JP3522513B2 - Flat cable and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat type cable suitable for a high frequency circuit configuration in which signal line noise is effectively prevented.

[0002]

2. Description of the Related Art With the miniaturization of electronic devices, miniaturization of high-frequency oscillators is required. In response to such demands, in a high frequency oscillator,
Flat type cables in which dielectric layers having signal wiring (strip lines) are laminated have been developed. By the way, when a plurality of signal wirings are formed (inner layer) in the laminated dielectric layer, signal radiation may occur and adversely affect other signal wirings. In addition, external electromagnetic noise may affect the wiring circuit including the signal wiring, causing malfunction.

In order to solve such a problem, as shown in FIG. 7 which is a cross-sectional view of the structure of a main part, a shield wire 4 formed by laminating an insulating layer 2 and a shield layer 3 concentrically with the signal wire 1 as a center line is arranged in parallel. And cover them with the insulator 5.
An integrated configuration has been proposed. Here, the signal wiring (center conductor) 1 is, for example, a tin-plated soft copper wire or a silver-plated alloy copper wire with a diameter of about 120 μm, and the shield layer 3 is a tin-plated soft copper wire mesh with a diameter of about 260 μm and a diameter of 260 μm. It is formed as a shielded wire 4 of a degree. Furthermore, the parallel arrangement of the shielded wires 4 is
The pitch is about 1.27 mm, and the thickness is about 1.27 mm when covered and integrated with the insulator 5 (for example, polyvinyl chloride resin).

[0004]

However, in the case of the above flat type cable, although the influence due to the signal wiring can be reduced, the following problems are still raised. In other words, in order to meet the demand for circuit compactness and high functionality, this type of flat cable is required to have a high density or a fine signal wiring pattern. However, in order to reduce the size or increase the density, complicated processing operations and fine and highly accurate processing are required, and there is a concern about a significant increase in manufacturing cost and reliability.

In other words, it is very difficult to reduce the size and cost with the structure shown in FIG. That is, the dimensional stability and the densification of the shielded wire 4 having a small diameter, the formation and the formation of the shielded wire 4 in parallel, and the covering and integration of the shielded wire 4 with the insulating layer 5 are significantly limited. Further, in the structure shown in FIG. 7, when connecting the connector to the cable end, it is necessary to connect each signal wiring to each connector terminal by soldering, which causes a cost increase. Moreover, there is a limit to flexibility.

On the other hand, as a means for stabilizing the signal wiring disposed in the inner layer of the insulator layer, the signal wiring is sandwiched between a pair of shield layers from above and below, and these shield layers are provided in the peripheral portion of a plurality of vertical shield conductors. A configuration has been proposed in which (via connection portion) is electrically connected (Japanese Patent Laid-Open No. 8-78912).
Issue). That is, the pair of shield layers sandwiching from the up and down direction blocks unnecessary radiation in the vertical direction of the signal wiring, and the vertical shield conductor blocks unnecessary radiation on both side surfaces of the signal wiring.

However, in the structure in which the signal wiring is shielded from the upper and lower sides and the left and right sides, in the peripheral portion of the shield layer, when vertically connecting with the via connecting portion conductor, a required hole is preliminarily drilled at a corresponding position. However, it is premised that a conductor film or the like is formed in this hole by through-hole plating. Due to the requirement of flexibility, the insulator layer is based on polyimide resin, but it is difficult to drill a small-diameter sheet with a small film thickness, and further, in through-hole plating, the quality of the inner wall surface of the drilled hole is high.・ Because the properties are important, careful drilling is desired. The above-mentioned careful drilling process inevitably causes an increase in cost. In addition, since the punching pitch cannot be reduced, there is a limit to downsizing.

Instead of drilling, a small diameter hole is drilled in the insulating base material by laser processing, and then,
It is possible to form the shield layer by vapor deposition or plating, but the combined use of laser processing causes a significant increase in cost. In addition, when the insulating layer is a polyimide resin base, there is a problem that the hygroscopicity of the insulating layer easily changes the dielectric constant, and thus stable frequency characteristics cannot be obtained.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a flat type cable which can be manufactured by a simple process and has a highly reliable shield property.

[0010]

According to a first aspect of the present invention, a plurality of signal wirings are arranged in an insulating layer made of a liquid crystal polymer, and the signal wirings are sandwiched in the thickness direction and arranged in the insulating layer. A flat type cable having a shield layer pair and a via-type connecting portion that is arranged at multiple points in the side surface side insulator layer of each of the signal wirings and electrically connects between the shield layer pairs, The via-type connecting portion for electrically connecting the pair of shield layers is a flat type cable characterized in that the via-type connecting portion is formed by a conductive bump press-fitted and passed through an insulating layer.

According to a second aspect of the present invention, there are provided a plurality of signal wirings which are inner layers and arranged in an insulating layer made of a liquid crystal polymer, and a shield layer pair which is arranged in the insulating layer with the signal wirings sandwiched in the thickness direction. , The inner layer in the side surface side insulator layer of each of the signal wiring
What is claimed is: 1. A flat type cable having a shield pattern arranged and a multi-point via type connecting portion electrically connecting the shield pattern and the shield layer, respectively, wherein the shield pattern and the shield layer are electrically connected. The via type connection portion is a flat type cable characterized in that it is made of a conductive bump which is press-fitted and passed through an insulating layer.

According to a third aspect of the present invention, in the flat type cable according to the first or second aspect, the insulating layer is formed by fusing or laminating liquid crystal polymer sheets having different melting points. .

In the above invention, the signal wiring and the shield layer are formed of a conductive metal such as copper or aluminum, and are generally formed of a foil or thin layer having a thickness of about 5 to 35 μm.

In the above invention, the insulator layer for arranging the signal wiring of the flat type cable as an inner layer is a so-called liquid crystal polymer, for example, Vectran A type (melting point).
285 ℃), Vectran C type (melting point 325 ℃)… Both (manufactured by Kuraray Co., Ltd.), BIAC film (melting point 335 ℃)…
It is commercially available as manufactured by Japan Gore-Tex Co., Ltd. Liquid crystal polymer is a stable thermoplastic material that has almost no hygroscopicity and a dielectric constant of approximately 3.0 (1MHz). The copper foil) and the conductive bump can be easily electrically connected.

When the insulating layer is formed of a plurality of laminated layers, a combination of the same kind of liquid crystal polymers or a combination of different kinds of liquid crystal polymers may be used. Especially, when a heating step is required, the melting point is relatively high. It is preferable to later combine a liquid crystal polymer with a liquid crystal polymer having a relatively low melting point.

In the above invention, the conductive bumps which penetrate the liquid crystal polymer insulating layer by pressure and electrically connect the opposing shield layers or the shield layer and the shield pattern are formed of a conductive composition. And is formed by the following means. For example, a projection (columnar body) having a high aspect ratio is formed at a peripheral portion of the conductive metal foil where the shield layer is formed or at a predetermined position of the shield pattern by a printing method using a relatively thick metal mask. And
The height, diameter, and distribution of the protrusions or columnar bodies are appropriately set according to the configuration of the through-hole type conductor portion to be formed.

Specifically, the liquid crystal polymer is determined in consideration of the arrangement and structure of the conductive bumps that penetrate the finally formed liquid crystal polymer insulating layer, and in the case of press-fitting from both sides, the liquid crystal polymer is used. 120 to 200% of the system insulator layer thickness,
In the case of press-fitting from one side, a height of about 180 to 400% of the thickness of the liquid crystal polymer insulating layer is preferable. In addition,
The protrusions (pillars) are arranged, for example, on a stainless steel plate having a thickness of about 5 mm at a predetermined position by arranging a mask having a hole of 0.3 mm on the entire surface of the housing, and the conductive composition housed in the housing. It is formed by a stamp method or the like in which a substance (paste) is pressed and pushed out from the hole of the mask.

Here, the conductive resin paste is prepared, for example, by mixing conductive powder such as silver, gold, copper, solder powder, alloy powder or composite (mixed) metal powder of these, and a resin binder component. The pasted pastes are listed. Examples of the resin binder component generally include thermoplastic resins such as polycarbonate resin, polysulfone resin, polyester resin, and phenoxy resin, and thermosetting resins such as phenol resin, polyimide resin, and epoxy resin. Others, acrylic acid esters such as methyl methacrylate, diethyl methyl methacrylate, trimethylolpropane triacrylate, diethylene glycol diethyl acrylate, methyl acrylate, ethyl acrylate, diethylene glycol ethoxylate acrylate, ε-caprolactone-modified dipentaerythritol acrylate, Examples thereof include ultraviolet curable resins such as methacrylic acid esters and electron beam irradiation curable resins.

According to the first aspect of the present invention, the electrical connection of the shield layer to the signal wiring arranged in the inner layer of the liquid crystal polymer layer is made by the conductive bumps press-fitted and passed through the liquid crystal polymer layer at a plurality of points. . In other words, since the opposing shield layers are connected by press fitting / passing of fine conductive bumps and adopting a form reinforced by the liquid crystal polymer layer, fine shields are possible and a highly reliable shield is provided. It functions as a flat cable that has been given the property.

According to the second aspect of the present invention, the electrical connection of the shield layer to the signal wiring disposed inside / arranged in the liquid crystal polymer layer is such that the electrical conductivity is obtained by press-fitting / passing through the liquid crystal polymer layer at a plurality of locations via the shield pattern. Made of bumps. In other words, since the opposing shield layers are connected by press fitting / passing of fine conductive bumps and adopting a form reinforced by the liquid crystal polymer layer, fine shields are possible and a highly reliable shield is provided. It functions as a flat cable that has been given the property.

According to the third aspect of the invention, the combination of the liquid crystal polymer having a relatively high melting point and the liquid crystal polymer having a relatively low melting point not only facilitates the production but also provides a flat type cable having finer signal wiring. Function.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment will be described with reference to FIGS.

FIG. 1, FIG. 2 and FIG. 3 show the essential structure of the flat type cable according to the first embodiment. FIG. 1 is a transverse sectional view, and FIG. 2 is a sectional view taken along line AA of FIG. 3 and 4 are top views. In FIGS. 1, 2 and 3, 6 is a plurality of signal wirings which are inner layers and are arranged in an insulating layer 7 made of liquid crystal polymer, and 8 and 9 are insulating layers 7 sandwiching the signal wirings 6 in the thickness direction. The shield layers 10a and 10b are the inner and inner shield patterns of the side surface insulating layer 7 of each signal wiring 6. Here, the signal wiring 6 and the shield patterns 10a and 10b are sheet-like liquid crystal polymers.
It is formed by patterning a copper foil with a thickness of 18 μm that is integrally arranged on the 7a surface. Signal wiring 6 width 100 μm, shield patterns 10a and 10b width 500 μm, signal wiring 6 pitch 6
At 00 μm, the thickness is about 130 μm.

Further, 11 is the shield pattern 10a, 1
This is a via-type connection portion that electrically connects the 0b and the shields 8 and 9 layers. Here, the via-type connection portion 11 is formed and arranged intermittently in a substantially conical shape using, for example, silver powder as a conductive component, epoxy resin as a binder component, and conductive paste as a material, and an insulator at a plurality of locations. The layer 7 is press-fitted / passed through and electrically connected (joined) to the opposing shield layers 8 and 9.

In this configuration example, the shield pattern
The configuration is such that 10a and 10b are electrically connected to the shield layers 8 and 9 located above and below the signal wiring 6 via the conductive bumps 11 which are pressed and passed through the interlayer insulating layer 7. That is, each signal wiring 6 has a structure in which a 360 ° circumference is three-dimensionally surrounded by a shield conductor in a cross section, as in the case of a flat shield cable.

Next, an example of a method of manufacturing the flat type cable having the above structure will be described.

First, the first shield layer (for example, the thickness 18
A plurality of conductive bumps 9 are provided at intervals (intermittently) on one main surface of the copper foil 8 of 8 μm, that is, at a predetermined shield position. For example, a metal mask made of stainless steel and having a thickness of 300 μm, which is formed by forming a hole having a diameter of 0.3 mm on one main surface of the copper foil 8, is positioned and arranged, and a conductive paste of silver powder-epoxy resin is printed. . After drying the printed conductive paste, print at the same position using the same mask, repeat the drying process three times, and then heat-cure it to obtain the height
A first conductive bump group of about 0.3 mm is formed.

Then, a first conductive metal foil (for example, a copper foil having a thickness of 18 μm) is laminated / arranged on the first conductive bump group formation surface via the first sheet-shaped liquid crystal polymer 7a, This laminated body is integrated under pressure. By this pressure integration operation, the tip end of the first conductive bump is inserted into the first sheet-shaped liquid crystal polymer 7a and the opposite thickness is 18 μm.
The copper foil is electrically connected to the copper foil to prepare a double-sided copper-clad board.

Then, the integrated first conductive metal foil (copper foil) surface is subjected to etching resist patterning,
For example an aqueous solution of ferric as chloride etchant, the copper foil of the unnecessary portions removed by etching. Then etch
By removing the grayed resist, to form a shield pattern 10a, 10b for signal lines 6 and the signal wiring shield. A second conductive bump group is formed (intermittently) on the surfaces of the formed shield patterns 10a and 10b so as to be separated from each other (intermittently). The formation of the second conductive bump group is performed in a process similar to that of the first conductive bump group formation.

After forming the second conductive bump group,
A second conductive metal foil (for example, a thickness of 18 μm) is formed on the second conductive bump group formation surface via the second sheet-shaped liquid crystal polymer 7b.
m copper foil) is laminated and arranged. Then, the laminate is integrated under pressure, and the tip end of the second conductive bump is electrically connected to the opposing second conductive metal foil by inserting the second sheet-shaped liquid crystal polymer 7b. and patterning the second conductive metal foil, by forming a second shield layer 9, the configuration of the flat cable shown in FIG. 1 to FIG. 3 is obtained.

In the case of the flat type cable having the above structure,
In particular, since the insulator layer 7 is formed of a liquid crystal polymer having a low dielectric constant, not only the high frequency characteristics are stabilized, but also low hygroscopicity and good flexibility make it light, thin, compact and reliable. It had a high function.

In the above manufacturing example, the signal wiring 6 and the shield patterns 10a and 10b for shielding the signal wiring are provided.
When the signal wiring 6 is formed in the first sheet-shaped liquid crystal polymer 7a by hot pressing the surface on which the signal wiring 6 is formed, the signal wiring 6 and the shield patterns 10a and 10b are misaligned. It is possible to easily prevent deformation and the like.

FIG. 4 is a sectional view showing the structure of the main part of a flat type cable according to the second embodiment. This second
The flat cable according to the embodiment of, except for some common shielding of the signal wiring 6, basically, the first embodiment
The configuration is similar to that of. That is, each signal wiring 6 has a structure in which the circumference 360 ° is three-dimensionally surrounded by a shield conductor in cross section, but the shield pattern 10a and the conductive bump 11 between the adjacent signal wirings 6 are shared. , The structure is simplified.

Although the shield patterns 10a are arranged in the structures shown in FIGS. 1 to 4 above, in this case, the insulating layer 7 serves to share the potential in the middle thereof. There are advantages. That is, a series of via-type connecting portions in the longitudinal direction of the signal wiring 6 are electrically connected at the intermediate position.
By the position, more stable frequency characteristics can be obtained. Further, FIG. 5 is a cross-sectional view showing the main configuration of the flat type cable according to the third embodiment. In the flat type cable according to the third embodiment, the shield pattern for each signal wiring 6 is omitted, the shield layers 8 and 9 are electrically connected only by the conductive bumps 11, and each signal wiring 6 is connected. to, on the section, the other being a structure in which surrounded around 360 ° three-dimensional shielded conductor, and has a basically similar to the case <br/> the first embodiment configuration. That is, the first embodiment
In the case of the above configuration, the conductive bump 11 is provided on one surface of the shield layer 8 or 9 and is connected to the opposing shield layer 9 or 8 surface by penetrating the liquid crystal polymer layers 7a, 7b at the tip thereof. In view of the cross section, the structure is such that the circumference 360 ° is three-dimensionally surrounded by the shield conductor.

In each of the above structural examples, the shield layers 9 adjacent to each other are arranged substantially linearly and separated from each other. However, as shown in the top view of FIG. The mutual separation may be a meandering type.

Also in the case of the flat type cable having the structure shown in FIGS. 4 to 6, the high frequency characteristics are stabilized especially when the insulating layer 7 is formed of the liquid crystal polymer having a low dielectric constant. Not only that, due to its low hygroscopicity and good flexibility, it was thin, compact, and reliable in function.

As shown in the above example of the manufacturing method, the second sheet-shaped liquid crystal polymer 7b is thermally fused to the first sheet-shaped liquid crystal polymer 7a having the signal wiring to be integrated. Since the liquid crystal polymers 7a and 7b are thermoplastic, if the first sheet-shaped liquid crystal polymer 7a is also softened or melted during thermocompression bonding, the signal wiring 6 may be deformed or bent. Therefore, the width of the signal wiring 6 cannot be reduced so much, and the hot press condition becomes delicate. Therefore, it is desirable that the first sheet-shaped liquid crystal polymer 7a provided with the signal wiring 6 having a small wiring width is selected to have a relatively high melting point. That is, even when the second sheet-shaped liquid crystal polymer 7b is in a molten state, the first sheet-shaped liquid crystal polymer 7a is
It is good to choose a material that does not soften or flow.

The present invention is not limited to the above examples, and various changes can be made without departing from the gist of the invention. For example, a flat cable configuration
The dimensions, the signal wiring, the shield layer, the material of the shield pattern, the material for forming the conductive bumps, and the like can be appropriately selected and used according to the application.

[0039]

According to the invention of claim 1, the liquid crystal polymer constituting the insulator layer has a low dielectric constant and good high frequency characteristics, and has almost no hygroscopicity and exhibits a stable function. Furthermore, a flexible flat cable can be easily provided due to the fact that the conductive bumps can be inserted with high precision with minute or fine conductive bumps.
In other words, it is possible to improve the performance of the high-frequency signal circuit and the like by providing the flat type cable of low cost, light weight and high density wiring at low cost.

According to the second aspect of the present invention, the liquid crystal polymer forming the insulator layer has a low dielectric constant and good high frequency characteristics, has almost no hygroscopicity and exhibits a stable function, and has flexibility. It is possible to provide a highly reliable flat type cable because it is possible to insert a minute or fine conductive bump with high precision, and further due to the insertion / arrangement of a shield pattern. In other words, by providing a low-cost, light, thin, and high-density wiring flat type cable, it becomes possible to easily improve the performance of a high-frequency signal circuit and the like.

According to the third aspect of the present invention, the combination of the liquid crystal polymer having a relatively high melting point and the liquid crystal polymer having a relatively low melting point not only facilitates manufacturing but also has a flat type having finer signal wiring. Cables are provided.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a main-part configuration of a flat type cable according to a first embodiment.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a top view of a main part of the flat type cable illustrated in FIG.

FIG. 4 is a cross-sectional view showing a configuration of a main part of a flat type cable according to a second embodiment.

FIG. 5 is a cross-sectional view showing the main configuration of a flat type cable according to a third embodiment.

FIG. 6 is a top view showing a configuration of main parts of a flat type cable according to another embodiment.

FIG. 7 is a cross-sectional view showing a main part structure of a conventional flat type cable.

[Explanation of symbols]

6 ... Signal wiring 7, 7a, 7b ... Insulator layer (liquid crystal polymer layer) 8, 9 ... Shield layer 10a, 10b ...... Shield pattern 11 …… Via connection

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Claims (3)

(57) [Claims] 1. An inner layer formed on an insulating layer made of a liquid crystal polymer.
A plurality of signal wirings arranged, a shield layer pair arranged in the insulating layer sandwiching each signal wiring in the thickness direction, and arranged at multiple points in the side insulating layer of each signal wiring, A flat type cable having a via-type connecting portion electrically connecting between the shield layer pairs, wherein the via-type connecting portion electrically connecting between the shield layer pairs is press-fitted / passed through the insulating layer. A flat cable that is made of conductive bumps. 2. An inner layer formed on an insulating layer made of a liquid crystal polymer.
A plurality of signal wirings arranged, a shield layer pair arranged in the insulating layer sandwiching each signal wiring in the thickness direction, a shield pattern arranged in the side surface insulating layer of each signal wiring, A flat type cable having a multi-point via type connecting portion electrically connecting the shield pattern and the shield layer respectively, wherein the via type connecting portion electrically connecting the shield pattern and the shield layer is an insulating layer. A flat type cable characterized by being made of conductive bumps that have been pressed into and passed through the body layer. 3. The flat type cable according to claim 1, wherein the insulating layer is formed by fusing or laminating liquid crystal polymer sheets having different melting points.