JPH11162744A - Square air-core coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a reliable surface mounting on a high packing-density article. SOLUTION: A lead 11 made of varnished wire is wound in the shape of a square tube to form an air coil. Both of the ends of the lead 11 are stripped to eliminate insulating coating and to form connecting parts 12 and 13 on a side of the square tube, namely on the surface to be connected to a wiring board 16. The connecting parts 12 and 13 are shifted toward the outside, namely toward the side of the wiring board for mounting by about the radius of the lead 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rectangular air-core coil in which a conductive wire covered with an insulating layer is wound in a rectangular cylindrical shape, and the insulating layers at both ends are peeled off to form a connection.

[0002]

2. Description of the Related Art A rectangular air-core coil of this type is used for a relatively high-speed signal transmission system of several tens to several hundreds of MHz between IC elements, for example, for impedance matching and filter elements. FIG. 2 shows a conventional rectangular air-core coil, in which a conductive wire 11 coated with an insulating layer is wound in a rectangular cylindrical shape.
At both ends, the insulating layers are peeled off to form connection portions 12 and 13 (13 is hidden in the figure). The connection portions 12 and 13 are provided on the same surface of a rectangular tube. For example, the square air-core coil 14 is provided on a wiring board, the axis thereof is parallel to the plate surface of the wiring board, and the connection portions 12 and 13 are provided. It is surface-mounted as the wiring board side.

The conductive wire 11 is, for example, a so-called enamel wire in which an enamel is baked to form an insulating layer. The diameter of the wire is about 0.8 to 1.2 mm. The length L1 has a square cylindrical shape of about 5 mm. The number of turns is generally about 2 to 10.

[0004]

In the conventional rectangular air-core coil, a connection failure may occur when the coil is actually mounted on a wiring board or the like. Although the number is only about 2%, even if the defective connection is soldered and repaired manually, the interval between the elements on the wiring board is narrow, and a soldering iron cannot be inserted. The entire substrate was wasted, resulting in a large loss.

[0005] As a result of pursuing the cause of such a connection failure, it has been determined that it is based on the following reason. That is, as shown in FIG. 3, electrodes (terminals, pads) 17 and wires connected thereto are formed on the wiring board 16 by a printing technique, a protective film 19 of an insulating material for the wires is formed, and the electronic components are connected. A small hole 21 is formed in the protective film 19 at the portion of the electrode 17 to be formed, and a solder cream 22 is arranged in the small hole 21. The rectangular air-core coil 14 is disposed on the protective film 19,
13 is arranged on the solder creams 22, 22, the solder cream 22 is melted, and the connection parts 12, 13 are soldered to the electrodes 17.

The protective film 19 has a thickness of, for example, 100 μm.
Conventionally, solder cream 22 is 250-300μ
embedded in the small hole 21 with a thickness of about m
Nos. 2 and 13 were connected by heating and melting the solder in a state in which the solder cream was in reliable contact with the solder cream 22. However, recently, the mounting density on the wiring board 16 has been remarkably improved, and at the time of the solder connection, even a little extra solder is present. Connection, a short circuit between the elements occurs, and there is a possibility that a defective product may occur.

[0007] From such a point, recently solder cream 2
The thickness of Sample No. 2 was about 100 μm. On the other hand, since the connecting portions 12 and 13 have the insulating coating peeled off, the thickness of the insulating coating is, for example, about 10
Although it is only about μm, the contact with the connecting portions 12 and 13 may not always be satisfactorily performed at the time of the heating solder connection process, and thus it is considered that the connection failure occurs.

[0008]

Therefore, in the present invention, the connection portions at both ends of the rectangular air-core coil are shifted outward on the same side from the rectangular external surface of the air-core coil. This displacement may be, for example, about half the diameter of the conductive wire forming the coil.

[0009]

FIG. 1 shows an embodiment of the present invention.
As in the conventional case, the conductive wire 11 coated with the insulating coating is wound in a substantially positive direction cylindrical shape.
2 and 13 are on the same side of the external surface of the coil 11 as
That is, the side to be connected to the wiring board 16 is shifted from the outside by only Δ. This shift is from 10 μm
Although it may be about several tens of μm, for convenience of manufacture, for example, it is about half the diameter of the conductive wire 11 constituting the coil 14, that is, about 0.4 to 0.6 mm. The conductive wire 11 is the same as the one used conventionally, for example, an enameled wire, and the end surface of the rectangular air-core coil 14 is, for example, a square having a side of approximately 5 mm.

In such an air-core coil, the length of the conductive wire is determined in advance instead of winding the conductive wire 11 around the prism core.
After peeling off the insulating coatings at both ends, each time the conductive wire is extruded by an extruder for a certain length, the extruded part is bent at a right angle to form a rectangular air-core coil. The length of one side of the air-core coil is, for example, extra half the diameter of the conductive wire 11, and the extrusion immediately before the last bending of the conductive wire at a right angle is also the same length as the first push, that is, other extrusions It is sufficient to slightly extrude the same amount with respect to the amount. In this case, it is natural that the connection portions 12 and 13 at both ends are located on the same surface side of the rectangular prism in consideration of the number of coil turns and the length of one side of the coil.

[0011]

As described above, according to the present invention, since both connecting portions 12, 13 are slightly shifted outward on the same surface from the external surface of the coil, for example, as shown in FIG. Even if the electrode 22 is drawn from the surface of the protective film 19 in the electrode hole 21 of the protective film 19, the connection portions 12 and 13 always contact the solder cream 22 and the electrode 1
7 is securely connected.

Further, there is no danger that the solder will overflow during the heat treatment during the heat treatment and an electrical short circuit will occur between the adjacent elements, and the occurrence of a defective rate is significantly reduced as compared with the conventional product.

[Brief description of the drawings]

FIG. 1A is a front view showing an embodiment of the present invention, and FIG. 1B is a left side view thereof.

FIG. 2 is a perspective view showing a conventional rectangular air-core coil.

FIG. 3 is a diagram for explaining a problem when a conventional rectangular air-core coil is connected to a wiring board.

Claims (2)

[Claims] 1. A rectangular hollow in which a conductive wire covered with an insulating layer is wound in a rectangular cylindrical shape, and the insulating layers at both ends of the conductive wire are peeled off on the same surface of the rectangular cylindrical shape to form a connecting portion. In the core coil, the connection portions at both ends are shifted outward from the outer peripheral surface of the rectangular cylinder of the square air core coil. 2. The rectangular air-core coil according to claim 1, wherein the amount of displacement of the connection portion is about the radius of the conductive wire.