Patent Grant
12080470
This application claims benefit of priority to Japanese Patent Application No. 2020-017321, filed Feb. 4, 2020, the entire content of which is incorporated herein by reference.
The present disclosure relates to a common-mode choke coil. More specifically, the present disclosure relates to a multilayer common-mode choke coil including a multilayer body with plural stacked non-conductor layers, and first and second coils incorporated in the multilayer body.
A technique that is of interest for the present disclosure is described in, for example, Japanese Unexamined Patent Application Publication No. 2006-313946. The technique described in Japanese Unexamined Patent Application Publication No. 2006-313946 relates to a multilayer common-mode choke coil. The common-mode choke coil is an ultra-small thin-film common-mode choke coil, and capable of high-speed transmission of transmission signals at frequencies near the GHz range. More specifically, Japanese Unexamined Patent Application Publication No. 2006-313946 describes a common-mode choke coil with a cutoff frequency of greater than or equal to 2.4 GHz, the cutoff frequency being defined as the frequency at which the attenuation of a transmission signal (differential-mode signal) reaches −3 dB.
Advances in high-speed communication technology have led to the growing need for a multilayer common-mode choke coil that can, at increasingly higher frequencies, transmit differential-mode signals and attenuate common-mode noise components.
Accordingly, the present disclosure provides a multilayer common-mode choke coil that can, at higher frequencies such as 25 GHz to 30 GHz, and even at very high frequencies such as above 30 GHz, transmit differential-mode signals, and suppress common-mode noise components.
A common-mode choke coil according to preferred embodiments of the present disclosure includes a multilayer body, a first coil, a second coil, a first terminal electrode, a second terminal electrode, a third terminal electrode, and a fourth terminal electrode. The multilayer body includes a plurality of non-conductor layers, the plurality of non-conductor layers being stacked and each made of a non-conductor. The first coil and the second coil are incorporated in the multilayer body. The first terminal electrode and the second terminal electrode are provided on an outer surface of the multilayer body, the first terminal electrode being electrically connected to a first end, the second terminal electrode being electrically connected to a second end, the first end and the second end being different ends of the first coil. The third terminal electrode and the fourth terminal electrode are provided on an outer surface of the multilayer body, the third terminal electrode being electrically connected to a third end, the fourth terminal electrode being electrically connected to a fourth end, the third end and the fourth end being different ends of the second coil.
The plurality of non-conductor layers include a first plurality of non-conductor layers and a second plurality of non-conductor layers. The first coil includes a first coil conductor disposed along a first interface, the first interface being an interface between the first plurality of non-conductor layers. The second coil includes a second coil conductor disposed along a second interface, the second interface being an interface between the second plurality of non-conductor layers.
To address the above-mentioned technical problem, according to preferred embodiments of the present disclosure, with the first coil conductor and the second coil conductor being viewed in plan in the stacking direction of the multilayer body, the first coil conductor and the second coil conductor have no portion where the first coil conductor and the second coil conductor overlap each other, except for a portion where the first coil conductor and the second coil conductors cross each other.
According to preferred embodiment of the present disclosure, the stray capacitance between the first coil and the second coil can be reduced to thereby improve high-frequency characteristics.
Other features, elements, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of preferred embodiments of the present disclosure with reference to the attached drawings.
With reference to
As illustrated in
The multilayer body 2 is substantially a cuboid in shape that has a first major face 5, a second major face 6, a first lateral face 7, a second lateral face 8, a first end face 9, and a second end face 10. The first major face 5 and the second major face 6 extend in the direction in which the non-conductor layers 3 extend, and are opposite to each other. The first lateral face 7 and the second lateral face 8 couple the first major face 5 and the second major face 6 to each other, and are opposite to each other. The first end face 9 and the second end face 10 couple the first major face 5 and the second major face 6 to each other and couple the first lateral face 7 and the second lateral face 8 to each other, and are opposite to each other. The cuboid may be, for example, rounded or chamfered in its edge and corner portions.
As illustrated in
As illustrated in
The following description assumes that the non-conductor layers 3a, 3b, 3c, 3d, and 3e are stacked from the bottom to the top in the order depicted in
Referring to
The first connection end portion 23 is disposed along the interface between the non-conductor layers 3a and 3b different from the interface between the non-conductor layers 3b and 3c along which the first coil conductor 17 is disposed. The first extended conductor 19 includes a first via-conductor 27, and a first coupling part 29. The first via-conductor 27 is connected to the first coil conductor 17, and penetrates the non-conductor layer 3b, which is located between the first coil conductor 17 and the first connection end portion 23, in the thickness direction of the non-conductor layer 3b. The first coupling part 29 is disposed along the interface between the non-conductor layers 3a and 3b along which the first connection end portion 23 is disposed. The first coupling part 29 connects the first via-conductor 27 and the first connection end portion 23 to each other. The first coupling part 29 is preferably shaped to extend substantially linearly. This makes it possible to reduce the inductance resulting from the first coupling part 29, leading to improved high-frequency characteristics.
As described below, the second coil 12 also has elements similar to those of the first coil 11.
The second coil 12 includes a second coil conductor 18 disposed along the interface between the non-conductor layers 3c and 3d. The second coil 12 includes a third extended conductor 21, and a fourth extended conductor 22. The third extended conductor 21 provides the second coil 12 with the third end 12a. The fourth extended conductor 22 provides the second coil 12 with the fourth end 12b. The third extended conductor 21 includes a third connection end portion 25. The third connection end portion 25 is connected to the third terminal electrode 15 at a location on the outer surface of the multilayer body 2. The fourth extended conductor 22 includes a fourth connection end portion 26. The fourth connection end portion 26 is connected to the fourth terminal electrode 16 at a location on the outer surface of the multilayer body 2.
The third connection end portion 25 is disposed along the interface between the non-conductor layers 3d and 3e different from the interface between the non-conductor layers 3c and 3d along which the second coil conductor 18 is disposed. The third extended conductor 21 includes a second via-conductor 28, and a second coupling part 30. The second via-conductor 28 is connected to the second coil conductor 18, and penetrates the non-conductor layer 3d, which is located between the second coil conductor 18 and the third connection end portion 25, in the thickness direction of the non-conductor layer 3d. The second coupling part 30 is disposed along the interface between the non-conductor layers 3d and 3e along which the third connection end portion 25 is disposed. The second coupling part 30 connects the second via-conductor 28 and the third connection end portion 25 to each other. As with the first coupling part 29 mentioned above, the second coupling part 30 is preferably shaped to extend substantially linearly. This makes it possible to reduce the inductance resulting from the second coupling part 30, leading to improved high-frequency characteristics.
The common-mode choke coil 1 is mounted with the second major face 6 of the multilayer body 2 directed toward a mounting substrate. In one exemplary embodiment of the common-mode choke coil 1, the multilayer body 2 has a length dimension L of greater than or equal to about 0.55 mm and less than or equal to about 0.75 mm (i.e., from about 0.55 mm to about 0.75 mm), which is defined between the first and second end faces 9 and 10 that are opposite to each other, a width dimension W of greater than or equal to about 0.40 mm and less than or equal to about 0.60 mm (i.e., from about 0.40 mm to about 0.60 mm), which is defined between the first and second lateral faces 7 and 8 that are opposite to each other, and a height dimension H of greater than or equal to about 0.20 mm and less than or equal to about 0.40 mm (i.e., from about 0.20 mm to about 0.40 mm), which is defined between the first and second major faces 5 and second major face 6 that are opposite to each other.
As is apparent from
The number of turns mentioned above is defined as follows. The first coil conductor 17 and the second coil conductor 18 each have a portion that extends in a substantially arcuate shape. Referring now to
The smaller the number of turns of the first coil conductor 17 and the number of turns of the second coil conductor 18, the more the stray capacitance generated between the first coil 11 and the second coil 12 can be reduced. Hence, a smaller number of turns can contribute to improved high-frequency characteristics of the common-mode choke coil 1.
As clearly illustrated in
Preferably, the distance SG1 from the first lateral face 7 to the first coil conductor 17, and the distance SG2 from the first lateral face 7 to the second coil conductor 18 differ from each other with a difference greater than the line width of the coil conductor 17, which is the closer one of the two coil conductors to the first lateral face 7. The distance SG1 from the second lateral face 8 to the first coil conductor 17, and the distance SG2 from the second lateral face 8 to the second coil conductor 18 differ from each other with a difference greater than the line width of the coil conductor 17, which is the closer one of the two coil conductors to the second lateral face 8. The distance from the first end face 9 to the first coil conductor 17 (no corresponding reference sign is illustrated in
As is apparent from
Preferably, the first coil conductor 17 and the second coil conductor 18 have a distance between each other of greater than or equal to about 6 μm and less than or equal to about 26 μm (i.e., from about 6 μm to about 26 μm). If the distance is less than about 6 μm, this may cause the stray capacitance generated between the first coil conductor 17 and the second coil conductor 18 to become large enough to degrade high-frequency characteristics. By contrast, if the distance is greater than about 26 μm, this may cause a decrease in the coefficient of coupling between the first coil 11 and the second coil 12.
Although each of the non-conductor layers 3a, 3b, 3c, 3d, and 3e is depicted in
Preferably, each of the first coil conductor 17 and the second coil conductor 18 has a line width of greater than or equal to about 10 μm and less than or equal to about 24 μm (i.e., from about 10 μm to about 24 μm). If the line width is less than about 10 μm, this may cause the coil conductors 17 and 18 to have an increased direct-current resistance. By contrast, if the line width is greater than about 24 μm, this may cause the stray capacitance generated between the first coil conductor 17 and the second coil conductor 18 to become large enough to degrade high-frequency characteristics.
The terminal electrodes 13 to 16 extend over an area from the first major face 5 to the second major face 6. In this regard, each of the terminal electrodes 13 to 16 has a width on the first lateral face 7 or the second lateral face 8 (the width of the first terminal electrode 13 on the first lateral face 7 is denoted by “W1” in
Each of the terminal electrodes 13 to 16 is depicted in
Reference is now made to a preferred manufacturing method for the common-mode choke coil 1.
The following process is performed to produce a glass-ceramic sheet that is to become each non-conductor layer 3. First, K2O, B2O3, and SiO2, and as required, Al2O3 are weighed in a predetermined ratio, put into a crucible made of platinum, and melted by being raised to a temperature of about 1500 to 1600° C. in a firing furnace. The resulting melted substance is rapidly cooled to yield a glass material.
An example of the above-mentioned glass material is a glass material containing at least K, B, and Si, with K contained at a K2O equivalent of about 0.5 to 5 mass %, B at a B2O3 equivalent of about 10 to 25 mass %, Si at an SiO2 equivalent of about 70 to 85 mass %, and Al at an Al2O3 equivalent of about 0 to 5 mass %.
Subsequently, the above-mentioned glass material is pulverized to obtain glass powder with a D50 particle size (particle size equivalent to 50% of the volume-based cumulative percentage) of about 1 to 3 μm.
Subsequently, alumina powder and quartz (SiO2) powder both having a D50 particle size of about 0.5 to 2.0 μm are added to the above-mentioned glass powder. The resulting powder is charged into a ball mill together with PSZ media. Further, an organic binder such as a polyvinyl butyral-based organic binder, an organic solvent such as ethanol or toluene, and a plasticizer are charged into the ball mill and mixed together to obtain a glass-ceramic slurry.
Then, the slurry is formed into a sheet with a film thickness of about 20 to 30 μm by a method such as the doctor blade method, and the obtained sheet is punched in a substantially rectangular shape. Plural glass-ceramic sheets are thus obtained.
Examples of inorganic components contained in each glass-ceramic sheet mentioned above include a dielectric glass material containing about 60 to 66 mass % of a glass material, about 34 to 37 mass % of quartz, and about 0.5 to 4 mass % of alumina.
Meanwhile, a conductive paste containing Ag as a conductive component and used for forming the first coil 11 and the second coil 12 is prepared.
Subsequently, a predetermined glass-ceramic sheet is subjected to, for example, irradiation with laser light to thereby provide the glass-ceramic sheet with a through-hole in which to place each of via-conductors 27 and 28. Then, the conductive paste is applied to the predetermined glass-ceramic sheet by, for example, screen printing. Thus, the via-conductors 27 and 28 with the conductive paste filling the above-mentioned through-hole are formed, and the coil conductors 17 and 18, the connection end portions 23 to 26 respectively constituting the extended conductors 19 to 22, and the coupling parts 29 and 30 are formed in a patterned state.
Subsequently, plural glass-ceramic sheets are stacked such that the non-conductor layers 3a to 3e stacked in the order illustrated in
Subsequently, the stacked glass-ceramic sheets are subjected to a warm isotropic press process at a temperature of about 80° C. and a pressure of about 100 MPa to obtain a multilayer block.
Subsequently, the multilayer block is cut with a dicer or other device into individual discrete multilayer structures each dimensioned such that the multilayer structure can become the multilayer body 2 of each individual common-mode choke coil 1.
Subsequently, each discrete multilayer structure thus obtained is fired in a firing furnace at a temperature of about 860 to 900° C. for about 1 to 2 hours, for example, at a temperature of about 880° C. for about 1.5 hours to thereby obtain the multilayer body 2.
The fired multilayer body 2 is preferably placed into a rotating barrel together with media. Then, as the multilayer body 2 is rotated, the edge and corner portions of the multilayer body 2 are rounded or chamfered.
Subsequently, a conductive paste containing Ag and glass is applied to portions of the multilayer body 2 to which the connection end portions 23 to 26 are extended. Then, the conductive paste is baked at a temperature of, for example, about 810° C. for about 1 minute to thereby form an underlying film for each of the terminal electrodes 13 to 16. The underlying film has a thickness of, for example, about 5 μm. Then, for example, a Ni film and a Sn film are formed sequentially on the underlying film by electroplating. The Ni film and the Sn film each have a thickness of, for example, about 3 μm.
In this way, the common-mode choke coil 1 illustrated in
As described above, with the first coil conductor 17 and the second coil conductor 18 being viewed in plan in the stacking direction of the multilayer body 2, the first coil conductor 17 and the second coil conductor 18 have no portion where the two coil conductors overlap each other, except for a portion where the two coil conductors cross each other. This configuration allows for improved high-frequency characteristics of the common-mode choke coil 1. An experiment conducted to verify this observation is described below.
Exemplary Experiment
Referring to
Table 1 below illustrates the distances SG1 and SG2 for each of Sample (indicated as “S” in Table 1) 1 to Sample 5. The multilayer body of the common-mode choke coil corresponding to each sample is dimensioned to have a length dimension L of 0.65 mm, a width dimension W of 0.50 mm, and a height dimension H of 0.30 mm
As with Samples 2 to 5 in Table 1, making the distances SG1 and SG2 different from each other means, as seen in plan view in the stacking direction of the multilayer body, minimizing the overlapping portion between the first coil conductor and the second coil conductor, or even eliminating the overlapping portion between the two coil conductors, except for a portion where the two coil conductors cross each other.
In the exemplary experiment, for all of the common-mode choke coils corresponding to Samples 1 to 5, the first coil conductor 17 and the second coil conductor 18 each have a line width of 0.018 mm. The difference between the distances SG1 and SG2 is 0.020 mm even for Sample 2 with the smallest value of this difference among Samples 2 to 5. This means that for all of Samples 2 to 5, as illustrated in
For all of the common-mode choke coils corresponding to Samples 1 to 5, the number of turns of the first coil conductor 17 is 0.8, and the number of turns of the second coil conductor 18 is 1. With the first coil conductor 17 and the second coil conductor 18 being viewed in plan in the stacking direction of the multilayer body 2, the first coil conductor 17 and the second coil conductor 18 cross each other at two locations.
For each of the common-mode choke coils corresponding to Samples 1 to 5, the transmission characteristic for common-mode components (Scc21 transmission characteristic) and the transmission characteristic for differential-mode components (Sdd21 transmission characteristic) are obtained.
From the characteristic charts in
In Table 1, the evaluation (indicated as “EV” in Table 1) for a sample is “pass” (marked “P”) if the peak position of the Scc21 characteristic, that is, the frequency at which the transmission coefficient is minimum is located at or above 24 GHz, and the evaluation is “fail” (marked “F”) if this peak is located below 24 GHz.
Further, the evaluation is “pass” (marked “P”) if the minimum transmission coefficient of the Scc21 characteristic, that is, the transmission coefficient at the peak position is less than or equal to −20 dB, and the evaluation is “fail” (marked “F”) if this minimum transmission coefficient is greater than −20 dB. In Table 1, no sample is marked “F”.
Further, the evaluation is “pass” (marked “P”) if the transmission coefficient at 20 GHz of the Sdd21 characteristic is greater than or equal to −3 dB, and the evaluation is “fail” (marked “F”) if this transmission coefficient is less than −3 dB. In Table 1, no sample is marked F.
Likewise, for the transmission coefficient at 30 GHz of the Sdd21 characteristic, the evaluation is “pass” (marked “P”) if this transmission coefficient is greater than or equal to −3 dB, and the evaluation is “fail” (marked “F”) if this transmission coefficient is less than −3 dB.
Likewise, for the transmission coefficient at 40 GHz of the Sdd21 characteristic, the evaluation is “pass” (marked “P”) if this transmission coefficient is greater than or equal to −3 dB, and the evaluation is “fail” (marked “F”) if this transmission coefficient is less than −3 dB.
As can be appreciated from Table 1, for Samples 2 to 5 in which the first coil conductor and the second coil conductor do not overlap each other anywhere except for where the two coil conductors cross each other, the evaluation result “P” is obtained with respect to all of the following items: the peak position and the minimum value for the Scc21 transmission characteristic, and the respective transmission coefficients at 20 GHz, 30 GHz, and 40 GHz for the Sdd21 characteristic.
By contrast, for Sample 1, the first coil conductor and the second coil conductor have an overlapping portion, and thus the evaluation result “F” is obtained with respect to the peak position for the Scc21 transmission characteristic, and the respective transmission coefficients at 30 GHz and 40 GHz for the Sdd21 characteristic.
Therefore, for Sample 1, with respect to Sdd21, that is, the transmission characteristic for differential-mode components, the transmission coefficient is −3 dB at a frequency of less than or equal to 30 GHz. This means that high-frequency signal components are attenuated. With respect to Scc21, that is, the attenuation characteristic for common-mode components, the peak position is 21.50 GHz. This means that common-mode noise components are not sufficiently attenuated at higher frequencies at or above, for example, 25 GHz.
Although the present disclosure has been described above with reference to the illustrated embodiment, various other modifications are possible within the scope of the present disclosure.
For example, in one alternative embodiment, a single coil conductor included in at least one of the first and second coils may be divided in two into a first portion and a second portion, the first portion and the second portion may be disposed respectively along a first interface and a second interface, which are different interfaces between non-conductor layers, and the first portion and the second portion may be connected by a via-conductor. In this case, overlap between the first coil conductor and the second coil conductor coil may be observed with the first and second portions of the above-mentioned single coil conductor combined.
While preferred embodiments of the disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the disclosure. The scope of the disclosure, therefore, is to be determined solely by the following claims.
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