KR102254467B1 - Manufacturing method for anisotropic conductive adhesive film - Google Patents

Abstract

Disclosed is a method of manufacturing an anisotropically conductive adhesive film. The method includes: preparing a mold including an adhesive film to which barrier particles having a diameter smaller than the diameter of the conductive particles are attached to the surface; Applying the conductive particles to the surface of the adhesive film to which the barrier particles are not attached; Preparing a film on which a first adhesive layer is formed and attaching the exposed surface of the first adhesive layer to the surface of the mold to which the conductive particles are attached; Peeling the film from the mold to selectively separate only the conductive particles; Applying a second adhesive layer formed of a low-flow resin on the first adhesive layer to which the conductive particles are attached; And applying a third adhesive layer for filling on the second adhesive layer.

Description

Manufacturing method of anisotropic conductive adhesive film {MANUFACTURING METHOD FOR ANISOTROPIC CONDUCTIVE ADHESIVE FILM}

The present invention relates to a circuit connection technology using an anisotropic conductive adhesive, and in more detail, in interconnecting two circuit members opposite to each other, two electrodes facing each other in the thickness direction are electrically conductive while at the same time being adjacent to each other in the plane direction. It relates to an anisotropically conductive adhesive for circuit connection capable of maintaining insulation between the electrodes.

Along with the miniaturization and thickness reduction of electronic devices, circuit members are becoming higher in density and higher precision. Accordingly, in order to connect microcircuits, it has become difficult to cope with conventional welding or soldering methods. In order to solve this problem, an anisotropic conductive adhesive was developed (Japanese Patent Laid-Open No. 51-21192), and anisotropic conductive adhesives contain conductive particles in an adhesive component including a curable resin, It refers to a circuit connecting member capable of electrically conducting two electrodes facing each other in the thickness direction by adjusting, and maintaining insulation between neighboring electrodes in the surface direction at the same time. Such anisotropically conductive adhesives are widely used for the purpose of electrically connecting and bonding various circuit members when manufacturing display devices, semiconductor devices, and the like.

On the other hand, in recent years, as the degree of integration of electronic circuits increases, the pitch between electrodes has been gradually reduced, and accordingly, the size (area) of the circuit electrodes has been gradually reduced. Moreover, in recent years, the development and commercialization of various wearable devices that can be attached to the body and used are further accelerated. Accordingly, even when the pitch between electrodes is applied to a fine electronic circuit and/or a circuit board having flexibility, an anisotropic conductive adhesive capable of maintaining the reliability of electrical connection between circuit members is urgently required.

In particular, the conventional anisotropically conductive adhesive film is manufactured in a form in which conductive particles are randomly dispersed on a resin constituting the adhesive layer. As the area of the electrode to be connected decreases and the distance between adjacent electrodes decreases, the electrode connection area In the presence of a region with a small number of conductive particles or too many conductive particles between the gaps between electrodes, electrical conduction occurs between neighboring electrodes. In order to solve this problem, there is a need to arrange conductive particles at regular intervals in a two-dimensional area.

Accordingly, an object of the present invention is to provide an anisotropically conductive adhesive film having excellent electrical connection reliability between circuit members when it is applied to an electronic circuit having a fine pitch between electrodes.

The objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned will be clearly understood from the following description.

The method of manufacturing an anisotropically conductive adhesive film according to the present invention is interposed between the opposing circuit members to electrically connect the opposing circuit electrodes in the thickness direction while at the same time electrically connecting the adjacent circuit electrodes in the plane direction. A method of manufacturing an insulated anisotropically conductive adhesive film, comprising: a first step of preparing a mold including an adhesive film in which barrier particles having a diameter smaller than the diameter of the conductive particles are attached to a surface; A second step of applying the conductive particles to the surface of the adhesive film to which the barrier particles are not attached; A third step of preparing a film on which a first adhesive layer is formed and attaching the exposed surface of the first adhesive layer to the surface of the mold to which the conductive particles are attached; A fourth step of selectively separating only the conductive particles by peeling the film from the mold; A fifth step of applying a second adhesive layer formed of a low-flow resin on the first adhesive layer to which the conductive particles are attached; It is achieved by including a sixth step of applying a third adhesive layer for filling on the second adhesive layer.

In the first step, an area to which the barrier particles are attached is used as an exposed portion, and an area to which the barrier particles are not attached is used as a non-exposed portion, and the surface of the adhesive film is exposed.

Here, the diameter of the barrier particles is preferably 10% or more to 50% or less of the diameter of the conductive particles.

In addition, the second adhesive layer preferably has a minimum melting viscosity of 500,000 cps or more and 1,200,000 cps or less within the circuit connection temperature range of the anisotropic conductive adhesive film.

In addition, in the first step, it is preferable that the adhesive film has a surface tension lower than that of the barrier particles.

In another aspect, the present invention provides an anisotropically conductive adhesive film manufactured according to the above-described manufacturing method.

In addition, the present invention, the first and third adhesive layers containing a curing agent; A second adhesive layer interposed between the first and third adhesive layers, impregnated with conductive particles therein, and formed of a low-flow resin having a minimum melting viscosity of 500,000 cps or more and 1,200,000 cps or less within a circuit connection temperature range; It is characterized.

By using the method of manufacturing an anisotropically conductive adhesive film according to the present invention, conductive particles can be arranged to a high density level while maintaining a separate state individually, and it is possible to effectively prevent the conductive particles from agglomeration in the local area. Furthermore, it is possible to manufacture an anisotropically conductive adhesive film including conductive particles fixed at a high capture rate, as well as in which conductive particles are regularly arranged at regular intervals. Therefore, when the anisotropically conductive adhesive film manufactured by the manufacturing method according to the present invention is used, even when applied to a flexible circuit board (FPCB) employed in electronic circuits and wearable devices having an ultra-fine pitch, the connection resistance between electrodes is increased. It can be greatly reduced, and at the same time, aggregation between conductive particles does not occur, so that the reliability of electrical connection of circuit members and insulation between neighboring circuit electrodes can be greatly improved.

1 is a process flow diagram schematically showing a method of manufacturing an anisotropically conductive adhesive film according to an embodiment of the present invention for each process.
2 is a cross-sectional view schematically showing a cross-section of an anisotropically conductive adhesive film manufactured by a manufacturing method according to the present invention.
3 is an image photographing an arrangement state of conductive particles transferred to a first adhesive layer, and is a diagram showing a change in the settlement rate of conductive particles according to the relative diameter of the barrier particles with respect to the diameter of the conductive particles.
4 is a graph showing changes in the lowest melting viscosity according to the low-flow resin used as the second adhesive layer.
5 is a graph showing a change in the capture rate of conductive particles according to the lowest melting viscosity of a low-flow resin and a view showing an indentation image together.

In the present invention, various modifications may be made and various embodiments may be provided, and specific embodiments are illustrated in the drawings and will be described in detail through detailed description. However, this is not intended to limit the present invention to a specific embodiment, it should be understood to include all changes, equivalents, and substitutes included in the spirit and scope of the present invention. In addition, in describing the present invention, when it is determined that a detailed description of a related known technology may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted.

The anisotropic conductive adhesive film according to the present invention is interposed between circuit members opposed to each other to electrically connect the circuit electrodes opposite to each other in the thickness direction while at the same time electrically insulating neighboring circuit electrodes in the plane direction. It refers to a conductive adhesive film. Here, the anisotropically conductive adhesive film may include an electrically insulating adhesive layer that can be cured by heat or a light source, and electrically conductive conductive particles dispersed in the adhesive layer.

The inventors of the present invention developed a process of transferring the two-dimensional array of conductive particles onto a film coated with a curable resin using a mold in which conductive particles are attached to a pre-designed two-dimensional plane, thereby producing a product of an anisotropic conductive adhesive film. The characteristics were made to be maximized. In addition, by controlling the physical properties of the resin constituting the adhesive layer, electrical conduction due to aggregation of conductive particles does not occur between adjacent electrodes, and a sufficient number of conductive particles are arranged between opposite electrodes to ensure electrical conduction reliability. I made it possible.

Hereinafter, with reference to FIGS. 1 and 2, an anisotropic conductive adhesive film and a method of manufacturing the same according to the present invention will be described in detail.

[Mold Manufacturing]

A mold is prepared for patterning of conductive particles. Here, the mold is formed of an adhesive film, and for example, a polymer material such as polydimethylsiloxane (PDMS), polyethylene (PE), and polyvinylchloride (PVC) may be used. As for the mold, a film or the like that is easily deformed in the surface shape may be used. The adhesive film constituting the mold has an adhesive force of a value lower than that of the adhesive layer constituting the anisotropic conductive adhesive film to be described below. In addition, the adhesive film can maintain a shape in a solid state (ie, a substrate or film shape) at room temperature without a separate support.

Barrier particles (M) are attached to the remaining areas except for areas where conductive particles are to be attached to the above-described adhesive film. Here, as the barrier particles, inorganic particles such as silicon oxide and zirconium oxide may be used. In addition, it is preferable that the barrier particles are spherical particles having a particle diameter smaller than that of the conductive particles. In particular, it is preferable that the barrier particles have a diameter of 10% or more and 50% or less of the conductive particle diameter. As shown in Fig. 3, when the diameter of the barrier particle is less than 10% of the diameter of the conductive particle, the PDMS resin used as the adhesive film is exposed on the barrier particle, causing the conductive particle to get caught in an unwanted position (approximately At the level of 30%, conductive particles are pinched and agglomerated). In addition, when the diameter of the barrier particles exceeds 50% of the diameter of the conductive particles, the area to which the conductive particles are attached (that is, the area in which the barrier particles are not disposed) is not uniformly formed, and the subsequent conductive particle arrangement process At the same time, the settlement rate at which conductive particles are settled on the adhesive film is sharply decreased (conductive particles cannot be settled at about 20% of the total area).

On the other hand, the barrier particles are selectively attached to a predesigned area on the adhesive film, and at this time, the surface of the adhesive film is disposed in a state pressed to a predetermined depth by the hardness of the barrier particles. That is, the barrier particles are not simply attached by the adhesive force provided by the adhesive film, but are pressed with a constant pressure after the barrier particles are disposed on the surface of the adhesive film. At this time, the surface tension of the adhesive film has a lower surface tension than the surface tension of the barrier particles, and therefore, has a property of broadly adhering the barrier particles due to the low surface tension of the adhesive film. Due to the flexible surface material and low surface tension of the adhesive film, the barrier particles may be in close contact and disposed on the adhesive film in a predetermined area.

On the other hand, by exposing the upper surface of the mold while the barrier particles are disposed on the adhesive film, the adhesion of the barrier particles to the adhesive film is increased. That is, light is irradiated on the upper surface of the mold using a mask in which the area where the barrier particles are not disposed (that is, the area to which the conductive particles are attached) is used as the non-exposed portion, and the area where the barrier particles are disposed is the exposed portion. At this time, the adhesive force of the exposed portion irradiated with light is greater than that of the non-exposed portion not irradiated with light. Accordingly, the barrier particles located in the exposed portion may maintain a state attached to the adhesive film with a stronger bonding force than the conductive particles disposed in the exposed area located in the non-exposed portion. For example, in the case of PDMS, when exposed to ultraviolet rays, the methyl portion of the chemical structure is damaged, through which reactive functional groups are formed in the polymer constituting the adhesive film. These functional groups form chemical covalent bonds through dehydration condensation bonds that can have adhesion to barrier particles such as hydrogen bonds compared to methyl groups.

[Arrangement of conductive particles]

Conductive particles are coated on the mold on which the barrier particles prepared above are arranged. The applied conductive particles are positioned in regions where the barrier particles are not disposed. At this time, the conductive particles adhere to the adhesive film with weaker adhesion than the barrier particles having increased adhesion through exposure or the like.

[Conductor's Warrior]

First, the film on which the first adhesive layer (R) of the anisotropic conductive adhesive film is formed is attached onto a mold in which conductive particles are disposed. At this time, it is preferable that the adhesive force of the first adhesive layer is smaller than the adhesive force of the area where the barrier particles are disposed (exposed portion) and greater than that of the area where the conductive particles are disposed (non-exposed portion). When the first adhesive layer of these physical properties is attached to the mold on which the conductive particles are disposed and then peeled again, only the conductive particles are selectively attached to the first adhesive layer and separated. In addition, since the diameter of the barrier particles is smaller than the diameter of the conductive particles, when attaching the first adhesive layer on the mold, the area in which the first adhesive layer contacts the conductive particles is compared to the area in which the first adhesive layer contacts the barrier particles. It becomes bigger. Accordingly, only the conductive particles disposed in the mold can be selectively attached to the first adhesive layer and separated due to the limitation of the adhesive strength of the first adhesive layer and the difference in diameters of the barrier particles and the conductive particles.

[Formation of low flow layer]

On the first adhesive layer prepared above, conductive particles are two-dimensionally arranged at a certain position. At this time, some of the conductive particles may be impregnated on the first adhesive layer, but most of the conductive particles are exposed. A second adhesive layer is formed on the first adhesive layer to which the conductive particles are exposed, using a resin having low flow characteristics. Here, the low-flow layer improves the capture rate of conductive particles when the anisotropically conductive adhesive film containing conductive particles is applied to an actual product. That is, the fluidity of the adhesive layer is increased due to high heat of the surrounding environment, so that the position of the conductive particles is moved at a predetermined position to prevent aggregation or separation of the conductive particles from the positions between the opposite electrodes. To this end, the low-flow resin to be used as the second adhesive layer has a minimum melting viscosity of at least within the circuit connection temperature range (generally, a temperature range of room temperature to 150°C) for connecting a circuit member using an anisotropic conductive adhesive film. It is preferably 500,000 cps or more and 1,200,000 cps or less.

[Formation of upper adhesive layer]

A third adhesive layer is formed on the film including the first and second adhesive layers prepared above. Here, the third adhesive layer serves to sufficiently fill the space between adjacent electrodes provided in the circuit members when the circuit members are connected by using the anisotropic conductive adhesive film together with the first adhesive layer.

The anisotropically conductive adhesive film thus prepared has a three-layer structure of a first adhesive layer, a second adhesive layer, and a third adhesive layer. Here, the first adhesive layer and the third adhesive layer use a resin having the above-described physical properties, but each resin composition includes a polymerizable material having a functional group polymerizable by radicals and a curing agent that generates free radicals by heat or light. . In addition, it is preferable that the second adhesive layer does not contain a curing agent as a low flow layer. However, when the anisotropic conductive adhesive film is applied to an actual product, the adhesive film is interposed between the opposing circuit members and then compressed. At this time, the first and third adhesive layers closely fill the voids between the electrodes between the circuit members. While being cured, the second adhesive layer is partially cured while being in contact with the curing agent present in the first or third adhesive layer during compression.

On the other hand, the second adhesive layer is interposed between the first and third adhesive layers, and conductive particles are impregnated therein, and in particular, the minimum melting viscosity within the circuit connection temperature range (approximately room temperature to 150°C) is 500,000 cps or more. It is preferably formed of a low-fluidity resin of 1,200,000 cps or less.

The low-fluidity resin used as the second adhesive layer has a melt viscosity that changes depending on the temperature in the circuit connection temperature range (see Fig. 4).At this time, the lowest melting viscosity is when the melt viscosity is the lowest within the circuit connection temperature range. Refers to the viscosity of The minimum melting viscosity varies depending on the type, composition, and manufacturing method of the resin used, and the inventors of the present invention use the anisotropically conductive adhesive film finally manufactured according to the minimum melting viscosity of the low-fluidity resin when connecting circuit members. It has been found that the capture ratio at which conductive particles are captured between electrodes facing each other varies.

In order to confirm the change in the capture rate according to the lowest melting viscosity of the second adhesive layer, an anisotropically conductive adhesive film was prepared using a low-flow resin having a different lowest melting viscosity as shown in Table 1 below. The first to third adhesive layers used in Examples 1 to 3 were all made of a phenoxy-based epoxy resin and a cycloaliphatic epoxy resin, wherein the second adhesive layer was made of resin. When forming the film, the minimum melting viscosity was adjusted by changing the process conditions (temperature and time).

division Minimum melting viscosity (cps) Capture rate (%) Comparative Example 1 100,000 30 Example 1 500,000 85 Example 2 800,000 90 Example 3 1,200,000 95

4 and 5, when the minimum melting viscosity of the low-flow resin used as the second adhesive layer within the circuit connection temperature range is less than 500,000 cps, the capture rate of conductive particles required for the anisotropically conductive adhesive film is not satisfied. . That is, in the case of Comparative Example 1 (lowest melting viscosity of 100,000 cps), the capture rate is 30% or less, and as can be seen in the indentation image (A) of FIG. 5, the conductive particles are second due to the low viscosity of the low-flow resin used. It can be seen that a large amount is lost in the trapped position in the adhesive layer. On the contrary, when the lowest melting viscosity of the low-fluidity resin used as another example exceeds 1,200,000 cps, as shown in the indentation image (E) of FIG. 5, the indentation level was almost "0", and through this, the challenge It can be seen that the particles are hardly deformed when the circuit is connected or no contact is made between the opposite electrodes. However, as in Examples 1 to 3, when the lowest melting viscosity of the low-fluidity resin is in the range of 500,000 cps or more and 1,200,000 cps or less, the indentation image of FIG. 5 [(B): Indentation image of Example 1 / (C) : Indentation image of Example 2 / (D): As can be seen from the indentation image of Example 3), it exhibits a capture rate of 85% or more and good indentation properties.

According to the above-described method of manufacturing an anisotropically conductive adhesive film, since each conductive particle is transferred to the first adhesive layer in a state in which each conductive particle is individually disposed through a mold in which the barrier particles are disposed, the conductive particles of fine diameter are transferred to the two-dimensional plane. It is easy to place regularly on the bed. In addition, the adhesive film constituting the mold in which the barrier particles are disposed provides only an adhesive force capable of reversibly attaching the conductive particles, and can be used repeatedly several times.

According to this method, the conductive particles can be arranged to a high density level while maintaining the individually separated state. In addition, it is possible to effectively prevent the conductive particles from being aggregated in the localized region. Further, it is possible to manufacture an anisotropically conductive adhesive film including conductive particles fixed at a high capture rate, as well as in which conductive particles are regularly arranged at regular intervals. Therefore, the use of the anisotropically conductive adhesive film manufactured by the manufacturing method according to the present invention can improve the reliability of the electronic device characteristics of the electronic device.

Although a preferred embodiment of the present invention has been described so far, those of ordinary skill in the art to which the present invention pertains may be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the embodiments of the present invention described herein should be considered from a descriptive point of view rather than a limiting point of view, and the scope of the present invention is indicated in the claims rather than the above description, and all differences within the scope equivalent thereto are the present invention. Should be interpreted as being included in.

Claims (7)

In the method of manufacturing an anisotropically conductive adhesive film interposed between opposing circuit members to electrically connect between opposing circuit electrodes in a thickness direction and at the same time electrically insulate adjacent circuit electrodes in a plane direction,
A first step of preparing a mold including an adhesive film in which barrier particles having a diameter smaller than the diameter of the conductive particles are attached to the surface;
A second step of applying the conductive particles to the surface of the adhesive film to which the barrier particles are not attached,
A third step of preparing a film on which the first adhesive layer is formed and attaching the exposed surface of the first adhesive layer to the surface of the mold to which the conductive particles are attached,
A fourth step of selectively separating only the conductive particles by peeling the film from the mold,
A fifth step of applying a second adhesive layer formed of a low-flow resin on the first adhesive layer to which the conductive particles are attached,
Including a sixth step of applying a third adhesive layer for filling on the second adhesive layer,
The first and third adhesive layers contain a curing agent,
The second adhesive layer is interposed between the first and third adhesive layers, conductive particles are impregnated therein, and formed of a low-flow resin having a minimum melting viscosity of 500,000 cps or more and 1,200,000 cps or less within a circuit connection temperature range. Characterized in, the method for producing an anisotropically conductive adhesive film.
The method of claim 1,
In the first step, manufacturing an anisotropically conductive adhesive film, characterized in that the area to which the barrier particles are attached is used as an exposed part, and the area to which the barrier particles are not attached is used as a non-exposed part, and the surface of the adhesive film is exposed. Way.
The method of claim 1,
The diameter of the barrier particle is characterized in that 10% or more and 50% or less of the diameter of the conductive particle, the method for producing an anisotropic conductive adhesive film.
delete The method of claim 1,
The adhesive film is characterized in that it has a surface tension lower than the surface tension of the barrier particles, the method of manufacturing an anisotropically conductive adhesive film.
An anisotropically conductive adhesive film manufactured according to the method of manufacturing an anisotropically conductive adhesive film according to any one of claims 1, 2, 3 and 5. delete

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