Patent Grant
12131854
This application claims benefit of priority to Japanese Patent Application No. 2020-132928, filed Aug. 5, 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 a first coil and a second coil that are 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 suppress 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.
To address the above-mentioned technical problem, a first characteristic feature of preferred embodiments of the present disclosure resides in that the first coil has a path length L1, the second coil has a path length L2, and the sum of the path lengths L1 and L2 is less than or equal to 3.30 mm.
Further, according to preferred embodiments of the present disclosure, 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, which is an interface between the first plurality of non-conductor layers. The second coil includes a second coil conductor disposed along a second interface, which is an interface between the second plurality of non-conductor layers and different from the first interface along which the first coil conductor is disposed, and a second characteristic feature of the preferred embodiments resides in that the first coil conductor and the second coil conductor have a spacing between each other of greater than or equal to 6 μm and less than or equal to 26 μm (i.e., from 6 μm to 26 μm) in a direction in which the plurality of non-conductor layers are stacked.
According to preferred embodiment of the present disclosure, the stray capacitance between the first coil and the second coil can be reduced. This helps to improve the high-frequency characteristics of the common-mode choke coil.
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 a 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. The first end face 9 and the second end face 10 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. As a result, an inductance due to the first coupling part 29 can be reduced, and high-frequency characteristics can be thus improved.
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. As a result, an inductance due to the second coupling part 30 can be reduced, and high-frequency characteristics can be thus improved.
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 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 allows for improved high-frequency characteristics of the common-mode choke coil 1.
In connection with the relatively small number of turns of each coil conductor, a first characteristic feature of the common-mode choke coil 1 resides in that the sum of path lengths L1 and L2 is less than or equal to about 3.30 mm, the path length L1 being the path length of the first coil 11, the path length L2 being the path length of the second coil 12. Due to this characteristic feature, the stray capacitance generated between the first coil 11 and the second coil 12 can be reduced. This helps to ensure that, at high frequencies, the common-mode choke coil 1 can transmit differential-mode signals and suppress common-mode noise components, which allows for improved high-frequency characteristics of the common-mode choke coil 1.
In
Likewise, in
In actuality, the above-mentioned path length measurement is performed as described below. First, the multilayer body 2 is ground in the stacking direction to expose the third connection end portion 25 and the second coupling part 30. The path length of the third connection end portion 25, and the path length of the second coupling part 30 are then measured with a measuring microscope. The grinding is further allowed to proceed to expose the second coil conductor 18 and the fourth connection end portion 26, and the path length of the second coil conductor 18 and the path length of the fourth connection end portion 26 are then measured with the measuring microscope. The grinding is further allowed to proceed to expose the first coil conductor 17 and the second connection end portion 24, and the path length of the first coil conductor 17 and the path length of the second connection end portion 24 are then measured with the measuring microscope. The grinding is further allowed to proceed to expose the first connection end portion 23 and the first coupling part 29, and the path length of the first connection end portion 23 and the path length of the first coupling part 29 are then measured with the measuring microscope.
Meanwhile, another multilayer body 2 is prepared. The multilayer body 2 is ground in a direction orthogonal to the stacking direction of the multilayer body 2 to expose the first via-conductor 27 and the second via-conductor 28. The respective lengths of the first and second via-conductors 27 and 28 in the stacking direction are then measured with the measuring microscope.
Subsequently, the sum of the lengths measured as mentioned above, that is, the length of the third connection end portion 25, the length of the second coupling part 30, the length of the second via-conductor 28, the length of the second coil conductor 18, and the length of the fourth connection end portion 26, is found and taken as the path length of the second coil 12. Likewise, the sum of the length of the first connection end portion 23, the length of the first coupling part 29, the length of the first via-conductor 27, the length of the first coil conductor 17, and the length of the second connection end portion 24 is found and taken as the path length of the first coil 11.
Preferably, as clearly illustrated in
As is apparent from
A second characteristic feature of the common-mode choke coil 1 resides in that, as illustrated in
By contrast, if the first coil conductor 17 and the second coil conductor 18 have a spacing D between each other of less than about 6 μm in the stacking direction of the non-conductor layers 3, 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. Consequently, as will be appreciated from the exemplary experiment described later, the frequency (peak position) at which the Scc21 transmission characteristic has a minimum value is less than, for example, about 29 GHz, and it is not possible to ensure that the transmission coefficient be made less than or equal to, for example, about −23 dB at the frequency (peak position) at which the Scc21 transmission characteristic has a minimum value.
By contrast, if the first coil conductor 17 and the second coil conductor 18 have a spacing D between each other of greater than about 26 μm in the stacking direction of the non-conductor layers 3, 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 conducted 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 predetermined proportions, 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 put 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 put into the ball mill and mixed together to thereby 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 60 to 90° C. and a pressure of about 80 to 120 MPa to thereby 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 multilayer body 2 that has undergone firing, or each discrete multilayer structure that has not undergone firing yet is preferably placed into a rotating barrel together with media, and rotated to thereby round or chamfer its edge and corner portions.
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 800 to 820° C. 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, the common-mode choke coil 1 has the first and second characteristic features. According to the first characteristic feature, the first coil 11 has the path length L1, the second coil 12 has the path length L2, and the sum of the path lengths L1 and L2 is less than or equal to about 3.30 mm According to the second characteristic feature, the first coil conductor 17 and the second coil conductor 18 have a spacing D 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) in the stacking direction of the non-conductor layers 3. These characteristic features help to ensure that at higher frequencies, the common-mode choke coil 1 can transmit differential-mode signals and sufficiently suppress common-mode noise components. An experiment conducted to verify this is now described below.
As illustrated in Table 1, common-mode choke coils corresponding to Sample (indicated as “S” in Table 1) 1 to Sample 16 are prepared by varying the following values: “1st coil/SG1”, “2nd coil/SG2”, “spacing between first and second coil conductors/D”, “1st coil path length/L1”, and “2nd coil path length/L2”. 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 Each of the first and second coil conductors of the common-mode choke coil corresponding to each sample has a line width of 0.018 mm.
Referring now to
In Table 1, “spacing between first and second coil conductors/D” represents the spacing D illustrated in
For each of the common-mode choke coils corresponding to Samples 1 to 16, 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
Table 1 also illustrates “sum of coil path lengths/L1+L2”, which is calculated based on the “1st coil path length/L1” and the “2nd coil path length/L2”.
Referring to Table 1, for each of Samples 5 to 16 with the “sum of coil path lengths/L1+L2” of less than or equal to 3.30 mm, the frequency (peak position) at which the transmission characteristic Scc21 has a minimum value can be made greater than or equal to 28.3 GHz. By contrast, for each of Samples 1 to 4 with the “sum of coil path lengths/L1+L2” of greater than or equal to 3.33 mm, the peak position of the Scc21 transmission characteristic is located below 28.3 GHz, and is less than or equal to 27.9 GHz.
In particular, among Samples 5 to 16 with the “sum of coil path lengths/L1+L2” of less than or equal to 3.30 mm, for samples excluding Sample 7, the “spacing between first and second coil conductors/D” is greater than or equal to 6 μm and less than or equal to 26 μm (i.e., from 6 μm to 26 μm).
In other words, Samples 5, 6, and 8 to 16 satisfy the condition that the “sum of coil path lengths/L1+L2” be less than or equal to 3.30 mm, and the condition that the “spacing between first and second coil conductors/D” be greater than or equal to 6 μm and less than or equal to 26 μm (i.e., from 6 μm to 26 μm). For each of Samples 5, 6, and 8 to 16 mentioned above, the frequency (peak position) at which the Scc21 transmission characteristic has a minimum value can be further increased to greater than or equal to 29.8 GHz. For Sample 7, the transmission coefficient at the peak position at which the Scc21 transmission characteristic has a minimum value is −20.3 dB. In this regard, for each of Samples 5, 6, and 8 to 16, the above-mentioned transmission coefficient can be further decreased to less than or equal to −23.1 dB.
Attention is now directed to the Sdd21 transmission characteristic. It can be appreciated that for Samples 5, 6, and 8 to 16, the transmission coefficient at 20 GHz can be made greater than or equal to −1.83 dB, the transmission coefficient at 30 GHz can be made greater than or equal to −1.80 dB, and the transmission coefficient at 40 GHz can be made greater than or equal to −2.58 dB, indicating that these samples allow differential-mode signals to be effectively transmitted without much attenuation.
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, the path length of the single coil conductor, which constitutes a portion of the coil path length, may be regarded as the path length with the first portion of the coil conductor, the via-conductor, and the second portion of the 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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