JPH04329607A - Laminar chip transformer - Google Patents

Abstract

PURPOSE:To provide a laminar chip transformer having a very loose electrostatic coupling between its primary and secondary coils. CONSTITUTION:A primary coil 8 is constituted with internal conductor patterns 6a-6d included in a group 1 for constituting the primary coil. A secondary coil 13 is constituted with internal conductor patterns 11a-11d included in a group 2 for constituting the secondary coil. An earth electrode sheet 3 is sandwiched between the groups 1, 2 for constituting the primary and secondary coil respectively. On the earth electrode sheet 3, provided is an earth electrode 16, whose size is nearly equal to the primary and secondary coil 8, 13, and on which slits 18 are so provided that the ring-like earth electrode 16 forms no closed circuit.

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 that can be used as various transformers, common mode choke coils, and the like.

0002

2. Description of the Related Art FIG. 6 shows a conventional multilayer chip transformer B. This is an internal conductor pattern 5 with a coil shape on the surface.
A plurality of magnetic sheets 52a on which 1a to 51c are formed
52c are stacked, and the internal conductor patterns 51a to 51c are electrically connected to each other through the through holes 53 to form the primary coil 54, and similarly, coiled internal conductor patterns 55a to 55c are formed on the surface. A plurality of magnetic sheets 56a to 56c are stacked, and each internal conductor pattern 55a to 55 is connected via a through hole (not shown).
A secondary coil 57 is formed by electrically connecting the c comrades, and a plurality of plain magnetic sheets (
dummy sheets) 58 are laminated and integrated by pressure firing. FIG. 7 shows an equivalent electrical circuit diagram of this multilayer chip transformer B. Primary coil 54 and secondary coil 5
7, and a capacitance CL is generated between each of the internal conductor patterns 51a to 51c of the primary coil 54 and between the internal conductor patterns 55a to 55c of the secondary coil 57.

0003

However, in such a multilayer chip transformer B, the primary coil 54 and the secondary coil 57 are insulated by only one magnetic sheet 52c. Stray capacitance C between the primary coil 54 and the secondary coil 57 through 52c
occurs.

[0004] Due to the existence of this stray capacitance C, conventional multilayer chip transformers have the following problems: ■ Resonance occurs at low frequencies;
Due to resonance at low frequencies, the frequency characteristics of the chip transformer do not extend to the high frequency side, resulting in poor frequency characteristics.■ Poor conversion efficiency between the primary and secondary sides. ■ Noise flows from the primary coil to the secondary coil. On the other hand, there was a problem in that it passed directly from the secondary coil to the primary coil.

The present invention has been made in view of the drawbacks of the conventional examples described above, and its purpose is to extremely reduce the electrostatic coupling between the primary coil and the secondary coil in a multilayer chip transformer. There is a particular thing.

[0006]

[Means for Solving the Problems] The multilayer chip transformer of the present invention has magnetic sheets and internal conductor patterns laminated,
A laminated chip transformer in which a laminated chip is formed by laminated magnetic sheets, and a primary coil and a secondary coil are formed by an internal conductor pattern, wherein both coils and a It is characterized by forming ground electrodes of approximately the same size and providing a slit in the ground electrodes so that the ground electrodes do not close in an annular shape.

[0007]

[Operation] In the present invention, since a ground electrode having approximately the same dimensions as both coils is provided between the primary coil and the secondary coil, by grounding the ground electrode, the primary coil and the secondary coil can be connected. It is possible to obtain an electrostatic shielding effect between the two coils, and the stray capacitance between the two coils can be extremely reduced.

On the other hand, since no ground electrode is provided in the parts corresponding to the inside of the primary coil and secondary coil,
The magnetic coupling between the primary and secondary coils is not shielded by the ground electrode.

Furthermore, if the earth electrode is annular, an excitation current is excited in the annular earth electrode by electromagnetic induction from the primary coil, and this excitation current weakens the magnetic coupling between the primary coil and the secondary coil. It will be done. but,
In the present invention, a slit is provided in the ground electrode to prevent it from becoming annular, so that no excitation current flows and there is no fear that magnetic coupling will be inhibited.

Therefore, according to the present invention, the electrostatic coupling between the primary coil and the secondary coil can be made extremely small without weakening the magnetic coupling between the two coils. As a result, the performance of the multilayer chip transformer has been improved, ■ Resonance does not occur up to high frequencies, and ■ Resonance does not occur up to high frequencies, which allows the frequency characteristics of the chip transformer to be extended to the high frequency side, resulting in good frequency characteristics. ■ Can be
Conversion efficiency between the primary and secondary sides has been improved, making it possible to prevent noise from passing directly from the primary coil to the secondary coil, and conversely from the secondary coil to the primary coil.

[0011]

[Embodiment] Fig. 1 is a perspective view showing the state before lamination of the multilayer chip transformer A of the first embodiment, Fig. 2 is a perspective view showing the completed product of the multilayer chip transformer A, and Fig. 3 is a perspective view of the multilayer chip transformer A of the first embodiment. This is an equivalent electrical circuit. The structure of this multilayer chip transformer A will be explained together with the manufacturing method.

As shown in FIG. 1, a multilayer chip transformer A
consists of a primary coil configuration group 1, a secondary coil configuration group 2, a ground electrode sheet 3, and a dummy sheet 4. The primary coil configuration group 1 is made by printing an electrode paste (for example, a conductive paste mainly composed of Ag and Pd, or a conductive paste mainly composed of Ag) on the surface of the ferrite green sheets 5a to 5d. Forming internal conductor patterns 6a to 6d of turns to 0.5 turns, and electrically conducting internal conductor patterns 6a to 6d located above and below through through holes 7 provided in ferrite green sheets 5a to 5c. A spiral primary coil 8 is formed by this, and extraction electrodes 9 to which both ends of the primary coil 8 are connected are arranged at the edges of the ferrite green sheets 5a and 5d. Similarly, for the secondary coil configuration group 2, electrode paste is printed on the surface of the ferrite green sheets 10a to 10d to form internal conductor patterns 11a to 11d of 0.75 turns to 0.5 turns. Through hole 1 provided at ~10c
Internal conductor patterns 11a to 1 located above and below via 2
A spiral secondary coil 13 is formed by electrically connecting the 1d to each other, and the secondary coil 13
The extraction electrodes 14 provided at both ends of the green sheets 10a and 10d are arranged at the edges of the green sheets 10a and 10d. In addition, the earth electrode sheet 3 is made by printing electrode paste on the surface of the ferrite green sheet 15 to form the primary and secondary coils 8 and 13.
A substantially annular ground electrode 16 having substantially the same shape (projected image) and dimensions as the ferrite green sheet 15 is formed, and is electrically connected to two extraction electrodes 17 arranged at the edge of the ferrite green sheet 15. However, the ground electrode 16 is divided into two by a slit 18 provided between both extraction electrodes 17 so as not to close in an annular shape. The dummy sheet 4 is a plain ferrite green sheet 19.

[0013] However, from the bottom, a plurality of dummy sheets 4
, the secondary coil configuration group 2, the earth electrode sheet 3, the primary coil configuration group 1, and a plurality of dummy sheets 4 are laminated in this order and pressure-molded from above and below by press crimping, and each layer's ferrite green sheets 5a to 5d, 10a-10d, 15, 1
The laminated chip 20 is obtained by press-bonding the 9 pieces together. However,
In reality, as shown in Figure 1, the elements are not manufactured individually, but the internal conductor patterns for multiple elements are formed on each large ferrite green sheet (mother sheet). After each large ferrite green sheet is pressure-bonded as described above, it is cut and separated into individual elements to obtain the laminated chip 20. Next, the laminated chip 20 in which the ferrite green sheets and internal conductor patterns are alternately laminated is fired, and after firing, the end face of the laminated chip 20 is barrel polished to expose each internal extraction electrode 9, 14, 17 on the end face. let After this, electrode paste is applied and baked on the surface of the laminated chip 20,
As shown in FIG. 2, the primary coil external electrode 21 is connected to the extraction electrode 9 of the primary coil 8, and the secondary coil external electrode 22 is connected to the extraction electrode 14 of the secondary coil 13.
and the grounding external electrodes 23 connected to each extraction electrode 17 of the grounding electrode 16 are formed so as not to overlap with each other.

A multilayer chip transformer is manufactured in which a primary coil 8, a ground electrode 16, and a secondary coil 13 are formed by internal conductor patterns in a multilayer chip 20 in which ferrite sheets obtained by firing the ferrite green sheets are stacked. A ground electrode 16 is disposed between the primary coil 8 and the secondary coil 13, and the ground electrode 16 is formed to have substantially the same dimensions as both coils 8 and 13.

In this multilayer chip transformer A, since the earth electrode 16 is grounded through the earth external electrode 23,
The equivalent circuit is a circuit as shown in FIG. 3 in which the primary coil 8 and the secondary coil 13 are each grounded via the capacitor C2, and the static between the primary coil 8 and the secondary coil 13 is reduced due to the electrostatic shielding effect of this capacitor C2. Electrical coupling is prevented, and the primary coil 8 and secondary coil 13 are electrostatically independent. On the other hand, since the ground electrode 16 is provided with a slit 18,
No excitation current flows, and the magnetic coupling between both coils 8 and 13 does not decrease.

FIG. 4 shows the structure of a ground electrode in another embodiment of the present invention. This is earth electrode 1
6 extraction electrodes 17 are combined into one, and correspondingly, a slit 18 is also provided at one location.

FIG. 5 shows the structure of a ground electrode in yet another embodiment of the present invention. In this case, the lead electrodes 17 of the ground electrode 16 are provided at four locations, and the slits 18 are also provided at a total of four locations between the lead electrodes 17. In this case, the slit 18 of the ground electrode 16
Although it is possible to have only one location, if a slit 18 is provided in the ground electrode 16 between each extraction electrode 17 as in this embodiment, it is possible to pass the slit from one extraction electrode 17 through the earth electrode 16 to another. An excitation current flows to the extraction electrode 17, and this excitation current causes the primary coil 8 and the secondary coil 13 to
It is possible to prevent the magnetic coupling force from becoming weaker. The same applies when the number of extraction electrodes is 3 or 5 or more.

In the above embodiment, a multilayer chip transformer was manufactured by laminating ferrite green sheets with internal conductor patterns formed on their surfaces, bonding them under pressure, and then firing them. However, the multilayer chip transformer of the present invention In addition to such a manufacturing method, a transformer can also be manufactured by, for example, alternately printing magnetic paste to form a magnetic sheet and electrode paste to form an internal conductor pattern, and firing the printed laminate.

[0019]

According to the present invention, the electrostatic coupling between the primary coil and the secondary coil can be extremely reduced without inhibiting the magnetic coupling between the two coils. For this reason,
■Resonance does not occur up to high frequencies;■By not generating resonance up to high frequencies, the frequency characteristics of the chip transformer can be extended to the high frequency side, resulting in better frequency characteristics.
■The conversion efficiency between the primary side and the secondary side is improved, and ■noise can be prevented from passing from the primary coil to the secondary coil, and conversely from the secondary coil to the primary coil.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a state before lamination in an embodiment of the present invention.

FIG. 2 is an external perspective view of the embodiment same as above.

FIG. 3 is an equivalent electric circuit diagram of the same as above.

FIG. 4 is a plan view showing a ground electrode in another embodiment of the present invention.

FIG. 5 is a plan view showing a ground electrode in still another embodiment of the present invention.

FIG. 6 is a perspective view of a conventional example before lamination.

FIG. 7 is an equivalent electric circuit diagram of the same as above.

[Explanation of symbols]

5a to 5d, 10a to 10d, 15, 19 Ferrite green sheets 6a to 6d, 11a to 11d Internal conductor pattern 8
Primary coil 13 Secondary coil 16 Earth electrode 18 Slit 20 Laminated chip

Claims (1)

[Claims] 1. A laminated chip transformer in which a magnetic sheet and an internal conductor pattern are laminated, a laminated chip is formed by the laminated magnetic sheet, and a primary coil and a secondary coil are formed by the internal conductor pattern, A multilayer chip characterized in that a ground electrode having approximately the same dimensions as both coils is formed between the primary coil and the secondary coil in the multilayer chip, and a slit is provided in the ground electrode so that the ground electrode does not close in an annular shape. Trance.