JP2016007722A - Copper-clad laminate and flexible printed wiring board using copper-clad laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an FPC which maintains excellent bondability between a resin film and copper foil and has a high degree of freedom in arrangement relation between the resin film and a positioning marker with excellent transmissive visibility at a resin film portion remaining after removal of the copper foil by chemical etching, and a copper-clad laminate for obtaining the FPC.SOLUTION: The copper-clad laminate includes a resin film and copper foil which are directly laminated. The peel strength between the resin film and the copper foil is 0.5 N/mm or more. The resin film remaining after removal of a part of the copper foil by chemical etching has a transmissive visibility Vdefined by a formula: V=(T-T)×C/100 (T: total light transmittance (unit: %), T: diffuse transmittance (unit: %), and C: transparency (unit: %)) satisfying: V≥10%.

Description

  The present invention relates to a technique for a flexible printed wiring board, and in particular, a flexible printed wiring board having good transmission visibility through a flexible base material that becomes a remainder after etching and removing a conductive foil, and the flexible printed wiring board. The present invention relates to a copper clad laminate for obtaining.

  A flexible printed circuit board (FPC) has a structure in which a flexible base material such as a resin film and a conductive foil are laminated, and because of its thinness and excellent flexibility, the flexibility in the wiring mounting form is high. It has the advantage of being expensive. Therefore, at present, FPC is widely used for wiring in movable parts of electronic devices and bent wiring in a narrow space.

  As flexible substrates of FPC, resin films (for example, polyimide films) with good thermal, mechanical, and chemical properties are generally used, and various surface treatments are applied to FPC conductor foils. Pure copper foil or copper alloy foil (hereinafter simply referred to as “copper foil”) is generally used. Copper foils are roughly classified into electrolytic copper foils and rolled copper foils depending on the manufacturing method.

  The manufacturing process of FPC is roughly as follows: “Process for forming copper clad laminate (CCL) by bonding copper foil for FPC and resin film” and “Process for forming circuit wiring on the copper clad laminate” (Step of etching away copper foil other than the circuit wiring portion). The copper-clad laminate is a three-layer copper-clad laminate in which a resin film and a copper foil are laminated via an adhesive, and a two-layer in which a resin film and a copper foil are directly laminated without using an adhesive. Broadly divided into copper-clad laminates.

  Since FPC has been used as a wiring material in moving parts as described above, it has traditionally had excellent bondability between resin film and copper foil (for example, peel strength of 0.5 N / mm or more) and excellent The bending characteristics (for example, bending characteristics of 1 million times or more) have been mainly required.

  In recent years, FPC has come to be used as a wiring material to a liquid crystal member, a mounting material for an IC chip, and the like due to high functionality of small electronic devices (for example, smart phones and tablet PCs). In this case, in the mounting process of liquid crystal members and IC chips, mounting with positioning markers that can be seen through the resin film part of the FPC (particularly the resin film part remaining after etching away the copper foil other than the circuit wiring) Components (liquid crystal members and IC chips) and FPC are aligned. For this reason, the FPC has been required to have good transmission visibility in the resin film portion remaining after the copper foil is removed by etching.

  On the other hand, as described above, FPC is required to have excellent bondability between the resin film and the copper foil. In order to ensure sufficient bondability at the CCL stage, the interface between the resin film and the copper foil (usually normal) , The copper foil side joining surface) is often subjected to a roughening treatment (for example, a roughened copper plating layer is formed). In general, as the surface roughness of the joint surface on the copper foil side increases (as the deep unevenness is formed), the bondability with the resin film is improved by the anchor effect.

  Here, since the anchor effect is an improvement in bondability due to the engagement of irregularities, irregularities are basically formed on the resin film side also in a negative / positive relationship. As a result, in FPC with increased bonding surface roughness to improve bondability, large surface irregularities remain in the resin film that remains after the copper foil is etched away, so a positioning marker via the resin film The problem that the visibility of was very bad occurred.

  However, if priority is given to improving the visibility of the positioning marker via the resin film and the roughness of the joint surface is excessively reduced, the bondability between the resin film and the copper foil is lowered and the reliability of the FPC is impaired. Problems arise. That is, it was found that the roughness of the joint surface needs to be controlled within an appropriate range, and various techniques were studied.

  For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-98659), a polyimide film and a low-roughness copper foil are laminated, and the light transmittance at a wavelength of 600 nm of the film after the copper layer etching is 40% or more, A copper clad laminate having a haze value (HAZE) of 30% or less, an adhesive strength of 500 N / m or more, and an adhesive strength of 285 N / m or more after heat treatment at 150 ° C. for 1000 hours is disclosed. Has been. According to Patent Document 1, all the problems in the conventional copper-clad laminate for substrates (the adhesive strength is low and the transparency of the remaining polyimide film after etching the copper foil is poor) are all solved. It is said that a copper-clad laminate using a polyimide substrate material can be provided.

  In Patent Document 2 (Japanese Patent Laid-Open No. 2013-147688), roughened particles are formed on a copper foil surface by a roughening treatment, and the average roughness Rz of the roughening treatment surface is 0.5 to 1.3 μm. The glossiness is 0.5 to 68, and the ratio A / B between the surface area A of the roughened particles and the area B obtained when the roughened particles are viewed in plan from the copper foil surface side is 2.00 to 2.45. A surface treated copper foil is disclosed. According to Patent Document 2, it is a surface-treated copper foil excellent in adhesiveness to a resin substrate, and the transparency of the resin substrate after removing the copper foil in the copper-clad laminate by etching (the resin substrate) It is said that the surface-treated copper foil can be provided.

JP 2004-98659 A JP 2013-147688 A

As described above, in recent years, in addition to the excellent bondability between the resin film and the copper foil, the FPC has been required to have good transmission visibility in the resin film portion remaining after the copper foil is etched away. ing. In general, the total light transmittance T _t and the haze H are used as indicators for the transparency of the resin film. These indicators are affected by the color tone and surface roughness of the resin film.

  Regarding the color tone of the resin film, the influence of the material of the resin film is considered to be large, but in FPC, polyimide film is usually selected because of various required characteristics, and it is not easy to change the material from the viewpoint of cost etc. Absent. In other words, in the present invention, the material of the resin film is not a special control target.

On the other hand, the surface roughness of the resin film is strongly influenced by the surface properties of the bonding surface on the copper foil side. That is, the surface roughness of the resin film can be controlled by controlling the surface properties (roughening properties) of the bonding surface on the copper foil side. However, it is not possible to successfully control the quality of transmission visibility of a resin film only by control based on general indices indicating the surface roughness of metal (for example, arithmetic average roughness Ra, maximum height Rz). It was. Therefore, an index (for example, total light transmittance T _t , haze H) directly indicating the transparency of the resin film is often used as a judgment criterion.

The present inventors also investigated in detail the transmission visibility in the resin film portion (resin film portion remaining after the chemical etching removal of the copper foil) in the FPC. As a result, depending on the positional relationship between the resin film and the positioning marker, even if the conventional index indicating the transparency of the resin film (for example, total light transmittance T _t , haze H), the positioning marker transmission visibility is good. It was found that it cannot be judged correctly (details will be described later).

  Therefore, the present invention maintains excellent bondability (for example, peel strength of 0.5 N / mm or more) between the resin film and the copper foil, and transmits the resin film portion remaining after the copper foil is chemically etched away. With regard to visibility, the ultimate goal is to provide an FPC with a high degree of freedom in the arrangement relationship between the resin film and the positioning marker while ensuring excellent transmission visibility, and provide a copper-clad laminate to obtain the FPC The primary purpose is to do.

(I) One aspect of the present invention is a copper-clad laminate in which a resin film and a copper foil are directly laminated, and a peel strength between the resin film and the copper foil is 0.5 N / mm or more, When a part of the copper foil is removed by chemical etching, in the resin film remaining after the chemical etching is removed, the formula “V _t = (T _t −T _d ) × C / 100” (T _t : total light transmission) rate (unit:%), T _d: diffuse transmittance (unit:%), C: transparency (units:%)) copper-clad laminate permeability visibility V _t being defined is "V _t ≧ 10%" in Provide a board.

In the copper-clad laminate according to the present invention described above, the present invention can be improved or changed as follows.
(I) A roughened copper plating layer is formed on the joint surface of the copper foil facing the resin film, and the average thickness of the roughened copper plating layer is 0.05 μm or more and 0.3 μm or less.
(Ii) The copper foil is a rolled copper foil, a base copper plating layer is formed between the copper foil and the roughened copper plating layer, and an average thickness of the base copper plating layer is 0.1 μm or more 0.6 μm or less.
(Iii) the transmission visibility V _t is "V _t ≧ 20%."

(II) Another aspect of the present invention is a flexible printed wiring board in which a part of the copper foil of the copper-clad laminate is chemically etched to form a circuit wiring, after the chemical etching is removed. in the remaining the resin films of, the expression _{"V t = (T t - T} d) × C / 100 " (T _t: total light transmittance (unit:%), T _d: diffuse transmittance (unit:%) , C: transparency (units:%)) transmitted visibility V _t as defined in to provide a flexible printed wiring board, which is a "V _t ≧ 10%."

In the flexible printed wiring board according to the present invention described above, the present invention can be improved or changed as follows.
(Iv) The transmission visibility V _t is “V _t ≧ 20%”.

  According to the present invention, excellent bondability between the resin film and the copper foil is maintained, and excellent transmission visibility is ensured with respect to the transmission visibility in the resin film portion remaining after the copper foil is chemically etched away. However, it is possible to provide an FPC having a high degree of freedom in the arrangement relationship between the resin film and the positioning marker. In addition, a copper clad laminate for obtaining the FPC can be provided.

It is a cross-sectional schematic diagram which shows the basic method (JIS K 7361, JIS K 7136) of the transmitted light measurement (calibration measurement, total light transmittance measurement, diffuse transmittance measurement) of a resin film. It is a photograph which shows an example of the transmission visibility in the resin film part after carrying out the chemical etching removal of the copper foil in the conventional copper clad laminated board, (a) The marker which carries out the transmission visual recognition is closely_contact | adhered and arrange | positioned under the resin film And (b) transmission visibility when a marker to be visually recognized is arranged with a gap (about 10 mm) under the resin film. It is the schematic diagram which showed the arrangement | positioning relationship between a resin film and a marker, and the optical path which permeate | transmits visually, (a) When the marker which permeate | transmits visually is arrange | positioned in close contact with the resin film, (b) Permeation | transmission This is a case where the marker to be visually recognized is arranged with a gap under the resin film. It is a cross-sectional schematic diagram which shows the basic method of the transparency measurement of a resin film. It is a cross-sectional schematic diagram which shows the structural example of the copper clad laminated board which concerns on this invention. It is a flowchart which shows an example of the manufacturing process of the copper clad laminated board which concerns on this invention. It is a SEM observation image of the cross-sectional microstructure near the interface of “underlying copper plating layer / rolled copper foil” in the surface-treated copper foils of Comparative Example 5 and Example 5, (a) Comparative Example 5, (b) Example 5 It is. It is a photograph which shows an example of the transmission visibility in the exposed polyimide film part after carrying out the chemical etching removal of the surface treatment copper foil in the FPC simulated sample of Example 5, (a) The marker which carries out the transmission visual recognition is under a polyimide film. And (b) transmission visibility when a marker to be visually recognized is arranged with a gap (about 10 mm) under the polyimide film.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. It should be noted that the present invention is not limited to the embodiments taken up here, and combinations and improvements can be appropriately made without departing from the technical idea of the invention.

(Problems in conventional technology and investigation of its causes)
As described above, the present inventors have been able to satisfy various requirements in FPC (for example, excellent bondability between the resin film and the copper foil, excellent transmission visibility in the resin film portion) after removing the copper foil by etching. The penetration visibility in the resin film part of was investigated in detail. First, a conventional method for measuring the transparency of a resin film (for example, total light transmittance T _t , diffuse transmittance T _d , haze H) was confirmed and examined.

  FIG. 1 is a schematic cross-sectional view showing a basic method (JIS K 7361, JIS K 7136) of transmitted light measurement (calibration measurement, total light transmittance measurement, diffuse transmittance measurement) of a resin film. As shown in FIG. 1, an integrating sphere for measuring transmitted light has an entrance opening for receiving a measurement light beam (incident light beam), an exit opening for emitting a parallel light beam, and a receiver opening for measuring the amount of light. And a compensation aperture (also referred to as a reflection measurement window) for canceling unwanted reflected light, and a light trap box is connected to the compensation aperture.

In the calibration measurement, a sample is not opened at the entrance opening, the exit opening is closed with a white plate, and the sample is placed at the compensation opening. Thereby, the environment including the reflected light from the sample can be calibrated. In total light transmittance measurement, a sample is placed at the entrance opening, the exit opening is closed with a white plate, and the compensation opening is opened. The incident light beam enters from the back of the sample (meaning the surface not facing the integrating sphere). Measure the light intensity. By comparing this with the light quantity of the calibration measurement, the total light transmittance T _t (%) of the sample is measured. In diffuse transmittance measurement, a sample is installed at the entrance opening, the exit opening is opened, and the compensation opening is closed with a white plate (white plate for haze compensation), and the amount of light is measured by entering the incident light beam from the back of the sample. To do. Since the parallel light beam that has passed through the sample passes through the exit opening, the diffuse transmittance T _d (%) is measured. The haze H (%) is calculated by the ratio of the diffuse transmittance T _{d to} the total light transmittance T _t (T _d / T _t × 100).

  FIG. 2 is a photograph showing an example of transmission visibility in the resin film portion after chemical etching removal of the copper foil in the conventional copper-clad laminate, and (a) a marker for visual recognition is placed under the resin film. Transmission visibility when arranged in close contact, and (b) transmission visibility when a marker for visual recognition is arranged with a gap (about 10 mm) under the resin film.

  As shown in FIG. 2 (a), when the marker to be seen through is placed in close contact with the bottom of the resin film, the characters displayed on the marker can be sufficiently visually recognized and discriminated. On the other hand, as shown in Fig. 2 (b), when the marker to be seen through is placed under a resin film with a gap (about 10 mm), the characters displayed on the marker are completely visible and discriminated. Can not. From this experiment, it was found that the transmission visibility through the resin film is strongly influenced by the arrangement relationship between the resin film and the marker (particularly, the distance between the resin film and the marker).

  In the process of mounting liquid crystal members and IC chips on the FPC, positioning is performed while the long FPC is continuously transported, so the FPC and the positioning marker are usually placed in order not to damage the FPC surface. An appropriate gap is set between them.

In the above experiment, only the positional relationship between the resin film and the marker is changed, so of course, an index indicating the transparency of the resin film (for example, total light transmittance T _t , diffuse transmittance T _d , haze) H) There is no change in itself. That is, when the arrangement relationship between the resin film and the marker is taken into consideration, it has been found that the transmission visibility through the resin film cannot be appropriately evaluated only with the conventional index indicating transparency.

  The reason why the transmission visibility through the resin film cannot be properly evaluated will be considered.

  FIG. 3 is a schematic diagram schematically showing an arrangement relationship between a resin film and a marker, and an optical path to be viewed through transmission. (A) When a marker to be viewed through transmission is placed in close contact with the resin film, (B) This is a case where the marker to be visually recognized is arranged with a gap below the resin film.

As shown in FIG. 3 (a), when the marker to be seen through is placed in close contact with the resin film, the marker is in close contact with the resin film. And reflection at the interface between the marker and the marker. In this case, the distance from the transmission through the resin film to the reflection at the marker surface can be regarded as substantially zero, and the diffused light (spread of light due to diffusion) when first transmitted through the resin film is taken into consideration. There is no need. In other words, it is considered that the light transmitted at the total light transmittance T _t is reflected almost as it is.

On the other hand, as shown in FIG. 3B, when the marker to be visually recognized is disposed with a gap under the resin film, the light transmitted through the resin film corresponds to the diffuse transmittance _Td . Only the light reflected from the marker surface while producing diffuse light and transmitted through the resin film again is detected. In other words, when there is a certain distance from the transmission through the resin film to the reflection at the marker surface, it is considered that light that travels straight through the resin film (that is, parallel rays) becomes important.

From the above considerations, the marker transmission visibility through the resin film means that the light that has passed through the resin film is reflected by the marker surface and is transmitted again through the resin film (or an observer such as a CCD camera). It was considered that the light that reciprocates through the resin film is the essence of transmission visibility. That is, the conventional index (for example, total light transmittance T _t , diffuse transmittance T _d , haze, etc.) that measures the light transmitted through the resin film only once in consideration that the light passing through the resin film should be taken into consideration. It was considered that the transmission visibility through the resin film could not be properly evaluated only with H).

(Indicator for judging transmission visibility through a resin film)
If there is no appropriate index for determining whether or not the transmission visibility is good, items to be controlled in order to improve the transmission visibility are not determined, which is a very big problem. In other words, in order to obtain a copper-clad laminate that satisfies the above-described requirements (coexistence of excellent bondability between the resin film and the copper foil and good transmission visibility through the resin film), at least the resin film An appropriate index that can determine whether or not the transmission visibility through the screen is good is required.

  From the above experiments and considerations, it has been found that light (parallel rays) that passes straight through the resin film and travels straight through the resin film is important for transmission visibility through the resin film. Therefore, the parallel light beam that passed through the resin film was examined in more detail.

  It is said that the parallel light transmitted through the resin film usually contains straight light and narrow-angle scattered light. Considering the importance of light passing through the resin film for transmission visibility through the resin film, if there is a certain distance between the resin film and the marker, even if it is a narrow angle, scattered light The light that passes through the resin film and goes straight and reflects straight (that is, straight light) is considered important. In addition, it is thought that the narrow angle scattered light in a parallel ray becomes a factor which blurs the outline of a marker in reflection on the marker surface.

Transparency C is an index of linear light (an index indicating the influence of narrow-angle scattered light). FIG. 4 is a schematic cross-sectional view showing a basic method for measuring the transparency of a resin film. As shown in FIG. 4, the transparency C is obtained by measuring the amount of parallel light transmitted through the sample with a ring sensor composed of a center sensor and an outer periphery sensor. The expression “C (%) = (I _c −I _r ) / ( I _c + I _r ) × 100 ”(where I _{c is the} received light amount of the center sensor, I _{r is the} received light amount of the ring sensor).

From a number of experiments and analysis, such as the indicators and the inventors Transparency described above, transparent visibility of indicators through the resin film (hereinafter, referred to as transmission visibility V _t, unit:%) is a resin film As a ratio of the linear light in the transmitted parallel rays, the formula “V _t = (T _t −T _d ) × C / 100” (T _t : total light transmittance (unit:%), T _d : diffuse transmittance (unit) :%), C: transparency (unit:%)). Thus, even if there is some distance between the resin film and the marker, by transmitting visibility V _t is controlled so as to satisfy a predetermined value, ensuring a good transmission visibility Can do. “T _t −T _d ” means the ratio of parallel rays transmitted through the resin film (for example, referred to as parallel ray transmittance T _p ).

[Copper-clad laminate structure]
FIG. 5 is a schematic cross-sectional view showing a structural example of a copper-clad laminate according to the present invention. As shown in FIG. 5, a copper clad laminate 10 according to the present invention is a two-layer copper clad laminate in which a copper foil 1 and a resin film 6 are laminated directly without a resin adhesive layer, A base copper plating layer 2, a roughened copper plating layer 3, and a rust prevention layer 4 are formed on the bonding surface of the copper foil 1 facing the film 6. Usually, the copper foil 1 to the antirust layer 4 are collectively referred to as a surface-treated copper foil 5.

  In addition, in FIG. 5, although the two-layer single-sided copper clad laminated board by which the copper foil 1 (or surface treatment copper foil 5) was laminated | stacked on the single side | surface of the resin film 6, the copper clad laminated board which concerns on this invention, It may be a two-layer double-sided copper-clad laminate in which copper foil 1 (or surface-treated copper foil 5) is laminated on both surfaces of the resin film 6.

(Copper foil)
The copper foil 1 is not particularly limited, and a conventional copper foil (for example, an electrolytic copper foil or a rolled copper foil) can be used. When extremely excellent bending characteristics (for example, bending characteristics of 1 million times or more) are required in FPC, it is preferable to use a rolled copper foil. In addition, as raw materials, pure copper (for example, tough pitch copper (JIS H 3100 C1100) and oxygen-free copper (JIS H 3100 C1020)), and dilute copper alloys with a small amount of tin (Sn) or silver (Ag) added to pure copper Is often used. Hereinafter, a case where a rolled copper foil is used as the copper foil 1 will be described unless otherwise specified.

(Underlying copper plating layer)
The base copper plating layer 2 is a layer that is formed immediately above the copper foil 1 and serves as a base for the roughened copper plating layer 3. In the present invention, by providing a predetermined base copper plating layer 2, the roughened shape (thickness (unevenness) direction or in-plane direction shape) of the roughened copper plating layer 3 formed thereon is equalized. Can be stabilized. The average thickness of the base copper plating layer 2 of the present invention is preferably 0.1 μm or more and 0.6 μm or less. When the average thickness is less than 0.1 μm, the effect of the underlying copper plating layer becomes insufficient. If the average thickness exceeds 0.6 μm, the effect is saturated and the process cost is wasted. The material is preferably the same composition as pure copper or copper foil 1.

  In the state of the surface-treated copper foil that has not been subjected to the recrystallization annealing treatment, the underlying copper plating layer 2 of the present invention is different from the polycrystalline grains constituting the copper foil 1 in the polycrystalline grains constituting the underlying copper plating layer 2 It has the characteristic of having a crystal orientation relationship. The polycrystalline grains constituting the copper foil 1 have a microstructure in which the {022} plane of the copper crystals is preferentially oriented at least on the rolling surface (so-called rolling texture: X-ray diffraction by the 2θ / θ method with respect to the rolling surface ( When XRD) measurement is performed, the {022} plane appears as a main peak (strongest peak) and the {002} plane appears as a second peak.

  On the other hand, the polycrystalline grains constituting the base copper plating layer 2 have a microstructure different from the rolling texture. Specifically, when XRD measurement is performed on the surface of the underlying copper plating layer 2, the {111} plane and / or the {002} plane of the copper crystal is preferentially oriented. The copper foil 1 is changed to a microstructure (so-called cubic texture) in which the {002} plane of the copper crystal is preferentially oriented by a recrystallization annealing process (for example, CCL forming step).

  Further, the base copper plating layer 2 of the present invention is an average of the polycrystalline grains constituting the base copper plating layer 2 when the cross-sectional structure observation is performed in the state of the surface-treated copper foil not subjected to the recrystallization annealing treatment. The thickness is larger than the average thickness of the polycrystalline grains constituting the copper foil 1.

  In the present invention, the formation method of the base copper plating layer 2 is greatly different from the prior art (details will be described later), and an obvious effect is exhibited with respect to the final “transmission visibility at the resin film portion”. However, unfortunately, the mechanism by which the above characteristics of the underlying copper plating layer 2 have an effect on “transparency visibility at the resin film portion” has not been elucidated at this stage.

(Roughened copper plating layer)
The roughened copper plating layer 3 is formed immediately above the base copper plating layer 2. The roughened shape of the roughened copper plating layer 3 directly affects “bondability between the resin film and the copper foil” and “transparency visibility at the resin film portion”. The average thickness of the roughened copper plating layer 3 is preferably 0.05 μm or more and 0.3 μm or less. When the average thickness is less than 0.05 μm, the bondability between the resin film 6 and the surface-treated copper foil 5 becomes insufficient. When the average thickness exceeds 0.3 μm, the transmission visibility of the resin film 6 after the surface-treated copper foil 5 is removed by chemical etching becomes insufficient. Except for the average thickness specification, conventional techniques can be used.

(Rust prevention layer)
The rust prevention layer 4 is formed immediately above the roughened copper plating layer 3. The rust prevention layer 4 is not an essential layer in the present invention, but is a layer often formed in FPC (and copper clad laminate for FPC). There is no particular limitation on the configuration of the rust prevention layer 4, and a conventional technique can be used. For example, nickel plating layer (average thickness 9 nm to 50 nm), zinc plating layer (average thickness 1 nm to 10 nm), trivalent chromium conversion treatment layer (average thickness 1 nm to 10 nm), A silane coupling treatment layer (molecular layer level thickness) is laminated in this order. As in the prior art, the antirust layer 4 may be provided on the surface opposite to the bonding surface of the copper foil 1 facing the resin film 6.

(Resin film)
The resin film 6 is a layer that becomes a flexible substrate in the FPC. There is no particular limitation on the material of the resin film 6, and the conventional technology can be used. For example, a polyimide film is preferably used.

When the surface-treated copper foil 5 is removed by chemical etching, the copper-clad laminate 10 according to the present invention has a formula “V _t = (T _t −T _d ) × C in the remaining resin film 6 after chemical etching removal. / 100 "(T _t: total light transmittance (unit:%), T _d: diffuse transmittance (unit:%), C: transparency (units:%)) transmitted visibility V _t being defined by the" V _t ≧ 10% ”. Further, the peel strength between the resin film 6 and the surface-treated copper foil 5 is 0.5 N / mm or more.

[Manufacturing method of copper clad laminate]
The manufacturing method of the copper clad laminated board which concerns on this invention is demonstrated using FIG. FIG. 6 is a flowchart showing an example of a manufacturing process of the copper clad laminate according to the present invention. In addition, below, description of a washing | cleaning process and a drying process may be abbreviate | omitted, However, It is preferable that these processes are suitably performed as needed.

(S10) Copper foil preparation process In this process, the copper foil 1 is prepared. As described above, there is no particular limitation on the copper foil 1 itself, and since conventional copper foil (for example, electrolytic copper foil and rolled copper foil) can be used, the copper foil preparation method is not particularly limited, Conventional methods can be used.

(S20) Base copper plating layer forming step In this step, the base copper plating layer 2 is formed immediately above the copper foil 1. Before forming the base copper plating layer 2, it is preferable to clean the surface of the copper foil 1 by performing electrolytic degreasing treatment and pickling treatment. The electrolytic degreasing treatment is a treatment in which the copper foil 1 is immersed in an alkaline aqueous solution to perform cathodic electrolytic degreasing. As the alkaline aqueous solution, for example, an aqueous solution containing sodium hydroxide (NaOH) at 20 g / L to 60 g / L and sodium carbonate (Na ₂ CO ₃ ) at 10 g / L to 30 g / L is used. Can do.

The pickling treatment is a treatment of immersing the copper foil 1 that has been subjected to electrolytic degreasing treatment in an acidic aqueous solution to neutralize the alkali component remaining on the surface of the copper foil 1 and remove the copper oxide film. As the acidic aqueous solution, for example, an aqueous solution containing sulfuric acid (H ₂ SO ₄ ) of 120 g / L or more and 180 g / L or less, a citric acid (C ₆ H ₈ O ₇ ) aqueous solution, a copper etching solution, or the like can be used. .

The formation of the base copper plating layer 2 is performed by electrolytic treatment using the copper foil 1 as a cathode in an acidic copper plating bath mainly composed of copper sulfate and sulfuric acid. The liquid composition, liquid temperature, electrolysis conditions, and average thickness of the base copper plating layer of the acidic copper plating bath are preferably selected from the following ranges, for example.
Copper sulfate pentahydrate: 20 g / L or more and 300 g / L or less (preferably 50 g / L or more and 300 g / L or less)
Sulfuric acid: 10 g / L or more and 200 g / L or less (more preferably 30 g / L or more and 200 g / L or less)
Additive: Add specified organic additive Additive temperature: 15 ° C or more and 50 ° C or less Current density: 2 A / dm ² or more and 15 A / dm ² or less
Treatment time: 1 second or more and 30 seconds or less Average thickness: 0.1 μm or more and 0.6 μm or less.

  Examples of the predetermined organic additive include a compound having a mercapto group (for example, 3-mercapto-1-sulfonic acid (MPS), bis (3-sulfopropyl) disulfide (SPS)), a surfactant (for example, Additives combining polyethylene glycol (PEG), polypropylene glycol (PPG), polyoxyalkylene ether), leveling agents (eg diallyldialkylammonium alkyl sulfate), and aqueous solutions containing chloride ions (eg aqueous hydrochloric acid) Is used.

  Such an additive can be prepared by blending a predetermined amount of constituent reagents (commercially available products). Also, plating chemicals that are pre-mixed with components (for example, plating chemicals containing a compound having a mercapto group, plating chemicals containing a surfactant, and plating containing a leveling agent) It is also possible to use a mixture of medicinal solution). Furthermore, it is also possible to mix and use a chemical solution for plating in which constituent components are mixed in advance and a constituent reagent (commercial product).

  More specifically, as the concentration of the compound having a mercapto group in the base copper plating bath, for example, in the case of SPS, 10 mg / L or more and 60 mg / L or less is preferable, 10 mg / L or more and 45 mg / L or less Is more preferable, and 10 mg / L or more and 30 mg / L or less is still more preferable. If the SPS concentration is less than 10 mg / L, the effects of the present invention may not be sufficiently obtained. On the other hand, when the concentration of SPS exceeds 60 mg / L, the operational effects of the present invention are saturated and wasteful material costs are generated.

  As the surfactant, for example, a CU-BRITE TH-R III (registered trademark) series surfactant chemical solution manufactured by Ebara Eugelite Co., Ltd. can be used. In this case, the addition concentration in the base copper plating bath is preferably 1 mL / L or more and 5 mL / L or less.

  As the leveling agent, for example, a leveling agent chemical solution mainly composed of CU-BRITE TH-R III (registered trademark) series polymer hydrocarbons manufactured by Ebara Eugelite Co., Ltd. can be used. In this case, the addition concentration in the base copper plating bath is preferably 3 mL / L or more and 10 mL / L or less.

  As an aqueous solution containing chloride ions, for example, commercially available hydrochloric acid (hydrogen chloride concentration: 35% to 37%) can be used. In this case, the addition concentration in the base copper plating bath is preferably 0.05 mL / L or more and 0.3 mL / L or less.

  Here, an organic additive itself containing a compound having a mercapto group, a surfactant, a leveling agent, and a chloride ion has been conventionally known as a brightener in copper plating, but is added and used as a brightener. The concentration (recommended concentration) is usually about 0.5 to 1.5 mg / L. On the other hand, the concentration of the organic additive (compound having a mercapto group) in the present invention is 10 to 60 mg / L, which is characterized by an order of magnitude higher than that for ordinary brightener applications.

  Although specific examples will be described later, the base copper plating layer 2 formed by the manufacturing method of the present invention has the above-described characteristics, and the copper clad laminate 10 incorporating the base copper plating layer 2 of the present invention is In addition, it can be said that the transmission visibility in the resin film 6 after the surface-treated copper foil 5 is removed by chemical etching is good, and it is clearly effective. However, unfortunately, the mechanism by which the characteristics of the base copper plating layer 2 of the present invention have an effect on “transparency visibility at the resin film portion” has not been elucidated at this stage.

(S30) Roughened copper plating layer forming step In this step, the roughened copper plating layer 3 is formed immediately above the base copper plating layer 2. The roughened copper plating layer 3 is formed by electrolytic treatment using copper foil 1 as a cathode in an acidic copper plating bath mainly composed of copper sulfate and sulfuric acid, and the roughened grains are deposited on the surface of the underlying copper plating layer 2.・ Grow it up. The liquid composition, liquid temperature, electrolysis conditions, and average thickness of the roughened copper plating layer of the acidic copper plating bath are preferably selected from the following ranges, for example.
Copper sulfate pentahydrate: 20 g / L or more and 300 g / L or less Sulfuric acid: 10 g / L or more and 200 g / L or less Other components: One or more selected from Fe, Mo, Ni, Co, Cr, Zn, W Liquid temperature: 15 ° C or higher and 50 ° C or lower Current density: 20 A / dm ² or higher and 100 A / dm ² or lower (exceeding the limit current density)
Treatment time: 0.3 seconds or more and less than 2.0 seconds Average thickness: 0.05 μm or more and 0.3 μm or less.

  Since the formation of the roughened copper plating layer 3 is performed by plating with a current density exceeding the limit current density (so-called burnt plating), it is necessary to add Fe to the plating bath so that the coarsening grains that precipitate and grow do not become excessively large. It is preferable to add at least one sulfate selected from Mo, Ni, Co, Cr, Zn and W. For example, iron sulfate heptahydrate is added to the plating bath in the range of 10 g / L to 30 g / L. This facilitates control of the roughened shape. The roughened shape is not particularly limited as long as each roughened grain is uniformly deposited and grown in the uneven direction or in-plane direction, and may be a grain shape, a hump shape, or a dendritic shape. However, it may be needle-shaped.

(S40) Rust prevention layer formation process At this process, the rust prevention layer 4 is formed on the roughening copper plating layer 3 directly. As described above, the rust prevention layer 4 is not an essential layer in the present invention, but here, an example of a process in the case of forming the rust prevention layer 4 will be described. The formation of the rust preventive layer 4 includes a nickel plating process, a galvanizing process, a trivalent chromium chemical conversion process (chromate process), and a silane coupling process.

The nickel plating treatment (formation of the nickel plating layer) is preferably selected from the following plating conditions, for example.
Nickel sulfate hexahydrate: 280 g / L or more and 320 g / L or less Nickel chloride: 40 g / L or more and 50 g / L or less Boric acid: 40 g / L or more and 60 g / L or less Other components: Other metal elements ( For example, Co) may be added to form a Ni-Co alloy plating layer. Liquid temperature: 30 ° C to 60 ° C Current density: 0.5 A / dm ^{2 to} 10 A / dm ²
Treatment time: 1 second to 10 seconds Average thickness: 9 nm to 50 nm

The galvanizing treatment (formation of the galvanized layer) is preferably selected from the following plating conditions, for example.
Zinc sulfate: 80 g / L or more and 120 g / L or less Sodium sulfate: 60 g / L or more and 80 g / L or less Other components: Other metal elements (for example, Cu) may be added to form a Zn-Cu alloy plating layer Liquid temperature: 15 ° C to 35 ° C Current density: 0.1 A / dm ² or more and 10 A / dm ² or less
Treatment time: 1 second or more and 10 seconds or less Average thickness: 1 nm or more and 10 nm or less.

The trivalent chromium chemical conversion treatment (formation of the trivalent chromium chemical conversion treatment layer) is preferably selected from the following processing conditions, for example.
Treatment liquid: Trivalent chromium reactive chromate liquid (trivalent chromium ion concentration: 70 mg / L or more and less than 500 mg / L in terms of metallic chromium. There is no particular limitation on the source of trivalent chromium ions. For example, nitric acid Chromium, chromium sulfate, chromium chloride)
Liquid temperature: 15 ° C to 40 ° C Treatment time: 3 seconds to 30 seconds Average thickness: 1 nm to 10 nm

The silane coupling treatment (formation of the silane coupling treatment layer) is preferably selected from the following treatment conditions, for example.
Treatment liquid: Silane coupling liquid (Select one suitable for the flexible base material to be laminated. For example, when the flexible base material is made of polyimide, the main material is aminosilane or aminopropyltrimethoxysilane. Preferably selected)
Liquid temperature: 15 ° C to 35 ° C Treatment time: 3 seconds to 40 seconds Drying temperature: 100 ° C to 300 ° C Drying time: 5 seconds to 35 seconds Thickness: Molecular layer level.

  Through the steps S10 to S40, the surface-treated copper foil 5 (surface-treated copper foil for copper-clad laminate) suitable for the copper-clad laminate 10 according to the present invention is completed.

(S50) Flexible base material laminating step In this step, the surface-treated copper foil 5 and the resin film 6 are laminated. In the case of a two-layer copper-clad laminate, the surface-treated copper foil 5 and the resin film 6 are directly laminated by being heated and pressed without going through the resin adhesive layer. The heating / pressing conditions are appropriately set depending on the properties of the resin film 6, but are preferably selected from the following ranges, for example.
Temperature: 150 ° C to 400 ° C Pressure: 0.5 MPa to 30 MPa Holding time: 1 minute to 120 minutes

  By heating in this step, the copper foil 1 (rolled copper foil) is usually recrystallized and tempered into a cubic texture. Thereby, the bending characteristic (final FPC bending characteristic) of the copper foil 1 is dramatically improved. In addition, in order to prevent undesired deformation (elongation, wrinkle, breakage, etc.) of the surface-treated copper foil 5 during handling in this step, the surface-treated copper foil 5 (at least the copper foil 1) to be provided in this step is reused. It is preferable that the crystal structure is not tempered (at least not annealed).

  In the above description, the case where the pre-molded resin film 6 is used as the flexible base material has been described, but the present invention is not limited thereto. For example, with a lamination method (manufacture of a two-layer copper-clad laminate by a casting method), a varnish that becomes polyimide is applied to the joint surface of the surface-treated copper foil 5 and the varnish is cured by heat treatment to form a flexible substrate. There may be.

  Through the above steps, the copper clad laminate 10 according to the present invention is completed.

(FPC manufacturing method)
FPC is manufactured by performing the formation process of a circuit wiring with respect to the copper clad laminated board 10 obtained above. The step of forming the circuit wiring is usually performed by chemically removing a part of the surface-treated copper foil 5 of the copper clad laminate 10. It is one of the objects of the present invention to ensure good transmission visibility in the resin film 6 portion where the surface-treated copper foil 5 is removed by etching.

  EXAMPLES Hereinafter, although this invention is demonstrated in more detail based on an Example, this invention is not limited to these.

[Production of surface-treated copper foil of Example 1]
The surface-treated copper foil 5 of Example 1 was produced by the following procedure. First, a rolled copper foil (thickness 11 μm) made of oxygen-free copper was prepared as the copper foil 1. Next, electrolytic degreasing treatment and pickling treatment were performed on the copper foil 1 under the following conditions, respectively, to clean the surface of the copper foil 1. After the pickling treatment, the copper foil 1 was washed with water.

(Electrolytic degreasing)
Solution: Aqueous solution containing 40 g / L sodium hydroxide and 20 g / L sodium carbonate Temperature: 40 ° C
Current density: 10 A / dm ²
Processing time: 10 seconds.

(Pickling treatment)
Solution: Aqueous solution containing 150 g / L sulfuric acid Liquid temperature: Room temperature (25 ° C)
Processing time: 10 seconds.

Next, the base copper plating layer 2 was formed on one surface of the copper foil 1 under the following plating conditions, and then washed with water.
(Under copper plating treatment)
Copper sulfate pentahydrate: 170 g / L
Sulfuric acid: 70 g / L
Additive 1: SPS 30 mg / L as an organic sulfur compound
Additive 2: CU-BRITE TH-R III manufactured by Sugawara Eugene Corporation as a surfactant
Series of surfactant chemicals 3 mL / L
Additive 3: CU-BRITE TH-R III manufactured by Sugawara Eugene Corporation as a leveling agent
Leveling chemicals based on high-molecular-weight hydrocarbons of the series 5 mL / L
Additive 4: Hydrochloric acid reagent stock solution as an aqueous solution containing chloride ions 0.15 mL / L
Liquid temperature: 35 ℃
Current density: 7 A / dm ²
Processing time: 10 seconds Average thickness: 0.1 μm.

Next, a roughened copper plating layer 3 was formed on the base copper plating layer 2 under the following plating conditions, and then washed with water.
(Roughening copper plating treatment)
Copper sulfate pentahydrate: 100 g / L
Sulfuric acid: 70 g / L
Other ingredients: Iron sulfate heptahydrate 20 g / L
Liquid temperature: 30 ℃
Current density: 60 A / dm ²
Processing time: 0.5 seconds Average thickness: 0.05 μm.

  Next, a rust prevention layer 4 was formed on the copper foil 1 on which the roughened copper plating layer 3 was formed under the following plating conditions. A water wash was performed between and at the end of each treatment. Nickel plating treatment, zinc plating treatment and trivalent chromium chemical conversion treatment are performed on both sides of the copper foil 1, and silane coupling treatment is performed on the joint surface of the copper foil 1 (the roughened copper plating layer 3 side). I only went to it.

(Nickel plating treatment)
Nickel sulfate hexahydrate: 300 g / L
Nickel chloride: 45 g / L
Boric acid: 50 g / L
Liquid temperature: 50 ℃
Current density: 2 A / dm ²
Processing time: 5 seconds Average thickness: 20 nm.

(Zinc plating treatment)
Zinc sulfate: 90 g / L
Sodium sulfate: 70 g / L
Liquid temperature: 30 ℃
Current density: 1.5 A / dm ²
Processing time: 4 seconds Average thickness: 7 nm.

(Trivalent chromium conversion treatment)
Treatment solution: Trivalent chromium reactive chromate solution using chromium nitrate as the source of trivalent chromium ions (Trivalent chromium ion concentration: 300 mg / L in terms of metallic chromium)
Liquid temperature: 30 ℃
Processing time: 5 seconds Average thickness: 5 nm.

(Silane coupling treatment)
Treatment liquid: Silane coupling liquid containing 5% 3-aminopropyltrimethoxysilane Liquid temperature: Room temperature (25 ° C)
Treatment time: 5 seconds Heat drying: 200 ° C, 15 seconds.

[Production of surface-treated copper foils of Examples 2 and 3]
The surface-treated copper foil 5 of Examples 2 and 3 was the same as the surface-treated copper foil 5 of Example 1 described above except that the average thickness of the base copper plating layer 2 was 0.3 μm and 0.6 μm, respectively. Produced.

[Production of surface-treated copper foil of Example 4]
The surface-treated copper foil 5 of Example 4 has an average thickness of the roughened copper plating layer 3 of 0.11 μm, except that the roughened grains of the roughened copper plating layer 3 are formed larger than in Example 1. It was produced under the same conditions as the surface-treated copper foil 5 of Example 1 described above.

[Production of surface-treated copper foils of Examples 5 and 6]
The surface-treated copper foil 5 of Examples 5 and 6 was under the same conditions as the surface-treated copper foil 5 of Example 4 described above, except that the average thickness of the base copper plating layer 2 was 0.3 μm and 0.6 μm, respectively. Produced.

[Production of surface-treated copper foil of Example 7]
In the surface-treated copper foil 5 of Example 7, the average thickness of the roughened copper plating layer 3 was set to 0.3 μm, and the roughened grains of the roughened copper plating layer 3 were formed to be larger than that of Example 4. These were produced under the same conditions as the surface-treated copper foil 5 of Example 1 described above.

[Production of surface-treated copper foils of Examples 8 and 9]
The surface-treated copper foil 5 of Examples 8 and 9 was under the same conditions as the surface-treated copper foil 5 of Example 7 described above, except that the average thickness of the base copper plating layer 2 was 0.3 μm and 0.6 μm, respectively. Produced.

[Production of surface-treated copper foils of Comparative Examples 1 and 2]
The surface-treated copper foil of Comparative Example 1 was the same as that described above except that the average thickness of the roughened copper plating layer 3 was 0.03 μm and the roughened grains of the roughened copper plating layer 3 were formed smaller than in Example 2. The surface-treated copper foil 5 of Example 2 was prepared under the same conditions. In Comparative Example 1, the influence of the average thickness of the roughened copper plating layer 3 can be observed. Further, the surface-treated copper foil of Comparative Example 2 was produced under the same conditions as the surface-treated copper foil of Comparative Example 1 except that the predetermined organic additive was not added in forming the base copper plating layer 2. . In Comparative Example 2, in addition to Comparative Example 1, the influence of a predetermined organic additive in the formation of the base copper plating layer 2 can be observed.

[Production of surface-treated copper foil of Comparative Examples 3 and 4]
In the surface-treated copper foil of Comparative Example 3, the average thickness of the roughened copper plating layer 3 was set to 0.35 μm, and the roughened grains of the roughened copper plating layer 3 were formed larger than in Example 8, It was produced under the same conditions as the surface-treated copper foil 5 of Example 8 described above. In Comparative Example 3, the influence of the average thickness of the roughened copper plating layer 3 can be observed. The surface-treated copper foil of Comparative Example 4 was produced under the same conditions as the surface-treated copper foil of Comparative Example 3 except that the predetermined organic additive was not added in forming the base copper plating layer 2. . In Comparative Example 4, in addition to Comparative Example 3, the influence of a predetermined organic additive in the formation of the base copper plating layer 2 can be observed.

[Production of surface-treated copper foil of Comparative Example 5]
The surface-treated copper foil of Comparative Example 5 was produced under the same conditions as the surface-treated copper foil 5 of Example 5 except that the predetermined organic additive was not added in forming the base copper plating layer 2. In Comparative Example 5, the influence of a predetermined organic additive in the formation of the base copper plating layer 2 can be observed.

[Production of surface-treated copper foil of Comparative Example 6]
The surface-treated copper foil of Comparative Example 6 is the surface-treated copper foil of Example 5 except that no iron component (iron sulfate heptahydrate) was added as the other component in forming the roughened copper plating layer 3. It was produced under the same conditions. In Comparative Example 6, the influence of other components in the formation of the roughened copper plating layer 3 can be observed.

[Production of surface-treated copper foils of Comparative Examples 7 to 9]
The surface-treated copper foils of Comparative Examples 7 to 9 were produced under the same conditions as the surface-treated copper foils 5 of Examples 1, 4 and 7, respectively, except that the base copper plating layer 2 was not formed. In Comparative Examples 7 to 9, the influence of the presence or absence of the base copper plating layer 2 can be observed.

  A list of conditions for producing the surface-treated copper foils of Examples 1 to 9 and Comparative Examples 1 to 9 is shown in Table 1 described later.

[Preparation of copper-clad laminate]
Using the surface-treated copper foils of Examples 1 to 9 and Comparative Examples 1 to 9, copper-clad laminates of Examples 1 to 9 and Comparative Examples 1 to 9 were produced under the following conditions. In addition, as a copper clad laminated board, the roughened surface (surface on the side where the roughened copper plating layer 3 is formed) of the surface-treated copper foil is opposed to the resin film, and the surface-treated copper foil is laminated on both surfaces of the resin film. A two-layer double-sided copper-clad laminate was prepared.
Resin film: Polyimide film (thickness 25 μm, Kaneka Corporation, Pixio)
Temperature: 300 ° C
Pressure: 5 MPa
Retention time: 15 minutes.

[FPC sample preparation]
FPC simulated samples in which a part of both surface-treated copper foils were removed by chemical etching with respect to the copper clad laminates of Examples 1 to 9 and Comparative Examples 1 to 9, and both surfaces of the polyimide film were exposed in a predetermined area ( Examples 1 to 9 and Comparative Examples 1 to 9) were produced. Chemical etching removal was performed by ferric chloride spray etching.

[Survey of properties of surface-treated copper foil and FPC simulation sample]
(1) XRD measurement of base copper plating layer of surface-treated copper foil In the surface-treated copper foils of Examples 1 to 9 and Comparative Examples 1 to 9, the surface of the base copper plating layer was formed at the stage where the base copper plating layer was formed. On the other hand, XRD measurement was performed using an X-ray diffractometer (Rigaku Corporation, model: Ultima IV). The results are also shown in Table 1 below. Note that the same XRD measurement was performed on the surface of the rolled copper foil, and it was separately confirmed that it was preferentially oriented on the {022} _Cu surface (having a rolled texture).

(2) Microstructure observation of the surface-treated copper foil of the surface-treated copper foil For the surface-treated copper foils of Examples 1 to 9 and Comparative Examples 1 to 9, using a scanning electron microscope (SEM), the surface copper-plated The cross-sectional microstructure near the layer / rolled copper foil interface was observed. Moreover, from the photographed SEM image, the average thickness of the polycrystalline grains constituting the rolled copper foil and the average thickness of the polycrystalline grains constituting the base copper plating layer were determined. The results will be described later.

(3) Measurement of surface roughness of roughened copper plating layer of surface-treated copper foil In the surface-treated copper foils of Examples 1 to 9 and Comparative Examples 1 to 9, the roughened copper plating layer was formed at the stage where the roughened copper plating layer was formed. The surface roughness of the plating layer was measured. Using a surface roughness measuring machine (Kosaka Laboratory Ltd., model: SE500) as a measuring device, ten-point average roughness Rzjis (JIS B 0601: 2001) was measured. The measurement conditions were a stylus diameter of 2 μm, a measurement speed of 0.2 mm / s, a measurement length of 4 mm, a sampling reference length of 0.8 mm, and a load of 0.75 mN or less. The results are also shown in Table 1 below.

(4) Transmission visibility measurement in the exposed polyimide film part For the exposed polyimide film part in the FPC simulated samples of Examples 1-9 and Comparative Examples 1-9, a haze meter (BYK Gardner-Haze-Guard Plus, stock) The total light transmittance T _t , diffuse transmittance T _d , and transparency C of the polyimide film are measured using the Toyo Seiki Seisakusho Co., Ltd., and the parallel light transmittance T _p and the transmission visibility V _t are defined as described above. It calculated using. The results are shown in Table 2 below.

(5) Peel strength measurement between surface-treated copper foil and polyimide film For the portion (circuit wiring portion) where the surface-treated copper foil remains in the FPC simulated samples of Examples 1 to 9 and Comparative Examples 1 to 9 The peel strength was measured according to JIS C6481. The results are also shown in Table 2 below.

(6) Experiment for confirming transmission visibility in exposed polyimide film portion A marker for transparent viewing is placed under the exposed polyimide film portion in the FPC simulated samples of Examples 1 to 9 and Comparative Examples 1 to 9, and the marker The distance between the film and the polyimide film was changed from “0 mm to about 10 mm”, and the transmission visibility through the polyimide film was visually confirmed.

As described above, it was confirmed that the surface (rolled surface) of the copper foil 1 is preferentially oriented to the {022} _Cu surface and has a rolled texture. In contrast, as shown in Table 1, in the base copper plating layer 2 of the surface-treated copper foil 5 of Examples 1 to 9, the surface is preferentially oriented to the {111} _Cu plane and / or the {002} _Cu plane. Thus, it was confirmed that the copper foil 1 had a crystal orientation different from the rolled surface.

Also in Comparative Examples 1, 3, and 6 in which a predetermined organic additive was used in the formation of the base copper plating layer 2, the surface of the base copper plating layer 2 was preferentially oriented in the {111} _Cu plane. On the other hand, in Comparative Examples 2, 4, and 5 in which the predetermined organic additive was not used in the formation of the base copper plating layer 2, the surface of the base copper plating layer 2 was the same as the rolled surface of the copper foil 1 {022} _Cu It was preferentially oriented on the surface.

  In addition, it was observed that the base copper plating layer 2 formed using a predetermined organic additive was recrystallized at room temperature because the crystal orientation was observed to change over time. It was considered. Therefore, the above XRD measurement is performed after a time (for example, 3 days) when the change is considered to be sufficiently completed in consideration of the change with time of the crystal orientation. On the other hand, in the base copper plating layer 2 formed without using a predetermined organic additive, no change with time in the crystal orientation was observed.

  FIG. 7 is a SEM observation image of a cross-sectional microstructure near the interface of “underlying copper plating layer / rolled copper foil” in the surface-treated copper foils of Comparative Example 5 and Example 5, (a) Comparative Example 5, (b) ) Example 5. As shown in FIGS. 7A and 7B, in either case, the copper foil 1 is composed of flat polycrystalline grains, and the average thickness of the polycrystalline grains is about 0.07 μm. It was estimated.

  When the microstructures of the underlying copper plating layer 2 are compared, it can be seen that there is a large difference between Comparative Example 5 and Example 5. As shown in FIG. 7A, the polycrystalline grains constituting the base copper plating layer 2 of Comparative Example 5 have the same flat shape as those of the copper foil 1, and the polycrystalline of the copper foil 1 It has a microstructure as if it is epitaxially grown from grains. Therefore, the average thickness of the polycrystalline grains constituting the base copper plating layer 2 of Comparative Example 5 was estimated to be about 0.07 μm, as with the copper foil 1.

  On the other hand, as shown in FIG. 7B, it was confirmed that the polycrystalline grains constituting the base copper plating layer 2 of Example 5 had a microstructure different from those of the copper foil 1. . Further, the average thickness of the polycrystalline grains constituting the base copper plating layer 2 of Example 5 was estimated to be about 0.15 μm, which was confirmed to be larger than that of the copper foil 1.

  Regarding the surface roughness of the roughened copper plating layer 3, as shown in Table 1, in the surface-treated copper foils of Examples 1 to 9 and Comparative Examples 1 to 9, no particular difference was found. In other words, it is difficult to control and pass / fail judgment of the characteristics described later (particularly, transmission visibility through a resin film exposed by chemical etching removal) with a general index (here Rzjis) indicating the surface roughness of a metal. It was confirmed that there was.

As shown in Table 2, the FPC simulated samples of Examples 1 to 9 had high parallel light transmittance T _p and transparency C, and as a result, high transmission visibility V _t was obtained. Moreover, it was confirmed that the transmission visibility was confirmed through visual observation through a polyimide film.

  FIG. 8 is a photograph showing an example of transmission visibility in an exposed polyimide film portion after chemical etching removal of the surface-treated copper foil in the FPC simulated sample of Example 5, and (a) a marker for visual recognition of transmission is The transmission visibility when arranged in close contact with the polyimide film, and (b) the transmission visibility when the marker for visual recognition is arranged with a gap (about 10 mm) under the polyimide film. As shown in FIGS. 8A and 8B, the character displayed on the marker can be sufficiently visually recognized and determined in any case.

In addition, FIG. 2 mentioned above is a result of the transmission visibility through the polyimide film in the FPC simulated sample of Comparative Example 5. Comparing FIG. 2 and FIG. 8, the difference in transmission visibility through the polyimide film is obvious. From various transparent visibility confirmation experiment, in order to ensure sufficient transmission visibility, the transmittance visibility V _t was confirmed to be required at least 10% or more.

  Regarding the peel strength of the circuit wiring part (bondability between the resin film and the copper foil), any of the FPC simulated samples of Examples 1 to 9 shows 0.5 N / mm or more, and sufficiently satisfies the required characteristics. It was confirmed.

The FPC simulated samples of Comparative Examples 1 and 2 are samples in which the average thickness of the roughened copper plating layer 3 was made thinner than that of the present invention (the roughened grains of the roughened copper plating layer 3 were formed smaller), Although high transmission visibility V _t (good transmission visibility) was exhibited, the peel strength of the circuit wiring portion was insufficient. Further, the FPC simulated sample of Comparative Example 2 does not use a predetermined organic additive in the formation of the base copper plating layer 2, and has a diffusion transmittance T _{d that} is higher than that of the FPC simulated sample of Comparative Example 1. The transparency C was greatly decreased.

The FPC simulated samples of Comparative Examples 3 and 4 are samples in which the average thickness of the roughened copper plating layer 3 is made thicker than specified in the present invention (the roughened grains of the roughened copper plating layer 3 are formed larger). although showed high peel strength, permeability visibility V _t is decreased significantly. Further, when Comparative Example 3 and Comparative Example 4 were compared, there was a large difference in transparency C.

By comparing the FPC simulated sample of Comparative Example 5 with Example 5, the influence of a predetermined organic additive in the formation of the base copper plating layer 2 can be observed. As a result, in Comparative Example 5, the diffuse transmittance _Td was increased and the transparency C was greatly decreased. In other words, like the method for producing a surface-treated copper foil in the present invention, a resin exposed by etching in the final FPC by adding a predetermined organic additive when forming the base copper plating layer 2 It is considered that the diffuse transmittance _Td of the film can be reduced and the transparency C can be improved.

By comparing the FPC simulated sample of Comparative Example 6 with Example 5, the influence of other components in the formation of the roughened copper plating layer 3 can be observed. As a result, in Comparative Example 6, the diffuse transmittance T _d was increased. This may be caused by the fact that the sizes of the individual roughened grains are not uniform in the formation of the roughened copper plating layer 3.

The FPC simulated samples of Comparative Examples 7 to 9 are samples in which the base copper plating layer 2 is not formed with the surface-treated copper foil, and the total light transmittance T _t is reduced as compared with Examples 1, 4 and 7. However, the diffuse transmittance _Td was increased and the transparency C was greatly decreased. From this result, it is considered that the significance of forming the base copper plating layer 2 in the surface-treated copper foil is great.

  As described above, the FPC produced from the copper-clad laminates of Examples 1 to 9 according to the present invention maintains excellent bondability between the resin film and the copper foil, and removes the copper foil by chemical etching. Regarding the transmission visibility at the exposed resin film portion, it was confirmed that excellent transmission visibility could be ensured regardless of the positional relationship between the resin film and the positioning marker.

  The above-described embodiments and examples are described in order to facilitate understanding of the present invention, and the present invention is not limited to the specific configurations described. For example, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. That is, according to the present invention, a part of the configurations of the embodiments and examples of the present specification can be deleted, replaced with other configurations, and added with other configurations.

10 ... Copper clad laminate,
1 ... copper foil, 2 ... underlying copper plating layer, 3 ... roughened copper plating layer, 4 ... rust prevention layer,
5 ... surface-treated copper foil, 6 ... resin film.

Claims (6)

A copper-clad laminate in which a resin film and a copper foil are directly laminated,
The peel strength between the resin film and the copper foil is 0.5 N / mm or more,
When a part of the copper foil is removed by chemical etching, in the resin film remaining after the chemical etching is removed, the formula “V _t = (T _t −T _d ) × C / 100” (T _t : total light transmission) The transmission visibility V _t defined by the rate (unit:%), T _d : diffuse transmittance (unit:%), C: transparency (unit:%)) is “V _t ≧ 10%” A copper-clad laminate. In the copper-clad laminate according to claim 1,
A roughened copper plating layer is formed on the bonding surface of the copper foil facing the resin film,
The copper clad laminate, wherein the roughened copper plating layer has an average thickness of 0.05 μm or more and 0.3 μm or less. In the copper clad laminate according to claim 2,
The copper foil is a rolled copper foil,
A base copper plating layer is formed between the copper foil and the roughened copper plating layer,
The copper-clad laminate, wherein the base copper plating layer has an average thickness of 0.1 μm to 0.6 μm. In the copper clad laminated board in any one of Claim 1 thru | or 3,
The copper-clad laminate, wherein the transmission visibility V _t is “V _t ≧ 20%”. A flexible printed wiring board in which a part of the copper foil of the copper clad laminate according to any one of claims 1 to 4 is chemically etched to form a circuit wiring,
In the resin film remaining after the chemical etching removal, the formula “V _t = (T _t −T _d ) × C / 100” (T _t : total light transmittance (unit:%), T _d : diffuse transmittance ( unit:%), C: transparency (units:%)) flexible printed wiring board transmitting visibility V _t is characterized in that it is a "V _t ≧ 10%" as defined. In the flexible printed wiring board according to claim 5,
The flexible printed wiring board, wherein the transmission visibility V _t is “V _t ≧ 20%”.

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