JP2017216407A - Printed-wiring board and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed-wiring board capable of improving a flux density of a planar coil at a relatively low cost, and a method for manufacturing the same.SOLUTION: A printed-wiring board according to one embodiment includes a base film with insulation properties, and a pattern layer laminated on at least one surface side of the base film. The pattern layer includes a spiral coil pattern and a coil core pattern having magnetism and disposed inside the innermost periphery of the coil pattern. A method for manufacturing the printed-wiring board according to one embodiment includes the steps of: forming an inverted shape resist pattern of the pattern layer including the spiral coil pattern on one surface of a conductive ground layer; forming a coil pattern by plating onto the conductive ground layer of an opening of the resist pattern; removing the resist pattern and the conductive ground layer at the bottom of the resist pattern; and forming a coil core pattern having magnetism inside the innermost periphery of the coil pattern.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a printed wiring board and a manufacturing method thereof.

  With the spread of RFID (Radio Frequency IDentification) systems that use Near Field Communication (NFC) technology and non-contact IC cards, wireless (non-contact) power supply devices that use electromagnetic induction have become widespread. I am doing. In this wireless power feeding device, a power feeding coil and a power receiving coil are arranged so as to face each other, and a current is generated in the power receiving coil by a magnetic flux generated by passing a current through the power feeding coil.

  In addition, with the recent miniaturization and thinning of portable devices, there is an increasing demand for miniaturization and thinning of the coil elements provided in the wireless power supply apparatus. Based on such a requirement, for example, a planar coil element has been devised in which a planar coil having a spiral shape in a plan view is disposed on the surface of a magnetic material sheet (see JP 2006-42519 A).

JP 2006-42519 A

  Such antennas for portable devices are required to be able to realize small and efficient power transmission. However, if the number of turns of the coil is simply increased in order to improve the magnetic flux density of the coil without changing the power, the manufacturing becomes difficult due to the higher density of the wiring and the higher aspect ratio of the cross section, resulting in an increase in cost.

  The present invention has been made based on the above-described circumstances, and an object of the present invention is to provide a printed wiring board capable of improving the magnetic flux density of a planar coil at a relatively low cost and a method for manufacturing the same.

  A printed wiring board according to an aspect of the present invention, which has been made to solve the above problems, includes a base film having insulating properties, and a pattern layer laminated on at least one surface side of the base film, and the pattern The layer includes a conductive spiral coil pattern and a coil core pattern that is disposed inside the innermost periphery of the coil pattern and has magnetism.

  Moreover, the manufacturing method of the printed wiring board which concerns on 1 aspect of this invention made | formed in order to solve the said subject, The base film which has insulation, The pattern layer laminated | stacked on the at least one surface side of this base film, A method of manufacturing a printed wiring board comprising: a conductive underlayer laminating step of laminating a conductive underlayer on one side of the base film; and a photoresist film on one side of the conductive underlayer A photoresist film laminating step for laminating, a resist pattern forming step for forming a resist pattern having an inverted shape of a pattern layer including a spiral coil pattern by exposure and development to the photoresist film, and an opening of the resist pattern A coil pattern forming step of forming the coil pattern by plating on the conductive underlayer of the resist, and the resist pattern And a conductive underlying layer removing step of removing the conductive underlayer of the bottom portion, and a coil core pattern forming step of forming a coil core pattern having magnetism inside the innermost periphery of the coil pattern.

  The printed wiring board and the manufacturing method thereof of the present invention can improve the magnetic flux density of the planar coil at a relatively low cost.

FIG. 1 is a schematic plan view of a printed wiring board according to an aspect of the present invention as viewed from the front side. FIG. 2A is a schematic cross-sectional view showing one step in the method for producing a printed wiring board of one embodiment of the present invention. FIG. 2B is a schematic cross-sectional view showing one step in the method for producing a printed wiring board of one embodiment of the present invention. FIG. 2C is a schematic cross-sectional view showing one step in the method for producing a printed wiring board of one embodiment of the present invention. FIG. 2D is a schematic cross-sectional view showing one step in the method for producing a printed wiring board of one embodiment of the present invention. FIG. 3 is a schematic cross-sectional view showing one step of a method for producing a printed wiring board in a mode different from FIGS. 2A to 2D of the present invention.

[Description of Embodiment of the Present Invention]
A printed wiring board according to one embodiment of the present invention includes an insulating base film and a pattern layer laminated on at least one surface side of the base film, and the pattern layer has a conductive spiral shape. It includes a coil pattern and a coil core pattern that is disposed inside the innermost periphery of the coil pattern and has magnetism.

  Since the printed wiring board has a coil core pattern having magnetism inside the spiral coil pattern, the coil core pattern can increase the magnetic flux density more than before without increasing the wiring density of the coil pattern. . That is, according to the printed wiring board, the magnetic flux density of the planar coil can be improved at a relatively low cost.

  The main component of the coil core pattern may be a metal, and the coil core pattern may be insulated from the coil pattern. In this way, by using metal as the magnetic material and insulating the coil core pattern from the coil pattern, the coil core pattern can be formed on the base film in the same procedure as the coil pattern, thus promoting the cost reduction effect. it can.

  Moreover, the manufacturing method of the printed wiring board which concerns on another one aspect | mode of this invention is a manufacturing of a printed wiring board provided with the base film which has insulation, and the pattern layer laminated | stacked on the at least one surface side of this base film. A method for laminating a conductive underlayer on one side of the base film, and a photoresist film laminating step for laminating a photoresist film on one side of the conductive underlayer And a resist pattern forming step for forming a resist pattern having an inverted shape of the pattern layer including the spiral coil pattern by exposing and developing the photoresist film, and on the conductive underlayer of the opening of the resist pattern. Coil pattern forming step of forming the coil pattern by plating, and the resist pattern and the conductive underlayer at the bottom thereof Comprising a conductive base layer removing step of removing, and a coil core pattern forming step of forming a coil core pattern having magnetism inside the innermost periphery of the coil pattern.

  According to the method for manufacturing a printed wiring board, a printed wiring board having a coil core pattern having magnetism inside a spiral coil pattern can be obtained. In this printed wiring board, the magnetic flux density can be increased by the coil core pattern without increasing the wiring density of the coil pattern. That is, according to the method for manufacturing a printed wiring board, the magnetic flux density of the planar coil can be improved at a relatively low cost.

  The coil core metal in which the resist pattern formed in the resist pattern forming step includes a reversal shape of the coil core pattern, and the coil core pattern forming step forms a coil core metal pattern by plating the opening of the resist pattern. It is good to have a pattern formation process and the magnetization process of magnetizing the said metal pattern for coil cores by heat processing. By forming the coil core pattern by such a process, the coil core pattern can be formed on the base film in the same procedure as the coil pattern, so that the cost reduction effect can be promoted.

  The “spiral shape” is not limited to a strict spiral shape, and a plurality of arcs or a part of a plurality of polygons are arranged in multiple rows, and one end of an outer arc or a part of a polygon It is a concept including a shape in which one end of a part of an inner arc or polygon is connected by a straight line or a curve. The “main component” is a component having the largest content, for example, a component occupying 50% by mass or more in the material.

[Details of the embodiment of the present invention]
Hereinafter, an embodiment of a printed wiring board and a manufacturing method thereof according to the present invention will be described in detail with reference to the drawings. In the printed wiring board of the present embodiment, “front and back” means a direction in which the pattern layer lamination side is “front” and the opposite side of the pattern layer lamination side is “back” in the thickness direction of the printed wiring board. However, it does not mean the front and back of the printed wiring board in use.

[Printed wiring board]
The printed wiring board shown in FIG. 1 mainly includes an insulating base film 1 and a pattern layer 2 laminated on one surface side (front surface side) of the base film 1. The pattern layer 2 includes a spiral coil pattern 2a and a coil core pattern 2b that is disposed on the inner side of the innermost periphery of the coil pattern 2a and has magnetism. In addition, the printed wiring board includes a coverlay (not shown) laminated on the surfaces of the base film 1 and the pattern layer 2.

<Base film>
The base film 1 is a synthetic resin layer having electrical insulation. The base film 1 is also a base material for forming the pattern layer 2. The base film 1 may have flexibility. In this case, the printed wiring board is used as a flexible printed wiring board.

  The material of the base film 1 is not particularly limited as long as it has insulating properties, but a low dielectric constant synthetic resin film formed in a sheet shape can be employed. Examples of the main component of the synthetic resin film include polyimide, polyethylene terephthalate, liquid crystal polymer, and fluororesin.

  As a minimum of average thickness of base film 1, 5 micrometers is preferred and 10 micrometers is more preferred. Moreover, as an upper limit of the average thickness of the base film 1, 50 micrometers is preferable and 40 micrometers is more preferable. When the average thickness of the base film 1 is less than the above lower limit, the insulation strength of the base film 1 may be insufficient. On the other hand, when the average thickness of the base film 1 exceeds the upper limit, the printed wiring board may be unnecessarily thick.

<Pattern layer>
The pattern layer 2 is a layer made of a conductive material and is laminated on the surface of the base film 1. The pattern layer 2 mainly has the above-described coil pattern 2a and coil core pattern 2b. The pattern layer 2 may include a pattern such as a land portion other than the coil core pattern 2a and the core pattern 2b. In addition, the pattern layer 2 may be laminated | stacked directly on the surface of the base film 1, and may be laminated | stacked through an adhesive bond layer.

(Coil pattern)
The coil pattern 2a is spiral. The outer shape of the coil pattern 2a (the shape formed by the outermost wiring) is not particularly limited, and may be a rectangular shape such as a square shape or a rectangular shape, a circular shape such as a perfect circle shape or an elliptical shape.

  The material (main component) of the coil pattern 2a is not particularly limited as long as it has conductivity, but a material having a small electric resistance is preferable. The coil pattern 2a can be formed of, for example, copper, silver or the like. The coil pattern 2a may be plated with gold, silver, tin, nickel or the like.

  In addition, as shown in FIG. 1, the coil pattern 2a has a first connection terminal 2c disposed at the end of the innermost wiring of the spiral pattern and an end of the outermost wiring of the spiral pattern. And a second connection terminal 2d. These terminals are connected to other wirings and devices by conductors such as via holes and lead wires. Note that these terminals are not essential constituent elements, and can be omitted depending on the shape of the coil pattern 2a, the positional relationship with other wirings, and the like.

  The lower limit of the average thickness of the coil pattern 2a is preferably 0.1 μm, and more preferably 1 μm. Moreover, as an upper limit of the average thickness of the coil pattern 2a, 100 micrometers is preferable and 80 micrometers is more preferable. When the average thickness of the coil pattern 2a is less than the above lower limit, the internal resistance may increase and the loss may be excessive, and the strength may be insufficient to easily tear the coil pattern 2a. Moreover, when the average thickness of the coil pattern 2a exceeds the said upper limit, there exists a possibility that the said printed wiring board may become thick unnecessarily.

  As a minimum of the average width of wiring in coil pattern 2a, 0.03 mm is preferred and 0.2 mm is more preferred. Moreover, as an upper limit of the average width | variety of the wiring in the coil pattern 2a, 1.5 mm is preferable and 1.25 mm is more preferable. When the average width of the wiring in the coil pattern 2a is less than the above lower limit, the mechanical strength of the coil pattern 2a is insufficient, and there is a possibility of breaking. On the other hand, when the average width of the wiring in the coil pattern 2a exceeds the upper limit, the printed wiring board may be unnecessarily large. Note that the width of the wiring in the coil pattern 2a is preferably constant.

  Although it does not specifically limit as a space | interval between wiring in the coil pattern 2a, For example, it can be 0.02 mm or more and 4.5 mm or less.

(Coil core pattern)
As shown in FIG. 1, the coil core pattern 2b is a solid pattern disposed on the inner side of the innermost circumference of the coil pattern 2a.

  The coil core pattern 2b has magnetism. That is, the coil core pattern 2b includes a magnetic material. The magnetic material is not particularly limited as long as it has paramagnetism or ferromagnetism, and a metal, a metal compound, or the like can be used. By using the coil core pattern 2b containing metal as the main component, the coil core pattern 2b can be formed relatively easily as will be described later. As this metal, for example, nickel, iron, chromium or the like is used.

  The coil core pattern 2b may have electrical conductivity. However, if it has electrical conductivity, it is necessary to insulate it so as not to be electrically connected to the coil pattern 2a or other wiring.

  The planar shape of the coil core pattern 2b is not particularly limited as long as it can be formed in a region surrounded by the innermost wiring of the coil pattern 2a (hereinafter also referred to as “coil inner region”). From the viewpoint of promoting the improvement effect, it is preferable to increase the area as much as possible. That is, a shape in which the outer edge of the coil core pattern 2b is along the outer edge of the coil inner region is preferable. However, when the coil core pattern 2b has conductivity as described above, it is necessary to be separated from the coil pattern 2a. The coil core pattern 2b may be divided into a plurality of blocks.

  The lower limit of the average thickness of the coil core pattern 2b is preferably 0.1 μm, and more preferably 1 μm. Moreover, as an upper limit of the average thickness of the coil core pattern 2b, 100 micrometers is preferable and 80 micrometers is more preferable. When the average thickness of the coil core pattern 2b is less than the lower limit, the effect of improving the magnetic flux density may be insufficient. Moreover, when the average thickness of the coil core pattern 2b exceeds the upper limit, the printed wiring board may be unnecessarily thick.

  The lower limit of the occupied area ratio of the coil core pattern 2b in the coil inner region is preferably 50%, more preferably 80%, and more preferably 95%. In addition, although the upper limit of the said exclusive area ratio is 100%, when the coil core pattern 2b has electroconductivity, 99% is preferable and 98% is more preferable.

  When the coil core pattern 2b has conductivity, the lower limit of the minimum distance between the coil core pattern 2b and the coil pattern 2a in the coil inner region is preferably 0.1 μm, and more preferably 1 μm. If the minimum distance is smaller than the lower limit, the coil pattern 2a and the coil core pattern 2b may be electrically connected.

  The coil core pattern 2b may have a multilayer structure, or a part of the coil core pattern 2b may be a layer having no magnetism (for example, a copper foil layer).

<Coverlay>
The coverlay mainly protects the pattern layer 2 in the printed wiring board. This coverlay has a cover film and an adhesive layer.

(Cover film)
The cover film has an insulating property. Examples of the main component of the cover film include polyimide, epoxy resin, phenol resin, acrylic resin, polyester, thermoplastic polyimide, polyethylene terephthalate, fluororesin, and liquid crystal polymer. Among these, polyimide is preferable from the viewpoint of heat resistance, but the cover film preferably includes a high dielectric material as a main component. The cover film may contain a resin other than the main component, a weathering agent, an antistatic agent, and the like.

  Although it does not specifically limit as a minimum of the average thickness of a cover film, 3 micrometers is preferable and 10 micrometers is more preferable. The upper limit of the average thickness of the cover film is not particularly limited, but is preferably 500 μm, and more preferably 150 μm. When the average thickness of the cover film is less than the above lower limit, protection of the pattern layer 2 and the like may be insufficient, and insulation may be insufficient. On the other hand, when the average thickness of the cover film exceeds the upper limit, there is a risk that the protective effect of the pattern layer 2 and the like will be reduced.

(Adhesive layer)
Although it does not specifically limit as an adhesive agent which comprises the adhesive layer of a coverlay, The thing excellent in the softness | flexibility and heat resistance is preferable. Examples of the adhesive include various resin adhesives such as epoxy resin, polyimide, polyester, phenol resin, polyurethane, acrylic resin, melamine resin, and polyamideimide.

  The lower limit of the average thickness of the adhesive layer is preferably 5 μm and more preferably 10 μm. Moreover, as an upper limit of the average thickness of an adhesive layer, 50 micrometers is preferable and 40 micrometers is more preferable. When the average thickness of the adhesive layer is less than the above lower limit, the adhesive strength of the coverlay to the pattern layer 2 and the base film 1 may be insufficient. On the other hand, when the average thickness of the adhesive layer exceeds the upper limit, the printed wiring board may be unnecessarily thick.

[Method of manufacturing printed wiring board]
The printed wiring board manufacturing method includes a conductive underlayer laminating step of laminating a conductive underlayer on one side of a base film, and a photoresist laminating a photoresist film on one side of the conductive underlayer. A film patterning process, a resist pattern forming process for forming a resist pattern having an inverted shape of a pattern layer including a spiral coil pattern by exposing and developing the photoresist film, and a conductive pattern under the opening of the resist pattern. A coil pattern forming step for forming the coil pattern by plating on the ground layer, a conductive underlayer removing step for removing the resist pattern and the conductive underlayer at the bottom thereof, and an inner side of the innermost circumference of the coil pattern A coil core pattern forming step for forming a coil core pattern having magnetism on the base film and the pattern layer Mainly it includes a coverlay lamination step of laminating the rectangular cover lay on the side of. The method for manufacturing the printed wiring board uses a so-called semi-additive method.

<Conductive underlayer lamination process>
In the conductive underlayer laminating step, as shown in FIG. 2A, a conductive underlayer S that is the underlayer of the pattern layer is laminated on the surface side of the base film 1. As a material (main component) of the conductive base layer S, a known material such as copper, silver, nickel, palladium or the like can be used, and among these, copper is preferable. Moreover, a well-known method can be used for the lamination | stacking method of the electroconductive base layer S, For example, methods, such as electroless plating, sputtering, a vapor deposition method, application | coating of electroconductive fine particle dispersion liquid, are mentioned.

  The upper limit of the average thickness of the conductive base layer S is preferably 10 nm, and more preferably 5 nm. On the other hand, the lower limit of the average thickness is preferably 0.1 μm, and more preferably 0.2 μm. When the average thickness exceeds the upper limit, the conductive base layer S may not be sufficiently removed in a removal step described later. On the other hand, when the average thickness is less than the lower limit, it is difficult to form a coil pattern on the surface of the conductive base layer S.

<Photoresist film lamination process>
In the photoresist film stacking step, a photoresist film is stacked on the surface of the conductive base layer S. As a method of laminating the photoresist film, for example, a negative resist composition in which the polymer bond is strengthened by photosensitivity and the solubility in the developer is lowered, or the polymer bond is weakened by photosensitivity and developed. Examples include a method of applying a positive resist composition that increases the solubility in a liquid on the surface of the conductive base layer S, a method of laminating a dry film resist containing these compositions on the surface of the conductive base layer S, and the like. It is done.

<Resist pattern formation process>
In the resist pattern forming step, the photoresist film is exposed and developed to form a resist pattern having an inverted shape of the pattern layer including the coil pattern. Specifically, when a negative resist product is used, a mask is stacked on the photoresist film, and only a portion other than the existing portion of the pattern layer of the photoresist film is exposed. Thereafter, the resist pattern is formed by removing unexposed portions with an organic solvent or the like.

<Coil pattern formation process>
In the coil pattern forming step, the coil pattern 2a is formed by plating the conductive underlayer S on the opening of the resist pattern R formed as shown in FIG. 2B.

  Examples of the plating that fills the opening of the resist pattern R include electroplating or electroless plating, and electroplating is preferable. By using electroplating, the coil pattern 2a can be easily and reliably formed. The temperature, time, etc. at the time of plating can be appropriately changed according to the type of plating used.

<Conductive underlayer removal process>
In the conductive underlayer removing step, as shown in FIG. 2C, after the coil pattern 2a is formed, the resist pattern and the bottom conductive underlayer are removed.

  The resist pattern is removed by peeling the resist pattern from the conductive base layer. Specifically, the resist pattern R is expanded by the stripping solution by immersing the laminate having the resist pattern R, the coil pattern 2a, the conductive base layer S, and the base film 1 shown in FIG. 2B in the stripping solution. Thereby, a repulsive force is generated between the resist pattern and the conductive underlayer S, and the resist pattern is peeled off from the conductive underlayer S. As this stripper, a known one can be used.

  The conductive base layer at the bottom of the resist pattern is removed by etching using the coil pattern 2a as a mask for the conductive base layer exposed after the resist pattern is peeled off. Thereby, the wiring in the coil pattern 2a is electrically separated. For this etching, an etchant that erodes the metal forming the conductive underlayer is used. For this reason, although the coil pattern 2a can also be eroded by the etching solution, the influence of etching can be ignored because the entire thickness of the coil pattern 2a is sufficiently larger than that of the conductive underlayer.

  In addition, you may perform the secondary plating which thickens wiring after the said conductive base layer removal process.

<Coil core pattern formation process>
In the coil core pattern forming step, as shown in FIG. 2D, the coil core pattern 2b having magnetism is formed inside the innermost periphery of the coil pattern 2a.

  The method for forming the coil core pattern 2b is not particularly limited, and for example, a method of laminating a magnetic block forming the coil core pattern 2b on the coil inner region with an adhesive or the like can be used. However, from the viewpoint of productivity, it is preferable to use the following method.

  That is, the coil core pattern forming step includes a coil core metal pattern forming step of forming a coil core metal pattern by plating the resist pattern opening, and a magnetizing step of magnetizing the coil core metal pattern by heat treatment. It is good to have.

  Specifically, first, in the resist pattern forming step, as shown in FIG. 3, a resist pattern R including the inverted shape of the coil core pattern in addition to the inverted shape of the coil pattern is formed. Thereafter, before the conductive underlayer removing step, that is, before removing the resist pattern R, a coil core pattern forming step including the following steps is performed.

(Metal pattern forming process for coil core)
In the coil core metal pattern forming step, a metal pattern for the coil core having the same shape as the coil core pattern is formed by plating the reversal opening of the coil core pattern of the resist pattern R in FIG. This plating may be performed simultaneously with the plating in the coil pattern forming step or may be performed separately.

(Magnification process)
In the magnetizing step, the coil core pattern 2b is formed by magnetizing the metal pattern for the coil core obtained by the above-mentioned plating by heat treatment. After the coil core pattern 2b is formed, the conductive underlayer removing process is performed. Note that the magnetizing step may be performed after the conductive underlayer removing step.

  As a minimum of the above-mentioned heat treatment temperature, 100 ° C is preferred and 150 ° C is more preferred. On the other hand, the upper limit of the heat treatment temperature is preferably 350 ° C, more preferably 300 ° C. Moreover, as a minimum of the said heat processing time, 0.25 hour is preferable and 0.5 hour is more preferable. On the other hand, the upper limit of the heat treatment time is preferably 24 hours, and more preferably 12 hours. If the heat treatment temperature or time is smaller than the lower limit, magnetization may be insufficient. On the contrary, if the heat treatment temperature and time exceed the upper limit, the coverlay and the like may be thermally deteriorated and the production cost may be excessive.

  In the above-described method, the coil pattern and the coil core pattern can be formed by plating using a single resist pattern, which is excellent in manufacturability. In addition, since the coil core pattern formed by the above-mentioned method is obtained by laminating a coil core metal pattern on the surface of the conductive underlayer, the conductive underlayer is included on the base film side. Since the entire thickness of the coil core pattern is sufficiently larger than the conductive underlayer, the conductive underlayer may or may not be magnetized.

  The coil core pattern may be formed before the coil pattern. That is, you may perform a coil pattern formation process after a coil core pattern formation process.

<Coverlay lamination process>
In the cover lay lamination step, the cover lay is laminated on the surface of the base film and the pattern layer. Specifically, the coverlay can be laminated by sticking the cover film to the surfaces of the base film and the pattern layer via an adhesive layer.

<Advantages>
Since the printed wiring board has a coil core pattern having magnetism inside the spiral coil pattern, the coil core pattern can increase the magnetic flux density more than before without increasing the wiring density of the coil pattern. . That is, according to the printed wiring board and the manufacturing method thereof, the magnetic flux density of the planar coil can be improved at a relatively low cost.

  Since the printed wiring board can increase the magnetic flux density, it can be suitably used as an actuator, antenna, transformer, or the like for small equipment.

[Other Embodiments]
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is not limited to the configuration of the embodiment described above, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims. The

  In the said embodiment, although the printed wiring board which has a single base film and one pattern layer laminated | stacked on one surface of this base film was demonstrated, a pattern layer is laminated | stacked on both surfaces of a single base film These are also within the intended scope of the present invention. Furthermore, the printed wiring board may have a plurality of base films, and each base film may be a multilayer printed wiring board having a pattern layer on one side or both sides.

  Moreover, you may further arrange | position the solid pattern which has magnetism around the coil pattern (outside of outermost periphery wiring). Thereby, magnetic flux density can further be raised.

  In addition, the coil pattern of the said printed wiring board may be formed by a subtractive method, and may be formed by printing with paste, ink, etc. which mix | blended metals, such as copper, silver, and nickel.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

  First, the inductance of a coil pattern having an inner diameter of 2 mm, an outer diameter of 2.703 mm, the number of turns of 11, an average wiring width of 24 μm, and an average wiring spacing of 8 μm was found by simulation to be 0.496 μH. Next, when the inductance of the pattern layer in which the coil core pattern having Ni as the main component and the relative permeability of 1.5 was formed inside the innermost circumference of the coil pattern was similarly obtained, it was 0.744 μH. It was shown that the inductance (magnetic flux density) is improved by this coil core pattern.

  As described above, since the printed wiring board of the present invention can improve the magnetic flux density of the planar coil at a relatively low cost, it can be suitably used as a power feeding antenna, power receiving antenna, transformer, or the like of a portable device such as a wearable device. .

DESCRIPTION OF SYMBOLS 1 Base film 2 Pattern layer 2a Coil pattern 2b Coil core pattern 2c 1st connection terminal 2d 2nd connection terminal S Conductive base layer R Resist pattern

Claims (4)

An insulating base film;
A pattern layer laminated on at least one surface side of the base film,
A printed wiring board, wherein the pattern layer includes a conductive spiral coil pattern and a coil core pattern that is disposed inside the innermost periphery of the coil pattern and has magnetism.   The printed wiring board according to claim 1, wherein a main component of the coil core pattern is a metal, and the coil core pattern is insulated from the coil pattern. A method for producing a printed wiring board comprising a base film having insulating properties and a pattern layer laminated on at least one surface side of the base film,
A conductive underlayer laminating step of laminating a conductive underlayer on one side of the base film;
A photoresist film laminating step of laminating a photoresist film on one surface of the conductive underlayer;
A resist pattern forming step of forming a resist pattern having a reversed shape of a pattern layer including a spiral coil pattern by exposing and developing the photoresist film;
A coil pattern forming step of forming the coil pattern by plating on the conductive underlayer of the opening of the resist pattern;
A conductive underlayer removing step for removing the resist pattern and the conductive underlayer at the bottom thereof;
And a coil core pattern forming step of forming a coil core pattern having magnetism inside the innermost periphery of the coil pattern. The resist pattern formed in the resist pattern forming step includes an inverted shape of the coil core pattern,
The coil core pattern forming step
A coil core metal pattern forming step of forming a coil core metal pattern by plating the opening of the resist pattern;
The method for producing a printed wiring board according to claim 3, further comprising a magnetizing step of magnetizing the metal pattern for the coil core by heat treatment.

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