JP5282675B2 - Copper foil for printed wiring board and method for producing the same - Google Patents

Description

  The present invention is used as a material for forming wiring patterns and other various conductor patterns in various printed wiring boards such as rigid or flexible printed wiring boards and tape carriers for semiconductor devices, and is used by being bonded to the surface of an insulating substrate. The present invention relates to a set copper foil for printed wiring boards and a method for producing the same.

In recent years, with the miniaturization of various electronic devices, there has been a strong demand for further miniaturization of the wiring pitch in printed wiring boards used therein.
As a manufacturing method of a printed wiring board having so-called copper wiring (various conductor patterns such as wiring patterns formed by patterning copper foil), a subtractive method is generally used as a mainstream process. In the subtractive method, an etching resist pattern is formed on the surface of a copper foil laminated on an insulating substrate, and then used as an etching mask to dissolve copper foil other than a portion that becomes a conductor pattern such as a wiring pattern ( This is a method of forming a conductor pattern (so-called copper pattern) having a desired pattern shape by etching.

  In particular, a copper-clad substrate formed by laminating a copper foil on the surface of an insulating film substrate used in a tape carrier or the like is called CCL (Copper Clad Laminate), but the copper foil used in this CCL is: Surface treatment is often performed in order to improve the adhesion to the insulating film substrate. As the surface treatment, roughening treatment is often used. Roughening treatment is a roughened copper that produces an uneven shape on the raw foil that is rougher than the surface roughness of the original foil by performing electrolytic plating in the copper plating solution at a current density equal to or higher than the limit current density. By forming a plating layer, the surface roughness of the surface of the copper foil bonded to the insulating film substrate is appropriately increased. In this case, the adhesiveness of the copper foil with respect to the insulating film substrate becomes better as the surface roughness of the copper foil is larger.

However, another problem occurs when the surface roughness of the copper foil becomes too large. First, if the surface roughness is too large, when a conductor pattern such as a wiring pattern is formed by an etching process, there is a very high possibility that the dimensional accuracy and adhesion of the completed conductor pattern will be reduced. This is because if the surface roughness of the copper foil is too large, the etching proceeds directly under the etching mask, resulting in an undercut. Second, the surface roughness of the copper foil is IC (Integrated Circuit) on a tape carrier for semiconductor devices such as TAB (Tape Automated Bonding) tape, BGA (Ball Grid Array) tape, COF (Chip On Film) tape, etc. This causes inconvenience in the process of mounting a semiconductor device, an electronic component element, or the like. For example, when bonding and mounting an IC on a COF tape, a method using a CCD camera or the like is generally employed for aligning the gold bumps on the IC chip to be mounted and the leads of the COF tape. At this time, the position of the conductor pattern such as the connection terminal portion on the COF tape must be recognized by a CCD camera or the like by the light transmitted through the insulating film substrate of the COF tape. For this reason, transparency is required for the insulating film substrate of the COF tape. However, if a copper foil having a surface roughness that is too large is used, the surface of the insulating film base material of the so-called non-patterned part that is exposed after the copper foil is removed by etching becomes rough. In this case, light is easily diffusely reflected, transparency is lowered, and alignment is difficult.

Copper foils used for COF tapes and the like include electrolytic copper foils and rolled copper foils, but rolled copper foils are particularly suitable for applications that require high flexibility. However, the surface of the rolled copper foil generally has a depression called an oil pit formed during rolling. When a certain level of surface roughness is required, the surface of the rolled copper foil is subjected to the roughening treatment as described above, and the surface is deliberately roughened to an appropriate roughness. Even in this case, it is desirable that the copper foil before the roughening treatment is smooth. This is because if a relatively large depression such as an oil pit is present on the surface of the copper foil (raw foil), a defect called a crater may occur in the depression. A crater is a phenomenon in which plating deposits abnormally starting from a recess, and the crater is rougher than its surroundings. Cause.
Therefore, a copper foil used for a rigid printed wiring board, a tape carrier for a semiconductor device or the like is first strongly required to have a smooth copper foil surface.
Also, if a copper foil having such a smooth surface can be obtained, abnormal portions such as craters are generated even if a roughening treatment is performed on the surface of the copper foil to further improve adhesion. It becomes possible not to do.

As a measure for making the surface of such a copper foil flat or even smoother, in the case of a rolled copper foil, the copper foil ( A technique of manufacturing a raw foil is proposed (for example, Patent Document 1).
In the case of an electrolytic copper foil, as a method for reducing the surface roughness of the electrolytic copper foil, that is, for smoothing the surface of the electrolytic copper foil as a raw foil, 3-mercapto-1-propanesulfonic acid and / or Alternatively, an electrolytic copper foil is produced by an electrolytic method using a sulfuric acid-based copper electrolytic solution obtained by adding bis (3-sulfopropyl), disulfide, a quaternary ammonium salt polymer having a cyclic structure, and chlorine. A technique has been proposed (for example, Patent Document 2).
In addition, as a method of reducing the surface roughness of the copper foil after being produced as a raw foil, a technique of smoothing the surface of the copper foil by a method such as electrochemical dissolution or plating, followed by a roughening treatment Has been proposed (for example, Patent Documents 3 and 4).
This is not a technology related to copper foil for printed wiring boards, but a technology related to copper alloy plates for semiconductor lead frames. By making the composition of the copper alloy plate appropriate, the roughness of the surface is reduced. A technique has been proposed in which the kurtosis (kurtosis) Rku of the curvature curve is 3.1 or less (for example, Patent Document 5).

JP 2006-281249 A JP 2007-217787 A JP 2004-238647 A JP 2006-155899 A Japanese Patent No. 4197718

However, the technique proposed in Patent Document 1 described above is not a technique for reducing the overall roughness of the surface of the copper foil and smoothing it, but prevents the generation of large depressions such as oil pits. Therefore, it is extremely difficult or impossible to use as a measure for achieving the overall smoothing of the surface of the copper foil.
In addition, the technique proposed in Patent Document 2 described above is for smoothing the surface of the electrolytic copper foil as the original foil, and is not related to the rolled copper foil. It is considered to be used as a measure to achieve smoothing of the surface of the rolled copper foil suitably used for printed wiring boards that require high flexibility such as tape carriers for flexible semiconductor devices and flexible printed wiring boards.・ Not considered.
In the techniques proposed in Patent Documents 3 and 4 above, the surface of the original foil once formed is ground and removed by electrochemical dissolution or mechanical polishing over a predetermined thickness. However, such a grinding treatment has a problem that there are many disadvantages from the viewpoint of material cost and from the viewpoint of complication of the manufacturing process due to the addition of such a grinding process. is there. In this technique, the Rz of the surface of the copper foil is adjusted. However, the surface roughness of the copper foil for the COF tape targeted by the present invention is smoothed more precisely. It is difficult to respond effectively enough.
Moreover, the technique proposed in the above-mentioned Japanese Patent No. 4197718 relates to a copper plate material for a lead frame, and is used for a printed wiring board used by being bonded to the surface of an insulating substrate such as an insulating film substrate. Since the copper foil responds to completely different conditions and requirements, a more precise surface required for the copper foil for printed wiring boards such as the copper foil for the COF tape targeted by the present invention. Whether or not it was possible to obtain the smoothness of was even out of the question.

In this way, the surface of the copper foil for printed wiring boards used to form various conductor patterns in printed wiring boards such as tape carriers for semiconductor devices is smoothed to the extent required in recent years. However, the conventional technique has a problem that it is extremely difficult or impossible.
The present invention has been made in view of such problems, and its purpose is to smooth the surface to such an extent that it can sufficiently cope with various technical requirements required for copper foil for COF tape, for example. It is providing the copper foil for printed wiring boards and its manufacturing method.
In addition, after realizing such surface smoothing, it is possible to perform roughening treatment to a desired roughness to ensure further good adhesion (adhesion) to the insulating substrate. It is providing the copper foil for boards and its manufacturing method.

The copper foil for printed wiring boards of the present invention is firstly a copper foil for printed wiring boards set to be used by being bonded to the surface of an insulating substrate, and the rolled copper foil and the rolled copper foil A flattened copper plating layer provided on the surface, and a kurtosis of a roughness curve defined in JIS B0601-2001 on the surface of the flattened copper plating layer that is bonded to the insulating substrate Rku is set to 3.23 μm or more and 4 μm or less, and the skewness Rsk of the roughness curve defined in JIS B0601-2001 is set to 0 or less.
Moreover, the copper foil for printed wiring boards of the present invention further has a surface roughness defined by JIS B0601-1994 on the surface of the flattened copper plating layer that is bonded to the insulating substrate. the roughened copper plating layer to 0.8μm or 3.0μm or less Rz, it is characterized by comprising further provided.
The method for producing a copper foil for a printed wiring board according to the present invention is a method for producing a copper foil for a printed wiring board, which is set to be used by being attached to the surface of an insulating substrate, with respect to the insulating substrate. The kurtosis Rku of the roughness curve defined by JIS B0601-2001 of the surfaces set to be bonded is set to 3.23 μm or more and 4 μm or less, and the skewness Rsk of the roughness curve defined by JIS B0601-2001 is set. It is characterized by including a step of providing a flattened copper plating layer on the rolled copper foil to be 0 or less.

According to the present invention, a flattened copper plating layer is formed on the surface of the original foil, and JIS B0601- of the surface set to be bonded to the insulating substrate in the copper foil for printed wiring board. The kurtosis Rku of the roughness curve defined in 2001 is set to 4 or less, and JIS
The skewness Rsk of the roughness curve defined in B0601-2001 is set to 0 or less, so that the surface is made to a level that can sufficiently cope with various technical requirements required for copper foil for COF tape, for example. A smoothed copper foil for a printed wiring board can be obtained.
In addition, by realizing such smoothing of the surface, a roughening process is performed on the smoothed surface to a desired roughness without forming a crater (forming a roughened copper plating layer). ) Is possible.

It is a figure which shows the structure of the principal part of the copper foil for printed wiring boards which concerns on embodiment of this invention. It is a figure which shows the structure which formed the roughening copper plating layer further on the flattening copper plating layer of the copper foil for printed wiring boards shown in FIG. It is a figure which shows the flow of the main manufacturing processes in the manufacturing method of the copper foil for printed wiring boards which concerns on embodiment of this invention. It is a figure which shows typically the relationship between the kurtosis Rku of the roughness curve defined by JISB0601-2001 in the surface of the copper foil for printed wiring boards, and the uneven | corrugated state of the surface corresponding to it. It is a figure which shows typically the relationship between the skewness Rsk of the roughness curve defined by JISB0601-2001 in the surface of the copper foil for printed wiring boards, and the uneven | corrugated state of the surface corresponding to it.

  Hereinafter, a copper foil for a printed wiring board and a method for manufacturing the same according to an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the copper foil for a printed wiring board according to the embodiment of the present invention is provided with a flattened copper plating layer 2 on the original foil 1, and the flattened copper plating layer 2. In other words, the roughness of the surface that is set to be bonded to the insulating substrate 4 such as a polyimide resin film base (for example, a polyimide resin film substrate) outside (the other to be bonded) is JIS B0601. The kurtosis Rku of the roughness curve defined by -2001 is 4 or less, and the skewness Rsk of the roughness curve defined by JIS B0601-2001 is 0 or less.

  Further, the surface roughness Rz defined by JIS B0601-1994 of the surface bonded to the insulating substrate 4 is 0.8 μm or less.

  In addition, the relationship between the film thickness T of the flattened copper plating layer 2 and the average depth D of the recessed portions in the original foil 1 satisfies 0.1 ≦ T / D ≦ 2.

  Although not shown, as a more desirable mode, a nickel (Ni) -cobalt (Co) alloy plating layer, zinc (Zn) plating is provided on the surface of the raw foil 1 or the surface of the flattened copper plating layer 2. Any one or both of a layer, a rust prevention treatment layer such as a chromate treatment layer, and a silane coupling layer may be provided.

  The raw foil 1 preferably contains 0.001% by mass or more and 0.01% by mass or less of tin (Sn) and the balance is made of copper (Cu) and a copper alloy that is an inevitable impurity.

  The raw foil 1 can be either a rolled copper foil or an electrolytic copper foil, but the rolled foil generally has more excellent characteristics in terms of surface flatness and bendability. Therefore, it is more desirable to use a rolled copper foil as the raw foil 1.

  Here, in order to make the adhesiveness (adhesiveness) to the other insulating substrate 4 to which the copper foil for printed wiring board is bonded, as shown in FIG. It is a desirable embodiment to further form a roughened copper plating layer 3 having a surface roughness Rz defined by JIS B0601-1994 of more than 0.8 and not more than 3.0 on the plating layer 2. It is.

  The method for manufacturing a copper foil for a printed wiring board according to an embodiment of the present invention is a method for manufacturing a copper foil for a printed wiring board that is set to be used by being attached to the surface of an insulating substrate 4. The roughness curve kurtosis Rku defined by JIS B0601-2001 of the surface set to be bonded to the conductive substrate 4 is set to 4 or less and the roughness curve skewness Rsk defined by JIS B0601-2001 is set. The plating process which provides the planarizing copper plating layer 2 which makes 0 or less on original foil 1 is included. Then, the step of forming the planarized copper plating layer 2 uses a plating solution containing an organic sulfur compound having a mercapto group, a surfactant, or at least one additive of chloride ions. By the electrolytic copper plating process.

  More specifically, first, a rolled copper foil or an electrolytic copper foil is prepared as the raw foil 1. In particular, in the case of a copper foil for a printed wiring board used for applications that require high precision surface flatness and high flexibility, such as COF tape and other semiconductor device tape carriers, as the original foil 1 It is more desirable to use a rolled copper foil.

  And in order to clean the surface of the prepared original foil 1, electrolytic degreasing is performed (step a in FIG. 3). This cleaning process can be performed, for example, by cathodic electrolytic degreasing using an alkaline solution such as sodium hydroxide.

  Subsequently, pickling treatment is performed to neutralize the alkali remaining on the surface of the copper foil and remove the copper oxide film (step b in FIG. 3). This pickling treatment is performed by immersing in an acidic aqueous solution such as sulfuric acid. As the pickling solution, a copper etching solution may be used.

Subsequently, electrolytic treatment using the original foil 1 as a cathode is performed by an acidic copper plating bath mainly composed of copper sulfate and sulfuric acid to form a flattened copper plating layer 2 (step c in FIG. 3). At this time, the copper sulfate, the liquid composition of the sulfuric acid bath, the liquid temperature, and the electrolysis conditions for providing the planarized copper plating layer 2 are not particularly limited, but are preferably selected from the following ranges.
Copper sulfate pentahydrate: 20-300 g / dm ³
Sulfuric acid: 10-200 g / dm ³
Liquid temperature: 15-50 degreeC
Plating current density: 1 to 30 A / dm ² (end of limit current density)
Plating time: 1 to 20 seconds
Further, in the process of forming the flattened copper plating layer 2, it is desirable to add an additive for more surely promoting smoothing. As the additive, a compound having a mercapto group such as 3-mercapto-1-sulfonic acid or bis (3-sulfopropyl) disulfide, a surfactant such as polyethylene glycol or polypropylene glycol, or a chloride ion is used in combination. It is possible. Alternatively, various copper plating additives used in the manufacturing process of the printed wiring board can also be used. As such an additive for copper plating, Top Lucina LS manufactured by Okuno Seiyaku Co., Ltd., Capper Grime CLX manufactured by Meltex, CU-BRITETH-RIII manufactured by Sugawara Eugelite Co., Ltd.
UC or the like can be used.
The plating current density is desirably smaller than the limit current density. Above the critical density, there is a high risk of surface irregularities becoming large. On the other hand, the higher the plating current density, the more the productivity tends to improve. Therefore, it is more desirable that the plating current density be as high as possible within a range smaller than the limit current density under the plating conditions.

  After the planarized copper plating layer 2 is formed, the roughened copper plating layer 3 is formed when higher adhesion to the insulating substrate 4 is required. The step of forming the roughened copper plating layer 3 includes a step of forming a resinous copper plating layer (step d in FIG. 3), a step of changing it to a bump-shaped copper plating layer (step e in FIG. 3), and Is included.

The dendritic copper plating layer uses an acidic copper plating solution mainly composed of copper sulfate or sulfuric acid, and performs electrolytic treatment at a current value exceeding the limit current density of the bath using the copper foil itself to be plated as a cathode. (Step d in FIG. 3).
At this time, the copper sulfate for providing the dendritic copper plating layer, the liquid composition of the sulfuric acid bath, the liquid temperature, and the electrolysis conditions can be selected in a wide range and are not particularly limited, but selected from the following ranges It is desirable that Moreover, when forming a dendritic copper plating layer, it is more desirable to add metal elements other than copper (such as molybdenum, iron, and cobalt), for example.
Copper sulfate pentahydrate: 20-300 g / dm ³
Sulfuric acid: 10-200 g / dm ³
Liquid temperature: 15-50 degreeC
Plating current density: above the limit current density, 20-100 A / dm ²
Plating time: 1-10 seconds

Subsequently, a smooth copper plating layer (covered plating) is formed on the dendritic copper plating layer by a current lower than the limiting current density of the plating solution, and the dendritic copper is changed to so-called bumpy copper. (Step e in FIG. 3).
At this time, the copper sulfate for providing the bumpy copper, the liquid composition of the sulfuric acid bath, the liquid temperature, and the electrolysis conditions can be selected in a wide range and are not particularly limited, but should be selected from the following ranges Is desirable. Moreover, you may make it add the additive used by the formation process of the planarization copper plating layer 2 in the plating solution used at this time.
Copper sulfate pentahydrate: 20-300 g / dm ³
Sulfuric acid: 10-200 g / dm ³
Liquid temperature: 20-50 degreeC
Plating current density: 1 to 20 A / dm ² (less than the limit current density)
Plating time: 1 to 20 seconds
Here, the so-called roughening treatment step (step d and step e in FIG. 3) for forming the roughened copper plating layer 3 is performed when the formation of the roughened copper plating layer 3 is unnecessary. Of course, it can be omitted.

After forming the roughened copper plating layer 3 (or after forming the flattened copper plating layer 2 if the roughened copper plating layer 3 is not formed), a more desirable surface such as sufficient anticorrosion performance, for example In order to obtain characteristics, a so-called post-treatment plating layer (not shown in FIGS. 1 and 2) is provided.
First, a nickel plating layer (or nickel alloy plating layer) is formed to prevent copper diffusion (step f in FIG. 3).
Subsequently, in order to improve heat resistance, a zinc plating layer (or zinc alloy plating layer) is formed (step g in FIG. 3).
Thereafter, a trivalent chromium chemical conversion treatment layer is formed using a trivalent chromium type reactive chromate solution (step h in FIG. 3).
Then, in order to improve the adhesion between the insulating substrate 4 and the resin surface, a silane coupling treatment layer is formed as a chemical conversion treatment film (step i in FIG. 3).
Thus, the principal part of the copper foil for printed wiring boards which concerns on embodiment of this invention is manufactured.

Next, the effect | action in the copper foil for printed wiring boards which concerns on embodiment of this invention, and its manufacturing method is demonstrated.
In the copper foil for printed wiring boards and the method for manufacturing the same according to the embodiment of the present invention, the flattened copper plated layer 2 for smoothing is applied to the surface of the raw foil 1. (But not including the roughened copper plating layer 3), the kurtosis Rku of the roughness curve and the skewness Rsk of the roughness curve on the outermost surface of the entire copper foil are controlled to appropriate values.

Conventionally, Ra, Rz, and the like are used as roughness indices, and these indices have been used according to required characteristics.
However, the inventors of the present invention have intensively conducted various experiments and investigations and studies on the results, and in particular, a copper foil for a printed wiring board used as a material for forming a conductor pattern such as a COF tape and a method for producing the same In Fig. 4, it was confirmed that a desired smooth surface can be obtained by controlling the kurtosis Rku of the roughness curve and the skewness Rsk of the roughness curve. As a specific means, it is possible to accurately control the smoothness of such a surface by forming the flattened copper plating layer 2 on the raw foil 1 by electrolytic plating. It was confirmed.

  Rku is an index indicating the degree of sharpness of the convex part and the concave part in the roughness curve, and Rsk is an index indicating the degree of distribution of the convex part and the concave part with respect to the reference surface in the roughness curve. FIG. 4 shows changes in the surface shape depending on the value of Rku, and FIG. 5 shows changes in the surface shape depending on the value of Rsk.

  The roughness curve kurtosis Rku and the roughness curve skewness Rsk cause the visibility of the CCD in the process of mounting an electronic component element such as an IC on the tape carrier for a semiconductor device and the occurrence of an abnormal part in the roughening process of the copper foil. Here, the main points of the influence will be described.

  In a process of mounting an electronic component element such as an IC chip on a tape carrier for a semiconductor device, a CCD camera is used for aligning a gold bump on the IC chip and a connection terminal portion such as a lead of a COF tape. In order to improve the visibility, it is important to reduce a partial light amount difference in the field of view imaged by the CCD camera. If the difference in the amount of light is too large, there is a high possibility that the dynamic range of the CCD camera will be exceeded, and at this time, it will be difficult to recognize the necessary connection terminals and the like. When considering the roughness of the surface of the resin film substrate (insulating substrate) after removing the copper foil by etching, that is, the roughness of the copper foil surface that is the cause of the unevenness, If there are convex parts or concave parts, the light is irregularly reflected at that part, and it is not possible to obtain a transmitted light amount that allows recognition by the CCD camera at that part. End up. Therefore, it is desirable that the surface of the copper foil for printed wiring boards has few convex portions and concave portions having sharply sharpened tips and bottoms.

The rough shape of such a convex part or a concave part can be represented by a kurtosis Rku of a roughness curve. That is, as schematically shown in FIG. 4A, the smaller the Rku, the fewer the sharpened portions, and the improvement of the light transmittance of the resin film after removing the copper foil by etching can be expected.
More specifically, Rku is preferably 4 or less on the surface of the copper foil for printed wiring board. On the contrary, as schematically shown in FIG. 4 (b), as Rku increases, a convex portion or a concave portion having a sharp tip or bottom is present.

  In addition, it is preferable that the surface of the copper foil for printed wiring board has fewer sharp (pointed) convex portions. That is, if the skewness Rsk of the roughness curve is 0 or less (or negative), as shown in FIG. 5A, the surface has a cross-sectional shape in which slow convex portions are continuously present. However, when the skewness Rsk of the roughness curve is positive, as shown in FIG. 5B, the cross-sectional shape of the surface is a sharp (pointed) convex shape. It will be in the state where a part exists continuously.

  Further, after forming the flattened copper plating layer 2 and smoothing it once, the roughened copper plating layer 3 as shown in FIG. 2 is formed to deliberately roughen the roughness of the surface. Even in such a case, in order to suppress the occurrence of an abnormal portion such as a crater in the formation process of the roughened copper plating layer 3, printed wiring at a stage before the roughened copper plating layer 3 is formed As described above, it is preferable that the surface of the copper foil for plate has fewer sharp convex portions and concave portions. This is because if sharp convex portions exist, the current is concentrated and concentrated on the portions, abnormal plating is deposited, and plating abnormalities such as craters occur. Further, if there is a pointed recess, the plating is not sufficiently performed on that portion. In addition to rough plating, for example, this type of printed wiring board copper foil is patterned to form a conductor pattern, and then a tin (Sn) plating layer or a gold plating layer is formed on the conductor pattern. In the same way as above, if there are sharp protrusions or recesses on the surface of the copper foil for printed wiring boards, plating defects will occur in the vicinity of these parts, and the quality of the printed wiring board There is a high risk of causing a decrease in reliability and reliability. Therefore, Rku is desired to be as small as 4 or less.

  In particular, when there is a sharp convex part on the surface of the copper foil, when the copper foil is subjected to pattern processing by an etching method or the like to form various conductor patterns such as a wiring pattern, the wiring There is a high risk that a short circuit failure or other pattern formation failure will occur. Also from this point, the skewness Rsk of the roughness curve is preferably 0 or less.

For this reason, it is preferable that the kurtosis Rku of the roughness curve is 4 or less and the skewness Rsk of the roughness curve is 0 or less (or negative).
Thus, in order to control Rku and Rsk, it is practically effective to form the flattened copper plating layer 2 on the surface of the original foil 1. That is, by forming the flattened copper plating layer 2 on the surface of the original foil 1, all sharp convex portions, concave portions, and hollow portions such as oil pits existing on the surface of the original foil 1 are filled. An extremely smooth surface state can be obtained.

Here, in order to fill the sharpened depressions with the flattened copper plating layer 2, the flattening is performed by a plating process using a plating solution in which an additive such as an organic sulfur compound, a surfactant, or a chloride ion is added. It is desirable to form the copper plating layer 2.
By using such an additive, it becomes possible to preferentially grow a plating film with respect to the recessed portion on the surface of the original foil 1 by the combined action of these additives and the plating solution. It is possible to completely fill those indentations.

Moreover, the relationship between the film thickness T of the flattened copper plating layer 2 at this time and the average depth D of the dents present on the surface of the original foil 1 before the formation of the flattened copper plating layer 2 is as follows: It is desirable to form the flattened copper plating layer 2 so that 0.1 ≦ T / D ≦ 2.
This is because when T / D <0, there is an extremely high possibility that the depression existing on the surface of the original foil 1 cannot be sufficiently filled, and it is difficult or impossible to make Rku smaller than 4 or less. Because it becomes. Further, in the case of 2 <T / D, due to the phenomenon that the film thickness of the flattened copper plating layer 2 in the hollow portion of the original foil 1 becomes too thick, the Rku of that portion exceeds 4. This is because the possibility of inconveniences such as an increase in size and a decrease in flexibility cannot be ignored becomes extremely high.

As described above, according to the copper foil for a printed wiring board and the manufacturing method thereof according to the present embodiment, the surface defined to be bonded to the insulating substrate 4 is defined in JIS B0601-2001. Since the flattened copper plating layer 2 that makes the kurtosis Rku of the roughness curve to be 4 or less and the skewness Rsk of the roughness curve defined by JIS B0601-2001 to be 0 or less is provided on the raw foil 1 For example, as a typical example, a printed wiring board in which the surface of the conductor pattern is ensured to a sufficient extent to ensure the visibility of the conductor pattern by transmitted light required for a copper foil for a COF tape and to meet various technical requirements. Copper foil can be obtained.
In addition, by realizing such smoothing of the copper foil surface, even when the surface is further subjected to roughening treatment (forming the roughened copper plating layer 3), there is no possibility of occurrence of craters, The roughened copper plating layer 3 can be formed to a desired roughness by the roughening treatment.

  Copper foils for printed wiring boards as described in the above embodiment were produced and used as samples according to examples (Examples 1 to 8). In addition, for comparison with this, copper foils for printed wiring boards were prepared by a configuration and manufacturing method different from those described in the above embodiment, and they were used as samples according to comparative examples (comparative examples). 1-8). And various characteristics about each sample were investigated and compared and examined. Here, in the samples of Examples 1 to 5 and the samples of Comparative Examples 1 to 4, the roughened copper plating layer 3 was not formed on the flattened copper plating layer 2. In addition, the samples of Examples 6 to 8 and the samples of Comparative Examples 5 to 8 were formed by forming the roughened copper plating layer 3 on the flattened copper plating layer 2.

Evaluation about each of those samples was performed by the methods as described in the following (1) to (8).
(1) Measurement of the depth D of the depression on the surface of the raw foil 1
For the measurement of the depth D of the depression on the surface of the raw foil 1, a laser microscope VK-8700 manufactured by Keyence Corporation was used. The observation magnification was set to 500 times, the depths of 50 depressions in the field of view were measured, the average value was obtained, and this was defined as D (μm).
(2) Film thickness T of flattened copper plating layer 2
The film thickness T of the flattened copper plating layer 2 was determined from a photograph obtained by observing a cross section obtained by processing a copper foil using a FIB (Focused Ion Beam) with a scanning electron microscope.
(3) Kurtosis Rku of the roughness curve
In order to evaluate the surface Rku of the samples according to Examples and Comparative Examples before forming the rough copper plating layer 3 or before forming the rough copper plating layer 3, a laser microscope VK-8700 manufactured by Keyence Corporation was used. And the observation magnification was set to 500 times, and Rku according to JIS B0601-2001 was determined as the overall roughness in the field of view.
(4) Kurtosis Rsk of roughness curve
In the Rsk evaluation of the surface in the samples according to Examples and Comparative Examples before forming the roughened copper plating layer 3 or before forming the roughened copper plating layer 3, as in the above (3), Using a laser microscope VK-8700 manufactured by Keyence Corporation, the observation magnification was set to 500 times, and Rsk according to JIS B0601-2001 was determined as the overall roughness in the field of view.
(5) Ten-point average roughness Rz of the roughness curve
The evaluation of the surface roughness Rz before and after the formation of the roughened copper plating layer 3 was evaluated by a ten-point average roughness based on the definition according to JIS B0601-1994. For the measurement, an SE500 surface roughness measuring machine manufactured by Kosaka Laboratory Ltd. was used. Rz was a scanning distance of 4 mm, and a cutoff was 0.8 mm.
(6) Light transmittance of resin film (insulating substrate 4)
After attaching the copper foil for printed wiring board of each sample to the insulating substrate 4 and then removing it by etching, the portion of the insulating substrate 4 that is exposed is checked whether the light transmission is good or not by the CCD camera in that portion. It was evaluated by the degree of ease of recognition.
That is, after applying polyimide resin to the copper foil for printed wiring board of each sample by casting method to form the insulating substrate 4, a part of the copper foil for printed wiring board is removed by etching to form a predetermined wiring pattern did. Then, the sample is photographed with a CCD camera from the surface opposite to the surface on which the wiring pattern is formed (so-called back surface), and the captured wiring pattern and the image of the LSI arranged in the vicinity thereof are more than predetermined. Based on whether or not it can be easily recognized, the light transmittance of the resin film (insulating substrate 4) was evaluated in three stages of ◎, ○, and Δ. In Table 1, the symbol ◎ indicates that it can be easily recognized, the symbol ○ indicates that it can be recognized with a predetermined clarity, and △ indicates that it is difficult to recognize. Show.
(7) Copper residue after etching
The copper residue after etching was confirmed by visual observation with an optical microscope. That is, after removing the copper foil bonded to the resin surface of the insulating substrate 4 to the thickness equivalent by etching, it was confirmed whether or not there was any copper residue on the resin surface of the insulating substrate 4 in that portion. .
(8) Crater density after formation of roughened copper plating layer
The crater density was evaluated for the samples formed with the roughened copper plating layer 3 (samples listed in Table 2). For evaluation of the crater density, an optical microscope was used to count the number of craters in the optical microscope photograph obtained by photographing a 3 × 3 mm area, to obtain the number density of craters per unit area, and to calculate the crater abnormality occurrence. Used as an index of evaluation.

  Table 1 shows the specifications and results of the samples (Examples 1 to 5 and Comparative Examples 1 to 4) in which the roughened copper plating layer 3 is not formed. Moreover, the specification and result about the sample (Examples 6-8 and Comparative Examples 5-8) which form the roughening copper plating layer 3 are put together in Table 2, and are shown.

Example 1
As the raw foil 1, a rolled copper foil having a thickness of 11 μm and containing 0.01% by mass of tin (Sn) was used. In order to clean the surface of the rolled copper foil, electrolytic degreasing and pickling treatment were performed. The electrolytic degreasing treatment was performed in an aqueous solution containing 40 g / dm ³ sodium hydroxide and 20 g / dm ³ sodium carbonate at a temperature of 40 ° C. and a current density of 5 A / dm ² for 10 seconds. The pickling treatment was performed for 5 seconds while keeping the liquid temperature at 25 ° C. in an aqueous solution containing 150 g / dm ³ of sulfuric acid. Then, it washed with running water. Here, the raw foil 1 is not limited, but in the case of a copper foil used for a printed wiring board that requires particularly high flexibility and a printed wiring board that requires ultra-fine wiring. A rolled copper foil is preferred. In that case, it is also desirable to use a copper alloy in which tin (Sn), silver (Ag), zirconium (Zr) or the like is mixed with copper (Cu).
Subsequently, a flattened copper plating layer 2 having an average thickness of 0.07 μm was formed on the surface of the raw foil 1 by electroplating. Copper plating solution used in this step, 185 g / dm ³ of copper sulfate pentahydrate, 80 g / dm ³ sulfuric acid, bis organic sulfur compound (3-sulfopropyl) disulfide 50 mg / dm ^3, surfactant polyethylene glycol 3000 200mg / dm ^3, was an aqueous solution containing chloride ion 50 mg / dm ³ as. The plating conditions were a plating solution temperature of 35 ° C. and a plating current density of 6 A / dm ³ for 3 seconds.
Subsequently, using a plating solution adjusted to nickel sulfate hexahydrate 300 g / dm ³ , nickel chloride 45 g / dm ³ , boric acid 50 g / dm ³ , and temperature 50 ° C., electrolytic treatment was performed at a current density of 2 A / dm ² for 5 seconds. Then, a nickel plating layer was formed at 10 μg / cm ² .
Subsequently, after washing with water, electrolytic treatment was performed at a current density of 1.5 A / dm ² for 4 seconds using a plating solution adjusted to zinc sulfate 90 g / dm ³ , sodium sulfate 70 g / dm ³ , and a temperature of 30 ° C., and then galvanized. A layer was formed at 1.0 μg / cm ² . Furthermore, trivalent chromium conversion treatment is performed,
A chromate film was formed at 1.1 μg / cm ² .
Then, after washing with water and immersing in a silane coupling solution of 5-aminopropyltrimethoxysilane 5% at room temperature for 5 seconds, it was immediately dried at a temperature of 120 ° C. to form a silane coupling treatment layer.

(Example 2)
In Example 2, a flattened copper plating layer 2 having an average thickness of 0.2 μm was formed by electroplating. The rest was the same as in Example 1. The plating conditions for forming the flattened copper plating layer ² were 9 seconds at a plating current density of 6 A / dm2.

(Example 3)
In Example 3, a flattened copper plating layer 2 having an average thickness of 0.8 μm was formed by electroplating. The rest was the same as in Example 1. The plating conditions for forming the planarized copper plating layer ² were 9 seconds at a plating current density of 24 A / dm ² .

Example 4
In Example 4, a flattened copper plating layer 2 having an average thickness of 1.4 μm was formed by electroplating. The rest was the same as in Example 1. The plating conditions for forming the flattened copper plating layer ² were 16 seconds at a plating current density of 24 A / dm ² .

(Example 5)
In Example 5, a rolled copper foil having a thickness of 8 μm containing 0.001% by mass of tin (Sn) was used as the raw foil 1. Further, a flattened copper plating layer 2 having an average thickness of 0.9 μm was formed by electrolytic plating. The rest was the same as in Example 1.

(Comparative Example 1)
As a sample of Comparative Example 1, a sample similar to Example 1 was produced except that the planarized copper plating layer 2 was not formed.

(Comparative Examples 2 and 3)
As Comparative Examples 2 and 3, the plating solution used for forming the flattened copper plating layer 2 does not contain additives such as bis (3-sulfopropyl) disulfide, polyethylene glycol, and chloride ions. Except for the above, samples were prepared in the same settings as in Examples 2 and 3.

(Comparative Example 4)
As Comparative Example 4, a sample was prepared with the same settings as Comparative Example 2 except that the process conditions in the plating step when forming the planarized copper plating layer 2 were 3 seconds at a plating current density of 30 A / dm ^2. did.

  As summarized in Table 1, the results of the samples according to Examples 1-5 are clearly compared with the inferior results of the samples according to Comparative Examples 1-4. The flattened copper plating layer 2 is formed on the surface, the kurtosis Rku of the surface roughness curve is 4 or less, the skewness Rsk of the surface roughness curve is 0 or less, and the value of T / D is 0. By controlling within the range of 1 ≦ T / D ≦ 2, the light transmittance of the portion of the insulating substrate 4 (resin film) after the removal of the copper foil by etching, and further the conductor pattern by the transmitted light in that portion It has been confirmed that good recognizability such as can be secured. At the same time, it was confirmed that the generation of copper residue after etching can be suppressed or eliminated. Further, in particular, by adding an additive such as bis (3-sulfopropyl) disulfide, polyethylene glycol, or chloride ion to the plating solution used when forming the flattened copper plating layer 2, it is further ensured. In addition, it was confirmed that smoothing of the surface can be realized.

  Further, in addition to the above setting, by setting the surface Rz to 0.8 μm or less, the smoothness of the surface can be made more surely favorable. Results (Rz = 1.0, that is, when Rz> 0.8, the permeability of the resin film is ◯), and other results of Examples 1 to 4 (when Rz ≦ 0.8, the permeability of the resin film) Was confirmed by comparison with ◎).

(Example 6)
In the sample of Example 6, after forming a flattened copper plating layer 2 on the original foil 1 using a rolled copper foil having a thickness of 11 μm containing 0.004% by mass of tin (Sn), A copper chloride plating layer 3 and a covering plating layer (not shown) were formed. Other than that, the settings were the same as in Example 1.
In forming the roughened copper plating layer 3, first, the flattened copper plating layer 2 was formed on the surface of the original foil 1, washed with water, copper sulfate pentahydrate 75 g / dm ³ , sulfuric acid 150 g / dm ³ , Dendritic copper plating layer by performing electrolytic treatment at a current density of 40 A / dm ² for 3 seconds with a plating bath adjusted to iron sulfate heptahydrate 20 g / dm ³ , sodium molybdate 1 g / dm ³ , and temperature 30 ° C. Formed. Subsequently, after washing with water, copper sulfate pentahydrate 185 g / dm ³ sulfuric acid 80 g / dm ^3, by using the plating solution was adjusted to a temperature 35 ° C., at a current density of 10A / dm ² for 10 seconds electrolytic treatment, dendritic The roughened copper plating layer 3 was formed by changing the copper plating layer into a bumpy copper plating layer.

(Example 7)
In the sample of Example 7, the setting was the same as that of Example 6 except that the plating time for forming the roughened copper plating layer 3 was 5 seconds.

(Example 8)
In the sample of Example 8, when the rough copper plating layer 3 is formed, the plating time of the rough copper plating is 8 seconds, and the plating time of the covering copper plating layer is 20 seconds. The same setting was used.

(Comparative Examples 5-7)
In the samples of Comparative Examples 5 to 7, the plating solution for forming the flattened copper plating layer 2 was a plating solution that did not contain additives such as bis (3-sulfopropyl) disulfide, polyethylene glycol, and chloride ions. Except for this, the settings were the same as in Examples 6-8.

(Comparative Example 8)
In the sample of Comparative Example 8, the plating conditions for forming the flattened copper plating layer 2 were the same as those of Comparative Example 6, except that the plating current density was 30 A / dm ² for 3 seconds.

As summarized in Table 2, the results of the samples according to Examples 6-8 are clearly compared with the inferior results of the samples according to Comparative Examples 5-8, as shown in Table 2. The planarized copper plating layer 2 is formed on the surface, and the kurtosis Rku of the surface roughness curve is set to 4 or less, and the skewness Rsk of the surface roughness curve is set to 0 or less, whereby the insulating substrate 4 ( It was confirmed that it was possible to ensure the light transmissivity of the portion of the resin film) after the etching removal of the copper foil, and thus good recognition of the conductor pattern or the like by the transmitted light in that portion. At the same time, it was confirmed that the generation of copper residue after etching can be suppressed or eliminated. Further, in particular, by adding an additive such as bis (3-sulfopropyl) disulfide, polyethylene glycol, or chloride ion to the plating solution used when forming the flattened copper plating layer 2, it is further ensured. In addition, it was confirmed that smoothing of the surface can be realized.

  Further, when the roughened copper plating layer 3 is formed on the surface of the copper foil which is formed to be very smooth by forming the extremely smooth flattened copper plating layer 2 as described above, the roughened copper plating layer. 3 can prevent or eliminate the occurrence of defects such as craters, and can reliably obtain a rough surface having a desired roughness that can improve the adhesion to the insulating substrate 4. It was confirmed that

  The present invention is particularly suitable for a copper foil for a printed wiring board for a COF tape and a method for producing the same, but the application of the present invention is of course not limited thereto. In addition, for example, flexible printed wiring boards for mobile phones and in-vehicle use have become increasingly finer in recent years, and accurate positioning based on transmitted light must be performed when mounting an IC chip or the like. It can also be suitably used as a copper foil used for a printed wiring board that does not become necessary. Needless to say, the present invention can be applied to various other uses.

1 Raw foil 2 Flattened copper plating layer 3 Roughened copper plating layer 4 Insulating substrate

Claims (8)

A copper foil for a printed wiring board set to be used by being attached to the surface of an insulating substrate,
Rolled copper foil,
A planarized copper plating layer provided on the rolled copper foil,
The roughness curve kurtosis Rku defined in JIS B0601-2001 on the surface of the flattened copper plating layer bonded to the insulating substrate is set to 3.23 μm or more and 4 μm or less, and JIS B0601-2001. A copper foil for a printed wiring board, wherein the skewness Rsk of the roughness curve defined in (1) is 0 or less. In the copper foil for printed wiring boards according to claim 1 ,
A surface roughness Rz defined by JIS B0601-1994 of the surface of the flattened copper plating layer that is bonded to the insulating substrate is 0.8 μm or less. Copper foil. In the copper foil for printed wiring boards according to claim 1 or 2 ,
On the surface of the pre-Symbol planarizing copper plating layer, a copper foil for printed wiring board characterized by comprising providing a rustproofing layer and / or a silane coupling layer. In the copper foil for printed wiring boards according to any one of claims 1 to 3 ,
The relation between the film thickness T of the flattened copper plating layer and the average depth D of the dents in the rolled copper foil is 0.1 ≦ T / D ≦ 2, . In the copper foil for printed wiring boards according to any one of claims 1 to 4 ,
The rolled copper foil contains tin (Sn) in an amount of 0.001% by mass to 0.01% by mass, and the balance is made of copper (Cu) and a copper alloy that is an inevitable impurity. Copper foil for plates. Te copper foil for printed wiring boards smell according to one term any one of claims 1 to 5,
Crude that on the side of the surface to be glued to the insulating substrate before Symbol planarizing copper plating layer, the surface roughness Rz defined in JIS B0601-1994 and 0.8μm or 3.0 [mu] m or less A copper foil for a printed wiring board, further comprising a copper chloride plating layer. A method for producing a copper foil for a printed wiring board set to be used by being bonded to the surface of an insulating substrate,
The kurtosis Rku of the roughness curve defined by JIS B0601-2001 of the surface set to be bonded to the insulating substrate is set to 3.23 μm or more and 4 μm or less and defined by JIS B0601-2001. The manufacturing method of the copper foil for printed wiring boards characterized by including the process of providing the planarization copper plating layer which makes skewness Rsk of a roughness curve 0 or less on rolled copper foil . In the manufacturing method of the copper foil for printed wiring boards of Claim 7,
The planarized copper plating layer is formed by an electrolytic copper plating process using a plating solution containing an organic sulfur compound having a mercapto group, a surfactant, or at least one additive of chloride ions. A method for producing a copper foil for a printed wiring board.

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