JPH06215962A - Transformer - Google Patents

Abstract

PURPOSE:To provide a small, thin and easy-to-manufacture transformer being mounted on a printed wiring board along with other electronic components. CONSTITUTION:A multilayer printed board 1 is constituted of a plurality of layers of basic material 4, formed with a spiral coil conductor pattern 5, laminated on one or both sides through insulation layers 6. The coil conductor patterns 5 formed on the of one layer Of basic material 4 are connected through an inter-grid via hole 7 and coil conductor patterns 5 of a plurality of layers are connected through a through hole 8 thus constituting a primary winding coil. Secondary winding coil is constituted in similar manner. A through hole is made in the center of the multilayer printed board 1 and one of magnetic cores 2, 2' passes through the through hole to form a closed magnetic path. An external connecting terminal 3 is connected with a desired coil conductor pattern in the multilayer printed board 1 through the through hole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer, and more particularly to a thin and compact transformer suitable for mounting on a printed wiring board together with other electronic components for use.

[0002]

2. Description of the Related Art A transformer used in combination with an electronic circuit, for example, a DC-DC converter transformer for converting a DC voltage, is mounted on a printed wiring board side by side with other electronic components such as an IC and a capacitor. However, it is desirable that the size of the transformer be small and that its height be as low as that of other electronic components.

The transformer has a plurality of coils, and a DC-DC converter transformer used with electronic parts also has at least two coils. In addition, these coils generally differ in the number of turns and the wire thickness.

Conventionally, in this type of DC-DC converter transformer or the like, each coil is formed by winding an enamel copper wire or the like around a plastic winding frame. Furthermore, several to about 10 external connection terminals are attached to the terminal mounting portion that is formed integrally with the winding frame or separately, and both ends of each coil are connected to these external connection terminals, and the external connection terminals are printed wiring board. By soldering to the upper connection land, the coil and the external circuit are connected and the transformer itself is fixed to the printed wiring board. Therefore, the winding made of the enamel copper wire and the like, the winding frame thereof, and the external connection terminal mounting portion make it difficult to downsize the entire transformer, and there is a limit to downsizing and thinning.

On the other hand, as a conventional technique for reducing the size and thickness of this type of DC-DC converter transformer, a sheet coil and an insulating sheet are laminated as described in, for example, Japanese Patent Application Laid-Open No. 61-74311. It is known that each sheet coil is connected with a connecting conductor to use the laminated sheet wiring body as a coil.

[0006]

In the above-mentioned prior art, since the coil composed of the laminated sheet wiring body is used, the winding frame is unnecessary, and the connecting conductor for connecting the sheet coils also serves as an external connecting terminal. As a result, the external connection terminal mounting part is not required, and the transformer can be made compact and thin. However, since the sheet-like coil and the insulating sheet are laminated in multiple layers, it is necessary to align each laminated body with high accuracy, and there is a problem in that connection work with external connection terminals becomes complicated. In particular, the smaller the number of windings of the transformer and the smaller the size of the transformer, the more hindered is the automation of manufacturing and the improvement of reliability such as securing a necessary insulation distance.

It is an object of the present invention to realize a compact and thin transformer which is mounted on a printed wiring board together with other electronic components for use, and facilitates manufacturing.

[0008]

In the transformer of the present invention, a plurality of base materials on which a spiral conductor pattern is formed are laminated with an insulating layer interposed therebetween to form coils for primary and secondary windings, and the center thereof is formed. A multilayer printed circuit board having a through hole formed therein, an external connection terminal connected to the arbitrary spiral conductor pattern in the multilayer printed circuit board by a through hole, and surrounding the multilayer printed circuit board and being inserted into the through hole. It is basically composed of a magnetic core forming a closed magnetic circuit.

Specifically, for example, N-turn spiral conductor patterns are formed on the front and back of one substrate, and both conductor patterns are connected by via holes provided in the substrate to form a 2N-turn coil. To do. Furthermore, the 2N
A coil of 2N × n turns is formed by stacking n base materials of a coil of turn and connecting each coil by a through hole. Alternatively, n pieces of the 2N-turn coil base material are superposed, terminals are brought out from the respective coils by through holes, and the terminals are connected to form a 2N × n-turn coil.

In the transformer of the present invention, the base material of the spiral conductor pattern forming the coil of the primary (or secondary) winding is the spiral shape forming the coil of the secondary (or primary) winding. It is characterized in that they are arranged so as to sandwich the base material of the conductor pattern.

[0011]

In the transformer of the present invention, as the coils of the primary and secondary windings, a plurality of coil conductor patterns are laminated inside via an insulating layer, and the coil conductor patterns of each layer are connected by via holes or through holes. Use a multilayer printed circuit board. The manufacture of such a multilayer printed circuit board is
This is exactly the same as the case of the multilayer printed circuit board for I, the automation of the production can be easily realized, and the variation in the production is small. In addition, the coil formed of the multilayer printed circuit board does not require a winding frame, and the external connection terminal connected to the coil conductor pattern by the through hole provided in the multilayer printed circuit board also serves as the external connection terminal of the transformer, so that the terminal mounting portion is also provided. It is not necessary and the transformer can be made smaller and thinner.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1A is a perspective view of an embodiment of the transformer according to the present invention. In the figure, 1 is a multilayer printed circuit board, 2'is a pair of upper and lower magnetic cores, and 3 is an external connection terminal. Although not shown in the drawing, a through hole for the magnetic core is provided at the center of the multilayer printed board 1. The magnetic cores 2 and 2'are integrated so as to sandwich the multilayer printed circuit board 1, and a central core provided on one side passes through a through hole in the central portion of the circuit board 1 to form a closed magnetic circuit.

FIG. 1 (B) is an enlarged view showing a partial cross section of the multilayer printed circuit board 1. The multilayer printed circuit board 1
A plurality of base materials 4 each having a spiral coil conductor pattern 5 formed on one surface or both surfaces are laminated with an insulating layer 6 interposed therebetween. Then, inter-grating via holes (IVH: Interstitial Via) are provided between the coil conductor patterns 5 belonging to one winding formed dispersedly on both surfaces of the base material 4.
Similarly, the coil conductor patterns 5 belonging to one winding formed by being dispersed on the base material 4 in a separated layer are connected by through through holes 8. Further, the external connection terminal 3 shown in FIG. 1A is also connected to a desired coil conductor pattern 5 by a desired through hole provided in the multilayer printed board 1.

FIG. 2 shows an exploded view of the multilayer printed circuit board 1. In the figure, 4a, 4b and 4c are base materials, 5b,
5d and 5f are coil conductor patterns formed on the upper surfaces of the respective substrates 4a, 4b, and 4c. Although not shown in the figure, coil conductor patterns are also formed on the lower surfaces of the respective base materials 4a, 4b, 4c, and 5a, 5c, 5e show these coil conductor patterns. 6a, 6b, 6c, 6
d is a fixing agent. 7a, 7b and 7c are interstitial via holes (IVH), 8a and 8b are through through holes, 9a,
9b and 9c are through holes for the magnetic core.

Substrates 4a, 4b, 4c, adhesives 6a, 6
By alternately stacking b, 6c, and 6d as shown in FIG. 2, and applying pressure, heating, and drying, the adhesives 6a to 6d become the insulating layer 6 as shown in FIG. Board 1
Are integrally molded. Here, the insulating layer 6 between the coil conductor patterns 5 of the adjacent layers in FIG.
With the above or three or more layers, for example, the IEC standard,
Reinforced insulation of safety standards such as UC standards is achieved. In addition,
The multilayer printed circuit board 1 may be molded by applying a fixing material to the base material on which the coil conductor pattern is formed, stacking the board coated with the fixing material, and heating and drying. In any case, the manufacture of the multilayer printed board 1 is basically the same as the manufacture of the multilayer printed board for LSI.

FIG. 3 shows an example of connection of coil conductor patterns. This is six coil conductor patterns 5a-
5f are laminated, of which the coil conductor pattern 5a,
5b, 5e, and 5f are connected in series by interstitial via holes 7a, through through holes 8a, and interstitial via holes 7c to form one winding (primary winding) 11, and the coil conductor patterns 5c and 5d are interstitial. This is an example in which the other winding (secondary winding) 12 is connected in series by a via hole 7b. In the case of FIG. 3, coil conductor patterns 5a, 5b, 5
The total number of turns of e and 5f is 12, the coil conductor pattern 5
The total number of turns of c and 5d is 2, and the turn ratio between the primary winding 11 and the secondary winding 12 is 12; 2, that is, 6: 1. 1
Since the secondary winding 11 is vertically distributed and the secondary winding 12 is sandwiched between them, the leakage inductance of the entire winding can be reduced. By reversing the arrangement of the primary winding and the secondary winding 12, the leakage inductance of the entire winding can be similarly reduced.

FIG. 3 shows an example of connection of transformer windings of two circuits, but a multi-winding transformer of three or more circuits can be easily constructed by increasing the number of laminated coil conductor patterns and changing the connections. It is also possible to easily arrange the respective coil conductor patterns in a self-distributed manner to reduce the overall leakage inductance. Further, the terminals of the coils of the respective layers may be drawn to the outside through the through holes, and the coils of arbitrary layers may be connected in series outside.

[0019]

As is apparent from the above description, claim 1
According to the transformers of the inventions Nos. 4 to 4, not only the size and thickness can be reduced, but also the manufacturing is easy, the manufacturing variations are small, and the characteristics are stable. According to the transformer of the invention of claim 5, the leakage inductance of the winding can be reduced.

[Brief description of drawings]

FIG. 1 is a perspective view and a partially enlarged sectional view of an embodiment of a transformer according to the present invention.

FIG. 2 is an exploded view of an example of a multilayer printed circuit board used in the transformer of the present invention.

FIG. 3 is a coil array diagram of an embodiment of the transformer of the present invention.

[Explanation of symbols]

 1 Multilayer Printed Circuit Board 2, 2'Magnetic Core 3 External Connection Terminal 4 Base Material 5 Coil Conductor Pattern 6 Insulating Layer 7 Interstitial Via Hole 8 Through Through Hole

Front page continuation (72) Inventor Hotaro Kaisawa 810 Shimoimaizumi, Ebina, Kanagawa Kanagawa, Ltd. Office Systems Division, Hitachi Ltd. System Division

Claims (5)

[Claims] 1. A multi-layered printed circuit board, wherein a plurality of base materials each having a spiral conductor pattern formed thereon are laminated via an insulating layer to form coils for primary and secondary windings, and a through hole is provided at the center thereof. An external connection terminal that is connected to an arbitrary spiral conductor pattern in the multilayer printed circuit board by a through hole; and a magnetic core that surrounds the multilayer printed circuit board and is inserted into the through hole to form a closed magnetic circuit. A transformer that is characterized by 2. A N-turn spiral conductor pattern is formed on each of the front and back sides of one base material, and both conductor patterns are connected by via holes provided in the substrate to form a 2 N-turn coil. The transformer according to claim 1, wherein 3. A substrate of n coils of 2N turns is superposed on each other, and each coil is connected by a through hole to form 2N × n.
The transformer according to claim 2, wherein a coil of turns is formed. 4. A substrate of 2N-turn coils is superposed on n sheets, terminals are provided to the outside by through holes from the respective coils, and the terminals are connected to form a 2N × n-turn coil. The transformer according to claim 2, wherein 5. A spirally conductive pattern base material forming a coil of a primary (or secondary) winding is a spirally conductive pattern base material forming a coil of a secondary (or primary) winding. The transformer according to claim 1, wherein the transformer is arranged so as to sandwich it.