JPH0750104A - Conductive particle and connection member using conductive particle - Google Patents

Abstract

PURPOSE:To provide conductive particles having no necessity to strictly control connecting conditions, excellent in connecting reliability and possible to control its deformability and a connecting member using the conductive particles. CONSTITUTION:A conductive particle has a soft layer formed on the surface of a hard core 1 and a conductive layer 3 formed outside thereof, and a connecting member is constructed by dispersing the conductive particles into adhesive components such as epoxy resin. A resin layer 4 fusible under connecting conditions may be formed outside the conductive layer 3. Material for the hard core 1 may be metallic or polymeric base. The hard core 1 is relatively harder than the soft layer 2 under circumstances where the conductive particles are used such as under connecting conditions in electrode or circuit connecting use.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to conductive particles suitable for connecting electrodes, etc., whose degree of deformation can be controlled, and a connecting member using the conductive particles.

[0002]

2. Description of the Related Art Circuit elements, circuit boards, and circuit boards are
There is an anisotropic conductive connecting member that is bonded by a connecting member in which conductive particles are dispersed in an adhesive component such as an epoxy resin to electrically connect the circuit element to the circuit board and the circuit boards to each other only in the pressing direction. In this connecting member, as the conductive particles to be dispersed in the adhesive component, there are known conductive particles in which a polymer is used as a core (polymer core) and the surface thereof is covered with a thin metal layer. . Since these particles have a small specific gravity, they are unlikely to settle when the adhesive component is liquid. Further, when using such a connecting member, for example, when connecting a microelectrode of an electronic component, the polymer core is deformed by the temperature and pressure at the time of connection, and the contact area between the conductive particles and the electrode is increased. There are features such as being able to. In this case, it is also proposed to mix hard spacer particles in order to prevent the conductive particles from being excessively deformed.

[0003]

The conductive particles formed by coating the surface of the polymer core with a thin metal layer, the deformation of the polymer core becomes large when the temperature and pressure at the time of connection increase, and The thin layer may be separated from the polymer core by being separated or partially broken, and the separated metal pieces may come into contact with the connection electrode to impair the insulation between adjacent electrodes. For this reason, it is necessary to strictly control the connection conditions, and in consideration of fluctuations in the conditions, an inspection process after connection is essential.

When mixing hard spacer particles, it is necessary to disperse the mixed particles uniformly.
Due to the difference in specific gravity and the difference in surface charge, it is difficult to uniformly disperse in a minute portion. In particular, recently, the application fields of this kind of adhesives are integrated circuits such as IC and LSI, liquid crystal and E.
It is often used as a connecting member for connecting minute electrodes and circuits such as connecting display elements such as L and plasma to electronic circuits, and therefore stable connection reliability can be obtained under a wide range of connection conditions and a large amount There is a strong demand for eliminating the inspection step after connection in production, and a connection member that is easier to use has been demanded.

[0005]

The present invention is a conductive particle in which a soft layer 2 is formed on the surface of a hard nucleus 1 and a conductive layer 3 is formed on the outer side thereof.

The present invention will be described below with reference to the drawings. Figure 1
FIG. 3A is a schematic sectional view showing an example of the present invention.
The material of the hard core 1 may be a metal or a polymer. Here, the meaning of “hard” means a relationship of relative hardness as compared with the soft layer 2 under the use environment of the conductive particles, for example, under the connection condition in the case of connecting the electrodes or circuits. A general index of hardness such as elastic modulus and hardness at a constant temperature, or a difference in thermal transformation point such as melting point, glass transition temperature and softening point can be used as a standard.

The particle size of the hard core 1 is 0.1 to 2 on average.
The thickness is preferably 0 μm, preferably 0.3 to 10 μm, and more preferably 0.5 to 6 μm from the viewpoint of reducing the distance between electrodes after connection and improving the connection reliability. The particle size of the hard core 1 is preferably uniform. Further, the grain shape of the hard core 1 is preferably substantially spherical, but as shown in (b), it may have any shape such as a large number of irregularities on the surface. The hard core 1 may be conductive or non-conductive.

Polymers such as polystyrene, nylon and various rubbers are preferable for the soft layer 2, and when these are cross-linked, solvent resistance is improved. Therefore, when a solvent is contained in the adhesive component, elution occurs. It is more preferable because it has no effect on the characteristics. If the soft layer 2 is made of a polymer, it is easy to obtain deformability, and the adhesiveness to the conductive layer and the core is good. Therefore, when it is used as a connecting member, a connection having low resistance and excellent reliability can be obtained. Also, depending on the heat resistance and hardness of the connection electrode and the substrate,
A combination can be set as appropriate.

The thickness of the soft layer 2 is preferably about 0.1 to 10 μm. If it is less than 0.1 μm, a sufficient deformation amount cannot be obtained and reliability is insufficient, and if it exceeds 10 μm, the deformation amount becomes excessive and the coating of the thin metal layer easily peels off. For this reason, 0.3 to 5 μm is preferable, and 0.5 to 3 μm is more preferable.

When the thickness of the soft layer 2 is less than or equal to the particle diameter of the hard core 1, more preferably less than 1/2, the amount of deformation of the conductive particles is easy to control, which is preferable as the material for the connecting portion of the circuit. The soft layer 2 may be present in the form of particles as shown in FIG. 1 (c), and may have a single-layer structure or a multi-layer structure or more. In the case of a structure having a plurality of layers or more, it is possible to share functions such as strength retention, solvent resistance, adhesiveness, flexibility, heat resistance, and plating solution resistance, which is preferable. The soft layer 2 can be formed by an arbitrary method such as a spraying method, a high-speed stirring method, or a spray dryer.

The conductive layer 3 is made of various conductive metals, alloys, oxides and the like. Materials preferably used in consideration of conductivity and corrosion resistance include Ni, Cu, Al and S.
n, Zn, Au, Pd, Ag, Co, Pb, and the like, and these may have a single-layer structure or a multi-layer structure or more.

The conductive layer 3 may be formed by a general method such as a vapor deposition method, a sputtering method, an ion plating method, a thermal spraying method or a plating method, but the electroless plating method is used for forming a coating layer having a uniform thickness. It is preferable because it can be obtained.

As shown in FIG. 1 (d), a resin layer 4 which can be melted under connection conditions may be formed on the surface of the conductive layer 3 if necessary. In this case, in the case of connecting the fine electrodes described above, the resin layer melts and can be connected on the contact surface with the electrode under heating and pressurization, but since the amount of heat is insufficient in the direction of the adjacent electrode, the resin layer is Since it is difficult to melt, there is little deterioration in insulation, and higher density mounting is possible.

If necessary, an auxiliary layer such as a coupling agent for improving adhesion can be formed between the above layers.

In order to use the conductive particles of the present invention for connecting fine electrodes, it is necessary to make the particle size smaller than the minimum width of the distance between adjacent wiring patterns to prevent short circuit with the adjacent wiring patterns. It is necessary to support the thinning of.

As the adhesive component in this case, a thermoplastic material may be used, but a curable material by energy of heat, light, electron beam or the like is preferably applied because it has excellent heat resistance and moisture resistance. The form may be a liquid form, a paste form, a film form, or the like, and the respective features are used to the proper use. For example, in the case of a film, it is easy to obtain a certain thickness, and a coating operation is not necessary. In the case of a liquid or paste, it can be formed only in a necessary portion of a minute area.

The proportion of conductive particles in the connecting member is
It can be set arbitrarily according to the purpose. In the case of a connecting member for a fine electrode which requires conductivity only in the thickness direction, it is 0.1 to 15% by volume, preferably 0.2 to 10% by volume, more preferably 0.5 to 6% by volume. If the compounding amount is small, the number of conductive particles on the electrodes to be connected decreases, so the reliability decreases,
If the amount is too large, the insulating property of the adjacent electrodes is deteriorated, and it becomes difficult to connect the fine electrodes.

In the case of a paint that requires conductivity in the surface direction as well 1
0-35% by volume is used.

FIG. 2 shows an electrode connecting structure of a connecting member using the conductive particles according to the present invention. Between the electrodes 13, 13 provided on the substrates 12, 12, the conductive particles 11 are connected by the connecting member 14 while being controlled by the particle size of the nucleus by heating and pressurizing at the time of connection. At this time, since the soft layer 2 on the hard core 1 is deformable, the conductive layer 3 is not peeled off. In the lateral direction of the electrode, the insulating property can be maintained by controlling the added amount of conductive particles and the particle size.

[0020]

In the conductive particles according to the present invention, the conductive layer 3 is formed on the soft layer 2, and the soft layer 2 follows deformation during connection. The maximum amount of deformation is controlled by the grain size of the nucleus 1, so that excessive deformation does not occur. Therefore, the conductive layer 3 does not peel off during the connection work.

The nucleus 1 has little or no deformation when it is heated and pressed during electrode connection so that it is harder than a soft layer, and therefore there is little deformation. Therefore, the distance between the electrodes after connection by heating and pressurization can be controlled to the particle size of the hard core, so that stable connection can be obtained even if the connection conditions are not taken into consideration. As is well known, control of the distance between electrodes has a great influence on the improvement of connection reliability.

[0022]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. Example 1 Cured epoxy particles having an average particle size of 3 μm (glass transition point 19
(0 ° C.), a coating layer having polystyrene / divinylbenzene = 100 / 0.5 (glass transition point 115 ° C.) having an average particle size of 1 μm is coated with a spray dryer using alcohol as a dispersant, and the temperature is 125 ° C. It was heated and fixed.

The particles are dispersed in water, and after a palladium chloride-based activation treatment, an electroless Ni plating solution is used to obtain Ni.
After plating was performed at 90 ° C., displacement plating was performed at 70 ° C. using an Au plating solution. The thickness of Ni / Au is 0.2 /
It was 0.02 μm.

2% by volume of the above-mentioned conductive particles was added to an adhesive component containing a high molecular weight epoxy as a main component, and a 20 μm thick layer was formed on a 50 μm thick polytetrafluoroethylene film.
m was applied to obtain a connection member. The sodium ion and the chlorine ion of the extracted water after extracting the obtained connecting member with pure water at 100 ° C. for 10 hours respectively contained 10
It was below ppm.

Sn is formed on a circuit with a thickness of 18 μm on a polyimide substrate having a thickness of 75 μm with an adhesive layer having a thickness of 15 μm interposed.
Cu circuit electrode having a thin layer and indium oxide (ITO, surface resistance 20
Ω / □) 1.5m above the connecting member between the thin layer electrode
The electrodes were placed with a width of m and the electrodes were aligned and then connected.

A circuit pitch of 100 μm and an electrode width of 50
It is a parallel circuit electrode of μm, and one test piece has 300 electrode connecting portions. The temperature of the connection is 150 ℃, 170
℃, 190 ℃, pressure 0.5MPa, 2MP
a, widely varied to 10 MPa. Under such a wide range of connection conditions, the distance between the electrodes is the average particle size of the nucleus 3
It was controlled to μm and showed good connection reliability. In addition, when observing the conductive particles in the connection part under different connection conditions with a scanning electron microscope, in all cases, minute cracks were seen in the contact part with the electrode and chrysanthemum-shaped, but the metal layer peeled off. I couldn't see it.

Comparative Example 1 Ni was directly applied to the surface of cured epoxy particles having an average particle size of 5 μm.
/ Au layer (thickness: 0.2 / 0.02 μm) was used to obtain a connecting member in the same manner as in Example 1 using conductive particles, and the same evaluation was performed. The distance between the electrodes fluctuates to 4 to 15 μm due to the variation of the connection conditions, and the variation width of the connection resistance is large. Therefore, for practical use, it was necessary to strictly control the connection conditions within a very narrow temperature and pressure range.

Example 2 Conductive Ni particles (melting point 1455 ° C.) obtained by the carbonyl method having an average particle size of 3 μm were used as nuclei, and the conductivity of the structure shown in FIG. Particles were obtained, Example 1
A connection member was obtained in the same manner as in, and the same evaluation was performed. However, the surface of the electrode was changed from Sn to a thin solder layer of Sn / Pb = 10/90.

Similar to Example 1, good connection reliability was obtained under a wide range of connection conditions, and the distance between the electrodes was controlled to 3 μm, which is the average particle size of the nucleus. In this example, the hard nuclei were made of metal particles having a high melting point, so that even if the surface of the electrode was an oxidizing substance such as solder, a good connection was obtained by cutting into the oxide layer.

Example 3 The conductive particles obtained in Example 1 were treated with a solution of nylon (glass transition point 110 ° C.) in alcohol and then dried at 60 ° C. to form a nylon layer having a thickness of 1-2 μm on the surface. 1
The conductive particles having the structure shown in (d) were obtained. The conductive particles were mixed and dispersed in the same adhesive component as in Example 1 by 6% by volume, and the same evaluation was performed below.

Also in this case, good connection reliability is obtained under a wide range of connection conditions, and the distance between the electrodes is 3 μ which is the average particle size of the nucleus.
It was controlled by m. In this example, the insulating property in the adjoining direction was good even though the content of the conductive particles was increased to 6% by volume.

Example 4 and Comparative Example 2 Using the connecting members of Example 1 and Comparative Example 1, the substrate and the connecting conditions were changed. That is, one circuit board was replaced with a glass having a thickness of 1.1 mm, and a film substrate made of polyethylene terephthalate having a thickness of 0.2 mm was used. Since the heat resistance of the film substrate is significantly different from that of glass, the connection condition was set to 130 ° C., 1 MPa, and 30 seconds, and the connection was similarly evaluated.

In the case of Example 4 (connecting member of Example 1),
The distance between the electrodes is controlled to 3 μm, which is the average particle size of the nucleus,
It showed good connection reliability. On the other hand, in the case of Comparative Example 2 (the connecting member of Comparative Example 1), cracks occurred in the ITO circuit on the film substrate.

From the comparison of the two, in the case of Example 4, since the polystyrene-based soft layer acted as an impact cushioning material at the time of connection, and in addition, the maximum deformation amount was controlled by the grain size of the hard core.
While no crack was generated in the TO circuit, in Comparative Example 2, the difference between the connection temperature and the glass transition point of the particles was large,
It is considered that cracks occurred because the hard nuclei dig into the ITO circuit on the soft film.

Therefore, by using the conductive particles and the connecting member of the present invention, in the case of so-called soft / lightweight and non-heat-resistant plastic substrates such as polyethylene phthalate, polycarbonate, polyether sulfone, polyarylate, etc. Even now it is possible to get a good connection.

[0036]

As described above in detail, according to the present invention, stable connection reliability can be obtained under a wide range of connection conditions, and it is possible to obtain conductive particles and a connection member which are easier to use.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of conductive particles according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of an electrode connection structure showing an embodiment of the present invention.

[Explanation of symbols]

 1 Hard Nucleus 2 Soft Layer 3 Conductive Layer 4 Resin Layer 11 Conductive Particles 12 Substrate 13 Electrode 14 Connection Member

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasushi Goto 1500 Ogawa, Shimodate, Ibaraki Prefecture Shimodate Laboratory, Hitachi Chemical Co., Ltd. (72) Kyohisa Ota 1500 Ogawa, Shimodate, Ibaraki Hitachi Chemical Co. Company Shimodate Institute

Claims (3)

[Claims] 1. A conductive particle having a soft layer formed on the surface of a hard nucleus and a conductive layer formed on the outer side of the soft layer. 2. The conductive particle according to claim 1, wherein a resin layer that can be melted under a connection condition is formed outside the conductive layer. 3. A connecting member containing the conductive particles of claim 1 or 2 in an adhesive component in an amount of 0.1 to 15% by volume.