JP2003247083A - Conductive fine particle with flux, and conductive connecting structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive fine particle having flux requiring neither a flux-coating step nor its cleaning step in inter-electrode connection and to provide a conductive connecting structure using the same. <P>SOLUTION: The conductive fine particle obtained by forming at least one or more metal layers on the surface of a fine particle as a base material and then allowing flux-containing microcapsules to adhere to the outer side of the resultant conductive fine particle is used. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive particle with a flux used for connecting electrodes and a conductive connection structure using the same.

[0002]

2. Description of the Related Art Conventionally, in electronic circuit boards, ICs and L
Electrodes of semiconductor products such as SI are connected to opposing electrodes via conductive fine particles such as solder balls. Contact resistance of these electrodes may be increased due to dirt such as oil and fat or an oxide film, and when it is desired to reduce the contact resistance, a flux is applied to the electrodes to clean the electrode surface, if necessary. The metal on the electrode surface was reduced to reduce the contact resistance, and then the conductive fine particles were arranged to connect the electrodes. Further, by applying the flux, it is possible to promote the wetting of the solder, the heat conduction during the solder reflow, and the reoxidation of the electrodes.

However, the flux applied to the electrodes is not necessary after the electrodes are connected, and the excess flux attached to the portions other than the electrodes may cause various harmful effects. Therefore, the flux is cleaned and removed. There was a need. Therefore, there is a problem that an additional step for cleaning the flux is required and an organic solvent must be used in the cleaning step.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and its purpose is to eliminate the need for a flux applying step and a cleaning step in connecting electrodes. Conductive particles with flux,
And to provide a conductive connection structure using the same.

[0005]

The conductive fine particles with a flux of the present invention have a microcapsule containing a flux on the outside of the conductive fine particles having at least one metal layer formed on the surface of the base fine particles. It is characterized by being fixed.

The present invention will be described in detail below. The base fine particles used in the present invention are not particularly limited, and examples thereof include those made of synthetic resin, metal and the like. Examples of the synthetic resin include styrene homopolymer, styrene copolymer, acrylic ester polymer, phenol resin, polyester resin, vinyl chloride resin and the like. Examples of the metal include high melting point metals such as silver, copper, nickel, silicon, gold, and titanium. Of these, base fine particles made of synthetic resin are preferably used. The shape of the base fine particles is preferably spherical, and may be hollow as long as they are spherical.

The average particle size of the base fine particles is 1 to 100.
0 μm is preferable. If the average particle diameter is smaller than 1 μm, the particle diameter of the obtained conductive fine particles is too small, so that it becomes difficult to obtain a good connection when used between electrodes.
If it is larger than 0 μm, it becomes impossible to satisfy the demand for narrow pitch connection, which has been particularly remarkable in recent years.

As the conductive fine particles according to the present invention, those having at least one metal layer formed on the surface of the base fine particles are used. As the metal used for the metal layer, for example, gold, silver, copper, platinum, zinc, iron, tin, aluminum, cobalt, indium, nickel, chromium,
Examples thereof include titanium, antimony, bismuth, germanium, cadmium and silicon. The metal layer may be formed of any one of these metals or an alloy composed of two or more of these metals.

The method for forming the metal layer on the surface of the base fine particles is, for example, a method by electroless plating; a method by electroplating; a method of coating fine metal powder on the fine base particles; A method of coating the paste obtained on the fine particles of the substrate; a method such as vacuum deposition, ion plating, or ion sputtering can be used.

In order to improve the adhesion between the metal layer and the fine particles of the base material, a metal underlayer may be previously provided on the surface of the fine particles of the base material.

The thickness of the above-mentioned metal layer is not particularly limited, but in consideration of applications such as conductive bonding and substrate bonding, it is 0.0
It is preferably 1 to 500 μm. When the thickness of the metal layer is less than 0.01 μm, good conductivity cannot be obtained, and when it exceeds 500 μm, the conductive fine particles are fused with each other, the distance between the substrates is maintained, and the circuit is added between the substrates. The function to relieve stress may be insufficient.

The outermost layer of the metal layer is preferably formed of tin or a tin-based alloy layer. The alloy layer is preferably formed by adding one or more metals selected from silver, copper, zinc, bismuth, indium, lead and antimony to tin as a base.

The conductive fine particles with a flux of the present invention are
A microcapsule containing a flux is fixed to the surface of the conductive fine particles. The microcapsules used for encapsulating the flux are not particularly limited as long as they can be destroyed by the pressure when connecting the conductive fine particles between the electrodes. As the material of the microcapsules, for example, vinyl chloride resin, acrylic resin, acrylic ester / acrylonitrile resin, melamine resin, styrene / divinylbenzene resin, etc. are used.

As a method of obtaining the microcapsules containing the above-mentioned flux, for example, a method of polymerizing a monomer of a synthetic resin forming the microcapsules in a medium in which the flux is dispersed can be mentioned.

Examples of the flux include commercially available rosin flux, stearic acid, adipic acid,
Examples thereof include a flux containing a carboxylic acid such as anthranilic acid, lauric acid, glycolic acid, azelaic acid, succinic acid and sebacic acid as a main component. Among them, the flux containing carboxylic acid as a main component is preferable because it can be deactivated by heating and need not be removed by washing.

The method for fixing the microcapsules containing the above-mentioned flux to the surface of the conductive fine particles is not particularly limited, and for example, by applying an adhesive to the surface of the microcapsules in advance and then mixing with the conductive fine particles, A method of adhering the capsule to the surface of the conductive fine particles can be mentioned. In addition, a hot-melt adhesive is applied to the surface of the microcapsules containing the flux in advance and then mixed with conductive fine particles, and the mixture is stirred while being heated to a temperature above the temperature at which the hot-melt adhesive is activated. A method of firmly adhering to the surface of the fine particles can be mentioned. Further, if a resin that exhibits tackiness upon heating is used as the material of the microcapsules, it can be adhered to the surface of the base particle without using an adhesive.

The size and number of the microcapsules adhered to the surface of the conductive fine particles are appropriately determined by the required amount of flux, and the amount of the flux is determined by the particle size of the conductive fine particles, the application, and the like.

When a conductive connection structure is obtained using the above conductive fine particles with flux, for example, the conductive fine particles with flux are directly placed between the electrodes, and the microcapsules are destroyed by applying pressure. After flowing the flux over the electrodes, the metal layers may be melted by heating to connect the electrodes to each other, and an anisotropic conductive sheet obtained by kneading conductive fine particles into a resin sheet or the like may be placed between the electrodes. The electrodes may be connected to each other.

The conductive fine particles with a flux of the present invention are
For example, solder balls such as BGA (ball grid array) and CSP (chip size package) for connecting IC, LSI and the like on a substrate; anisotropic conductive sheet for inspecting circuits of semiconductor products such as IC and LSI; It can be suitably used for anisotropic conductive adhesives and the like.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to the following examples and comparative examples. (Example) Base metal fine particles (average particle size of about 700 μm) made of a copolymer of styrene and divinylbenzene were plated with nickel as a conductive underlayer, and then copper was plated by an electrolytic plating method to form a metal layer. Formed. Further, tin / silver plating was applied thereon to obtain conductive fine particles having the alloy layer formed thereon. On the other hand, in an aqueous dispersion liquid in which sebacic acid is dispersed, ethyl acrylate, acrylonitrile and methacrylonitrile are copolymerized by suspension polymerization to contain sebacic acid as a flux, and a microcapsule having an average particle size of about 15 μm. Was produced.

After applying a hot melt adhesive to the surface of the microcapsules by using a spray device, the microcapsules are heated to 100 ° C. and mixed with the plated conductive fine particles, and the flux is applied to the surface of the conductive fine particles. The microcapsules encapsulating were fixed to obtain conductive particles with flux. When the obtained conductive fine particles with flux were observed by an electron microscope, the microcapsules were uniformly adhered to the surface.

[0022]

The conductive fine particles with a flux and the conductive connecting structure of the present invention are configured as described above, and the flux applying step and the washing step are completely unnecessary. Therefore, the electrode connecting step can be shortened. You can Further, since it is not necessary to wash the flux, the working environment is not deteriorated in the electrode connecting step.

Claims (4)

[Claims] 1. A conductive fine particle with a flux, characterized in that a microcapsule containing a flux is fixed to the outside of the conductive fine particle having at least one metal layer formed on the surface of the base fine particle. . 2. The conductive fine particles with a flux according to claim 1, wherein the flux is composed of a component which is deactivated by heating. 3. The conductive fine particles with a flux according to claim 1, wherein the microcapsules are fixed to the outside of the conductive fine particles via a hot melt adhesive. 4. A conductive connection structure, which is connected by the conductive fine particles with a flux according to claim 1.