JP2004260017A - Thin film common mode choke coil and common mode choke coil array - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultra-small thin film common mode choke coil and a common mode choke coil array capable of high speed transmission of signals near GHz. <P>SOLUTION: At least two coil conductors are formed of a multilayer structure where insulation layers and conductor layers are stacked in the thickness direction on a magnetic substrate 1. At least two conductor layers 5 and 7 have a spiral conductor pattern having a conductor width (W<SB>1</SB>) W<SB>1≤</SB>36 μm. Furthermore, the conductor thickness (T) and the conductor space (W<SB>2</SB>) of the spiral shape satisfy a relation W<SB>2</SB><T×2. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a thin-film common mode choke coil and a common mode choke coil array, and more particularly to a filter used for suppressing a common mode current which causes electromagnetic interference which is a problem in a balanced transmission system.
[0002]
[Prior art]
Conventionally, a multilayer type is known as a chip-type common mode choke coil. This component has a structure in which a coil conductor pattern is formed on the surface of a magnetic material sheet such as ferrite to form a first coil, and a first coil magnetic sheet and a similar second coil magnetic sheet are alternately laminated.
[0003]
Also, a common mode choke coil disclosed in Patent Document 1 below is known as one using a thin film method. In this part, a lead electrode is formed on a magnetic substrate by a thin film method, and then an insulating layer, a first coil conductor, an insulating layer, a second coil conductor, and an insulating layer are sequentially formed by a thin film method, and the magnetic layer is formed from the upper surface. The structure is sandwiched between substrates.
[0004]
[Patent Document 1] JP-A-8-203737
[Problems to be solved by the invention]
In the above-described conventional laminated type, a magnetic sheet exists between the first coil and the second coil conductor, and when used as a common mode choke coil, the magnetic coupling between the two coils is reduced, causing a problem in characteristics. .
[0006]
Further, the thin-film type common mode choke coil using the thin-film method of Patent Document 1 is a non-magnetic insulating layer between two coil conductors, and is sandwiched between magnetic substrates from above and below, so that magnetic coupling is not possible. The problem has been solved.
[0007]
However, recent balanced transmission lines require high-speed transmission of transmission signals in the vicinity of GHz, and cannot cope with this high-speed transmission.
[0008]
There are several measures for the high-speed transmission.
[0009]
The first is matching of characteristic impedance. The importance of this matching is well known in transmission circuits.
[0010]
Second, there is a further improvement in magnetic coupling. However, this improvement has structural limitations.
[0011]
A third measure is to reduce the capacitance between conductors. However, simply increasing the space between conductors in order to lower the capacitance results in an increase in size.
[0012]
In view of the above, it is an object of the present invention to provide an ultra-small thin-film common mode choke coil and a common mode choke coil array capable of high-speed transmission of a transmission signal in the vicinity of GHz.
[0013]
Other objects and novel features of the present invention will be clarified in embodiments described later.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, a thin-film common mode choke coil according to the invention of claim 1 of the present application is a laminated structure in which an insulating layer and a conductor layer are stacked in a thickness direction on a magnetic substrate, and has at least two coil conductors. Wherein at least two conductor layers are spiral-shaped conductor patterns, and the spiral-shaped conductor pattern has a conductor width (W ₁ ) of W ₁ ≦ 36 μm.
It is characterized by being.
[0015]
In the thin film common mode choke coil according to the invention of claim 2 of the present application, the relationship between the conductor thickness (T) of the spiral-shaped conductor pattern and the space between conductors (W ₂ ) is W ₂ <T × 2.
It is characterized by having.
[0016]
The thin-film common mode choke coil according to the invention of claim 3 of the present application is the method according to claim 1 or 2, wherein the spiral-shaped conductor pattern comprises a base conductor formed of a thin film and a thickened conductor thereon. It is characterized in that the thick conductor is a Cu plating layer.
[0017]
The thin-film common mode choke coil according to claim 4 of the present invention is characterized in that, in claim 3, the lower layer of the base conductor is Cr and the upper layer is Cu, or the lower layer is Ti and the upper layer is Cu. I have.
[0018]
The thin-film common mode choke coil according to the invention of claim 5 of the present application is characterized in that, in claim 3 or 4, the surface of the spiral-shaped conductor pattern is covered with a Ni plating film.
[0019]
The invention of claim 6 of the present application is characterized in that in claim 1, 2, 3, 4, or 5, the upper surface of the laminated structure is covered with a magnetic material.
[0020]
The invention of claim 7 of the present application is characterized in that in claim 1, 2, 3, 4, or 5, another magnetic substrate is attached to the upper surface of the laminated structure.
[0021]
The invention of claim 8 of the present application is characterized in that it is a thin film common mode choke coil array including a plurality of thin film common mode choke coils according to claim 1, 2, 3, 4, 5, 6, or 7.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a thin-film common mode choke coil and a common mode choke coil array according to the present invention will be described with reference to the drawings.
[0023]
1 and 2 show an embodiment of the present invention. FIG. 1 is an exploded perspective view of a thin-film common mode choke coil, and FIG. 2 is an external perspective view. At the time of actual production, a plurality of components are produced on a substrate at the same time, but in this embodiment, description will be made for one element.
[0024]
As shown in these figures, a thin-film common mode choke coil having an outer shape of a chip type has an insulating layer 2, a first extraction electrode layer 3, an insulating layer 4, and a first coil conductor on a main surface of a first magnetic substrate 1. Layer (spiral-shaped coil conductor pattern) 5, insulating layer 6, second coil conductor layer (spiral-shaped coil conductor pattern) 7, insulating layer 8, second extraction electrode layer 9, insulating layer 10, and second magnetic substrate 11 in this order. It is configured to be laminated and integrated. The first coil conductor layer 5 and the second coil conductor layer 7 are arranged so as to be magnetically coupled. When a current in the differential mode flows through both conductor layers 5 and 7, the magnetic fluxes cancel each other, and the current in the common mode is reduced. When flowing, the magnetic flux is added.
[0025]
At this time, the first extraction electrode layer 3 and the first coil conductor layer 5, and the second extraction electrode layer 9 and the second coil conductor layer 7 are electrically connected via the through holes 4a and 8a, respectively. One end of each lead electrode layer and one end of each coil conductor layer are connected to an external electrode 15 (formed on the outer peripheral surface of the chip as shown in FIG. 2).
[0026]
The magnetic substrates 1 and 11 are made of sintered ferrite, composite ferrite or the like, and the insulating layers 2, 4, 6, 8 and 10 are made of a material having excellent insulation properties and good workability, such as polyimide resin and epoxy resin.
[0027]
FIG. 3 shows the relationship between the conductor width of the first coil conductor layer 5 and the second coil conductor layer 7, which are spiral coil conductor patterns, and the attenuation characteristics of the transmission signal. In FIG. 3, a curve a represents a conductor width of 45 μm, a space between conductors of 20 μm, a curve b represents a conductor width of 36 μm, a space of 13 μm between conductors, and a curve c represents a differential mode attenuation characteristic (dB) when the conductor width is 12 μm and the space between conductors is 12 μm. It is a frequency characteristic, and the data transmission attenuation characteristic is improved by reducing the width of the spiral conductor. Further, from FIG. 3, it is effective to reduce the conductor width to 36 μm or less in order to set the cutoff frequency (attenuation-3 dB) of the transmission signal to 2.4 GHz (800 MHz transmission × 3) or more. Therefore, the conductor width _{W 1} of the first and second coil conductor layers 5 and 7 _{W 1} ≦ 36 .mu.m
It can be said that this has a great effect on high-speed transmission.
[0028]
At this time, a decrease in the conductor width causes an increase in DC resistance, but it is necessary to increase the conductor thickness in order to suppress the decrease. In order to increase the conductor thickness, side etching twice as large as the conductor thickness T occurs in the vacuum film forming / etching method, and when the conductor thickness is increased, the space between the conductors becomes T × 2 or more, and the conductor becomes practically real. It is difficult to increase the thickness (the space between conductors must be wide and the spiral formation area must be large).
[0029]
This can be improved by forming the spiral coil conductor layers 5 and 7 by electroplating (additive method). The spiral conductor thickness and the space between conductors can be in the following relationship, and the thick spiral coil conductor layers 5 and 7 can be formed in a small space.
W ₂ <T × 2
[0030]
The procedure for forming the spiral-shaped coil conductor layers 5 and 7 under the above conditions by plating is as follows.
[0031]
As shown in FIG. 4A, a base conductor film 20 is formed on the insulating layers 4 and 6 by a vacuum film forming method (sputtering or the like). At this time, the base conductor film 20 is preferably made of Cr / Cu (Cr in the lower layer, Cu in the upper layer) or Ti / Cu in consideration of the adhesion of the insulating layers 4 and 6 to the resin and the subsequent electroplating.
[0032]
A photoresist 21 is applied on the film. At this time, it is preferable to apply the photoresist 21 thicker than the spiral conductor thickness to be electroplated thereafter.
[0033]
Next, exposure is performed using a photomask having a pattern necessary for forming a spiral conductive pattern, and the resist 21 is developed, whereby a resist pattern shown in FIG. 4B is formed. That is, the underlying conductive film 20 is exposed so as to match the spiral shape.
[0034]
Next, as shown in FIG. 4C, electroplating of the thick conductor 22 is performed using the base conductor film 20 already formed as an electrode. At this time, the pattern of the resist 21 becomes a dam, and electroplating is formed in a spiral shape.
[0035]
Next, as shown in FIG. 4 (D), the unnecessary resist after the electroplating is removed, and further, as shown in FIG. 4 (E), the underlying conductor film other than the thick conductor 22 formed by the spiral plating portion. 20 is removed by etching. Thereby, the spiral coil conductor layers 5 and 7 are completed.
[0036]
The electroplated metal used for the thick conductor is preferably Cu in consideration of the plating property, cost, electric conductivity and the like.
[0037]
Also, in consideration of corrosion resistance and the adhesion of the resin applied to the upper layer on the Cu thick conductor 22 formed by electroplating, it is also effective to cover with Ni plating as shown in FIG. .
[0038]
Next, a manufacturing procedure of the thin-film common mode choke coil will be described with reference to FIG. An insulating layer 2 is formed on a first magnetic substrate 1. As a forming method, a spin coating method, a dip method, a spray method, and a printing method are employed.
[0039]
Next, a conductor is formed on the insulating layer 2, and the first extraction electrode layer 3 is formed by photolithography. Sputtering, vapor deposition, plating and the like are adopted as a film forming method. In the photolithography method, a photosensitive resist is used. After exposure and development, unnecessary metal portions are etched, and then the resist is removed.
[0040]
Next, the insulating layer 4 is formed. The formation method is the same as that of the insulating layer 2, but in order to connect the lead electrode layer 3 and the spiral-shaped first coil conductor layer 5, a through hole 4 a is formed by development using a photolithography method. The extraction electrode layer 3 and the first coil conductor layer 5 are electrically connected by the through hole 4a.
[0041]
Next, film formation and patterning of the first coil conductor 5 having a spiral shape are performed, and the electroplating method (additive method) is used as described in FIG.
[0042]
Next, the insulating layer 6 is formed by the same method as the insulating layer 2, and a spiral-shaped second coil conductor 7 is formed and patterned thereon. This is the same as the first coil conductor 5.
[0043]
Next, the insulating layer 8 is formed by the same method as the insulating layer 4, and the through-hole 8a is developed using a photolithography method to connect the second extraction electrode layer 9 and the spiral-shaped second coil conductor layer 7. Formed by
[0044]
Next, the second extraction electrode layer 9 is formed by the same method as the first extraction electrode layer 3.
[0045]
Next, the insulating layer 10 is formed by the same method as the insulating layer 2, and the second magnetic substrate 11 is attached thereon.
[0046]
Although the above description has been made with reference to the drawing for one element, actually, a plurality of elements are simultaneously manufactured on the substrate. After the device fabricated on this substrate is cut into one element shape, the external electrodes 15 are formed as shown in FIG. 2 to complete the common mode choke coil.
[0047]
According to this embodiment, the following effects can be obtained.
[0048]
(1) The first and second coil conductor layers 5 and 7, which are two-layer spiral conductor patterns, have a conductor width (W ₁ ) of W ₁ ≦ 36 μm.
As can be seen from FIG. 3, the cut-off frequency of the transmission signal can be set to 2.4 GHz or higher, which can support high-speed transmission.
[0049]
(2) By forming the thick conductor 22 on the underlying conductor film 20 using the electroplating method (additive method) shown in FIG. 4, the conductor thickness (T ) And the space between conductors (W ₂ ) is W ₂ <T × 2
It is possible to reduce the space between the conductors and to reduce the size (area) of the spiral shape.
[0050]
(3) Since the lower layer of the base conductor film 20 is made of Cr and the upper layer is made of Cu, or the lower layer is made of Ti and the upper layer is made of Cu, the adhesion of the insulating layer to the resin is good. It is suitable for electroplating.
[0051]
(4) By coating the surfaces of the spiral-shaped coil conductor layers 5 and 7 with a Ni plating film, it is possible to improve the corrosion resistance and to improve the adhesion of the insulating layer of the resin applied to the upper layer. .
[0052]
FIG. 5 shows another embodiment of the present invention, in which a thin-film common mode choke coil array is manufactured. In this case, two configurations of the common mode choke coil of the embodiment are formed on the first magnetic substrate 1 side by side. With this configuration, a 2010 type (2 mm long, 1 mm wide, 1 mm thick) common mode choke coil array can be realized. Note that the same or corresponding parts as those of the above-described embodiment are denoted by the same reference numerals, and detailed description is omitted.
[0053]
In each embodiment, instead of attaching the second magnetic substrate, a structure in which a magnetic material such as a resin containing magnetic powder is provided by coating or the like may be adopted.
[0054]
Although the embodiments of the present invention have been described above, it will be obvious to those skilled in the art that the present invention is not limited to the embodiments and various modifications and changes can be made within the scope of the claims.
[0055]
【The invention's effect】
As described above, according to the present invention, high-speed transmission of transmission signals in the vicinity of GHz is possible, and an ultra-small thin-film common mode choke coil and a common mode choke coil array can be realized.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a thin-film common mode choke coil according to an embodiment of the present invention.
FIG. 2 is a perspective view showing an appearance of the embodiment.
FIG. 3 is a graph showing a differential mode attenuation characteristic of a common mode choke coil.
FIG. 4 is an explanatory view showing a step of forming a spiral-shaped conductor pattern in the embodiment.
FIG. 5 is an exploded perspective view showing a thin-film common mode choke coil array according to another embodiment of the present invention.
[Explanation of symbols]
1,11 Magnetic substrate 2,4,6,8,10 Insulating layer 3,9 Extraction electrode layer 5,7 Coil conductor layer 20 Base conductor film 21 Resist pattern 22 Thick conductor

Claims (8)

A laminated structure in which an insulating layer and a conductor layer are stacked in a thickness direction on a magnetic substrate, at least two coil conductors are formed, and at least two of the conductor layers are spiral-shaped conductor patterns. The conductor pattern has a conductor width (W ₁ ) of W ₁ ≦ 36 μm
A thin film common mode choke coil characterized by the following. The relationship between the conductor thickness (T) of the spiral-shaped conductor pattern and the space between conductors (W ₂ ) is represented by W ₂ <T × 2.
The thin-film common mode choke coil according to claim 1, wherein The thin-film common mode choke coil according to claim 1 or 2, wherein the spiral-shaped conductor pattern comprises a base conductor formed of a thin film and a thick conductor thereon. The thick conductor is a Cu plating layer. 4. The thin-film common mode choke coil according to claim 3, wherein the lower layer of the base conductor is Cr and the upper layer is Cu, or the lower layer is Ti and the upper layer is Cu. 5. The thin-film common mode choke coil according to claim 3, wherein the surface of the spiral-shaped conductor pattern is covered with a Ni plating film. The thin-film common mode choke coil according to claim 1, 2, 3, 4, or 5, wherein an upper surface of the multilayer structure is covered with a magnetic material. The thin film common mode choke coil according to claim 1, 2, 3, 4, or 5, wherein another magnetic substrate is attached to an upper surface of the laminated structure. A thin-film common-mode choke coil array including a plurality of the thin-film common-mode choke coils according to claim 1, 2, 3, 4, 5, 6, or 7.

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