JPS6216565B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises arranging elongated electrically conductive conductors in the longitudinal direction on both sides of a strip-shaped dielectric material, which are made up of two or more electrically conductive materials, facing each other and spaced parallel to each other. It is an object of the present invention to provide a stripline of this type which has particularly good electric signal transmission characteristics, dimensional stability, and good properties for removing resin portions at the ends.

It is generally known that good electrical signal transmission characteristics can be achieved by using a material with a small dielectric constant and dielectric loss and a small frequency dependence as the dielectric material for such strip lines. Are known. That is, if the dielectric constant used is small, even if the characteristic impedance of the stripline is the same, the structural dimensions of the stripline can be made smaller, and the signal propagation speed becomes faster. The smaller the dielectric loss, the smaller the signal attenuation. Furthermore, if the frequency dependence of the dielectric constant and dielectric loss is small, for example, when a pulse signal is transmitted through the stripline, the waveform rounding of the pulse signal can be kept small.

Therefore, the dielectric material that can be used for the stripline as described above is as described above.
It is required that the dielectric constant and dielectric loss be small, and their frequency dependence should be small.As a material that can satisfy such requirements, a material made of a crystalline polymeric organic material, Materials are known that have a porous microstructure with continuous pores in which a large number of nodules are connected by fibrils as an internal structure, and a large number of voids are formed between these fibrils and nodules. There is. A typical example thereof is expanded porous polytetrafluoroethylene resin (PTFE) produced by the method disclosed in Japanese Patent Publication No. 18991/1983. However, stretched porosity
PTFE is too flexible as a material and has poor shape stability, so for example, it is processed into tape and wrapped around a conductor and used as a dielectric material for coaxial cables, but it has the structure described above. It is unsuitable for use as a dielectric for strip lines.

However, the inventor has developed an expanded porous DTFE
However, as mentioned above, we focused on the fact that it meets all the requirements imposed on stripline dielectrics, such as low permittivity and dielectric loss, as well as low frequency dependence. In order to use expanded porous PTFE as a dielectric material for striplines, and to take advantage of its inherent excellent characteristics, it is possible to ensure the other requirements mentioned above for striplines, that is, shape stability. As a result of various experiments and considerations as to how this should be done, we came up with a new and improved stripline structure according to the present invention.

Briefly, in the present invention, a plurality of electrically good conductors are arranged on both the upper and lower sides of a porous low-k tape, and if necessary, in the middle of the dielectric material, and are arranged in pairs to face each other. The conductors are sandwiched together to form a conductor assembly, over which an outer covering layer of a non-porous or solid plastic material such as PTFE, PFA, FEP, ETFE or polyester is applied to the conductors at both ends of the conductor assembly. The dielectric tape is formed by any suitable method such as integral molding, fusion bonding, or adhesion so as to compress and clamp the dielectric tape.

The invention will now be explained in more detail with reference to the embodiments shown in the drawings.

Referring to FIG. 1, a portion of a stripline is shown in cross-section in accordance with one embodiment of the present invention. In this example, an unfired PTFE tape formed from a mixture of fine PTFE powder and a liquid lubricant by a known process of paste extrusion, rolling, and delubrication is longitudinally heated in an atmosphere at 300°C. A porous low dielectric constant tape 1 made of sintered expanded porous PTFE having a thickness of 0.127 mm was prepared by stretching the tape three times, then heating it to 360° C. while maintaining the stretched state. In this case, the degree of firing of Tape 1 was close to complete firing, and its dielectric constant was 1.3.
Next, 2a: 2a', 2b: 2b', 2
As shown by c: 2c', 2d: 2d', 2e: 2e', five conductor sets consisting of two opposing conductors are placed on both sides of the stretched porous low dielectric constant tape 1 to the same thickness. The conductors of each set are arranged to face each other in the direction, and the conductors of adjacent sets are arranged parallel to and spaced apart from each other and extended in the longitudinal direction. In this case, each conductor 2a: 2a', ......, 2e: 2e' has a width of 0.5 mm,
It was a silver-plated rectangular copper conductor with a thickness of 0.1 mm. Although it has been stated that there are five sets of such conductors, this is only for the convenience of illustration and construction, and it is clear that the number of conductors can be selected as necessary. Will. After each set of conductors is disposed on both sides of the low dielectric constant tape 1 made of expanded porous PTFE, an unfired unstretched sheet with a thickness of 0.25 mm is placed on both sides of the tape 1.
A PTFE tape is applied, and the composite structure thus obtained is passed between at least a pair of crimping rolls (not shown) having convex portions at the ends corresponding to the ends of the assembled conductor, and then heated at 370°C. The material was passed through a sintering tank (not shown). As a result, the corresponding portions of each jacket 3, 3' are
It is made into a concave shape as shown by a and 3a', and the internal dielectric 1 is also made into a crushed shape as shown by 1,
In this state, the outer cover 3, 3' and the low dielectric constant tape 1 are fused and integrated. Due to this shape, the porosity of the crushed portion 1' of the low dielectric constant tape 1 is lowered than that of other portions, and the dielectric constant becomes large, so that the low dielectric constant tape 1 Each assembled conductor 2 is formed by the crushed portion 1' whose dielectric constant is increased, and the jacket 3, 3' which has a higher dielectric constant than the dielectric 1.
a:2a', . Furthermore, by crimping the conductors in each group so as to form a concave shape, deformation due to pressure applied in the thickness direction of the stripline can be prevented.

FIG. 2 shows another embodiment according to the present invention, in which conductors 2a: 2a'...2e: 2 are provided on both sides of a low dielectric constant tape 1 consisting of two sheets 1a and 1b.
An example is shown in which another conductor 2a''...2e'', which is preferably used as a signal line, is provided in the middle of e', and the same effect as above can be obtained.

As can be understood from the above explanation, according to the present invention, it is possible to realize excellent electric signal transmission characteristics with low dielectric constant and dielectric loss, and in addition, it is possible to realize excellent electric signal transmission characteristics on both sides of the low dielectric constant dielectric. By integrally providing a hard insulating layer, it compensates for shape instability caused by the flexibility of the low dielectric constant tape itself, which is made of expanded porous PTFE, and thus provides sufficient shape stability as a whole. It is possible to ensure gender.

Furthermore, for example, the dielectric constant of the insulating layer attached to both sides of a low dielectric constant tape made of expanded porous PTFE and between the assembled conductors is higher than that of the dielectric material, and therefore, the structure with the insulating layer attached thereto is This makes it difficult for the electric field between each set of conductors to be radiated to the outside, which reduces signal crosstalk between layers and line-to-line crosstalk between adjacent strips, which can be a problem when, for example, the striplines according to the present invention are stacked and used. It will be done. In addition, according to the structure of the present invention described above, when processing the ends of the stripline, a sharp object such as a razor or knife may be used in the direction perpendicular to the longitudinal direction of the stripline. Another advantage is that the resin can be easily cut and separated by making a cut with a knife and moving the knife in the longitudinal direction, making the end treatment very easy. It is of course possible to provide an electromagnetic wave shielding layer made of metal or conductive fluororesin on the outer surface of the jacket depending on the purpose.

[Brief explanation of the drawing]

1 and 2 are partial cross-sectional views of striplines showing different embodiments of the invention, respectively. 1: Low dielectric constant tape, 1': Increased dielectric constant part, 2
a, 2a', 2a'' to 2e, 2e', 2e'': conductor, 3,
3': Outer cover, 3a, 3a': Recess.

Claims (1)

[Scope of Claims] 1. A porous low dielectric constant tape, at least one set of conductors arranged in the longitudinal direction consisting of a plurality of conductors arranged oppositely on at least both sides of the tape, and at least one set of the conductors. A stripline comprising an outer sheath that surrounds the conductor assembly and compresses and clamps the porous low dielectric constant tape at both ends of the conductor assembly. 2. The stripline according to claim 1, wherein the outer sheath is provided with compression molded recesses at both ends of the assembled conductor. 3. The stripline according to claim 1 or 2, wherein the porous low dielectric constant tape is made of stretched porous tetrafluoroethylene resin.