JP3135941B2 - High frequency thin film transformer and high frequency thin film inductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency thin-film transformer and a high-frequency thin-film inductor which are suitable for a converter, a switching power supply and the like, and are formed in a small size by using a conductive pattern and have excellent high-frequency characteristics.

[0002]

2. Description of the Related Art In recent years, there has been a severe demand for downsizing and weight reduction of electronic device components, and downsizing is an essential issue even in switching power supplies that can obtain high-quality power. Miniaturization has been promoted by making components such as transformers, inductors and capacitors smaller. For semiconductor parts and capacitor parts, LS
As represented by I and multilayer ceramic capacitors, thin-film technology has been used from an early stage and has sufficiently responded to the demand for downsizing of components. On the other hand, transformers and inductors have been most difficult to miniaturize so far, and it is difficult to suppress an increase in loss due to the increase in frequency. For this reason, it is no exaggeration to say that the volume of the high-frequency switching power supply is determined by the transformer in particular. In recent years, thin film transformers studies using thin film forming techniques to respond to high frequencies is advanced, began to develop small power with an increased switching frequency to MH _Z bandwidth is highly desirable.

FIG. 3 is a schematic structural view of a thin film transformer manufactured by a conventional thin film forming technique. In the figure, 1 is a substrate, 2 is an insulating layer, 3 is a magnetic film, 4 is a primary conductor, and 5 is a secondary conductor. Conventionally, this type of thin film transformer has been manufactured as follows. That is, a lower conductor layer is formed on a substrate 1 having an insulating surface by a thin film forming method such as sputtering, and is patterned to form a strip-shaped lower conductor. , SiO ₂ , S
It is formed of iO, Al ₂ O ₃ , polyimide resin or the like, flattened, and then a magnetic film layer is formed by sputtering or the like, and patterned to form a rectangular magnetic film 3. After forming the upper conductor layer, a strip-shaped upper conductor is formed by patterning. The upper conductor and the lower conductor are connected through a through hole formed by etching, and a primary conductor 4 and a secondary conductor 5 are formed so as to surround the magnetic film 3, and a transformer is manufactured.

FIG. 4 is a sectional view showing the structure of the central magnetic film 3 and the primary conductor 4 and the secondary conductor 5 of the above-mentioned conventional thin film transformer. The point of increasing the frequency by such a conventional thin film transformer is to reduce the eddy current loss at a high frequency by forming a thin conductor and a magnetic layer using a thin film forming technique such as sputtering.

[0005]

However [0007] By the conventional art, the reduction of just losses simply thin strip of a magnetic layer, the conductive layer of the thin film transformer is not sufficient, the area where the switching frequency exceeds several MH _Z In this case, there is a problem that characteristics are significantly deteriorated. As shown in FIG. 5 (a schematic diagram of the generation of leakage magnetic flux in a sample having only the center magnetic film 3), the magnetic flux in the core at the center is changed by the demagnetizing field at the end of the magnetic material into the conductors 3 and 4.
And a state appears to be intersected. As a result, an eddy current is generated in the conductive wires 3 and 4 because magnetic flux penetrates perpendicularly from the plane direction into the thin conductive wires 3 and 4, and the conductor resistance at high frequencies increases rapidly. 6 (lower magnetic film 6).
In order to improve the inductance, as shown in FIG.
When the conductor is installed, the conductor resistance increases from a lower frequency. This increase in conductor resistance at high frequencies is due to Q
Values and efficiency are significantly reduced, and the upper limit of usable frequencies is determined.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to reduce an increase in conductor resistance at high frequencies and to improve usable frequencies and efficiency.

[0007]

In order to achieve the above object, in the high-frequency thin film transformer and the high-frequency thin film inductor of the present invention, the band forming the conductive wire is used.
A slit in the longitudinal direction of the conductor is inserted into the
It is characterized in that a part or the whole of the body is subdivided into strips .

[0008]

In the high-frequency thin-film transformer and high-frequency thin-film inductor of the present invention, a part or the whole of the conductor constituting the thin-film transformer or the thin-film inductor is divided into strip-shaped conductors to cut off the surface where the magnetic flux intersects. The area is reduced, the generation of eddy current is reduced, the increase in conductor resistance at high frequencies is suppressed, and the efficiency can be improved and the usable frequency can be increased.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. 1A and 1B are a plan view showing an embodiment of the present invention and a sectional view taken along line AA 'of FIG. In the present embodiment, the conductor of the conventional example shown in FIG. 4 has a flat cross section, but is formed by dividing the conductor into strips in the longitudinal direction of the conductor. In the figure, 1 is a substrate, 2 is an insulating layer, 3 is a center magnetic film, 4 is a partially divided primary conductor,
Reference numeral 5 denotes a partially divided secondary conductor, and reference numeral 6 denotes a lower magnetic film.
The manufacturing method of this embodiment is performed in the same process as that of the conventional example shown in FIG. 3, but by using a mask provided with a slit when patterning the conductor layer, the conductors for forming the conductors 4 and 5 can be formed. The layer is partially divided into strips. That is, a magnetic film layer is formed on the substrate 1 by sputtering or the like, and is patterned to form a rectangular lower magnetic film 6, on which an insulating layer 2 is formed by photoresist, SiO ₂ , SiO, Al
_{It is made of 2} O ₃ , polyimide resin, etc., flattened, and then a lower conductor layer is formed by a thin film forming technique such as sputtering, and is patterned to form a strip-shaped lower conductor, which is then insulated again. Layer 2 is formed as described above. After flattening this, a magnetic film layer is formed by sputtering or the like, and patterned to form a rectangular central magnetic film 3. After that, an insulating layer 2 is further formed thereon, and an upper conductor layer is formed. Is formed, and finally the insulating layer 2 is formed. The upper conductor and the lower conductor are connected through a through-hole formed by etching, and the primary conductor 4 and the secondary conductor 5 are formed so as to surround the central magnetic film 3, thereby producing a transformer.

The operation of the embodiment constructed as described above will be described. In the high-frequency thin-film transformer of the present embodiment, the conductors around the ends of the magnetic material composed of the magnetic films 3 and 6 among the conductors of the primary conductor 4 and the secondary conductor 5 constituting the thin-film transformer are strip-shaped conductors. , The cross-sectional area of the plane where the magnetic flux intersects is reduced. When the cross-sectional area is reduced in this way,
The occurrence of eddy current is reduced, and the increase in conductor resistance at high frequencies is suppressed. As a result, efficiency is improved,
It can be used up to high frequencies.

The operation of the above embodiment will be described below in comparison with the conventional example shown in FIG. FIG. 2 compares the frequency characteristics of inductance and the conductor resistance of the primary winding (primary conductor 4) of the thin film transformer for the two types of transformers. FIG. 1A shows the case of the conventional thin film transformer of FIG. 6, and FIG. 2B shows the case of the thin film transformer according to the present embodiment. Initially, the value of the conductor resistance is almost the same in the low frequency range, but in the conventional thin film transformer of (1), the value is 1 MHz.
Whereas the starting to increase from around _Z, in the thin film transformer embodiment of (2) is the degree to which gradually increased and maintained a low resistance up to several tens MH _Z. On the other hand, for the inductance, the conventional case of (1), in accordance with the increase of conductor resistance, to the order of several MH _Z to inductance is reduced, several tens MH _Z in the embodiment of (2) Up to frequency characteristics have been improved. When evaluated by the Q value, it is clear that the value is improved by one digit or more compared to the conventional example.

In the above embodiment, the conductor is divided by slitting only the conductor near the end of the magnetic body. However, it goes without saying that the same effect can be obtained by dividing the entire conductor. . It is apparent that the same effect can be obtained by subdividing the conductors even in a thin film inductor having no secondary winding (secondary conductor) in the thin film transformer structure of this embodiment. Further, the present invention is naturally applicable to a thin film transformer or a thin film inductor having a structure in which a magnetic flux and a conducting wire intersect with each other. Thus, the present invention
Various applications can be made along the gist and various embodiments can be taken.

[0013]

As is clear from the above description, according to the high-frequency thin film transformer and the high-frequency thin film inductor of the present invention, it is possible to reduce the conductor resistance at high frequencies, and to obtain the characteristics of higher frequency and higher efficiency. It is possible to provide a small transformer or inductor having the following.

[Brief description of the drawings]

FIG. 1A is a plan view showing the structure of one embodiment of the present invention, and FIG.

FIG. 2 is a comparative characteristic diagram showing the frequency dependence of the inductance and resistance of the embodiment and the conventional example.

FIG. 3 is a schematic structural view of a conventional example.

FIG. 4 is a sectional view of the conventional example.

FIG. 5 is a schematic view of generation of leakage magnetic flux of a sample having only a center magnetic film.

FIG. 6 is a schematic diagram of generation of leakage magnetic flux of a sample with a lower magnetic film.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Insulating layer, 3 ... Central magnetic film, 4 ... Primary conductor, 5 ... Secondary conductor, 6 ... Lower magnetic film.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Akio Tago 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Keiichi Yanagisawa 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo No. Nippon Telegraph and Telephone Corporation (56) References JP-A-2-166707 (JP, A) JP-A-58-130511 (JP, A) JP-A-59-36210 (JP, U) (58) Field (Int.Cl. ⁷ , DB name) H01F 30/00-38/42

Claims (2)

(57) [Claims] 1. A thin-film transformer comprising one or a plurality of magnetic film layers, a primary wire and a secondary wire, wherein the primary wire and the secondary wire are constituted by a band-shaped conductor, and the band-shaped conductor is provided in a conductor longitudinal direction. Put the slit of the above
A high-frequency thin-film transformer characterized in that a part or the whole of a strip conductor is subdivided into strips . 2. A thin-film inductor comprising one or a plurality of magnetic film layers and a conductive wire, wherein the conductive wire is formed of a band-shaped conductor, and a slit is formed in the band-shaped conductor in a conductor longitudinal direction.
A high-frequency thin film inductor characterized in that a part or the whole of a strip conductor is subdivided into strips .