JP2000340036A - Anisotropic conductive connection body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a connection structural body of an electric circuit having an excellent connection resistance value and connection reliability by using a flexible printed wiring board on which an inexpensive solder alloy layer is formed instead of expensive gold plating. SOLUTION: In this connection structural body of an electric circuit, a board with a wiring pattern formed is connected to a flexible printed wiring board having a wiring pattern connected to the aforementioned wiring pattern through an anisotropic conductive adhesive layer that is made by dispersing copper alloy particles in a binder resin containing a thermosetting resin so as to be electrically insulated in its surface direction and to conduct a current in its width direction. In the case, the connection surface of the wiring pattern of the flexible printed wiring board is formed of a solder alloy, and the copper alloy particles are alloyed with the solder alloy in the connection parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anisotropic conductive connector for electrically connecting a flexible printed wiring board (FPC board) made of a polyimide film or the like to a printed wiring board (PC board).

[0002]

2. Description of the Related Art The following two methods are generally known as methods for joining a flexible printed wiring board to a wiring pattern on a wiring board. One is a method of soldering a wiring pattern on a wiring board and a corresponding wiring pattern on a flexible printed wiring board. the other one is,
This is a method of thermocompression bonding via an anisotropic conductive film. In this case, the wiring of the wiring board and the wiring of the flexible printed wiring board are formed by applying nickel plating and gold plating on copper wiring. As the conductive particles in the anisotropic conductive film, nickel particles and plastic particles obtained by plating gold are usually used.

[0003]

When soldering is used as a method for joining a wiring pattern on a wiring board to a flexible printed wiring board, both the conduction resistance value and the conduction reliability are excellent. When the pitch between the terminals becomes narrow, there is a problem that it is difficult to solder and that the insulation between the terminals is likely to be reduced.

On the other hand, in the case of thermocompression bonding via an anisotropic conductive film, nickel plating and gold plating must be applied to copper wiring in order to reduce the connection resistance value and to increase the reliability of the connection portion, resulting in high cost. Met. Nickel plating,
A flexible printed wiring board on which a solder alloy layer is formed instead of gold plating has the following problems when joined via an anisotropic conductive film.

That is, when gold-plated resin particles are used as the conductive particles in the anisotropic conductive film, gold is diffused into the solder alloy, and the connection reliability is reduced.
In addition, when nickel particles are used as the conductive particles, there is a problem that the connection resistance value is increased because nickel has a high specific resistance value. The present invention uses a flexible printed wiring board of a wiring pattern in which an inexpensive solder alloy layer is formed instead of expensive nickel and gold plating,
An object of the present invention is to provide an anisotropic conductive connection body having excellent connection resistance and connection reliability.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above problems, and as a result, an anisotropic conductive connector excellent in connection resistance and connection reliability can be obtained by the following composition. That is, the present invention has been completed. In other words, the anisotropic conductive connector according to claim 1 includes a printed wiring board (PC board) and a flexible printed wiring board (F
(PC board) electrically connected to each other, and the anisotropic conductive connector is electrically insulated by a binder resin in an in-plane direction and conductive by metal particles in a thickness direction. The metal particles are copper alloy particles that form an alloy with the solder layer of the connection terminal of the FPC board.

Further, in the anisotropically conductive connector according to claim 2, in the anisotropically conductive connector according to claim 1, the copper alloy particles have a general formula AgxCuy (0.01 ≦ x ≦ 0.4, 0 .
6 ≦ y ≦ 0.99 (atomic ratio)), and the silver concentration on the surface of the particle is higher than the average silver concentration of the particle. The method for connecting an anisotropic conductive connector according to claim 3 is the method for connecting an anisotropic conductive connector according to claim 1 or 2, wherein the anisotropic conductive connector is an anisotropic conductive adhesive film. The connection is made via

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION As a flexible printed wiring board used in the present invention, if connection terminals corresponding to a wiring pattern of a wiring board to be connected are formed and a solder alloy layer is formed on the connection terminal surface, Any structure or material is acceptable. The material of the base film is preferably polyimide from the viewpoint of heat resistance. The thickness of the base film should be 20 μm in order to obtain sufficient strength.
m or more, more preferably 25 μm or more. The structure of the flexible printed wiring board may be a single-sided structure or a double-sided structure, but a structure with a coverlay is preferred.

The material of the connection terminals of the flexible printed wiring board may be any metal material depending on the required electric resistance value, but is preferably copper in terms of electric resistance value. The solder alloy layer on the connection terminal surface of the flexible printed wiring board can be formed by, for example, electrolytic solder plating, electroless solder plating, solder leveler, vapor deposition, sputtering, or the like. From the viewpoint of smoothness, it is preferable to form by a solder plating method or a vapor deposition method. The solder alloy is not particularly limited as long as it forms an alloy with the copper alloy particles of the connection portion, but preferably contains at least tin and has a melting point of less than 350 ° C.,
It is particularly preferable that the melting point is 200 ° C. or lower. The aforementioned solder alloy layer preferably has a thickness of 0.1 to 10 μm,
Particularly preferred is 0.5 to 3 μm. The thickness of the connection terminal is 1
0 μm to 35 μm or more, preferably 15 μm to 20 μm
Is particularly preferred.

The material of the printed wiring board used in the present invention may be, for example, an insulating resin such as an epoxy resin, a polyimide resin, a polyphenylene ether resin, a fluororesin, a polyamide resin alone, or a glass cloth, a glass nonwoven fabric, or an aramid nonwoven fabric. Can be used as a composite material. As a wiring material of the wiring board, a metal is preferable in terms of an electric resistance value, and copper is particularly preferable. Nickel plating or gold plating may be performed to prevent oxidation of the wiring surface. It is also possible to form a solder alloy layer.

As the thermosetting resin used for the anisotropic conductive connector used in the present invention, an epoxy resin is preferable. The epoxy resin is a compound having two or more epoxy groups in one molecule, specifically, a compound having a glycidyl ether group, a glycidyl ester group, a glycidylamine group, an alicyclic epoxy group, and a substituent thereof. Is a compound having two or more kinds of As the curing agent for the epoxy resin, an acid anhydride-based, amine-based, or cationic curing agent can be used, but an amine-based curing agent having a high curing speed is preferred. Among them, a microencapsulated amine-based curing agent is particularly preferred.

The above-described anisotropic conductive connector may be mixed with a thermoplastic resin in addition to the thermosetting resin. As the thermoplastic resin in this case, phenoxy resin, polyvinyl acetal resin, polyvinyl butyral resin, alkylated cellulose resin, polyester resin, acrylic resin,
Urethane resin and the like. The copper alloy particles used for the anisotropic conductive connector of the present invention are preferably spherical, and the particle diameter is preferably 0.1 to 20 μm. If the particle size is too small, the connection is likely to be unstable, affected by variations in the surface roughness of the terminals.If the particle size is too large,
Short circuits between adjacent terminals are likely to occur.

The compounding amount of the copper alloy particles in the anisotropic conductive connector is preferably in a range where conduction in the connection direction is possible while ensuring insulation between adjacent terminals. Preferably, it is in the range of 0.03 to 20% by volume, more preferably 0.1 to 10% by volume, based on the resin component in the anisotropic conductive connector. As elements other than copper contained in the copper alloy particles,
Silver, gold, palladium, platinum and the like can be used,
Silver is preferred. When the copper alloy particles have the general formula AgxCuy (0.
01 ≦ x ≦ 0.4, 0.6 ≦ y ≦ 0.99 (atomic ratio)
When the silver concentration on the particle surface is higher than the average silver concentration of the particles, it is easy to form an alloy with the solder alloy layer on the connection terminal surface of the flexible printed circuit board, and the connection resistance and the connection reliability are good. Is particularly preferred because

As a method for producing the copper alloy particles, it is preferable to produce the particles by an inert gas atomizing method because spherical particles are easily obtained and oxides on the surface are reduced. The silver concentration at the surface and near the surface of the copper alloy particles was XPS (X
Line photoelectron spectroscopy analyzer). The average silver concentration can be measured by dissolving copper alloy particles in concentrated nitric acid and using IPC (high frequency inductively coupled plasma emission spectrometer). The copper alloy particles are characterized in that the silver concentration on the particle surface is higher than the average concentration, but it is preferable that the silver concentration on the particle surface is 1.4 times or more the average silver concentration.

[0015] The method for connecting an anisotropic conductive connecting body of the present invention comprises:
A method in which the anisotropic conductive connection layer is formed in a film shape in advance and thermocompression bonding, a method in which a paste is formed and thermocompression bonding can be used, etc. Is preferred. In this case, the anisotropic conductive connector formed in a sheet shape is a printed wiring board,
Alternatively, a method of temporarily crimping the connection terminals on the flexible printed wiring board, and then performing the final crimping after the alignment can be used. Since the solder alloy layer on the surface of the connection terminal of the flexible printed wiring board and the copper alloy particles at the connection portion easily form an alloy, the anisotropic conductive connection layer film is temporarily pressure-bonded onto the connection terminal of the flexible printed wiring board, After the alignment, a method of performing full pressure bonding is preferable.

Hereinafter, the present invention will be specifically described based on examples. (Production method of copper alloy particles) Copper alloy particles were obtained by the following method. 720 g of copper powder (purity 99.99%) and silver powder (purity 9
(9.99%), 180 g were mixed, put in a graphite crucible (with a boron nitride nozzle), melted by high frequency induction heating in a nitrogen atmosphere, and heated to 1700 ° C. This melt was jetted out of the nozzle for 30 seconds under helium atmospheric pressure. At the same time, 4.2 m ³ (volume at 25 ° C., 1 atm) of helium gas in a cylinder (cylinder pressure 150 atm) was jetted from a peripheral nozzle toward the jetting melt. Observation of the obtained powder with a scanning electron microscope revealed that the powder was spherical.
(Average particle size: 19.3 μm) As a result of analyzing the silver concentration of the particles by XPS, Ag / (Ag + Cu) (atomic ratio)
Was 0.47. Further, the particles are dissolved in concentrated nitric acid,
The average silver concentration measured by PC was 0.13. Therefore, the silver concentration on the surface of the copper alloy particles was 3.6 times the average silver concentration. A part of the obtained copper alloy particles having a particle size of 10 μm or less was taken out by an airflow classifier and used in Examples. (Average particle size 6.1 μm)

[0017]

Example 1 50 g of a bisphenol A type epoxy resin (epoxy equivalent: 960) and 50 g of a phenoxy resin having an average molecular weight of 25,000 were mixed with a mixed solvent of toluene-ethyl acetate (1).
(Weight ratio: 1, weight ratio) to give a solution having a solid content of 50%.
The resin component 100 and the microencapsulated amine-based curing agent 30 were blended in a solid weight ratio, and the above-mentioned copper alloy particles were blended and dispersed at 3% by volume. Then, it applied on the 100-micrometer-thick polyethylene terephthalate film, and was air-dried at 70 degreeC, and the 30-micrometer-thick anisotropic conductive film was obtained.

Wiring width 100 μm, wiring pitch 200 μ
m, a flexible printed wiring board having 200 circuits of eutectic solder plating of 2.0 μm on copper wiring of 18 μm thickness (material: polyimide resin, thickness 25 μm, cover lay film of polyimide resin 25 μm except for connecting parts) The above-mentioned anisotropic conductive film is temporarily attached on the connection terminal portion of (attached), and using a crimping head having a width of 2.5 mm,
After pressing at 70 ° C. and 0.5 MPa for 3 seconds, the polyethylene terephthalate film is peeled off. Wiring width 100
Anisotropic conduction on a connection circuit of a printed circuit board (material: glass epoxy board, 1.6 mm thick) having 200 circuits with 0.3 μm gold plating on copper wiring with a wiring pitch of 200 μm and a wiring pitch of 200 μm and a thickness of 18 μm. After aligning the connection terminals of the flexible printed wiring board to which the functional film is temporarily attached, and temporarily connecting them, 170 ° C., 20 seconds, 3.0M
Anisotropically conductive connectors were obtained by pressure bonding with Pa.

The resistance value between the connection terminals was measured with a four-terminal resistance meter, and the average value was found to be 212.0 mΩ. After holding the anisotropic conductive connector in a hot air dryer at 120 ° C. for 1000 hours, the resistance value was measured in the same manner, and it was 220.0 mΩ. An anisotropic conductive connector was prepared in the same manner as described above, the connection was peeled off, and the surface of the connection of the copper alloy particles was measured with an EDX (energy dispersive X-ray analyzer). And alloys of tin and silver were detected.

[0020]

Example 2 Anisotropically conductive connection was carried out in exactly the same manner as in Example 1 except that the solder layer on the connection terminal of the flexible printed wiring board was a solder containing 2% by weight of silver instead of eutectic solder. I got a body. The resistance value between the connection terminals was measured by a four-terminal resistance meter, and the average value was determined.
mΩ. After keeping the anisotropic conductive connector in a hot air dryer at 120 ° C. for 1000 hours, the resistance was measured in the same manner, and it was 219.2 mΩ.

An anisotropic conductive connector was prepared in the same manner as described above, the connection was peeled off, and the surface of the connection of the copper alloy particles was measured with an EDX (energy dispersive X-ray analyzer). And copper, and tin and silver alloys were detected.

[0022]

Comparative Example 1 A 0.2 μm nickel layer was provided on the surface of particles having polystyrene resin as a core instead of copper alloy particles,
An anisotropic conductive connector was obtained in exactly the same manner as in Example 1, except that conductive particles having an average particle size of 10 μm, in which a gold layer having a thickness of 0.02 μm was provided outside the nickel layer, were used. The resistance value between the connection terminals was measured by a four-terminal resistance meter, and the average value was found to be 253.3 mΩ. After keeping the anisotropic conductive connector in a hot air dryer at 120 ° C. for 1000 hours, the resistance value was measured in the same manner, and it was 5 kΩ.

[0023]

[Comparative Example 2] Instead of copper alloy particles, average single particle diameter 2μ
m, except that nickel particles having an aggregate particle size of 12 μm were used.
An anisotropic conductive connector was obtained in the same manner as in Example 1. The resistance value between the connection terminals was measured by a four-terminal resistance meter, and the average value was found to be 520.3 mΩ. After holding this anisotropic conductive connector in a hot air dryer at 120 ° C. for 1000 hours, the resistance was measured in the same manner.
It was 2 mΩ.

An anisotropically conductive connector was prepared in the same manner as described above, the connection was peeled off, and the surface of the connection of the copper alloy particles was measured with an EDX (energy dispersive X-ray analyzer). And nickel, and alloys of tin and nickel were not detected. As described above, it was shown that the connection resistance value of the example according to the present invention was lower than that of the comparative example, and that the connection resistance value after the reliability test was also lower.

[0025]

The anisotropic conductive connector according to the present invention can use a flexible printed wiring board having a wiring pattern on which an inexpensive solder alloy layer is formed instead of expensive gold plating.
In addition, the connection resistance and the connection reliability are excellent.

Claims (3)

[Claims] 1. An anisotropic conductive connection body in which a printed wiring board (PC board) and a flexible printed wiring board (FPC board) are electrically connected, and the anisotropic conductive connection body is in an in-plane direction. Is electrically insulated by a binder resin, and is electrically conductive by metal particles in the thickness direction.
An anisotropically conductive connector comprising copper alloy particles formed of an alloy with a solder layer of a connection terminal of a substrate. 2. The anisotropically conductive connector according to claim 1, wherein the copper alloy particles have a general formula of AgxCuy (0.01 ≦
x ≦ 0.4, 0.6 ≦ y ≦ 0.99 (atomic ratio), wherein the silver concentration on the surface of the particles is higher than the average silver concentration of the particles. . 3. An anisotropically conductive connection body according to claim 1, wherein said anisotropically conductive connection body is connected via an anisotropically conductive adhesive film. Connection method of the sexual connection body.