JPH11186046A - Transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transformer which can be manufactured with few number of steps. SOLUTION: This transformer includes a multilayered printed circuit board 2, having transformer winding 1 in the form of circuit patterns and also includes a ferromagnetic material forming a core for the windings 1. An electrical shielding layer 5 in the form of a circuit pattern is provided to the board 2 at least at one of the outer winding layers 1 and therebetween. The winding 1 and electrical shielding layer 5 can be formed by a print wiring method, at manufacturing of the board 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer in which a winding for a transformer is formed on a multilayer printed wiring board.

[0002]

2. Description of the Related Art In a conventional transformer, a wire is generally formed by winding an electric wire or a copper foil ribbon around a bobbin. When an electric shield layer is formed between the windings in order to reduce the common mode noise transmitted between the windings provided in a plurality of layers, after forming the winding on the bobbin, an insulating sheet and an electric shield are formed thereon. It is performed by winding a conductor sheet and an insulating sheet forming a layer in this order, and further winding a winding thereon.

[0003]

As described above, the conventional transformer has a problem that the number of manufacturing steps is increased in forming the electric shield layer. Further, in order to ensure insulation between windings, it is necessary to increase a creepage distance or a space distance, and there is a problem that the overall shape of the transformer becomes large.

[0004] The present invention has been made in view of the above points, and has as its object to provide a transformer that can be manufactured with a reduced number of steps, and to provide a transformer that can be reduced in size. It is intended for.

[0005]

A transformer according to the present invention comprises a multilayer printed wiring board 2 having a transformer winding 1 formed in a circuit pattern, and a ferromagnetic material forming a magnetic core 3 in the transformer winding 1. The electric shield layer 5 is provided in a circuit pattern on the multilayer printed wiring board 2 between at least one of the plurality of transformer windings 1 and outside the transformer winding 1. Things.

[0006] The invention of claim 2 provides the electric shield layer 5.
Are provided so as not to form an electrically closed circuit around the magnetic core 3. Claim 3
The invention is characterized in that the transformer winding 1 has an end face embedded in the multilayer printed wiring board 2. The invention according to claim 4 is characterized in that terminals 6 for connecting the electric shield layer 5 to the ground are provided on the multilayer printed wiring board 2.

[0007]

Embodiments of the present invention will be described below. The multilayer printed wiring board 2 is formed in a frame shape as shown in FIG. 3, and by providing an annular circuit pattern formed by printed wiring processing of a copper foil-bonded resin laminate as an inner layer circuit, A transformer winding 1 is formed in a pattern. The transformer windings 1 are formed in a plurality of layers so as not to be electrically connected to each other via an insulating layer. In the illustrated embodiment, the transformer windings 1 on the primary side and the secondary side are formed. is there. The transformer winding 1 is formed so as to be embedded in the multilayer printed wiring board 2, and the end face of the transformer winding 1 is covered with resin so as not to be exposed on the outer surface of the multilayer printed wiring board 2. It is.

[0008] Terminal portions 9 are integrally provided at two opposing locations on the outer periphery of the multilayer printed wiring board 2, and each terminal portion 9 has a plurality of through-holes 10 whose inner periphery is plated with through-holes. Is formed. The primary-side transformer winding 1 is connected to the through-hole 10 of one terminal 9.
The secondary winding 1 is connected to a through-hole 10 of the other terminal 9. Terminals 6 formed by pins are inserted into the through holes 10.
The multilayer printed wiring board 2 is not limited to the above-described round frame shape, but may be formed in a square frame shape.

[0009] Similarly, the multilayer printed wiring board 2
By providing an annular circuit pattern formed by printing wiring processing of a copper foil-bonded resin laminate as an inner layer circuit or an outer layer circuit, the electric shield layer 5 is formed with this circuit pattern. The electric shield layer 5 is provided between the plurality of transformer windings 1 so as not to be electrically connected via an insulating layer, and is provided on the surface of the multilayer printed wiring board 2 outside the transformer winding 1. Is provided via The electric shield layer 5 outside the transformer winding 1 is not necessarily provided. The electric shield layer 5 between the transformer windings 1 is formed so as to be embedded in the multilayer printed wiring board 2.
The end surface of the electric shield layer 5 is covered with resin so as not to be exposed on the outer surface of the multilayer printed wiring board 2. The electric shield layer 5 is formed in an annular shape.
As shown in (1), a separating portion 11 is provided at one place to prevent a closed circuit, and the electric shield layer 5 is connected to a through hole 10 of one terminal portion 9. By inserting the terminal 6 formed of a pin into the through hole 10, the electric shield layer 5 can be connected to the ground.

On the other hand, the housing 15 is formed of a ferromagnetic material such as iron or ferrite, and includes a pair of housing halves 15a and 15b. Each of the housing halves 15a and 15b is formed in a thin disk shape, and a circular hole 16 is formed in the center. Walls 17 and 18 are provided on the inner and outer circumferences of the lower surface of the upper housing half 15a, and walls 17 and 18 are provided on the inner and outer circumferences of the upper surface of the lower housing half 15b.
18 are provided integrally with each other, and an annular concave portion 19 is formed between the walls 17 and 18 in each of the housing halves 15a and 15b. Each housing half 1
Notches 20 are formed at two opposing locations on the outer peripheral wall 18 of 5a and 15b. This pair of housing halves 15
Although a and 15b are formed to have substantially the same dimensions and the same shape, they are not limited to the circular shape as described above, and may be polygonal.

Then, as shown in FIG. 2, the multilayer printed wiring board 2 is fitted into the concave portion 19 with the terminal portions 9 protruding from the cutouts 20, and the multilayer printed wiring board 2 is sandwiched between the housing halves 15a and 15b. Thus, the printed wiring board 2 can be incorporated in the housing 15 as shown in FIG. In this case, an inner peripheral wall 17 of a housing 15 serves as a magnetic core 3, a transformer winding 1 of a multilayer printed wiring board 2 and a ferromagnetic housing 1.
5 constitutes a transformer.

In the transformer thus formed,
The electric shield layer 5 provided to reduce the transformer windings 1 and the common mode noise transmitted between the transformer windings 1 can be formed by printed wiring processing when manufacturing the multilayer printed wiring board 2. It can be manufactured with a small number of manufacturing steps. Further, although the electric shield layer 5 is formed around the magnetic core 3, the separation section 11 is provided so that an electric closed circuit is not formed around the magnetic core 3. Thus, the copper loss can be reduced. Further, since the transformer windings 1 and the electric shield layer 5 between the transformer windings 1 are embedded in the multilayer printed wiring board 2 and the end faces are not exposed from the multilayer printed wiring board 2, the end faces are not exposed. Higher resistance to tracking and air discharge can be obtained, reliability can be improved, and there is no need to increase the creepage distance or clearance to ensure insulation between the end faces. This makes it possible to reduce the size.

[0013]

As described above, the present invention provides a multi-layer printed wiring board having a transformer winding formed by a circuit pattern and a ferromagnetic material forming a magnetic core in the transformer winding. Since the electric shield layer is provided on the multilayer printed wiring board in a circuit pattern at least between the transformer windings of the layers and at least one of the outer sides of the transformer winding, the transformer winding and the electric shield layer are formed of the multilayer printed wiring. The transformer can be formed by printed wiring processing at the time of manufacturing the board, and the transformer can be manufactured with a small number of manufacturing steps.

According to the second aspect of the present invention, since the electric shield layer is provided so as not to form an electric closed circuit around the magnetic core, the current flowing through the electric shield layer can be suppressed, and copper loss can be reduced. It is possible to achieve reduction. According to the third aspect of the present invention, since the transformer winding has the end face embedded in the multilayer printed wiring board, it is possible to obtain a high resistance to tracking between the end faces and air discharge. This eliminates the necessity of increasing the creepage distance or the space distance, and makes it possible to reduce the size of the transformer.

According to the fourth aspect of the present invention, the terminal for connecting the electric shield layer to the ground is provided on the multilayer printed wiring board. Therefore, the effect of reducing the common mode noise by the ground of the electric shield layer is further enhanced. What you can get.

[Brief description of the drawings]

FIG. 1 shows an example of an embodiment of the present invention,
(A) is a front sectional view, and (b) is a side sectional view.

FIG. 2 is a plan view of the example of the embodiment with the housing opened.

FIGS. 3A and 3B show a multilayer printed wiring board according to an example of the above embodiment, wherein FIG. 3A is a plan view and FIG. 3B is a cross-sectional view taken along the line II.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transformer winding 2 Multilayer printed wiring board 3 Magnetic core 5 Electric shield layer 6 Terminal

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H01F 31/00 R (72) Inventor Toshiyuki Yamaguchi 1048 Odakadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works, Ltd. (72) Inventor Nishioka Shigeki 1048, Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Works, Ltd. (72) Inventor Yuichi Fujisawa 1048 Kadoma, Kazuma, Kadoma-shi, Osaka Matsushita Electric Works, Ltd.

Claims (4)

[Claims] 1. A multi-layer printed wiring board having a transformer winding formed in a circuit pattern and a ferromagnetic material forming a magnetic core in the transformer winding. And a multi-layer printed wiring board provided with an electric shield layer in a circuit pattern on at least one of the outer sides of the transformer winding. 2. The transformer according to claim 1, wherein the electric shield layer is provided so as not to form an electric closed circuit around the magnetic core. 3. The transformer according to claim 1, wherein an end face of the transformer winding is embedded in the multilayer printed wiring board. 4. The transformer according to claim 1, wherein a terminal for connecting the electric shield layer to the ground is provided on the multilayer printed wiring board.