JPS61200606A - Anisotropic conducting film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (,) Industrial Application Fields The present invention is applicable to flexible circuits, etc. This is an anisotropically conductive film in which a conductive material is dispersed to maintain conductivity only in the thickness direction, and which has the ability to remain connected. It's about film.

The so-called anisotropic conductive film, which has the ability to be conductive in the thickness direction and insulating in the plane direction, is useful for connecting the terminals of flexible circuits and for connecting flexible circuits. When connecting two electrode groups, the method described above is to connect each electrode simultaneously and independently.
It has been proposed to hold an anisotropically conductive 7-ilm between electrode groups in a pressurized manner.

In this way, the anisotropically conductive film that connects the two 'ui groups has electrical insulation as its base material.

It is known that the spherical film itself is made of a hot/rut type adhesive material1, or that a heat-sensitive adhesive is added to the film in advance to impart adhesive properties. It is being

(e) Problems to be Solved by the Invention In the former anisotropic conductive film, the conductive material is unevenly distributed in the film, so the electrical resistance varies in the thickness direction of the film. The problem was that it was big.

In addition, in the latter 4-way conductive 7-ilm, if the blending ratio of the adhesive is too high, gaps similar to those described above will occur, and conversely, if it is too small, the adhesive strength will be low. There were problems such as birds falling off or separating.

The problem of peeling in the above films is thought to be due to the manufacturing method.

In other words, when the base material itself is made of a photomel F-type adhesive material, etc., the adhesiveness is extremely high, so the conductive material does not stick to each other or is unevenly dispersed, resulting in the thickness being reduced. This is because the electrical resistance in the horizontal direction varies greatly.

On the other hand, contact′? In an anisotropic conductive film containing I-shaving, as the adhesive composition ratio increases, the resistance in the thickness direction varies due to the same reason as above. There was a problem with XI characteristics.

(d) Between 7fl, 57. As a method for solving the above problems, it is conceivable to provide adhesive l\1/1 on one or both sides of the anisotropically conductive film.

However, as will be described later, when using the anisotropically conductive film for the above-mentioned purposes, it is necessary to satisfy two conditions that are contradictory to each other.

(1) Firmly fix the electrode group 1illi above so that it does not separate.

■Providing electrical continuity between two opposing electrode groups.

That is, in order to firmly fix both electrode groups, it is better that the adhesive layer is thicker, and on the other hand, in order to provide electrical conductivity to both the electrode groups, it is preferable that the contact 1gl1 layer is thinner.

・In order to satisfy these two contradictory requirements, the inventor conducted extensive research on the degree of I'7 that the adhesive layer should have, and as a result, he decided to We succeeded in determining the optimal thickness range of the layers.

That is, the present invention provides an anisotropically conductive film in which a large number of conductive materials are fractionated into an electrically insulating film, and both ends or both ends of the conductive materials are exposed from the surface of the film, at least on one side of the film. It is characterized by forming an adhesive layer with a thickness of 1 to 50 μm.

In the present invention, the insulating film refers to a film formed of electrically insulating rubber or synthetic U1 resin. Gen rubber, styrene butanoene rubber, silicone type υ, fat percentage urethane type resin, etc.

In addition, the above-mentioned synthetic υ (fats include thermoplastic 1 (fat) and 1 thermosetting υ (fat), such as polyolefins,
PVC, polyester flfJm, 7 grill t
H1m, polyamide, polycarbonate) 01 pilgrimage, poly 7 cetal resin, polystyrene υ (fat, A B S U
(+m, polytetrafluoroethylene (hereinafter referred to as PTFE)
In the present invention, the above-mentioned insulating Among plastic films, especially PTFE
The film has the best electrical properties and productivity.

The most significant feature of the present invention is that when an adhesive layer is provided on both sides or one side of an anisotropic conductive film, the thickness of the adhesive/1 is 1 to 50 μm, preferably 3 to 10 μm.
The point is that

If the thickness of the adhesive layer is more than 50 μm, there will be a problem of poor conductivity with the electrode group, while if it is less than 1 μm thick, the electrode group cannot be firmly fixed, resulting in problems such as the electrode group falling off or separating. occurs.

According to the experimental results of the present inventors, the appropriate thickness of the adhesive stopper layer is 3 to 10 μm, and very good results were obtained in both adhesive strength and conductivity within this range.

The adhesive layer used in the present invention may be a pressure-sensitive adhesive or a heat-sensitive adhesive: X! Commonly used adhesives such as scraps and thermosetting epoxy adhesives can be used, but adhesives that are easily plastically deformed, such as HotF-melt adhesives, have improved productivity, adhesive strength, and anisotropic conductivity. This is preferable from the viewpoint of ease of handling of the plastic film and electrical properties.

For example, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, aveophmer fat, etc. are useful as the above-mentioned hot-F melt adhesive.

When an insulating film made of fluorine-based polyolefin such as PTFE is used, it is easy to form an adhesive layer with high peel strength by sputter etching when forming an abrasion layer on the surface. It is uruno.

In addition, the method of forming an adhesive layer on both sides or one side of the anisotropic conductive film includes a method of dipping it in a solution of the above adhesive and pulling it up, or a method of spraying adhesive Rokuyo, or using a method such as Rollco F, etc. , various methods can be adopted.

The anisotropically conductive film of the present invention can be used, for example, in the following 1
The product is manufactured to 5XL through the steps shown below.

(a) Plastically mixing the insulating material and the conductive material, or, if necessary, processing aids (meaning things that give fluidity to the insulating material to make it easier for the conductive material to disperse) or A solvent is added and mixed using a stirrer to uniformly disperse and orient the conductive material in the insulating material.

(b) If unnecessary processing aids are floating in the composition obtained in this way, after filtering the processed ribs, conventionally known rolling The film is manufactured by the most suitable method from among the methods such as the method, the Karengoo method, the in-7reshi method, the T-gui method, and the melting method.

Further, when a 77-wire resin such as PTFE is used as the insulating material, firing can be performed after tEt if desired. Firing temperature is usually 360°C to 380°C'''C
be. At this time, if the conductive material is easily oxidized, it is preferable to bake it in an inert atmosphere such as nitrogen gas.

(Convex) The anisotropically conductive film obtained in this manner; if desired, the surface may be eluted with a growth solvent, or removed by sputter etching, ion blasting, etc. to form a conductive material. Exposing both ends or both ends.

Next, in manufacturing the anisotropically conductive film of the present invention,
PTFE, which is excellent in both productivity and electrical properties of the film, is used as an insulating material, and powdered material is monodispersed as a conductive material in the film (thickness direction 1; one conductive material is present). In this case, an example of the transfer process will be explained in more detail.

(a) First, a PTFE fine bag or fibrillated PTF'E and a powdered conductive material are mixed in the presence of a processing aid (kerosene, white oil, etc.). 5! By fighting Shigeru, they are united.

The above-mentioned fibrillated PTFE refers to PT "E" which has been pre-stirred with a stirrer to advance fibrillation, and when this fibrillated PTFE is stirred, the dispersibility of the above-mentioned powdery conductive material is further improved.

Then, stir the PTI'E and powdered conductive material! By stirring the mixture with a screw, the fibrillation of the P T l"E proceeds and the dispersion of the conductive material is promoted. Mixers such as an autohomogen mixer, a mixigroll, and an internal mixer are used for stirring. A homodisper, which is a stirring blade bent 90 degrees vertically around the disk, is sufficient.

It is appropriate that the amount of processing aid during stirring is the minimum amount that can soak the entire mixture; if it is too large,
Powdered conductive material is easy to separate, similar to the preliminary disposal case 1 mentioned above.
The stirring time for consolidating is 2 times, 2 times.
2 to 3 minutes after 000 to 300 Orpm is sufficient.

In the second case, since the conductive material is in powder form, it has better dispersibility compared to using a fibrous conductive material, and can be evenly dispersed in a state close to the ideal close packing. It will become.

In addition, it is desirable to increase the amount of the conductive material added to PTFE in order to increase the density of the connector, but if it is too much, the anisotropic conductive film will become unstable. Since it is difficult to guarantee tensile strength, 100-2500 parts by weight per 1001 parts of r'TFE is usually appropriate.

(b) If a mixture of powdered conductive material and PTFE is obtained as in step 2, processing aids are removed by filtration and roll pressure weir is performed using a uniform roll.In this case, it is possible to make a living! In order to maintain the temperature of the roll, it is appropriate to set the roll temperature to 20°C to 80'C. In order to efficiently promote fibrillation in one roll roll, it is necessary to gradually reduce the thickness to a predetermined thickness by rolling several F or more stages. When PTFIE is fibrillated by roll-rolling (on top of this), fibers grow like root hairs between the four electrical materials mentioned above, eliminating contact between the electrically conductive materials, compared to other insulating materials. The blending ratio of the conductive material can be increased, and the film is subjected to tensile force, but the tensile strength increases due to fibrillation. Therefore, the thickness of the film can be rolled very easily until it becomes equal to the size of the conductive material.

In addition, in order to further improve the dispersion of the powdered conductive material, it is necessary to pile up the rolled materials to a specified thickness and re-roll them to the specified thickness several times until the film has no color unevenness. It is desirable to have two or more times.

During this rolling, it is possible to replenish the conductive material separated during the stirring and rolling.

The above predetermined thickness refers to the thickness of the conductive material in the rolled film.
- Refers to the particle size that can be dispersed, and is usually larger than the maximum diameter of the conductive material, but smaller than 1.8 times the maximum diameter.

(c) Obtain a rolled film of a predetermined thickness in this way:
After heating and drying, the film is finally rolled at rt to remove the processing auxiliary layer by extraction by solvent proofing. Both ends are exposed from both sides of the film, and each conductive material is passed through the film in a single shape.

The thickness of this final rolling is set according to the powder diameter distribution of the conductive powder used, and is usually within the range of the maximum powder diameter to the average powder diameter, but it may be less than the average powder diameter in some cases. Monkey.

(d) Next, PTFH is fired if desired.

The firing temperature is usually 360°C to 380°C. When the conductive material is easily oxidized, especially when %zinc is used,
It is preferable to perform the firing in an inert gas such as a nitrogen bath.

Note that when the anisotropic conductive film is fired while attached to a substrate such as a 1Al connector body, or when used unfired, step (d) above can be omitted.

As in step (c) above, when the final rolling (penetrating the film of the conductive powder) is performed after the processing aid is removed, pinholes and the like that remain after the removal of the processing aid are formed by rolling. On the other hand, if the occurrence of bottle holes is slight or there is no good luck, the final thickness (predetermined thickness) in step (B) is the final rolling thickness above, and in step (c) above, the processing aid is You can only remove it.

(e) To connect the two electrode groups for eyebrow 8I via a hexagonal conductive film, the film is interposed between both electrode groups, and then heated and pressurized to fix them together. However, during this pressurization, the contact layer covering the conductive material in the anisotropic 4'4 film is exposed to the periphery.
However, if the thickness of the adhesive layer exceeds 50 μm, the abrasions cannot be reliably removed and the conductive material cannot be exposed. The adhesion/peel strength of both electrode groups is approximately proportional to the thickness of the adhesive layer, and the thickness of the adhesive layer must be 1μ or more in order to securely bond these electrode groups without separating them. Out.

(f) Example (a) Example of drying out of the anisotropic conductive film of the present invention y of the present invention
An example of the structure of the four-way conductive film will be explained below with reference to the drawings.

3 to 5, the anisotropic conductive film (
1) comprises a non-permanent film (2), a conductive material (3) penetrating the insulating film (2) in its thickness direction, and a conductive material (3) formed on the surface of the insulating film (2). It is composed of an adhesive layer (4).

The shape of the conductive material (3) is not particularly limited, and may be, for example, spherical as shown in FIG. 1 or oval as shown in FIG. figure~
As shown in FIG. 5, the exposed portions from both sides of the anisotropic conductive film (1) may be formed into a flat shape.

In addition, the adhesive N (4) needs to have a thickness in the range of 1 to 50 μ-, and outside this range it lacks practical properties, and the adhesive N (4) is As shown in Figures 1 to 4, it may be provided on both sides of the insulating film (2), or alternatively, as shown in Figure 5, it may be provided on one side of the film (2). It may be provided. Note that, if desired, the surface of the film may be subjected to electrical or chemical adhesion treatment.

(B) Examples 1 to 6 and Comparative Example i) 10 parts by weight of kerosene as a processing aid was added to 10 parts by weight of kerosene as a processing aid to 10 parts by weight of TE'H fine balago [Daikin Industries, Ltd., trade name F-101]. Fibrillated PTFE was produced by forced stirring for 2 minutes at a rotational speed of 2000 to 3000 rpm using an Odohomo mixer 1 manufactured by Kakogyo Co., Ltd., with a stirring amount of a disper blade [18 beads], and a copper powder [Fukuda Metal Whistle] was produced. After adding 75 weight i parts of Powder Industry (trade name: Cu-Q average particle diameter 45μ layer) and adding 2 weight parts of kerosene,
Stirring was performed for 3 minutes under the same conditions as above. After leaving it for about 1 hour,
Excess kerosene was removed, the mixture was kneaded for about 20 minutes using a mixing roll heated to 60°C, and the mixture was passed several times through a rolling roll heated to 60°C to form an anisotropically conductive film with a thickness of 35 to 40 μm. Each film was immersed in 1 hour of kerosene to extract the kerosene, and then left in nitrogen gas at 370° C. for about 20 minutes to be fired.

The obtained anisotropic conductive film was heated to 60 watts of energy.
After Svanta etching treatment with "see/cIll", the anisotropic conductive film was immersed in a solution prepared by dissolving the hot-melt adhesive shown in the table in 8 xylene and pulled up. An adhesive layer having a thickness of 7I was formed as shown in Figure 3. The thickness of the AI abrasion layer was controlled by the concentration of the adhesive or the number of dippings.

This anisotropically conductive film with an adhesive layer was cut into 15 mm squares, that is, 15 square rings, which were sandwiched between 10 mm square, 35 μm thick rolled copper foils and heated to 130°C using a hot press. Each sample was prepared by heat-pressing with a machine at a pressure of 5 kB/Cm for 5 minutes, and then cooling.

Note 1) Measurement of resistance in the thickness direction The sample shown in each example was sandwiched between 1m square, 35μ thick foils, and a load of 100g was applied to it. The resistance of each sample was measured using a denotal meter.

Note 2) Measuring the resistance in the plane direction.
An absolute gap of 5Idm was set up, and the sample shown in Example 3 was placed on top of the second one, and the electrodes were brought into contact between the two electrodes, and a load of 1kg was applied to the electrodes. Measure the resistance with a denotal meter.

Note 3) Adhesive strength is 200° when beading the sample body foil at 90 degrees.
The values are shown when peeled at a speed of mm/in.

(g) Effects of the Invention The anisotropically conductive film of the present invention has an adhesive layer of 1 to 50 µm on at least one side thereof, so that it can be connected without separating the two electrode groups that are in phase with each other. Each ′ of the electrode group
It is possible to easily and reliably connect the IL poles in a state where they are left alone.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of an anisotropically conductive film with layers formed on both sides, and Figure 2 is a cross-sectional view of an anisotropically conductive film with layers formed on both sides. Figure FA3 is a cross-sectional view showing that both ends of the conductive material are flat in Figure 1, and Figure 4 is a cross-sectional view showing that both ends of the conductive material are anisotropically conductive in Figure 3. A sectional view showing that the film is exposed from both sides, and FIG. 5 is a top view of the ``Aj7 conductive film with an adhesive layer formed on one side. 2)... Ja green film (3)... Conductive material (4)... Adhesive layer Patent applicant: Nitto Electric Industry Co., Ltd. 7) 7) Cable and printed wiring board and Figure 1 2 ... 9 Nine hairs seven!Fil Otsu, Figure 3, 〆 4 N Figure 4, Figure S, /

Claims (1)

[Claims] (1) In an anisotropic conductive film in which a large number of conductive materials are dispersed in an electrically insulating film, and both ends or both end portions of each conductive material are exposed from both sides of the film, at least one side of the film has a thickness. An anisotropically conductive film comprising an adhesive layer having a thickness of 1 to 50 μm.