JP2001267166A - Method for manufacturing plane coil, plane coil and transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the occupation of volume of a coil conductor line in a plane coil having a coil conductor line on an insulation substrate and to make the sectional shape and size of the coil conductor line to be uniform regardless of the position in the coil. SOLUTION: This method for manufacturing a plane coil includes a step for forming a base conductor layer for forming a base conductor layer on an insulation substrate, a step for forming a resist pattern for forming a resist pattern in a manner that the surface of the base conductor layer is spirally exposed, a first electroplating step for a central conductor having an almost square section by conducting an electroplating using the base conductor layer as a base, a step for peeling off the resist pattern, and a second electroplating step for completing a coil conductor line comprising the central conductor and surface conductor layer covering it by forming the surface conductor layer through electroplating using the central conductor as a base.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a planar coil having a spiral coil conductor on an insulating substrate, a method of manufacturing the planar coil, and a transformer using the planar coil.

[0002]

2. Description of the Related Art A planar coil is formed by spirally forming conductive wires on an insulating substrate. For example, a biaxial actuator of a digital audio disk, a power supply coil of a CPU of a mobile computer, a planar display (liquid crystal display) ) Is widely used as a power supply or signal coil.

[0003] By the way, as the planar coil, a coil having a narrow and thick, so-called high-aspect conductor strip arranged at a narrow interval has been required. The direct current resistance is reduced by forming the conductor wire in a high aspect pattern. The present applicant has disclosed a flat coil having a narrow, thick, high-aspect conductor strip having a mushroom-shaped cross section and a method of manufacturing the same.
7 and JP-A-11-204361.

[0004] The manufacturing method described in the above-mentioned Japanese Patent Application Laid-Open No. 11-204361 has the following steps: (A) a step of providing a thin film layer for plating on an insulating substrate; (B) a step of laminating a positive photoresist layer thereon. (C) a step of subjecting the positive photoresist layer to photolithography to form a photoresist mask pattern from the positive photoresist layer, and (D) performing a plating process to expose the exposed portion of the plating underlying thin film layer and its vicinity. Expanding a coil conductor plating layer having a mushroom cross section on the covering portion of the positive photoresist mask pattern, (E) plating and covering the entire coil conductor plating layer with a protective metal thin film layer, F) The positive photoresist layer between the coil conductor plating layers exposed by developing after irradiating the entire surface with an actinic ray is removed. Successively with a step and (G) removing only the plating base film layer is selectively etched to removed by.

Japanese Patent Application Laid-Open No. Hei 7-142254 discloses that it is difficult to increase the thickness of a coil pattern formed by a printed wiring technique. In addition, a method is proposed in which an electroplating layer is provided by electroplating on the coil pattern to reinforce the conductor of the coil pattern. That is, in this method, a coil pattern is formed by a subtractive method using an insulating substrate having a conductor layer, for example, a copper-clad substrate, and electroplating is performed using the coil pattern as a base to thicken the coil pattern.

[0006]

In order to achieve both the miniaturization and high performance of a planar coil, it is important to increase the space factor of the coil conductor wire. In this specification, the space factor of the coil conductor wire is defined as a width of the arrangement pitch of the coil conductor wire and a height of the coil conductor wire in a cross section perpendicular to the direction in which the coil conductor wire extends. Means the ratio of the cross-sectional area of the coil conductor wire to the rectangular area.

Considering the prior art from the viewpoint of the space factor,
In the planar coil described in JP-A-11-204361, as shown in FIG. 2 (C), the cross section of the coil conductor wire 4 has a mushroom shape, and the neck portion of the mushroom is thinner than the head portion. There are limits to improvement. Further, since the high aspect conductor is grown by electroplating from the surface of the plating base thin film layer having a thickness of about 1 μm, the upper part of the coil conductor wire section has a relatively large radius of curvature curve. Therefore, there is a limit in improving the space factor from this point as well.

In the method described in the publication, a high aspect ratio is realized by increasing the growth rate of the coil conductor wire in the thickness direction with respect to the width direction. Specifically, with the growth of the coil conductor filament, the distance between adjacent filaments is reduced, and with the shortening of the distance, the growth rate in the width direction is lower than the growth rate in the thickness direction. As a result, The aspect ratio of the coil conductor wire section increases. In order to realize such a high aspect, it is necessary to sufficiently perform stirring during electroplating. On the other hand, in order to improve the productivity, it is preferable to form a large number of coil conductor patterns at once using a substrate having an area as large as possible. However, since it is difficult to stir the plating bath uniformly over the entire surface of a large-area substrate, the method described in the publication is:
There are limits to productivity.

Further, in the method described in the publication, the shape and dimensions of the cross section of the coil conductor wire are affected by the coil pattern. For example, the degree of anisotropic growth differs between a place where the arrangement pitch of the coil conductor wires is narrow and a place where the pitch is wide, since the circulation of the plating bath is not the same. Therefore, differences tend to occur in the thickness and aspect ratio of the coil conductor. Therefore, it is difficult to control the cross-sectional shape of the coil conductor wire independently of the coil pattern, and the degree of freedom in design is likely to be limited.

On the other hand, in the method described in JP-A-7-142254, a conductor layer serving as a base for electroplating is patterned in a coil shape in advance, and the coil-shaped conductor layer is formed by a conventional printing method. It cannot be made thick because it is formed by wiring technology. Therefore, the electric resistance of the conductor layer is increased, so that when it is necessary to form a long independent pattern such as a spiral pattern having a large number of turns, the electroplated layer becomes thinner at a position away from the power supply portion. That is, there is a problem that the entire coil conductor cannot be formed to a uniform thickness. This problem can be improved by lowering the plating current value, but when the plating current value is reduced, the work time is greatly increased, and the productivity is significantly deteriorated.

In the method described in the above publication, the conductor layer serving as a base is thin.
The same problem as in the method described in JP-A-4361 is caused.

An object of the present invention is to increase the space factor of a coil conductor in a planar coil having a coil conductor on an insulating substrate. Another object is to increase the space factor regardless of the coil pattern and position.
It is another object of the present invention to make the cross-sectional shape and dimensions of the coil conductor wire uniform regardless of the position in the coil. Another object of the present invention is to enable such a planar coil to be manufactured by a method suitable for mass production.

[0013]

The above object is achieved by the following (1).
This is achieved by the present invention according to (10). (1) a base conductor layer forming step of forming a base conductor layer on an insulating substrate, a resist pattern forming step of forming a resist pattern such that the surface of the base conductor layer is spirally exposed, By performing plating, a first electroplating step of forming a center conductor having a substantially rectangular cross section, a resist pattern stripping step of stripping the resist pattern, and electroplating using the center conductor as a base to form a surface conductor layer A method for manufacturing a planar coil, comprising a second electroplating step of forming and completing a coil conductor wire comprising the center conductor and the surface conductor layer covering the center conductor. (2) The method for producing a planar coil according to (1), further comprising an etching step of removing an underlying conductor layer exposed by stripping the resist pattern by etching between the resist pattern stripping step and the second electroplating step. (3) The method for manufacturing a planar coil according to (2), wherein the thickness of the central conductor is at least five times the thickness of the underlying conductor layer. (4) The method of manufacturing a planar coil according to the above (1), wherein the underlying conductor layer is spirally formed in the underlying conductor layer forming step. (5) The method for manufacturing a planar coil according to any one of (1) to (4), wherein the thickness of the center conductor is set to be not less than 1/3 of the thickness of the coil conductor wire. (6) The method for manufacturing a planar coil according to any one of (1) to (5), wherein a width of the cross section of the resist pattern is equal to or more than の of a thickness. (7) The above-described (1) to (1) to manufacturing a planar coil having a region where the space factor of the coil conductor wire is 70% or more.
(6) The method for manufacturing a planar coil according to any of (6). (8) A planar coil manufactured by the method according to any one of (1) to (7). (9) The planar coil according to (8), wherein an oxide layer is present at an interface between the center conductor and the surface conductor layer. (10) A transformer formed by stacking a plurality of the planar coils of (8) or (9).

[0014]

According to the present invention, as shown in FIG. 1 (C), first, in a first electroplating step, a center conductor 41 having a substantially rectangular cross section is formed by utilizing a resist pattern 11. Next, as shown in FIG. 1E, in the second electroplating step, the surface conductor layer 42 is formed using the center conductor 41 as a base, and the coil conductor wire 4 is completed. As a result, the following effects are realized.

In the present invention, since the cross-sectional shape of the center conductor 41 is substantially rectangular, the electric field concentrates on the corners of the center conductor 41 in the second electroplating step. Therefore, the cross section of the finally obtained coil conductor wire 4 becomes close to a rectangle, and as a result, the space factor of the coil conductor wire becomes high. For example,
In the region where the coil conductor wires are arranged most densely, the space factor can be 70% or more, and can be 90% or more.

In the present invention, for example, 1
After the center conductor 41 is formed to a thickness of or more, the resist pattern is removed, a groove is provided between the adjacent center conductors 41, and the surface conductor layer 42 is isotropically or anisotropically filled to fill the groove. Let it grow. Accordingly, Japanese Patent Application Laid-Open No. 11-2
Compared to the method described in Japanese Patent No. 04361, the thickness of the conductor that grows anisotropically is small even if the coil conductor filaments have the same aspect ratio. As described above, the degree of anisotropic growth is affected by the plating conditions and the coil pattern. However, in the present invention, since the thickness of the conductor that grows anisotropically is smaller than the total thickness of the coil conductor filaments, The cross-sectional shape and dimensions of the conductor wire and the distance between adjacent coil conductor wires are less affected by plating conditions and coil patterns. Therefore, the margin of the manufacturing condition is widened. In addition, a large number of planar coils can be simultaneously formed using a large-area insulating substrate. Further, even when the array density of the coil conductors is not constant within one plane coil, the thickness of the coil conductors can be made substantially constant.

The width of the groove existing between the adjacent center conductors 41 and the dimensional accuracy of the central conductor 41 are determined by the patterning accuracy of the resist pattern 11, and the dimensional accuracy of the resist pattern is substantially the same as the dimensional accuracy of the photomask. Become. Therefore, the dimensional accuracy of the groove and the center conductor 41 is extremely accurate. Therefore, from this point as well, the cross-sectional shape and dimensions of the coil conductors and the distance between adjacent coil conductors can be accurately determined.

Further, according to the present invention, since the distance between adjacent coil conductors can be controlled accurately, even if the distance is designed to be small, a short circuit may occur due to contact between the coil conductors during production. Hateful. Therefore, the space factor of the coil conductor can be increased.

The present invention is also effective when the distance between adjacent coil conductors is large. For example, in a high-frequency coil having a small number of turns, the distance between lines is generally large, so that the surface conductor layer grows isotropically in the second electroplating step. However, in the present invention, since the center conductor thicker than the base conductor layer used in the conventional manufacturing method is formed in advance, even when the surface conductor layer is grown isotropically, the finally obtained coil conductor wire is obtained. Has a higher aspect ratio than isotropic growth in the conventional manufacturing method. In order to increase the Q value of the high-frequency coil when the circumference of the coil conductor wire is the same, the magnetic flux penetrating through the coil conductor wire only needs to be reduced. It is effective for

In the present invention, usually, a step of etching the underlying conductor layer 3 after the formation of the center conductor 41 and before the formation of the surface conductor layer 42 is provided. This etching usually involves
Although wet etching is used, unlike the case where the underlying conductor layer is etched after the entire coil conductor wire is formed, the distance between the center conductors 41 is large, so that the flow of the etching solution is good and the etching is easy.

In the present invention, since the base conductor layer 3 is usually provided on the entire surface of the insulating substrate 2, unlike the case where the base conductor layer 3 is patterned in advance, the formation of the center conductor 41 can be performed at high speed regardless of the coil pattern. Can be done.

Further, since the surface conductor layer 42 is formed by electroplating with the center conductor 41, which is significantly thicker than the conventional base conductor layer, as the base, the surface conductor layer does not become thin even at a position far from the power supply portion.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The manufacturing method of the present invention is shown in FIG.
This will be described with reference to FIG.

First, as shown in FIG. 1A, a base conductor layer 3 is formed on the surface of an insulating substrate 2.

The insulating substrate 2 may be made of a single crystal such as glass epoxy, plastic, quartz, SiO ₂ , A
Various insulating ceramics such as l ₂ O ₃ and ferrite
It can be arbitrarily selected from those conventionally used for a substrate of a planar coil. Usually, the thickness of the insulating substrate 2 may be selected from the range of 10 to 500 μm.

The constituent material of the base conductor layer 3 is not particularly limited as long as it functions as a base layer in electroplating. For example, Ti, Ni, Cr, Cu, Al, S
Any of n, Zn, Au, Ag, and an alloy containing at least one of these may be used. The underlying conductor layer 3 may be a single layer or a laminate of two or more layers having different compositions. The base conductor layer 3 can be formed by any means such as a vacuum film forming method such as vapor deposition, sputtering, or ion plating, an electroless plating method, and attaching a metal foil. In this case, an electroplating method can also be used except when the lowermost layer is formed. The thickness of the underlying conductor layer 3 is suitably in the range of 0.5 to 10 μm when using a vacuum film forming method or plating method, and is suitably in the range of 5 to 18 μm when attaching a foil.

Next, as shown in FIG. 1B, a resist pattern 11 is formed on the underlying conductor layer 3 so that the surface of the underlying conductor layer 3 is spirally exposed. The resist pattern can be formed by first forming a photoresist layer, performing pattern exposure on the photoresist layer, and then developing.
The photoresist to be used is not particularly limited, and either a positive type or a negative type may be used. However, in the present invention, it is necessary to use a dry film because the resist pattern needs to be relatively thick. It is preferable that the cross section of the resist pattern has a width equal to or more than の of the thickness. If the width is too narrow relative to the thickness, the mechanical strength becomes insufficient, and deformation during plating tends to occur. Further, it is difficult to stably form a pattern whose width is too narrow with respect to the thickness by photolithography. Resist pattern 11
Is not particularly limited. The thicker resist pattern 11 is preferable because the center conductor 41 can be made thicker. However, in the current technology, 100 μm is considered in consideration of mass productivity.
m is the limit.

Next, as shown in FIG. 1C, electroplating is performed using the underlying conductor layer 3 exposed from the resist pattern 11 as a foundation, thereby forming a center conductor 41 having a substantially rectangular cross section. In the present invention, this step is called a first electroplating step.

The thickness of the center conductor 41 is limited by the thickness of the resist pattern 11. Normally, the center conductor 41 is formed so as to be thinner than the resist pattern 11, but it is also possible to form the center conductor 41 exceeding the thickness of the resist pattern 11. The relative thickness of the center conductor 41 to the thickness of the finally formed coil conductor wire is preferably 1/3 or more, more preferably 1/2 or more. If the relative thickness is too small, the effect of the present invention by providing the center conductor 41 will be insufficient. However, in order to ensure mechanical strength, the width of the resist pattern 11 cannot be significantly reduced. Therefore, if the relative thickness of the center conductor 41 is increased, that is, if the thickness of the surface conductor layer 42 is reduced, adjacent coils The distance between the conductor wires cannot be reduced. As a result, a high space factor cannot be obtained. Therefore, the relative thickness is preferably 2/3 or less, more preferably 60% or less.

The aspect ratio of the center conductor 41, that is, the value obtained by dividing the height by the width is preferably 0.5 or more, more preferably 0.7 or more. When the aspect ratio of the center conductor 41 is low, it is difficult to increase the aspect ratio of the coil conductor wire. Further, if an attempt is made to form a coil conductor filament having a high aspect ratio despite the low aspect ratio of the center conductor 41, the degree of anisotropic growth of the surface conductor layer 42 must be increased. The effect cannot be obtained sufficiently. However, the aspect ratio of the central conductor 41 is usually 2 or less, preferably 1 or less because the aspect ratio of the resist existing between the adjacent central conductors cannot be made so high (strength becomes low) in the cross section of the resist pattern. .

The constituent material of the center conductor 41 is not particularly limited, and may be appropriately selected from the various conductive materials described in the description of the base conductor layer 3. However, copper is particularly preferable because of its low electric resistance and low cost. .

Next, as shown in FIG. 1D, the resist pattern 11 is peeled off, and the underlying conductor layer 3 under the resist pattern 11 is removed.
Expose the surface. For this stripping, a normal resist stripping agent may be used.

Next, the underlying conductor layer 3 exposed by peeling of the resist pattern 11 is removed by etching. This etching method is not particularly limited, but usually,
Utilize wet etching. Base conductor layer 3 and center conductor 4
1 is etched by the same etching solution, and when wet etching is performed without masking the center conductor 41, that is, when quick etching is performed, the vicinity of the surface of the center conductor 41 is also etched. However, the influence of quick etching on the center conductor 41 can be reduced by forming the center conductor 41 sufficiently thick, preferably five times or more thicker than the base conductor layer 3. The base conductor layer 3 is made of a material that can be etched by an etchant that does not attack the center conductor 41.
With this configuration, the influence on the center conductor 41 can be prevented.

Next, as shown in FIG. 1E, a surface conductor layer 42 is formed by performing electroplating with the center conductor 41 as a base. In the present invention, this step is called a second electroplating step. By the second electroplating step, the coil conductor wire 4 including the center conductor 41 and the surface conductor layer 42 covering the center conductor 41 is completed. The constituent material of the surface conductor layer 42 is not particularly limited, and a material different from that of the center conductor 41 may be used. However, considering simplification of the manufacturing process,
Usually, it is preferable to use the same material as the center conductor 41.

The growth rate of the surface conductor layer 42 during the electroplating may be the same or different in the width direction and the thickness direction. If the conductive growth is performed, a coil conductor filament having a higher aspect ratio can be obtained. However, since it is difficult to keep the degree of anisotropic growth constant over the entire area of the planar coil, if the degree of anisotropic growth is large, the cross-sectional shape and dimensions of the coil conductor wire tend to vary greatly depending on the position. Considering this point, it is preferable that the degree of anisotropic growth is not so large. Specifically, the growth rate in the thickness direction is preferably 10 times or less, more preferably 3 times or less the growth rate in the width direction. Normally, the growth rate in the thickness direction does not fall below the growth rate in the width direction.

In the coil conductor filament formed by the above steps, the aspect ratio in the cross section shown in FIG.
The value obtained by dividing the thickness by the width can be 0.5 or more.

When the working atmosphere between the first plating step and the second plating step is an oxidizing atmosphere such as air, an oxide layer is formed at the interface between the center conductor 41 and the surface conductor layer 42. May be done.

In the illustrated method, in the first electroplating step for forming the center conductor 41, electroplating is performed using the unpatterned base conductor layer 3 as a base. Therefore, even when it is necessary to form a long independent pattern such as a spiral pattern having a large number of turns, the electric resistance of the underlying conductor layer 3 does not increase. Therefore, since the plating current value can be increased, even if the center conductor 41 is formed at a high speed, there is little variation in thickness.

However, when the plating current value does not need to be so large, for example, when the center conductor 41 does not need to be formed so thick, specifically, the thickness of the coil conductor wire is made so thick. When it is not necessary, or when the aspect ratio of the coil conductor wire does not need to be so large, the base conductor layer 3 may be formed in a spiral shape, and the center conductor 41 may be formed in that state. In the method of removing the underlying conductor layer 3 by quick etching, the center conductor 4 is removed.
Although the vicinity of the surface of the first conductor 1 is also etched, the dimensional accuracy of the center conductor 41 is slightly reduced. However, if the base conductor layer 3 is patterned in advance, it is not necessary to perform quick etching, so that the dimensional accuracy can be increased. .

The thickness of the coil conductor wire is usually 10 μm
As described above, the thickness is preferably 40 to 300 μm. If the coil conductor wire is too thick, the feature of the planar coil that it can be reduced in thickness becomes indispensable.

The transformer of the present invention can be manufactured by laminating the planar coil of the present invention. In the case of lamination, an insulating layer having a contact hole is formed on the above-mentioned planar coil according to a normal build-up method, and this is used as an insulating substrate. do it.

[0042]

EXAMPLE 1 A glass epoxy substrate (thickness: 100 μm) having a diameter of 3 inches was used as an insulating substrate 2 and a 0.2 mm diameter was placed at a predetermined position.
Then, a 1 μm thick base conductor layer 3 made of copper was formed on both surfaces of the insulating substrate 2 using an electroless copper plating solution (trade name “Buil Copper” manufactured by Okuno Pharmaceutical Co., Ltd.). .

Next, a resist pattern 11 was formed on the underlying conductor layer 3 using a dry film (trade name “P8008” manufactured by Tokyo Ohka Kogyo Co., Ltd.). The thickness of the resist pattern was 80 μm, the width was 60 μm, and the width of the region where the underlying conductor layer 3 was exposed was 60 μm.

Next, using a plating solution having a copper sulfate concentration of 110 g / l, a pipe having small holes was arranged near the cathode, and the plating solution was jetted from the small holes at a rate of 80 mm / sec. The central conductor 41 having a thickness of 75 μm was formed by performing electroplating under the conditions of a density of 9 A / dm ² .

Next, the resist pattern was peeled off by immersing the insulating substrate 2 in a 4% potassium hydroxide solution at 40 ° C. for 10 minutes.

Then, 50 g of ammonium persulfate /
The insulating substrate 2 was immersed in an etching solution containing 2 liters of sulfuric acid and 2% sulfuric acid at 25 ° C., and after visually confirming that the underlying conductor layer 3 was completely removed, the substrate was pulled up. At this time,
The etching depth of the center conductor 41 was about 2 μm.

Next, electroplating was performed in the same manner as when the center conductor 41 was formed, except that the jetting speed of the plating solution was set to 60 mm / sec. The growth anisotropy during the electroplating was 1.6. That is, the growth rate in the thickness direction is 1.times. The growth rate in the width direction.
It was 6 times.

Through the above steps, the planar coil having the coil conductor wire 4 having the shape shown in FIG.
In total, 284 pieces were formed on both surfaces. In each planar coil, the thickness of the coil conductor was 110 μm, and the distance between adjacent coil conductors was 5 μm on average. Further, in the cross section of the coil conductor wire, the radius of curvature at the corners at both upper ends was about 10 μm. The space factor of the coil conductor wire was 90%. The difference in the thickness of the coil conductor between the innermost circumference and the outermost circumference of each planar coil was 3 μm or less. The yield of these planar coils was 98%. The cause of the failure was due to a defect in the resist pattern caused by the adhesion of particles, and no short circuit between lines due to contact between adjacent coil conductor wires was observed. That is, the variation in the cross-sectional shape and dimensions of the coil conductor wire was extremely small.

From the above results, it can be seen that according to the present invention, a planar coil having a high space factor of the coil conductor wire and a good uniformity in the shape and dimensions of the cross section of the coil conductor wire can be obtained.

COMPARATIVE EXAMPLE 1 A planar coil having a mushroom-shaped coil conductor wire was produced in the same manner as in the example of JP-A-11-204361. First, after a base conductor layer was formed in the same manner as in Example 1 above, a positive photoresist (trade name “PMER PA-A” manufactured by Tokyo Ohka Kogyo Co., Ltd.) was formed thereon.
R900 ”) was spin-coated to a dry film thickness of 5 μm, and exposed and developed according to a conventional method to form a resist pattern having a pattern width of 90 μm and a pattern interval of 20 μm. The resist pattern thus obtained has a spiral shape, and the innermost radius is 0.9 m.
m, the number of turns was 11.5. Next, a 110 μm-thick coiled conductor wire was formed in the same manner as in Example 1 except that the jetting speed of the plating solution was set to 50 mm / sec. The anisotropy of growth during the electroplating was 2.8.

[0051] Subsequently, using a gloss Watts bath containing NiSO ₄ · 7H ₂ O 280 grams / liter, NiCl ₂ · 6H ₂ O45 grams / liter, the H ₃ BO ₃ 40 g / liter, the surface of the coil conductor striatum A nickel layer having a thickness of 2 μm was formed on the entire surface by electroplating. Next, the entire surface is irradiated with ultraviolet light using the coil conductor wire covered with the nickel layer as a mask to expose only the positive photoresist existing between the wires, and then a developing solution (trade name, manufactured by Tokyo Ohka Kogyo Co., Ltd.) The exposed portion was dissolved and removed by "P-7G"). Thereafter, only the underlying conductor layer exposed between the filaments is removed by etching with an alkali etching solution (trade name “A process” manufactured by Meltex Co., Ltd.), and then cut to obtain an outer dimension of 3.1 mm × 3. .
284 planar coils of 1 mm × 0.4 mm were manufactured.

The obtained coil conductor filament had the cross-sectional shape shown in FIG. 2 (B). In this cross section, the radius of curvature of the corner is about 50 μm, and the distance between adjacent coil conductors is 5 μm above the coil conductors.
m and 15 μm at the bottom. Therefore, the space factor of the coil conductor wire is lower than that of the planar coil manufactured in Example 1. The space factor of the coil conductor was 75%. The yield of these planar coils was 70%. The causes of the defects were mostly line-to-line short-circuits due to variations in the spacing between the coil conductors and short-circuits due to poor etching of the underlying conductor layer, and the occurrence frequency of both was approximately the same. The difference in the thickness of the coil conductor wire between the innermost and outermost circumferences of each planar coil is about 10 μm.
Met. The reason for such a large difference is that the growth anisotropy during electroplating is high.

COMPARATIVE EXAMPLE 2 The same procedure as in Comparative Example 1 was carried out except that the plating conditions such as the current value were controlled to improve short circuit between lines and poor etching of the underlying conductor layer so that the yield was 98%. A planar coil was manufactured. In these planar coils, the distance between the coil conductors was 15 μm, and the space factor was further reduced as compared with Comparative Example 1. The space factor of this coil conductor wire was less than 70%.

Example 2 A coil for a flat motor was manufactured in the same procedure as in Example 1. However, a Kapton film (12.5 μm thickness) manufactured by DuPont was used for the insulating substrate, and a through hole having a diameter of 0.4 μm was used for connection on both sides. The thickness of the resist pattern was 100 μm, the width was 80 μm, the width of the region where the underlying conductor layer 3 was exposed was 80 μm, and the thickness of the center conductor 41 was 95 μm. The arrangement pitch of the formed coil conductor filaments was 160 μm, the thickness was 160 μm, and the distance between the coil conductors was 5 μm on average.

Comparative Example 3 A planar coil having a coil pattern similar to that of Example 2 was produced in the same manner as in Comparative Example 2. The thickness of the coil conductor wire is 160 μm, and the distance between the coil conductor wires is 2 on average.
It was 0 μm. The cross section was mushroom-shaped, and the cross section of the head had a very large curvature at the corner and was almost circular. When the DC resistance was measured, the coil of Comparative Example 3 was 30% less than the coil of Example 2.
it was high. The DC resistance was increased because the space factor was low.

Example 3 A thickness of 0.3 mm made of vinylbenzyl and a plane dimension of 1.6
3 (A) to FIG. 3 on an insulating substrate 2 of mm × 0.8 mm.
As shown in (C), a coil pattern was formed using a build-up method. First, as shown in FIG.
The first-layer coil conductor wire 4 was formed on the insulating substrate 2. Next, after forming the interlayer insulating layer 12 as shown in FIG. 3B, as shown in FIG.
A second-layer coil conductor wire 4 was formed thereon. The thickness of the interlayer insulating layer 12, that is, the distance between the first-layer coil conductor and the second-layer coil conductor was 50 μm.

In forming the first and second layers of coil conductor strips, the thickness of the resist pattern is 80 μm, the width of the region where the underlying conductor layer is exposed is 60 μm, and the thickness of the center conductor is 70 μm. And the other conditions were the same as in Example 1.
The same as above. The formed coil conductor wire has a width of 120
μm and a thickness of 100 μm. In other words, the growth anisotropy when forming the surface conductor layer was 1, and the surface conductor layer was adhered on the center conductor with a uniform thickness. The reason why the surface conductor layer is isotropically grown is that the distance between adjacent coil conductor wires is extremely large. In this coil, the surface conductor layer grew isotropically, but since the center conductor was provided, the aspect ratio of the coil conductor filament was as large as 1.2, which was larger than the aspect ratio (1.17) of the center conductor. Was. The circumference of the coil conductor wire is about 440 μm.

This coil had an inductance value of 5.3 nH at 1 GHz and a Q value of 106.

Comparative Example 4 A coil was produced in the same manner as in Example 3 except that the surface conductor layer was not formed. In this coil, since the center conductor in the third embodiment is used as the coil conductor wire,
The aspect ratio of the coil conductor wire was 1.17, and the circumferential length of the coil conductor wire was about 260 μm, all of which were smaller than the coil of Example 3.

This coil had an inductance value of 5.3 nH at 1 GHz and a Q value of 80.

A comparison between Example 3 and Comparative Example 4 shows that the present invention improves the Q value by about 30%. The improvement of the Q value is due to the improvement of the aspect ratio of the coil conductor wire and the improvement of the perimeter.

[Brief description of the drawings]

FIGS. 1A to 1E are cross-sectional views showing a flow of steps in an example of a method for manufacturing a planar coil of the present invention.

FIGS. 2A to 2C are cross-sectional views of a planar coil.

FIGS. 3A to 3C are plan views illustrating a manufacturing process of a planar coil.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 2 Insulating substrate 3 Base conductor layer 4 Coil conductor wire 41 Central conductor 42 Surface conductor layer 11 Resist pattern 12 Interlayer insulation layer

Claims (10)

[Claims] An underlying conductor layer forming step of forming an underlying conductor layer on an insulating substrate; a resist pattern forming step of forming a resist pattern such that a surface of the underlying conductor layer is spirally exposed; A first electroplating step of forming a center conductor having a substantially rectangular cross section by performing electroplating, a resist pattern stripping step of stripping the resist pattern, and a surface conductor by electroplating using the center conductor as a base. A method for producing a planar coil, comprising a second electroplating step of forming a layer and completing a coil conductor wire comprising the central conductor and the surface conductor layer covering the central conductor. 2. The method of manufacturing a planar coil according to claim 1, further comprising an etching step of removing an underlying conductor layer exposed by stripping the resist pattern by etching between the resist pattern stripping step and the second electroplating step. . 3. The method of manufacturing a planar coil according to claim 2, wherein the thickness of the center conductor is at least five times the thickness of the underlying conductor layer. 4. The method of manufacturing a planar coil according to claim 1, wherein the underlying conductor layer is formed in a spiral shape in the underlying conductor layer forming step. 5. The method for manufacturing a planar coil according to claim 1, wherein the thickness of the center conductor is at least one third of the thickness of the coil conductor wire. 6. In a cross section of the resist pattern,
The method for manufacturing a planar coil according to any one of claims 1 to 5, wherein the width is not less than half the thickness. 7. The method for manufacturing a flat coil according to claim 1, wherein a flat coil having a region where the space factor of the coil conductor wire is 70% or more exists. 8. A planar coil manufactured by the method according to claim 1. 9. The planar coil according to claim 8, wherein an oxide layer exists at an interface between the center conductor and the surface conductor layer. 10. A transformer formed by laminating a plurality of the planar coils according to claim 8 or 9.