JPH0355961B2 - - 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.

[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 there are heads (two sets since there are two heads in Fig. 3), which are wound concentrically with the rotating shaft as shown in Fig. 3. The coil is connected to the main 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 constant gap, and surrounding the 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 types of 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 have the same space factor as wire-wound coils, so the number of turns in the coil may not be sufficient, or conversely, if the number of turns is increased, the DC resistance will increase. It was not possible to outperform wire-wound coils. Furthermore, with an etched coil that has the same resistance and number of turns as a wire-wound coil, the thickness of the coil is also the same as a wire-wound coil, so the surface processing accuracy of the facing surface of the ferrite core is maintained at the same level as when using a wire-wound coil. It is necessary to.

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

[Means for solving problems]

That is, the present invention forms a resist pattern on a thin aluminum plate at a corresponding location other than the circuit area,
After forming a conductor on the circuit part on the board by plating, an insulating layer is formed on the conductor, and then the thin aluminum plate is removed by etching, and the surface of the obtained conductor that was in contact with the thin aluminum plate is plated. A step of forming a conductor to obtain a printed coil, and embedding the printed coil in a concentric groove of a plate-shaped circular ferrite core provided with a plurality of concentric grooves and a plurality of grooves in the radial direction of the circle. This is a method for manufacturing a rotary transformer, comprising the steps of embedding the extraction circuit section in a groove in the radial 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 corresponding location other than the circuit area, forming a conductor by plating, forming an insulating layer, removing the thin aluminum plate by etching, and then Plating the circuit section to reduce the DC resistance of the circuit section. Note that the conductor to be plated should preferably have good conductivity; for example, copper is preferable. The aluminum sheet is removed by etching. Therefore, it is preferable that the conductor to be plated be made of a material such as copper, which has etching characteristics significantly different from that of aluminum. 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 decrease the DC resistance value even with the same number of turns, coils 9 are formed on both sides of the insulating 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. In addition, if there is no need to increase the number of turns or to reduce the DC resistance, it is possible to place the coil on one side of the insulating layer and collect the circuitry on the other side of the coil section of a multi-head rotary transformer. However, all heads can be manufactured in one piece. The plate-like circular ferrite core used in the present invention may be manufactured by conventional methods, and the material may be as follows:
It may be one used in a general transformer or a conventional rotary transformer. In addition, the shape has a plurality of circular grooves 3 having the same circumference centered around 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 embedding. Further, grooves 4 may be provided between the coils to function as isolation. Furthermore, a plurality of grooves 6 are provided in the radial direction in order to embed the extraction circuit 5'.

The coils corresponding to each head can be connected to the take-out circuit section 5' from the positions corresponding to the take-out circuit grooves 6, but considering productivity,
It is preferable to form the lead-out circuit portion 5' on the insulating layer at the same time as the coil is formed. Each coil can be formed separately and embedded in the ferrite core one after another, but in the case of two heads, the coils are formed on both sides of the insulating layer and the through holes 7 are connected to connect the outer coil and the inner coil. If the extraction patterns are placed on the outside and inside of the coil, both the outside coil and the inside coil can be formed on a single insulating layer at the same time when forming the printed coil, thereby improving productivity.

Any adhesive can be used to bond the coil and ferrite core, but commonly used room temperature curing type or heat curing type epoxy adhesive can be used.

〔Example〕

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

Example A negative photoresist "Microresist 747" 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. The circuit pattern mask of a 2-head rotary transformer coil was exposed to light using a high-pressure mercury lamp, developed using a special developer and rinse solution, dried, and post-paked to form a resist on areas other than the pattern on the aluminum foil. .

Next, a 100 μm thick copper plating layer was formed on the patterned portion by electroplating using a copper pyrophosphate plating solution manufactured by Harshyou Murata Co., Ltd. and using the aluminum foil as a cathode. The above-mentioned aluminum foil was attached to a polyimide film "Kapton" manufactured by 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 prepared by diluting 36% by weight hydrochloric acid with water at a ratio of 2:3, and a hole of 0.45 mmφ was drilled in the through-hole portion.

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. The result was a coil with a conductor line width of 140μm, a conductor spacing of 10μm, a film thickness of 200μm, and a number of turns of 20, a conductor line width of 1500μm,
A coil with a film thickness of 200 μm and one turn was formed. The above coil was adhered to the concentric grooves of the ferrite core for a rotary transformer using "Cemedine High Super" manufactured by Cemedine.

The obtained rotary transformer was flat from the surface where the coil was embedded, and the coil space factor was high, so the coupling coefficient was 0.98 and low transmission loss was achieved. In addition, the turns ratio is 20:1, the voltage amplification factor is large, and even a 20-turn coil has low DC resistance.
Since the resistance was 1.1Ω, a low-noise rotary transformer was obtained.

〔effect〕

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

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 is a sectional view and an arrow view of a rotary transformer according to the present invention. FIG. 2 is a sectional view of the printed coil portion of the rotary transformer shown in FIG. FIG. 3 is a sectional view and an arrow view of 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...Insulating layer, 9...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, form an insulating layer on the conductor, and then remove the thin aluminum 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 the conductor is formed by plating to obtain a printed coil, and the printed coil is formed into a plurality of concentric grooves. manufacturing a rotary transformer, including the steps of: embedding in a concentric groove of a plate-shaped circular ferrite provided with a plurality of grooves in the radial direction of the circle; and burying a take-out circuit section in the groove in the radial direction of the circular core. Law.