JP3097296B2 - Multilayer T-type LC filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated T-type LC filter composed of L and C for removing noise, and more particularly to a laminated T-type LC filter having good frequency characteristics in a wide frequency band.

[0002]

2. Description of the Related Art Conventionally, as a laminated LC filter (for example, a T-type LC filter) composed of a magnetic layer and a dielectric layer including two or more coils, for example, the one shown in FIG. 6 is known. The T-type LC filter 100 includes magnetic ceramic green sheets (hereinafter referred to as magnetic sheets) 101 to 104 and dielectric ceramic green sheets (hereinafter referred to as dielectric sheets) 105 to 105 configured as described below.
108 and the magnetic sheets 109 to 112 are laminated, pressure-bonded and integrally sintered. Magnetic sheet 101-
104 forms the inductor element portion (A). The magnetic sheet 101 is a dummy sheet, and the magnetic sheet 102
Are provided with an electrode 113 for forming a coil, an extraction electrode 114, and a through hole 115, respectively. In the magnetic material sheet 103, the electrode 116 for forming the coil is formed from the receiving portion 117 facing the through hole 115 to the through hole 118.
The magnetic material sheet 104 is provided with through holes 119 so as to provide electrical conduction between the two. Dielectric sheets 105 to 10
8 forms the capacitor element portion (B). The dielectric sheet 105 is a dummy sheet and has a through hole 120. An electrode 121 for forming a capacitor is provided on the dielectric sheet 106, a through hole 123 is provided at one end, and a receiving portion 122 is provided at a position facing the through hole 120 at the other end. The dielectric sheet 107 includes a ground electrode 124 for forming a capacitor and a through hole 126.
And the extraction electrodes 12 at both ends of the ground electrode 124.
5a and 125b are exposed to the outside from the edge of the dielectric sheet 107. The dielectric sheet 109 has a through hole 128. Magnetic sheet 109-112
Form another inductor element (C). The magnetic sheet 109 is a dummy sheet.
28, and the coil-forming electrode 129 is provided on the magnetic sheet 110 with the receiving portion 130 facing the through hole 128.
And the through holes 131 are electrically connected to each other. The magnetic sheet 111 includes a coil forming electrode 132, a receiving portion 133 of the through hole 131, and an extraction electrode 134.
And the magnetic sheet 112 is a dummy sheet without electrodes. Then, the sheets 101 to 112 are sequentially laminated, pressure-bonded and integrally sintered to obtain a laminated T-type LC filter 100 having an equivalent circuit shown in FIG.

As an example similar to the above-mentioned laminated T-type LC filter, an inductor element portion composed of an alternating laminate of a magnetic layer made of a magnetic material sheet such as ferrite and an electrode for coil formation, and TiO ₂ , BaTiO _2, etc. A composite LC in which a capacitor element portion composed of an alternating laminate of dielectric layers and electrodes composed of a dielectric sheet as a main component is superposed and integrally sintered.
Filters are known (for example, Japanese Utility Model Publication No. 60-178).
No. 95). As in the case of this composite LC filter, in order to integrally sinter a magnetic material and a dielectric material made of completely different materials, unless the firing shrinkage rate and the thermal expansion coefficient of both materials are strictly matched, layers will peel off and cracks will occur. However, it is very difficult to obtain an integral sintered body. Therefore, it has been proposed to form a capacitor element portion by using a dielectric constant of a magnetic material itself such as ferrite without using a dielectric material for the capacitor element portion (see the above-mentioned publication). Since both the inductor element portion and the capacitor element portion are made of the same magnetic material, there is an advantage that mismatch in firing shrinkage does not occur during integral sintering.

[0004]

However, in the composite LC filter in which the capacitor element portion is formed by utilizing the dielectric constant of the conventional magnetic material such as ferrite, the dielectric constant of the magnetic material such as ferrite is low. It is difficult to obtain a small and large capacitance, and a large number of capacitor electrodes with a large area are required to obtain a predetermined capacitance.
There is a problem that the size and cost increase. Further, in order to increase the inductance of the inductor element portion, it is desirable to use a magnetic material such as ferrite having a large magnetic permeability. However, the ferrite having a large magnetic permeability rapidly decreases in a high frequency. As a result, the inductance at high frequencies is reduced, and the noise removing effect is reduced. Ferrite having a small magnetic permeability has a small decrease in magnetic permeability up to a high frequency, but in order to obtain a large inductance, it is necessary to increase the number of turns of the coil, resulting in an increase in size and cost.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has an advantage that the inductor element portion and the capacitor element portion can be easily joined, processed easily, and have excellent frequency characteristics. It is an object of the present invention to provide a laminated T-type LC filter having the following.

[0006]

According to the present invention, there is provided a laminated T type L according to the present invention.
The C filter is formed by laminating a magnetic ceramic green sheet on which an electrode for forming a coil is formed to form two portions of an inductor element portion, and a magnetic material and a dielectric on which an electrode for forming a capacitor and an electrode for forming an additional inductor are formed. The ceramic green sheets of the mixed material are laminated to form an LC composite element portion, and the LC composite element portion is laminated between the inductor element portions. One end of each of the coil forming electrodes and the LC composite element portion The one end of the additional inductor forming electrode is connected via a through hole.

[0007]

According to the present invention, a magnetic sheet and a dielectric sheet made of completely different materials, which are constituted as described above, are not sintered together, but are mixed with a magnetic sheet and a dielectric material. Since the material sheet and adjacent are sintered together,
The firing shrinkage and the coefficient of thermal expansion of the two can be made close to each other, and the occurrence of peeling and cracking of the layer is reduced. The inductor function consists of an inductor element made of a magnetic material sheet, and the capacitor function uses a relatively large dielectric constant of a mixture of a magnetic material and a dielectric material. The number of electrodes can be reduced or the area of the electrodes can be reduced, and the size can be reduced. Furthermore, the magnetic characteristics of the LC composite element portion forming the capacitor made of the mixed material sheet have excellent high-frequency characteristics, a small decrease in the magnetic permeability at high frequencies, and noise with good high-frequency characteristics due to the addition of an additional inductor. An LC filter for removal can be obtained.

[0008]

Embodiments of the present invention will be described below. First, the following Ni-Zn ferrite and a powder of a Pb-based relaxor dielectric are mixed to form a mixed material of a magnetic substance and a dielectric substance. 1) Ni-Zn ferrite: Ni _0.34 Zn _0.57 Cu _0.16
Fe _1.95 O _3.97 2) Pb-based relaxer: 0.95 [Pb (Mg _1/3
Nb _2/3) O _3] -0.05PbTiO ₃ magnetic and dielectric of each of a pre-calcined, milled powder. By appropriately selecting the calcination conditions for the magnetic material and the dielectric material and mixing them, the firing shrinkage curve of the mixed material can be made the same as that of the magnetic material alone. The magnetic powder and the dielectric powder of the above 1) and 2) whose calcination conditions and pulverization conditions were respectively adjusted were weighed at the weight ratio shown in Table 1, mixed with a binder and a solvent, and mixed with a ceramic green sheet as a mixed material. (Hereinafter referred to as a mixed material sheet). The mixed material sheet is laminated and pressure-bonded, punched into a ring and a disk, and fired at 930 ° C. to obtain a sample. The characteristics of this sample were measured, and the results are shown in Table 1.
Shown in

[0009]

[Table 1]

As is clear from the measurement results in Table 1 of the characteristics of the sample, it is clear that ferrite only (No. 1) and dielectric simple (N
o. 6) and shrinkage ratio and sintering start temperature are different,
The difference is small in the mixed material (No. 4) containing up to 60% of the dielectric. That is, the mixed material is more dielectric simple (No.
Better matching by integral sintering with the magnetic material (No. 1) than 6).

Next, an embodiment of a laminated T-type LC filter according to the present invention will be described with reference to FIGS. In the drawing, reference numeral 1 denotes a T-type LC filter, which is an inductor element portion 3 formed by forming electrodes on a magnetic sheet and laminating and pressing.
And an LC composite element part 4 including an additional inductor formed by forming electrodes on the mixture material sheet and laminating and crimping, and another inductor element part 5 formed by forming electrodes on the magnetic material sheet and laminating and crimping. The filter element 2 is press-bonded and sintered integrally to form a filter element 2, and external electrodes 6, 7, 8,
9 is provided. 10 to 14 and 24 to 28 are magnetic sheets, and 15 to 23 are mixed material sheets.

As shown in FIG. 2, the inductor element section 3 has coils 29, 32 and 35 formed on the surfaces of the magnetic sheets 11, 12 and 13, respectively. One end 30 of the electrode 29 of the magnetic sheet 11 is exposed to the outside to form a lead electrode, and the other end is connected to one end 33 of the lower electrode 32 via a through hole 31. Similarly, the other end 34 of the electrode 32 is connected to one end 36 of the electrode 35 thereunder through a through hole,
A coil is formed, and the magnetic material sheets are laminated and crimped in this manner to form the inductor element portion 3.

Similarly, as shown in FIG. 3, another inductor element portion 5 is formed. An electrode 58 for forming a coil is formed on the surface of the magnetic material sheet 25, and one end of the electrode 58 is provided with the magnetic material sheet 24 on the upper surface and the mixed material sheet 2.
3, 22, 21 through holes 57, 56,
The other end 60 of the mixture sheet 20 is connected to one end 51 of the additional inductor 50 via 55 and 52, and the other end 60 is connected to one end 62 of the electrode 61 of the lower magnetic sheet 26 via a through hole. The other end 63 of the magnetic sheet 27 is connected to one end 65 of the electrode 64 via a through hole at the other end 63, and the other end 66 of the electrode 64 forms a lead electrode exposed to the outside.

As shown in FIG. 3, the LC composite element section 4 located between the two inductor element sections 3 and 5 is provided on the surfaces of the mixture sheets 17, 18, 20 and 21 for forming capacitors. The electrodes 42, 44, 49 and 53 are formed to face each other. Here, the electrodes 42, 53 are ground electrodes, and the ends 43a, 43b, 54a, 5
At 4b, it is exposed to the outside as an extraction electrode. From the capacitor electrode 44 facing the ground electrode 42, a meandering electrode 45 for forming an additional inductor extends to an end 46. Similarly, a meandering electrode 50 for forming an additional inductor extends from the capacitor electrode 49 facing the other ground electrode 53 to the through hole at the end 51. The end 46 of the meandering electrode 45 on the surface of the mixture material sheet 18 is passed through the mixture material sheets 17, 16, 15 and the through holes 41, 40, 39, and 38 of the magnetic material sheet 14 to form the inductor element portion. It is connected to one end 37 of the third coil electrode 35. Similarly, the mixture material sheet 2
The end 51 of the other meandering electrode 50 on the surface of the surface 0 is mixed with the mixture material sheets 21, 22, 23 and the magnetic material sheet 24 thereunder.
Through the respective through holes 52, 55, 56 and 57 of the coil electrode 5 of the other inductor element portion 5.
8 is connected to one end 59.

An equivalent circuit diagram of the LC filter having the above configuration is as follows.
As shown in FIG. Here, L ₁ and L ₂ are the inductances formed in the inductor element portions 3 and 5, respectively.
L ₃ and L _4, an inductance formed on the additional inductors of the LC composite element unit 4, respectively. Also, C
Reference numeral ₁ denotes a capacitance formed in the capacitor of the LC composite element unit 4. In the laminated T-type LC filter, when an additional coil electrode for connecting the coil-forming electrode and the capacitor-forming electrode is formed on the ceramic green sheet for mixed material, high-frequency characteristics can be improved.

FIG. 7 shows the T-type LC of the above embodiment and the conventional example.
The noise removal effect of the noise filter is shown by the relationship between the insertion loss and the frequency characteristics. In the conventional T-type LC noise filter shown in FIG. 2A, the insertion loss that rapidly increases from around 10 MHZ becomes gentle from around 100 MHZ, and the noise removing effect deteriorates. On the other hand, in the curve shown by (b) of the present invention, the insertion loss sharply increases up to around several hundred MHZ, has a large insertion loss in a high frequency range, and has an excellent noise removing effect. This is an effect of the inductor added to the LC composite element section 4. The mixture of magnetic and dielectric materials has excellent magnetic high-frequency characteristics and, with the addition of an additional inductor, can maintain high impedance up to high frequencies.
Effective for removing noise at high frequencies.

In the above embodiment, the coil forming electrode of the inductor element portion is shown in a meandering shape. However, the shape, the number of turns, the number of sheets, and the like of the coil forming electrode are not limited to the above embodiment. Can be appropriately selected according to the conditions. In addition, the present invention is not limited to the above-described embodiment, and can be modified by a person skilled in the art without changing the gist thereof.
It can be changed and implemented.

[0018]

According to the laminated T-type LC filter of the present invention, by using a mixture of a magnetic material and a dielectric material in the capacitor forming portion, a dielectric constant larger than that of the magnetic material alone can be obtained. Can be configured with a small electrode area or a small number of capacitor elements, cost can be reduced, downsizing can be achieved, and the mismatch of shrinkage during integral sintering of the inductor element with the magnetic material can be reduced. Therefore, it is possible to obtain a highly reliable LC filter having an excellent noise removing effect by preventing defects such as cracks and peeling.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating an embodiment of a laminated T-type LC filter according to the present invention.

FIG. 2 is an exploded perspective view of a part of the embodiment.

FIG. 3 is an exploded perspective view of another part of the embodiment.

FIG. 4 is an equivalent circuit diagram of the laminated T-type LC filter according to the present invention.

FIG. 5 is an equivalent circuit diagram of a conventional laminated T-type LC filter.

FIG. 6 is an exploded perspective view illustrating a conventional example.

FIG. 7 is a graph showing the insertion loss frequency characteristics of the laminated T-type LC filter of the present invention and the conventional example.

[Brief description of reference numerals]

REFERENCE SIGNS LIST 1 laminated T-type LC filter 3,5 inductor element part 4 LC composite element part 6,7,8,9 external electrode 10-14 magnetic sheet 15-23 mixture material sheet 24-28 magnetic sheet 45,50 additional inductor Electrode for formation Patent applicant Attorney, Murata Manufacturing Co., Ltd. Attorney, Kesa Machida

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-97211 (JP, A) JP-A-2-232915 (JP, A) JP-A-3-155609 (JP, A) JP-A-3-3 140006 (JP, A) JP-A-1-196113 (JP, A) JP-A-3-39823 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H03H 7/075 H01F 17 / 00 H01F 15/00 H01G 4/40

Claims (1)

(57) [Claims] 1. A magnetic ceramic green sheet on which an electrode for forming a coil is formed is laminated to form two portions of an inductor element portion, and a magnetic material and a dielectric on which an electrode for forming a capacitor and an electrode for forming an additional inductor are formed. A ceramic green sheet of a body mixture is laminated to form an LC composite element part, and the LC composite element part is laminated between the inductor element parts, and one end of each of the coil forming electrodes and the LC composite element part 3. A laminated T-type LC filter, wherein one end of an electrode for forming an additional inductor is connected through a through hole.