JP2006203013A - Pattern formation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plating method which makes it possible to form a pattern film and a through hole film uniformly in thickness on both faces rapidly, in manufacturing a planar coil having a coil conductor filament with a small variation in DC resistance which can be widely used for various electric products including industrial apparatuses, consumer apparatuses, etc. <P>SOLUTION: Plating is conducted using a copper sulfate plating liquid having the copper sulfate concentration of 100 g/l and the sulfuric acid concentration of 220 g/l to make the flow rate uniform near a work, and plating is conducted by a periodic inversion current application method wherein application of positive current at a positive current density of 6 A/dm<SP>2</SP>for 10 ms and application of negative current at a negative current density of 12 A/dm<SP>2</SP>for 0.5 ms are alternately performed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pattern forming method for manufacturing a planar coil that can be widely used for various electrical components (electroacoustic transducers, transformers, motors, etc.) such as industrial equipment and consumer equipment. The present invention relates to a high current density pattern plating technique for forming a coil conductor pattern.

  In recent years, along with the reduction in size, thickness, and weight of electronic devices, it is necessary to reduce the size, thickness, and weight of planar coils used in these devices. Improvement is strongly desired. Typical manufacturing methods include etching and plating, but there is a need for a high space factor coil with narrow spaces between the wires and few gaps, so there is no need for a plating method, so semi-additive, additive, etc. The manufacturing method is well known.

  As for the semi-additive method described above, a resist is formed so as to cover the surface of the underlying conductor layer previously formed on the insulating substrate except for the coil portion, and electroplating by direct current is performed using the underlying conductor layer as a base. To form a conductor layer. Then, after peeling a resist pattern, it is a manufacturing method of removing the unnecessary base conductor layer exposed by peeling of a resist pattern by an etching.

  At that time, as a general pattern plating, copper plating is used as a pattern forming material, and the technique is becoming more important. Copper plating mainly uses copper sulfate plating, and is a solution in which sulfuric acid and copper sulfate are mixed and dissolved as main components, and a brightener and chlorine are added thereto. Copper sulfate plating baths were previously poor in throwing power, but in recent years, by improving the brightener, the copper sulfate concentration is lowered and the sulfuric acid concentration is raised to increase the liquid conductivity and to activate the polarization. Larger, highly uniform baths have been developed and are often used as electrolytic copper plating for printed circuit boards.

However, since the copper sulfate concentration is low, the cathode current density can only be increased to 3 A / dm ² . If it is more than that, burn will occur due to insufficient supply of copper ions in the vicinity of the interface, resulting in poor in-plane uniformity. As a result, the resistance value of the coil conductor cannot be made constant. Further, as an important factor for improving the cathode current density and ensuring in-plane uniformity, optimization and uniformization of the plating solution flow rate at the time of plating can be mentioned, and by implementing this, productivity and yield can be improved.

As prior art document information relating to the invention of this application, for example, Patent Document 1, Patent Document 2, Patent Document 3, and Non-Patent Document 1 are known.
JP 56-94937 A Japanese Unexamined Patent Publication No. 64-61986 Japanese Patent Laid-Open No. 64-82598 Surface technology, 50, 135 (1999)

  The disadvantage of the conventional pattern plating is that, in the direct current application method, current concentration occurs in the periphery of a multi-faced workpiece, the shape and arrangement of the coil pattern, or the shape of the workpiece feeding portion. Therefore, the conductor of the current concentration part is formed thick, and when the coil pattern is faced with several to thousands, the plating thickness varies, and it is necessary to make the work size as small as possible. As a result, the yield surface, In terms of cost, it was inferior in mass productivity.

In addition, it is necessary to perform plating that achieves productivity and yield at the same time. In consideration of productivity, the cathode current density needs to be 6 A / dm ² or more, but in a highly uniform bath with improved electrodeposition. However, since the copper sulfate concentration is low, the cathode current density can be increased only by 3 A / dm ² at the maximum, and if it exceeds this, the in-plane uniformity is inferior and the resistance value of the coil conductor cannot be made constant. It was. Therefore, the present invention is a method of manufacturing a large amount of planar coils having coil conductor wires with small DC resistance variation, which can be widely used in various electrical products such as industrial equipment and consumer equipment, and is based on plating in consideration of productivity and yield. An object of the present invention is to provide a pattern forming method.

  In order to achieve the above object, the present invention has the following configuration.

  The invention according to claim 1 of the present invention is a method for manufacturing a planar coil in which local etching is performed by applying a negative current opposite to conductor formation in the same plating solution as electroplating. In order to laminate the central conductor layer by repeating the electrolytic etching to apply the current opposite to the conductor formation by electroplating in the same plating solution as electroplating, excess conductor formed in the current concentration part Since the conductor layer is formed while removing the film by electrolytic etching, uniform plating with little variation can be performed regardless of the shape of the multifaceted work and the coil pattern.

  The invention according to claim 2 of the present invention is a method for manufacturing a planar coil in which the current density of a negative current passed for local etching is larger than the current density of a positive current passed for forming a conductor of the surface conductor layer. Because the current density of the negative current that flows for local etching is larger than the current density of the positive current that flows for forming the conductor, it may be partially affected by the periphery of the workpiece and the coil pattern shape that are multifaceted when forming the conductor. In this case, excessive plating formed excessively at locations where current is concentrated is preferentially etched, so that uniform plating with little variation can be performed regardless of the shape of the multi-faced workpiece or coil pattern.

  The invention according to claim 3 of the present invention is a method for producing a planar coil pattern in which the time required for one cycle for repeating the formation of a conductor by electroplating and local etching is 0.1 seconds or less. By shortening the cycle time and frequently repeating the formation and etching of the conductor, the excess plating formed in the portion where the current is partially concentrated is preferentially etched, so it is multi-faceted. It is possible to perform uniform plating with little variation regardless of the shape of the workpiece or coil pattern.

  The invention described in claim 4 of the present invention is a plating method performed at a maximum plating production rate of 2 μm / min, and enables high-speed plating with excellent mass productivity.

  According to the fifth aspect of the present invention, the in-plane uniformity can be further improved by making the flow velocity near the workpiece constant.

  The invention according to claim 6 of the present invention can further improve the pattern formation accuracy by making the through-hole plating film thickness uniform with the pattern plating film thickness.

  The pattern plating by the high current density application method of the present invention can improve the cathode current density and the in-plane uniformity by the periodic reversal current application method as compared with the direct current application method, thereby improving productivity and yield. There is an effect of being able to plan.

(Embodiment)
Hereinafter, the invention according to the first to fifth aspects of the present invention will be described with reference to embodiments.

  1A to 1I are schematic views for explaining a planar coil manufacturing process according to an embodiment of the present invention. First, an insulating substrate 2 made of a polyimide film with a thickness of 25 μm, in which the base conductor layer 1 made of a 9 ± 1 μm thick Cu foil was formed on both surfaces, was prepared. The work size is 250 × 500 mm (FIG. 1A).

  Next, the entire Cu foil was etched to a thickness of 3 ± 1 μm by a slice etching apparatus using an etching solution made of a sulfuric acid hydrogen peroxide solution (FIG. 1B). Next, a through hole 3 having a diameter of 100 μm was provided by a punching apparatus for drilling so as to penetrate the base conductor layer 1 and the insulating substrate 2 on both sides (FIG. 1C).

  Next, the thickness of the Cu foil was etched to 2 ± 1 μm using a soft etching solution made of a sulfuric acid hydrogen peroxide solution (FIG. 1D). Next, a 37 μm dry film resist 4 was laminated on the surface of the underlying conductor layer 1 on both sides. And it patterned with the film mask which imposed 300 coil patterns (FIG.1 (e)). For patterning, a spiral pattern having a resist width of 40 μm and a space between resists of 40 μm was formed (FIG. 1F).

Next, in a plating apparatus in which the flow velocity in the vicinity of the workpiece is made uniform on the underlying conductor layer 1 including the through-hole portion not covered with the resist 4 by a propeller type flowmeter, the copper sulfate concentration is 100 g / l, sulfuric acid Using a copper sulfate plating solution having a concentration of 220 g / l, a positive current having a positive current density of 6 A / dm ² and an application time of 10 mS shown in FIG. 2 and a negative current having a negative current density of 12 A / dm ² and an application time of 0.5 mS are applied. Plating was performed by a periodic reversal current application method applied alternately to form both sides of a 36 μm plated conductor layer 5 (FIG. 1 (g)). The plating thickness variation at this time was as small as ± 13%. This was a reduction of about 40% with respect to the plating thickness variation ± 30% when the current density was 6 A / dm ^{2 in} the direct current application method. Further, when the patterns are formed simultaneously on both sides, the plating is also performed in the through hole 3 at the same time, but the film thickness is uniform with the pattern plating thickness.

  Next, the resist pattern was removed with an organic amine solution at 40 ° C. using a resist stripping apparatus (FIG. 1H). Thereafter, the underlying conductor layer was etched using an etching apparatus using an etching solution comprising a sulfuric acid hydrogen peroxide solution to form a coil conductor filament (FIG. 1 (i)).

  The high current density application method in pattern plating according to the present invention realizes productivity improvement by improving cathode current density and yield improvement by improving in-plane uniformity of pattern plating. Useful.

Process sectional drawing of the manufacturing process of the planar coil in embodiment of this invention The figure which shows the periodic inversion current application system in embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ground conductor layer 2 Insulating board 3 Through hole 4 Dry film resist 5 Plating conductor layer

Claims (6)

Electroplating is performed by applying a positive current in a copper sulfate plating solution, and a predetermined pattern is formed by applying a negative current opposite to the conductor formation in the same plating solution as the electroplating to perform local electrolytic etching. Pattern forming method. 2. The pattern forming method according to claim 1, wherein a current density of a negative current passed for local etching is larger than a current density of a positive current passed for forming a conductor layer. The pattern forming method according to claim 1, wherein the time required for one cycle for repeating the formation of the conductor by electroplating and the local etching is 0.1 second or less. The pattern forming method according to claim 1, wherein the electroplating with a copper sulfate plating solution has a maximum plating production rate of 2 μm / min. The pattern forming method according to claim 1, wherein the electroplating with the copper sulfate plating solution is performed at a constant flow speed on the workpiece surface. 2. The pattern forming method according to claim 1, wherein the electroplating with the copper sulfate plating solution is performed so that the pattern plating thickness and the through-hole plating thickness are uniform.

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