JPS62271406A - Manufacture of rotary transformer for multihead - Google Patents

Abstract

PURPOSE:To obtain a rotary transformer having a low transmission loss and a high voltage amplyfication ratio, by burying a printed coil in a concentric circular groove of a planar circular ferrite core, burying a taking-out circuit part in a hole arranged in the direction of core thickness. CONSTITUTION:On a metal thin plate, a resist pattern is formed on a part other than the part corresponding to a circuit part, and a conductor is formed by plating on the circuit part of the thin plate. Then an insulating layer is formed on the conductor, and the thin plate is eliminated to obtain printed coils 1' and 1''. A plurality of concentric circular grooves 3 are arranged on a planar circular ferrite core 2, and a plurality of holes in the direction of core thickness are arranged in the inner part or in the vicinity of the grooves 3. The coils 1' and 1'' are buried in the grooves 3, and a taking-out circuit part 5' is buried in the hole in the direction of core thickness. Thereby a rotary transformer having a low transmission loss and a high voltage amplification ratio can be obtained.

Description

[Detailed Description of the Invention] 3. 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 that can be easily mass-produced.

[Conventional technology and problems]

In recent years, with the spread of VTRs, there has been a demand for higher recording densities in VTRs, and there has also been a demand for lower noise in signal transmission systems.

Generally, a VTR is equipped with a rotating cylinder head that has two or more heads, and is used by rotating the heads 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 rotating shaft, facing each other with a certain gap therebetween, 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.

Conventionally, the coils of these rotary transformers are 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 flat. However, it was difficult to increase the space factor. 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 in the ferrite core must be machined deeply, and the surface machining accuracy of the opposing surfaces of the ferrite core is strictly required.

In addition, printed coils obtained by etching do not have a sufficient number of coil turns, but conversely, increasing the number of turns increases DC resistance, making it impossible to outperform wire-wound coils. Furthermore, since the etched coil has the same resistance value and the same number of turns as a wire-wound coil, the surface processing accuracy of the opposing surface of the core must be maintained at the same level as when using a wire-wound coil. was there.

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

[Failure to solve the problem]

That is, in the present invention, a resist pattern is formed on a thin metal plate at a location other than the circuit section, a conductor is formed by plating at the circuit section on the substrate, an insulating layer is formed on the conductor, and then an insulating layer is formed on the conductor. removing the thin metal plate to obtain a printed coil, and converting the printed coil into a plate-like circular ferrite core having a plurality of concentric grooves and a plurality of holes in the thickness direction inside or near the grooves. This method of manufacturing a multi-head rotary transformer includes the steps of embedding the printed coil in a concentric groove and embedding the 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 metal plate at a location other than the circuit area, forming a conductor by plating, pasting it on an insulating layer, and removing the thin metal plate. Preferably, after the above-described treatment, the DC resistance of the circuit portion can be reduced by plating the circuit portion again.

The material of the conductor to be plated is preferably copper, which has good conductivity. 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 installed on both sides of the insulation resistance layer 8 as shown in FIG.
It is also possible to connect the coils in series or in parallel by forming through-hole connections, 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-like 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. In addition, the shape has a plurality of concentric grooves 3 centered on the rotation axis as shown in Fig. 1, and the grooves may be formed to match the cross-sectional shape of the printed coil.
It is preferable that the surface be flat after the coil is buried. Further, grooves 4 may be provided between the coils to function as isolation. Further, a plurality of holes 68 in the thickness direction are provided for filling the extraction circuit 5' and are provided in the vicinity of or within the same circular groove. For the coils corresponding to each head, a take-out circuit part 5' is provided at a position corresponding to the take-out hole 8 on the ferrite core for the take-out printed circuit part, and all the coils corresponding to the heads are simultaneously molded on one sheet. Figure 2 shows the take-out circuit section 5'.
and shows an enlarged view of the through-hole portion 7.

Unnecessary parts of the formed printed coils are cut off, the lead-out circuit section 5' is passed through the hole 8 of the ferrite core, and each coil is embedded into the corresponding concentric groove 3 and pasted with an adhesive. Any adhesive may be used, but commonly used room temperature curing type or heat curing type eboshi adhesive can be used.

For the coils corresponding to each head, it is only necessary to connect the take-out circuit section tangentially from the position corresponding to the take-out circuit hole 8, but from the viewpoint of productivity, it is recommended that the coil be formed at the same time as 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 74" manufactured by Eastman Co., Ltd. was coated on an aluminum foil with a film thickness of 80 μm.
After drying 7J (@Eastman Kodak), the film thickness is 3μ.
It was coated and prebaked to give a coating thickness of m. It is exposed to light using a high-pressure mercury lamp through a mask having four concentric coil patterns with different radii, developed using a special developer and rinsing solution, dried, and post-baked. A resist was formed on the parts.

Next, using a copper pyrophosphate plating solution manufactured by Barshaw Uchide Co., Ltd., a 100 μm plating solution was applied to the patterned area using aluminum foil as a cathode.
An m-thick copper metal middle layer was formed by electrolytic plating. Film thickness 25
μl DuPont polyimide film “Kapton” (
(DuPont), the aluminum foil was attached to the Kapton film from both sides, with the side on which the copper pattern was formed facing the "Kapton" side. Next, the aluminum foil was removed by etching with a solution prepared by diluting 36% by weight hydrochloric acid with water at a ratio of 2:3, and the through holes were drilled with a 0.4%
A hole of 5mφ was drilled.

Using the copper birophosphate plating solution described above, the pattern portion was electrolytically plated with copper to a thickness of 100 μm using the coil pattern as a cathode. As a result, we produced 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 turns.
Four different sized coils for the head were formed simultaneously on the sheet in a cocentric arrangement. 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 lead-out circuit part was passed through the hole for the lead-out circuit in the ferrite core, and the coil was adhered to the concentric grooves 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.
With a coupling coefficient of 0.97, low transmission loss was achieved. In addition, the turns ratio can be set to 20=1, the voltage amplification factor is large, and
Even with a 0-turn coil, the DC resistance was 2.4Ω, so a low-noise rotary transformer was obtained.

Moreover, the coil part of the rotary transformer for 4 heads is 1
Productivity is excellent because it is formed using the same process as the head coil in principle.

〔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 high space factor.
The etching method provides a rotary transformer with lower transmission loss and higher voltage amplification ratio than when using printed coils.

Furthermore, since the coil can be made thinner, it is possible to use a ferrite core with shallow grooves and rough surface machining accuracy on 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, Fig. 2 shows an enlarged view of the extraction circuit section (Fig. 1 C) of the rotary transformer of the invention, and Fig. 3 shows a printed coil section. FIG. 4 shows a cross-sectional view of a conventional rotary transformer. 1 - Winding coil 1' - Printed coil (primary side) 1" - Printed coil (secondary side) 2 - Ferrite core 3 - Concentric groove (for coil) 4 - Concentric groove (isolated) (for ration) 5・-
Take-out electric wire 5' - - Take-out circuit part 6 - Take-out circuit part groove 7 - - Through hole 8 - Take-out circuit part hole 9 - Insulating layer 1〇 - Conductor patent applicant Asahi Kasei Kogyo Co., Ltd. Figure 2, Figure 3 Figure 4 L pa

Claims (1)

[Claims] A resist pattern is formed on a thin metal plate at a location other than the circuit area, a conductor is formed on the circuit area on the board by plating, an insulating layer is formed on the conductor, and the thin metal plate is then removed. The process of obtaining a printed coil, embedding the printed coil in a concentric groove of 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, and taking out the printed coil. A method for manufacturing a multi-head rotary transformer, comprising the step of embedding a circuit section in a hole in the thickness direction of the circular core.