JPH07771B2 - Method for producing conductive adhesive - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for producing a conductive adhesive.

BACKGROUND OF THE INVENTION In order to electrically connect an LSI chip and a printed circuit board to each other, an anisotropic adhesive containing conductive particles of metal in an insulating adhesive such as epoxy or silicon is used as a connector for both. It is considered to use a conductive adhesive). One example is shown in FIG. 1 is an LSI chip, 5 is its terminal, 2
Is a printed circuit board, 4 is its terminal, and an anisotropic conductive adhesive 3 is interposed between the terminals, and 6 is a conductive particle contained in the adhesive. In order to perform the adhesion, first, a liquid (paste-like) anisotropic conductive adhesive 3 is applied on a printed circuit board, and an LSI chip is placed on the printed circuit board in alignment with the printed terminals and supported. Therefore, an appropriate pressure is applied between the LSI chip and the printed board to heat and cure the anisotropic conductive adhesive. Ideally, it is desirable that only the corresponding terminals of the LSI chip as the printed circuit board are surely conducted through the conductive particles, and the insulation is secured in the horizontal direction (lateral direction) as seen in the figure. However, the current situation is that connection failure between terminals that should be connected and short-circuiting between terminals that should not be connected occur to the extent that they cannot be ignored. One of the reasons for this is
The dispersibility of the conductive metal particles in the adhesive may be poor. In other words, this is a phenomenon in which conductive particles concentrate in some places in the adhesive and become sparse in other places. Particles having a low specific gravity have good dispersibility, but since the conductive metal is a requirement for the material of the particles, the specific gravity is limited, and the reality is that it does not work as expected.

In order to solve this problem, the inventor of the present application considered to solve the problem by forming the particles into a multi-layer structure and forming only the outer layer (surface layer) from the conductive metal. For example, if a material having a low specific gravity is used for the inner layer, the specific gravity of the particles as a whole is reduced and the dispersibility is improved. Alternatively, an externally controllable material, for example, a material that reacts to magnetism (magnetic material) is used for the inner layer, the particles are mixed in the adhesive, and then the magnetic force is externally controlled to mix the mixed particles. It is possible to control the dispersibility by moving the particles so that the particles are evenly distributed or particles are concentrated between the terminals to be connected. However, it has been extremely difficult to produce the particles having the above-mentioned multilayer structure because the particles themselves are extremely small.

[Object of the Invention] The present invention has been made in light of the above background, and an object thereof is to easily manufacture a conductive adhesive.

[Points of the Invention] The present invention is to mix particles having a higher melting point and a smaller specific gravity than the conductive material into the conductive material and encapsulating the particles, which are wrapped in the conductive material melted from a nozzle, at room temperature. Is almost liquid, and has a specific gravity smaller than the specific gravity of the particles encased in the conductive material, and the upper portion is dropped into a liquid layer heated near the temperature at which the conductive material is melted. The gist of the present invention is to add an electroconductive substance, which is obtained by allowing the electroconductive material encapsulating the particles to be precipitated and being cooled and solidified, to the adhesive.

[Embodiment] In FIG. 1, (a) is an embodiment of the present invention and (b) is an enlarged view of a part of FIG. 1 (a). As a result, as shown in FIG. The particles 16 are manufactured to have a two-layer structure. That is, 7 is, for example, a ruby or sapphire container, and the material 8 (for example, indium and gallium liquid) of the outer layer B of the two-layer structure of FIG. 2 is contained in the container, and further, the inside of FIG. Particles A, for example, non-metals such as plastic and ferrite are mixed. A nozzle 10 is formed at the tip of the container 7 and is opened by a laser or the like. For example, a particle having a two-layer structure in which a non-metal such as plastic or ferrite is used as the particle A and a conductive metal such as indium or gallium is used as the outer layer B (when used as particles contained in an anisotropic adhesive) In this case, the diameter of the interior is about 10 μm and the thickness of the outer layer is about 5 μm, so the diameter of the nozzle is also adjusted to about 20 μm. The container 12 contains a liquid 15, here glycerin or oil, which is dropped from the nozzle into this liquid 11, that is, the outer layer material 8 enclosing the particles A (here, plastic or ferrite). Is introduced and cooled to solidify to form particles 16 having a two-layer structure.

A heating power source 13 heats a heater 14 mounted around the container 12. The purpose of the heater 14 is to melt the material to be the outer layer B.

Explaining the manufacturing procedure, first, a material (indium, gallium) to be an outer layer and particles having a higher melting point (forming an inner layer) than that are put into the container 7 through an injection port (not shown). Then, as shown in FIG. 1, the container 7 is turned upside down and supported by an appropriate supporting device (not shown).
Put some in 12 liquids (glycerin, oil). By heating the heater, the materials (indium and gallium) in the container 7 are dissolved, but the particles are not dissolved. The dissolved material wrapped with particles is dropped from the nozzle in a drop shape, shaped as it hardens in the liquid (glycerin, oil), and is deposited on the bottom surface of the container. At the same time, the material in which the particles that were in a molten state were wrapped around was solidified by the heat, and the particles of the double-layer structure 16
Is completed.

A pressure controller (not shown) may be used to optimize the amount of the dissolved material and particles flowing out of the nozzle, and the pressure applied to the surface of the dissolved material in the container 7 may be controlled.

Further, although the illustrated method is a badge processing method, it may be configured to be a continuous method so that particles having a two-layer structure are continuously produced.

The two-layered particles produced by the above-mentioned method have the same structure as in FIG. 1, but the nozzle diameter of the container 7'is slightly larger than that of the particles. By repeating the above manufacturing process by adding the material to be the outer layer, a granule having a three-layer structure can be manufactured. You can

3 to 6 are application examples of the two-layer particles manufactured in this way.

In FIG. 3, the particles 16 ″ contained in the anisotropic adhesive 3 ′ have a ferrite (magnetic material) inside (particle A) and a conductive metal such as indium or gallium as the outer layer 2
It is a layered particle. Therefore, if a magnetic field is applied from the outside to control, the particles 16 ″ in the adhesive will move, so the dispersibility can be controlled. With proper magnetic field control, a terminal to which a larger number of particles should be connected than other parts For example, as the simplest method, if a magnetic field B is applied as shown in Fig. 3, the terminals are magnetized and the particles are attracted and collected near the terminals. It is possible to reduce the incidence of contact failure between terminals that should be connected and the short circuit between terminals that should not be connected, and the yield rate of the adhesive as a connector is good.
It is possible to raise.

FIG. 4 shows that the inside (particle A) having a low specific gravity such as plastic is used, and the outer layer B is made of gallium or indium particles having a two-layer structure are dispersed in a dissolved rubber to harden the rubber. This is a connector (anisotropic elastic rubber member) that has been lowered. Since the particles having the two-layer structure have a lower specific gravity than particles of one conventional material (single layer), the dispersibility in the dissolved rubber in the process of manufacturing the anisotropic elastic rubber member 3'is improved. FIG. 6 shows an LCD (terminal 5 ′ of the liquid crystal display 17 and terminal 4 of the printed circuit board 2) using the anisotropic elastic rubber member 3 ″ (connector) thus manufactured.
Is shown in the connected state. The connector 3 ″ is inserted between the terminals 5 ′ and 4, and the LCD and the printed circuit board are fixed by the pressing member 18. FIG. 5 shows a partial sectional view taken along the line in FIG. Since the dispersibility of ′ is good, it is possible to increase the yield.

[Effects of the Invention] According to the present invention, the melted material drops particles in a form in which the particles are entrapped from the nozzle. After that, particles in a two-layer structure or a multi-layer structure can be formed by simply putting it in a liquid and exposing the heat to the melted material. Therefore, the conductive adhesive can be easily manufactured.

[Brief description of drawings]

FIG. 1 shows a device for carrying out the invention,
FIG. 2 shows particles having a two-layer structure manufactured by the apparatus shown in FIG. 1, FIGS. 3 to 6 show application examples of particles having a two-layer structure, and FIG. 7 shows a conventional anisotropic adhesive. It is a figure which shows a usage example. 7 ... Container, 8 ... Dissolving material, A ... Particle, 13 ... Heating power supply, 14 ... Heater, 15 ... Liquid, 12 ... Container, 16 ...
Two-layer structure particles

Claims (1)

[Claims] 1. A particle having a melting point higher than that of the conductive material and a specific gravity lower than that of the conductive material is mixed into the conductive material, and the particle encased in the conductive material melted from a nozzle is substantially liquid at room temperature. And having a specific gravity smaller than the specific gravity of the particles encased in the conductive material, the upper part of which is dropped to a liquid layer heated near the temperature at which the conductive material is melted, and the particles are wrapped in the liquid layer. A method for producing a conductive adhesive, characterized in that a conductive substance obtained by precipitating and cooling the solidified conductive material to solidify is added to the adhesive.