JPH04364710A - Chip transformer - Google Patents

Abstract

PURPOSE:To improve the coupling coefficient of primary and secondary electrodes and the insulation resistance in order to reduce stray capacity between coils. CONSTITUTION:A plurality of magnetic sheets 1 to 10 in which specified conductor patterns 1b and 2a to 10a are formed on the surface, and at the same time the patterns 1b and 2a to 10a are connected to form a pair of primary and secondary electrodes and the sheets are calcined as one body to produce a chip transformer 50. In these steps, cavities 31 to 40 are also prepared on a part of surfaces of the patterns 1b and 2a to 10a, or any cavities are prepared among the conductor patterns.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer chip transformer having a coiled conductor path, and more particularly to a chip transformer with improved insulation and coupling coefficient.

0002

[Conventional example] Conventionally, as an example of a multilayer chip transformer in which a coil-shaped conductor path is formed using a magnetic green sheet (magnetic sheet) formed by the green sheet method, the one shown in FIGS. something is known. FIG. 12 shows a cross-sectional view taken along line A-A in FIGS. 10 and 11. This chip transformer 20 is made by laminating a plurality of magnetic sheets 1 to 10 on which a predetermined conductive pattern as described below is formed, and a dummy magnetic sheet 11 on which no conductive pattern is formed, and firing them into one piece. conductor patterns 2a, 4a, 6a, 8a, 10a
constitute a primary side electrode, and conductor patterns 1b, 3a, 5
A, 7a, and 9a constitute a secondary side electrode.

As shown in FIGS. 10 and 11, conductor patterns 1a and 1b are formed on the surface of a magnetic sheet 1. As shown in FIGS. One ends of the conductor patterns 1a and 1b extend from the center of the opposing sides to edges slightly closer to the corners and are exposed to the outside, and serve as lead-out portions 12a and 12b for the primary and secondary electrodes of the transformer, respectively. ing. Further, at the other ends of the conductor patterns 1a, 1b, through holes 21a,
21b is formed.

A magnetic sheet 2 is laminated adjacent to the magnetic sheet 1 on the side opposite to the side on which the dummy magnetic sheet 11 without a conductive pattern is laminated. On the surface of the magnetic sheet 2, an L-shaped conductor pattern 2a is formed. At one end of this conductor pattern 2a, an electrode 2b connected to the through hole 21a of the take-out part 12a of the magnetic sheet 1 is formed, and at the other end, the conductor of the magnetic sheet 4, which will next form the primary electrode, is formed. A through hole 22a is formed to connect to the pattern 4a. Further, a through hole 22b is formed in the magnetic sheet 2 at a position away from the conductive pattern 2a and in a position opposite to the through hole 21b of the magnetic sheet, and a through hole electrode is formed around the through hole 22b. 22c is formed. Note that this through-hole electrode is formed around the through-hole in order to improve the connectivity of the through-hole portion.

[0005] Also, magnetic sheets 3, 4, 5, 6, 7,
8 and 9 are sequentially laminated next to the magnetic sheet 2. On the surface of each magnetic sheet, symmetrical L-shaped or L-shaped conductor patterns 3a, 4a, 5a, 6a, 7a, 8 are alternately arranged.
a and 9a are formed respectively. Electrodes 3b, 4b, 5b, 6b, 7b, 8b,
9b is formed, and a through hole 23b is formed at the other end, respectively.
, 24a, 25b, 26a, 27b, 28a, and 29b are formed. Furthermore, conductor patterns 3a, 4a, 5
Through holes 23a, 24b, 25a, 2 are provided at positions away from a, 6a, 7a, 8a, 9a and not in contact with each other.
6b, 27a, 28b, and 29a are formed, and through-hole electrodes are formed around them.

[0006] Conductor patterns 10a and 10b are formed on the surface of the magnetic sheet 10. Conductor pattern 10a
, 10b extend from the center of each opposing side to an edge slightly closer to the corner and are exposed to the outside, and serve as lead-out portions 13a and 13b for the primary and secondary electrodes of the transformer, respectively. Further, the other ends of the conductor patterns 10a and 10b are
Electrodes 14a and 14b are formed, respectively, and are connected to conductor patterns 8a and 9a, respectively.

Furthermore, a plurality of dummy magnetic sheets 11 are stacked adjacent to the conductive pattern 10. Then, the conductor pattern 2a of the magnetic sheet 2 is connected to the through hole 22a.
, 23a to the conductor pattern 4a of the magnetic sheet 4, and similarly conductor patterns 6a, 8a, 10a.
are connected in sequence to form two turns of the primary electrode of the transformer. Further, the conductor pattern 1b of the magnetic sheet 1 is connected to the conductor pattern 3a of the next magnetic sheet 3 through the through holes 21b and 22b, and further connected to the conductor pattern 3a of the magnetic sheet 5 through the through holes 23b and 24b. 5a, and constitutes one turn of the secondary electrode. Similarly, conductor patterns 7a and 9a are further connected in sequence to form two turns of the secondary electrode of the transformer. In this way, a spiral bifilar coil is formed by alternately and repeatedly stacking the conductor pattern of the primary electrode and the conductor pattern of the secondary electrode.

[0008]

[Problems to be Solved by the Invention] In order to increase the coupling coefficient between the primary side electrode and the secondary side electrode in the above chip transformer, it is necessary to
Although it is necessary to make the distance d (FIG. 12) between the next-side and secondary-side electrodes as short as possible, there is a problem in that when d is shortened, the insulation between the primary-side and secondary-side electrodes deteriorates. Furthermore, when the dielectric constant of the magnetic sheet is large, stray capacitance between the primary conductor pattern and the secondary conductor pattern increases, which may cause noise in a high frequency range.

The present invention was made in view of the problems of the prior art described above, and it improves the coupling coefficient between the primary and secondary electrodes, improves the insulation resistance, and reduces the stray capacitance between the wires. The purpose is to provide a chip transformer that achieves the following.

0010

[Means for Solving the Problems] The present invention laminates a plurality of magnetic sheets each having a predetermined conductor pattern formed on their surface, bakes them into one, and connects the conductor patterns to form a pair of primary The chip transformer connected to the electrode and the secondary electrode is characterized in that a cavity is formed in a part of the surface of the conductor pattern, or a cavity is formed between the conductor patterns.

[0011] The above-mentioned cavity can be formed by printing a diffusing agent on top and bottom of the conductive pattern, or by stacking a magnetic sheet printed with a diffusing agent sandwiched between magnetic sheets printed with a conductive pattern. It is formed by diffusing it into the magnetic material during firing and leaving voids on the printed surface. The part of the surface of the conductor pattern mentioned above may be either one of the conductor patterns forming the primary side or the secondary side electrode, or a part of the surface of the conductor pattern.

0012

[Operation] According to the chip transformer of the present invention, a diffusing agent that diffuses into the magnetic material during firing is printed on top and bottom of the conductor pattern on the surface of the magnetic sheet, and the magnetic sheets are laminated and integrated by firing. , either by forming cavities scattered at the interface between the conductor pattern and the magnetic layer, or by sandwiching and laminating a magnetic sheet with a diffusion agent printed between the magnetic sheets on which the conductor pattern has been formed, and then baking and integrating the diffusion agent. is diffused into the magnetic material during firing, forming cavities between the conductor patterns. In this way, by forming a cavity in a part of the surface of the conductor pattern or in the magnetic material between the conductor patterns, the magnetic flux generated across the primary conductor pattern and the secondary conductor pattern can be increased. It is possible to improve the coupling coefficient. In addition, due to the low dielectric constant layer (ε=1) due to the cavity,
It reduces floating capacitance between the primary and secondary electrodes and improves insulation resistance. Furthermore, this improvement in insulation resistance is achieved not only by the effect of the cavities but also by the diffusion of the diffusing agent into the magnetic material to form a highly insulating compound.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the chip transformer according to the present invention will be described below with reference to the drawings. Portions corresponding to the above-mentioned prior art will be described with the same reference numerals. 1 and 2 are diagrams illustrating a manufacturing process of a part of a chip transformer according to a first embodiment of the present invention. In the figure, 50 is a chip transformer, and this chip transformer 50 includes a plurality of magnetic sheets 1 to 10 on which a predetermined conductor pattern is formed, and a dummy magnetic sheet without a conductor pattern, as described below. 11 are laminated and baked to form a single conductor pattern 2a, 4a, 6a, 8a, 10a.
constitute a primary side electrode, and conductor patterns 1b, 3a, 5
A, 7a, 9a constitute a secondary side electrode, and each conductor pattern 1b, 2a, 3a, 4a, 5a, 6a, 7a, 8a,
Hollows 31, 32, 33 are formed around 9a and 10a, respectively.
34, 35, 36, 37, 38, 39, and 40 are formed.

The step of forming a cavity at the interface between the conductive pattern and the magnetic sheet is as follows:
, 2, 3, 4, 5, 6, 7, 8, 9, and 10, respectively, to form a diffusion agent layer by printing a diffusion agent at a position corresponding to the conductor pattern of the predetermined primary or secondary electrode. Then, a conductive pattern is formed on this surface, and a diffusing agent is further printed on this surface to form an upper layer of the diffusing agent. Then, layer
During firing, it is diffused into the magnetic sheet and integrated by firing.

A diffusing agent is printed on the magnetic sheet 1 at a position corresponding to the main part of the conductor pattern 1b to form a diffusing agent layer. After the diffusing agent is cured, a conductor pattern 1b is formed. Further, a diffusing agent is printed on the surface of the conductive pattern 1b to form an upper layer of the diffusing agent (not shown). As shown in FIG. 2, a diffusing agent is printed on the magnetic sheet 2 at a position corresponding to the conductor pattern 2a of the primary electrode to form a diffusing agent layer 32a. Next, after the diffusing agent has hardened, conductor patterns 2a and the like are formed on this surface. Next, as shown in FIG. 3, a diffusing agent is printed on the surface of the conductor pattern 2a to form an upper layer 32b of the diffusing agent. magnetic sheet 3,
Similarly, diffusion agent layers 33a and 34a are applied to 4.
are formed, conductor patterns 3a and 4a are formed, and then,
An upper layer 3 of the diffusing agent is placed on the surface of the conductor patterns 3a, 4a.
3b and 34b are formed.

Similarly, although not shown, conductor patterns 5 of other magnetic sheets 5, 6, 7, 8, 9, and 10 are formed.
A diffusion agent layer is formed by printing a diffusion agent at positions corresponding to a, 6a, 7a, 8a, 9a, and 10a, respectively. Conductor patterns 5a, 6a, and 7 are placed over each layer of the diffusing agent, respectively.
a, 8a, 9a, and 10a are formed, respectively. A diffusing agent is printed on a portion of the surface of each conductor pattern to form a diffusing agent layer. Then, dummy magnetic sheets 11 are laminated above and below the magnetic sheets 1 to 10, and are fired and integrated to form the chip transformer 50 shown in FIG.

FIGS. 4 and 5 are diagrams illustrating a chip transformer according to a second embodiment of the present invention. In the figure,
51 is a chip transformer, and this chip transformer 51 is
Magnetic sheets 15 and 1 are printed with a required diffusing agent between predetermined magnetic sheets of a plurality of magnetic sheets 1 to 10 on which predetermined conductive patterns are formed, as described below.
Either No. 6 or No. 17 are laminated and fired into one piece. and between conductor patterns 1b and 4a, and between 2a and 3a, respectively.
Between, between 4a and 5a, between 3a and 6a, between 5a and 8a, 6a
and 7a, between 8a and 9a, and between 7a and 10a, cavities 41, 42, 43, 44, 45, respectively.
, 46, 47, 48 are formed.

In order to form a cavity between the conductor patterns according to this embodiment, conductor patterns 1b and 4a and conductor patterns 2a and 2a are connected so that cavities are formed between conductor patterns 1b and 4a and conductor patterns 2a and 3a. A magnetic sheet 15 having diffusion agent layers 15b, 15a, etc. formed in a substantially U-shape at a position opposite to magnetic sheet 3a is laminated between magnetic sheets 2 and 3. Further, a magnetic sheet 16 having a layer 16a of a diffusing agent formed thereon at a position facing the conductive patterns 3a and 4a is placed between the magnetic sheets 3 and 4 so as to form a cavity between the conductive patterns 3a and 4a. layered in between. Further, a layer 17a of a diffusing agent is applied to these conductor patterns 4a and 5a and conductor patterns 3a and 6a so as to form cavities between conductor patterns 4a and 5a and conductor patterns 3a and 6a.
, 17b, etc., is laminated between the magnetic sheets 4 and 5. Note that this magnetic sheet 1
7 is the same as the magnetic sheet 15 rotated by 180 degrees.

Furthermore, in the same way, although not shown,
Magnetic sheets 15, 16, and 17, which are obtained by rotating the magnetic sheet 16 by 180 degrees, are laminated between the other magnetic sheets 5 and 6, between 6 and 7, between 7 and 8, and between 8 and 9, respectively. Magnetic sheet 1 is placed between magnetic sheets 1 and 2 and between 9 and 10, respectively.
6 rotated 180° and stacked. Then, they are fired and integrated in the same manner as above.

The magnetic sheet described above is formed from a slurry of granular material such as Ni--Zn ferrite by a printing method, a green sheet method, or the like. Further, the conductive pattern and electrodes formed on the surface of this magnetic sheet are formed by printing, coating, sputtering, or the like using Ag, Ag-Pd, or the like. Examples of the diffusing agent that diffuses into the magnetic material to form cavities include glass materials such as silicate glass and borosilicate glass, and Bi2 O3,
Examples include low melting point compounds such as Li2C03 and LiF. One or more types of these may be contained. In addition, to increase the strength of the cavity, it is possible to form a mesh-like cavity by impregnating the cavity with a highly insulating resin and filling the cavity after forming the cavity, or by adding a compound (Al2 O3, ZrO2, etc.) that does not react with glass to the diffusing agent. There are various methods of forming it.

FIGS. 6 and 7 are diagrams illustrating a third embodiment of the chip transformer according to the present invention. In this example,
This is an example in which cavities are formed scattered at the interface between the conductive pattern and the magnetic layer. First, a magnetic sheet was produced by a doctor blade method using a Ni-Zn ferrite raw material with an initial magnetic permeability μ=300. A diffusing agent or Ag
- A Pd conductor pattern was printed. External electrode is Ag-Pd
using electrodes. The chip transformer 52 of the third embodiment has cavities 82 and 83 formed around predetermined conductor patterns 62a and 63a, respectively.

This chip transformer 52 is made by baking a chip, which is a stack of magnetic sheets 62 and 63 on which a conductive pattern is formed by stacking them on a magnetic sheet 61 and a layer of a diffusing agent is printed, at 960° C. for 2 hours. do. 3.7mm
A chip transformer measuring 3.2 mm x 1.2 mm was fabricated. Conductor patterns 62a and 63a are formed on the magnetic sheets 62 and 63, respectively, and diffusion agent layers 62b and 63b are printed above and below the magnetic patterns, respectively. When these are laminated and fired, a cavity 8 is formed as shown in FIG.
2 and 83 are formed at the interface between the conductor patterns 62a and 63a and the magnetic layer, respectively. After firing this chip transformer 52, the distance d between the primary and secondary electrodes is 60 μm, the line width of the conductor pattern is 500 μm, and the thickness of the conductor pattern is 10 μm.
It was μm.

FIGS. 8 and 9 are diagrams illustrating a fourth embodiment of a chip transformer according to the present invention. This embodiment is an example in which a cavity is formed between conductor patterns. The chip transformer 53 has diffusion agent layers 84, 85, and 86 formed above the conductor pattern 62a, between the conductor patterns 62a and 63a, and under the conductor pattern 63a, respectively. This chip transformer 53 consists of magnetic sheets 6 stacked one above the other.
Magnetic sheets 64, 65, and 66 each having patterns 64a, 65a, and 66a printed with a diffusing agent on the upper, middle, and lower sides of magnetic sheets 62 and 63 each having a conductive pattern formed between them are stacked. to form chips. The other parts were fired and integrated in the same manner as in the third embodiment to obtain a chip transformer 53. The inductance values, coupling coefficients, and insulation resistance values between the primary and secondary conductor patterns of the chip transformers 52 and 53 thus obtained were measured and shown in Tables 1 and 2. Table 1 shows the case where cavities are formed scattered at the interface between the conductive pattern layer and the magnetic layer as shown in FIG. 6, and Table 2 shows the case where cavities are formed between the conductive patterns as shown in FIG. It is.

[0024]

[Table 1]

[0025]

[Table 2]

As shown in Table 1, when cavities are formed scattered at the interface between the conductor pattern layer and the magnetic layer, the coupling coefficient is improved and the insulation resistance between the primary and secondary conductor patterns is improved compared to the monitor. was completed. In sample No. 3, the diffusion of glass into the ferrite was insufficient, cavities were partially formed, and almost no improvement in insulation resistance was observed.

As shown in Table 2, when a cavity was formed between the conductor patterns, the coupling coefficient and the insulation resistance between the primary and secondary conductor patterns were improved compared to the monitor. In this case as well, samples No. 9 and No. 10 in which cavities were only partially formed showed almost no improvement in insulation resistance. By forming the cavity, the stray capacitance could be reduced to about 1/2 of that in the case where no cavity was formed.

Furthermore, the cavity formed in the above-described process can be impregnated with a highly insulating resin. Filling the cavity has the advantage of increasing the strength of the cavity and improving moisture resistance. Further, as described in the above process, by adding a compound such as Al2 03 or ZrO2 that does not react with glass to the diffusing agent, it is possible to prevent the cavities from fusion during firing. In addition, although three types of magnetic sheets printed with a diffusing agent were described in the above embodiment, the present invention is not limited to this embodiment, and other shapes may be used.

[0029]

[Effects of the Invention] According to the chip transformer according to the present invention,
By forming a cavity in a completely non-magnetic material (air) layer (μ = 1), the coupling coefficient between the primary and secondary electrodes is improved, and the floating due to the low dielectric constant (air) layer (ε = 1) is improved. A reduction in capacitance and an improvement in insulation resistance are obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view taken along line A-A in FIGS. 2 and 3 of a first embodiment of a chip transformer according to the present invention.

FIG. 2 is an exploded perspective view illustrating the configuration of a part of the manufacturing process of the chip transformer of this embodiment.

FIG. 3 is an exploded perspective view illustrating another part of the manufacturing process of the chip transformer according to the present embodiment.

4 is a cross-sectional view taken along the line AA in FIG. 5 of a second embodiment of the chip transformer according to the present invention.

FIG. 5 is an exploded perspective view illustrating a part of the configuration of this embodiment.

6 is a sectional view taken along the line AA in FIG. 7 of a third embodiment of the chip transformer according to the present invention.

FIG. 7 is an exploded perspective view of this embodiment.

8 is a sectional view taken along the line AA in FIG. 9 of a fourth embodiment of the chip transformer according to the present invention.

FIG. 9 is an exploded perspective view of this embodiment.

FIG. 10 is an exploded perspective view of a part of the configuration of a conventional example.

FIG. 11 is an exploded perspective view of another part of the configuration of the conventional example.

FIG. 12 is a sectional view taken along the line AA in FIGS. 10 and 11 of the conventional example.

[Explanation of symbols]

1 to 10 Magnetic sheet 1b, 2a to 10a Conductor pattern 12a, 12b Take-out part 31-40, 41-48 Hollow

Claims (1)

[Claims] 1. A plurality of magnetic sheets each having a predetermined conductor pattern formed on the surface are laminated, and the conductor patterns are connected to form a pair of primary and secondary electrodes, and then fired and integrated. A chip transformer characterized in that a cavity is formed in a part of the surface of the conductor pattern or a cavity is formed between the conductor patterns.