JP2004300538A - Plating method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plating device capable of facilitating a thickness control, uniformizing a thickness distribution and reducing the amount of a plating liquid. <P>SOLUTION: In the plating device, the plating is performed while retaining a plating liquid between an electrically conductive sheet and rotating rollers set with intervals from the surface of the electrically conductive sheet. Each rotating roller has ruggedness on the surface, and a mechanism of controlling the intervals between the electrically conductive sheet and the rollers is provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for forming a plating film on a sheet.
[0002]
[Prior art]
Various types of electrolytic plating are used in the manufacture of TAB (Tape Automated Bonding), FPC (Flexible Printed Circuit), various wiring substrates such as printed wiring boards, electromagnetic wave shielding members, ultrasonic oscillation base materials, transfer belts for copying machines, and the like. And an electroless plating method is used. Specifically, a metal base film such as copper is formed in advance on a plastic substrate such as polyimide, polyethylene terephthalate (PET), or glass epoxy by a sputtering method, a vacuum evaporation method, or the like. It turns into a film. Although an electroless plating method may be used for the formation of the base film, the thickness is generally increased by electrolytic plating. In order to increase the film thickness, the anode and the conductive substrate are placed opposite to each other in a bath in which a plating solution is stored, and power is supplied to both electrodes.
[0003]
As a material, copper having excellent conductivity is often used. Therefore, the following mainly describes electroless and electrolytic copper plating. However, in the present invention, metal plating other than copper, for example, nickel plating, electrolytic chromium plating, electroless gold plating, or plating by dispersing fine particles in a plating bath is performed. Composite plating to be performed can also be used.
[0004]
Electroless plating Electroless copper plating is a method of depositing metallic copper by adding a reducing agent to an alkaline solution containing a copper compound and a complexing agent. The deposited metallic copper becomes an autocatalyst as it is, and the deposition reaction proceeds continuously. As the precipitation reaction proceeds, the copper solution, formaldehyde, and hydroxide ions in the plating solution become insufficient, so the concentration of these reactive species is constantly analyzed and replenishment of depletion is performed to maintain a constant deposition rate. .
[0005]
Electrolytic copper plating The electrolytic copper plating method is further classified into copper sulfate plating and copper cyanide plating. Here, copper sulfate plating will be mainly described.
The plating solution for copper sulfate plating is a solution in which sulfuric acid and copper sulfate are mixed and dissolved as main components, and an additive and chlorine are added thereto. In the copper sulfate plating bath, divalent copper ions are generated by ionization of copper sulfate, and when energization is started, the copper ions receive (reduce) electrons and deposit on the cathode. At the anode (copper anode), copper loses electrons (is oxidized) to become divalent copper ions and dissolves in the bath, whereby copper ions are replenished. The additive is introduced for leveling of the film, and is used in combination with an organic sulfur compound such as sulfopropyl disulfide, an organic nitrogen compound such as an azo dye, and a polymer surfactant such as polyethylene glycol.
[0006]
In these electrolytic and electroless platings, it is very important to maintain a constant solution by controlling the solution, and to maintain plating quality, and various proposals have been made for a management method therefor. In addition, a constant filtration facility for removing anode slime generated at the time of electrolytic copper plating, a stirring facility for preventing a current from being hindered by polarization, and the like are provided.
Pre-treatment and post-treatment of the substrate are important for obtaining a high-quality plating film. As pretreatment of the substrate, degreasing, washing with water, and the like are performed, and in the case of electroless copper plating, blast treatment or palladium activation is required. As the post-treatment, a series of steps such as water washing, rust prevention treatment, and drying operation are prepared.
[0007]
Although the present invention relates to electrolytic plating, it has been described above because it is also effective for electroless plating. Hereinafter, problems in the electrolytic plating will be described.
It should be noted that patterning (wiring processing) is performed in order to serve as an electronic component or an electromagnetic wave shielding material. As a patterning method, an additive method, a subtraction method, and the like are generally used.
[0008]
As a continuous plating method of a conductor film, there is a method of passing a conductor film through a plating tank containing a plating solution (for example, see Patent Document 1). In addition, there is a method of spraying a plating solution onto a conductive film (for example, see Patent Document 2).
[0009]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2000-192289 (Embodiment of the Invention)
[Patent Document 2] Japanese Patent Application Laid-Open No. 7-238394 (Claims)
[0010]
[Problems to be solved by the invention]
A major problem in conventional electrolytic plating is in-plane variation in plating thickness. The cause of the variation is that when current flows between the anode and the cathode, the current distribution becomes uneven in the plating bath. Therefore, the current distribution is made uniform by optimizing the plating tank structure and introducing a current shielding plate between the anode and the cathode.
[0011]
The thickness control in the electrolytic plating is performed by controlling the current-time product. In the case of electrolytic copper sulfate plating, a current efficiency of almost 100% can be obtained in principle, but the current efficiency is substantially reduced because it is also deposited at places other than the product. Therefore, an anti-adhesion process is also performed to prevent adhesion to places other than products.
[0012]
The scale of the plating bath used varies, but usually a bathtub which is considerably larger than the product size is prepared. For example, when plating a continuous conductive sheet having a width of 90 cm, if a plating tank having a width of 100 cm, a length of 20 cm in the sheet longitudinal direction, and a depth of 100 cm is prepared by estimating a small size, the amount of the plating solution is also in this case. It will be 200 liters. Therefore, the continuous filtration equipment and the stirring equipment had to be large-scale.
[0013]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, a plating method according to claim 1, wherein in the electrolytic plating method of forming a metal plating film on a conductive sheet, a rotating roller provided at a distance from the conductive sheet and the surface of the conductive sheet. And performing plating while holding a plating solution.
[0014]
A plating method according to a second aspect is characterized in that the rotating roller has surface irregularities.
[0015]
The plating method according to claim 3 is characterized in that the conductive sheet is a continuous conductive sheet.
[0016]
5. The electroplating apparatus according to claim 4, wherein the electroplating apparatus forms a metal plating film on a conductive sheet, wherein the plating is performed between a surface of the conductive sheet and a rotating roller provided at a distance from the surface of the conductive sheet. The plating is performed while holding the solution.
[0017]
A plating apparatus according to a fifth aspect is characterized in that the plating apparatus has a mechanism for adjusting a distance between the conductive sheet and the roller.
[0018]
Embodiment
Next, the present invention will be described with reference to the accompanying drawings.
[0019]
FIG. 1 shows an embodiment of the present invention, in which a conductive side of a continuous conductive sheet 4 is connected to a negative side of a power supply 7 by a power supply roller 6. On the other hand, the anode 5 is provided in the liquid pan 8. The plating solution 9 is pumped out by the rotation of the lower roller 1, and a liquid pool 3 is formed between the top of the lower roller 1 and the conductive sheet 4. When a current flows from the anode 5 to the conductive sheet 4 through the liquid reservoir 3, a plating film is formed on the conductive sheet 4.
[0020]
The plating thickness controller is adjusted according to the amount of current and the transport speed of the conductive sheet, and there is an optimum value for the amount of current. When the amount of current is low, the gloss of the plating film cannot be obtained, and when the amount of current is high, energization is inhibited by polarization, and hydrogen gas is generated by electrolysis. Furthermore, the plating film becomes rough due to the local growth of crystal grains. In the case of electrolytic copper sulfate plating, the current amount is optimally set depending on the additive, but is about 0.005 to 0.04 A / cm ² . Therefore, in practice, it is preferable to fix the amount of current and adjust the plating film thickness by the transport speed of the conductive sheet.
[0021]
Examples of the conductive sheet include a sheet formed by forming a metal such as copper on a plastic film such as polyethylene terephthalate or polyimide by sputtering or vacuum deposition. However, there is no particular limitation as long as the sheet is conductive. Here, the material of the plastic film is not particularly limited other than the above two, and may be a woven fabric.
[0022]
Surface of lower roller 1 There is no particular limitation on the uneven shape and processing method provided on the surface of lower roller 1. The provision of the unevenness on the surface of the lower roller 1 is performed using mechanical punching, pushing, laser or the like. Examples of the shape include various shapes such as an oblique line type, a cup type, and a tortoiseshell type. There is no particular limitation on the size of the uneven shape. However, the current required for plating flows along the plating solution on the surface of the lower roller 1. In order to secure a sufficient amount of current, the uneven shape and size are appropriately selected.
[0023]
Spacing Adjustment The spacing between the sheet surface and the rotating roller is a very important parameter. This interval must be set to a certain size or less so that at least the plating solution is held between the sheet surface and the roller. This size is determined by the surface tension and viscosity of the plating solution. In order to adjust the interval, the upper roller 2 in FIG. 1 or the guide roller 10 in FIG. 2 may be vertically movable.
[0024]
FIG. 2 shows another embodiment of the present invention, in which a continuous conductive sheet 4 is supported by two guide rollers 10. Although two examples of the apparatus configuration relating to the formation of the plating film on the continuous conductive sheet 4 have been described, the present invention is effective even when the conductive sheet is plate-shaped. In this case, although the apparatus configuration and the like are different from those in FIGS. 1 and 2, plating is performed while holding a plating solution between a surface of the plate-shaped conductive sheet and a rotating roller provided at an interval. All cases are included if it is a plating method.
[0025]
In the plating method according to the present invention, only a portion of the conductive sheet that contacts the liquid pool is plated. Therefore, the current consumed other than plating can be made almost zero, and the current efficiency approaches 100%. Further, since there is no current distribution that causes thickness variations in the sheet width direction (the depth direction in FIG. 1), thickness variations are suppressed. Further, the amount of the plating solution used is very small in comparison with a conventional plating tank due to the configuration of the apparatus. For this reason, the filtration equipment and the waste liquid treatment equipment are also reduced in scale, and convenience is enhanced. Further, since the plating solution is constantly stirred by the rotation of the lower roller, the size of the stirring equipment is small.
[0026]
The conductive sheet 4 shown in FIG. 1 is usually subjected to pre-treatment and post-treatment. Known equipment can be applied to these facilities.
[0027]
【Example】
Hereinafter, details will be described with reference to examples.
[Example 1]
[0028]
80 g of copper sulfate, 200 g of sulfuric acid, 60 mg of chloride ions, and 2.5 ml of an additive (Top Lucina H-380 manufactured by Okuno Pharmaceutical Co., Ltd.) were added to pure water per liter of the plating solution to prepare a plating solution.
[0029]
As the lower roll, a roll whose surface shape was obliquely cut at intervals of 0.5 mm was used. The depth of the hatched portion was 0.5 mm. The plating solution was put into a solution pan, and the lower roll was started to rotate at a surface speed of 15 m / min. The diameter of the roller is 150 mm.
[0030]
As a continuous conductive sheet, a sheet in which 0.3 μm thick copper was formed on the surface of a 125 μm thick polyethylene terephthalate film by a sputtering method was used. The surface resistance of this sheet was about 1 Ω / □.
[0031]
This conductive sheet was touched to the lower roll that started rotating, and feeding was started at a speed of 3 cm / min.
[0032]
Next, energization was started by controlling the amount of current so that the current density became 0.04 A / cm ² . The thickness of the obtained copper film was about 1 μm including the sputtered film.
[0033]
【The invention's effect】
The present invention is different from the conventional plating bath system in that the thickness is easily controlled, the thickness distribution is uniform, and the amount of the plating solution is small.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an embodiment of a plating apparatus according to the present invention.
FIG. 2 is a schematic view showing another embodiment of the plating apparatus according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Lower roller 2 Upper roller 3 Liquid pool 5 Anode 4 Continuous conductive sheet 6 Power supply roller 7 Power supply 8 Liquid pan 9 Plating solution 10 Guide roller

Claims (5)

In the electrolytic plating method for forming a metal plating film on a conductive sheet, plating is performed while holding a plating solution between the conductive sheet and a rotating roller provided at an interval from the conductive sheet surface. A plating method characterized in that: The plating method according to claim 1, wherein the rotating roller has surface irregularities. The plating method according to claim 1, wherein the conductive sheet is a continuous conductive sheet. In an electroplating apparatus for forming a metal plating film on a conductive sheet, plating is performed while holding a plating solution between the conductive sheet surface and a rotating roller provided at an interval from the conductive sheet surface. A plating apparatus. The plating apparatus according to claim 4, further comprising a mechanism for adjusting a distance between the conductive sheet and the roller.

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