JPS63261612A - Anisotropic conducting sheet - 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 (a) Industrial Application Field The present invention is an anisotropic conductive sheet used in a laminated connector for precision electronic circuits, particularly for use in precision electronic circuits with an interelectrode pitch of 0.4 + * + s or less. This anisotropic conductive sheet is used as a connector for joining 7-fin pitch electrodes, and controls the flow of insulating resin during the joining process to prevent short circuits between adjacent electrodes and improve connection characteristics. It is related to.

(b) Conventional technology Conventionally, as an anisotropic conductive sheet for precision electronic equipment circuits,
The following are known:

The first anisotropically conductive sheet is a wall-shaped sheet formed by penetrating an electrical insulator and arranging a large number of conductive rubber contacts.

The second anisotropically conductive sheath has a structure in which a conductive member such as a metal wire or carbon fiber is embedded in the thickness direction of an electrically insulating sheet (electrical insulator) (Japanese Patent Laid-Open No. 59-9332
-3 Publication, JP-A-57-141880).

The third anisotropically conductive sheet is obtained by mixing an appropriate amount of conductive material with an electrical insulator, extruding the mixture into a sheet shape using a rock or roll, and producing an electrically conductive sheet. It has a structure in which conductive members are dispersed in an insulating sheet.

(c) Problems to be Solved by the Invention However, the first anisotropic conductive sheet described above has low productivity and is therefore expensive, and since the contact portion is linear, it is not suitable for precision electronic equipment circuits. It is necessary to install the terminals so that they are parallel to the conductive member, and if they are not installed parallel to the conductive member, the insulation between the terminals cannot be maintained, resulting in short circuits and failures. The connection workability with the anisotropic conductive sheet was poor (sometimes problems occurred with product reliability).

In addition, since the conductive members in the second anisotropic conductive sheet are formed in a linear shape, if the amount of the conductive members is increased, the conductive members may come into contact with each other and the insulating properties in the plane direction may be impaired. On the other hand, if the amount of the conductive material is reduced, variations in contact resistance and electrical resistance in the thickness direction may occur, or the problem of mistouching may occur, causing electrical problems between terminals for precision electronic equipment circuits and the anisotropic conductive sheet. In some cases, communication was lost.

Furthermore, in the third anisotropically conductive sheet, the conductive member may be buried in the electrically insulating sheet, and the contact resistance may vary depending on the uneven shape of the circuit terminal connected to the anisotropically conductive sheet, pressurizing conditions, etc. As a result, the reliability as a connector was poor as a result of variations in the conductivity and sometimes problems of poor conduction.

The biggest disadvantage of the first to third anisotropic conductive sheets mentioned above becomes noticeable when they are used for bonding so-called fine-pitch electrical circuit boards with an electrode pitch of 0.4 mm or less.

Specifically, when the electrical insulator (sheet) is made of heat-press adhesive resin, even if the manufacturing process of the anisotropically conductive sheet has a predetermined structure, that is, the electrically conductive members are electrically insulating. Even though the sheet is completely independent and has conductivity in the thickness direction and insulation in the plane direction, the flow of the electrical insulator (sheet) is reduced by heating and pressurizing it during actual use. phenomenon occurs, as a result of which the conductive member becomes an electrical insulator (
This moves with the flow of the sheet), inhibits the independent form of the conductive members at the end, and makes it easy for the conductive members to aggregate, resulting in electrical connection between adjacent electrodes to be joined, resulting in so-called leakage.・Furthermore, if the conductive member moves, the conductive member necessary for the final electrical connection should be in contact with the electrode to be joined, but this contact cannot be achieved. The mistouch phenomenon, which is the biggest problem for connectors, was occurring.

(d) Means for Solving the Problems The present inventors have discovered that the fine pitch structure of the anisotropically conductive sheet is not inhibited even when heated and pressurized, and
For many years, we have been conducting intensive studies on anisotropically conductive sheets that do not cause mistouch or leak phenomena on the electrodes to be bonded, and also provide good connection characteristics over a long period of time.

As a result, the electrically insulating resin layer that surrounds the conductive member in the anisotropic conductive sheet is formed of two types of electrically insulating resin layers with different compositions, and one of them suppresses the fluidity of the other resin while also providing initial adhesion. It was discovered that by using a resin with high strength and a resin whose adhesive strength increases over time, it has good connection characteristics for a long time after heat and pressure bonding, and this led to the completion of the present invention. It is.

That is, the present invention is an electrically insulating sheet having a lattice shape in plan view,
It is an anisotropically conductive sheet in which a conductive member is passed through the lattice in the thickness direction of the sheet, and the space between the conductive members is surrounded by two types of electrically insulating resin layers having different compositions. This is a characteristic feature.

The present invention will be explained in detail below.

The anisotropically conductive sheet to which the present invention is applied is particularly limited as long as it is formed by an electrically insulating sheet having a lattice shape in plan view and a conductive member passing through the lattice in the thickness direction of the sheet. isn't it.

The conductive members used in the present invention are not particularly limited, but include zinc, tin, iron, nickel,
m, lead, indium, ml, 1% metal powder, alloy powders and fibers containing these as main components, lead-tin alloy, bismuth-
Examples include powders and fibers of tin-lead-innotum alloy, bismuth-tin-lead-cadmium alloy, tin-lead-indium alloy, bismuth-tin alloy, carbon powder and a-fiber, etc.
Among these, those having excellent machinability are preferred.

Further, as the conductive member, a mixture of a conductive material and a binder may be used.

As the conductive material, the above-mentioned metal powder or metal fiber, or
Carbon powder or a-fiber can be used, while thermoplastic resin or thermosetting resin can be used as the binder.

Further, examples of materials for forming the electrically insulating sheet used in the present invention include electrically green synthetic resins and rubber.

The above-mentioned synthetic resins include thermoplastic resins, reactive thermoplastic resins, and thermosetting 8 (fats);
Examples include hot melt arboreal.

As the hot melt resin, for example, so-called hot melt adhesive resins such as polyolefin, polyamide, polyester, and ionomer 1fJIllt resins are useful.

In addition, the reactive thermoplastic resin used in the present invention includes:
A above? Examples include those in which a urethane compound having an incyanate group is added to a resin, and epoxy/nylon based resins.

A feature of the present invention is that in the anisotropic conductive sheet, each conductive member is surrounded by two types of electrically insulating resin layers having different compositions.

By configuring it in this way, electrically insulating resin layers with different compositions can have one electrically insulating property! ! The fat layer (resin) controls the flowability of the other resin when heated and pressurized,
This makes it possible to maintain the anisotropic structure during the bonding process by heating and pressurizing during actual use and during the production of the anisotropically conductive sheet.

In a preferred embodiment of the present invention, one of the two electrically insulating resin layers (PIS 1 layer) has a gel fraction in the range of 10 to 60% by weight. It is something.

In the present invention, the gel fraction was measured by the following method.

That is, in 200 ml of toluene at a temperature of 80 to 90 °C
3 g of resin was immersed for 90 minutes, and then the remaining undissolved gel was taken out. After sufficient toluene had been evaporated, the weight of the gel was measured and calculated as a ratio to the initial weight.

The gel fraction of one electrically insulating resin layer (ttS1 layer) is 1
If it is less than 0% by weight, the resin tends to flow, and as a result, the conductive members move, causing unevenness and irregular spacing of the conductive members, leading to mistouching and leakage phenomena, and reducing reliability in practical use. This is not preferable because it may cause a decrease in the temperature.

Furthermore, if the gel fraction exceeds 60% by weight, the adhesive properties of the electrically insulating resin layer will be impaired.

Therefore, in particular, the heating and pressing conditions (uniformity) during actual use
Taking this into consideration, 20 to 40 percent heavy view is preferable.

Any commonly used method can be used to control the gel fraction, and both chemical crosslinking and electron beam crosslinking are useful, but with chemical crosslinking, the residual crosslinking agent added for crosslinking is In some cases, variations in quality may occur due to the influence on the material or changes over time, etc., so electron beam crosslinking is the most useful.

In the case of electron beam crosslinking, the irradiation dose is 1 to 20
Mrad is effective in obtaining the above gel fraction.

In the present invention, in two types of electrically insulating resin layers having different compositions, one electrically insulating resin layer (first layer) has a higher gel fraction than the other electrically insulating resin layer (second layer). It may be adjusted so that it becomes high.

Further, in the present invention, in two types of electrically insulating resin layers having different compositions, the other electrically insulating resin layer (tj4
It is preferable that the second layer I) is formed of a reactive thermoplastic resin because the connection characteristics with the electrode to be joined are stable over a long period of time.

The above-mentioned reactive thermoplastic resins include those to which a urethane compound having an incyanate group is added, epoxy/nylon resins, and ethylene-vinyl acetate copolymers and polyethylenes that are grafted with silane using a silane coupling agent. Examples include those in which a base polymer is mixed with a tackifier resin, wax, etc.

(e) Function In the present invention, the electrical insulator surrounding the conductive member in the anisotropic conductive sheet is composed of two types of electrically insulating resin layers having different compositions, and one electrically insulating resin layer (m1 layer). The fluidity of the other electrically insulating resin layer (second layer) is suppressed and a material with high initial adhesive strength is used, and the other electrically insulating resin layer (second layer) is made of a material whose adhesive strength increases over time. By using the anisotropically conductive sheet, it is possible to prevent the electrically insulating resin layer from flowing when manufacturing the anisotropically conductive sheet or when adhering it to the electrode to be joined by applying heat and pressure. Even after bonding to the electrode to be bonded, the conductive member has the effect of maintaining the anisotropic structure of the present invention in which the conductive member independently penetrates the electrically insulating sheet.

(f) Examples Hereinafter, the present invention will be explained in detail based on Examples, but the present invention is not limited thereto.

Examples 1 to 4 Examples of the structure of the anisotropically conductive sheet of the present invention are shown in Fig. 1 and fjS.
To explain with reference to Figure 2, (1) is an anisotropically conductive sheet, and the anisotropically conductive sheet (1) is an electrically insulating sheet (2) that has a lattice shape in plan view, and conductive members (3) are arranged between the lattices. ) is passed through the sheet in the thickness direction, and the conductive members (3) and (3) are surrounded by two types of electrically insulating resin layers (4) and (5) having different compositions. It will be done.

The anisotropic conductive sheet (1) is manufactured, for example, by the method described below.

As one electrically insulating resin layer (first layer) (4), 3 M rad (Example 51j) was applied in advance to a film of hot melt modified polyethylene having a thickness of 25 μm.

Absorbed doses of 5 Mrad (Example 2), s 10 Mrad (%Example 3), and 20 Mrad (Example 4) were applied by electron beam irradiation, and the other electrically insulating resin layer (second layer )(5) is a film of a reactive hotnold adhesive (reactive thermoplastic resin) containing glycidyl methacrylate and an organic peroxide in a composition consisting of an ethylene-vinyl acetate copolymer and a tackifier. (
One of the electrically insulating resin layers (12 μm thickness theory) was used.
On both sides of ffi 175) (4), the other electrically insulating resin layer (TLS2 layer) (5) and (5) are superposed, respectively, to obtain a composite film, and the composite film and 100 parts by weight of polyurethane resin are A conductive film (thickness: 30μ) made by dispersing 230 parts by weight of nickel powder into a rectangle of the desired size, and after laminating these alternately,
By applying heat and pressure, they are integrated to form a lump.

By cutting the above lump in the stacking direction, a thickness of 30
A zebra-like film of μ-rings is obtained.

The above zebra-like film and the above composite film are cut into rectangles of desired size, laminated alternately, and then integrated by heating and pressurizing to obtain a rectangular block, which has a thickness of 50 μm in the stacking direction. By cutting into rings, anisotropic conductive sheets (Examples 1 to 4) having a lattice shape in plan view were obtained.

Comparative Example 1 Same as the above example except that a film of hot melt modified polyethylene with a thickness of 50 μm, which had been given an absorbed dose of 5 Mrad by electron beam irradiation, was used instead of the composite film of the above example. An anisotropic conductive sheet having a lattice shape in plan view was obtained.

Comparative Example 2 In the above example, a 90,000 conductive film with a lattice shape in plan view was prepared in the same manner as in the example except that a film (thickness: 25 μm) of hot-melt modified polyethylene that had not been irradiated with electron beams was used. ) was obtained.

Comparative Example 3 In the above example, a flat surface was prepared in the same manner as in the example except that a hot melt modified polyethylene film (thickness 25 μm) was irradiated with an electron beam at an absorbed dose of 25 Mrad. An anisotropically conductive sheet with a visual lattice shape was obtained.

The anisotropic conductive sheet having a lattice shape in plan view obtained in each of the Examples and Comparative Examples described above was cut into pieces with a width of 5 mm and a length of 20 ss. Pull print base I! (FPC) electrodes are arranged so as to face each other,
They were integrated by heating and pressurizing them at a temperature of 180° C., a pressure of Gkg/am', and a pressurizing time of 30 seconds.

Table 1 shows the properties of each of the above examples and comparative examples.

(Left below) Attention 111 After storage for 500 hours under conditions of temperature 70℃ and relative humidity 95%! & Wear force (g/10 am).

Note 2) JIIIt resistance Connection resistance (Ω/-Ω) after storage for 500 hours under conditions of temperature 70°C and relative humidity 95%.

From Table 1, it can be seen that for each 'X example product, no movement of the guide member was observed when connecting the printed circuit board, and the adhesive strength after storage was better than the initial adhesive strength. It can be seen that the connection resistance remains stable even after this.

On the other hand, in Comparative Examples 1 to 3, the variation in connection resistance increases due to storage, and in Comparative Example 1, the adhesive strength decreases due to storage, and in Comparative M2, the connection with the 7-sided cable printed circuit board decreases. Movement of the conductive member is observed.

Furthermore, the initial adhesive strength of Comparative Example 3 was extremely low, and Nf
When the problem i occurs, it is recognized that the initial resistance varies widely.

(1) Effects of the Invention The present invention has the above-mentioned structure, and the electrically insulating layer for forming the conductive member in the anisotropic conductive sheet is composed of two types of electrically insulating resin layers having different compositions, one of which As the electrically insulating resin NM, use one that can push the fluidity of the other electrically insulating resin layer and have a large initial adhesive strength, and use a material that increases the adhesive strength over time for the other electrically insulating resin layer. This prevents the flow of the electrically insulating resin layer (treeffff) when the electrically conductive sheet is attached to the electrode to be bonded by heating and pressurizing, and in particular, this anisotropically conductive Even after the electrically insulating sheet and the electrode to be bonded are bonded, the conductive member passes through the electrically insulating sheet in an independent state, making it possible to integrate electrical bonding and adhesion, and to prevent a decrease in adhesive strength. This has the effect of maintaining stable welding characteristics over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the anisotropic conductive sheet of the present invention, and FIG. 2 is a perspective view of the anisotropic conductive sheet of the present invention. 1... Anisotropic conductive sheet, 2... Electrical insulation sheet F
. 3... Conductive member, 4... One electrically insulating resin layer,
5...The other electrically insulating resin layer.

Claims (5)

[Claims] (1) An anisotropically conductive sheet consisting of an electrically insulating sheet having a lattice shape in plan view, with a conductive member passing through the sheet in the thickness direction between the lattices, where the conductive members have two different compositions. An anisotropically conductive sheet characterized by being surrounded by an electrically insulating resin layer. (2) In two types of electrically insulating resin layers, one of them (the first layer) is made of a resin that suppresses the fluidity of the resin of the other (the second layer) and has a large initial adhesive strength, and the other (the second layer) The anisotropic conductive sheet according to claim 1, in which the layer) is made of a resin whose adhesive strength increases over time. (3) Anisotropic conductivity according to claim 1 or 2, wherein one of the two electrically insulating resin layers (the first layer) has a gel fraction of 10 to 60% by weight. sheet. (4) The anisotropically conductive sheet according to claim 3, wherein one of the two electrically insulating resin layers (the first layer) has a gel fraction of 20 to 40% by weight. (5) The anisotropic conductivity according to any one of claims 1 to 4, wherein the other (second layer) of the two types of electrically insulating resin layers is formed of a reactive thermoplastic resin. sex sheet.