JPH11213776A - Thin coaxial cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the terminal working property without damaging excellent high frequency electric characteristic and heat resisting performance by providing a low dielectric constant insulating layer consisting of a porous ethylene tetrafluoride resin insulating layer having a sintered surface on the circumference of a central conductor. SOLUTION: A non-sintered porous ethylene tetrafluoride resin is paste extruded to cover the circumference of a central conductor such as silver plated copper wire to form a nonsintered porous ethylene tetrafluoride layer with a porosity of about 50%. This is sintered for about 3 seconds in a sand bath tank of about 320 deg.C to form a porous ethylene tetrafluoricle resin insulating layer 3 with a coating thickness of about 0.18 mm and an average porosity of about 25%, which consists of a surface sintered layer 3a and a porous layer 3b, whereby an insulator core 4 having an outer diameter of about 0.48 mm is provided. An external conductor layer 5 is provided on the circumference of the insulator core 4 to form a thin coaxial cable 1. The external conductor layer 5 is formed of, for example, Ni-P anchor metal layer 5a and a copper plated metal layer 5b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small-diameter coaxial cable used for a high-frequency transmission line of a small electronic device.

[0002]

2. Description of the Related Art A small-diameter coaxial cable used as a high-frequency transmission line in a small electronic device such as a portable telephone is required to have high flexibility, excellent high-frequency electric characteristics, and easy terminal processing. The general configuration of a small diameter coaxial cable is
The outer periphery of the central conductor is formed by extrusion molding or coating a fluororesin or a polyethylene resin or the like or a tape of the above resin to form a low dielectric constant insulating layer, and an outer metal conductor layer is formed on the outer periphery of the low dielectric constant insulating layer. Is provided. For the outer metal conductor layer, wrap metal tape or wrap a conductor horizontally, or insert a copper pipe into the low-k insulating layer and draw with a die until the copper pipe and the low-k insulating layer are in close contact. An anchor metal layer formed by electroless plating and a good conductive metal layer formed by electroplating on the outer periphery of a low dielectric constant insulating layer as disclosed in Japanese Patent Application Laid-Open No. 6-187847 by the present applicant. And the like formed by application.

[0003]

The small-diameter coaxial cable is
As with other electronic components, when soldering to circuit boards, etc., an automatic soldering method using a reflow furnace has been applied. In place of the solid fluororesin insulator, a porous tetrafluoroethylene resin (PTFE) insulator having good heat resistance has come to be frequently used for the high-rate insulating layer.

However, when the insulating layer of the small-diameter coaxial cable is formed of a porous PTFE insulator, when the porous PTFE insulating layer is peeled off from the center conductor in a ring shape in the terminal processing, the porous PTFE insulating layer is not formed. There has been a problem that it is difficult to reliably peel off the porous PTFE insulating layer in a ring shape by being crushed and stretched by a peeling tool, and there is a problem that the center conductor is damaged at the time of peeling. This is because the rigidity of the porous PTFE insulator is lower than the rigidity of the solid fluororesin insulator.

Therefore, an object of the present invention is to improve the terminal processability without impairing the excellent high-frequency electrical characteristics and heat resistance, and to form a porous PTFE insulating layer without damaging the center conductor during terminal processing. An object of the present invention is to provide a small-diameter coaxial cable that can be surely cut off in a round slice.

[0006]

In order to solve the above-mentioned problems, a small-diameter coaxial cable according to the present invention relates to a small-diameter coaxial cable in which a low dielectric constant resin insulating layer and an external metal conductor layer are sequentially provided on the outer periphery of a center conductor. The low dielectric constant resin insulating layer is formed by a porous PTFE insulating layer having a sintered surface.

[0007]

The thin coaxial cable of the present invention is characterized in that the surface of the porous PTFE insulating layer is sintered to form a solid outer skin on the surface of the insulating layer as a means for improving the rigidity of the porous PTFE insulating layer having poor rigidity. Is what you do. Since the sintered body has the same rigidity as the solid body, the rigidity of the surface of the porous PTFE insulating layer is increased by the sintered layer. Since the rigidity of the surface of the porous PTFE insulating layer is increased, the blade of the peeling tool can be inserted deep into the porous PTFE insulating layer without crushing the porous PTFE insulating layer during terminal processing.
The porous PTFE insulating layer can be reliably and easily stripped off from the center conductor without forcibly stretching the insulating layer. Therefore, there is no risk of damaging the center conductor during peeling. Further, since the inner layer other than the surface layer of the porous PTFE insulating layer is formed of a porous body as it is, the high-frequency electric characteristics and the heat resistance are not significantly impaired.

In the above-mentioned small diameter coaxial cable, if the porosity in the surface-sintered porous PTFE insulating layer is gradually reduced from the inner layer to the surface, the porous PTFE insulating layer in contact with the center conductor is formed. Is formed in a high porosity state, so that the adhesion strength between the porous PTFE insulating layer and the center conductor does not increase, which is preferable.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the drawings. Note that the present invention is not limited by this.

FIG. 1 is a cross-sectional view showing one embodiment of the small diameter coaxial cable of the present invention. Unsintered porous PTFE is applied to the outer periphery of the center conductor 2 of a silver-plated copper wire having an outer diameter of 0.12 mm.
The resin is subjected to paste extrusion coating to form an unsintered porous PTFE layer having a porosity of 50%, which is sintered in a sand bath at 320 ° C. for 3 seconds to have a surface sintered layer 3a and a porous layer 3b. Porous 4 having a coating thickness of 0.18 mm and an average porosity of 25%
The insulating layer 3 having an outer diameter of 0.48 is formed.
The insulator core 4 of mm is obtained. An outer conductor layer 5 is provided on the outer periphery of the obtained insulator core 4, and the small-diameter coaxial cable 1
Is formed. As the external conductor layer 5, for example, there is a metal plating conductor layer. The means for forming the outer conductor layer 5 by metal plating is briefly described. First, the insulator core 4 is activated in a metal sodium-naphthalene complex solution at a liquid temperature of 10 ° C. for 0.26 seconds. A 1 μm-thick Ni—P anchor metal layer 5 a is applied to the outer periphery by electroless plating, and a 60 μm-thick copper-plated metal layer 5 b is applied to the anchor metal layer 5 a by electroplating. The conductor layer 5 is formed. The outer diameter of the obtained small diameter coaxial cable 1 in this case was 0.602 mm. As the outer conductor layer 5, in addition to the above-mentioned metal-plated outer conductor layer, as described above, a layer formed by overlapping and winding a metal tape, a layer formed by winding a conductor horizontally, or a copper pipe is formed. And others. Although the metal-plated outer conductor layer has been exemplified in the embodiment of the present invention, it is needless to say that any outer conductor layer may be used. Also, the porous PTFE resin insulating layer 3 is obtained by pasting and extruding the unsintered porous PTFE resin of the example, and also wrapping and winding an unsintered porous PTFE resin tape. May be formed by surface sintering. In FIG. 1, the porous PTF is used.
The E resin insulating layer 3 shows an example in which the porosity is gradually reduced from the inner layer toward the surface.

[0011]

According to the small diameter coaxial cable of the present invention, since the low dielectric constant insulating layer is formed of the porous PTFE insulating layer whose surface is sintered, the porous PTFE insulator has excellent high-frequency electrical characteristics and heat resistance. And the rigidity, which is a disadvantage of the porous PTFE insulator, is increased. By increasing the rigidity of the surface of the porous PTFE insulating layer, the peeling tool prevents the porous PTFE insulating layer from being crushed or forcibly stretched during the terminal processing, and damages the center conductor. The porous PTFE insulating layer can be reliably and easily stripped off from the center conductor without any trouble. Further, since the inner layer side of the porous PTFE resin insulating layer in contact with the center conductor is formed of a porous body, the adhesion between the center conductor and the porous PTFE resin insulating layer does not become excessive.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a small-diameter coaxial cable according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 small diameter coaxial cable 2 center conductor 3 porous PTFE resin insulation layer 3a sintered layer 3b porous layer 4 insulator core 5 outer conductor layer 5a electroless plating anchor metal layer 5b electroplating metal layer

Claims (4)

[Claims] 1. A small-diameter coaxial cable in which a low dielectric constant resin insulating layer and an external metal conductor layer are sequentially provided on the outer periphery of a center conductor, wherein the low dielectric constant resin insulating layer is formed of a porous 4-fiber having a sintered surface. A small-diameter coaxial cable characterized by being formed of an insulating layer of ethylene resin. 2. The surface-sintered porous tetrafluoroethylene resin insulating layer is formed such that the porosity decreases gradually from the inner layer to the surface of the insulating layer. The described small diameter coaxial cable. 3. The porous tetrafluoroethylene resin insulating layer is obtained by sintering the surface of a paste-extruded unsintered porous tetrafluoroethylene resin insulator. The small-diameter coaxial cable according to claim 2. 4. The porous tetrafluoroethylene resin insulating layer is formed by sintering the surface of an unsintered porous tetrafluoroethylene resin tape insulator wound in an overlapped manner. Or the small diameter coaxial cable according to claim 2.