JPH0145950B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a connector, particularly a flat package type IC, a leadless IC, which is made by dispersing and orienting metal fibers in a sheet member made of a non-conductive polymer material. This invention relates to the improvement of anisotropic conductive connectors that are useful for electrical connection of chip carrier type ICs, flexible printed circuit boards, etc.

(Prior art) Anisotropically conductive sheet-like composite materials are used for connections between circuits such as leadless ICs and hybrid circuits. The non-conductive polymer material and conductive fiber material in In a sheet of a non-conductive polymer material, the material is oriented in a substantially constant direction, the polymer material is cured, and the cured material is sliced along a plane substantially perpendicular to the orientation direction of the conductive fiber material. A sheet is known in which a large number of conductive fibers are dispersed and oriented in the thickness direction of the sheet so that some of the conductive fibers penetrate through the sheet.
(See Special Publication No. 56-6083).

Therefore, various types of anisotropically conductive sheet-like composite materials can be made by appropriately selecting the above-mentioned non-conductive polymeric material or the conductive fibrous material dispersed and oriented therein. However, due to the demands for low contact resistance (several + ohms), improved compression cyclic characteristics, and high current capacity, it is especially important to use conductive fibrous materials as metal fibers. IC connector,
It is commonly used as a connector for FPC connection.

However, in products using these metal fibers, the fibers are shortened during the mixing and dispersion process, and as a result, the fiber length follows the Poisson distribution, especially the distribution obtained by the straight line of the Rosin Rammler diagram. Therefore, an anisotropic conductive sheet obtained by curing a polymer material containing such metal fibers and slicing it in a plane perpendicular to the orientation direction of the metal fibers has metal fibers near the cut surface. Even if an edge exists, it is pulled out without being cut by the slicing blade, and in some cases the cut surface is flush with the sheet, so the length of this metal fiber varies. . Therefore, when this type of anisotropic conductive connector is used with pressure contact between electrodes, the pressure contact load is concentrated on the long metal fiber part, and the fiber is cut at the same height as the sheet surface that exists near the fiber. The metal fibers and the like that are attached cannot receive sufficient pressure contact force for electrical connection, and therefore there is a disadvantage that the continuity becomes uncertain or unstable in this part.

(Structure of the Invention) The present invention relates to an anisotropically conductive connector that solves the above-mentioned disadvantages, and includes metal fibers in a member made of a non-conductive polymer material, at least a portion of which is attached to the sheet member. An anisotropically conductive connector is arranged so as to penetrate through the sheet member, and is oriented at a constant angle in the thickness direction of the sheet member, and an anisotropically conductive adhesive layer is provided on at least one surface of the anisotropically conductive connector. It is characterized by:

That is, the present inventors have conducted various studies on improving an anisotropically conductive connector in which metal fibers are oriented on a sheet member made of a non-conductive polymer material, and as a result, the inventors have found that when connecting the electrode body surfaces that are to be electrically connected, In the conventionally known anisotropic conductive connector shown in FIG. 1, in which metal fibers 2 are oriented in the thickness direction of a sheet-like member 1 made of a non-conductive polymer material, this is shown in FIG. 2, for example. As shown above, a metal foil conductor 4,
4', this metal fiber 2
Since the lengths of the connectors vary, the conduction becomes uncertain and unstable. However, as shown in Fig. 3, this anisotropically conductive connector is made of a sheet member 1 made of a non-conductive polymer material. At least one surface of an anisotropically conductive connector 5 has metal fibers 2, a part of which penetrates through the sheet member, and is oriented at an angle α in the thickness direction of the sheet member. A connector is provided with anisotropically conductive adhesive layers 6, 6', and is connected to two printed wiring boards 3, 3' as shown in FIG.
When the metal fibers are pressed and sandwiched between them, all of them fall in the same direction and the pressing force acts on all the fibers, so even if there is some variation in the length of the metal fibers, there will be no partial contact between them. It is possible to obtain stable conduction without causing defects, and the apparent contact area is increased by the conductor contained in the anisotropic conductive adhesive layers 6, 6', so it is even more effective. The present invention was completed by conducting research on the orientation direction of the metal fibers, the range of the inclination angle, the type of anisotropically conductive connector, etc. used for this purpose.

The non-conductive polymer material as a matrix material constituting the anisotropically conductive connector of the present invention and the metal fibers oriented thereon may be of known materials. Therefore, the non-conductive polymeric substances include thermoplastic polymeric substances such as polyester, polyvinyl chloride, polymethyl methacrylate, polyolefin, polyamide, polycarbonate, polystyrene, unsaturated polyester, polyurethane, organopolysiloxane, phenol, Examples include thermosetting polymeric substances such as urea, melamine, and guanamine, as well as rubber-like elastic bodies such as natural rubber and various synthetic rubbers. , curing agent, stabilizer, etc. In addition, since the connector of the present invention is based on the conductivity of this metal fiber, it is necessary that the metal fiber has an electrical resistivity of 10 ^-4 Ωcm or less, and this requires the use of gold. Examples include metal fibers made from copper, nickel, brass, phosphor bronze, aluminum, and the like.
However, these metal fibers must not exhibit ductility or curl due to bending stress or shear stress applied when dispersed in a non-conductive polymer material, and It is necessary to select a material that exhibits rigidity against the bending stress and shear stress that is sometimes applied, and that can break without curling. Copper alloy is said to be the most preferable for this purpose, but this material has a diameter of 10 to 10 mm. 50μm,
It is preferable to have a length of 10 to 50 mm.

In addition, the metal fibers used here may be manufactured by a method such as a drawing method, a melt spinning method, or a chatter vibration cutting method, but the cross section of the metal fiber made by this chatter vibration cutting method is It has a roughly triangular shape, has a large surface roughness, and has good adhesion to the non-conductive polymer material, has high machinability and fiber diameter accuracy, and is inexpensive, so it was made using the chatter vibration cutting method. It is better to take it as a fact. In order to improve the adhesion with non-conductive polymer substances, it is desirable to couple the surface of these metal fibers with a silane coupling agent. Glycidoxypropyltrimethoxysilane, N-β
(Aminoethyl)γ-aminopropyltrimethoxysilane and the like are exemplified.

The orientation of the metal fibers into a non-conductive polymer material can be achieved by mixing the metal fibers into a non-conductive polymer material, and then molding this mixture into a rod or sheet using an extrusion molding machine or an injection molding machine. During this molding, the metal fibers are often oriented in the flow path direction when passing through a plate or die at the exit of the molding machine. The blending amount of this metal fiber is 0.1 to 20% of the non-conductive polymer material.
The amount may be set to % by volume, preferably 0.5 to 10% by volume, and when oriented, the fiber length of the metal fibers follows a Poisson distribution, particularly a distribution obtained from a Rosin-Rammler diagram.

The anisotropically conductive connector used in the connector of the present invention is obtained by curing the thus obtained molded product with oriented metal fibers, and then curing the molded product at an angle to the orientation direction of the metal fibers. It can be obtained by slicing it into sheets.
The thickness of this sheet is required to be such that at least a portion of the metal fibers penetrate through this sheet member, so the metal fibers mixed with a non-conductive polymeric material as a matrix are used. Therefore, this should be in the range of 0.1 to 1 mm. In addition,
The slicing angle may be determined depending on the orientation angle of the metal fibers in the intended anisotropic conductive connector of the present invention, but if the angle is less than 5 degrees, the above-mentioned tilting effect will not be sufficiently expected. If the angle is 45° or more, the contact force will decrease significantly due to the elastic recovery force of the matrix made of non-conductive polymer material, and the reliability of contact will be impaired.
The preferred angle is between 10 and 20 degrees, although it may be in the range of 45 degrees.

The connector of the present invention is made by providing an anisotropically conductive adhesive layer on at least one surface of the anisotropically conductive connector thus obtained, and this anisotropically conductive adhesive layer is For example, when the connector is held in pressure contact between two printed wiring boards, the metal fibers dispersed and oriented in the non-conductive polymer material of this anisotropically conductive connector are all tilted in a certain direction. Therefore, when unique vibrations, shocks, etc. are applied from the outside, it may cause a twisting motion, which may cause the inconvenience of shifting the position of the electrons that should be connected, so this should be prevented. Since the adhesive is used to reliably bond electronic components to be connected to the anisotropically conductive connector, it must not exhibit fluidity at the operating temperature. Therefore, the anisotropically conductive adhesive may be a thermoplastic resin such as polyamide, polyethylene, polypropylene, polyvinyl acetate, polymethyl methacrylate, polyester, polyurethane or a co-blend or copolymer thereof, epoxy resin, or phenol. A curing agent, if necessary, is added to the adhesive composition made of resin, thermosetting resin such as urethane resin, synthetic rubber such as nitrile rubber, butyl rubber, chloroprene rubber, silicone rubber, etc.
Gold, silver, copper, aluminum, nickel, tungsten, titanium, cobalt, or alloys thereof are added to a preferably hot-melt adhesive polymer composition containing crosslinking agents, fillers, pigments, stabilizers, coupling agents, etc. Furthermore, powder of a conductive metal or metal compound such as tungsten carbide, nickel carbonyl, and tin dioxide may be added. In this case, if the amount of the conductive metal or metal compound is less than 0.05 parts by volume per 100 parts by volume of the adhesive polymer composition, the conduction density at the connection part will decrease and the reliability of the connection will decrease. If it is more than 100%, a chain will occur between the conductive particles due to pressure heating during bonding, making it difficult to maintain insulation between adjacent terminal electrodes.
A range of 0.5 to 40 parts by volume is required, with a preferred range of 2 to 25 parts by volume.

The connector of the present invention is made by providing the above-described anisotropically conductive adhesive layer on the surface of the above-described anisotropically conductive connector, and this adhesive layer is provided on at least one surface of the anisotropically conductive connector. This can be done on both sides or just one side, but
This does not have to be the entire surface, but may be arranged at appropriate positions at specific intervals.

The connector of the present invention is configured as described above, and according to this, the metal fibers in the anisotropically conductive connector are oriented to penetrate through the sheet member at a certain angle in the thickness direction. When pressed between printed circuit boards, this pressing force acts on all the metal fibers, and even if the length of the metal fibers varies, there will be no contact failure and stable conduction can be obtained. Since this anisotropic conductive connector is coated with a conductive adhesive, the contact area between the connector and the printed circuit board is increased, and electronic components incorporating this connector are subjected to external vibrations, shocks, etc. This adhesive force provides an advantage in that positional displacement does not occur even when the adhesive is moved.

Next, examples of the present invention will be given, in which parts are by weight.

Example: 100 parts of silicone rubber compound KE-171U [trade name manufactured by Shin-Etsu Chemical Co., Ltd.], 65 parts of copper alloy metal fibers cut to a length of 30 mm with a diameter of 30 μm, and silicone rubber vulcanizing agent C-2 [Company product name]
2 parts were kneaded with a mixing roll, extruded into a round bar with a diameter of 5 mm using a rubber extruder, and heated and vulcanized in an oven at 170°C for 10 minutes, resulting in a molded product with metal fibers oriented in the extrusion direction. Obtained.

Next, this round bar was sliced into 0.2 mm thick pieces at right angles to the vertical direction and at angles of 5°, 20°, and 45° to make four types of anisotropically conductive sheets. When the pressure contact amount and contact resistance were measured by sandwiching the material between electrodes, the results shown in Figures 5 and 6 were obtained, and the slices sliced at an inclination angle of 20° had the best characteristics. Indicated.

Next, the surface of the anisotropically conductive connector thus obtained was coated with a silane coupling agent, KBM-
After coupling with 403 [trade name manufactured by Shin-Etsu Chemical Co., Ltd.], 7 parts by volume of nickel powder of 350 mesh pass was added to epoxy resin and Araldite.
An anisotropically conductive adhesive obtained by dispersing and orienting 100 parts by volume of AW106 (trade name manufactured by Ciba Geigy) and 80 parts by volume of hardening agent HV953U (trade name manufactured by Ciba Geigy) to a thickness of 10 μm. This was applied to a flat package IC with electrode terminals at a pitch of 1.27mm to make a connector, and then bonded by heating and pressing at 200℃ x 15Kg/cm ² , and then attached to a plastic molded housing. When the connected structure was fixed by pressure welding and subjected to a vibration test at a width of 1.2 mm and a frequency of 55 Hz, the results shown in Figure 7A were obtained, indicating that this structure has high reliability. However, this product was also subjected to a thermal cycle of -40°C x 30 minutes → +23°C → +80°C x 30 minutes to evaluate the connection reliability based on the difference in thermal expansion coefficient. As shown in Figure 8, it was confirmed that it could be used without any problems.

However, for comparison, we used the anisotropically conductive connector obtained above without applying the anisotropically conductive adhesive, and made it into a flat package IC by pressure welding with a plastic mold housing in the same manner as above. When connected, the fibers shifted in the direction of inclination in the vibration test described above 120 hours after the start of the test, resulting in an increase in resistance as shown in FIG. 7B.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view of a conventionally known anisotropically conductive connector, Fig. 2 is a longitudinal cross-sectional view of the anisotropically conductive connector sandwiched between electrodes, and Fig. 3 is a longitudinal cross-sectional view of the anisotropically conductive connector of the present invention. , Fig. 4 is a vertical cross-sectional view of this material which is pressure-bonded and sandwiched between electrodes, and Figs. 5 and 6 show the amount of compression and the contact resistance value of the anisotropic conductive connector used in the connector of the present invention in the embodiment. Figure 7 shows the results of a vibration test of a connected structure using the connector of the present invention, and Figure 8 shows the results of a thermal shock test of this connected structure. .

Claims (1)

[Claims] 1 Metal fibers are arranged in a sheet member made of a non-conductive polymer substance so that at least a part of the metal fibers penetrates the sheet member, and the metal fibers are arranged at a constant angle in the thickness direction of the sheet member. A connector characterized in that an anisotropically conductive adhesive layer is provided on at least one surface of an anisotropically conductive connector which is oriented in the direction of the anisotropically conductive connector.