JPH07320543A - Anisotropic conductive bonded structure and its manufacture - Google Patents

Abstract

PURPOSE: To provide an anisotropic conductive adhesive structure which has low connecting resistance, high current capacity, and high high-density connecting reliability, by forming conductive member on a recyclable substrate and coating insulating adhesive on it. CONSTITUTION: In holes of a conductive member forming board 20 which is a glass board 21 which has many separated micro holes 26 and is covered by a mask 23, conductive material such as gold is filled into the holes in electrolytic plating method and is projected from upper surface of the mask 23 like a bump to form a conductive member 2. Next, epoxy based adhesive is coated on the conductive member to form adhesive film layer 1. Finally, by separating the layer from the board 20, an anisotropic conductive adhesive structure in which conductive members 2 with uniform shape and size are distributed homogeneously on its surface. The conductive member forming board 20 can be used many times to form conductive members 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anisotropic conductive adhesive structure and a method for manufacturing the same.

[0002]

2. Description of the Related Art An anisotropic conductive adhesive structure having conductivity in the thickness direction and insulation in the surface direction is a high-density electrical connection,
For example, it is used for connection between an LCD (liquid crystal display) panel and a film carrier or an FPC (flexible circuit board). The structure is generally one in which conductive particles are uniformly dispersed in the adhesive film, and the conductive particles are sandwiched between both electrodes by heating and pressurizing them by sandwiching them between the opposing electrodes that connect them. An electrical connection is made and the surrounding adhesive cures to hold the connection. Since the conductive particles are not in contact with each other, insulation is maintained between adjacent electrodes.

The conductive particles used in this anisotropic conductive adhesive structure are those using metal particles such as nickel and solder (see Japanese Patent Laid-Open No. 60-140791), or nickel,
The most general is one that uses plastic particles such as polystyrene, which is plated with metal such as solder or gold (see Japanese Patent Publication No. 63-31906). These conductive particles are uniformly dispersed in a thermosetting resin such as an epoxy resin, or a resin in which a thermosetting resin and a thermoplastic resin are mixed, and then molded into a film by a casting method or the like to obtain anisotropic conductivity. A bonded structure is obtained.

[0004]

However, in the anisotropic conductive adhesive structure using metal particles, although the connection resistance is low and the current capacity is high, it is difficult to make the particle diameters of the metal particles uniform. Since only particles contribute to the connection, there is a drawback in that the pitch of the electrodes cannot be made too narrow.

On the other hand, in the anisotropic conductive adhesive structure using metal-plated plastic particles, the particle size can be made small and uniform, so that high-density connection is possible, but the metal-plated film makes electrical connection. Therefore, there is a problem that the connection resistance is relatively high and the current capacity is low. Furthermore, in the conventional method for producing an anisotropic conductive adhesive structure, when the conductive particles are dispersed in the resin, the conductive particles tend to aggregate, so that the distribution of the conductive particles in the film becomes uneven. Therefore, there has been a problem that the pitch of the electrodes to be connected cannot be made so narrow.

An object of the present invention is to provide an anisotropic conductive adhesive structure which solves the above-mentioned conventional problems, that is, an anisotropic conductive structure having a low connection resistance, a high current capacity, and a high reliability in high-density connection. Provided is a flexible adhesive structure and a method for manufacturing the same.

[0007]

The anisotropic conductive adhesive structure of the present invention comprises a sheet-like insulating adhesive layer and a large number of conductive members each containing metal as a main component and spaced from each other. The conductive member has a substantially uniform size, and at least a part of the conductive member is exposed from only one surface of the insulating adhesive layer.

The method for manufacturing an anisotropic conductive adhesive structure according to the present invention comprises the steps of forming a large number of conductive members, which are mainly composed of a metal, and are spaced apart from each other on the substrate, and the conductive member is formed on the substrate. The method further comprises the steps of forming an insulating adhesive layer on the substrate and separating the anisotropic conductive adhesive structure including the conductive member and the insulating adhesive layer from the substrate.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view showing a manufacturing process of a substrate for forming a conductive member used in the present invention. FIG. 2 is a cross-sectional view showing a process of manufacturing an anisotropic conductive adhesive structure according to an embodiment of the present invention.

In FIG. 1, a substrate 20 is a heat-resistant glass substrate 21, a conductive layer 22 of platinum or ITO which becomes a conductive path when electrolytically plating a conductive member later, and silicon dioxide or silicon nitride which serves as a mask. The mask material 23 of is sputtered,
It is formed by a known method such as a plasma CVD method (see FIG. 1).
(A)). When the material of the conductive layer 22 is platinum, it is desirable to form an underlayer of titanium or chromium prior to the formation of the conductive layer in order to improve the adhesion to the glass substrate.
Next, a photoresist is applied, and then mask exposure and development are performed to form a resist pattern 24 having holes 25 having an appropriate shape (FIG. 1B). This resist pattern
Holes 26 are formed in the mask material 23 by dry etching using carbon tetrafluoride gas with 24 as a mask (see FIG. 1).
(C)). Finally, the resist pattern 24 is removed to obtain a conductive member forming substrate 20 (hereinafter simply referred to as a substrate) (FIG. 1 (d)). A known wet etching method may be used for etching the mask material 23. For example, conductive layer
When platinum is used for 22 and silicon dioxide is used for the mask material 23, it can be etched with hydrofluoric acid.

Although the conductive member 2 is formed in the mask hole 26 by the method described later, the hole 26 may have a cross-sectional shape of a circle, an ellipse, a rectangle, or any other shape. Further, the arrangement of the mask holes 26 on the surface of the substrate 20 may be regular or irregular. The depth of the mask hole 26 (that is, the thickness of the mask material 23) is preferably 0.3 to 3 μm, and the diameter is 3 to 3.
Although it is 10 μm, it is not particularly limited to this range.

Using the substrate 20 thus manufactured, a conductive member and an anisotropic conductive adhesive structure including the conductive member are manufactured by the process shown in FIG. First, gold is plated by electroplating using the conductive layer 22 as a cathode, the holes of the mask material 23 are filled with gold, and gold plating is continued until the bumps 2a are formed by protruding from the upper surface of the mask material 23. The member 2 is formed. (FIG. 2 (a)). Next, the conductive member 2
A liquid epoxy resin is applied onto the substrate 20 on which is formed by a spin coating method, that is, a method of dropping the liquid epoxy resin onto the rotating substrate 20 to form an adhesive film (insulating adhesive layer) 1 (see FIG. 2 ( b)). Mask material for bump 2a
The protrusion height from the upper surface of 23 and the preferable thickness of the adhesive film 1 are 2 to 20 μm and 10 to 25 μm, respectively, but are not particularly limited to this range. Finally, the substrate 20 is peeled off to obtain the anisotropic conductive adhesive structure 3 including the adhesive film 1 and the conductive member 2. (Fig. 2
(C)). The peeled substrate 20 can be used in the step of forming the next conductive member 2 by returning to the step of FIG. In addition, prior to the formation of the conductive member 2, the mask material 23
By forming a layer of a release material (for example, Teflon) for the adhesive film 1 on the surface of, the separation of the adhesive film 1 and the substrate 20 can be facilitated.

In the method of manufacturing the anisotropic conductive adhesive structure 3 described above, when the conductive member 2 does not project beyond the upper surface of the mask material 23, the contact area between the conductive member 2 and the adhesive film 1 becomes small, If the adhesive force of the adhesive film 1 to the conductive member 2 is sufficiently strong, the conductive member 2 will not remain on the substrate 20 side when the substrate 20 is peeled off.
Therefore, in such a case, the upper end of the conductive member 2 may be flush with the upper surface of the mask material 23 or may be recessed.

As the material of the adhesive film 1, in addition to the above-mentioned epoxy resin, a thermosetting resin such as polyurethane resin,
A thermoplastic resin such as an acrylic resin or a styrene resin, or a mixture of these thermosetting resins and thermoplastic resins can be used.

As the material of the conductive member 2, in addition to gold, for example, metals such as silver, copper, nickel, tin, lead and indium, and alloys thereof can be used. The conductive member 2 does not have to be a uniform material as a whole, and may be made of a combination of different metals or alloys. Further, an organic material or an inorganic material may be added to these metals or alloys.

The above-mentioned conductive member 2 was formed by an electrolytic plating method, but other methods such as an electroless plating method or a film formation using ultrafine particles described in JP-A-59-80361. It may be formed by a method such as a so-called gas deposition method. In the latter method, ultrafine metal particles are mixed with a carrier gas and sprayed onto a substrate from a small-diameter nozzle to form a metal film in a predetermined shape and thickness. According to this method, directly on the glass substrate 21, or other suitable metal, ceramics, a flat substrate such as a polymer,
The conductive layer 22 and the mask material 23 are not necessarily required because a large number of conductive members can be formed apart from each other. When the conductive member is formed without using the mask material, the lower side (substrate side) of the conductive member is flush with the lower surface of the adhesive film 1 in FIG.

The insulating adhesive film 1 is formed by the spin coating method in the above steps, but other methods such as coating by knife coating method may be used. When applying by these methods, it is essential that the adhesive used is liquid, but this adhesive is a liquid at room temperature, and after application, heating or humidity, or ultraviolet rays, visible light, etc. It is of course possible to use low molecular weight or high molecular weight compounds that produce adhesiveness due to light or radiation such as electron beam, or a mixture thereof, as well as a solvent added to this mixture or a resin that is solid at room temperature as a solvent. It is possible to use the one diluted with, or the one which is solid at room temperature and made into a liquid by heating.

Instead of applying the liquid adhesive, the adhesive film may be thermocompression bonded onto the substrate on which the conductive member is formed. However, when a thermosetting resin is included as a material for the adhesive film, it is necessary to perform thermocompression bonding at a relatively low temperature at which the adhesive film sufficiently adheres to the conductive member but does not completely cure.

Further, by applying energy such as ultraviolet rays, radiation such as electron beam, and plasma discharge, direct polymerization from the gas phase is caused on the substrate surface (gas phase polymerization method) to form an adhesive film. Can be used.

The various insulating adhesive film forming methods described above can be carried out by combining a plurality of them. For example, after forming an adhesive film using a liquid adhesive, another adhesive film can be pressure-bonded. That is, among the currently known methods for producing a polymer film, all of the obtained films that can be used for adhesion can be used alone or in combination in the present invention. These methods can be freely selected depending on the properties that the obtained membrane should have.

FIG. 3 shows the electrodes 3 of the external electric circuit parts 31, 31 which are opposed to each other by using the anisotropic conductive adhesive structure 3 described above.
It shows how to connect 2 and 32 to each other. The anisotropic conductive adhesive structure 3 is sandwiched between the upper and lower electrodes 32, 32 to be connected (Fig. 3 (a)), and the conductive member 2 is opposed to the electrode 32 by heating and pressurizing with a predetermined tool from the outside. , 32
It is sandwiched between the two to electrically connect the circuits, and the adhesive film 1 flows by heat and pressure to fill the gap and maintain the connection (FIG. 3B). The conductive member 2 located between the adjacent electrodes 32 and 32 'and not contributing to the connection is insulated by being surrounded by the adhesive 1. The conductive members 2 have substantially the same size and can be regularly distributed in the adhesive film 1. Therefore, every conductive member 2 has an even electrode.
It is possible to take charge of the connection between 32 and 32. Therefore, the electrode
Reliable connection is obtained even when 32 pitches are narrow. Further, since each conductive member 2 has a metal as a main component, it has a low connection resistance and a large current capacity. Further, since each conductive member 2 is exposed from one surface of the adhesive film 1, contact with the electrode 32 of the lower external electric circuit component 31 is obtained before the adhesive film 1 is fluidized. Therefore, the connection with the lower electrode 32 becomes more reliable, and a frictional force acts between each conductive member 2 and the lower electrode 32, so that each conductive member 2 can flow when the adhesive flows. Are flowed together and eliminated between the electrodes 32, 32 facing each other and the adjacent electrode 32 '
The problem of poor connection caused by being located between and does not occur. In addition, each conductive member 2 is not exposed from the upper surface of the adhesive film 1 and is covered with a sufficient amount of the adhesive, and the adhesive flows during connection and the external electric circuit component
You can completely fill the gap between 31 and.

Next, a second embodiment of the present invention will be described with reference to FIG. The same members as those of the first embodiment are designated by the same reference numerals. In the method of manufacturing the anisotropic conductive adhesive structure 3 shown in the first embodiment, the mask material 23 is formed of a hard inorganic dielectric material (such as silicon dioxide or silicon nitride) that can be repeatedly used. Can also be formed of an organic material such as a photoresist.

In FIG. 4, a substrate 20 'comprises a heat-resistant glass substrate 21 and a conductive layer 22, on which a mask material 23' made of photoresist is added. The mask material 23 'is obtained by applying a photoresist on the conductive layer 22, exposing it to a predetermined pattern, and developing it. Using the conductive layer 22 as a cathode, the conductive member 2 is formed by electrolytic plating in the same manner as in the first embodiment (FIG. 4 (a)). Next, the mask member 23 'is removed with acetone or the like (FIG. 4 (b)), and after cleaning, an adhesive film 1'is formed by the same method as in the first embodiment (FIG. 4 (c)). Finally, the substrate 20 'is peeled off to form an anisotropic conductive adhesive structure 3'consisting of the adhesive film 1'and the conductive member 2.
Is obtained (FIG. 4 (d)). The separated substrate 20 'can be used for forming the mask material 23' with photoresist again after cleaning and returning to the step of FIG. 4A to form the conductive member 2. In this manufacturing method, the mask material
23 'needs to be formed each time the anisotropic conductive adhesive structure 3'is manufactured, but the substrate 20' including the heat-resistant glass substrate 21 and the conductive layer 22 can be repeatedly used. In this manufacturing method, the lower end of the conductive member 2 is flush with the lower surface of the adhesive film 1 '.

In this manufacturing method, since the adhesive film 1'is formed after the mask material 23 'is removed, the conductive member 2 is sufficiently contacted with the adhesive film 1'even if the bumps 2a are not necessarily formed. Can have area, substrate 20 '
The conductive member does not remain on the side of the substrate 20 ′ when peeling off. Therefore, the upper surface of the conductive member 2 may or may not project from the upper surface of the mask material 23 '. Further, in the above-mentioned manufacturing method, the substrate 20 ′ is composed of the heat-resistant glass substrate 21 and the conductive layer 22, but a metal foil or thin plate of copper or stainless steel is used as the substrate, and a photoresist is formed thereon. A mask material may be formed.

Further, the cross-sectional shape of the mask hole in this manufacturing method may be circular, elliptical, rectangular, or any other shape, as in the first embodiment. Further, the arrangement of the mask holes on the surface of the substrate 20 'is made regular or irregular so that the number density of the mask holes per unit area is substantially uniform (irregular uniform distribution). By doing so, the distribution of the conductive members within the surface of the adhesive film becomes uniform, and the connection pitch of the electrodes can be reduced.

Next, a third embodiment of the present invention will be described with reference to FIGS. A mask material 23 of a hard inorganic dielectric material (silicon dioxide, silicon nitride or the like) is formed on the copper foil 51 by the same method as in the first embodiment (FIG. 5 (a)). Further, a recess 52 is formed in the copper foil portion at the bottom of the mask hole 26 by etching with ferric chloride or cupric chloride to form the substrate 2
0 ″ is obtained (FIG. 5 (b)). Next, a conductive member 2 ″ is formed by electrolytic plating using the copper foil 51 as a cathode by the same method as in the first embodiment (FIG. 6 (a)). Thereafter, the adhesive film 1 is formed in the same manner as in the first embodiment (FIG. 6 (b)), and finally the substrate 20 ″ is peeled off to form an anisotropic conductive film composed of the adhesive film 1 and the conductive member 2 ″. The adhesive structure 3 ″ is obtained (FIG. 6 (c)). The peeled substrate 20 ″ can be used in the step of returning to the step of FIG. 6A to form the next conductive member 2 ″.

In the manufacturing method described above, a foil or a thin plate made of stainless steel or the like can be used instead of the copper foil 51. Further, a conductive layer such as platinum or ITO formed on the glass substrate may be used as long as it has a sufficient thickness to form the recess 52. Further, as the mask material, it is also possible to use one in which a predetermined pattern is formed after coating or thermocompression bonding of polyimide.

In the anisotropic conductive adhesive structure 3 ″ obtained by this manufacturing method, not only the upper bump 2a of the conductive member 2 ″ but also the lower bump 2b is convex rather than flat.
Therefore, a contaminated film such as an oxide film existing on the surface of the external electrode during connection is more likely to be destroyed, and high connection reliability can be obtained.

Next, a fourth embodiment of the present invention will be described with reference to FIG. Similar to the second embodiment with respect to the first embodiment,
The mask material of the third embodiment may be formed of an organic material such as photoresist. In FIG. 7, a substrate 20 '''is a mask material 23' formed of a copper foil 51 and a photoresist.
Consists of. The mask material 23 'is obtained by applying a photoresist on the copper foil 51, exposing it to a predetermined pattern, and developing it. After that, a recess is formed in the copper foil portion at the bottom of the mask material 23 'by etching in the same manner as in the third embodiment to form the substrate 2
You get 0 '''. A conductive member 2 ″ is formed by electrolytic plating using the copper foil 51 as a cathode (FIG. 7 (a)). Next, mask material
After removing 23 'with acetone or the like (FIG. 7 (b)) and washing, an adhesive film 1'is formed by the same method as in the first embodiment (FIG. 7 (c)). Finally, the copper foil 51 is peeled off to obtain an anisotropic conductive adhesive structure 3 ″ ′ composed of the adhesive film 1 ′ and the conductive member 2 ″ (FIG. 7 (d)). The stripped copper foil 51 can be used for forming the mask material 23 'with photoresist again after cleaning and returning to the step of FIG. 7A to form the conductive member 2''. When the copper foil 51 is reused, a recess is already formed on the surface of the copper foil before applying the photoresist. Therefore, when patterning the photoresist, it is necessary to align and expose the holes of the pattern to the recesses. After that, development is performed to remove the photoresist on the copper foil concave portion to obtain a mask material 23 '. As described above, in the present manufacturing method, the mask material 23 ′ needs to be formed each time the anisotropic conductive adhesive structure is manufactured, but the copper foil 51 can be repeatedly used. Also, instead of the copper foil 51, a foil or thin plate of stainless steel or the like, a conductive layer such as platinum or ITO formed on a glass substrate, or the like can be used, just as in the third embodiment.

In the anisotropic conductive adhesive structure 3 '"obtained by this manufacturing method, the upper bumps 2a and the lower bumps 2b of the conductive member 2" are not flat but convex as in the third embodiment. Therefore, high connection reliability can be obtained.

[0032]

According to the anisotropic conductive adhesive structure of the present invention, an anisotropic conductive adhesive structure having a low connection resistance, a high current capacity, and a high reliability in high density connection can be obtained.
Furthermore, since the conductive member forming the anisotropic conductive adhesive structure of the present invention and the electrode of the external electric circuit component can be reliably connected, there is an advantage that the reliability of the electric connection is high.

Further, according to the method for manufacturing an anisotropic conductive adhesive structure of the present invention, since the number of steps is relatively small and the same substrate can be repeatedly used, low connection resistance,
There is an advantage that an anisotropic conductive adhesive structure having high current capacity and high reliability can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a process of manufacturing a conductive member forming substrate.

FIG. 2 is a cross-sectional view showing a manufacturing process of a first embodiment of the anisotropic conductive adhesive structure of the present invention.

FIG. 3 is a cross-sectional view showing a method of connecting an electric circuit using the anisotropic conductive adhesive structure manufactured according to the present invention.

FIG. 4 is a cross-sectional view showing a manufacturing process of a second embodiment of the anisotropic conductive adhesive structure of the present invention.

FIG. 5 is a cross-sectional view showing a process of manufacturing another conductive member forming substrate.

FIG. 6 is a cross-sectional view showing a manufacturing process of a third embodiment of the anisotropic conductive adhesive structure of the present invention.

FIG. 7 is a cross-sectional view showing a manufacturing process of a fourth embodiment of the anisotropic conductive adhesive structure of the present invention.

[Explanation of symbols]

 1, 1'adhesive film (insulating adhesive layer) 2, 2 '' conductive member 3, 3 ', 3' ', 3' '' anisotropic conductive adhesive structure 20, 20 ', 20' ', 20 '' 'substrate

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location // H05K 3/20 A 7511-4E

Claims (2)

[Claims] 1. A sheet-like insulating adhesive layer, and a plurality of electrically conductive members, which are mainly composed of a metal and are spaced apart from each other, each electrically conductive member having a substantially uniform size and the insulating adhesive layer. An anisotropic conductive adhesive structure, characterized in that at least a part is exposed from only one surface of the agent layer. 2. A step of forming a large number of electrically conductive members which are mainly composed of a metal and are spaced apart from each other on a substrate, a step of forming an insulating adhesive layer on the substrate on which the electrically conductive members are formed, And a step of separating an anisotropic conductive adhesive structure composed of the conductive member and the insulating adhesive layer from a substrate.