JPH0770252B2 - Thermal adhesive flexible wiring member - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat-adhesive flexible wiring member, and more particularly to a heat-adhesive flexible wiring member useful as a connecting component for electronic devices.

(Prior art and its problems) Flexible wiring members are used for connecting a display (LCD, EL, LED, ECD, plasma display, etc.) to a PCB (rigid printed wiring board), or between PCBs. However,
In recent years, the number of circuits has increased with the increase in size, color, and miniaturization of displays. Conversely, the pitch with the connection pattern is 0.3 mm.
The table is becoming smaller, 0.2 mm.

In a conventional flexible wiring member, a copper foil is joined to an insulating flexible film with an insulating adhesive, and the circuit is formed by etching the copper foil. When the width or the conductive interval is reduced, the conductor becomes too thin due to overetching and is broken, or etching residue remains between the conductors to cause leakage. In addition, since conductive material such as copper foil generally uses electrolytic copper, it has poor flexibility and makes processing difficult. In the case of etching, various complicated steps must be performed, and the etching deteriorates the adhesive strength between the conductor and the adhesive, and variations in concentration, time, etc. cause pitch, conductive width, peel strength, and tolerance. It is easy for the current to fluctuate.

Also, when conductive paste such as silver paste is screen-printed to form a circuit, the printing limit is about 0.30 mm, and if it is less than 0.30 mm, the circuit cannot be formed at all.
In that case, wire breakage and leakage occur, so the yield is poor, stable production is not possible, and productivity is poor.

(Structure of the Invention) The present invention relates to a heat-adhesive flexible wiring member that solves such disadvantages, and it is a non-stretch insulating flexible film having a film thickness (T) of heat. An adhesive adhesive layer is provided, and a plurality of cross-sectional wire diameters (D) are 10 to 10
A round metal wire having a size of 50 μm is partially embedded in the adhesive layer, and the arrangement pitch (Pc) and the connected electrode terminal electrode width (W) are expressed by the formula T ≦ D <Pc <1 / 2W. It is characterized in that they are arranged so as to have the relationship shown.

That is, the inventors of the present invention have conducted various studies to develop a wiring member having a low connection circuit resistance, high contact stability, and high reliability, and as a result, a non-stretch insulating flexible film has a film thickness (T) of Adhesive Adhesive layer is adhered as a base material, and round metal wires are arranged in parallel in this adhesive layer so that a part of its cross section is embedded in the adhesive layer. When the electric and electronic parts to be electrically connected are arranged and hot pressed, they adhere to the electric and electronic parts and are electrically connected by the metal round wire, but this insulating flexible film is not stretchable. Since the metal round wire is arranged in this, according to this, even if a force is applied in the arrangement direction of the metal round wire, there is no displacement or peeling, and therefore the contact resistance is low and the contact We found that we could obtain excellent stability, When the cross-sectional diameter of the metal round wire is D, the wiring pitch is Pc, and the connected electrode terminal electrode width is W, the relationship between them is T ≦ D <Pc <1 / 2W For example, the arrangement pitch can be made small, and a plurality of metal round wires come into contact with the electrode terminals to be connected. Therefore, the reliability of the contact was confirmed to be improved, and the present invention was completed.

Examples of the non-stretchable insulating flexible film that constitutes the heat-bondable flexible wiring member of the present invention include polyimide, polyester, aramid, polycarbonate, prephenylene sulfide, glass fiber-containing epoxy, and ethylene-vinyl acetate copolymer. , And those made of synthetic resin such as polymethylmethacrylate, but considering the flexibility and workability at the time of wiring, the polyester film is most preferable among them, and the thickness of these films is In consideration of the above, it may be 10 to 50 μm, but preferably 10
It is preferable to set the thickness to 25 μm.

The heat-adhesive adhesive applied to this insulating flexible film is thermoplastic as long as it exhibits adhesiveness by heat activation,
It may be thermosetting. However, thermoplastics have the advantage of bonding at a relatively low temperature and heating for a short time, but they have the disadvantage of poor heat resistance. Thermosetting resins have high adhesive strength and heat resistance. It is excellent, but has a short pot life and high adhesion conditions.
These are disadvantageous in that they take a long time, so these may be appropriately selected according to the purpose of use.

Examples of the thermoplastics include polyamides, polyesters, ionomers, polyolefins such as EVA, EAA, EMA, and EEA, various synthetic rubbers, and modified products and composites thereof. Examples of the flexible resin include epoxy resin-based, urethane-based, acrylic-based, silicone-based, chloroprene-based, nitrile-based, etc. synthetic rubbers and mixtures thereof. Agents, control agents, deterioration inhibitors, heat resistance additives, thermal conductivity improvers, tackifiers, softeners, colorants and the like may be added as appropriate.

The round metal wire used here is copper, stainless steel,
A metal wire such as phosphor bronze, beryllium copper, or nickel, or a round wire formed by plating these metal wires with gold, silver, palladium, rhodium, or the like may be used. Unevenness and disconnection during wiring work, resulting in a low yield. Further, when the contact state with the electrode terminal to be connected is a round wire, the contact is a wire contact, which is advantageous in that a sufficient contact pressure can be obtained. This product has a circular cross-sectional shape, and the cross-sectional wire diameter (D) is the width of the connected electrode terminal (W).
It is better to be 1/2 or less. The wire diameter is preferably as small as possible since it is preferably flexible, but the wire diameter is 10 to 50 μm, preferably 20 in view of the wiring workability and the resistance value. It is preferable that the thickness is about 30 μm. There is also a method of making this connection using a pressure-sensitive anisotropic conductive film in which conductive particles are dispersed and arranged in a non-conductive rubber-based resin matrix, but this conventional method uses conductive particles and terminals. Since the contact area of is small, the connection part may become unstable and there may be a disadvantage in conduction,
If the conductive particles are increased, the connecting portion becomes brittle and easily shaken, resulting in insufficient conduction. However, if this is a metal round wire having a cross-section wire diameter of 10 to 50 μm, such a disadvantage occurs. Is excluded.

Next, the manufacturing method of the heat-adhesive flexible wiring member of the present application will be described. This method first forms a heat-adhesive adhesive layer on the above-mentioned insulating flexible film. Method of laminating the adhesive layer on the roll by the above, after mixing or printing the adhesive with a solvent and coating,
This can be achieved by a method of removing the solvent to obtain a coverlay film. In this case, a commercially available product in which the adhesive layer is already laminated on the film may be applied. Arrangement of the metal round wire to this adhesive layer is one, a method of arranging while applying tension for each one pitch, or after wrapping the coverlay film around the rotating drum,
There is a method in which a metal round wire is sent out and wound around the film while moving in the axial direction of the drum to form a coil. At that time, if the coverlay film itself has adhesiveness, the metal round wire is temporarily fixed as it is, but if not, the solvent is sprayed and the adhesive is made a viscous body to be temporarily fixed. Next, this is subjected to hot pressing to achieve the curing of the adhesive and the embedding of the metal round wire in the adhesive layer. In addition,
The degree of embedding of the metal round wire can be controlled by the spacer, but if the metal round wire having the relationship of D and T described above is selected, it will not be buried in the adhesive layer and the metal round wire will be within a predetermined range. Can be stopped.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

FIG. 1 and FIG. 2 are longitudinal sectional views of the heat-bondable flexible wiring member of the present invention, in which the heat-bondable adhesive is applied onto the non-stretchable insulating flexible film 1. Agent 2 with a film thickness of 10-50
The adhesive layer 2 is coated with metal round wires 3 so that a part thereof is embedded in the adhesive layer 2. However, if the thickness (T) of the adhesive layer 2 is larger than the cross-sectional wire diameter (D) of the metal round wire 3, the wire is buried in the adhesive layer during wiring of the metal round wire 3 and the surface thereof is Since it is covered with an insulating adhesive, the contact with the electrode terminal to be connected becomes incomplete, and when the heat-adhesive flexible wiring member is hot pressed, the metal round wire moves and the desired arrangement is achieved. Since the pitch (Pc) cannot be maintained, it is necessary that T ≦ D, preferably 10 μm ≦ T ≦ 4 / 5D.

The use of this material is, for example, as shown in the longitudinal sectional view of FIG. 3, made by screen printing of a conductive paste or the like on the heat-bondable flexible wiring member shown in FIGS. 1 and 2. The flexible electrode terminal 4 is mounted, and according to this, the flexible electrode terminal 4 is connected to the adhesive layer 2 and comes into contact with the metal round wire 3 to form the wiring member and the flexible electrode terminal 4. Are electrically connected, but the electrode width W of the flexible electrode terminal 4, the cross-sectional diameter D of the metal round wire 3 and the array pitch (Pc) are set to D <Pc <1 / 2W. Therefore, the flexible electrode terminal 4 comes into contact with at least two metal round wires, and the electrical connection becomes stable. The flexible electrode terminal 4 is provided corresponding to the connected electrode terminal, and the contact with the connected electrode terminal is made through the flexible electrode terminal 4, so that the surface of the connected electrode is sufficiently contacted. Since they follow, the contact stability becomes high, and the advantage that expensive precious metal plating need not be applied on the metal round wire is given. Further, FIG. 4 is a longitudinal sectional view of a wiring member having the flexible electrode terminal 4 shown in FIG. 3 coated with an anisotropic conductive adhesive 5 containing conductive particles 6. As shown,
This product has an anisotropic conductive adhesive 5 on the flexible electrode terminal 4.
Is arranged, so that it is useful for electrical connection with other electrode terminals placed thereon.

FIG. 5 is a plan view of the heat-adhesive flexible wiring member of the present invention provided with the flexible electrode terminals 4 as shown in FIG. 3, and FIG. 6 is a cross sectional view thereof. Is shown,
The metal round wires 3 are arranged in parallel at an arrangement pitch (Pc), but the portions of the metal round wires 3 that are not in contact with the electrode terminals 4 are chemically treated by etching or the like as shown in the figure. It is preferable to remove it by a treatment, which can completely eliminate the occurrence of leakage between adjacent electrodes.

FIG. 7 is a vertical cross-sectional view showing the usage of the wiring member of the present invention, in which the arrangement pitch (Pc) of the metal round wires 3 in the wiring member is the width of the connected electrode terminal 9 ( W)
Is shown in contact with a plurality of.

(Effects) The heat-adhesive flexible wiring member of the present invention is configured as described above, and the round metal wires having a cross-section wire diameter of 10 to 50 μm are wired in parallel, so that the conventional FPC and There is no risk of disconnection or leakage compared to the line formed by the screen method, and since the fine metal wire is not embedded in the adhesive layer, the contact with the connected electrode terminal will not be incomplete, Since the round metal wires are arranged so as to make contact with multiple electrode terminals, it suffices to set them so that the longitudinal direction of the connected electrode terminal and the line direction of the wiring member are parallel, and it corresponds to the position of the connected electrode terminal. Unlike conventional ones that required alignment, this alignment error is completely eliminated,
And especially when connecting low-pitch electrodes, it is possible to easily connect fine-pitch circuits to each other with no problem with the electrode pitch or cumulative pitch of the connected electrode terminals. Since the metal round wire is fixed by adhesion, it has the advantages of low connection circuit resistance and high contact reliability, but the connected electrode terminal electrode is additionally provided on this metal round wire with conductive paste. The environmental resistance is improved and the contact stability is improved without using expensive noble metal, and the metal wire between the wires that does not contact the connected electrode terminals is removed by etching. Even if the alignment with the connection electrode terminals is slightly misaligned, there is no risk of leakage, and there is an advantage that no special position management is required for connecting the low-pitch connected electrode terminal group.

(Example) Next, the Example of this invention is given.

Example A thermoadhesive thermoplastic polyester-chloroprene-based adhesive was applied to a 25 μm thick polyester film to a thickness of 15 μm, and then heat-dried at 100 ° C. for 30 minutes to fix the adhesive to the polyester film.

Then, after winding the polyester film coated with this adhesive around a rotating drum that moves in the axial direction and fixing it,
A copper round wire with an outer diameter of 20 μm wound on a bobbin is sent out from between two fixed columns, and while rotating the drum, it is moved at a rate of 0.07 mm / rotation in the axial direction, and the copper wire is placed on the film. Wrap it to make a 0.07mm pitch coil.
After the winding is completed, toluene is sprayed on the coil, the adhesive is partially melted, and the copper wire is temporarily fixed to the film surface. After evaporating the toluene, remove the polyester film with copper wire from the rotating drum. Put this film in a heat press, 16
When the adhesive was cured under the conditions of 0 ° C, 20 kg / cm ² and 20 minutes and the copper wire was embedded in the adhesive layer, a heat-adhesive flexible wiring member with a total thickness of 45 μm and a wiring pitch of 70 μm was obtained. It was

Next, sizing 500 wires to this one with a length of 20 mm, and placing them on a PCB electrode with a terminal pitch of 0.3 mm and electrodes of 0.15 mm so that the longitudinal direction and the wiring direction of the flexible wiring member are parallel. , From above, a silicone rubber with a surface temperature of 200 ° C was pressed at a pressure of 30 kg / cm ² to connect the PCB and the PCB with this wiring member, and the conduction resistance and line insulation resistance were measured.
This is an average of 2.47Ω (minimum 1.09Ω, maximum 3.22Ω),
10 ¹⁰ Ω or more.

[Brief description of drawings]

1 and 2 are vertical cross-sectional views of the heat-bondable flexible wiring member of the present invention, and FIGS. 3 and 4 are vertical cross-sectional views showing a usage example of the same, and FIG. FIG. 6 is a plan view thereof, FIG. 6 is a transverse sectional view thereof, and FIG. 7 is a vertical sectional view of another example of the usage of the same. 1 ... Insulating flexible film, 2 ... Adhesive layer, 3 ... Metal round wire, 4 ... Flexible electrode terminal, 5 ... Anisotropic conductive adhesive, 6 ... Conductive particle, 7: Resist, 9: Connected electrode terminal

Claims (1)

[Claims] 1. A heat-adhesive adhesive layer having a film thickness (T) is provided on a surface of a non-stretchable insulating flexible film, and a plurality of cross-sectional wire diameters (D) is 10 to 10 in the adhesive layer. A round metal wire of 50 μm is partially embedded in the cross section in the adhesive layer, and its arrangement pitch (Pc) and connected electrode terminal width (W) are shown by the formula T ≦ D <Pc <1 / 2W. A heat-adhesive flexible wiring member, characterized in that the heat-adhesive flexible wiring member is arranged so as to have a relationship as described above.