JP2002212518A - Anisotropic conductive adhesive sheet and electric and/or electronic element using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anisotropic conductive adhesive sheet which can ensure the anisotropic conductivity only by a pressing treatment without needing a heating treatment. SOLUTION: This anisotropic conductive adhesive sheet is formed by forming on a separator 11 an adhesive layer in which conductive particles 13 or conductive short fibers are dispersed and arranged in the horizontal direction in one layer in an extent that the particles or the short fibers do substantially not contact with each other. The sheet is finely cut in a proper size, and the obtained adhesive layer is nipped between two conductive fine elements and then pressed. Thus, the two conductive fine elements can electrically be connected to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anisotropic conductive pressure-sensitive adhesive sheet and an electric and / or electronic device using the same.

[0002]

2. Description of the Related Art Flip chip assemblies (flip chip assemblies)
assembly), CSP (chip size / scale package), M
CM (multichip module), COF (chip on flexible
2. Description of the Related Art In the manufacture of printed circuit boards, etc., anisotropic conductive adhesives are used for bonding between fine terminals such as terminals and the like of terminals of devices such as integrated circuits and printed wiring / circuit boards.

[0003] The terminals as described above (terminals and the like in the element are treated as "fine elements" in this specification) are arranged at an extremely short distance, and therefore, terminals between adjacent terminals are arranged between the terminals. The conductivity must not occur at Therefore, for such bonding, an anisotropic conductive adhesive which does not have conductivity in a direction parallel to the bonding surface and has conductivity between the target pair of terminals to be bonded in a direction perpendicular to the direction is used. Must be used. Such anisotropic conductive adhesive is usually an adhesive obtained by dispersing gold beads (gold-plated bead material) in a one-component reaction type epoxy resin.
For example, the adhesive is processed into a film and used (for example, an anisotropic conductive film [AFC: anisotropic conductive fil of “FP series” manufactured by Sony Chemical Corporation).
m]). This film is sandwiched between the terminals arranged on the two elements, and, for example, 170
The mixture is heated at 180 ° C. for several minutes to 10 minutes to complete the melt-solidification bonding. FIG. 2 shows the state of such adhesion.

In the example of FIG. 2, a substrate 1 and an integrated circuit IC
Anisotropic conductive adhesive 4 is applied to terminal 3 which is a bump of 2.
Although the gold beads 5 in the inside are in contact with each other to ensure the conductivity between the terminal pairs, the dispersion of the gold beads 5 in the anisotropic conductive adhesive 4 is sparse in the portion without the terminals 3. No conductivity.

[0005]

However, there is a problem that the conventional one-component reactive epoxy resin-based anisotropic conductive adhesive requires pressure heating. One is that the pressure bonding heating process itself is a waste of time and cost, and the other is that heating may cause breakage of fine elements such as disconnection on a substrate or IC, which may cause a decrease in yield. is there.

Accordingly, an object of the present invention is to provide an anisotropic conductive pressure-sensitive adhesive sheet which can secure anisotropic conductivity only by pressure bonding without requiring heating.

[0007]

SUMMARY OF THE INVENTION According to the present invention, there is provided a pressure-sensitive adhesive layer in which conductive particles or short fibers are arranged and dispersed in one layer to such an extent that they do not substantially contact each other in a planar direction. An anisotropic conductive material comprising: a pressure-sensitive adhesive layer formed on a separator so that when the pressure-sensitive adhesive layer is sandwiched between the two pressure-sensitive adhesive layers, the two conductive fine elements can be electrically connected to each other. An object of the present invention is to provide an adhesive sheet and an electric and / or electronic element using the anisotropic conductive adhesive sheet.

The technical concept of the anisotropic conductive pressure-sensitive adhesive sheet of the present invention will be described with reference to FIG. 1 in the case where conductive beads or conductive beads are used as conductive particles or short fibers. The pressure-sensitive adhesive layer 12 in which the conductive beads 13 are sparsely dispersed is provided on the separator 11 to prepare the anisotropic conductive pressure-sensitive adhesive sheet of the present invention. Simply cut such an anisotropic conductive pressure-sensitive adhesive sheet into a desired width and press-bond as shown in FIG. Conductivity is ensured between the bump pairs via the conductive beads 13, and the other portions are insulated. Even when conductive short fibers are used, the conductive properties are secured between the pair of bumps via the conductive short fibers, and the conductive short fibers are insulated from the adhesive to the extent that they are insulated in other portions. There is no problem if it is distributed to In the present invention, the shape of the “conductive particles or short fibers” is typically a bead or a fiber having a circular cross section, and is preferably a particle shape, for example, an elliptical sphere, an oval shape, a sea urchin shape, various polyhedral shapes. Including irregular shapes such as
The short fiber shape means that, for example, a cross-sectional shape includes an elliptical shape, a star shape, various shapes such as various polygonal shapes, and also includes a whisker shape. As can be seen from FIGS. 1 and 2, it is needless to say that the particle diameter and cross-sectional diameter of the conductive particles or short fibers are desired to be substantially uniform. In addition, although the adhesion by the anisotropic conductive pressure-sensitive adhesive sheet of the present invention is adhesion, elements such as integrated circuits and printed wiring / circuit boards are generally finally packaged. The anisotropic conductive pressure-sensitive adhesive sheet of the present invention can sufficiently withstand long-term use of the element. However, it is natural that the anisotropic conductive pressure-sensitive adhesive sheet of the present invention can sufficiently withstand the long-term use of the element even in the case of not packaging.

The conductive particles or short fibers usable in the present invention include, for example, various metal particles or short fibers, nickel-coated glass fibers, gold-nickel-coated carbon particles, gold-coated metal particles, and gold-nickel-coated resin particles. Examples thereof include, but are not limited to, as long as conductivity and durability can be ensured. Specific examples of such particles or short fibers include “Bright PF” which is a nickel-coated glass fiber, “Bright GNC-Gr” which is a gold-nickel-coated carbon particle, “Bright GNM” which is a gold-coated metal particle, and gold-coated metal particles. "Bright GNR-EH" which is a nickel-coated resin particle can be mentioned (all of them are manufactured by Nippon Chemical Industry Co., Ltd.). Among these, those coated with gold are particularly preferable in terms of conductivity and stability. In addition, a material in which silica is used as a base material and plated with a conductive metal such as gold can also be used. The fiber diameter or particle diameter varies depending on the specific application target of the anisotropic conductive pressure-sensitive adhesive sheet of the present invention, but is preferably 3 to 50 μm.

As the separator, a polyethylene film, a polypropylene film, a polymethylpentene film, etc., which itself has releasability, can be used as a separator as it is, but these films, polyethylene terephthalate film, polyvinyl chloride film, etc. It is preferable from the viewpoint of the ease of peeling that various films coated with a compound imparting releasability such as a silicone-based or fluorine-based compound are used as the separator.

The pressure-sensitive adhesive of the pressure-sensitive adhesive layer may be an acrylic
A rubber-based or silicone-based pressure-sensitive adhesive can be used, but an acrylic pressure-sensitive adhesive is preferable in terms of cost and durability. It is preferable that the pressure-sensitive adhesive is somewhat cross-linked from the viewpoint of durability and the like.

The thickness of the pressure-sensitive adhesive layer varies depending on the particle size or cross-sectional diameter of the conductive particles or short fibers, the ratio of the conductive particles or short fibers in the pressure-sensitive adhesive, and the like. It is in the range of 4 μm, preferably in the range of −2 μm to 0 μm as compared with the diameter of the conductive particles or short fibers.
If the proportion of the conductive particles or short fibers in the pressure-sensitive adhesive increases, the thickness of the pressure-sensitive adhesive layer is generally and desirably made closer to the diameter of the conductive particles or short fibers.

[0013]

Next, embodiments of the present invention will be described, but the present invention is not limited thereto. Note that FIGS. 1 and 2 described above are conceptual diagrams for facilitating the understanding of the technical idea of the present invention, and that the ratios of the sizes of the respective members do not represent actual ones. I refuse.

The proportion of the conductive particles or short fibers dispersed in the pressure-sensitive adhesive of the pressure-sensitive adhesive layer depends on the kind of the pressure-sensitive adhesive, the material of the conductive particles or short fibers and the particle diameter or cross-sectional diameter, and further, the difference of the present invention. It greatly differs depending on the specific application target of the isotropic conductive pressure-sensitive adhesive sheet. As an example, in the case of using "Bright GNR-EH" which is an acrylic adhesive and gold-nickel coated resin particles, the content is preferably 0.3 to 20% by weight, more preferably 1 to 5% by weight based on the adhesive. . In the case of conductive short fibers, it may be considered that the conductive short fibers are substantially aligned in a direction whose major axis is parallel to the surface of the pressure-sensitive adhesive layer.

An example of the method for producing the anisotropic conductive pressure-sensitive adhesive sheet of the present invention will be described below. An appropriate amount of conductive particles or short fibers is dispersed in a solution of the adhesive dissolved in an appropriate solvent.
The resulting pressure-sensitive adhesive solution is coated on the separator by various coating methods such as screen printing or gravure coating, dried to form a pressure-sensitive adhesive layer, and further a second separator is used as necessary until use. To form an anisotropic conductive pressure-sensitive adhesive sheet of the present invention. In use, the sheet is, of course, cut into an appropriate size.

[0016]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

Example 1 A solution was prepared by dissolving an acrylic pressure-sensitive adhesive in a toluene solvent to a concentration of about 40%. About 1% by weight of "Bright GNR-EH", which is gold-nickel-coated resin particles, was added to the above solution and stirred to prepare a dispersion. This dispersion was solid-coated by screen printing on a separator, which was a silicone-treated polyethylene terephthalate film having a thickness of about 100 μm, and dried by heating to produce the anisotropic conductive pressure-sensitive adhesive sheet of the present invention. The average particle (bead) diameter of the gold-nickel-coated resin particles is 5 μm, the true specific gravity is 1.40, the resin is a benzoguanamine-based resin, and the gold film thickness is 200 ± 50 Å. The thickness of the portion of the pressure-sensitive adhesive layer containing only the pressure-sensitive adhesive was 4.5 μm. Further, the acrylic pressure-sensitive adhesive was slightly cross-linked with an appropriate amount of a cross-linking agent.

This anisotropic conductive pressure-sensitive adhesive sheet is cut into small pieces,
An adhesive layer is attached to the terminal portion of the substrate as shown in FIG.
The separator was peeled off, and then the terminal portion of the IC was attached, pressure was applied, and the terminals were bonded. Substrate and IC
It was confirmed that the terminals were electrically connected, and that insulation between adjacent terminals was secured. It was also confirmed that when these were packaged according to a conventional method, they had sufficient durability.

[0019]

The flip chip assembly (flip chip assembly)
assembly), CSP (chip size / scale package), M
CM (multichip module), COF (chip on flexible
In the production of printed circuit boards, etc., the anisotropic conductive adhesive sheet of the present invention is cut into small pieces, and the above-mentioned adhesive is used for bonding between fine elements such as terminals of integrated circuits and printed wiring / circuit boards. Adhesion using the adhesive force of the sheet eliminates the need for a heating step in a pressed state, which is extremely advantageous in terms of time and cost. Also, when using an anisotropic conductive adhesive in which gold beads (gold-plated bead material) are dispersed in a conventional one-component reaction type epoxy resin,
Heating may cause breakage of fine elements such as disconnection on a substrate or IC, which may cause a decrease in yield. However, when the anisotropic conductive pressure-sensitive adhesive sheet of the present invention is used, there is no such risk.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of the anisotropic conductive pressure-sensitive adhesive sheet of the present invention.

FIG. 2 is a cross-sectional view showing a state in which a bump on a substrate is electrically connected to a bump on an IC using a conventional anisotropic conductive adhesive.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 IC 3 Bump 4 Anisotropic conductive adhesive layer 5 Conductive beads 11 Separator 12 Anisotropic conductive adhesive layer 13 Conductive beads

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05K 3/32 H05K 3/32 B (72) Inventor Yukio Takamisawa 2-1-1, Hagoromocho, Tachikawa-shi, Tokyo No. Cosmotec Co., Ltd. (72) Inventor Makoto Kuwahara 2-1-1-10 Hagoromocho, Tachikawa-shi, Tokyo Stock Company Cosmotech Co., Ltd. (72) Atsushi Takano 2-1-110 Hagoromocho, Tachikawa-shi, Tokyo Stock Cosmotech Co., Ltd. (72) Inventor Megumi Horiuchi 1-23-1, Kagurechi, Fujiyoshida City, Yamanashi Prefecture Inside Citizen Electronics Co., Ltd. (72) Inventor Shinobu Nakamura 2666-3, Funatsu, Kawaguchiko-cho, Minamitsuru-gun, Yamanashi Prefecture Kawaguchiko Precision Co., Ltd. F term (reference) 4J004 AA04 AA05 AA10 AA11 AB01 BA02 BA07 DA02 DA03 DA04 DB02 EA05 FA05 4J040 CA001 DF021 EK031 HA066 JA09 JB09 JB10 KA32 LA09 MA02 MB03 NA20 NA21 PA23 5E319 AA03 AB05 BB16 CC61 5F044 LL09 NN05 NN19

Claims (3)

[Claims] 1. A pressure-sensitive adhesive layer in which conductive particles or short fibers are arranged and dispersed in one layer so that they do not substantially contact each other in a planar direction, and the pressure-sensitive adhesive layer is sandwiched between two conductive fine elements. An anisotropic conductive pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed on a separator so that the two conductive fine elements can be electrically connected to each other when pressure-bonded. 2. The conductive particles or short fibers are at least one material selected from the group consisting of nickel-coated glass fibers, gold-nickel-coated carbon particles, gold-coated metal particles, and gold-nickel-coated resin particles. The anisotropic conductive pressure-sensitive adhesive sheet according to claim 1, wherein: 3. An electric and / or electronic device using the anisotropic conductive pressure-sensitive adhesive sheet according to claim 1.