JP2009117546A - Planar coil, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-inductance planar coil whose DC resistance is reduced by reducing a conductor width in a range from an outermost peripheral portion to an innermost peripheral portion, and to provide a manufacturing method thereof. <P>SOLUTION: The planar coil has a conductor 3 spirally shaped by electrolytic copper plating. The conductor 3 has a conductor width reduced in a range from the spirally shaped outermost peripheral portion to the innermost peripheral portion so that a conductor with Wa of the spirally-shaped outermost peripheral portion of the planar coil connected to an external terminal is maximum, the conductor width is gradually smaller as tending to the center and a conductor width Wb of the innermost peripheral portion is minimum. The ratio of the conductor width Wb of the innermost peripheral portion to the conductor width Wa of the outermost peripheral portion is 0.01 or more and less than 0.5. The conductor 3 is embedded into an insulator. Besides, magnetic plating treatment is applied to the surface layer of the conductor 3 to improve an inductance value for the coil. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a planar coil and a method of manufacturing the same, and more particularly to a planar coil made of a conductor formed by electrolytic copper plating embedded in an insulator, and more particularly, the innermost portion than the outermost portion of the planar coil. The present invention relates to a planar coil having a high inductance and a method for manufacturing the same, by reducing the direct current resistance of the coil by reducing the conductor width toward.

  In recent years, in digital home appliances and mobile phones such as digital still cameras and digital video cameras, there has been an increasing demand for further miniaturization, thinning, and power saving along with higher functionality and higher quality. To that end, it is necessary to reduce the size and thickness of inductors, which are key electronic components, and to realize low resistance.

  As patent documents describing the prior art relating to the planar coil of the present invention, there are Patent Documents 1 and 2, for example. Patent Document 1 discloses a core structure in which a ferrite core having an outer leg and a ferrite core having a center leg are butted on the outer leg, and both surfaces of an insulating resin film having a through hole in the center. A spiral coil conductor is formed on the coil substrate, and a coil substrate in which both sides of the spiral coil conductor are connected to each other via a through-hole portion and an external electrode connected to the coil conductor, and between the spiral conductor portions of the coil conductor The surface mount type coil element having a high inductance and a low resistance coil conductor is realized.

  In addition, the device described in Patent Document 2 is formed by forming a relatively thin first coil electrically connected to at least one place on the first insulating layer, and then forming an organic layer between the coil conductors. Alternatively, a second insulating layer made of an inorganic material is formed, and a second coil having a relatively large thickness is formed on the second insulating layer by plating to insulate the coils with an organic or inorganic insulating film. Thus, a high-density and low-resistance coil is realized.

Japanese Patent Laid-Open No. 2005-210010 JP-A-6-176318

  Generally known winding coils cannot be thinly wound, and have a demerit that the winding position is not constant, making it difficult to apply as a mass-produced product. Also, in the process of patterning copper-clad substrates by the etching method, the gap between conductors cannot be narrowed with thick film copper foil due to under-etching, and in order to narrow the gap between conductors It was difficult to reduce the resistance because the foil had to be thin.

  Therefore, the plating method is optimal for narrowing the gap between conductors to increase the occupancy rate and to realize low resistance. For example, a method for realizing a low resistance coil by forming coil conductors on both surfaces of an insulating resin film and setting a gap between the coil conductors to 20 μm or less has been proposed (see Patent Document 1 described above). .

  Further, after the step of forming the first coil conductor, a method is proposed in which an insulating layer is formed in the gap between the first coil conductors, and the second coil conductor layer is formed by plating using this insulating layer as a mask. (See Patent Document 2 mentioned above).

  However, in the method described in Patent Document 1, it is difficult to apply the mass production technique to the gap between conductors of 1 μm or less because the quality is not stable. Even if it is narrowed, there is a problem that the effect of reducing the resistance cannot be obtained.

  Further, in the method described in Patent Document 2, an insulating layer mask must be newly formed after the first plating for reducing resistance, and then the second plating must be performed. However, there is a problem that the manufacturing cost increases.

  The present invention has been made in view of such problems, and its purpose is to reduce the DC resistance of the coil by reducing the conductor width from the coil outer periphery to the inner periphery, An object of the present invention is to provide a high-inductance planar coil and a method for manufacturing the same.

  The present invention has been made in order to achieve such an object. The invention according to claim 1 is a planar coil including a conductor formed in a spiral shape by electrolytic copper plating, wherein the conductor includes the conductor. The conductor width is reduced from the outermost part of the spiral shape toward the innermost part.

  The invention according to claim 2 is the invention according to claim 1, wherein the ratio of the conductor width of the innermost part to the conductor width of the outermost part is 0.01 or more and less than 0.5. It is characterized by.

  The invention according to claim 3 is the invention according to claim 1 or 2, characterized in that the conductor width continuously decreases from the outermost part toward the innermost part. To do.

  The invention according to claim 4 is the invention according to claim 1 or 2, characterized in that the conductor width is gradually reduced from the outermost portion toward the innermost portion. To do.

  The invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the conductor is embedded in an insulator.

  The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the conductor is subjected to a magnetic plating treatment.

  The invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein the spiral shape is circular or rectangular.

  The invention according to claim 8 is a method of manufacturing a planar coil provided with an electrolytic copper plating layer formed in a spiral shape by electrolytic copper plating, and a step of coating a photosensitive photoresist on the surface of the substrate; A step of exposing the photosensitive photoresist using a photomask having a resist pattern shaped so as to reduce the conductor width from the outermost portion to the innermost portion of the conductor forming portion; And a step of forming the electrolytic copper plating layer in the opening of the pattern.

  The invention according to claim 9 is the invention according to claim 8, wherein the ratio of the conductor width of the innermost part to the conductor width of the outermost part is 0.01 or more and less than 0.5. It is characterized by forming in.

  Further, the invention according to claim 10 is the invention according to claim 8 or 9, wherein the conductor width is formed so as to be continuously reduced from the outermost part toward the innermost part. Features.

  The invention according to claim 11 is the invention according to claim 8 or 9, wherein the conductor width is formed so as to decrease stepwise from the outermost part toward the innermost part. Features.

  The invention according to claim 12 is the invention according to any one of claims 8 to 11, further comprising a step of embedding the electrolytic copper plating layer in an insulator.

  The invention according to claim 13 is the invention according to any one of claims 8 to 12, further comprising a step of magnetic plating the surface of the electrolytic copper plating layer.

  The invention according to claim 14 is characterized in that, in the invention according to any one of claims 8 to 13, the spiral shape is formed to be a circle or a rectangle.

  According to the present invention, the resistance of the coil is proportional to the wire length of the conductor and is inversely proportional to the conductor cross-sectional area with the conductor volume ratio being constant, so that the resistance can be reduced as compared with a coil having a constant conductor width. . Moreover, it is possible to realize high inductance by magnetic plating.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<Embodiment 1>
FIG. 1 is a plan view showing a conductor portion for explaining a first embodiment of a planar coil according to the present invention, in which reference numeral 3 denotes a conductor, and 5a and 5b denote through holes. Wa represents the outermost conductor width, Wb represents the innermost conductor width, and a relationship of Wa> Wb is established.

  The planar coil of the present invention is a planar coil provided with a conductor 3 formed in a spiral shape by electrolytic copper plating, and the conductor 3 has a conductor width from the outermost peripheral portion of the spiral shape toward the innermost peripheral portion. It is getting smaller. That is, the conductor width Wa at the outermost peripheral portion of the spiral-shaped planar coil connected to the external terminal is maximum, the conductor width gradually decreases toward the center, and the conductor width Wb at the innermost peripheral portion is minimum. is there. Moreover, it is connected to the external terminal through the through hole 3b in the innermost periphery. In addition, since it forms with the manufacturing method of the planar coil mentioned later, conductor height is constant.

  The ratio of the innermost conductor width Wb to the outermost conductor width Wa is 0.01 or more and less than 0.5. The conductor width is continuously reduced from the outermost part toward the innermost part.

  The conductor 3 is configured to be embedded in an insulator. The conductor 3 can also be subjected to magnetic plating. In addition, the planar coil shown in FIG. 1 shows a circular shape as a spiral shape, but other than this, as shown in FIG.

  Table 1 shows measured values of coil resistance and inductance of a specific example in the first embodiment.

In the conventional planar coil shown in the comparative example, the conductor width is constant from the outermost periphery to the innermost periphery (innermost / outermost periphery = 1.00), and the linear resistance value of the planar coil at this time is 0. 20Ω. On the other hand, Example 1 is the case where the innermost circumference / outermost circumference = 0.07, the DC resistance value is 0.18Ω, and Example 2 is the case where the innermost circumference / outermost circumference = 0.14. The DC resistance value is 0.17Ω, and in Example 3 the innermost circumference / outermost circumference = 0.25, the DC resistance value is 0.164Ω, and the DC resistance values are both reduced.

  2 and 3 are diagrams for explaining the reason why the resistance value of the present invention is lower than that of the prior art. FIG. 2 is a diagram showing the coil pitch and the resistance by turn from the outermost peripheral portion, and FIG. 3 is a diagram showing the coil pitch and the cumulative coil resistance from the outermost peripheral portion.

  Here, in the comparative example, the conductor width is constant, and in the embodiment, the conductor width Wa is large at the outermost peripheral portion and the conductor width Wb is small at the innermost peripheral portion. In the comparative example in which the conductor width is constant, the turn-by-turn resistance is reduced according to the cumulative coil pitch from the outermost periphery, that is, the distance from the outermost periphery to the innermost periphery. This is because the outermost part has a large circumference and the innermost part has a small circumference, and the resistance is reduced in proportion to the total coil pitch. That is, the resistance at the outermost periphery is increased.

  On the other hand, in this embodiment, since the conductor width Wa at the outermost peripheral portion is large, the resistance is smaller than that in the comparative example. In addition, since the conductor width Wb of the innermost peripheral portion is small, the resistance is larger than that of the comparative example, but since the circumference is small, the resistance value is smaller than the decrease in resistance due to the decrease in the conductor width, The effect of reducing the conductor width is small.

  As shown in FIG. 2, the resistance value as a planar coil is the cumulative resistance value of each turn, and as shown in FIG. 3, this is the cumulative coil resistance from the outermost periphery, that is, the resistance of the planar coil. As shown in the table, since the resistance of the turn at the outermost periphery is low, the cumulative resistance can be greatly reduced compared to the comparative example. The conductor width decreases and the resistance increases as it goes to the innermost peripheral portion, but since the circumference length is small, there is little influence of increasing the resistance, and the resistance value as a whole is smaller than that of the comparative example.

  4A (a) to (f) and FIGS. 4B (a) to (e) are process diagrams for explaining the manufacturing method of the planar coil according to the first embodiment of the present invention. 4A and 4B are divided for convenience in drawing, and the steps are continuous.

  In the figure, reference numeral 1 is a substrate, 2 is a resist pattern, 3 is an electrolytic copper plating layer (conductor), 4 is an insulator, 5 is a through hole, 6 is a metal catalyst, 7 is an overcoat layer, 8 is an insulating layer, 9 is A metal underlayer, 10 is an electroplating layer, and 11 is a resist pattern.

  First, in FIG. 4A (a), a photosensitive photoresist is coated on the surface of the substrate 1 having, for example, copper or aluminum as a base layer. The substrate 1 can be simultaneously formed with patterns on both sides by welding the peripheral portion with ultrasonic waves or bonding them together with an adhesive.

  As the photosensitive photoresist, for example, a negative type liquid resist or a positive type liquid resist can be used. The substrate 1 is immersed in the liquid resist, or the liquid resist is applied to the surface of the substrate 1 by spin coating. The Alternatively, a dry film resist having a photosensitive photoresist applied on the film surface is laminated on the substrate 1 and applied to the surface.

  Next, the photosensitive photoresist is exposed by irradiating ultraviolet rays through a photomask. As the photomask at this time, a photomask having a glass or PET film as a base material and Cr or Ag salt as a pattern and an emulsion coated on the surface is generally used. Further, it is possible to draw a fine pattern by directly irradiating the resist with ultraviolet rays using a laser drawing apparatus. At this time, in order to obtain a desired resistance value, the opening width of the photosensitive photoresist is appropriately designed so as to narrow the conductor width from the outermost peripheral portion to the innermost peripheral portion of the planar coil. That is, the photosensitive photoresist is exposed using a photomask having a resist pattern 2 shaped so as to reduce the conductor width from the outermost peripheral portion to the innermost peripheral portion of the conductor forming portion.

  The exposed substrate 1 is developed to form a resist pattern 2 in which a conductor forming portion of the planar coil is opened in a pattern. The developing solution is a weakly alkaline aqueous solution such as a 1-5% sodium carbonate solution or a 3-15% triethanolamine aqueous solution, but an organic solvent can also be used. The development is carried out by immersing and swinging the substrate or passing through a shower device.

Next, as shown in FIG. 4A (b), an electrolytic copper plating layer 3 is deposited on the opening of the resist pattern 2 by an electrolytic copper plating method to form a planar coil wiring. The electrolytic copper plating solution is processed using a chemical solution containing general copper sulfate or a chemical solution containing copper pyrophosphate. For example, the composition of the copper sulfate plating solution is 30 to 200 g / l (liter) for CuSO ₄ .5H ₂ O, 100 to 200 g / l (liter) for H ₂ SO ₄ , and 30 to 80 mg / l (liter) for Cl ^−. ), A small amount of organic sulfur compound (for example, bis (3-propanesulfonesan) disulfide) of about 0 to 10 ppm, an organic nitrogen compound (for example, quaternary polyamine having a molecular weight of about 1,000), a surfactant (for example, polypropylene glycol, A mixture containing polyethylene glycol). Preferably, CuSO ₄ .5H ₂ O is used in a range of 100 to 180 g / l (liter), H ₂ SO ₄ is used in a range of 120 to 200 g / l (liter), and Cl ⁻ is used in a range of 40 to 70 mg / l (liter). Good.

Next, as shown in FIG. 4A (c), the substrate 1 is separated and bonded so that the insulator 4 is sandwiched between the substrates having a plurality of coil patterns. As this insulator 4, a glass cloth coated with an adhesive resin having a functional group such as epoxy, acrylate, phenol or the like, a coating of these adhesives on the surface of an aramid film, or these adhesives on the surface of an imide film Or imide varnish coated. These insulators 4 are bonded under high temperature and high pressure, for example, in an environment of 150 ° C. or higher and 5 kgf / cm ² or higher.

  Next, as shown in FIG. 4A (d), the underlayer is removed by etching, and a metal underlayer 9 is bonded (laminated) to the upper and lower layers via an insulator 8.

  Next, as shown in FIG. 4A (e), through-holes 5 are formed in the connection portions on the upper and lower layers of the pattern. The through-hole 5 can use a mechanical device such as a drill, a punch, or a laser, but it is preferable to select a method according to the laminated material.

  Next, as shown in FIG. 4A (f), the substrate 1 is immersed in a chemical solution containing a metal catalyst such as a palladium salt, and the metal catalyst 6 is adsorbed on the inner wall of the through hole 5.

  Next, as shown in FIG. 4B (a), electrolytic copper plating is performed to form an electrolytic copper plating layer 10. An electrolytic plating method combined with electroless plating that does not require electricity as copper plating can also be used. Although the thickness can be arbitrarily adjusted as copper plating, it is preferable to form a thickness of 5 μm or more in consideration of the reliability of the through hole 5.

  Next, as shown in FIG. 4B (b), by using a lithography method using a photoresist on the formed electrolytic copper plating layer 10, for example, the resist pattern 11 is left in a necessary place such as a through hole. By removing the electrolytic copper plating layer 10 by etching, electrical connection between a plurality of conductor layers is obtained (FIG. 4B (c)). For the etching of the electrolytic copper plating layer 10, an aqueous solution containing iron chloride, copper chloride, sulfuric acid / hydrogen peroxide solution, persulfates, or the like can be used, and treatment is performed by appropriately selecting a chemical solution according to the etching rate.

  After stripping the resist pattern 11 (FIG. 4B (d)), as shown in FIG. 4B (e), an overcoat layer 7 is printed and covered at an arbitrary position for electrical insulation. As this overcoat layer 7, a thermosetting resin that is cured by heat, a photocurable resin, a photo solder resist that is cured in a pattern by light, or the like can be used. The terminal part of the wiring of such a planar coil is connected to a solder material containing at least one metal of Sn, Ag, Cu, Ni, Zn, Sb, and In and other electronic parts such as Au / Ni and reliability of connection. It is possible to obtain a planar coil with low resistance by processing with a material having high properties.

<Embodiment 2>
5A (a) to 5 (d) and FIGS. 5B (a) to 5 (c) are process diagrams for explaining the manufacturing method of the planar coil according to the second embodiment of the present invention. 5A and 5B are separated for convenience in drawing, and the steps are continuous.

5A (a) to 5 (c) are the same steps as FIGS. 4A (a) to (c).
Next, as shown in FIG. 5A (d), through-holes 5 are formed in the connection portions on the upper and lower layers of the pattern. The through-hole 5 can use a mechanical device such as a drill, a punch, or a laser, but it is preferable to select a method according to the laminated material.

  Next, as shown in FIG. 5B (a), the substrate is immersed in a chemical solution containing a metal catalyst such as a palladium salt to adsorb the metal catalyst 6 on the inner wall of the through hole, and then the underlying layer is removed by etching.

  Next, as shown in FIG. 5B (b), electrolytic copper plating is performed again to form an electrolytic pattern copper plating layer 12. This step has an advantage that the resistance can be further reduced in a short process because the resist pattern 2 formed in FIG. 5A (a) is used as it is and the electrical connection of the through hole 5 is also performed at the same time.

  Next, as shown in FIG. 5B (c), an overcoat layer 7 is printed and covered at an arbitrary position for electrical insulation. As this overcoat layer 7, a thermosetting resin that is cured by heat, a photocurable resin, a photo solder resist that is cured in a pattern by light, or the like can be used. The terminal part of the wiring of such a planar coil is connected to a solder material containing at least one metal of Sn, Ag, Cu, Ni, Zn, Sb, and In and other electronic parts such as Au / Ni and reliability of connection. It is possible to obtain a planar coil with low resistance by processing with a material having high properties.

<Embodiment 3>
FIGS. 6A (a) to 6 (e) and FIGS. 6B (a) to 6 (d) are process diagrams for explaining the manufacturing method of the planar coil according to the third embodiment of the present invention. FIG. 6A and FIG. 6B are separated for convenience in drawing, and the steps are continuous.

6A (a) to 6 (b) are the same steps as FIGS. 5A (a) to 5 (b).
Next, as shown in FIG. 6A (c), an electrolytic magnetic plating layer 13 of a metal material having magnetism including at least one of Fe, Ni, or Co is formed on the surface of the electrolytic copper plating layer 3. . For example, a magnetic plating solution made of ferrous sulfate, nickel chloride, nickel sulfate, boric acid, sodium chloride, and saccharin sodium is used as the magnetic plating solution, and ferrous sulfate heptahydrate is 1 to 10 g / l (liter), nickel chloride hexahydrate 30-100 g / l (liter), nickel sulfate hexahydrate 10-50 g / l (liter), boric acid 10-50 g / l (liter), chloride Thorium is treated within a range of 10 to 50 g / l (liter) and sodium saccharin within a range of 0.5 to 5 g / l (liter).

Next, as shown in FIG. 6A (d), the substrate 1 is separated and bonded so that the insulator 4 is sandwiched between the substrates having a plurality of coil patterns. As this insulator 4, a glass cloth coated with an adhesive resin having a functional group such as epoxy, acrylate, phenol or the like, a coating of these adhesives on the surface of an aramid film, or these adhesives on the surface of an imide film Or imide varnish coated. These insulators are bonded under high temperature and high pressure, for example, in an environment of 150 ° C. or higher and 5 kgf / cm ² or higher.

  Further, the through hole 5 is formed in the connection portion of the pattern upper and lower layers. The through-hole 5 can use a mechanical device such as a drill, a punch, or a laser, but it is preferable to select a method according to the laminated material.

  Next, as shown in FIG. 6A (e), the substrate is immersed in a chemical solution containing a metal catalyst such as a palladium salt, and the metal catalyst 6 is adsorbed on the inner wall of the through hole 5.

  Next, as shown in FIG. 6B (a), after the metal catalyst 6 is adsorbed on the inner wall of the through hole 5, the underlying layer is removed by etching.

  Next, as shown in FIG. 6B (b), electrolytic copper plating is performed again to form an electrolytic pattern copper plating layer 12. This step has an advantage that the resistance can be further reduced in a short process because the resist pattern 2 formed in FIG. 5A (a) is used as it is and the electrical connection of the through hole 5 is also performed at the same time.

  Next, as shown in FIG. 6B (c), the electrolytic magnetic plating layer 14 is formed again on the surface of the electrolytic copper plating layer 12. At this time, the electrolytic magnetic plating layer 14 is also formed on the surface of the through hole 5.

  Next, as shown in FIG. 6B (d), an overcoat layer 7 is printed and covered at an arbitrary position for electrical insulation. As the overcoat layer 7, a thermosetting resin that is cured by heat, a photocurable resin, a photo solder resist that is cured in a pattern by light, or the like can be used. The terminal part of the wiring of such a planar coil is connected to a solder material containing at least one metal of Sn, Ag, Cu, Ni, Zn, Sb, and In and other electronic parts such as Au / Ni and reliability of connection. It is possible to obtain a planar coil having a low resistance and a high inductance by processing with a material having high properties.

  Table 2 shows measured values of coil resistance and inductance of a specific example in the third embodiment.

  In the conventional planar coil shown in the comparative example, the magnetic plating thickness was 0 and the inductance was 9.50 μH, but the inductance when the thickness was 4 μm in Example 4, 6 μm in Example 5, and 8 μm in Example 6 was used. It can be seen that Example 4 is 12.30 μH, Example 5 is 13.40 H, and Example 6 is 14.50 μH. That is, a planar coil having a higher inductance than that of a conventional planar coil can be obtained.

It is a top view which shows the conductor part for demonstrating Embodiment 1 of the planar coil which concerns on this invention. It is a figure for demonstrating the reason that resistance value falls compared with the former in this invention, and is a figure which shows resistance according to the turn from a coil pitch and an outermost periphery part. It is a figure for demonstrating the reason that resistance value falls compared with the past in the present invention, and is a figure showing coil pitch and coil resistance accumulation from the outermost part. It is process drawing for demonstrating the manufacturing method of Embodiment 1 of the planar coil which concerns on this invention. It is process drawing for demonstrating the manufacturing method of Embodiment 1 of the planar coil which concerns on this invention, and is a figure which shows the process following FIG. 4A. It is process drawing for demonstrating the manufacturing method of Embodiment 2 of the planar coil which concerns on this invention. It is process drawing for demonstrating the manufacturing method of Embodiment 2 of the planar coil which concerns on this invention, and is a figure which shows the process following FIG. 5A. It is process drawing for demonstrating the manufacturing method of Embodiment 3 of the planar coil which concerns on this invention. It is process drawing for demonstrating the manufacturing method of Embodiment 3 of the planar coil which concerns on this invention, and is a figure which shows the process following FIG. 6A. It is a top view which shows the conductor part for demonstrating other embodiment of the planar coil which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2,11 Resist pattern 3,10 Electrolytic copper plating layer 4 Insulator 5 Through hole 5a, 5b Through hole 6 Metal catalyst 7 Overcoat layer 8 Insulating layer 9 Metal base layer 12 Electrolytic pattern copper plating layers 13, 14 Electromagnetic Body plating layer Wa The outermost conductor width Wb The innermost conductor width

Claims (14)

  A planar coil comprising a conductor formed in a spiral shape by electrolytic copper plating, wherein the conductor has a conductor width that decreases from the outermost portion of the spiral shape toward the innermost portion. .   2. The planar coil according to claim 1, wherein a ratio of a conductor width of the innermost portion to a conductor width of the outermost portion is 0.01 or more and less than 0.5.   The planar coil according to claim 1 or 2, wherein the conductor width continuously decreases from the outermost portion toward the innermost portion.   The planar coil according to claim 1, wherein the conductor width is gradually reduced from the outermost portion toward the innermost portion.   The planar coil according to claim 1, wherein the conductor is embedded in an insulator.   The planar coil according to claim 1, wherein the conductor is subjected to magnetic plating.   The planar coil according to claim 1, wherein the spiral shape is circular or rectangular. In the manufacturing method of the planar coil provided with the electrolytic copper plating layer formed in a spiral shape by electrolytic copper plating,
Coating a photosensitive photoresist on the surface of the substrate;
Next, the step of exposing the photosensitive photoresist using a photomask having a resist pattern shaped so as to reduce the conductor width from the outermost portion of the conductor forming portion toward the innermost portion;
Next, a method of forming the electrolytic copper plating layer in the opening of the resist pattern.   9. The method for manufacturing a planar coil according to claim 8, wherein a ratio of the conductor width of the innermost part to the conductor width of the outermost part is 0.01 or more and less than 0.5.   The method for manufacturing a planar coil according to claim 8 or 9, wherein the conductor width is formed so as to continuously decrease from the outermost portion toward the innermost portion.   The method for manufacturing a planar coil according to claim 8 or 9, wherein the conductor width is formed so as to decrease stepwise from the outermost portion toward the innermost portion.   The method for producing a planar coil according to claim 8, further comprising a step of embedding the electrolytic copper plating layer in an insulator.   The method for producing a planar coil according to any one of claims 8 to 12, further comprising a step of magnetically plating the surface of the electrolytic copper plating layer.   The planar coil manufacturing method according to any one of claims 8 to 13, wherein the spiral shape is circular or rectangular.

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