Metal foil electrolytic manufacturing apparatus

Abstract

An object of the present invention is to provide an apparatus for electrolytically manufacturing a metal foil which can precisely control the uniformity of the foil thickness in a transverse direction of the metal foil, when the metal foil is continuously manufactured through the electroprecipitation by the use of a drum-like rotating cathode. The present invention is an apparatus for electrolytically manufacturing a metal foil comprising a drum-like rotating cathode which electrodeposits the metal foil thereon, an anode whose surface is oppositely disposed along a contour of a peripheral surface of the above described rotating cathode, and solution-supplying means having an electrolyte-supplying inlet for supplying an electrolyte in between the rotating cathode and the anode from an underside of the rotating cathode, the metal being electrodeposited onto the peripheral surface of the rotating cathode through an electrolytic reaction while supplying the electrolyte from the solution-supplying means, then the metal foil electrodeposited being continuously released from the rotating cathode, in which the solution-supplying means has a plate-like damper body extending in a transverse direction of the rotating cathode above the electrolyte-supplying inlet.

Description

TECHNICAL FIELD

[0001] The present invention relates to an apparatus for electrolytically manufacturing a metal foil, and more specifically, to a manufacturing technique of a metal foil intended for uniform thickness in a transverse direction of the metal foil.

BACKGROUND ART

[0002] In recent years, a metal foil such as an electrodeposited copper foil which is a representative material for a printed wiring board, for example, has been extensively manufactured for various purposes. As a method for manufacturing such a metal foil, the method which utilizes an electrolytic reaction has been known.

[0003] As an apparatus for electrolytically manufacturing a metal foil which utilizes this electrolytic reaction, an apparatus which employs a drum-like rotating cathode as shown in FIG. 4 is used for continuously manufacturing a metal foil. An apparatus 1 for electrolytically manufacturing a metal foil as shown in FIG. 4 comprises a drum-like rotating cathode 2 which electrodeposits the metal foil thereon, an anode 3 whose surface is oppositely disposed along a contour of a peripheral surface of the rotating cathode 2, and solution-supplying means 5 having an electrolyte-supplying inlet 4 for supplying an electrolyte in between the rotating cathode 2 and the anode 3 from an underside of the rotating cathode 2, in which the metal is electrodeposited onto the peripheral surface of the rotating cathode 2 through the electrolytic reaction while supplying the electrolyte from this solution-supplying means 5, then the metal foil 6 electrodeposited is continuously released from the rotating cathode 2.

[0004] There are many characteristic requirements of the metal foil which can be obtained by such an electrolytically manufacturing apparatus, such as strength, surface properties, and uniform thickness to cope with individual applications, so that the metal foil which satisfies these requirements has to be manufactured. Particularly, in case of a copper foil used as a material for a printed wiring board, uniformity of the foil thickness is very important as the quality of the metal foil in addition to a strength characteristic and a surface property.

[0005] In most cases, the metal foil which can be obtained by this apparatus for electrolytically manufacturing a metal foil is manufactured by continuously peeling the metal electroprecipitated on the surface of the rotating cathode and then making the long lengths of metal foil into a roll-shape. In such a case, a thickness in a longitudinal direction of the metal foil can be uniformly controlled with relative ease by controlling the rotating speed of the rotating cathode, but a thickness in a transverse direction of the metal foil cannot be easily controlled.

[0006] Conventionally, in order to improve the thickness uniformity in the transverse direction of the metal foil obtainable by this apparatus for electrolytically manufacturing a metal foil, measures in which the anode facing to the rotating cathode is divided in its transverse direction and an electrolytic current supply in the transverse direction is controlled in the transverse direction has been proposed.

[0007] However, such an improvement of the method for current supply is far from satisfactory although the thickness uniformity in the transverse direction of the metal foil can be controlled to some extent. In addition, to allow different electrolytic currents to be supplied to the divided anodes, respectively, a structure of the apparatus for electrolytically manufacturing a metal foil becomes complicated, so that it becomes undesirable for designing such an apparatus.

[0008] Further, quality requirements for metal foils in these days have become stringent with the advance of technology for each purpose. In particular, there has been a tendency to highly demand a metal foil having a smaller thickness. In case of an electrodeposited copper foil used as a material for a printed wiring board, foil thicknesses of 35 Mm and 18 Mm have been conventionally the mainstream, but recently the demands for ultra-thin copper foils of 12 &mgr;m and 9 &mgr;m thickness have been intensified. If such an ultra-thin copper foil is manufactured by the above described apparatus for electrolytically manufacturing a metal foil, wrinkles are caused on a surface of the foil when the metal foil is released from the rotating cathode to be wound up unless the thickness uniformity in the transverse direction of the metal foil is precisely maintained, so that the utilization of this metal foil as a final product becomes difficult. In measures for achieving the uniformity of the thickness in the transverse direction of the metal foil which have been conventionally proposed, it is difficult to precisely control the uniformity of the thickness in the transverse direction that is required to manufacture such an ultra-thin metal foil. Thus, in order to supply a metal foil having a smaller thickness such as the ultra-thin copper foil to market with stability, it can be said that it is essential to establish a technique for electrolytically manufacturing a metal foil which allows for achieving the uniform thickness in the transverse direction of the metal foil more precisely than before.

DISCLOSURE OF THE INVENTION

[0009] The present invention has been achieved in view of the above described circumstances, and an object of the present invention is to provide an apparatus for electrolytically manufacturing a metal foil which can uniformly control a foil thickness in a transverse direction of the metal foil precisely when the metal foil is continuously manufactured through electroprecipitation by the use of a drum-like rotating cathode.

[0010] In order to solve the above described problems, the present inventors have conducted a close study on the apparatus for electrolytically manufacturing a metal foil which uses the drum-like rotating cathode. As a consequence of this study, the present inventors have noticed that a liquid flowing state of a electrolyte which is supplied in between the rotating cathode and the anode has a large influence on the thickness uniformity in the transverse direction of the metal foil and have conceived the present invention.

[0011] The present invention is an apparatus for electrolytically manufacturing a metal foil comprising a drum-like rotating cathode which electrodeposits the metal foil thereon, an anode whose surface is oppositely disposed along a contour of a peripheral surface of the rotating cathode, and solution-supplying means having an electrolyte-supplying inlet for supplying an electrolyte in between the rotating cathode and the anode from an underside of the rotating cathode, the metal being electrodeposited onto the peripheral surface of the rotating cathode through an electrolytic reaction while the electrolyte being supplied from this solution-supplying means, and then the metal foil electrodeposited being continuously peeled from the rotating cathode, in which the solution-supplying means is provided with a plate-like damper body extending in the transverse direction of the rotating cathode above the electrolyte-supplying inlet.

[0012] When the electrolyte is supplied in between the drum-like rotating cathode which electrodeposits the metal foil thereon and the anode whose surface is oppositely disposed along the contour of the peripheral surface of the rotating cathode from the underside of the rotating cathode, as indicated by dashed lines with arrow heads in FIG. 4, the supplied electrolyte forms a certain liquid flow in which the electrolyte runs into the surface of the rotating cathode at a position facing to the electrolyte -supplying inlet and diverges into two streams going upward along the contour of the peripheral surface of the rotating cathode.

[0013] In the proximity of the surface of the rotating cathode at a position which faces to this electrolyte-supplying inlet, the electrolyte running into the surface of the rotating cathode easily causes a vortex flow state, and the more complicated liquid flow is produced compared with a liquid flow state in which the electrolyte goes upward along the contour of the peripheral surface of the rotating cathode. In addition, since new electrolyte is continuously supplied to the surface of the rotating cathode at the position which faces to this electrolyte-supplying inlet, metal ions available for the electroprecipitation are sufficiently supplied in this situation. Considering this situation, a supplying amount of the electrolyte in the transverse direction of the surface of the rotating cathode at a position which faces to the electrolyte-supplying inlet may tend to become non-uniform compared with other regions on the surface of this rotating cathode because the liquid flow at the above described position is more complicated. Further, metal ions available for the electroprecipitation are sufficiently supplied to the surface of the rotating cathode into which the electrolyte runs, so that the present inventors have assumed that electroprecipitation which causes non-uniformity of the thickness in the transverse direction of the metal foil is conducted.

[0014] Therefore, the present inventors have provided a plate-like damper body extending in the transverse direction of the rotating cathode above the electrolyte-supplying inlet, in order to dissolve the complicated liquid flow state which is produced on the surface of the rotating cathode at the position facing to this electrolyte-supplying inlet. As a result of providing this plate-like damper body in order to dissolve the complicated liquid flow state which is produced in the proximity of the surface of the rotating cathode at the position facing to the electrolyte-supplying inlet, the present inventors have found that the uniformity of the thickness in the transverse direction can be greatly improved as previously assumed. In addition, the present inventors have also found that providing this plate-like damper body has the effect of reducing the abnormal deposition which occurs on the surface of the metal foil.

[0015] The plate-like damper body of the apparatus for electrolytically manufacturing a metal foil according to the present invention has no restrictions on its shape or its arrangement, except that a certain liquid flow state in which the electrolyte supplied from the electrolyte-supplying inlet toward the surface of the rotating cathode directly runs into the surface of the rotating cathode can be dissolved. Briefly speaking, the plate-like damper body having any shape or any arrangement can be used as long as the plate-like damper body provided in the transverse direction of the rotating cathode interferes with the flowing direction of the electrolyte which is supplied from the electrolyte-supplying inlet toward the surface of the rotating cathode.

[0016] In addition, the plate-like damper body of the apparatus for electrolytically manufacturing a metal foil according to the present invention is desirably provided with a projection for divergence extending in the longitudinal direction of the plate at a center of the plate-width. Providing the plate-like damper above the electrolyte-supplying inlet, the supplied electrolyte directly runs into the plate-like damper, so that the complicated liquid flow such as a vortex flow can be easily formed at this position. Therefore, providing the projection for divergence in the longitudinal direction of the plate at the center of the plate-width of this plate-like damper, the electrolyte directly running into the plate-like damper is diverged into two directions by the projection for divergence, so that the electrolyte smoothly goes upward along the contour of the peripheral surface of the rotating cathode. Providing this projection for divergence for the plate-like damper body ensures that the thickness uniformity in the transverse direction of the metal foil can be improved.

[0017] Further, the apparatus for electrolytically manufacturing a metal foil according to the present invention preferably has an electrolyte-supplying inlet being divided into a plurality of sections in the transverse direction of the rotating cathode and being able to regulate the flow rate of the electrolyte supplied from the each section of the divided electrolyte-supplying inlet. Such construction facilitates precisely controlling of the uniformity of the thickness in the transverse direction of the metal foil. The apparatus for electrolytically manufacturing a metal foil according to the present invention frequently uses a relatively large rotating cathode or anode etc. in order to achieve high production efficiency, but in such an large apparatus for electrolytically manufacturing a metal foil, members constituting the rotating cathode or anode of the apparatus cannot be uniformly formed. Therefore, the result of the electroprecipitation tends to vary depending on the apparatus as the apparatus becomes larger. Thus, the variations of the thickness in the transverse direction of the manufactured metal foil also tends to differ from apparatus to apparatus. Even if such variations in the electroprecipitation may result between the apparatuses, regulating the flow rate of the electrolyte supplied from each section of the divided electrolyte-supplying inlet to correspond to the variations of the thickness in the transverse direction of the metal foil from each apparatus can easily provide the precise control of the thickness uniformity in the transverse direction of the metal foil in cooperation with the effect of the plate-like damper body according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG. 1 is a partly enlarged perspective view of an apparatus for electrolytically manufacturing a metal foil;

[0019] FIG. 2 is a partly enlarged cross sectional view of an apparatus for electrolytically manufacturing a metal foil provided with a plate-like damper body;

[0020] FIG. 3 is a partly enlarged perspective view of the plate-like damper body;

[0021] FIG. 4 is a cross sectional view schematically showing the apparatus for electrolytically manufacturing a metal foil;

[0022] FIG. 5 is a graph showing a thickness distribution in a transverse direction when the plate-like damper body is disposed; and

[0023] FIG. 6 is a graph showing a thickness distribution in a transverse direction when the plate-like damper body is not disposed.

BEST MODE FOR CARRYING OUT THE INVENTION

[0024] The preferable embodiment of the present invention will now be described below.

[0025] An apparatus for electrolytically manufacturing a metal foil of the present embodiment has basically the same structure as that of an apparatus conventionally used, and its cross section is schematically shown in FIG. 4. An apparatus 1 for electrolytically manufacturing a metal foil comprises a drum-like rotating cathode 2 which electrodeposits the metal foil thereon and an anode 3 whose surface is oppositely disposed along a contour of a peripheral surface of the rotating cathode 2. The rotating cathode 2 and the anode 3 are connected to a feeder system which is not shown. And the rotating cathode 2 is disposed such that almost one-half its volume is immersed in an electrolyte. The anode 3 is divided into two sections, and electrolyte supplying means 5 having an electrolyte -supplying inlet 4 for supplying the electrolyte in between the two sections of the anode 3 from an underside of the rotating cathode 2 is provided between the two sections of the anode 3. Supplying the electrolyte from this electrolyte-supplying inlet 4 toward the rotating cathode 2, the electrolyte flows upward along the contour of the peripheral surface of the rotating cathode 2 and overflows into an electrolytic bath 7 as indicated by dashed lines with arrow heads in FIG. 4. A metal foil 6 electroprecipitated onto the peripheral surface of the rotating cathode 2 is released from the rotating cathode 2 and is wound by a wind-up roll 9 via a guide roll 8.

[0026] FIG. 1 is an enlarged perspective view of a portion which is enclosed with a circle A shown in FIG. 4. The electrolytic supplying inlet 4 of the electrolytic supplying means 5 is divided into a plurality of sections in a transverse direction of the rotating cathode 2, each of the divided electrolyte-supplying inlets 4′, 4′, . . . being provided with flow rate regulating means, which is not shown in this figure, for regulating the flow rate of the electrolyte to be supplied although.

[0027] FIG. 2 is an enlarged cross sectional view of a plate-like damper body which is disposed above the electrolyte-supplying inlet 4 of the apparatus 1 for electrolytically manufacturing the metal foil according to the present invention. And FIG. 3 is a perspective view of the plate-like damper body which is partly enlarged. The plate-like damper body 10 has almost the same length as a width of the rotating cathode 2 and has a width which is slightly longer than a width of the electrolytic supplying inlet 4, and a projection 11 for divergence is formed in a longitudinal direction of the plate at a center of the plate-width. And at an underside of the plate-like damper body 10, that is, at a side facing to the electrolytic supplying inlet 4, partition walls 12 are respectively provided corresponding to the sections 4′ of the divided electrolyte-supplying inlet 4. This partition walls 12 are provided on fixing plates 13 so that the walls are in their vertical positions. Therefore, at the lower part of the plate-like damper body 10, liquid discharging outlets 14 are respectively formed corresponding to the sections 4′, 4′, . . . of the divided electrolyte-supplying inlet 4.

[0028] In this arrangement in which the plate-like damper body 10 shown in FIG. 2 and FIG. 3 is disposed above the electrolyte-supplying inlet 4, the electrolyte supplied from the electrolyte-supplying inlet 4 runs up against the plate-like damper body 10 as indicated by arrows in FIG. 2, and the flowing direction of the electrolyte diverges into two directions by the projection 11 for divergence to form a certain liquid flowing state in which the electrolyte flows upward along the contour of the peripheral surface of the rotating cathode 2.

[0029] Next, a copper foil is manufactured as the metal foil by the use of the apparatus for electrolytically manufacturing a metal foil according to the present invention, the results of studying thickness distribution in the transverse direction and surface properties of the manufactured copper foil will be described.

[0030] When a copper foil was manufactured as the metal foil, an apparatus for electrolytically manufacturing the copper foil comprising a drum-like rotating cathode (3 m in diameter and 1.35 m in width) whose peripheral surface is made of Ti and an insoluble anode which is referred to as DSA in which a gap between the rotating cathode and the insoluble anode becomes about 20 mm was used. And a plate-like damper body provided with a projection for divergence was made of a Ti material (partition plates and fixing plates are also formed by the Ti material) and disposed above an electrolyte-supplying inlet at a central position between the rotating cathode and the anode. This placement of the plate-like damper body was performed with insulating materials interposed between the anode and the fixing plate in order to prevent the electrolytic current from passing through the plate-like damper body. As the electrolyte, a copper sulfate solution was used.

[0031] Using such an apparatus for electrolytically manufacturing the copper foil which is provided with the plate-like damper foil, a copper foil was manufactured through an electrolytic treatment, and this copper foil was subjected to the comparison study for comparing its thickness distribution in the transverse direction of the copper foil and its surface property with those of a copper foil which was manufactured by an apparatus for electrolytically manufacturing the copper foil without the plate-like damper body.

[0032] Firstly, the result of measuring the thickness distribution in the transverse direction of the copper foil will be described. This thickness distribution measurement in the transverse direction was performed on the copper foil which was subjected to the electrolytic treatment with the electrolyte supplied thereto under the condition that the rotating cathode was in a stationary state. As a sample which was subjected to the measurement of the thickness distribution in its transverse direction, a copper foil, which was obtained by performing an electrolytic treatment such that a copper foil corresponding to a thickness of 70 &mgr;m was formed and by peeling the electroprecipitated copper foil on a half of the peripheral surface of the rotating cathode after the electrolytic treatment, was used. From this sample obtained through the stationary electrolysis, a total of four web-like specimens (A to D) each of which had a length of 150 mm and a width of 1350 mm (a width of the rotating cathode) were cut out in a circumference direction such that two specimens each were respectively taken from a forward region and a backward region of a position in which the rotating cathode and the surface of the anode were facing each other.

[0033] Each of the cut out web-like specimens was further divided into smaller strips each of which had a 10 mm of width and a 100 mm of length. This division of the web-like specimens gave 84 strips which were formed by dividing the specimens in the transverse direction. A weight thickness (g/m2) was calculated through measuring a weight of each strip and this calculated value was regarded as a thickness of the copper foil.

[0034] As for the four web-like specimens (A to D) which were cut out after the stationary electrolysis, the weight of each strip obtained by dividing the web-like specimens into 84 strips was measured. A plot of the thickness corresponding to the transverse direction was shown in FIG. 5 and FIG. 6.

[0035] FIG. 5 shows an apparatus provided with the plate-like damper body, and FIG. 6 shows an apparatus in which the plate-like damper body was not disposed. In these web-like specimens A to D, a region between the strip specimens B and C corresponds to a position in which the surface of the rotating cathode faces to the electrolyte-supplying inlet. In FIG. 5 and FIG. 6, the maximum value of weight thickness was specified among 84 strips obtained by dividing the web-like specimens, a difference between the weight thickness value of each strip and the maximum weight thickness value was calculated, and each value of the weight thickness difference was divided by the maximum value of the weight thickness in order to obtain a value of thickness ratio (%), and then each of the obtained value was plotted.

[0036] In case of an apparatus in which the plate-like damper body was not disposed, the web-like specimens A to D taken altogether exhibited a weight thickness difference of 14.2% at the maximum and exhibited a weight thickness difference of 6.5% on an average. As can be seen from FIG. 6, the apparatus without the plate-like damper body produces variations of the weight thickness in the transverse direction of each of the web-like specimens A to D, a standard deviation at that time was 3.05 (a value calculated from all data on A to D).

[0037] On the other hand, in case of disposing the plate-like damper body, a difference of weight thickness was decreased to 10.8% at the maximum and a difference of weight thickness on average was 3.4%. As can be seen from FIG. 5, the apparatus provided with the plate-like damper body had an extremely uniform weight thickness in the transverse direction of each of the web-like specimens A to D, and it was ensured that the standard deviation was 1.89 (a value calculated from all data on A to D). The study on the thickness distribution in the transverse direction was performed on the divided strips having a size of 10 mm in width and a 100 mm in length. However, when the foil was divided to such a precise extent in the transverse direction of the copper foil, the apparatus according to the present invention which could precisely control the variation in weight thickness with a standard deviation of 1.89 is completely different from the conventional apparatus for manufacturing the copper foil which could hardly achieve such a standard deviation.

[0038] Next, the result of a study performed on a surface property of the copper foil will be described. This comparison study on the surface property was conducted by manufacturing 10 m of a copper foil having a thickness of 35 &mgr;m and observing an unusual deposition on a rough surface of the obtained copper foil (a matte surface; a surface corresponding to a surface after the electroprecipitation was completed). This unusual deposition means a certain region in which the deposits are extraordinarily projected compared to the surrounding regions at a surface of the manufactured metal foil after the electroprecipitation was completed. This study on the surface property was conducted by randomly collecting samples of 100 mm×100 mm from the manufactured copper foil, observing the rough surface side of each sample with the use of an stereoscopic microscope, and verifying the presence or absence of the unusual deposition.

[0039] Consequently, in case of a copper foil manufactured by an apparatus without the plate-like damper body, many substances which could be regarded as unusual deposits were observed in almost all samples. On the other hand, in case of a copper foil manufactured by an apparatus provided with the plate-like damper body, substances which could be regarded as unusual deposits were very few in any of the samples. Therefore, it has been confirmed that the plate-like damper body is effective for reducing the unusual deposition.

[0040] Industrial Applicability

[0041] According to the present invention, when a metal foil is continuously manufactured through electroprecipitation by the use of a drum-like rotating cathode, thickness uniformity in a transverse direction of the metal foil can be precisely controlled and the production of unusual deposits which may occur on a surface of the metal foil can be also regulated.

Claims

1. An apparatus for electrolytically manufacturing a metal foil comprising a drum-like rotating cathode which electrodeposits the metal foil thereon, an anode whose surface is oppositely disposed along a contour of a peripheral surface of said rotating cathode, and solution-supplying means having an electrolyte-supplying inlet for supplying an electrolyte in between the rotating cathode and the anode from an underside of the rotating cathode,

the metal being electrodeposited onto the peripheral surface of the rotating cathode through an electrolytic reaction while the electrolyte being supplied from the solution-supplying means, then the metal foil electrodeposited being continuously released from the rotating cathode,

wherein the solution-supplying means has a plate-like damper body extending in a transverse direction of the rotating cathode above the electrolyte-supplying inlet.

2. The apparatus for electrolytically manufacturing a metal foil according to claim 1, wherein the plate-like damper body is provided with a projection for divergence extending in a longitudinal direction of the plate at a center of a width of the plate.

3. The apparatus for electrolytically manufacturing a metal foil according to claim 1 or 2, wherein which the electrolyte-supplying inlet is divided into a plurality of sections in the transverse direction of the rotating cathode and a flow rate of the electrolyte supplied from each section of the divided electrolyte-supplying inlet can be regulated.