WO2021039370A1

WO2021039370A1 - Copper-clad laminate and method for producing same

Info

Publication number: WO2021039370A1
Application number: PCT/JP2020/030460
Authority: WO
Inventors: 展彰迎
Original assignee: 東洋鋼鈑株式会社
Priority date: 2019-08-29
Filing date: 2020-08-07
Publication date: 2021-03-04
Also published as: CN112449483B; CN118433993A; JPWO2021039370A1; KR20220052860A; CN112449483A; TW202117074A

Abstract

Provided are a copper-clad laminate 10 capable of ensuring high adhesion between a resin film 1 and a copper plating layer 2 while suppressing transmission loss when applied to a flexible circuit board, and a method for producing the same. [Problem] [Solution] The copper-clad laminate is characterized by including a resin film 1 having a relative permittivity of 3.5 or lower and a dielectric loss tangent of 0.008 or lower at a frequency of 10 GHz and an electroless copper plating layer 2 laminated on at least one surface of the resin film 1, the average surface roughness Ra of the resin film 1 being 1-150 nm at the plating layer side interface in contact with the electroless copper plating layer 2, and by the adhesive strength of the resin film 1 and the electroless copper plating layer 2 being 4.2 N/cm or higher.

Description

Copper-clad laminate and its manufacturing method

The present invention relates to a copper-clad laminate for a flexible circuit board mounted on a communication device or the like, and a method for manufacturing the same.

In recent years, the miniaturization and high performance of electronic devices have been remarkable, and the development of communication devices using radio waves such as mobile phones and wireless LANs has greatly contributed.
In particular, in recent years, as the capacity of information represented by big data by IoT has increased, the frequency of communication signals between electronic devices has been increasing, and the circuit boards mounted on such communication devices are transmitted in the high frequency region. A material with low loss (dielectric loss) is required.

Here, it is known that the dielectric loss generated in this circuit board is proportional to the product of three elements composed of "signal frequency", "square root of dielectric constant of substrate material" and "dielectric loss tangent". Therefore, in order to obtain the above-mentioned excellent dielectric properties, a material having both a dielectric constant and a dielectric loss tangent as low as possible is inevitably required.

In such a circuit board, the circuit is generally formed of a metal such as copper. The copper layer in this circuit board is formed by, for example, the laminating method shown in Patent Document 1, the casting method shown in Patent Document 2, the plating method shown in Patent Document 3, and the like.

Patent No. 6202905 Patent No. 5186266 JP-A-2002-256443

As mentioned above, in recent years, suppressing transmission loss in high-frequency communication has become an important development factor, and resin films with low transmission loss (hereinafter, also referred to as "low-dielectric film" or "low-dielectric resin film") are flexible. It is being used as a base material for circuit boards.
However, in the prior art including the above-mentioned patent documents, sufficient adhesion between the above-mentioned low-dielectric film and a metal layer (for example, a copper layer) for forming a circuit cannot be secured. For example, in the laminating method exemplified in Patent Document 1 and the casting method exemplified in Patent Document 2 described above, the interface between the copper layer and the low-dielectric film must be roughened, and the smoothness of the interface deteriorates, resulting in transmission loss. Will occur.

On the other hand, according to the plating method shown in Patent Document 3, a relatively good adhesion with the copper layer can be ensured for a resin film having a high dielectric constant. However, since the low-dielectric film has a relatively rigid molecular structure and little surface polarization, it has been a problem to secure an adhesive force when a copper layer is formed by a plating method. That is, when a low-dielectric film is used as a base material, roughening the interface has been widely performed as a conventional method for ensuring adhesion, but there is a trade-off relationship with transmission loss. Therefore, both of them have been desired.
For example, a sputtering method can be exemplified by a manufacturing method other than the above, but as a result of the manufacturing process becoming more complicated than the above method, many problems remain in terms of productivity and cost.

An object of the present invention is to solve the above-mentioned problems as an example. Specifically, the interface between a low-dielectric film as a base material and a metal layer for forming a circuit is smoothed in order to suppress transmission loss. An object of the present invention is to provide a copper-clad laminate capable of ensuring high adhesion while ensuring properties, and a method for producing the same.

In order to solve the above-mentioned problems, the copper-plated laminate according to the embodiment of the present invention includes (1) a resin film having a relative dielectric constant of 3.5 or less and a dielectric tangent of 0.008 or less at a frequency of 10 GHz. An electroless copper plating layer laminated on at least one surface of the resin film is included, and the average surface roughness Ra at the plating layer side interface of the resin film in contact with the electroless copper plating layer is 1 to 150 nm. It is characterized in that the adhesion strength between the resin film and the electroless copper plating layer is 4.2 N / cm or more.

In the copper-clad laminate according to (1) above, (2) the strength of the mass 121 by the time-of-flight mass spectrometry (TOF-SIMS) at the interface on the plating layer side of the resin film is 800 or more. Is preferable.

Further, in the copper-clad laminate according to (1) or (2) described above, it is preferable that (3) a hydroxyl group and / or a carboxyl group hydroxyl group is added to the interface on the plating layer side of the resin film.

Further, in the copper-clad laminate described in (3) above, it is preferable that the hydroxyl group is added in a larger amount than the carboxyl group at the interface on the plating layer side (4).

Further, in the copper-clad laminate according to any one of (1) to (4) above, (5) the resin film is any one of polyimide, modified polyimide, liquid crystal polymer, fluororesin, or a mixture thereof. Is preferable.

Further, in the copper-clad laminate according to any one of (1) to (5) above, (6) the electroless copper plating layer is a Cu—Ni alloy, and Ni in the electroless copper plating layer. The content is preferably 3 wt% or less.

Further, in the copper-clad laminate according to any one of (1) to (6) above, it is preferable that (7) the thickness of the electroless copper plating layer is in the range of 0.1 to 1.0 μm.

Further, in the copper-clad laminate according to any one of (1) to (7) described above, (8) any of Cu, Ni, Pd and Ag is provided at the interface of the resin film on the electroless copper plating layer side. It is preferable that a metal made of copper is present.

Further, it is preferable that the copper-clad laminate according to any one of (1) to (8) described above further contains (9) a protective layer formed on the electroless copper plating layer.

Further, in the copper-clad laminate according to any one of (1) to (9) described above, (10) the electroless copper plating layer is formed on both sides of the resin film and is passed through the resin film. It is preferable that the through hole has a hole and at least a part of the electroless copper plating layer is formed on the inner wall of the through hole.

Further, in order to solve the above-mentioned problems, the method for producing a copper-clad laminate in one embodiment of the present invention has (11) a specific dielectric constant of 3.5 or less and a dielectric tangent of 0.008 or less at a frequency of 10 GHz. A method for producing a copper-clad laminate produced by forming a copper-free copper plating layer on a resin film, which comprises a first surface modification step of imparting a carboxyl group and / or a hydroxyl group to the surface of the resin film. A second surface modification step of applying a charge to the surface to which the carboxyl group and / or a hydroxyl group is applied by a wet method, a catalyst adsorption step of adsorbing a catalyst on the surface to which the charge is applied, and the above. It includes a electroless copper plating step of forming an electroless copper plating layer on the surface on which a catalyst is adsorbed, and a heating step of heating the copper-clad laminate on which the electroless copper plating layer is formed. It is characterized by that.

In the method for producing a copper-clad laminate according to (11) above, it is preferable to use a mixed solution of an alkaline aqueous solution and alcohol in (12) the first surface modification step.

Further, in the method for producing a copper-clad laminate according to (12) above, (13) the alcohol is preferably aminoethanol.

Further, in the method for producing a copper-clad laminate according to any one of (11) to (13) described above, (14) the surface of the resin film is provided with more hydroxyl groups than the carboxyl groups. Is preferable.

Further, in the method for producing a copper-clad laminate according to any one of (11) to (14) above, the carboxyl group and / or the hydroxyl group was added in the second surface modification step (15). It is preferable that the positive charge is adsorbed on the surface and then the negative charge is adsorbed on the surface.

Further, in the method for producing a copper-clad laminate according to (15) above, (16) a cationic surfactant is added to the surface to adsorb the positive charge, and the anionic surfactant is used. It is preferable to add it to the surface to adsorb the negative charge.

Further, in order to solve the above-mentioned problems, the flexible circuit board according to the embodiment of the present invention is characterized in that a circuit made of the copper-clad laminate according to any one of (1) to (10) above is formed. And.

According to the present invention, it is possible to secure a high adhesion force without roughening the interface between the low-dielectric film and the electroless copper plating layer.

It is a schematic cross-sectional view which shows the copper-clad laminate 10 of this embodiment. It is a schematic diagram which shows the state of the interface between a resin film 1 and an electroless copper plating layer in the copper-clad laminate 10 of this embodiment. It is a schematic diagram which shows the through hole H in the copper-clad laminate 10 of this embodiment. It is a figure which shows the flow of the manufacturing method of the copper-clad laminate 10 of this embodiment. It is a schematic cross-sectional view which shows the copper-clad laminate 20 of this embodiment.

Hereinafter, the copper-clad laminate 10 of the present embodiment will be described with reference to FIG.
<Copper-clad laminate>
The copper-clad laminate 10 according to the present embodiment has a resin film 1 as a base material and an electroless copper plating layer 2 laminated on at least one surface of the resin film 1. In the present embodiment, it is preferable to use a so-called low-dielectric resin film having excellent electrical characteristics in the high frequency range as the resin film 1 as the base material.
Specifically, films such as known liquid crystal polymers, fluororesins, polyimide resins, modified polyimide resins, epoxy resins, polytetrafluoroethylene resins, and polyphenylene ether resins having lower dielectric losses are preferably used. These resins may be monopolymers or copolymers. Further, the resin may be used alone, or a plurality of resins may be blended and used as a hybrid product.

Specifically, as the electrical characteristics of the resin film 1 as the base material, it is preferable that the relative permittivity at a frequency of 10 GHz is 3.5 or less and the dielectric loss tangent is 0.008 or less.
The thickness of the resin film 1 is not particularly limited, but is preferably 5 μm to 100 μm in practical use.

Next, the electroless copper plating layer 2 laminated on at least one surface of the resin film 1 will be described. The electroless copper plating layer 2 in the present embodiment is preferably formed by electroless copper plating. That is, since the resin film 1 has an insulating property, a copper plating layer is formed by electroless plating. The electroless copper plating layer 2 may be a seed layer when a flexible circuit board is manufactured by a semi-additive method (SAP method or MSAP method), a subtractive method, a full additive method, or the like.

In the present embodiment, the electroless copper plating layer 2 may be the plating of Cu alone or the copper alloy plating containing a predetermined amount or more of copper. Examples of the copper alloy include Cu—Ni alloys, Cu—Zn alloys, Cu—Sn alloys, and the like.

When the electroless copper plating layer 2 is formed of a Cu—Ni alloy, the Ni content is 3 wt% or less, preferably 0.01 to 3 wt%, and more preferably 0.01 to 1. It is preferably .5 wt%, more preferably 0.01 to 0.3 wt%.
When the electroless copper plating layer 2 is a Cu—Ni alloy, it is considered that blistering is suppressed because the internal stress in the plating layer is also suppressed by containing Ni, which has a higher plating precipitation property than Cu. Therefore, it is preferable. On the other hand, if the amount of Ni in the Cu—Ni alloy exceeds 3 wt%, magnetism may be generated in the Cu circuit, which may increase the transmission loss and complicate the etchability at the time of forming the copper wiring. , The amount of Ni in the Cu—Ni alloy is preferably 3 wt% or less. Further, when the amount of Ni in the Cu—Ni alloy is less than 0.01 wt%, the plating precipitation property deteriorates.
As a method for measuring the Ni content in the electroless plating layer 2, for example, a known method such as a fluorescent X-ray apparatus (XRF) or a plasma emission spectroscopic analyzer (ICP) can be used.

In the present embodiment, as the electroless copper plating method for forming the electroless copper plating layer 2, a known method may be used as long as the electroless copper plating layer 2 having a predetermined thickness can be formed. The electroless copper plating method will be described in detail with reference to the items of the manufacturing method described later.
In the present embodiment, the thickness of the electroless copper plating layer 2 is preferably in the range of 0.1 μm to 1.0 μm from the viewpoint of manufacturing efficiency and cost.

When the thickness of the electroless copper plating layer 2 is less than 0.1 μm, it is not preferable because it may not function as a seed layer when the flexible circuit board is manufactured by the semi-additive method. On the other hand, when the thickness of the electroless copper plating layer 2 exceeds 1.0 μm, it may be difficult to form a fine circuit pattern when manufacturing a flexible circuit board, which is not preferable.

The thickness of the electroless copper plating layer 2 is more preferably 0.1 μm to 0.8 μm. In particular, in circuit formation by the SAP method, the shorter the etching time (thinner), the finer the pattern can be formed with less variation in impedance in the cross-sectional direction of the circuit.

In the copper-clad laminate 10 of the present embodiment, the average surface roughness Ra of the above-mentioned resin film 1 at the plating layer side interface in contact with the electroless copper plating layer 2 is 1 to 150 nm, preferably 20 to 150 nm. It is characterized by being. In particular, when the resin film 1 is a liquid crystal polymer, the average surface roughness Ra at the interface on the plating layer side in contact with the electroless copper plating layer 2 is preferably 20 to 150 nm. Further, particularly when the resin film 1 is a modified polyimide (MPI), the average surface roughness Ra at the interface on the plating layer side in contact with the electroless copper plating layer 2 is preferably 1 to 150 nm, more preferably. 1 to 50 nm is desirable.
The reason for this is as follows.

That is, in the copper-clad laminate of the present embodiment, it is desired that the transmission characteristics in the high frequency band above the GHz band are high in order to be suitably applicable to the circuit board corresponding to the high frequency as described above.

In general, it is known that the transmission signal propagates on the conductor surface as the frequency increases due to the skin effect, and the transmission loss increases as the conductor surface roughness increases. Therefore, in the present embodiment, in order to reduce the influence of transmission loss due to the skin effect, it is possible to reduce the average surface roughness Ra of the electroless copper plating layer 2 forming the wiring conductor at the interface with the resin film 1. preferable.

On the other hand, obtaining an anchor effect by roughening the interface between the electroless copper plating layer 2 and the resin film 1 has been widely practiced in order to ensure the adhesion between the metal and the resin. As described above, in the copper-clad laminate of the present embodiment, the roughness (adhesion) and the transmission loss are in a trade-off relationship between the electroless copper plating layer 2 and the resin film 1.
The present inventors have conducted diligent studies in order to achieve both of the above characteristics at a higher level. As a result, in the present embodiment, it has been found that it is preferable that the average surface roughness Ra of the above-mentioned resin film 1 at the interface on the plating layer side in contact with the electroless copper plating layer 2 is 1 nm to 150 nm. Is.

As a result of continuous studies by the present inventor, it has been concluded that when the average surface roughness Ra is less than 1 nm, favorable adhesion cannot be obtained between the electroless copper plating layer 2 and the resin film 1. .. On the other hand, when the average surface roughness Ra exceeds 150 nm, when the wiring conductor is formed on the circuit board by the electroless copper plating layer 2 as described above, it is preferable at high frequencies due to the transmission loss due to the skin effect. It may not be possible to obtain transmission characteristics.

In the present embodiment, as described above, the purpose is to achieve both roughness reduction (reduction of transmission loss) and adhesion between the electroless copper plating layer 2 and the resin film 1.
The specific adhesion strength between the electroless copper plating layer 2 and the resin film 1 is preferably 4.2 N / cm or more in practical use. Further, the above-mentioned adhesion strength is more preferably 5.0 N / cm or more, and further preferably 6.4 N / cm or more.

In the present embodiment, in order to ensure the above-mentioned adhesion between the electroless copper plating layer 2 and the resin film 1, it is preferable to have the following characteristics.
FIG. 2 schematically shows the state of the interface between the resin film 1 and the electroless copper plating layer in the copper-clad laminate 10 of the present embodiment. That is, it is preferable that a hydroxyl group and / or a carboxyl group is imparted to the interface of the resin film 1 on the electroless copper plating layer 2 side. This is due to the following reasons.

As shown in FIG. 1, in the copper-clad laminate 10 of the present embodiment, when the electroless copper plating layer 2 is formed on at least one surface of the resin film 1 by electroless plating, it is plated on the surface of the resin film 1. It is generally known that the metal palladium, which is the core of formation, is applied. As this metallic palladium, those produced by a palladium catalyst can be applied.

In the present embodiment, by imparting at least one of a hydroxyl group and a carboxyl group to the surface of the resin film 1, it is possible to strengthen the adsorption of metallic palladium on the surface of the resin film 1. Therefore, it is possible to improve the adhesion between the resin film 1 and the electroless copper plating layer 2.

The presence of hydroxyl groups and / or carboxyl groups at the interface between the resin film 1 and the electroless copper plating layer 2 can be confirmed by a known surface analysis method. For example, known analytical methods such as Fourier transform infrared spectrophotometer (FT-IR), X-ray photoelectron spectroscopy (ESCA), and time-of-flight secondary ion mass spectrometry (TOF-SIMS) can be used. is there.

In particular, in the present embodiment, at the interface between the resin film 1 and the electroless copper plating layer 2, as a result of analysis by the time-of-flight mass spectrometry (TOF-SIMS) on the side of the electroless copper plating layer 2, the peak at the mass 121 The strength is preferably 800 (0.12 amu bin) or more.
That is, in the present embodiment, as a result of analysis by TOF-SIMS, it is preferable that a functional group having a mass of 121 and containing a hydroxyl group and / or a carboxyl group is present at the interface between the resin film 1 and the electroless copper plating layer 2. The functional group having a mass of 121 is preferably any of the following structural formula 1 or structural formula 2, but structural formula 1 is particularly preferable.

The "functional group containing a hydroxyl group and / or a carboxyl group" imparted to the interface between the resin film 1 and the electroless copper plating layer 2 is not limited to the above. Further, as long as the "functional group containing a hydroxyl group" is added, the "functional group containing a carboxyl group" may not be added. And vice versa. Further, both a "functional group containing a hydroxyl group" and a "functional group containing a carboxyl group" may be added.

In particular, in the present embodiment, it is preferable that the interface between the resin film 1 and the electroless copper plating layer 2 is provided with more "functional groups containing hydroxyl groups" than "functional groups containing carboxyl groups". Alternatively, it is preferable that the "functional group containing a hydroxyl group" is added and the "functional group containing a carboxyl group" is not added.

In the copper-clad laminate of the present embodiment, as shown in FIG. 5, an electrolytic copper plating layer 4 may be further formed on the electroless copper plating layer 2 described above. That is, when the flexible circuit board is manufactured by the semi-additive method, it is possible to use the electroless copper plating layer 2 as a seed layer and further form an electroless plating layer on the electroless copper plating layer 2.

The method for forming the flexible circuit board using the copper-clad laminate of the present embodiment is not limited to the semi-additive method described above, and other known methods can be applied.

Further, in the copper-clad laminate of the present embodiment, it is preferable that the electroless copper plating layers are formed on both sides of the resin film and then the through holes H are formed as shown in FIG. That is, it is preferable that the resin film 1 has through holes in its cross section, and the through holes H are formed so that at least a part of the electroless copper plating layer 2 covers the inner surface of the through holes. It is preferable to form such a through hole H when the copper-clad laminate of the present embodiment is used for a flexible circuit board application.
Since the position and size of the through hole H can be appropriately determined by the flexible circuit board to be manufactured, detailed description thereof will be omitted.

The copper-clad laminate in the present embodiment includes the resin film 1 and the electroless copper plating layer 2 as described above, but is further on the surface of the electroless copper plating layer 2 (the side opposite to the resin film 1). ) May be formed with a known protective layer for preventing oxidation of the electroless copper plating layer 2. The protection of the electroless copper plating layer 2 is intended to suppress oxidation, and is formed by performing a rust preventive treatment by a known method.

<Manufacturing method of copper-clad laminate>
Next, a method of manufacturing the copper-clad laminate 10 of the present embodiment will be described with reference to FIG.
The method for producing the copper-plated laminate 10 in the present embodiment includes a first surface modification step (step 1) of imparting a carboxyl group and / or a hydroxyl group on at least one surface of the resin film 1, and the carboxyl group and / Or a second surface modification step (step 2) in which a charge is applied to the surface to which a hydroxyl group is applied by a wet method, and a catalyst adsorption step (step 3) in which a catalyst is adsorbed on the surface to which the charge is applied. ), The electroless copper plating step (step 4) of forming the electroless copper plating layer 2 on the surface on which the catalyst is adsorbed, and the copper-clad laminate on which the electroless copper plating layer is formed. The heating step (step 5) of heating is included.

First, the first surface modification step (step 1) will be described. As described above, the resin film 1 used is preferably a so-called low-dielectric resin film. As specific electrical characteristics of the resin film 1, it is preferable that the relative permittivity at a frequency of 10 GHz is 3.5 or less and the dielectric loss tangent is 0.008 or less.

In the first surface modification step of the present embodiment, a carboxyl group and / or a hydroxyl group is imparted onto at least one surface of the resin film 1. Examples of the method for imparting the carboxyl group and / or the hydroxyl group include a method in which a mixed solution of an alkaline aqueous solution and an amino alcohol is brought into contact with at least one surface of the resin film 1.

The alkaline aqueous solution used in the first surface modification step may be either an inorganic alkali or an organic alkali. Examples of the inorganic alkali include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, or carbonates thereof. Examples of the organic alkali include tetraalkylammonium hydroxide and the like.
The above-mentioned alkalis may be used alone or in combination of two or more.

On the other hand, the amino alcohol used in the first surface modification step may be, specifically, an aliphatic amino alcohol or an aromatic amino alcohol. Moreover, it may be a derivative thereof.

Specifically, as the amino alcohol, ethanolamine, heptaminol, isoetaline, butanolamine, propanolamine, sphingosine, methanolamine, dimethylethanolamine, N-methylethanolamine and the like can be used. Of these, it is particularly preferable to apply aminoethanol.

The mixing ratio of the alkaline aqueous solution and the amino alcohol in the first surface modification step is such that the ratio of -OH groups and -NH ₂ groups is (-NH ₂ groups / -OH groups) = 2.00 to the molar ratio. It is preferable to adjust it so that it becomes 3.00.
By setting the molar ratio within the above range, it is possible to achieve both the roughness reduction (reduction of transmission loss) and the adhesion between the electroless copper plating layer 2 and the resin film 1 which are the objects of the present invention. .. The reason is not clear at this time, but as a result of the examination by the inventors, it is presumed that the reason is as follows.

That is, with respect to the resin film 1 using the resin having a low dielectric loss (liquid crystal polymer, modified polyimide resin, etc.), the mixture having a molar ratio of _{(-NH 2 groups / -OH groups) within the above range is the first.} When the 1 surface modification step is performed, it is considered that the average surface roughness Ra of the surface on the electroless copper plating layer 2 side can be 1 nm to 150 nm as the state of the surface of the resin film 1. Therefore, when the wiring conductor is formed on the circuit board by the electroless copper plating layer, the transmission loss due to the skin effect is suppressed, and it is possible to exhibit preferable transmission characteristics. In addition, if the average surface roughness Ra of the surface on the electroless copper plating layer 2 side is within the range of 1 nm to 150 nm, the adhesion between the resin film 1 and the electroless copper plating layer 2 can be ensured.
Therefore, the present inventors have come up with the idea of achieving the object of the present invention by going through the first surface modification step as described above.

_{By setting the molar ratio of (-NH 2} groups / -OH groups) in the mixed solution in the above range in the first surface modification step, more hydroxyl groups than carboxyl groups are added to the surface of the resin film 1. can do.

As a method of bringing the mixed solution of the alkaline aqueous solution and the amino alcohol into contact with the surface of the resin film 1 in the first surface modification step, a known method can be appropriately applied, for example, the resin film 1 is immersed in the mixed solution. Examples thereof include a method and a method of spraying the mixed solution onto the resin film 1 by spraying or the like. The method is not limited to these methods, and any method other than the above method may be applied as long as it can impart a carboxyl group and / or a hydroxyl group to the surface of the resin film 1.

In the first surface modification step, the precipitation property of the plating and the adhesion of the plating can be improved by adjusting the contact angle of the film surface. In particular, when the resin film 1 is a liquid crystal polymer, the contact angle at the plating layer side interface in contact with the electroless copper plating layer 2 is preferably 30 ° or less. Further, particularly when the resin film 1 is a modified polyimide (MPI), the contact angle at the plating layer side interface in contact with the electroless copper plating layer 2 is preferably 45 ° or less.

Next, the second surface modification step (step 2) of the present embodiment will be described. The second surface modification step in the present embodiment is preferably a step performed after the first surface modification step described above.
The second surface modification step is a step of imparting a carboxyl group and / or a hydroxyl group on the surface of the resin film 1 in the first surface modification step, and then further adding an electric charge. It is preferable because it is possible to improve the adhesion between the resin film 1 and the electroless copper plating layer 2 by applying an electric charge.

That is, as described above, in order to form the electroless copper plating layer 2, it is preferable that the metallic palladium, which is the core of the plating growth, is present on the resin film 1. Then, in order for the metallic palladium to adhere firmly to the resin film 1, it is preferable that the surface of the resin film 1 has at least a negative charge.

Preferably, in the second surface modification step of the present embodiment, further, a step of applying a positive charge on the surface of the resin film 1 and a step of further applying a negative charge to the surface to which the positive charge is applied are performed. It is preferable to include it. By going through these steps, it is possible to reliably attach a negative charge to the surface of the resin film 1. Therefore, from the viewpoint of the above-mentioned adhesion of metallic palladium and the adhesion of the electroless copper plating layer 2. Is preferable.

In the above-mentioned step of imparting a positive charge on the surface of the resin film 1, as a specific method, the resin film 1 after imparting a carboxyl group and / or a hydroxyl group to the surface is further known as a cationic surfactant. It is possible to apply a method of immersing in an agent, a method of bringing a known cationic surfactant into contact with the resin film 1 by spraying, or the like.

Further, also in the step of adsorbing a negative charge on the surface of the resin film 1, it is possible to apply a method of immersing in a known anionic surfactant, a method of spraying, or the like.
The second surface modification step of the present embodiment is preferably performed by a wet method as described above. By performing the wet method, it is suitable for mass production by reel-to-reel or the like, and there is an advantage that the cost can be reduced.

Next, the catalyst adsorption step (step 3) in the production method in the present embodiment will be described.
The catalyst adsorption step of the present embodiment is a step of further adsorbing the catalyst on the surface of the resin film 1 with respect to the resin film 1 to which at least a negative charge is applied to the surface by the second surface modification step described above. ..

In the catalyst adsorption step, as a method of further adsorbing the catalyst on the surface of the resin film 1, for example, a known catalyst solution can be brought into contact with the surface of the resin film 1 by a known method. As the catalyst, Cu, Ni, Pd, Ag and the like can be used. As the known catalyst solution, for example, a tin-palladium-based catalyst solution or a palladium colloid-based catalyst solution can be used, but the catalyst solution is not limited thereto.

In the catalyst adsorption step, the amount of the catalyst applied to the resin film 1 is preferably ^{15 μg / dm 2 or less as metallic palladium.} The lower limit of the catalyst should be as small as possible in consideration of etching during circuit formation, but it must be applied to the extent that the electroless copper plating layer is well formed, and it may be 1 μg / dm ² or more. preferable.
If the amount of metallic palladium applied to the resin film 1 exceeds the above value, the insulation reliability between the circuits when the flexible circuit board is used may decrease, which is not preferable.
The amount of metallic palladium can be obtained by a known measuring method. For example, it can be obtained by a method such as peeling only copper from the resin film 1, dissolving the palladium residue on the resin film 1 with nitric acid, and measuring the amount of the residue by ICP.

Next, the electroless copper plating step (step 4) in the manufacturing method of the present embodiment will be described.
The electroless copper plating step is preferably performed after the catalyst adsorption step. Here, an example is given below as a condition of electroless plating in this embodiment.
[Example of electroless copper plating conditions]
Bath composition: Copper sulfate 5-10g / L
Nickel sulfate 0.5-1.0 g / L
Rochelle salt 10-30g / L
Sodium hydroxide 3-8g / L
pH: 7-13
Bath temperature: 29-35 ° C

The immersion time of the resin film 1 in the plating bath may be appropriately determined so that the thickness of the electroless copper plating layer 2 is 0.1 to 1.0 μm.

Further, the plating layer formed in this electrolytically electroless copper plating step is not limited to plating Cu alone, and may be copper alloy plating. For example, it may form a Cu—Ni alloy, a Cu—Zn alloy, a Cu—Sn alloy, or the like.
As the plating bath in this case, a known plating bath can be appropriately applied.

In the production method of the present embodiment, after the electrolytic copper plating layer 2 is formed on the resin film 1, the purpose is to release the internal stress of the electrolytic copper plating layer, to cause structural transformation, and the like. It is preferable to have a heating step (step 5) for heating the entire copper-clad laminate on which the electrolytic copper plating layer is formed.
The heating temperature for stress relaxation is preferably 100 to 200 ° C, more preferably 120 to 150 ° C. The heating time for stress relaxation is preferably 5 to 60 minutes, more preferably 10 to 30 minutes. The heating temperature for transforming the tissue is preferably 150 to 350 ° C, more preferably 150 to 300 ° C. The heating time for transforming the tissue is preferably 5 to 180 minutes, more preferably 10 to 30 minutes.
Further, the heating atmosphere may be, for example, an atmosphere or an atmosphere of an inert gas such as nitrogen.
By performing the heating step, it is possible to prevent the electroless copper plating layer 2 from peeling off from the resin film 1, and it is possible to secure the adhesion between the electroless copper plating layer 2 and the resin film 1. Further, as the crystallites of the electrolytic copper plating layer 2 grow, the copper plating layer (electrolytic copper plating layer 2 and electrolytic copper plating layer 4) and the resin film 1 after laminating the electrolytic copper plating layer 4 described later are laminated. Adhesion with can be improved.

In the method for producing a copper-clad laminate of the present embodiment, after the electrolytic copper plating layer 2 is formed by the electrolytic copper plating step, the electrolytic copper plating step of forming the electrolytic copper plating layer 4 by the electrolytic plating step is performed. You may have. As the electrolytic copper plating step, a known copper sulfate bath, copper pyrophosphate bath, or the like can be applied, and the electrolytic plating conditions (pH, temperature, current density, immersion time, etc.) are the thickness of the electrolytic plating layer. It can be selected as appropriate based on the above.
Through the above steps, the copper-clad laminate 20 according to the present embodiment is manufactured.

In the manufacturing method of the present embodiment, the above-mentioned step 5 is performed after the electrolytic copper plating layer 4 is formed on the resin film 1 (that is, after the electrolytic copper plating layer and the electrolytic copper plating tank are formed). The entire stretched laminate may be heated (baked). In other words, in the present embodiment, the electrolytic copper plating layer 4 may be formed on the resin film 1 and then the heating step described above may be performed, or the electrolytic copper plating layer 2 may be formed on the resin film 1. A heating step of heating the entire copper-clad laminate may be performed after the copper plating layer 4 is formed. When the above-mentioned step 5 is executed before forming the electrolytic copper plating layer 4, it is more preferable to execute the step 5 before the resist patterning step described later.

<Flexible circuit board>
Next, the flexible circuit board of this embodiment will be described.
The flexible circuit board in this embodiment is preferably a flexible circuit board in which a circuit is formed by the electroless copper plating layer 2 of the copper-clad laminate 10 described above.
As described above, in the copper-clad laminate 10 of the present embodiment, the surface roughness Ra between the resin film 1 and the electroless copper plating layer 2 is equal to or less than a predetermined value, so that the transmission loss as a flexible circuit board is reduced. It can be suppressed.
Further, since it is possible to improve the adhesion between the resin film 1 and the electroless copper plating layer 2, it is preferable because a fine circuit pattern can be formed even when the semi-additive method is adopted.

More specifically, for example, in the case of the SAP method or the MSAP method, as the method for manufacturing the flexible circuit board in the present embodiment, after going through the above-mentioned steps 1 to 5 (see also FIG. 4), the electroless plating layer 2 A known resist patterning step of applying and patterning a resist is performed on the resist, and then the electrolytic copper plating step described above is performed to form an electrolytic plating layer 4 between the patterned resists.
The method for forming the flexible circuit board of the present embodiment is not limited to the semi-additive method described above, and other known methods such as the full additive method and the subtractive method can be applied.

Next, the present invention will be described in more detail with reference to examples.

<Example 1>
First, a liquid crystal polymer film (Vecstar CTQLCP, manufactured by Kuraray Co., Ltd., thickness: 50 μm) was prepared as the resin film 1. As for the electrical characteristics, the relative permittivity at 10 GHz was 3.3, and the dielectric loss tangent at 10 GHz was 0.002.

Next, both sides of the prepared resin film 1 are immersed in a mixed solution of potassium hydroxide aqueous solution and monoethanolamine for 5 minutes as a first surface modification step, and carboxyl groups and / or hydroxyl groups are added to both surfaces. It was introduced and washed with immersion water. The temperature of the mixed solution used was 30 ° C., and the molar ratio of _{-OH group and -NH 2} _{group (-NH 2} group / -OH group) was 2.29. The peak intensity of the mass 121 of TOF-SIMS was 1000.

Next, as a second surface modification step, both sides of the resin film 1 were immersed in an aqueous solution of a cationic surfactant of 10 g / L for 2 minutes to adsorb a positive charge. Immersion After washing with water, it was immersed in an aqueous solution of an anionic surfactant of 3 g / L for 1 minute. In this way, after adsorbing the positive charge, the negative charge was adsorbed.
Further, as a catalyst adsorption step and an electroless copper plating step, the plating catalyst was _{immersed in an aqueous solution of palladium chloride (PdCl 2} ) (2 g / l, pH 12, 40 ° C.) for 5 minutes and then washed with immersion water. Further, it was immersed in an aqueous solution (25 ° C.) containing 1 g / L of dimethylamine borane (DMAB) and 6 g / L of boric acid as a catalytic activator (reducing agent) for 5 minutes, and then washed with immersion water.
Then, an electroless Cu—Ni plating layer of 0.3 μm was formed by an electroless plating bath. The electroless plating conditions were as follows. The Ni content in the obtained electroless Cu—Ni plating layer was determined by using the above-mentioned plasma emission spectrophotometer (ICP) and found to be 1.18 wt%.

[Electroless plating conditions]
Bath composition: Copper sulfate 7.5 g / L
Nickel sulfate 0.7g / L
Rochelle salt 20g / L
Sodium hydroxide 5g / L
pH: 9
Bath temperature: 32 ° C

Then, an electrolytic copper plating layer was further formed with a thickness of 18 μm on the electroless Cu—Ni plating layer in the copper-clad laminate by an electrolytic plating bath. The electrolytic copper plating conditions were as follows.
Bath composition: Copper sulfate hexahydrate 200 g / L
Sulfuric acid 50g / L
Chloride ion 50ppm
Brightener 5 ml / L (Okuno Pharmaceutical Additive Top Luciner)
Bath temperature: 20-25 ° C
pH: 1 or less Current density: 2-3 A / dm ²

[Heating (annealing) treatment]
In this example, after the electroless copper plating layer was formed, the first heat treatment was performed under the following heating conditions, and after the electrolytic copper plating layer was formed, the second heat treatment was performed under the following heating conditions.
<Heating conditions in the first heat treatment>
Heating temperature: 150 ° C
Heating time: 10 minutes Heating atmosphere: Atmosphere <Heating conditions in the second heat treatment>
Heating temperature: 230 ° C
Heating time: 10 minutes Heating atmosphere: In the atmosphere By going through the above steps, the copper-clad laminate 10 in Example 1 was obtained.

[Evaluation]
<TOF-SIMS and ESCA>
In order to confirm the presence of carboxyl groups and / or hydroxyl groups at the interface between the resin film 1 and the electroless copper plating layer 2, the surface condition was confirmed.
First, the obtained copper-clad laminate 10 was immersed in the electroless copper plating layer 2 in _{a FeCl 3 solution (50 ° C.) of 42 bohm without heat treatment, and the electroless copper plating layer 2 disappeared.} The electroless copper plating layer 2 was peeled off by taking it out at the timing visually confirmed, and the resin film was exposed. The exposed resin film surface was cut out to a size of 20 mm × 20 mm and used as a measurement sample. This measurement sample was measured with an X-ray photoelectron spectroscope (manufactured by JEOL Ltd., JPS-9200, X-ray source: Mg, analysis area: φ3 mm) to obtain a C1s spectrum. Then, the intensity of the peak derived from the carboxyl group (COO (H) bond) appearing in the binding energy 288.8 eV and the intensity of the peak derived from the CC bond appearing in the binding energy 284.7 eV were calculated.

According to the measurement result by the above ESCA, the existence of the carboxyl group could not be confirmed. Next, the surface condition of the measurement sample was confirmed by TOF-SIMS.

The surface of the measurement sample was analyzed by TOF-SIMS TRIFT-II (manufactured by ULVACPHI CO., LTD.). An untreated resin film sample was used as a control. The measurement conditions are as follows.
Primary ion: ⁶⁹ Ga
Acceleration voltage: 15kV
Measurement range: 100 μm x 100 μm
Mass range: 0.5-300 (m / z)

The obtained results were analyzed by analysis software Win Cadence (manufactured by Physical Electricals). In the TOF-SIMS spectrum, it was confirmed that a characteristic peak at mass 121 was observed only from the surface of the sample from which the electroless copper plating was peeled off. No peak characteristic of mass 121 was observed from the surface of the untreated sample.
According to the measurement results by ESCA, the presence of the carboxyl group could not be confirmed. Therefore, after the first surface modification step and the second surface modification step, C ₈ H ₉ O (-CH-CH) ₃ -C ₆ H ₄ -OH) group is determined to have been introduced.

<Ra after peeling of the plating layer>
The obtained copper-clad laminate 10 (thickness of electroless copper plating layer: 0.3 μm (in the case of Examples 1 to 5, Examples 11 and Comparative Examples 1 to 8) or 0.2 μm (Examples 6 to 6). In the case of 10 and Comparative Example 9)), the electroless copper plating layer 2 was peeled off using a _{FeCl 3 solution in the same manner as described above to expose the resin film.} The surface roughness (Ra) of the exposed resin film was measured by a laser microscope (Olympus OLS3500) in AFM mode and a viewing angle of 5 μm × 5 μm. The values obtained are shown in Table 2.

<Contact angle>
With respect to the obtained copper-clad laminate 10, the electroless copper plating layer 2 was peeled off using a _{FeCl 3 solution in the same manner as described above to expose the resin film.} The exposed resin film surface was cut out to a size of 20 mm × 20 mm and used as a measurement sample. 2.0 μL of pure water was dropped on the surface of this sample, and the contact angle was measured with a contact angle measuring device (DropMaster manufactured by Kyowa Interface Science Co., Ltd.). The contact angle of the untreated resin surface used in Example 1 was 65 °, and the contact angle of the untreated resin surface used in Example 5 was 58 °.

<Tape peeling strength>
The obtained copper-clad laminate 10 (thickness of electroless copper plating layer: 0.3 μm (in the case of Examples 1 to 5, Examples 11 and Comparative Examples 1 to 8) or 0.2 μm (Examples 6 to 6). 10 and Comparative Example 9))), an adhesive tape (manufactured by Nichiban Co., Ltd.) was attached to the surface of the electroless copper plating layer 2, and then the tape was peeled off to perform a tape peeling test, which was visually electroless. When the peeling of the copper plating layer 2 was not confirmed, the evaluation result was evaluated as 〇. The results are shown in Table 2.

<90 ° peel strength>
A copper-clad laminate 20 formed with electrolytic copper plating and subjected to a second heat treatment at 230 ° C. for 10 minutes is cut out into a sample having a size of 40 mm × 40 mm, and the cut-out sample is attached to an aluminum plate with polyimide tape. It was. The 90 ° peel strength was measured as the adhesive strength between the resin film and the electroless copper plating layer as follows.

That is, a strip-shaped cut is made in the copper-plated surface at 5 mm intervals with a cutter on the surface on which the electrolytic copper plating layer is formed on each test material, and then the strip-shaped end is forcibly peeled off to create a trigger for peeling. , The peeled resin film and the copper-plated part were made. Next, the peeled resin film and the copper plating layer were sandwiched between Tensilon chucks, and the 90 ° peel strength was measured by an autograph. The 90 ° peel strength was converted into N / cm (width). These results are shown in Table 2.

<Plating property (appearance inspection)>
The appearance of the electroless copper plating layer of the obtained copper-clad laminate was visually observed, and those without peeling or swelling were shown as ◯ in Table 2.

<Measurement of Ni content of electroless copper plating layer 2>
After forming the electroless copper plating layer 2 under the conditions shown in Table 1, 2 cm × 2 cm was immersed in 30% nickel (normal temperature) to dissolve the electroless copper plating layer 2, and the obtained liquid was used as a plasma emission spectroscopic analyzer ( Using ICP) (ICPE-9820 manufactured by Shimadzu Corporation), weigh Cu (copper) and Ni (nickel), calculate Ni weight / Cu weight + Ni weight, and calculate the Ni content of the electroless copper plating layer 2. Was calculated.

<Comprehensive evaluation>
The above evaluation items were comprehensively judged, and those that had no practical problem were shown as ◯, and those that were not practical were shown as x in Table 2.

<Example 2>
The same procedure as in Example 1 was carried out except that the temperature of the mixed solution in the first surface modification step was changed to the temperature shown in Table 1. The results are shown in Tables 1 and 2.

<Example 3>
The same procedure as in Example 1 was carried out except that the molar ratio _{of -OH groups and -NH 2} _{groups (-NH 2} groups / -OH groups) of the mixed solution in the first surface modification step was changed to the values shown in Table 1. It was. The results are shown in Tables 1 and 2.

<Example 4>
The same procedure as in Example 1 was carried out except that the temperature of the mixed solution in the first surface modification step was changed to the temperature shown in Table 1. The results are shown in Tables 1 and 2.

<Example 5>
A modified polyimide (MPI) resin (FS-L manufactured by SKC Kolon PI, thickness: 50 μm) was prepared as the resin film 1. As for the electrical characteristics, the relative permittivity at 10 GHz was 3.4, and the dielectric loss tangent at 10 GHz was 0.0035.

Next, both sides of the prepared resin film 1 are immersed in a mixed solution of sodium hydroxide aqueous solution and monoethanolamine for 5 minutes as a first surface modification step, and carboxyl groups and / or hydroxyl groups are introduced on both surfaces. Then, it was washed with immersion water. The temperature of the mixed solution used at this time was 40 ° C., and the molar ratio of _{-OH group and -NH 2} _{group (-NH 2} group / -OH group) was 0.19.

Next, as a second surface modification step, a positive charge was adsorbed on both surfaces of the resin film 1 by the same method as in Example 1, and then a negative charge was further adsorbed.
Further, as a catalyst adsorption step and an electroless copper plating step, the plating catalyst was _{immersed in an aqueous solution of palladium chloride (PdCl 2} ) (2 g / l, pH 12, 40 °) for 5 minutes and then washed with immersion water. Further, it was immersed in an aqueous solution (25 ° C.) containing 1 g / L of dimethylamine borane (DMAB) and 6 g / L of boric acid as a catalytic activator (reducing agent) for 5 minutes, and then washed with immersion water.

Then, an electroless Cu—Ni plating layer of 0.3 μm was formed by an electroless plating bath. The electroless plating conditions were as follows. At this time, the Ni content in the electroless Cu—Ni plating layer was 1.18 wt%.
[Electroless plating conditions]
Bath composition: Copper sulfate 7.5 g / L
Nickel sulfate 0.7g / L
Rochelle salt 20g / L
Sodium hydroxide 5g / L
pH: 12.5
Temperature: 32 ° C
Processing time: 10 minutes

After that, an electrolytic copper plating layer was further formed with a thickness of 18 μm on the electroless Cu—Ni plating layer in the above copper-clad laminate by an electrolytic plating bath in the same manner as in Example 1.

[Heating (annealing) treatment]
In Example 5, after forming the electroless copper plating layer, the first heat treatment was performed using a dry oven (DY300 manufactured by Yamato Scientific Co., Ltd.) under the following heating conditions. The second heat treatment after the above-mentioned electrolytic plating was omitted.
<Heating conditions in the first heat treatment>
Heating temperature: 150 ° C
Heating time: 60 minutes Heating atmosphere: In the atmosphere By going through the above steps, the copper-clad laminate 10 in Example 5 was obtained.
In this way, after obtaining the copper-clad laminate 10 of Example 5, the copper-clad laminate was evaluated in the same manner as in Example 1. The results of Example 5 are shown in Tables 1 and 2.

<Example 6>
The plating thickness of the electroless Cu-Ni plating layer was set to 0.2 μm, and annealing (heat treatment) was performed in an inert (nitrogen) gas using a vacuum drying device (DQ-46P-LP manufactured by Sato Vacuum Co., Ltd.). A copper-clad laminate was obtained in the same manner as in Example 2 except that the annealing (heat treatment) was performed at ° C. for 180 minutes after electroless copper plating and before electrolytic copper plating. No heat treatment was performed after electrolytic copper plating.
Then, in the same manner as in Example 1, the copper-clad laminate of Example 6 was evaluated. The results of Example 6 are shown in Tables 1 and 2.

<Example 7>
A copper-clad laminate was obtained in the same manner as in Example 6 except that the nickel sulfate content in the electroless Cu—Ni plating bath was 0.32 g / L. The Ni content in the obtained electroless Cu—Ni plating layer was 0.74 wt%. Then, in the same manner as in Example 1, the copper-clad laminate of Example 7 was evaluated. The results of Example 7 are shown in Tables 1 and 2.

<Example 8>
A copper-clad laminate was obtained in the same manner as in Example 6 except that the nickel sulfate content in the electroless Cu—Ni plating bath was 0.13 g / L. The Ni content in the obtained electroless Cu—Ni plating layer was 0.41 wt%. Then, in the same manner as in Example 1, the copper-clad laminate of Example 8 was evaluated. The results of Example 8 are shown in Tables 1 and 2.

<Example 9>
A copper-clad laminate was obtained in the same manner as in Example 6 except that the nickel sulfate content in the electroless Cu—Ni plating bath was 0.065 g / L. The Ni content in the obtained electroless Cu—Ni plating layer was 0.18 wt%. Then, in the same manner as in Example 1, the copper-clad laminate of Example 9 was evaluated. The results of Example 9 are shown in Tables 1 and 2.

<Example 10>
A copper-clad laminate was obtained in the same manner as in Example 6 except that the nickel sulfate content in the electroless Cu—Ni plating bath was 0.013 g / L. The Ni content in the obtained electroless Cu—Ni plating layer was 0.14 wt%. Then, in the same manner as in Example 1, the copper-clad laminate of Example 10 was evaluated. The results of Example 10 are shown in Tables 1 and 2.

<Example 11>
Copper in the same manner as in Example 6 except that the nickel sulfate content in the electroless Cu—Ni plating bath was 0.0065 g / L and the thickness of the electroless Cu—Ni plating layer was 0.3 μm. A tension laminate was obtained. The Ni content in the obtained electroless Cu—Ni plating layer was 0.09 wt%. Then, in the same manner as in Example 1, the copper-clad laminate of Example 11 was evaluated. The results of Example 11 are shown in Tables 1 and 2.

<Comparative example 1>
First, a polyimide film (Kapton, manufactured by Toray DuPont Co., Ltd., thickness: 50 μm) was prepared as the resin film 1. As for the electrical characteristics, the relative permittivity at 1 MHz was 3.4, and the dielectric loss tangent at 1 MHz was 0.0024.
Next, the prepared resin film 1 was immersed in a potassium hydroxide aqueous solution (200 g / L) at 30 ° C. for 10 minutes and washed with immersion water.

As a catalyst adsorption step and an electroless plating step, the plating catalyst is _{immersed in an aqueous solution of palladium chloride (PdCl 2} ), then immersed in an aqueous solution of dimethylamine borane (DMAB) as a catalytic activator (reducing agent), washed with immersion water, and then electroless nickel. An electroless nickel-phosphorus plating layer of 0.5 μm was formed by a phosphorus plating bath. The electroless plating conditions were as follows. The conditions of the catalyst adsorption step were the same as in Example 1. Further, the subsequent electrolytic copper plating and annealing (heat treatment) were the same as in Example 1.

[Electroless plating conditions]
Bath composition: Nickel sulfate 27 g / L
Sodium hypochlorite 30 g / L
Malic acid 30g / L
Lactic acid 15g / L
Stabilizer 0.6ppm
pH: 4.5
Temperature: 89 ° C
Processing time: 5 minutes

<Comparative example 2>
The same procedure as in Comparative Example 1 was carried out except that the liquid crystal polymer film used in Example 1 was used as the resin film. The results are shown in Tables 1 and 2.

<Comparative example 3>
The same procedure as in Comparative Example 2 was carried out except that the electroless plating layer was an electroless copper plating layer.
[Electroless plating conditions]
Bath composition: Copper sulfate 6 g / L
Rochelle salt 20g / L
Formalin 5g / L
pH: 11.5
Temperature: 30 ° C
Processing time: 10 minutes

<Comparative example 4>
It was carried out in the same manner as in Comparative Example 3 except that the second surface modification step was carried out under the same conditions as in Example 1.

<Comparative example 5>
The same procedure as in Example 1 was carried out except that the molar ratio _{of -OH groups and -NH 2} _{groups (-NH 2} groups / -OH groups) of the mixed solution used as the first surface modification step was 0.23. ..

<Comparative Example 6>
The same procedure as in Example 1 was carried out except that the molar ratio _{of -OH groups and -NH 2} _{groups (-NH 2} groups / -OH groups) of the mixed solution used as the first surface modification step was 0.45. ..

<Comparative Example 7>
The same procedure as in Example 1 was carried out except that the molar ratio _{of -OH groups and -NH 2} _{groups (-NH 2} groups / -OH groups) of the mixed solution used as the first surface modification step was 0.92. ..

<Comparative Example 8>
The same procedure as in Example 1 was carried out except that the molar ratio _{of -OH group and -NH 2} _{group (-NH 2} group / -OH group) of the mixed solution used as the first surface modification step was set to 1.83. ..

<Comparative Example 9>
The electroless plating formed on the resin film was copper plating (Ni content was 0), and the plating thickness of this electroless Cu plating was 0.2 μm using the same plating solution as in Comparative Example 3. Using the same equipment as in Example 6, annealing (heat treatment) was performed in an inert (nitrogen) gas at 280 ° C. for 180 minutes, and this annealing (heat treatment) was performed after electroless copper plating and before electrolytic copper plating. Except for what was done, it was done in the same manner as in Example 2. In Comparative Example 9, since the electroless Cu plating layer was locally non-plated, electrolytic Cu plating was performed only on the portion where the electroless Cu plating layer was formed, except for the measurement of peel strength. Evaluation was performed.

In the copper-clad laminate of the present invention, the surface roughness Ra between the resin film and the electroless copper plating layer is equal to or less than a predetermined value, so that transmission loss as a flexible circuit board can be suppressed and a high frequency is obtained. Can provide high transmission characteristics in. Further, since it is possible to improve the adhesion between the resin film and the electroless copper plating layer, it is possible to form a fine circuit pattern even when the full additive method or the semi-additive method is adopted as the circuit forming method. Is.
According to the copper-clad laminate of the present invention, it is clear that it is suitably applied to a wiring board or the like that requires fine wiring having a multi-layer structure.

1 Resin film 2 Electroless copper plating layer 4 Electroplating layer 10 Copper-clad laminate 20 Copper-clad laminate

Claims

A low-dielectric resin film having a relative permittivity of 3.5 or less and a dielectric loss tangent of 0.008 or less at a frequency of 10 GHz.
An electroless copper plating layer laminated on at least one surface of the low-dielectric resin film,
Including
Among the low-dielectric resin films, the average surface roughness Ra at the plating layer side interface in contact with the electroless copper plating layer is 1 to 150 nm, and the adhesion strength between the resin film and the electroless copper plating layer is 4. A copper-clad laminate characterized by being .2 N / cm or more.
The copper-clad laminate according to claim 1, wherein the strength of the mass 121 by the time-of-flight mass spectrometry (TOF-SIMS) at the interface on the plating layer side of the resin film is 800 or more.
The copper-clad laminate according to claim 1 or 2, wherein a hydroxyl group and / or a carboxyl group is added to the interface on the plating layer side of the resin film.
The copper-clad laminate according to claim 3, wherein more hydroxyl groups are added than the carboxyl groups at the plating layer side interface.
The copper-clad laminate according to any one of claims 1 to 4, wherein the resin film is any one of polyimide, modified polyimide, liquid crystal polymer, and fluororesin, or a mixture thereof.
The electroless copper plating layer is a Cu—Ni alloy.
The copper-clad laminate according to any one of claims 1 to 5, wherein the content of Ni in the electroless copper plating layer is 3 wt% or less.
The copper-clad laminate according to any one of claims 1 to 6, wherein the thickness of the electroless copper plating layer is in the range of 0.1 to 1.0 μm.
The copper-clad laminate according to any one of claims 1 to 7, wherein a metal made of Cu, Ni, Pd, or Ag is present at the interface of the resin film on the electroless copper plating layer side. body.
The copper-clad laminate according to any one of claims 1 to 8, further comprising a protective layer formed on the electroless copper plating layer.
The electroless copper plating layer is formed on both sides of the resin film, and
The copper-clad laminate according to any one of claims 1 to 9, wherein the resin film has through holes, and at least a part of the electroless copper plating layer is formed on the inner wall of the through holes. body.
A method for producing a copper-clad laminate produced by forming an electroless copper plating layer on a resin film having a relative permittivity of 3.5 or less and a dielectric loss tangent of 0.008 or less at a frequency of 10 GHz.
The first surface modification step of imparting a carboxyl group and / or a hydroxyl group to the surface of the resin film, and
A second surface modification step of applying an electric charge to the surface to which the carboxyl group and / or a hydroxyl group is added by a wet method, and
A catalyst adsorption step of adsorbing a catalyst on the surface to which the electric charge is applied, and
An electroless copper plating step of forming an electroless copper plating layer on the surface on which the catalyst is adsorbed,
A heating step of heating the copper-clad laminate on which the electroless copper plating layer is formed, and
A method for producing a copper-clad laminate, which comprises.
The method for producing a copper-clad laminate according to claim 11, wherein a mixed solution of an alkaline aqueous solution and an amino alcohol is used in the first surface modification step.
The method for producing a copper-clad laminate according to claim 12, wherein the amino alcohol is amino ethanol.
The method for producing a copper-clad laminate according to any one of claims 11 to 13, wherein more hydroxyl groups are imparted to the surface of the resin film than the carboxyl groups.
According to any one of claims 11 to 14, in the second surface modification step, a positive charge is adsorbed on the surface to which the carboxyl group and / or the hydroxyl group is added, and then the negative charge is adsorbed on the surface. The method for producing a copper-clad laminate according to the description.
The copper-clad laminate according to claim 15, wherein a cationic surfactant is added to the surface to adsorb the positive charge, and an anionic surfactant is added to the surface to adsorb the negative charge. Production method.
A flexible circuit board on which a circuit made of the copper-clad laminate according to any one of claims 1 to 10 is formed.