JPH04292803A - Anisotropic conductive film - Google Patents

Abstract

PURPOSE:To heighten the electric connection between electrodes so as to further narrow the electrode pitch by using an anisotropic conductive film in which individual bodies each having an insulating coating and containing conductive particles are dispersed and mixed. CONSTITUTION:In a connecting material to be used between electrodes 4 arranged opposite to each other to make the electric connection, individual bodies each having as an outer wall an insulative film 7 different from the resin component 8 which is a main body of the connecting material are dispersed and mixed in the resin 8 while the individual bodies contain conductive particles 5.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anisotropic conductive film with improved reliability of electrical insulation between terminals.

0002

[Prior Art] Conventionally, anisotropic conductive films have been produced by uniformly dispersing conductive particles in a resin, localizing conductive particles in a resin according to the connection pitch, or embedding conductive fibers in silicone rubber. has been applied. In order to prevent short circuits between adjacent electrodes, it is necessary to manage the maximum length of a conductive particle or an individual made of a plurality of conductive particles to be smaller than the inter-electrode spacing. In addition, as described in Japanese Patent Application Laid-open No. 1-52303, by using a ferromagnetic material on fibers as a conductive material and arranging it in the film thickness direction in a magnetic field, shorts can occur between electrodes even at a fine pitch. I try not to wake up.

0003

[Problems to be Solved by the Invention] In recent years, with the practical use of liquid crystal displays, anisotropically conductive adhesives or films have come to be widely used for connection between electrodes. Since high-density electrodes can be connected economically, it will become increasingly important in the field of mounting personal computers, televisions, etc. With the development of such electronic devices, the number of connection terminals will increase in the future, and the pitch of connection electrodes will tend to become smaller. The minimum connection pitch of conventionally commonly used anisotropic conductive films is approximately 2
It was about 00 μm. However, as the electrode pitch becomes smaller, the spacing between adjacent electrodes becomes smaller, increasing the possibility that conductive particles in adjacent electrodes will come into contact with each other and cause a short circuit, limiting the distance between adjacent electrodes, and The reliability of the electrical insulation between them has become a problem. In conventional anisotropic conductive films, it is necessary to manage the dispersion of conductive particles and a plurality of conductive particles. For this reason, advanced technology is required for dispersion control, and there is a natural limit to the distance between adjacent electrodes due to the size of the conductive particles and the individual particles made up of a plurality of conductive particles. In order to localize conductive particles by using a magnetic field to arrange a conductive substance as shown in Japanese Patent Laid-Open No. 1-52303, a new device for forming a magnetic field is required. In the connection step, it is preferable that the electrical insulation between adjacent electrodes be ensured only by conventional pressurization or heating. Further, as shown in Japanese Patent Application Laid-Open No. 1-33808, controlling the distribution of conductive particle diameters within an extremely narrow range requires advanced technology in the production and selection of conductive particles. Even when the conductive particle size distribution is wide, it is preferable that electrical continuity between the connecting electrodes can be ensured. The object of the present invention is related to the connection between electrical connection terminals,
An object of the present invention is to provide an anisotropically conductive film that can ensure electrical continuity between connecting electrodes and electrical insulation between adjacent electrodes.

0004

[Means for Solving the Problems] In order to achieve the above object, the present invention ensures electrical insulation between adjacent electrodes by ensuring electrical insulation between solid conductive particles, and Conductivity must be ensured between the connecting electrodes. The present invention is characterized in that an insulating film that is removed during a connection process such as pressurization is formed on a solid body made of a plurality of conductive particles used for an anisotropic conductive film. The insulating film may be in the form of a capsule containing the individual, or may be in a state in which the individual is coated with an insulating resin. Due to this insulating film, even if individuals come into contact with each other,
Electrical insulation is ensured. In addition, the insulating film covering the individual can be formed through a mechanical connection process such as pressurization.
The conductive particles that form the solid body between the connecting electrodes move and move, breaking the insulating film covering the solid body made of conductive particles and exposing the surface of the conductive particles, causing the solid body between the connecting electrodes to move. Electrical continuity is ensured. In addition, by heating, energizing, etc., the solid insulating film is softened and plastically flows to expose the surface of the conductive particles in contact with the electrode surface, thereby ensuring electrical continuity between the connection terminals.

[0005]

[Operation] By using an insulating film formed on the solid conductive particles used in the anisotropic conductive film, which is removed during the connection process such as applying pressure, electrical insulation can be achieved even if the solids simply come into contact with each other. By ensuring this property, it is possible to reduce the distance between adjacent electrodes, and the insulating film covering the individual can be used to connect the individual between the connected electrodes through a mechanical connection process such as applying pressure. The movement of the formed conductive particles destroys the insulating film covering the individual conductive particles, exposing the surface of the conductive particles, ensuring electrical continuity between the connected electrodes. . In addition, by heating, energizing, etc., the solid insulating film is softened and plastically flows to expose the surface of the conductive particles in contact with the electrode surface, thereby ensuring electrical continuity between the connection terminals.

[0006]

[Examples] The present invention will be explained below with reference to Examples.

<Example 1> FIG. 1 is a sectional view showing an example using the anisotropically conductive film of the present invention. The semiconductor element 1 is fixed to an insulating base substrate 3 via an anisotropic conductive film 2. The electrode 4 of the semiconductor element 1 is an individual 6 made up of a plurality of conductive particles 5 within the anisotropic conductive film 2.
Electrical continuity with the electrode 11 of the insulating base substrate 3 is ensured via the insulating base substrate 3. The conductive particles 5 are made of nickel metal material. The conductive particles 5 may be made of copper, other than nickel material.
Any material that conducts electricity, such as aluminum or silver, may be used. In this example, conductive particles with an average particle size of 5 μm were used. The spacing between adjacent electrodes is 30 μm. An individual 6 made of a plurality of conductive particles 5 is an insulating film 7 made of a thermoplastic epoxy resin.
is coated. The resin 8, which is the main component of the anisotropically conductive film, is made of thermosetting polyimide resin. In addition to thermoplastic epoxy resin, the resin forming the insulating film 7 may also be selected from the resin 8 that is the main component of the anisotropically conductive film, such as silicone, polystyrene, polypropylene, polyvinyl chloride, polyethylene, polyamide, polyurethane, and polyester. Any resin with a low softening temperature may be used.

FIG. 2 shows the connection process. As shown in FIG. 2A, before the anisotropic conductive film undergoes a connection process by heating and pressurizing, the periphery of the individual 6 is completely covered with an insulating film 7. Therefore, electrical conduction does not occur even if the individuals come into contact with each other. The individual 6 consists of a plurality of conductive particles. The individuals 6 are dispersed narrower than the spacing between adjacent electrodes. The size of the individual 6 may be longer or shorter than the distance between the electrode 4 of the semiconductor element 1 and the electrode 8 of the electrically insulating substrate 3 after connection. An anisotropic conductive film is placed between the semiconductor element 1 and the insulating base substrate 3, and heated and pressed. The anisotropic conductive film used in the present invention may be in the form of a sheet or paste as long as it can cover the electrode surface. FIG. 2(b) shows a cross-sectional view of the connected state after heating and pressurizing. Possible heating methods include thermal conduction heating through a jig during pressurization, infrared heating, high frequency heating, ultrasonic heating, and laser heating. By pressurizing and heating at 160° C. for 30 seconds, the solids 6 existing between the electrodes 4 of the semiconductor element 1 and the electrodes 11 of the insulating base substrate move and come into contact with each other, and the insulating film 7 covering the solids 6 is removed. was softened and plastically flowed, and was removed from between the contacting conductive particles and between the electrode and the conductive particles, and electrical continuity could be obtained. The thickness of the anisotropic conductive film is determined so as not to apply excessive pressure to the solids existing between adjacent electrodes. As a result, the solids existing between adjacent electrodes remain in the same shape as before the connection process even after the heating and pressurizing connection. Since the individual was covered with an insulating film, electrical insulation between adjacent electrodes was maintained even if they were in contact with each other.

<Embodiment 2> FIG. 3 is a sectional view showing a second embodiment of the present invention. The anisotropic conductive film 2 shown in FIG. 3(a) includes a plurality of capsules 9 made of insulating resin. The capsule 9 contains solder metal particles 5 as conductive particles. As the solder material, a low melting point solder containing 18% bismuth was used. The melting point of the solder material is approximately 165°C. For the capsule 9, polyimide resin having a higher softening point than the solder material was used. As the main resin for the anisotropically conductive film 2, a thermoplastic epoxy resin having a lower softening point than the polyimide resin used for the capsule 9 was used. The heating and pressurizing conditions in the bonding step are determined in consideration of the melting point of the conductive particles and the temperature characteristics regarding the softening point of the resin that is the main component of the insulating film of the capsule and the anisotropically conductive film. FIGS. 3(b) and 3(c) show a connection process using the anisotropic conductive film of the present invention. FIG. 3B shows a cross-sectional view of the anisotropic conductive film placed between the connection electrodes and then pressurized. The capsule 9 sandwiched between the electrode 4 of the semiconductor element 1 and the electrode 11 of the insulating base substrate 3 is destroyed by cracks in the insulating film forming the outer wall of the capsule due to the pressure. The distance between the semiconductor element 1 and the insulating base substrate 3 is as follows:
Electrode 4 of semiconductor element 1 and electrode 11 of insulating base substrate 3
The capsule is wider by the height of the electrode part, and the capsule is surrounded by a thermoplastic resin with a low elastic modulus, so the pressure applied to the capsule is small and the capsule does not crack. FIG. 3(c) is a cross-sectional view showing a heated state after pressurization in FIG. 3(b). The heating temperature is the melting point of the solder16
Bonding was carried out at 180°C, which is higher than 5°C and lower than the softening point of 250°C of the polyimide resin forming the outer wall of the capsule. The solder particles between the connecting electrodes bonded to each other to form one large particle, allowing electrical continuity between the connecting electrodes. The capsule that exists between adjacent electrodes is surrounded by a resin with low thermal conductivity, so the solder particles inside are difficult to melt, and even if they melt, they will not form the outer wall of the capsule. Because the heating conditions are lower than the softening temperature of the polyimide resin, the outer wall of the capsule does not melt or flow, maintaining insulation from the outside of the outer wall. Inside the capsule,
In addition to conductive particles for the purpose of electrical conduction, removing the oxide film on the electrode surface and adding flux to assist solder bonding further improves solder adhesion. In addition, if a substance that develops color depending on the load is placed inside the capsule, it will be useful for monitoring the bonding process and inspecting the bonding state. Furthermore, if a substance that generates heat due to load, such as benzoyl peroxide or dicumyl peroxide, is placed in the capsule, it is possible to reduce the amount of heat applied from the outside during bonding.

Embodiment 3 FIGS. 4(a) and 4(b) are cross-sectional views showing a third embodiment of the present invention. In the anisotropic conductive film 2 of FIG. 4(a), there are conductive particles 5 having an insulating film 7.
It is blended at such a high density that the individuals 6 consisting of are in contact with each other. A solvent 12 that dissolves the insulating film 7 is applied to the surfaces of the electrode 11 on the insulating substrate 3 and the electrode 4 on the semiconductor element 1 . The insulating film 7 is made of epoxy resin. The solvent 12 is an ethylene glycol-based solvent, and has the function of swelling and dissolving the epoxy resin. The resin 8 that is the main component of the anisotropically conductive film is a photocurable resin. Figure 4(b)
shows the bonded state of the present invention. Without heating, light is irradiated to maintain contact between the electrodes using the contractile force of the photocurable resin. The insulating film 7 covering the conductive particles 5 between the connecting electrodes is swollen and dissolved by the solvent 12 applied to the electrode surface, exposing the surface of the conductive particle 5 and establishing electrical continuity with the electrode surface. . Since the conductive particles having an insulating film between adjacent electrodes do not come into contact with the solvent 12, the insulating film does not melt, and electrical insulation between the conductive particles is ensured.

[0011]

According to the present invention, it is possible to further reduce the distance between adjacent electrodes, which was limited by the size of conductive particles or solid particles made of conductive particles. Therefore, higher density packaging is possible.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an example using the anisotropically conductive film of the present invention.

FIG. 2 is an explanatory diagram showing a connection process in the embodiment of FIG. 1;

FIG. 3 is a sectional view showing a second embodiment of the invention.

FIG. 4 is a sectional view showing a third embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Semiconductor element, 2... Anisotropically conductive film, 3... Insulating base substrate, 4... Electrode on semiconductor element, 5... Conductive particles,
6... Solid, 7... Insulating film, 8... Resin forming the main body of the anisotropically conductive film, 11... Insulating base substrate-shaped electrode.

Claims (7)

[Claims] 1. A connecting material used between opposing electrodes disposed to establish an electrical connection, wherein a resin that is the main component of the connection material contains a component different from a resin component that is the main component of the connection material. 1. An anisotropically conductive film characterized in that a solid having an insulating film as an outer wall is dispersed therein, and the solid has conductive particles encapsulated therein. 2. In a connecting material used between opposing electrodes disposed to establish an electrical connection, a resin that is the main component of the connection material has a softening temperature different from that of the resin that is the main component of the connection material. An anisotropically conductive film characterized in that a solid having an insulating film as an outer wall is dispersed and blended, and the solid contains conductive particles. 3. The anisotropic conductive film according to claim 1 or 2, wherein the size of the largest conductive particle contained in the individual is smaller than the distance between connected electrodes. 4. The anisotropic conductive film according to claim 1, wherein the insulating film has a capsule shape. 5. According to claim 1 or 2, the individual in which a plurality of conductive particles are included in the insulating film includes pressure-sensitive particles that develop color under load in addition to the conductive particles. Anisotropic conductive film. 6. According to claim 1 or 2, the insulating film contains a plurality of conductive particles, and in addition to the conductive particles, a flux is included to assist bonding during heating. Anisotropic conductive film. 7. According to claim 1 or 2, the individual body in which a plurality of conductive particles are included in the insulating film contains a substance that generates heat by itself in addition to the conductive particles. directional conductive film.