JP2743957B2 - Method for manufacturing anisotropic conductive sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an anisotropic conductive sheet used for electrical connection between various circuit boards or between an electronic component and a circuit board, and more particularly to a pitch of a surface mount IC (hereinafter referred to as IC). The present invention relates to a method for manufacturing an anisotropic conductive sheet suitable for connecting an outer lead electrode (hereinafter referred to as a lead electrode) having a small area to a pattern electrode on a circuit board of an inspection device.

[0002]

2. Description of the Related Art Advances in semiconductors and semiconductor-related technologies have led to the development of high-performance IC chips, which have become possible to mount IC chips at high density on circuit boards.
It greatly contributes to high integration, light weight, and compactness of various electronic devices such as word processors, personal computers, and memory cards. Although these ICs are properly designed and manufactured in a controlled process, they sometimes fail, so highly integrated ICs that require high reliability are 100% tested. Is common. Since resin packages for such ICs are diversified, IC sockets, anisotropic conductive sheets, and the like have been conventionally used for inspection and mounting.

[0003]

Generally, an IC socket is
Au-plated phosphor bronze, beryllium copper, and other copper on a socket body made by injection molding an engineering plastic made of glass fiber added to polybutylene terephthalate (PBT), polysulfone (PSF), polyethersulfone (PES), etc. A large number of contacts made of an alloy spring material are press-fitted and fixed, and the lead electrodes of the IC mounted on the IC socket and the pattern electrodes of the circuit board are electrically connected via these contacts. Thus, the contact is provided with a bent portion that generates elasticity in order to maintain a predetermined contact pressure when connected to the lead electrode of the IC.

[0004] Such IC sockets are widely used because they have high connection stability and high reliability in heat resistance tests such as IC burn-in tests, but have the following problems. That is, with the increase in the integration of ICs, the number of lead electrodes has been reduced and the pitch has been reduced. At present, the lead electrodes have been advanced to a pitch of about 0.3 mm. When an IC socket is used to inspect an IC having such a lead electrode, the lead electrode is likely to be deformed or damaged due to insufficient strength against applied contact pressure.

In particular, when setting an IC in an IC socket, since the IC is dropped by using tapered guides at the four corners, a slight displacement causes bending in the floating direction (vertical direction), resulting in unstable connection and reliability. Decrease. Further, the socket body is manufactured by injection molding of engineering plastic as described above. However, in the case of an IC having a low pitch lead electrode as described above, the partition plate (separator) of the socket body becomes very thin. For,
The molding dies become more precise and complex, resulting in very expensive and increased costs. Due to the problems described above, the conventional IC socket cannot currently handle an IC having a low-pitch lead electrode.

Recently, ICs for processing high-frequency signals have been frequently used in mobile phones, communication devices, computers, and the like. However, when such ICs are inspected using a conventional IC socket, the contacts are bent. Because of the presence of the portion, the conduction path is long, the inductance is increased, and an operation failure often occurs.

Next, the anisotropic conductive sheet has a structure in which a large number of fine metal wires are buried in a sheet-like electrically insulating elastomer layer in a direction parallel to the thickness direction of the sheet. It is sandwiched between pattern electrodes such as a substrate and electrically connected to each other to perform IC inspection and the like, and has been used as a device capable of improving the problem of the IC socket.

In order to obtain an anisotropic conductive sheet having the above-mentioned structure, one method is as follows. (A) After arranging and fixing fine metal wires at a constant pitch on one surface of a sheet-like electrically insulating elastomer layer, A large number of composite sheets are laminated and integrated such that the thin metal wires are parallel and the electrically insulating elastomer layer and the thin metal wires alternately overlap, and the laminate is cut into a sheet at right angles to the thin metal wires. As another method, (b) one is a thin metal wire and the other is polyethylene terephthalate (PET)
A cross-woven fabric prepared by weaving an electrically insulative thin wire (hereinafter referred to as an insulative thin wire) made of a monofilament or the like into a mesh shape is laminated to a sheet-like electrically insulative elastomer layer to form a composite. A method is adopted in which a large number of thin wires are stacked and integrated so that the electrically insulating elastomer layer and the thin metal wires alternately overlap, and the laminate is cut into a sheet at right angles to the direction of the thin metal wires.

However, in the method (a), it is troublesome to regularly arrange the thin metal wires on the sheet-like electrically insulating elastomer layer, and it is extremely difficult to arrange them at a low pitch. . The method (b) has the advantage that the arrangement of the fine metal wires is easier and the lower pitch arrangement is possible as compared with the method (a). However, since the resulting anisotropic conductive sheet contains the insulating thin wires, the sheet is used. The contact pressure when connecting the lead electrode of the IC and the pattern electrode of the circuit board is increased, and cannot be used for an IC having a low pitch lead electrode. Since the cut portion of the insulating thin wire remains, there is a problem that contact with the lead electrode of the IC or the pattern electrode of the circuit board becomes unstable and the reliability of the connection is reduced.

[0010]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks of the prior art, and simply and stably connects a lead electrode having a small pitch and area of a surface mount IC to a pattern electrode of a circuit board. It is an object of the present invention to provide a method for producing an anisotropic conductive sheet having a low compressive load and capable of inspecting an IC by using the same and not deforming a lead electrode of the IC at the time of connection.

The present invention achieves this object, and comprises the following first to fifth steps.
In particular, a gist of the present invention is a method of manufacturing an anisotropic conductive sheet for connecting an outer lead electrode of a surface-mounted IC and a pattern electrode of a circuit board with facing each other. First Step: A mesh-shaped cross-woven fabric is formed from a conductive thin wire (preferably warp) and a water-soluble electrically insulating fine wire (preferably weft). 2nd process The said interwoven fabric is bonded and fixed to the electrically insulating elastomer layer formed on the base material to form a first composite sheet. Third step The water-soluble electrically insulating fine wires in the first composite sheet are dissolved and removed with water or hot water to form a second composite sheet. Fourth step: The base material is removed from a large number of the second composite sheets, and the conductive directions of the conductive thin wires are aligned and preferably parallel to each other. Integrate to form a laminate. Fifth Step The laminate is cut into a sheet in a predetermined plane, preferably at a right angle, in the conductive direction of the conductive thin wire to form a sheet. After the first to fifth steps, it is optional to add a step of performing metal plating on the portions of the conductive thin wires protruding from both cut surfaces of the sheet after the sixth step.

Next, each step of the method for producing an anisotropic conductive sheet of the present invention will be described with reference to the drawings. First Step As shown in FIGS. 1 (a) and 1 (b), a conductive thin wire 1 used as a warp in a warper and an insulating thin wire 2 used as a weft in a warper are woven into a mesh. The mixed fabric 3 is obtained. A general-purpose weaving machine can be used for weaving, but if a weaving machine that manufactures a mesh for screen printing is used, the conductive fine wire 1 can be made fine to about 300 mesh. As the conductive thin wire 1, a metal wire, a conductive synthetic resin wire, a carbon fiber, a wire made of a conductive elastomer, or a metal-plated wire of these or a glass fiber can be used. A bronze wire, beryllium copper wire, or the like, which has high strength and is advantageous in cost, is desirable. The wire diameter is not particularly limited, but is preferably 10 to 50 μm in order to reduce the gauze thickness of the interwoven cloth 3 and to obtain a stable contact with the lead electrode and the like and to minimize the compressive load when connecting. . This material is used after its surface is treated with an adhesive, if necessary. A synthetic resin wire such as water-soluble polyvinyl alcohol is used as the thin insulating wire 2, and a monofilament or multifilament of water-soluble vinylon having a strength suitable for weaving is preferable.

Second step Next, as shown in FIG. 1 (c), the electrically insulating elastomer is converted into a base material 4 by using a calendering machine, a T-die extruder or, when the material is in a liquid state, various coating machines.
After processing into a thin film to form an electrically insulating elastomer layer 5 thereon, by laminating with the interwoven fabric 3,
A first composite sheet 6 is obtained. As the electrically insulating elastomer, natural rubber, synthetic rubber, thermoplastic elastomer, and the like can be used, and silicone rubber, which has high heat resistance and is easily formed into a sheet, is most preferable. It is optional to add an adhesive component therein to improve the adhesion to the conductive thin wire 1. When silicone rubber is used as the electrically insulating elastomer, the first composite sheet 6
Is a substrate 4 such as a PET sheet by a calendering machine.
The silicone rubber layer is formed into a sheet by topping, and the obtained fabric is easily laminated by laminating the mixed fabric 3 with the silicone rubber layer.

Third Step Next, the water-soluble insulating fine wire 2 in the first composite sheet 6 is treated with water or hot water or steam (a small amount of a highly polar solvent such as methanol or ethanol added as necessary). (It is acceptable to use a surfactant in an amount that does not degrade the electrical characteristics.)
The second composite sheet 7 shown in (d) is easily obtained.

Fourth Step Next, the second composite sheet 7 is cut into a predetermined size, and after the base material 4 is peeled off, as shown in FIG. 1 (e), the conductive direction of the conductive thin wire 1 is changed. A large number of the laminates 8 are laminated, preferably in parallel, and laminated in such a manner that the electrically insulating elastomer layer 5 and the conductive thin wire 1 are alternately formed.
Get. The direction of the conductive thin wire 1 is constantly changed in a wavy manner due to the warp, and the conductive direction is the direction of the average dashed line shown in the figure.

Fifth Step Subsequently, the laminate 8 is cut into a sheet in a predetermined plane, preferably a vertical plane, in the conductive direction of the conductive fine wire 1, and the conductive fine wire 1 is cut into the electrically insulating elastomer layer 5. An anisotropic conductive sheet 9 of the present invention (see FIG. 1 (f)) in which only the buried conductive sheet is buried is obtained.

Sixth step Further, if necessary, in order to improve the connection reliability and stabilize the connection resistance value, a portion of the conductive thin wire 1 protruding on both cut surfaces of the obtained sheet is made of gold or the like. By performing the metal plating treatment described above, an anisotropic conductive sheet having a more stable connection resistance value can be obtained.

The anisotropic conductive sheet 9 thus obtained is shown in FIG.
As shown in (f), both electrodes are connected to be sandwiched between the lead electrode 11 of the IC 10 and the pattern electrode 13 on the circuit board 12.

[0019]

According to the manufacturing method of the present invention, the cross-woven fabric woven by the conductive thin wires and the insulating thin wires is bonded onto the sheet-like electrically insulating elastomer layer, so that the step of arranging the conductive thin wires is performed. An anisotropic conductive sheet that is simplified, can be easily arranged at high density, and can be connected to an IC having lead electrodes with a small pitch and area is obtained.

Since the insulating thin wires are not contained in the anisotropic conductive sheet, the compressive load applied to the lead electrodes when connecting the lead electrodes of the IC is reduced, and the bending and bending of the lead electrodes having a small pitch and area are reduced. It is possible to connect and inspect the IC without causing damage. Further, since the conduction path of the anisotropic conductive sheet is shorter than that of an IC socket, it can be used for inspection of an IC for processing a high-frequency signal.

[0021]

【Example】

First step: Plain weave with a screen mesh weaving machine using a phosphor bronze wire having a diameter of 40 μm for the warp and a 30 denier water-soluble vinylon fiber monofilament / ML type (trade name, manufactured by Nichibi Co., Ltd.) for the weft. Bronze is 2
A 50-mesh, 100-mesh water-soluble vinylon fiber mixed fabric was obtained.

Second step Next, a P having a thickness of 50 μm
On a glossy surface of the ET sheet, 100 parts by weight of a silicone rubber compound having a hardness of 68 ° H, KE-702BU (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.), and a peroxide-based vulcanizing agent, C-3 ( Shin-Etsu Chemical Co., Ltd., product name) 3
A silicone rubber composition obtained by adding parts by weight and kneading was kneaded to a thickness of 100 μm using a calendering machine. Subsequently, the above-mentioned woven fabric was overlapped and laminated on this silicone rubber composition to produce a first composite sheet.

Third step The water-soluble vinylon fibers on the interwoven fabric surface of the first composite sheet are dissolved and removed using hot water at 80 ° C., and then dried to remove the water, thereby obtaining a second composite sheet. Was.

Fourth Step Next, the second composite sheet is cut to 100 mm in length and width, and then the PET substrate is peeled off, and the silicone rubber composition layer, which is parallel to the conductive direction of the phosphor bronze wire, and which is 500 sheets were laminated so that bronze wires were alternately overlapped. Next, this laminated block is
Heat and pressure molding at 0 ° C, 1.0 kgf / cm ² for 5 hours,
A laminate having a height of about 50 mm was produced.

Fifth Step The laminate thus manufactured is cut into a sheet perpendicular to the direction of conduction of the phosphor bronze wire by a slicer using a rotary blade, and the pitch of the phosphor bronze wire is 100 μm vertically and horizontally, and the thickness is 100 μm. A sheet having a thickness of 0.5 mm was obtained.

Sixth step Then, this sheet is
After a heat treatment at 2 ° C. for 2 hours, the portions of the phosphor bronze wire protruding on both cut surfaces were subjected to metal salt, reducing agent, complexing agent, buffering agent,
Nickel was plated to a thickness of 1 μm and gold to a thickness of 0.3 μm sequentially by an electroless plating method using a plating solution containing a stabilizer to obtain a final anisotropic conductive sheet.

[0027]

[Comparative Example] A conventional anisotropic material in which a 30 μm diameter PET monofilament was used for the weft yarn and the same process as in the example was performed except for the step of dissolving and removing the weft yarn, and the weft yarn was left in the electrically insulating elastomer layer. A conductive sheet was produced.

The two kinds of anisotropic conductive sheets obtained in this manner are each composed of a gold-plated PC plate and a tip area of 0.2 m.
the amount of compression and relation of compressive loads when compressed between the lead electrodes gilded pins shape m ² shown in FIG. FIG. 3 shows the relationship between the compressive load and the connection resistance value according to the four-terminal method. It was confirmed that the anisotropic conductive sheet of the example can be connected with a low compressive load as compared with the comparative example. Also,
FIG. 4 shows the distribution of the connection resistance values. It was confirmed that the connection resistance values of the anisotropic conductive sheet of the example were lower than those of the comparative example, and the dispersion was small.

[0029]

As described above, according to the present invention, the step of arranging the conductive thin wires on the electrically insulating elastomer layer is simplified, and the conductive thin wires can be arranged at a high density. I with small pitch and area lead electrodes
An anisotropic conductive sheet capable of connecting C to the circuit board is obtained.

Further, since the anisotropic conductive sheet obtained finally does not contain the insulating thin wires, the anisotropic conductive sheet itself becomes soft, and when the lead electrode of the IC is connected to the pattern electrode, the lead electrode is connected to the lead electrode. The applied compressive load is reduced, and even in the case of an IC having a small lead electrode pitch and area, the IC can be inspected by connecting the lead electrodes without bending or damage. Furthermore, since the cut portions of the insulating thin wires do not protrude on both cut surfaces of the anisotropic conductive sheet as in the comparative example, the contact between the lead electrodes of the IC and the pattern electrodes of the circuit board becomes stable, and the reliability of the connection is improved. The performance is improved.

In addition, the obtained anisotropic conductive sheet is used
When the inspection is performed by connecting the lead electrode of the circuit board and the pattern electrode of the circuit board, the conduction path of the anisotropic conductive sheet is shorter than that of the IC socket, so that it can be used for the inspection of the IC for processing the high frequency signal. .

[Brief description of the drawings]

FIG. 1 shows a process for producing an anisotropic conductive sheet of the present invention, wherein (a) is a plan view of a cross-woven fabric obtained in a first step,
(B) is a sectional view taken along line XX of (a), (c) is a second view.
Sectional view of the first composite sheet obtained by the step, (d)
Is a cross-sectional view of the second composite sheet obtained in the third step,
(E) is a cross-sectional view of the laminate obtained in the fourth step,
(F) is an explanatory view of how to use the anisotropic conductive sheet obtained by the method of the present invention.

FIG. 2 is a graph showing the relationship between the amount of compression and the compressive load of an anisotropic conductive sheet obtained in Examples and Comparative Examples.

FIG. 3 is a graph showing a relationship between a compressive load and a connection resistance value of an anisotropic conductive sheet obtained in Examples and Comparative Examples.

FIG. 4 is a graph showing a distribution state of connection resistance values of anisotropic conductive sheets obtained in Examples and Comparative Examples.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Conductive thin wire 2 ... Insulating thin wire 3 ... Interwoven fabric 4 ... Base material 5 ... Electrical insulating elastomer layer 6 ... 1st composite sheet 7 ... 2nd composite sheet 8 ... Laminate 9 ... Anisotropic conductive sheet 10 ... IC 11 ... Lead electrode 12 ... Circuit board 13 ... Pattern electrode

Continuation of front page (56) References JP-A-4-17282 (JP, A) JP-A-1-140577 (JP, A) JP-A-61-179014 (JP, A) JP-A-56-156608 (JP) , A)

Claims (1)

(57) [Claims] 1. A method for producing an anisotropic conductive sheet, comprising the following first to fifth steps. First step: A mesh-shaped interwoven fabric is formed from the conductive thin wires and the water-soluble electrically insulating thin wires. 2nd process The said interwoven fabric is bonded and fixed to the electrically insulating elastomer layer formed on the base material to form a first composite sheet. Third step The water-soluble electrically insulating fine wires in the first composite sheet are dissolved and removed with water or hot water to form a second composite sheet. Fourth step: The base material is removed from a large number of the second composite sheets, the conductive directions of the conductive thin wires are aligned, and the electrically insulating elastomer layer and the conductive thin wires are stacked and integrated so that they alternately overlap to form a laminate. I do. Fifth Step The laminate is cut into a predetermined plane in the conductive direction of the conductive thin wire to form a sheet.