JPH04236406A - Thin film transformer - Google Patents

Abstract

PURPOSE:To prevent magnetic saturation, and obtain a thin film type transformer which has a small external size and is excellent in power transferring characteristics in a high frequency region, by constituting a magnetic yoke by combining a magnetic thin film excellent, in high frequency characteristics and a substrate containing magnetic fine grains. CONSTITUTION:A magnetic thin film yoke part 21 is laminated on a magnetic substrate yoke part 11, via an insulator layer (low permeability substrance) 31. A primary winding 13 is formed so as to wind the yoke part 11. A secondary winding 23 is formed so as to wind the yoke part 21. The insulator layer 31 composed of SiO2, Si3N4, polyimide, etc., electrically insulates the primary winding 13 and the secondary winding 23. Since the permeability of the layer 31 is low, the magnetic flux generated by the primary winding 13 does not leak, and flows into the magnetic thin film yoke part 21. The magnetic flux generated by a primary current in the primary winding 13 passes the magnetic substrate yoke part 11, and flows into the magnetic thin film yoke part 21.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film transformer using a magnetic thin film.

0002

[Prior art] Magnetic transformers are used for switching power supplies,
Power transformers such as DC-DC power supplies, step-up transformers,
It is used as a transformer for weak signal voltage amplification. BACKGROUND ART As the devices become smaller, there is a demand for space-saving in power supply units mounted on electronic devices, particularly portable electronic devices, etc., and the magnetic transformers used therein also need to be smaller. Furthermore, in order to save space in the entire power supply section, it is necessary to satisfy characteristics requirements such as improved switching frequency, and a magnetic transformer with performance corresponding to this is required.

It is known that the magnetic yoke of a conventional bulk type transformer can be made into a thin film transformer (
Japanese Patent Publication No. 55-13416, Japanese Patent Publication No. 61-2082
10). By making the magnetic yoke thin, the transformer can be made smaller and thinner, and the property of the magnetic thin film, which has good high frequency magnetic properties, can be utilized.

However, since the magnetic yoke of such a thin film transformer is entirely of a thin film type, it has the disadvantage that saturation of the magnetic yoke is likely to occur at high output. Further, Japanese Patent Application Laid-Open No. 62-214604 describes that a coil pattern is formed on a sheet that is sintered to become a magnetic material, and the coil patterns are laminated to form a laminated transformer.

Furthermore, Japanese Patent Laid-Open No. 62-198146 discloses that wiring is printed in a zigzag manner on the front and back sides of a substrate on which a magnetic layer is formed via through holes to form a primary winding and a secondary winding. It is stated that.

[0006]

SUMMARY OF THE INVENTION The present invention provides a thin film transformer that has small external dimensions, can operate at high output, and has excellent power transmission characteristics in a high frequency region.

[0007]

[Means for Solving the Problems] In the thin film transformer of the present invention, a yoke is formed by laminating a magnetic thin film made of a soft magnetic material on a magnetic substrate in which magnetic fine particles are dispersed in a nonmagnetic material. One of the windings and the secondary winding is interlinked with the magnetic flux passing through the magnetic substrate yoke section, and the other winding is interlinked with the magnetic flux passing through the magnetic thin film yoke section, or the magnetic flux passing through the magnetic substrate yoke section - magnetic It is characterized by interlinking with the magnetic flux passing between the thin film yoke parts.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an exploded perspective view showing an embodiment of a thin film type transformer according to the present invention, and FIG. 2 is a longitudinal sectional view. A magnetic thin film yoke portion 21 is laminated on the magnetic substrate yoke portion 11 via an insulator layer (low magnetic permeability material) 31 to form a magnetic yoke. A primary winding 21 is provided on the magnetic substrate yoke portion 11 so as to be wound around the primary winding 21 . On the other hand, the magnetic thin film yoke portion 21 is provided with a secondary winding 23 wound around the magnetic thin film yoke portion 21 .

The magnetic substrate yoke portion 11 is made of a plastic substrate such as polyimide or the like in which fine particles of sendust, carbonyl iron, YIG, magnetic ferrite, etc.
A ceramic substrate such as GG or non-magnetic ferrite is used. Such a magnetic fine particle dispersion has good high frequency characteristics and allows the substrate to be relatively thick, so that magnetization saturation is unlikely to occur even when the saturation magnetic flux density of the magnetic substrate yoke portion 11 is relatively small.

The magnetic thin film yoke portion 21 is made of Co-Zr-N
It is formed from an amorphous film such as B, a soft magnetic thin film such as iron nitride, pure iron, permalloy, or a laminated film thereof, and has a high saturation magnetic flux density.

[0011] The insulator layer 31 made of SiO2, Si3N4, polyimide, etc. electrically insulates the primary winding 13 and the secondary winding 23, and has low magnetic permeability, so that the primary winding The magnetic flux generated at 13 flows into the magnetic thin film yoke portion 21 without leaking.

The magnetic thin film yoke portion 21 (soft magnetic thin film) is
It can be formed by a vacuum film forming method such as a sputtering method or an evaporation method, a plating method, or a screen printing method using a suitable binder after a soft magnetic material is once made into fine particles.

[0013] The primary winding 13 is formed from conductive foil or the like. The secondary winding 23 is formed by photolithography or the like. In terms of the magnetic circuit, a closed magnetic path is formed by a magnetic yoke consisting of a magnetic substrate yoke portion 11 and a magnetic thin film yoke portion 21, as shown by arrows indicating magnetic flux in FIG.

Furthermore, the primary winding 13 is connected to the magnetic thin film yoke portion 2.
1 and the secondary winding 23 is wound around the magnetic substrate yoke portion 11, similar effects can be obtained.

As shown in FIG. 2, as in a normal magnetic transformer, magnetic flux (indicated by an arrow) generated by the primary current from the primary winding 13 passes through the magnetic substrate yoke portion 11 constituting the magnetic yoke. It flows into the magnetic thin film yoke portion 21 . In the secondary winding 23 arranged around the magnetic thin film yoke part 21, a voltage proportional to the time change of the magnetic flux passing through the magnetic thin film yoke part 21 is generated, and a current flows according to an appropriate load, which is applied to the primary side. Power is transferred to the secondary side.

FIG. 3 is an exploded perspective view showing another embodiment of the present invention, and FIG. 4 is a longitudinal sectional view thereof. A primary winding 13 is embedded in the magnetic substrate yoke portion 11 on the side where the magnetic thin film yoke portion 21 is in contact with the magnetic substrate yoke portion 11 . The insulator layer 31 shown in FIG. 1 is not required, making manufacturing easier.

As shown in FIG. 4, a closed magnetic path is formed as in the case of FIG. 2, and power on the primary side is transmitted to the secondary side. In this case as well, the secondary winding may be disposed on the magnetic substrate yoke portion 11 and the primary winding 13 may be disposed on the magnetic thin film yoke portion 21.

FIG. 5 is a longitudinal sectional view showing another embodiment of the thin film type transformer of the present invention. This embodiment is the same as the embodiments shown in FIGS. 3 and 4, except that magnetic fine particles (indicated by dots) are not distributed on the surface layer 11a of the magnetic substrate yoke above the buried primary winding 13. be. This prevents leakage of magnetic flux to the magnetic substrate yoke surface layer portion 11a. The distribution of magnetic fine particles in the magnetic substrate yoke surface layer 11a may be made sparser than in other portions, or the magnetic fine particles may be distributed from sparse to dense in the thickness direction of the magnetic substrate yoke portion 11 from the surface layer 11a toward the back side. The same effect as above can be obtained even if a concentration gradient is provided so that

In each of the above embodiments, when the primary winding 13 is provided on the magnetic substrate yoke portion 11, a relatively large current can be passed through the primary winding 13, so the winding dimensions when boosting the voltage are Suitable for optimization. In addition, the magnetic flux generated by the primary winding is transmitted throughout the magnetic substrate yoke portion 11, and magnetic saturation is difficult to occur even at low saturation magnetic flux density, and since the magnetic thin film yoke portion 21 has a high saturation magnetic flux density, , magnetic saturation is also less likely to occur.

FIG. 6 is a perspective view showing another embodiment of the thin film type transformer of the present invention, and FIG. 7 is an explanatory diagram showing the flow of magnetic flux (winding wires are not shown). Further, in FIG. 6, only a part of the secondary winding 23 is shown.

A primary winding 13 is similarly wound around the magnetic substrate yoke portion 11 shown in FIG. A magnetic thin film yoke portion 21 is provided on the magnetic substrate yoke portion 11 and is divided into three parts in a direction perpendicular to the flow direction of magnetic flux. A secondary winding is wound around the magnetic thin film yoke portion 21 .

The magnetic flux generated by the primary current of the primary winding 13 passes through the magnetic substrate yoke portion 11 constituting the magnetic yoke, and is divided into three magnetic thin film yoke portions 21 and flows therein. Therefore, compared to the configuration shown in FIG. 3, magnetic saturation is less likely to occur even at higher outputs.

Note that as the magnetic substrate yoke portion 11, one having the configuration shown in FIG. 1 or FIG. 5 may be used. FIG. 8 is an exploded perspective view showing still another embodiment of the thin film type transformer of the present invention, and FIG. 9 is a longitudinal sectional view thereof.

As in FIG. 2, a primary winding 13 is embedded in the magnetic substrate yoke portion 11. The primary winding 13 is not wound at the center of the magnetic substrate yoke portion 11, and the winding direction is reversed on both sides. Magnetic substrate yoke part 1
1, a spiral secondary winding 23 embedded in an electrically insulating and non-magnetic support substrate 33 is laminated,
Furthermore, a magnetic thin film yoke portion 21 made of a soft magnetic material
are layered. Note that a through hole 35 is provided in the support substrate 33 at an approximately central portion of the spiral secondary winding 23, and the magnetic substrate yoke portion 1 is formed in this through hole 35.
1 and the magnetic thin film yoke portion 21 are in direct contact with each other.

The magnetic flux generated by the primary current from the primary winding 13 flows through the magnetic substrate yoke portion 1 constituting the magnetic yoke.
1 and further passes through the magnetic thin film yoke portion 21 to form a closed magnetic path. At this time, current flows through the spiral secondary winding 23 arranged to interlink with this closed magnetic path in accordance with an appropriate load, and the power applied to the primary is transmitted to the secondary.

[0026] In this embodiment as well, due to the same effects as in each of the above embodiments, it is easy to optimize the dimensions of the primary winding 11, and magnetic saturation is less likely to occur. FIG. 10 is a longitudinal cross-sectional view showing another embodiment, in which the secondary winding 23 is directly mounted on the magnetic substrate yoke portion 11 by photolithography or the like.
It is the same as FIGS. 8 and 9 except that .

In the embodiments shown in FIGS. 8 to 10, the magnetic substrate yoke shown in FIG. 1 or 5 can also be used. Further, in each of the above embodiments, the primary winding and the secondary winding may be arranged in opposite yoke parts.

FIG. 11 shows an example of the coupling constant of the thin film type transformer of the present invention shown in FIG. It can be seen that the output is higher in the high frequency range than the conventional bulk type transformer or all-thin film type transformer.

Therefore, it can be used as a magnetic transformer at 1 MHz or higher in switching power supplies, etc., where high frequency is being designed to improve efficiency, contributing to higher efficiency of power supplies, and further downsizing the product. Weight reduction can be achieved.

[0030]

According to the present invention, by constructing a magnetic yoke by combining a magnetic thin film with excellent high frequency characteristics and a substrate containing magnetic fine particles, magnetic saturation can be prevented, the external dimensions are small, and power in the high frequency region can be reduced. A thin film transformer with excellent transmission characteristics can be obtained.

Both the substrate magnetic yoke portion and the magnetic thin film yoke portion exhibit high inductance up to the high frequency range, and since the capacitance between both windings is reduced and the resonant frequency is increased, the characteristics in the high frequency range are improved.

[0032] Furthermore, since only one of the primary and secondary windings is wound around the magnetic substrate yoke near the magnetic thin film, the winding can be made as densely as possible considering only insulation. Therefore, the binding constant can be further increased.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing an embodiment of a thin film transformer of the present invention.

FIG. 2 is a longitudinal sectional view of the embodiment shown in FIG. 1;

FIG. 3 is an exploded perspective view showing another embodiment of the present invention.

FIG. 4 is a longitudinal sectional view of the embodiment shown in FIG. 3;

FIG. 5 is a longitudinal sectional view of still another embodiment.

FIG. 6 is a perspective view showing an embodiment of the present invention.

FIG. 7 is an explanatory diagram showing the flow of magnetic flux in the embodiment shown in FIG. 6;

FIG. 8 is an exploded perspective view showing another embodiment of the present invention.

FIG. 9 is a longitudinal cross-sectional view of the embodiment shown in FIG. 8;

FIG. 10 is a longitudinal sectional view showing still another embodiment.

FIG. 11 is a graph showing the relationship between coupling constant and frequency for the thin film transformer of the present invention and a conventional product.

[Explanation of symbols]

11 Magnetic substrate yoke part 13 Primary winding 21 Magnetic thin film yoke part 23 Secondary winding 31 Insulator layer 33 Support board 35 Through hole

Claims (8)

[Claims] Claim 1: A yoke is formed by laminating a magnetic thin film made of a soft magnetic material on a magnetic substrate in which magnetic fine particles are dispersed in a non-magnetic member, and a yoke is formed by laminating a magnetic thin film made of a soft magnetic material on a magnetic substrate in which magnetic fine particles are dispersed in a non-magnetic member. The winding interlinks with the magnetic flux passing through the inside of the magnetic substrate yoke section, and the other winding interlinks with the magnetic flux passing through the magnetic thin film yoke section or the magnetic flux passing between the magnetic substrate yoke section and the magnetic thin film yoke section. A thin film type transformer featuring: 2. The thin film transformer according to claim 1, wherein the one winding is wound around the magnetic substrate yoke portion. 3. The thin film type transformer according to claim 2, wherein said one winding is buried so as not to be exposed on the surface of the magnetic substrate yoke portion in contact with the magnetic thin film yoke portion. 4. The thin film transformer according to claim 3, wherein a portion of the magnetic substrate yoke portion in which the one winding is buried has a smaller amount of magnetic fine particles distributed than other portions. 5. The magnetic thin film yoke portion is divided into a plurality of parts in a direction intersecting the flow direction of magnetic flux.
4. The thin film transformer according to any one of 4. 6. The thin film transformer according to claim 1, wherein the other winding is wound around the magnetic thin film yoke portion. 7. The other winding according to claim 1, wherein the other winding wire is spirally wound in the direction in which the surface of the magnetic thin film yoke portion extends, and is sandwiched between the magnetic substrate yoke portion and the magnetic thin film yoke portion. 5. The thin film transformer according to any one of 4 to 4. 8. The thin film transformer according to claim 7, wherein the other winding is supported by a support substrate.