KR100241589B1 - Anisotropic conductive film - Google Patents

Abstract

Many of the anisotropic conductive films produced by using a mixture of metal powder particles having a small particle diameter and a large hardness and metal coated metal particles coated with a metal thin film on the surface of the metal particle having a large particle diameter and low hardness as conductive particles in the insulating adhesive. It is an excellent anisotropic conductive film in which the connection thickness between the fine circuits is constant, the variation in the connection resistance value between the connection circuits is extremely small, and shows high connection reliability.

Description

Anisotropic conductive film

[TECHNICAL FIELD OF THE INVENTION]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to anisotropic conductive films used for the electrical connection of fine circuit boards, in particular the connection of LCDs (liquid crystal displays) and flexible circuit boards (FPCs), micro bonding and tapping of semiconductor ICs and IC mounting circuit boards. In detail, the connection thickness is constant by using a metal particle having a large particle size, a low hardness, a low melting point, a high melting point, and a high hardness. This invention relates to an anisotropic conductive film having a small distribution of variation in connection resistance between connection terminals, high connection reliability, and excellent weather resistance.

[Private Technology]

With the recent trend of miniaturization and thinning of electronic devices, the necessity of the connection of the microcircuit board, the connection of the micro part and the microcircuit, etc. is increased. Films have been developed and started to be used.

Such anisotropic conductive film is thermally crimped under constant temperature, constant pressure and constant time by inserting an adhesive or film containing a predetermined amount of conductive metal particles having a small particle size between the circuits to be connected to each other to perform electrical connection between circuits, and to insulate between adjacent circuits. It has been used to maintain. This will be described in more detail with reference to FIG. 3 as follows. 3 is a view showing a simple connection between a liquid crystal display substrate and a driving integrated circuit (a kind of tab (TAB)) using an anisotropic conductive film to a liquid crystal display device. The application method thereof is a film-type thermosetting resin or thermoplastic resin. The anisotropic conductive film which disperse | distributed the electroconductive particle 6 about 10 micrometers in diameter was sandwiched in resin 1 between the glass substrate 7 of a liquid crystal display substrate, and the electrodes 9 and 10 of the tab 8, and this state After heating the anisotropic conductive film at a predetermined temperature in the glass substrate 7 and the tab (8) by pressing the thermosetting resin or thermoplastic resin (1) as shown in Figure 4 the glass substrate 7 and the tab 8 Filled in the space between the electrodes, and an electrically conductive passage between the electrodes 9 and 10 is provided by the conductive particles 6.

However, with the trend toward miniaturization and thinning of electronic devices, the demand for microcircuits increases, the number of pitches between electric circuits increases, the number of circuit pins increases, and the spacing between circuit pins decreases. As it decreases, the number of the conductive particles 6 sandwiched in the polarization 9 and 10 and the size of the particles also decrease. However, in the case of manufacturing a miniaturized and thinned electronic device, for example, a liquid crystal display device using small conductive particles in a conventional anisotropic conductive film, the liquid crystal display substrate and the tab are not securely connected to each other. As a result, connection failure 12 is caused. As a method for solving such a problem, there is a method of increasing the quantity of the conductive particles dispersed in the thermosetting resin or the thermoplastic resin 1, but this is likely to cause a short circuit between the electrodes as shown in FIG. In addition, it is difficult to control the connection thickness with high reliability due to the connection operation by thermocompression, nonuniformity occurs in the connection thickness between a plurality of circuits, causing a difference in the connection resistance value in the plurality of circuit terminals, and worsening the connection reliability. There is this.

Recently, in order to improve the connection reliability by increasing the contact area with a circuit even under the influence of expansion and contraction effects on temperature change, a technique using conductive particles in which a metal thin film is coated on a polymer material instead of conductive metal particles has been used. Developed. However, it is difficult to control highly reliable connection thickness by the connection operation by thermocompression bonding, and also the electroconductive particle which coat | covered the metal thin film in such a polymeric material, and the nonuniformity also arises in the connection thickness between many circuits, Therefore, there is still a problem that a difference occurs in the connection resistance value and the connection reliability deteriorates.

The present invention has been made to solve the problems of the prior art as described above, an object of the present invention is to provide an anisotropic conductive film having a constant connection thickness between the first fine circuit, and secondly between the connection circuit even under the change of temperature and humidity An object of the present invention is to provide an anisotropic conductive film having a small variation in connection resistance, and to provide an anisotropic conductive film having a high third connection reliability.

1 is a schematic cross-sectional view of an anisotropic conductive film according to an embodiment of the present invention,

2 is a schematic cross-sectional view of a circuit board in which an anisotropic conductive film is applied according to an embodiment of the present invention.

3 is a schematic exploded cross-sectional view of a circuit board to which a conventional anisotropic conductive film is applied.

4 is a schematic cross-sectional view of a circuit board in which an anisotropic conductive film according to FIG. 3 is applied.

* Explanation of symbols for main parts of the drawings

1: adhesive resin 2: high hardness, high melting point conductive particles

3: low hardness low melting point conductive particles 4: high hardness high melting point metal layer

6: conductive particle 7: liquid crystal display substrate

8: tab 9: electrode of liquid crystal display substrate

10: tap electrode 11: electrical short

12: Poor connection

In order to achieve the object of the present invention as described above, the present invention is an anisotropic conductive film comprising a release film and a conductive layer comprising an insulating adhesive and conductive particles on the release film, wherein the conductive particles (a) particle size is 7 A first metal particle selected from the group consisting of gold, silver, iron, copper, nickel, cadmium, bismuth, indium, aluminum, palladium, and mixtures thereof; And (b) from the group consisting of bismuth-tin-lead alloys, bismuth-tin-zinc alloys, tin-lead alloys, tin-zinc alloys, tin-antimony alloys, tin-silver alloys, copper-zinc alloys and mixtures thereof Coating a metal thin film on the surface of the selected metal particles, wherein the size of the coated metal particles has a radius of 20 to 40% greater than that of the first metal particles; It provides an anisotropic conductive film comprising a.

In the present invention described above, the conductive particles are preferably added in an amount of 5 to 10% by volume with respect to the adhesive, and a deviation of the particle diameter in the particle size distribution is preferably ± 0.2 μm.

In the present invention, it is preferable that the first metal particles and the second metal particles coated with the metal thin film have a radius difference of 20 to 40%.

In addition, in the present invention, the material of the second metal particles having a large particle size is bismuth-tin-lead alloy, bismuth-tin-zinc alloy, tin-lead alloy, tin-zinc alloy, tin-antimony alloy, tin- Preference is given to using those selected from the group consisting of silver alloys, silver-zinc alloys, copper-zinc alloys, and mixtures of two or more thereof.

EXAMPLE

An example of the present invention will be described in more detail with reference to FIGS. 1 and 2 as follows.

The present invention is made by dispersing 5 to 10% by volume of conductive particles in a thermosetting resin or a thermoplastic resin component in an insulating adhesive, the conductive particles having two kinds of particle diameters, in the particle size distribution in the range of particle diameter ± 0.2μm. It is preferable. In addition, the above two kinds of particles are preferably metal powder having a difference in radius in the range of 20 to 50%. The metal particles 2 having a small particle radius are metal particles having a high hardness and a high melting point, and the metal particles having a large particle diameter are smaller in hardness than the metal particles having a small particle diameter and are conductive to an alloy 3 having a lower melting point. It is a conductive particle made of metal (4) which is excellent in melting point and has a higher hardness than the alloy.

1 is a cross-sectional view of the anisotropic conductive film according to the present invention. In this anisotropic conductive film, the metal particles 2 having a small particle radius are metal particles having a high hardness and a high melting point, and the metal particles having a large particle diameter have an alloy having a lower melting point and a lower melting point than metal particles having a small particle diameter (3). Coated liquid solution formed by dispersing a predetermined amount of conductive particles in the insulating adhesive 1 onto two types of conductive particles made of metal (4) having excellent body conductivity, high melting point, and much higher hardness than the alloy. It dries and shape | molds to the film form of 20-150 micrometers or less. The metal conductive particles 2 having a small particle size are preferably metals having a value higher than twice as high as the Knoop value in hardness compared to the alloy material 3 of the conductive particles having a large particle size. In addition, each conductive particle is preferably used metal particles and metal matrix alloy particles having a uniform particle size distribution having a particle size deviation within ± 0.2 μm of their respective particle diameters.

Metal particles with high hardness determine the connection thickness during the heating pressurization.Conductive particles with a large particle diameter have a high hardness due to the heating pressurization and the height decreases as the connection area increases to the connection thickness provided by the small particles. As shown in the figure, high connection reliability is provided and a wide connection area also serves to reduce connection resistance.

2 is a cross-sectional view illustrating an example of a connection state of a circuit by applying an anisotropic conductive film to a circuit board according to an embodiment of the present invention. As can be seen from this figure, the conductive particles having a high hardness connected by thermocompression determine the connection thickness, and there is a height variation between the terminals, and as shown in FIG. 4, small metal particles provide a conductive passage. It can be seen that even in a situation in which a poor connection can occur, a large particle can provide a connection conductive path through deformation as much as its height.

Particle size is small and the hardness is shown a strain of less than 5% at a pressure of high metal particle (2) is a metal or the like to connect between the circuit by the anisotropic conductive film thermocompression bonding conditions 100~200 ℃, 5.0Kg / cm ² The material is particularly preferably selected from the group consisting of the above-mentioned gold, silver, iron, copper, nickel, cadmium, bismuth, indium, aluminum, palladium and mixtures thereof. And these particle diameters are preferable 7-15 micrometers which is the level which ensures the insulation between the circuits to connect, and the reliability of a connection.

In addition, alloys of the conductive particles 3 having low hardness include bismuth-tin-lead alloys, bismuth-tin-zinc alloys, tin-lead alloys, tin-zinc alloys, tin-antimony alloys, tin-silver alloys, and silver-zinc. An alloy, a copper-zinc alloy, or the like may be used, and the particle size may be about 1.5 to 2.5 times as large as that of the conductive particles 2 by a meticulous treatment. Metals that can be used for bait treatment include nickel, aluminum, cadmium, palladium and indium.

The kind of the metal foil layer 4 coated on the alloy 3 is nickel, aluminum, cadmium, palladium, indium and the like which are relatively stable to oxidation and the like, and it is easy to obtain a coating layer having a uniform thickness by the electroless plating method. The coating insect is preferably 0.1 to 1.5 µm, more preferably 0.2 to 0.8 µm. If the thickness of the above-mentioned covering insect is less than 0.2 µm, the conductivity is lowered, and if it exceeds 1.5 µm, the hardness of the deformable particles is affected and deformation does not occur easily.

In addition, it is preferable to add 10-50 volume%, More preferably, 10-20 volume% of the electrically-conductive particle 2 with a small particle diameter in all electroconductive particle mix | blending. If the addition amount of the conductive particles 2 is less than 10% by volume, it is difficult for the circuit terminal and the connection area to obtain a sufficient control thickness control effect, and when the amount of the conductive particles 2 exceeds 50% by volume, the circuit terminal and the connection area are lowered and the connection resistance value is reduced. It becomes high and reliability falls.

As for the compounding quantity of electroconductive particle with respect to the thermosetting resin or thermoplastic resin which is an insulating adhesive agent, 5-10 volume% is preferable. If the amount of the conductive particles is less than 5% by volume, it is difficult to obtain a stable conductive path, and when it exceeds 10% by volume, it is difficult to obtain insulation reliability between the connection circuits.

As the adhesive adhesive polymer resin 1 used in the present invention, thermoplastic, thermosetting, or photocurable resins exhibiting insulating properties can be used. As an example, styrene-butadiene resin, styrene resin, ethylene-vinyl resin, acrylonitrile butadiene rubber, silicone resin, acrylic resin, epoxy resin, urethane resin, phenol resin, amide resin, acrylate resin, etc. may be appropriately selected and used. Therefore, you may use together 2 or more types of resin as needed. Moreover, if necessary, a tackifier, a crosslinking agent, an anti-aging agent, a coupling agent, etc. which are represented by rosin, a turbine resin, a gumarodine resin, etc. can also be used.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the following examples are merely examples of the present invention and the present invention is not limited to the following examples.

[Examples 1-3]

An adhesive solution was prepared by dissolving 100 parts by weight of epoxy-based thermoplastic resin (YD-128, Kukdo Chemical), 60 parts by weight of rubber modified epoxy (KR-208, Kukdo Chemical), and 20 parts by weight of phenol resin. In the solution, conductive particles obtained by electroless bonding method of nickel particles having a particle diameter of 10 ± 0.2 μm (only Daeju Fine Chemicals) and a tin-zinc alloy material having a particle diameter of 13.0 ± 0.2 μm with a thick film of 0.3 μm by electroless bonding method, were used for the resin solid content. 7 volume% was mixed and dispersed. In addition, anisotropic conductive films were prepared while changing the conductive particles having a large particle diameter, that is, the conductive particles made of tin-zinc alloy to 30, 50, and 70% by weight based on the total particle amount. Using this, a flexible circuit board (FPC) having a line width of 0.1 mm, a pitch of 0.2 mm, and a thick film of 35 μm terminal number of 160 copper circuits and a transparent conductive circuit glass substrate (ITO circuit) were connected by thermocompression bonding.

The connection resistance value was measured by the four-terminal method (Four Probe Method) after the initial connection and after leaving the high temperature and high humidity, and the adhesive force was obtained by the peel tester. The results are shown in Table 1 below.

As a result of the measurement, the control effect of the connection thickness was excellent, and the reliability of the connection resistance value between the connection terminals was also excellent.

Comparative Example 1

An FPC and an ITO circuit of the same form were connected to the same adhesive solution as Examples 1-3 using an anisotropic conductive film prepared by mixing nickel particles having an average particle diameter of 8 m, a maximum particle diameter of 18 m, and a minimum particle diameter of 2 μm as conductive particles. Evaluated. The results are shown in Table 1 below.

As a result of the measurement, the variation in connection thickness was severe as compared with Examples 1 to 3, and the connection resistance value after the high temperature and high humidity test was increased.

Comparative Example 2

As the conductive particles, anisotropic conductive films prepared by using a conductive particle coated with nickel metal particles with an electroless bonding method on melamine resin polymer particles having an average particle diameter of 12 μm, a maximum particle diameter of 23 μm, and a minimum particle diameter of 5 μm, and the same as in Examples 1 to 3 A comparison was made with the form. The results are shown in Table 1 below.

As a result of the measurement, the effect of the connection thickness was shown slightly, and the initial resistance value was lowered, but the connection resistance skin increased after the high temperature and high humidity test.

[Examples 4 to 6]

An adhesive solution was prepared by mixing 100 parts by weight of an epoxy-based thermoplastic resin (YD-208, Kukdo Chemical), 60 parts by weight of a rubber-modified epoxy resin (KR-128), and 20 parts by weight of a phenol resin. Resin solids were obtained by conducting the electrolytic particles obtained by electrolessly depositing a thick film of 0.3 μm of nickel with silver particles having a particle size of 8 ± 0.2 μm (from Daeju Fine Chemicals) and a silver-tin alloy having a particle size of 13.0 ± 0.2 μm. 7 vol% of the mixture was mixed and dispersed. In addition, anisotropic conductive films were prepared while changing conductive particles having a large particle diameter, that is, conductive particles obtained by subjecting nickel-tin to the material to 50, 60, 70, 80, 90, and 100% by weight based on the total particle amount. By using this, a flexible circuit board (FPC) having a line width of 0.1 mm, a pitch of 0.2 mm, a thick film of 35 μm, and 160 copper circuits and a transparent conductive circuit glass substrate (ITO circuit) were connected by thermocompression bonding.

The connection resistance value was measured by the four-terminal method (Four Probe Method) after the initial connection and the high temperature and high humidity, respectively, and the adhesion was obtained by the peel tester. The results are shown in Table 1 below.

Table 1 shows the results of the above examples and comparative examples.

As described above, the anisotropic conductive film of the embodiment made by using two kinds of conductive particles having different hardness and particle size in accordance with the present invention, compared to the anisotropic conductive film produced according to the comparative example of the conventional manufacturing method, It is an excellent anisotropic conductive film having a constant connection thickness between a plurality of microcircuits, a very small variation in the connection resistance value between the connection circuits, and showing high connection reliability.

Claims (2)

In an anisotropic conductive film comprising a release film and a conductive layer comprising an insulating adhesive and conductive particles on the release film, the conductive particles (a) have a particle diameter of 7 to 15 μm, and include gold, silver, iron, copper, nickel, First metal particles selected from the group consisting of cadmium, bismuth, indium, aluminum, palladium and mixtures thereof; And (b) from the group consisting of bismuth-tin-lead alloys, bismuth-tin-zinc alloys, tin-lead alloys, tin-zinc alloys, tin-antimony alloys, tin-silver alloys, copper-zinc alloys and mixtures thereof Coating a metal thin film on the surface of the selected metal particles, wherein the size of the coated metal particles has a radius of 20 to 40% greater than that of the first metal particles; Anisotropic conductive film comprising a. The anisotropic conductive film according to claim 1, wherein the conductive particles are added in an amount of 5 to 10% by volume with respect to the adhesive, and the variation in particle size in the particle size distribution is ± 0.2 μm.