group, an azole group, an acryloyl group, a vinyl group, and an epoxy group. The surface-treated copper foil according to any one of the items. A copper-clad laminate comprising the surface-treated copper foil according to any one of claims 1 to 7 and a resin base material bonded to the surface-treated copper foil. A printed wiring board comprising the copper-clad laminate according to claim 8 .

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