JP2006032335A - Anisotropic conductive adhesion film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anisotropic conductive adhesion film capable of reducing the secondary coagulation of conductive particles with a small amount of additional particles and coping with a fine pitch while keeping conventional connection properties. <P>SOLUTION: The measurement ratio of the number of conductive particles a per unit area of the anisotropic conductive adhesion film and the number of conductive particles b after circuit connection (b/a×100) is 30% or more. It is preferable to carry out the measurement of the conductive particles by using an optical microscope in a scale factor of 200 times. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an anisotropic conductive adhesive film that bonds and fixes an electronic component and a circuit board or circuit boards and electrically connects both electrodes.

The anisotropic conductive adhesive film is used to connect a circuit between a substrate and a circuit or an electrical connection between a substrate circuit and a semiconductor chip, for example, to electrically connect a liquid crystal substrate and a driving substrate with a flat cable. It is used for. The anisotropic conductive adhesive film comprises an insulating adhesive and conductive particles, and the conductive particles are particles or metal particles in which the surface of the polymer core is substantially covered with a thin metal layer, and The particles are a mixture of both. The manufacturing method of this anisotropic conductive adhesive film usually includes an insulating resin such as an epoxy resin, a coupling agent, a curing agent, a curing accelerator, and an adhesive varnish mixed and dispersed with conductive particles on a carrier film (separator). It is manufactured by applying and drying. Further, a varnish that does not contain conductive particles is applied to the surface to form a multilayer.
JP 07-136556 A Japanese Patent Laid-Open No. 02-230672 JP 60-184478 A

  By the way, in recent years, with the development of electronic devices, the density of wirings and the functions of circuits have been advanced. However, it has been demanded that the thickness is 50 μm or less. In connection with this, also in the connection in a connection member, it is requested | required that it can respond to a high-density connection circuit.

The basic idea for increasing the resolution of an anisotropic conductive adhesive film is to reduce the particle size of the conductive particles smaller than the insulating portion between adjacent electrodes, ensuring insulation between adjacent electrodes. Thus, by setting the content of the conductive particles to such an extent that the particles do not contact each other, the conductivity at the connection portion can be obtained with certainty. However, in the conventional method, conductive particles having a small diameter are added and dispersed in the adhesive varnish, so that the adhesive varnish is mixed and dispersed before it is applied to the carrier film. If the conductive particles settle or are charged and secondary aggregation of the conductive particles is likely to occur, insulation between adjacent electrodes cannot be maintained, and if the content of the conductive particles is reduced, the connection is established. Since the number of conductive particles on the power circuit also decreases, the number of contact points is insufficient, and conduction between the connection electrodes cannot be obtained.
In addition, as the connection wiring density is increased, the area of the connection electrode is reduced. Therefore, in order to prevent an increase in connection resistance, the amount of conductive particles added must be increased. When connecting / fixing the substrate and the substrate or the substrate and the semiconductor chip by applying pressure to the substrate and the semiconductor chip via the anisotropic conductive adhesive film, the conductive particles between the connection electrodes are bonded to the connection electrode and the connection electrode together with the insulating adhesive. As a result, a large amount of conductive particles gather between the connecting electrodes, so that the possibility of a short circuit between the electrodes becomes higher. Therefore, it has been difficult to increase the resolution of the connecting member while maintaining long-term reliability.

  The present invention suppresses the flow of conductive particles at the time of connection, reduces the secondary aggregation of the conductive particles with a small amount of added particles, and maintains the conventional connection characteristics, and is capable of supporting the fine pitch. An object is to provide an adhesive film.

This invention solves the said subject by providing the following anisotropically conductive adhesive films.
(1) Anisotropic conductive adhesion in which the measurement ratio (b / a × 100) between the number of conductive particles a per unit area of the anisotropic conductive film and the number of conductive particles b after circuit connection is 30% or more the film.
(2) The above (1), wherein the conductive particles are measured using a 200 × optical microscope.
An anisotropic conductive adhesive film described in 1.

  Since the anisotropic conductive adhesive film according to the present invention suppresses the flow of conductive particles at the time of circuit connection, the conventional connection characteristics can be maintained even if the amount of the added conductive particles is reduced, and two conductive particles are used. Since the secondary agglomerated particle size can be reduced, it can be applied to fine pitches, and its industrial value is great.

Hereinafter, the present invention will be described with reference to the drawings shown in the embodiments, but the present invention is not limited thereto.
1 (a) to 1 (c) and FIG. 2 are cross-sectional schematic views of an anisotropic conductive adhesive film according to the present invention. 1 (a) to (c) in which conductive particles 1 are dispersed on the surface layer of the insulating adhesive 2 formed on the separator 3 and then the conductive particles are embedded in the surface layer of the insulating adhesive. ). The degree of embedding of the conductive particles varies depending on the type of the insulating adhesive, but basically there is no problem unless the conductive particles are peeled off from the insulating adhesive. As shown in FIG. 2, the effective distance for embedding can be obtained experimentally by attaching the insulating adhesive 4 to the anisotropic conductive adhesive film of FIG. 1 and placing the conductive particles at specific positions in the thickness direction. . It is necessary for the particle diameter of these conductive particles to be smaller than the insulation width (space) of the circuit to be connected, in order to maintain the insulation with the adjacent circuit.

  The method of uniformly arranging the surface layer of the insulating adhesive layer formed on the peelable film substrate is, for example, spraying, use of magnetic field or charging, filling of mesh holes, use of screen printing, use of surface tension, etc. However, a method in which conductive particles are charged with the same charge and dispersed is preferable. Specifically, a method in which an air tube is connected to an ejector, conductive particles are dropped into a suction port of the ejector, and dispersed together with an air flow can be applied.

The conductive particles arranged on the surface of the insulating adhesive layer in which the conductive particles are formed on the peelable film substrate do not stick to the insulating adhesive on the surface of the insulating adhesive on which the conductive particles are arranged. It is possible to embed in the surface layer of the insulating adhesive by overlapping the plastic film having the surface and applying pressure by pressing or laminating. Furthermore, it is preferable to heat the insulating adhesive when embedding the conductive particles. The heating temperature is such that the insulating adhesive is not cured, and is preferably heated to such an extent that the tackiness and plastic deformation necessary for the subsequent connection between the substrate and the substrate remain, and other times and It can be experimentally determined in advance depending on the type of the insulating adhesive together with the pressure condition and the like.
When both circuit thicknesses to be connected are thick, an insulating adhesive is further bonded to the insulating adhesive surface on which the conductive particles are arranged, and the conductive particles are placed at specific positions in the thickness direction of the insulating adhesive. An arranged multilayer adhesive film is preferred.

  As a method of connecting a circuit using the obtained anisotropic conductive adhesive film, for example, the separator is peeled off in a state where the adhesive film is temporarily attached to the circuit, and another circuit to be connected is hot-pressed on the surface, or What is necessary is just to stick with a heating roll. FIG. 3 schematically shows a state in which circuits are connected by such a method. The adhesive 2 softens and flows due to heat and pressure, and the conductive particles 1 whose surface is coated with metal are also softened. Since they are deformed and contact each other, conductive bonding between both circuits 5, 5 'becomes possible.

  In the anisotropic conductive adhesive film using the present invention, the conductive particles are arranged on the surface layer of the insulating adhesive, so that the conductive particles are not easily affected by the adhesive flow at the time of circuit connection. Since there is little movement of conductive particles, circuit connection can be made efficiently. Since the efficiency at the time of circuit connection is improved and the conductive particle content can be reduced by disposing the insulating adhesive only on the surface layer, the secondary aggregated diameter of the conductive particles is also reduced. As a result, the measurement ratio (b / a × 100) between the number of conductive particles a per unit area of the anisotropic conductive adhesive film and the number of conductive particles b after circuit connection may be 30% or more. Can be connected efficiently.

The invention is explained in more detail by means of examples.
Phenoxy resin PKHA (product name: 40 parts by weight), which is a polymer epoxy resin, and NovaCure HP-3942HP (product made by Asahi Kasei Kogyo Co., Ltd.), a liquid epoxy resin containing a microcapsule type latent curing agent Name: 100 parts by weight) was diluted at a weight ratio of 30/70 so as to be 30% (by weight) of ethyl acetate to obtain an adhesive varnish. This adhesive varnish was cast and dried on a separator made of a 50 μm biaxially stretched polyethylene terephthalate resin film that had been subjected to a release treatment, and an average thickness of 23 μm film A, an average thickness of 20 μm film D, and an average thickness. A film E having a thickness of 15 μm, a film F having an average thickness of 11 μm, a film J having an average thickness of 3 μm, a film K having an average thickness of 8 μm, and a film L having an average thickness of 12 μm were obtained.

A plastic particle having a Ni / Au plating film having an average diameter of 5 μm and an average thickness of 0.25 μm is fluidized through an air ejector from a container having a volume of 0.1 liter and a pressure of 0.5 MPa from the air tube. Then, the film A, D, E, and F were respectively sprayed at an average rate of 8000 pieces / mm ² to obtain films B, G, H, and I. The films A, D, E, and F were moved at a speed of 0.6 m / min, and the air tube was fixed at a height of 10 cm from the films A, D, E, and F, and was sprayed in the horizontal direction. . On this film B, the release treatment surface of the separator made of a biaxially stretched PET resin film subjected to the release treatment and the conductive particle dispersion surface are overlapped face to face, under conditions of a temperature of 50 ° C., a pressure of 0.3 MPa, and a speed of 2 m / min. The anisotropically conductive adhesive film C was obtained by pressing and fixing the dispersed conductive particles through the two laminating rolls into the surface layer of the insulating adhesive.

At this time, the conductive particles were embedded so that the conductive particles did not fall off from the insulating adhesive. Film G and film J, film H and film K, film I and film L were bonded together under the same lamination conditions to obtain films M, N and O. This anisotropic conductive adhesive film C was applied to an ITO glass substrate by applying heat and pressure at 100 ° C. and 2 kg / cm ² for 5 seconds, and after peeling off the separator, a bare chip having 50 μm × 90 μm gold bumps was aligned. Then, the circuit was connected by heating and pressing at 200 ° C. and 30 kg / cm ² for 20 seconds. The anisotropic conductive adhesive film C was observed with a 200 × optical microscope, and the number of conductive particles b on the bare chip bump after circuit connection with the number of conductive particles a per unit area was measured. For the films M, N, and O, connection experiments and measurements similar to those for the film C were performed. Based on the experimental results, the particle density to be dispersed was determined, and similar films C, M, N, and O were produced at the particle density. A connection experiment was performed on the produced film under the same conditions, and the measurement of the secondary aggregation state and the connection resistance between opposed electrodes and the connection resistance between adjacent electrodes were measured.

Conventional Example An insulating adhesive layer 4 having no conductive particles having a thickness of 15 μm was produced on a separator using the same adhesive varnish as in the example. In addition, the same conductive particles (added amount 9.5% by volume) as used in the examples were dispersed in the adhesive varnish to form an insulating adhesive layer 2 containing conductive particles having a thickness of 8 μm. Produced. The insulating adhesive layer 4 and the insulating adhesive layer 2 were bonded together to obtain an anisotropic conductive adhesive film having a two-layer structure shown in FIG. Using the two-layer anisotropic conductive adhesive film, the same connection and measurement as in the example were performed.
Table 1 shows the measurement results of the example and the conventional example.

  In this example, the arrangement of the conductive particles is concentrated only on the layer very close to the surface layer of the insulating adhesive, the particle flow at the time of circuit connection is reduced, and the particle capture rate (b / a × 100) is set. It can be seen that by setting the content to 30% or more, the particle density can be reduced, so that the amount of added conductive particles can be reduced. If the conductive particles are within the effective range from the surface of the insulating adhesive to 8 μm than the conventional example, and the secondary aggregated particle size is also within this range, the aggregated particle size can be made smaller than that of the conventional example.

The cross-sectional schematic diagram which shows the anisotropic conductive adhesive film using this invention which has arrange | positioned electroconductive particle to the surface layer of an insulating adhesive agent. (A) A state in which conductive particles are on the surface of the insulating adhesive. (B) A state in which a part of the conductive particles is embedded in the surface layer of the insulating adhesive. (C) State where conductive particles are embedded in the surface layer of the insulating adhesive. The cross-sectional schematic diagram which shows the anisotropic conductive adhesive film using this invention which bonded the insulating adhesive to the electroconductive particle arrange | positioned at the surface layer of the insulating adhesive. The cross-sectional schematic diagram which shows the connection condition of the circuit by the anisotropically conductive adhesive film using this invention. The cross-sectional schematic diagram which shows the anisotropic conductive adhesive film of the 2 layer structure used by the prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive particle 2 Insulating adhesive 3 Separator (peelable film) 4 Insulating adhesive 5 Circuit 5 'circuit

Claims (2)

An anisotropy in which the measurement ratio (b / a × 100) between the number of conductive particles a per unit area of the anisotropic conductive film and the number of conductive particles b after circuit connection is 30% or more. The anisotropic conductive adhesive film according to claim 1, wherein the conductive particles are measured using a 200 × optical microscope.

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