JPH0355962B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a rotary transformer with low transmission loss and high voltage amplification ratio, which is excellent in mass production.

[Conventional technology and problems]

In recent years, with the spread of VTRs, there has been a demand for higher recording densities in VTRs and lower noise in signal transmission systems. Generally, a VTR is equipped with a rotating cylinder head that has two or more heads, and the heads are rotated at high speed. The signal from this high-speed rotating head is transmitted to the same number of coils 1 as the head (two sets because there are two heads in Fig. 4), which are wound concentrically with the rotating shaft as shown in Fig. 4. It is connected to the main body circuit via a rotary transformer consisting of a ferrite core 2 which is divided into two parts perpendicular to the rotation axis, facing each other with a constant gap, and surrounding the above-mentioned coil. In such a rotary transformer, the flatter the surfaces of the opposing ferrite cores, the smaller the gap, and the smaller the signal transmission loss. It is also said that the higher the space factor of the coil, the less magnetic flux leaks between the conductors of the coil, and as a result, the transmission loss becomes smaller.

Conventional rotary transformer coils are
It is made by winding formal wire, etc. with a winding machine, but since the wire is wound with a circular cross section, it is difficult to wind the surface facing the gap evenly, and it is also difficult to increase the space factor. It was hot. Furthermore, since it is difficult to wind a large number of turns in a narrow groove of ferrite, it is also impossible to obtain a large winding ratio. Furthermore, for this purpose, the grooves of the ferrite core must be machined deeply, and the surface machining accuracy of the facing surfaces of the ferrite core is strictly required.

In addition, printed coils obtained by etching do not have a sufficient number of turns, but conversely, increasing the number of turns increases DC resistance, making it impossible to outperform wire-wound coils.
Furthermore, the resistance value is as low as that of a wire-wound coil, and the thickness of the etched coil is the same as that of a wire-wound coil, so the surface processing accuracy of the facing surface of the core is maintained at the same level as when using a wire-wound coil. I needed to.

The present invention solves the above problems by providing low transmission loss and
This is a method for manufacturing a high voltage amplification ratio rotary transformer.

[Means for solving problems]

That is, the present invention forms a resist pattern on a thin aluminum plate at a location other than the circuit section, forms a conductor by plating at the circuit section on the substrate, and then forms an insulating layer on the conductor. The printed coil is formed by forming an insulating layer on the conductor, etching away the aluminum thin plate, and forming a conductor by plating on the surface of the obtained conductor that was in contact with the aluminum thin plate. and embedding the printed coil in a plate-shaped circular ferrite core having a plurality of concentric grooves and a plurality of holes in the thickness direction inside or near the grooves. This is a method for manufacturing a multi-head rotary transformer, which includes the step of embedding an extraction circuit section in a hole in the thickness direction of the circular core.

In the present invention, the printed coil is manufactured by forming a resist pattern on a thin aluminum plate at a location other than the circuit area, forming a conductor by plating, forming an insulating layer, removing the thin aluminum plate by etching, and then It is possible to reduce the direct current resistance of the circuit section where the circuit section is plated.

The material for the conductor to be plated is preferably one with good conductivity, such as copper. The aluminum sheet is removed by etching. Therefore, the conductor to be plated should preferably have etching characteristics that are significantly different from those of aluminum, such as copper. On the other hand, the etching solution should be one that dissolves aluminum well but does not dissolve the plated conductor. In order to increase the number of turns to increase the voltage amplification ratio, or to reduce the direct current even with the same number of turns, coils 9 are formed on both sides of the insulation resistance value layer 8 and through-hole connections are made as shown in Figure 2. It is also possible to connect the coils in series or in parallel, and by using this method, the terminals of the coils can be gathered in one place. It is also possible to form coils on both sides of the insulating layer to simultaneously form the coils of a multi-head rotary transformer for all heads.

The plate-shaped circular ferrite core used in the present invention may be manufactured by any conventional method, and the material may be those used in general transformers and conventional rotary transformers. Also, the shape is the first
As shown in the figure, it has a plurality of concentric grooves 3 centered on the rotation axis, and the grooves may be formed to match the cross-sectional shape of the printed coil, but the surface should be flat after the coil is buried. is preferred. Further, grooves 4 may be provided between the coils to function as isolation. Further, a plurality of holes 8 in the thickness direction for filling the extraction circuit 5' are provided in the vicinity of or within the same circular groove for extraction. For the coils corresponding to each head, a take-out circuit section 5' is provided at a position corresponding to the take-out hole 8 on the ferrite core for the take-out printed circuit section, and the coils corresponding to the heads are simultaneously molded on one sheet. FIG. 2 shows an enlarged view of the extraction circuit section 5' and the through-hole section 7.

The unnecessary parts of the formed printed coil are cut off,
After the extraction circuit section 5' is passed through the hole 8 of the ferrite core, each coil is attached to the corresponding concentric groove 3 using an embedded adhesive. Any adhesive may be used, but commonly used room temperature curing type or heat curing type epoxy adhesive can be used.

The coil corresponding to each head can be made by connecting the take-out circuit part tangentially from the position corresponding to the take-out circuit part hole 8, but in terms of productivity, it is better to make the coil at the same time as forming the insulating layer. Preferably, a take-out circuit section 5' is formed thereon.

〔Example〕

Examples will be shown below, but the present invention is not limited to these examples.

Example A negative photoresist "Microresist 747" (Eastman Kodak Co., Ltd.) manufactured by Eastman Kodak Co., Ltd. was coated on an aluminum foil with a film thickness of 80 μm so that the film thickness after drying became 3 μm, and prebaked.
Exposure with a high-pressure mercury lamp through a mask having four concentric coil patterns with different radii, develop with a special developer and rinse solution, dry, and post-bake, except for the patterned areas on the aluminum foil. A resist was formed on the part.

Next, a 100 μm thick copper plating layer was formed on the patterned portion by electrolytic plating using a copper pyrophosphate plating solution manufactured by Harshyou Murata Co., Ltd. and using the aluminum foil as a cathode. The aluminum foil was attached to a polyimide film "Kapton" (DuPont) with a film thickness of 25 μm from both sides, with the surface on which the copper pattern was formed facing the "Kapton" side. Next, the aluminum foil was removed by etching with a solution of 36% by weight hydrochloric acid diluted 2:3 with water, and the through holes were drilled.
A hole of 0.45mmφ was drilled.

Using the aforementioned copper pyrophosphate plating solution and using the coil pattern as a cathode, electrolytic copper plating was performed on the pattern portion to a thickness of 100 μm. As a result, we created four different sizes of coils for 4 heads with a conductor line width of 140 μm, a conductor spacing of 10 μm, a film thickness of 200 μm, and a number of turns of 20, and a coil for 4 heads with a conductor line width of 1500 μm, a film thickness of 200 μm, and a number of turns of 1 turn. Coils of four different sizes were simultaneously formed on the sheet with each having the same center. Next, unnecessary parts of the insulating sheet were removed, and the extraction circuit part (the part that passes through the hole in the ferrite core and exits on the other side) was cut out. The take-out circuit part was passed through the take-out circuit hole of the ferrite core, and the above coil was adhered to the concentric groove of the ferrite core using "Cemendine High Super" manufactured by Cemendine. The obtained rotary transformer has a flat surface on which the coil is embedded and a high coil space factor, so the coupling coefficient is 0.97.
Low transmission loss was achieved. In addition, the turns ratio was 20:1, the voltage amplification factor was large, and even a 20-turn coil had a DC resistance of 2.4Ω, so a low-noise rotary transformer was obtained. Moreover, since the coil portion of the rotary transformer for four heads is formed in principle by the same process as the coil for one head, productivity is excellent.

〔Effect of the invention〕

According to the method of the present invention, the number of turns can be increased and the resistance can be reduced, so the coil part has high precision, high density, and a high space factor, and the etching method allows for lower transmission loss and higher voltage amplification than when using printed coils. A ratio rotary transformer is obtained.

Furthermore, since the coil can be made thinner, it is possible to use a ferrite core with a shallow meso and rough surface machining accuracy on the opposing surfaces.

[Brief explanation of drawings]

FIG. 1 shows a cross-sectional view and an arrow view of the rotary transformer of the present invention, and FIG. 2 shows an enlarged view of the extraction circuit section (FIG. 1 c) of the rotary transformer of the present invention.
FIG. 3 shows a cross-sectional view of the printed coil section, and FIG. 4 shows a conventional rotary transformer. 1...Wound coil, 1'...Printed coil (primary side), 1''...Printed coil (secondary side), 2
...Ferrite core, 3... Concentric groove (for coil), 4... Concentric groove (for isolation), 5... Outgoing wire, 5'... Outgoing circuit section, 6... Outgoing circuit Groove for section, 7... Through hole, 8... Hole for take-out circuit section, 9...
Insulating layer, 10... conductor.

Claims (1)

[Claims] 1. Form a resist pattern on a thin aluminum plate at a location other than the circuit area, form a conductor on the circuit area on the board by plating, then form an insulating layer on the conductor, and then remove the aluminum thin plate by etching. Further, the resist pattern is used only on the surface of the obtained conductor that was in contact with the aluminum thin plate, and a conductor is formed by plating to obtain a printed coil, and the printed coil is formed with a plurality of concentric grooves. burying it in a concentric groove of a plate-like circular ferrite core having a plurality of holes in the thickness direction inside or near the groove, and burying the take-out circuit section in the holes in the thickness direction of the circular core. Manufacturing method for multi-hed rotary transformer.