JP6384747B2 - Flexible printed wiring board for wireless communication devices - Google Patents

Description

  The present invention relates to a flexible printed wiring board.

  In recent years, with the spread of RFID (Radio Frequency IDentification) systems using near field communication (NFC) technology, non-contact IC cards, etc., an antenna device that uses a planar coiled circuit as an antenna Is widely used. Such an antenna device can be provided as a flexible printed wiring board in which a coil-like circuit is formed by laminating a conductor layer on a flexible resin film.

  Further, such a coiled circuit of the antenna device forms a magnetic flux when a current flows. However, if a metal (particularly a nonmagnetic metal) is present in the vicinity, an eddy current is generated in the metal. Then, since this eddy current forms a magnetic flux (demagnetizing field) in a direction opposite to the magnetic flux formed by the coiled circuit, and the apparent inductance of the coiled circuit is lowered, the communication performance of the coiled circuit is lowered. .

  Therefore, by arranging a magnetic material (soft magnetic material) on one side of the substrate on which the coiled circuit is formed and supplementing and blocking the magnetic flux formed by the coiled circuit, no eddy current is generated in the nearby conductor. There is a known technique (see Japanese Patent Application No. 2005-122595).

JP 2005-122595 A

  Ferromagnetic materials used in the antenna device include a ferrite sintered body having a high ability to supplement magnetic flux, a high magnetic permeability, and a low coercive force. However, such materials are generally brittle and easy to chip. For this reason, when a magnetic body is laminated on one side of the coiled circuit, the magnetic body may be chipped and the scraps may be scattered around, which requires care in handling.

  In addition, the magnetic material is relatively expensive, and if the magnetic material is laminated on the entire surface of the coiled circuit, the flexible printed wiring board becomes expensive.

  In view of the above-described circumstances, an object of the present invention is to provide an inexpensive flexible printed wiring board that includes a coiled circuit with high communication performance and is difficult to scatter magnetic materials.

  The invention made in order to solve the above problems includes a first coil layer constituting a first coiled circuit, a first insulating layer made of a synthetic resin, a magnetic layer containing a ferromagnetic material, and a synthetic resin. A flexible printed wiring board comprising a second insulating layer and a second coil layer constituting a second coiled circuit in this order, wherein the first coil layer and the second coil layer are electrically connected. .

  The flexible printed wiring board of the present invention includes a coiled circuit with high communication performance while being inexpensive, and the magnetic material is not easily scattered.

It is a typical exploded perspective view showing the flexible printed wiring board of one embodiment of the present invention. It is a typical fragmentary sectional view of the flexible printed wiring board of FIG.

[Description of Embodiment of the Present Invention]
The present invention provides a first coil layer constituting a first coiled circuit, a first insulating layer made of synthetic resin, a magnetic layer containing a ferromagnetic material, a second insulating layer made of synthetic resin, A flexible printed wiring board comprising a second coil layer constituting a coil-like circuit in this order, wherein the first coil layer and the second coil layer are electrically connected.

  In the flexible printed wiring board, since the first coiled circuit and the second coiled circuit are magnetically separated by the magnetic layer, the first coiled circuit and the second coiled circuit do not interfere with each other, High communication performance can be demonstrated. Moreover, since the flexible printed wiring board has the magnetic layer sandwiched between the first insulating layer and the second insulating layer, it is difficult for the magnetic material to scatter and is easy to handle. Further, by arranging the magnetic layer between the first coiled circuit and the second coiled circuit, the magnetic flux of the first coiled circuit is interrupted on one surface of the magnetic layer, and the other of the magnetic layer is Since the magnetic flux of the second coiled circuit can be blocked in this aspect, the amount of expensive magnetic material used can be reduced and the flexible printed wiring board can be provided at low cost. Furthermore, since the flexible printed wiring board blocks the magnetic flux formed by the first coil-like circuit or the second coil-like circuit with respect to the metal disposed in the vicinity by the magnetic layer, the communication performance due to the proximity of the metal is reduced. Reduction (decrease in apparent inductance) can be suppressed. In addition, since the first coiled circuit and the second coiled circuit are arranged so as to overlap each other, per unit area of the circuit connecting the first coiled circuit and the second coiled circuit in the flexible printed wiring board. The inductance of the flexible printed wiring board can be reduced.

  In the flexible printed wiring board, the magnetic layer includes a magnetic sheet containing the ferromagnetic material, and a synthetic resin reinforcing sheet into which the magnetic sheet is fitted, and the magnetic sheet has the first coil shape. It is preferable that at least a composite projection region of the circuit occupation region and the second coiled circuit occupation region is disposed. Thus, by selectively disposing a magnetic material in a necessary region of the magnetic material layer and not using the magnetic material over the entire surface, the manufacturing cost of the flexible printed wiring board can be reduced. Further, the magnetic sheet can be easily positioned by fitting the magnetic sheet to the reinforcing sheet. Furthermore, since the magnetic layer is provided with a reinforcing sheet having higher adhesiveness than the magnetic sheet, the bonding between the region other than the magnetic sheet of the magnetic layer and the first insulating layer and the second insulating layer is ensured. Reliability and mechanical strength are increased.

  The flexible printed wiring board preferably includes a plurality of the magnetic sheets in which the magnetic layer is divided and disposed. By dividing and arranging the magnetic sheet in this way, the magnetic sheet can be efficiently cut out from the base material sheet.

  It is preferable that the flexible printed wiring board includes a through hole that electrically connects the first coil layer and the second coil layer in a reinforcing sheet region between the plurality of magnetic sheets. By arranging the through holes between the magnetic sheets divided and arranged in this way, the first coiled circuit and the second coiled circuit can be easily and reliably connected.

  In the flexible printed wiring board, it is preferable that the magnetic sheet overlaps the first coiled circuit occupying region and the second coiled circuit occupying region in plan view in 90% or more of the respective projected areas. Thus, by setting the overlapping area of the magnetic sheet, the first coiled circuit, and the second coiled circuit to 90% or more, most of the magnetic flux formed by the first coiled circuit and the second coiled circuit with the magnetic sheet. Therefore, it is possible to more reliably prevent the first coiled circuit and the second coiled circuit inductance from being lowered due to the proximity of the metal.

  The flexible printed wiring board includes a pair of connection terminals provided at ends of the first coil-shaped circuit and the second coil-shaped circuit that are not connected to each other, and the first coil-shaped circuit or the second coil-shaped circuit. It is preferable to have an intermediate terminal provided in the circuit. By providing a pair of connection terminals in this way, the first coiled circuit and the second coiled circuit can be handled as one coil, and an intermediate terminal is provided in the first coiled circuit or the second coiled circuit. By providing, the first coiled circuit and the second coiled circuit can be handled as independent coils. In addition, since the first coiled circuit and the second coiled circuit are magnetically isolated by the magnetic layer, the communication performance is unlikely to deteriorate due to interference between the first coiled circuit and the second coiled circuit. Further, the intermediate terminal can re-divide a circuit in which the first coiled circuit and the second coiled circuit are connected in series into two circuits having a desired impedance. In this configuration, since it is not necessary to install the two coils apart from each other, a plurality of coils can be arranged in a small space.

  In the flexible printed wiring board, it is preferable that the first coil layer, the first insulating layer, the second coil layer, and the second insulating layer each form a single-sided plate. Thus, the first coil layer and the first insulating layer and the second coil layer and the second insulating layer form a single-sided plate, respectively, so that the first insulating layer and the second insulating layer are the first coil layer and the second coil layer. Since it is also used as a base material for forming a coil layer, the number of layers of the entire flexible printed wiring board can be reduced, and contact between the first coiled circuit and the second coiled circuit and the magnetic body is ensured. Can be prevented. In addition, a single-sided board means the single-sided printed wiring board which formed the circuit only in the single side | surface of a base film.

  The flexible printed wiring board preferably has a coverlay laminated on at least one of the outermost surface and the outermost surface. By providing the cover lay in this way, it is possible to prevent a short circuit or damage when the flexible wiring board is incorporated into an electronic device.

[Details of the embodiment of the present invention]
Hereinafter, an embodiment of a flexible printed wiring board according to the present invention will be described in detail with reference to the drawings.

[Flexible printed wiring board]
The flexible printed wiring board of FIGS. 1 and 2 is formed in a substantially rectangular sheet shape in plan view, and in order from the surface side, a first cover lay 1 and a first coil layer 3 constituting a first coiled circuit 2 A first insulating layer 4 made of synthetic resin, a plurality of magnetic sheets 5 containing a ferromagnetic material, and a magnetic layer 7 having a reinforcing sheet 6 into which these magnetic sheets 5 are fitted, and a second insulating made of synthetic resin. The first coil shape through the layer 8, the second coil layer 10 constituting the second coiled circuit 9, the second coverlay 11, the first insulating layer 4, the reinforcing sheet 6 and the second insulating layer 8. A through hole 12 that electrically connects the circuit 2 and the second coiled circuit 9 is provided.

<Coverlay>
The first cover lay 1 and the second cover lay 11 mainly protect the first coil layer 3 and the second coil layer 10 in the flexible printed wiring board. The first cover lay 1 and the second cover lay 11 each have a cover film 13 and a cover film adhesive layer 14. In addition, the first coverlay 1 is formed with an opening 15 for allowing access to a first connection terminal 17, an intermediate terminal 18, and a second connection terminal 19 described later.

(Cover film)
The cover film 13 preferably has flexibility and insulation. Examples of the main component of the cover film 13 include polyimide resin, epoxy resin, phenol resin, acrylic resin, polyester resin, thermoplastic polyimide resin, polyethylene terephthalate resin, fluororesin, and liquid crystal polymer. In particular, a polyimide resin is preferable from the viewpoint of heat resistance. The cover film 13 may contain a resin other than the main component, a weathering agent, an antistatic agent, and the like. In addition, a main component is a component with most content, for example, points out the component which occupies 50 mass% or more in material.

  Although it does not specifically limit as a minimum of the average thickness of the cover film 13, 3 micrometers is preferable and 10 micrometers is more preferable. Moreover, as an upper limit of the average thickness of the cover film 13, although it does not specifically limit, 500 micrometers is preferable and 150 micrometers is more preferable. When the average thickness of the cover film 13 is less than the above lower limit, the protection of the first coil layer 3, the second coil layer 10, etc. may be insufficient, and the cover film 13 is required to have insulating properties. Insulation may be insufficient. On the other hand, when the average thickness of the cover film 13 exceeds the above upper limit, the protective effect of the first coil layer 3 and the second coil layer 10 may be reduced, and the cover film 13 is required to be flexible. In such a case, the flexibility may be insufficient.

  Here, the “average thickness” refers to an average value of thicknesses measured at arbitrary ten points. In the following description, the term “average thickness” is defined similarly for other members.

(Cover film adhesive layer)
Although it does not specifically limit as an adhesive agent which comprises the cover film contact bonding layer 14, The thing excellent in the softness | flexibility and heat resistance is preferable. Examples of the adhesive include various resin adhesives such as an epoxy resin, a polyimide resin, a polyester resin, a phenol resin, a polyurethane resin, an acrylic resin, a melamine resin, and a polyamideimide resin.

  As a minimum of average thickness of cover film adhesive layer 14, 5 micrometers is preferred and 10 micrometers is more preferred. On the other hand, the upper limit of the average thickness of the cover film adhesive layer 14 is preferably 50 μm, and more preferably 40 μm. When the average thickness of the cover film adhesive layer 14 is less than the lower limit, the adhesive strength of the first cover lay 1 and the second cover lay 11 to the first coil layer 3 and the second coil layer 10 may be insufficient. . Moreover, when the average thickness of the cover film contact bonding layer 14 exceeds the said upper limit, there exists a possibility that the said flexible printed wiring board may become uselessly thick.

<Coil layer>
The 1st coil layer 3 and the 2nd coil layer 10 are layers which consist of material which has electroconductivity, and constitute the 1st coil circuit 2 and the 2nd coil circuit 9, respectively. The first coil layer 3 and the second coil layer 10 form a single-sided plate, respectively, with a first insulating layer 4 and a second insulating layer 8 described later. That is, the first coil layer 3 and the second coil layer 10 are formed in advance on one side of the first insulating layer 4 and the second insulating layer 8.

  The material of the first coil layer 3 and the second coil layer 10 may be any material as long as it has conductivity, but preferably has a low electrical resistance. For example, the first coil layer 3 and the second coil layer 10 are made of copper. Further, the surfaces of the first coil layer 3 and the second coil layer 10 may be plated with gold, silver, tin or the like.

  The lower limit of the average thickness of the first coil layer 3 and the second coil layer 10 is preferably 0.1 μm, and more preferably 1 μm. On the other hand, the upper limit of the average thickness of the first coil layer 3 and the second coil layer 10 is preferably 100 μm, and more preferably 80 μm. If the average thickness of the first coil layer 3 and the second coil layer 10 is less than the above lower limit, the internal resistance may increase and the loss may be excessive, and the first coil layer 3 and the second coil layer may be insufficient due to insufficient strength. The coil layer 10 may be easily broken. Moreover, when the average thickness of the 1st coil layer 3 and the 2nd coil layer 10 exceeds the said upper limit, there exists a possibility that the said flexible printed wiring board may become thick unnecessarily.

  The first coiled circuit 2 and the second coiled circuit 9 constituted by the first coil layer 3 and the second coil layer 10 have an insulating layer 4 and an insulating layer 8 to be described later so as to draw a spiral having a substantially rectangular outer shape. It is a strip | belt-shaped electric flow path extended | stretched along an external shape line. The first coiled circuit 2 extends in the clockwise direction when viewed from the surface side, and the second coiled circuit 9 extends in the clockwise direction when viewed from the surface side. The first coiled circuit 2 and the second coiled circuit 9 are arranged such that the respective band-like portions substantially overlap in plan view.

  As shown in FIG. 1, the first coil layer 3 is provided near the first connecting terminal 17 provided at the outer end of the first coiled circuit 2 and the inner end of the first coiled circuit 2. An intermediate terminal 18 and a second connection terminal 19 provided outside the first coiled circuit 2 are provided.

  As shown in FIG. 2, the inner end of the first coiled circuit 2 and the inner end of the second coiled circuit 9 are electrically connected by a through hole 12. Similarly, the outer end of the second coiled circuit 9 and the second connection terminal 19 are also electrically connected by another through hole 12.

  Thereby, between the 1st connection terminal 17 and the 2nd connection terminal 19, the circuit which has one coil with a large inductance with which the 1st coiled circuit 2 and the 2nd coiled circuit 9 were connected in series is formed. . A circuit having only the first coiled circuit 2 is formed between the first connection terminal 17 and the intermediate terminal 18, and only the second coiled circuit 9 is provided between the intermediate terminal 18 and the second connection terminal 19. A circuit is formed. By connecting wirings to these terminals, the above circuit can be selected and used.

  The lower limit of the average width of each strip portion of the first coiled circuit 2 and the second coiled circuit 9 is preferably 0.03 mm, and more preferably 0.2 mm. On the other hand, the upper limit of the average width of each band-like portion is preferably 1.5 mm, and more preferably 1.25 mm. When the average width of each band-like portion of the first coiled circuit 2 and the second coiled circuit 9 is less than the lower limit, the mechanical strength of the first coiled circuit 2 and the second coiled circuit 9 is insufficient and breaks. There is a fear. Further, when the average width of each band-like portion of the first coiled circuit 2 and the second coiled circuit 9 exceeds the upper limit, the first coiled circuit 2 and the second coiled circuit 9 and the flexible printed wiring board are There is a risk of growing unnecessarily. The widths of the strip portions of the first coiled circuit 2 and the second coiled circuit 9 are preferably all equal.

  The gap (insulation distance) between the strip portions of the first coiled circuit 2 and the second coiled circuit 9 can be set to 0.02 mm to 4.5 mm, for example.

<Insulating layer>
The first insulating layer 4 and the second insulating layer 8 are synthetic resin layers for preventing a short circuit due to electrical contact between the first coiled circuit 2 and the second coiled circuit 9 and a magnetic sheet 5 described later. is there. Moreover, in the flexible printed wiring board of FIG.1 and FIG.2, the 1st insulating layer 4 and the 2nd insulating layer 8 form the 1st coil layer 3 and the 2nd coil layer 10, and the single-sided board. Specifically, the first coil layer 3 is formed on the front surface side of the first insulating layer 4, and the second coil layer 10 is formed on the back surface side of the second insulating layer 8. That is, the first insulating layer 4 and the second insulating layer 8 are also base films (base materials) for forming the first coil layer 3 and the second coil layer 10.

  The synthetic resin used for the first insulating layer 4 and the second insulating layer 8 is not particularly limited as long as it has insulating properties, and in particular, a synthetic resin film formed in a sheet shape having flexibility and electrical insulating properties. Can be adopted. As a material for the synthetic resin film, for example, a polyimide resin, a polyethylene terephthalate resin, a liquid crystal polymer, a fluororesin, or the like is preferably used.

  As a minimum of average thickness of the 1st insulating layer 4 and the 2nd insulating layer 8, 5 micrometers is preferred and 10 micrometers is more preferred. On the other hand, the upper limit of the average thickness of the first insulating layer 4 and the second insulating layer 8 is preferably 50 μm, and more preferably 40 μm. When the average thickness of the 1st insulating layer 4 and the 2nd insulating layer 8 is less than the said minimum, there exists a possibility that the insulation strength of the 1st insulating layer 4 and the 2nd insulating layer 8 may become inadequate. Moreover, when the average thickness of the 1st insulating layer 4 and the 2nd insulating layer 8 exceeds the said upper limit, the coupling | bonding of the magnetic flux of the 1st coiled circuit 2 and the 2nd coiled circuit 9 falls, and an inductance may become small. There is. In addition, the flexible printed wiring board may become unnecessarily thick.

  Each of the first insulating layer 4 and the second insulating layer 8 is bonded to the magnetic layer 7 by an adhesive layer 20.

(Adhesive layer)
The material of the adhesive forming the adhesive layer 20 is not particularly limited, but is preferably excellent in flexibility and heat resistance. Examples of the adhesive include various resin-based adhesives such as epoxy resin, polyimide resin, polyester resin, phenol resin, polyurethane resin, acrylic resin, melamine resin, and polyamideimide resin. A bonding sheet obtained by forming these adhesives on a film can be suitably used as the adhesive layer 20.

  The lower limit of the average thickness of the adhesive layer 20 is preferably 5 μm, and more preferably 10 μm. On the other hand, the upper limit of the average thickness of the adhesive layer 20 is preferably 50 μm, and more preferably 40 μm. When the average thickness of the adhesive layer 20 is less than the above lower limit, the adhesive strength between the first insulating layer 4 and the second insulating layer 8 and the magnetic layer 7 may be insufficient. Moreover, when the average thickness of the adhesive layer 20 exceeds the upper limit, the flexible printed wiring board may be unnecessarily thick.

<Magnetic layer>
As shown in FIG. 1, the magnetic layer 7 is configured by fitting the magnetic sheet 5 into a fitting hole 16 formed in the reinforcing sheet 6. In the flexible printed wiring board of FIG. 1, the magnetic sheet 5 is divided and disposed in two fitting holes 16.

(Magnetic sheet)
The magnetic sheet 5 supplements and blocks the magnetic flux formed by the first coiled circuit 2 and the second coiled circuit 9. The material of the magnetic sheet 5 may be any material that can efficiently supplement the magnetic flux by including a ferromagnetic material, but a material having flexibility is preferable. As the magnetic sheet 5, a material in which a ferromagnetic material is dispersed in a synthetic resin can be used, and a commercially available product such as a noise suppression sheet can be used.

  The magnetic sheet 5 is disposed in a combined projection area of the occupied area of the first coiled circuit 2 and the occupied area of the second coiled circuit 9 in the magnetic layer 7. Specifically, the two magnetic sheets 5 are formed in a substantially L shape having the same shape, and are arranged point-symmetrically so as to be combined into a substantially rectangular frame shape.

  The lower limit of the overlapping area of the magnetic sheet 5 with the first coiled circuit 2 and the second coiled circuit 9 is 90% of the projected area of the occupied area of each of the first coiled circuit 2 and the second coiled circuit 9. Is preferable, and 95% is more preferable. When the overlapping area of the magnetic sheet 5 with the first coiled circuit 2 and the second coiled circuit 9 is less than the lower limit, the magnetic sheet 5 generates the magnetic flux formed by the first coiled circuit 2 or the second coiled circuit 9. There is a risk that the effect of preventing a decrease in the apparent inductance of the first coiled circuit 2 or the second coiled circuit 9 may be insufficient due to the influence of metal present in the vicinity of the flexible printed wiring board that cannot be sufficiently supplemented. is there.

  More specifically, the magnetic sheet 5 is formed inside the first coiled circuit 2 and the second coiled circuit 9 from a rectangular region including the projected shapes of the first coiled circuit 2 and the second coiled circuit 9. It has a rectangular frame shape excluding the rectangular portion to be formed. Then, the magnetic sheet 5 is further removed from the outline by removing the two band-shaped portions so as to form an edge extending from the pair of long sides of the inner rectangular portion to the outer peripheral portion of the rectangular frame outward in opposite directions. It has a shape divided into two substantially L-shaped parts. Therefore, only the band-like portion that divides the magnetic sheet 5 into two does not overlap with the occupied areas of the first coiled circuit 2 and the second coiled circuit 9. A through-hole 12 to be described later that connects between the first coil-like circuit 2 and the second coil-like circuit 9 is disposed avoiding the magnetic sheet 5 in the band-like portion that is the reinforcing sheet region.

  The lower limit of the relative magnetic permeability of the magnetic sheet 5 is preferably 20, and more preferably 30. On the other hand, the upper limit of the relative magnetic permeability of the magnetic sheet 5 is preferably 500, and more preferably 300. When the relative permeability of the magnetic sheet 5 is less than the lower limit, the inductance is reduced by reducing the coupling of the magnetic fluxes of the first coiled circuit 2 and the second coiled circuit 9, so that the flexible printed wiring can be downsized. May interfere. Moreover, when the relative magnetic permeability of the magnetic sheet 5 exceeds the upper limit, the DC resistance of the first coiled circuit 2 and the second coiled circuit 9 is increased, and the communication performance of the flexible printed wiring may be reduced. In addition, the magnetic sheet 5 becomes overspec, and the flexible printed wiring board may be expensive.

  As a minimum of the thickness of the magnetic sheet 5, 10 micrometers is preferable and 20 micrometers is more preferable. On the other hand, the upper limit of the thickness of the magnetic sheet 5 is preferably 500 μm, and more preferably 300 μm. When the thickness of the magnetic sheet 5 is less than the lower limit, the magnetic flux formed by the first coiled circuit 2 and the second coiled circuit 9 cannot be sufficiently blocked, and communication performance may be deteriorated. Moreover, when the thickness of the magnetic sheet 5 exceeds the said upper limit, there exists a possibility that the said flexible printed wiring board may become thick unnecessarily.

(Reinforcement sheet)
The reinforcing sheet 6 is a member that positions and holds the magnetic sheet 5 in the two fitting holes 16 and improves the adhesion of the magnetic layer 7 to the first insulating layer 4 and the second insulating layer 8. . That is, in the magnetic layer 7, the reinforcing sheet 6 is present in the central rectangular portion of the magnetic sheet 5 and the belt-shaped portion that divides the magnetic sheet 5 into two. Thus, by accommodating the magnetic sheet 5 in the fitting hole 16 of the reinforcing sheet 6, even if the magnetic sheet 5 is cracked or chipped and magnetic powder is generated, the flexible printed wiring board You can keep it in the internal space and prevent it from splashing outside.

  In addition, the reinforcing sheet 6 is formed on the belt-like portion where the magnetic sheet 5 is not provided in the area occupied by the first coiled circuit 2 and the second coiled circuit 9, The through hole 12 connecting the inner end of the two-coil circuit 9 and the through hole 12 connecting the outer mold end of the second coil circuit 9 and the first connection terminal 17 of the first coil layer 3 pass through. doing.

  Although it does not specifically limit as a material of the reinforcement sheet 6, The resin film similar to the 1st insulating layer 4 and the 2nd insulating layer 8 can be used conveniently. Further, the thickness of the reinforcing sheet 6 is substantially the same as that of the magnetic sheet 5.

  The lower limit of the minimum distance from the outer peripheral edge of the reinforcing sheet 6 to the fitting hole 16 is preferably 0.5 m and more preferably 1 mm. On the other hand, the upper limit of the minimum distance from the outer peripheral edge of the reinforcing sheet 6 to the fitting hole 16 is preferably 5 mm, and more preferably 3 mm. When the minimum distance from the outer peripheral edge of the reinforcing sheet 6 to the fitting hole 16 is less than the lower limit, the adhesion between the reinforcing sheet 6 and the first insulating layer 4 and the second insulating layer 8 is incomplete and is generated from the magnetic sheet 5. The magnetic material powder may not be sealed inside the flexible printed wiring board. Moreover, when the distance of the minimum distance from the outer periphery of the reinforcement sheet 6 to the fitting hole 16 exceeds the said upper limit, there exists a possibility that the said flexible printed wiring board may enlarge unnecessarily.

<Through hole>
The through hole 12 passes through the first coil layer 3, the first insulating layer 4, the adhesive layer 20, the magnetic layer 7, the adhesive layer 20, the second insulating layer 8, and the second coil layer 10, and passes through the first coil. The circuit 2 and the second coiled circuit 9 are electrically connected. Such a through-hole 12 can be formed by forming a through hole in a laminate in which the above layers are stacked and plating the through hole with a metal such as copper. It can also be formed by injecting silver paste, copper paste or the like and heating and curing. The diameter of the through hole 12 is appropriately selected in consideration of processability, conduction characteristics, etc., and can be set to 350 μm, for example.

<Manufacturing method>
The flexible printed wiring board has a (1) single-sided board forming step, (2) magnetic layer forming step, (3) laminating step, (4) through-hole forming step, and (5) coverlay laminating step. Easy and reliable manufacture.

<(1) Single-sided plate forming step>
In the single-sided plate forming step, the first coil layer 3 and the second coil layer 10 are formed by laminating conductive materials on the first insulating layer 4 and the second insulating layer 8 respectively. The planar shapes of the first coil-like circuit 2 of the first coil layer 3 and the second coil-like circuit 9 of the second coil layer 10 can be formed by an appropriate method depending on the method of laminating the conductive material. For example, the first coiled circuit 2 and the second coiled circuit 9 can be formed by performing masking and etching on the metal film laminated on the first insulating layer 4 and the second insulating layer 8. For example, the metal film may be formed by attaching a metal foil or the like to the first insulating layer 4 and the second insulating layer 8 with an adhesive or the like. May be formed by vapor deposition. Moreover, when forming the 1st coil layer 3 and the 2nd coil layer 10 with an electrically conductive paste, the 1st coiled circuit 2 and the 2nd coiled circuit 9 can be formed with a printing technique.

<(2) Magnetic layer forming step>
In the magnetic layer forming step, the magnetic sheet 5 and the reinforcing sheet 6 are cut out from the respective sheet-like base materials, and the magnetic sheet 5 is fitted into the fitting holes 16 formed in the reinforcing sheet 6 to form the magnetic layer 7. .

<(3) Lamination process>
In the laminating step, the single-sided plate made up of the first coil layer 3 and the first insulating layer 4 formed in the single-sided plate forming step on the front and back of the magnetic layer 7 formed in the insulating layer forming step, the second coil layer 10 and Single-sided plates made of the second insulating layer 8 are laminated with the adhesive layer 20 interposed therebetween.

<(4) Through hole formation process>
In the through hole forming step, the through hole 12 penetrating the laminated body of the first coil layer 3, the first insulating layer 4, the magnetic layer 7, the second insulating layer 8, and the second coil layer 10 formed in the above laminating step is formed. Form. The through hole 12 can be formed by forming a through hole in the laminated body and plating the through hole with a metal such as copper. It can also be formed by injecting silver paste, copper paste or the like into the through-holes and heating and curing. Etching, laser processing, punching, or the like can be applied as the through hole forming method. Further, a resin or the like may be filled in the cavity inside the through hole 12 for reinforcement.

<(5) Coverlay lamination process>
In the cover lay stacking step, the first cover lay 1 is stacked on the surface of the first coil layer 3 and the second cover lay 11 is stacked on the back surface of the second coil layer 10. Specifically, the first cover lay 1 and the second cover lay 11 can be formed by attaching the cover film 13 to the first coil layer 3 and the second coil layer 10 via the cover film adhesive layer 14.

<Advantages>
In the flexible printed wiring board, the magnetic layer 7 is disposed between the first coil layer 3 and the second coil layer 10. For this reason, since the coupling of magnetic flux between the first coiled circuit 2 and the second coiled circuit 9 is improved and an increase in inductance per unit area can be expected, the first coil layer 3, the second coil layer 10, and the magnetic body The size of the layer 7 can be reduced. Further, the flexible printed wiring board can be provided at a low cost by using both surfaces of the magnetic sheet 5 because the amount of expensive magnetic material used is small.

  Further, the magnetic flux leakage of the first coiled circuit 2 and the second coiled circuit 9 due to the magnetic sheet 5 is reduced due to the improved coupling. Therefore, even if a metal exists in the vicinity of the flexible printed wiring board, an eddy current generated in the metal can be suppressed, and a decrease in inductance of the first coiled circuit 2 and the second coiled circuit 9 can be suppressed.

  Further, in the flexible printed wiring board, the magnetic sheet 5 fitted in the fitting hole 16 is surrounded by the reinforcing sheet 6 at the periphery, and the front and back surfaces thereof are the first insulating layer 4 and the second insulating layer 8. It is sandwiched between. For this reason, even if the magnetic material powder contained by the magnetic sheet 5 being damaged is separated, the magnetic material powder is sealed in the fitting hole 16 and does not leak to the outside. Therefore, the flexible printed wiring board is easy to handle because it does not generate dust.

  In the flexible printed wiring board, the magnetic sheet 5 is disposed in a composite projection region of the occupation region of the first coiled circuit 2 and the occupation region of the second coiled circuit 9. A reinforcing sheet 6 is disposed at the center. Since a material having high adhesiveness to the adhesive layer 20 can be selected for the reinforcing sheet 6, the flexible printed wiring board can be easily and reliably assembled, has a low risk of delamination, and has high reliability and mechanical strength. high.

  Moreover, the area efficiency at the time of cutting out the magnetic sheet 5 from a big sheet-like base material can be improved by dividing the magnetic sheet 5 into two. Thereby, the manufacturing cost of the flexible printed wiring board can be further reduced.

  In the flexible printed wiring board, the through-hole 12 connecting the first coiled circuit 2 and the second coiled circuit 9 includes an occupied area of the first coiled circuit 2 and an occupied area of the second coiled circuit 9. Are arranged so as to penetrate through the reinforcing sheet 6 between the magnetic sheets 5. With such an arrangement, the electrical flow path connecting the first coiled circuit 2 and the second coiled circuit 9 can be made short and simple, so the first coiled circuit 2 and the second coiled circuit The circuit 9 can be easily and reliably connected.

  In the flexible printed wiring board, the first coil layer 3 and the first insulating layer 4, the second coil layer 10 and the second insulating layer 8 each form a single-sided board. For this reason, since the 1st insulating layer 4 and the 2nd insulating layer 8 are utilized also as a base material for forming the 1st coil layer 3 and the 2nd coil layer 10, the number of the layers of the said flexible printed wiring board whole Can be reduced. Moreover, if comprised in this way, the thickness of the 1st insulating layer 4 and the 2nd insulating layer 8 will become constant, and the contact with the 1st coiled circuit 2 and the 2nd coiled circuit 9 and the magnetic sheet 5 will be ensured. Can be prevented.

  Moreover, since the flexible printed wiring board is provided with the cover lays 1 and 11 on the outermost surface and the rearmost surface, the first coiled circuit 2 and the second coiled circuit 9 are provided when the flexible printed wiring board is incorporated into an electronic device. It is prevented from being damaged or short-circuited.

[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 above embodiment, two fitting holes 16 are formed in the reinforcing sheet 6 and the magnetic sheet 5 is divided into two. However, the magnetic sheet 5 may be divided into three or more, and one magnetic sheet that is not divided. 5 may be used. In addition, the magnetic sheet 5 may be disposed in the center of the magnetic layer 7 (the inner region of the first coiled circuit 2 and the second coiled circuit 9) instead of the reinforcing sheet 6. Furthermore, the magnetic sheet 5 having the same size as that of the first insulating layer 4 and the second insulating layer 8 may be used without using the reinforcing sheet 6 at all.

  In the flexible printed wiring board, the first insulating layer 4 and the second insulating layer 8 may not form a single-sided plate with the first coil layer 3 and the second coil layer 10. For example, a base film that forms a single-sided plate together with the first coil layer 3 and the second coil layer 10 may be provided on the front surface side of the first coil layer 3 and the back surface side of the second coil layer 10. This base film may also be used as the coverlays 1 and 11. In this case, the first coil layer 3 and the second coil layer 10 and the magnetic layer 7 may be insulated by the adhesive layer 20, or a further insulating film layer may be provided to ensure insulation. . As a further alternative, after the first insulating layer 4 and the second insulating layer 8 are stacked on the magnetic layer 7, the first coil is applied to the first insulating layer 4 and the second insulating layer 8 using, for example, a conductive paste or the like. The layer 3 and the second coil layer 10 may be formed.

  In the flexible printed wiring board, the intermediate terminal 18 can be disposed at an arbitrary position of the first coiled circuit 2. Further, the intermediate terminal 18 can be disposed at an arbitrary position on the second coiled circuit 9. In that case, an opening for accessing the intermediate terminal 18 may be formed in the cover lay 11 on the back surface side, and a further through hole may be provided to connect to the intermediate terminal 18.

  In the flexible printed wiring board, the first coiled circuit 2 and the second coiled circuit 9 may be connected by means other than the through hole 12. For example, a lead wire or the like that connects the surface of the first coiled circuit 2 and the surface of the second coiled circuit 9 by bypassing the insulating layer 4, the magnetic layer 7, and the insulating layer 8 may be provided. .

  In the flexible printed wiring board, the intermediate terminal 18 is not an essential component. Conversely, two or more intermediate terminals 18 may be provided on the flexible printed wiring board.

  The flexible printed wiring board is particularly useful as an antenna device for near field communication.

DESCRIPTION OF SYMBOLS 1, 11 Coverlay 2 1st coiled circuit 3 1st coil layer 4 1st insulating layer 5 Magnetic sheet 6 Reinforcement sheet 7 Magnetic body layer 8 Second insulating layer 9 Second coiled circuit 10 2nd coil layer 12 Through hole 13 cover film 14 cover film adhesive layer 15 opening 16 fitting hole 17 first connection terminal 18 intermediate terminal 19 second connection terminal 20 adhesive layer

Claims (7)

A first coil layer constituting a first coiled circuit;
A first insulating layer made of synthetic resin;
A magnetic layer containing a ferromagnetic material;
A second insulating layer made of synthetic resin;
A second coil layer constituting the second coiled circuit in this order,
The first coil layer and the second coil layer are electrically connected;
The winding directions of the first coil circuits Ri same current direction der the winding direction of the second coil layer,
The magnetic layer includes a magnetic sheet containing the ferromagnetic material, and a synthetic resin reinforcing sheet with which the magnetic sheet is fitted,
A flexible printed wiring board for a wireless communication device , wherein the magnetic sheet is disposed at least in an overlapping projection region of the first coiled circuit occupation region and the second coiled circuit occupation region . The flexible printed wiring board for a wireless communication device according to claim 1 , wherein the magnetic layer includes a plurality of the magnetic sheets that are divided and disposed. The flexible printed wiring board for a radio communication device according to claim 2 , further comprising a through hole that electrically connects the first coil layer and the second coil layer in a reinforcing sheet region between the plurality of magnetic sheets. The said magnetic sheet overlaps with the said 1st coiled circuit occupation area | region and the said 2nd coiled circuit occupation area | region in 90% or more of each projection area in planar view, The Claim 1 , 2 or 3 Flexible printed wiring board for wireless communication devices. A pair of connection terminals provided at ends of the first coiled circuit and the second coiled circuit that are not connected to each other, and an intermediate terminal provided in the first coiled circuit or the second coiled circuit The flexible printed wiring board for a wireless communication device according to any one of claims 1 to 4 , further comprising: The wireless communication device according to any one of claims 1 to 5 , wherein the first coil layer, the first insulating layer, the second coil layer, and the second insulating layer each form a single-sided plate. Flexible printed wiring board. The flexible printed wiring board for a wireless communication device according to any one of claims 1 to 6, wherein a coverlay is laminated on at least one of the outermost surface and the outermost surface.

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