JP2849283B2 - Method for producing conductive particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing conductive particles used for electrically connecting terminals of a substrate such as a liquid crystal panel or a thermal printer head to terminals of a semiconductor element for driving the substrate. About.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional terminal connection structure, wherein reference numeral 1 denotes a substrate of one electronic component, and reference numeral 2 denotes a substrate of the other electronic component. Terminals 4 and 5 are provided on the surfaces of the substrates 1 and 2. Between these substrates 1 and 2,
An adhesive layer 6 in which conductive particles 3 are dispersed in an adhesive is provided. The terminals 4 and 5 are electrically connected via the conductive particles 3 of the adhesive layer 6. In order to form this terminal connection structure, an adhesive in which the conductive particles 3 are dispersed is applied to the substrate 1 and then the other substrate 2 is pressed so that the terminals 4 and 5 of the substrates 1 and 2 are electrically conductive particles. 3.

[0003]

However, in the connection structure as described above, as shown in FIG.
May be agglomerated, and the agglomerated conductive particles 3
Therefore, there is a problem in that it is difficult to narrow the electrode pitch because a short circuit occurs between the adjacent terminals 4, 4 and 5, 5 via.

Accordingly, the present applicant has filed Japanese Patent Application No. Hei 3-16725.
No. 8 has previously proposed a method for solving the above problem.

FIG. 7 is a process chart for explaining a method for producing conductive particles proposed by the present applicant. First, FIG.
As shown in (a), a recess 8 is formed by anisotropic etching on the surface of a silicon crystal substrate 7 used as a substrate for producing conductive particles (hereinafter referred to as a substrate for producing particles). Anisotropic etching is, for example, an etching method using a KOH aqueous solution after forming a mask having a predetermined pattern of openings on the surface of a (100) silicon crystal or a (110) silicon crystal. This method utilizes a phenomenon that an etching rate varies depending on the crystal orientation. Although the shape of the concave portion 8 of the particle manufacturing substrate 7 is not limited, it is desirable that the concave portion 8 is gradually narrowed toward a deep portion like a quadrangular pyramid. Since the size of each recess is determined by the precision of the mask, it can be up to several μm in principle.

Next, as shown in FIG. 7B, the surface 9 of the particle-producing substrate 7 which has been anisotropically etched is subjected to a treatment 9 described later for deteriorating the wettability with a melt of a conductive material.

Subsequently, as shown in FIG. 7C, a metal to be a conductive material such as gold, nickel, a solder alloy, and indium is deposited by a method such as vapor deposition, sputtering, electrolytic plating, and electroless plating. When the conductive material film (hereinafter, referred to as a material film) 10 is melted by heating, each of the concave portions 8 becomes spherical due to surface tension. When this is cooled, conductive particles 11 are obtained for each recess 8 as shown in FIG. Here, the size of the conductive particles 11 is determined by the size of the recess 8 of the substrate 7 for manufacturing particles.
Is determined by the opening area and depth of the substrate and the thickness of the material film 10 so as to protrude from the concave portion 8 of the particle manufacturing substrate 7 by about several μm.

[0008] Thereafter, as shown in FIG. 7 (e), the substrate 1 of the first electronic component is opposed to the surface of the particle production substrate 7 and is superposed. An adhesive 15 is applied to the surface of the substrate 1 of the first electronic component in advance.

As described above, when the substrate 1 of the first electronic component is superimposed on the substrate 7 for producing particles, the conductive particles 11 move to the substrate 1 of the first electronic component.

Thereafter, as shown in FIG. 7 (f), when the substrate 1 of the first electronic component and the substrate 2 'of the second electronic component to which the adhesive 15 has been applied are aligned and adhered to each other, Are electrically connected to the terminals 4 and 5 via the conductive particles 11.

However, this method is not without its problems. That is, after the metal is formed on the particle manufacturing substrate 7 and when the material film 10 is heated and melted, the oxide film 13 is formed on the surface of the material film 10 by the oxygen existing in the air, as shown in FIG. Since the material film 10 is formed and the thickness of the material film 10 itself is very thin, several micrometers, there is a problem that the sphere 11 is not formed due to the oxide film 13. In addition,
As a means for preventing the formation of the oxide film 13 due to oxygen in the air, a method of vacuum replacement is generally mentioned. However, such a vacuum replacement device only requires a container having excellent airtightness and pressure resistance. In addition, since various parts such as a vacuum pump are required, the apparatus becomes expensive.

The present invention has been made in view of the above-mentioned circumstances of the prior art, and has as its object to produce conductive particles having a desired particle size at low cost and without variation.

[0013]

In order to achieve the above object, the present invention provides a method for forming a conductive material film on a surface of a substrate for producing conductive particles having fine concave portions formed on the surface thereof. After applying flux to the surface of the film, the conductive material film is heated and melted, and the melted conductive material is formed into a sphere by surface tension and then cooled, so that the conductive material film is formed in each concave portion of the conductive particle manufacturing substrate. It is characterized in that conductive particles are generated. The heating and melting of the conductive material is preferably performed in an inert gas atmosphere, and nitrogen gas, argon gas, or the like can be used.

[0014]

According to the method for producing conductive particles of the present invention, a film of a conductive material is formed on the surface of a substrate for producing particles having fine recesses formed on the surface, and then a flux is applied to the surface.
Thereafter, the film is heated and melted, and the melt is sphericalized by surface tension, and then cooled to generate conductive particles in each concave portion of the particle manufacturing substrate. Therefore, the conductive particles are formed in a state where they are separated by the walls between the concave portions of the particle manufacturing substrate. The flux also prevents the surface of the material film from being exposed to air to form an oxide film, and also serves to remove the oxide film that has been formed undesirably. Without being hindered, the conductive particles can be manufactured with an inexpensive device.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a process diagram showing a method for producing conductive particles according to an embodiment of the present invention, and the same components as those in FIG. 7 are denoted by the same reference numerals.

The substrate 7 for producing particles shown in FIG.
The (110) plane can be formed by covering the surface of the silicon crystal with a mask having a square opening provided in a predetermined pattern and performing anisotropic etching using a KOH aqueous solution or the like. The surface of the substrate 7 for particle production is subjected to a treatment 9 so that wettability with a melt of a conductive material to be deposited later is deteriorated.

After preparing the substrate 7 for producing particles as described above, a solder alloy is deposited on the surface of the substrate 7 for producing particles.
As shown in FIG. 1B, a material film 10 is formed.

After forming the material film 10 as described above, FIG.
As shown in (c), the flux 14 is applied to the surface of the material film 10.
Is applied, and then heated and melted under a nitrogen atmosphere. Then, the molten conductive material 10 is sphericalized at each concave portion 8 by surface tension. When this is cooled, conductive particles 11 are formed for each recess 8 as shown in FIG. At this time, the amount of the flux 14 applied is preferably such that the tops of the conductive particles 11 formed in the concave portions are not exposed from the layer of the flux 14. If applied excessively, the flux layer becomes thicker, and the conductive material in each recess 8 aggregates in the flux 14 to form large particles 11 as shown in FIG.

Since the size of the conductive particles 11 is determined by the thickness of the material film 10, the material film 10 is formed so as to have an appropriate thickness, and as shown in FIG. 11 is projected several μm from the surface of the substrate 7 for producing particles.

After the conductive particles 11 have been formed in each recess 8 in this manner, the flux 14 is removed, and as shown in FIG. 1E, the substrate of the first electronic component is placed on the surface of the substrate 7 for particle production. Overlap one. An adhesive 15 is applied to the surface of the substrate 1 of the first electronic component in advance. When the substrate 1 of the first electronic component is superimposed on the substrate 7 for particle production in this way, as shown in FIG.
To the substrate 1 of the electronic component.

Thereafter, as shown in FIG. 1 (g), when the substrate 1 of the first electronic component and the substrate 2 of the second electronic component to which the adhesive 15 has been applied in advance are aligned and bonded, The terminals 4 and 5 are electrically connected via the conductive particles 11. The terminal connection structure thus formed has a state in which the terminals 4 of the first electronic component and the terminals 5 of the second electronic component are connected by the conductive particles 11 that are arranged apart from each other. Become.

Next, the relationship between the size of the concave portion 8 of the substrate 7 for manufacturing particles, the thickness of the material film 10, and the protrusion size of the conductive particles 11 will be described with reference to FIGS.

The recess 8 of the particle manufacturing substrate 7 manufactured by forming a mask having a square opening on the (100) wafer and performing anisotropic etching is shown in FIG.
, The angle θ formed between the bottom surface and the slope is 54.7 °.
Square pyramid. Assuming that true spherical conductive particles 11 having a radius R are formed in the concave portions 8, the protruding height H of the formed conductive particles 11 is defined as L, the length of one side of the opening of the concave portion 8. In this case, it is given by the following equation (1).

[0025]

(Equation 1)

On the other hand, the flat substrate shown in FIG.
When the material film 10 is formed on the substrate having the concave portions 8 shown in (b) by the vapor deposition method under the same conditions, the amount of the metal formed in the concave portions 8, that is, the square of the opening area L × L is formed. The amount (Vm) of the metal deposited in the recess 8 is determined by the amount (thickness × area = tL) of the metal deposited in the range of a square having a length L of one side of the flat substrate shown in FIG. ² ) is considered to be equal to This is because the amount of metal passing through the opening having the area L × L is equal under the same conditions. Therefore, assuming that all of the material film 10 formed on the inner surface of the concave portion 8 has become the conductive particles 11, the volume Vb of the conductive particles 11 (= 4πR ³ /
3) is equal to the metal amount Vm (= tL ² ) of the material film 10 formed on the inner surface of the recess 8. Therefore, the following equation (2) holds.

[0027]

(Equation 2)

Using the equation (2), the equation (1) can be rewritten as the following equation (3).

[0029]

(Equation 3)

From equation (3), it can be seen that the protrusion height H of the conductive particles 11 is determined by the thickness t of the formed material film 10 and the length L of one side of the opening of the recess 8. For example,
The length of one side of the concave portion 8 formed in the substrate 7 for particle production is L
In the case of = 10 μm, it can be predicted that forming the material film 10 to have a thickness of 1.1 μm allows the conductive particles 11 to protrude +1 μm from the surface of the particle manufacturing substrate 7. From this, if the material film 10 is formed to have an appropriate thickness, the conductive particles 11 project from the particle manufacturing substrate 7, and in this state, the conductive particles are superposed on the particle manufacturing substrate 7, and 11 can be transferred to the electronic component.

According to the above-described method for producing conductive particles of the present invention, since all of the conductive particles 11 are arranged apart from each other, short-circuiting between adjacent terminals via the conductive particles 11 can be prevented. Absent. Therefore, the terminals can be arranged at a narrow pitch, and high-density mounting is possible. Further, by providing the recesses 8 having the same shape in a grid pattern, the conductive particles 11 can be arranged in a uniform density.
Can be obtained.

After the material film 10 is formed, the surface of the material film 10 is coated with a flux 14 to prevent oxidation of the surface of the material film 10 and to remove the undesired oxide film 13. Complexity to eliminate
An expensive vacuum replacement device is not required, and the total cost can be reduced.

Furthermore, by appropriately adjusting the mask used for the anisotropic etching, it is possible to provide recesses having different sizes, shapes and depths of the openings in the substrate 7 for producing particles. Therefore, the conductive particles 11 having different particle diameters can be manufactured in the concave portions having different shapes, and the height of the conductive particles 11 protruding from the substrate 7 can be made different. Therefore, conductive particles 11 can be arranged only at desired positions of first electronic component 1.

In addition, in the present invention, a conductor layer made of a melt of a conductive material to be deposited later and having poor wettability, for example, a conductor layer made of indium tin oxide, is provided on the surface of a substrate made of a conductor or an insulator. Forming an insulating film having poor wettability with a melt of a conductive material thereon, and manufacturing the conductive particles using a particle manufacturing substrate having a recess formed by etching the insulating film. Is also possible.

[0035]

As described above, according to the present invention,
By appropriately setting the opening area of the concave portion and the thickness of the conductive material, conductive particles having a desired particle size can be manufactured without variation, and an oxide film is prevented from being formed on the surface of the material film by the flux. Therefore, an expensive vacuum replacement device is not required, and the conductive particles can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a process chart showing a method for producing conductive particles according to an example of the present invention.

FIG. 2 is an explanatory diagram of a flux operation.

FIG. 3 is an explanatory view showing a concave portion of the substrate for producing particles.

FIG. 4 is a cross-sectional view for explaining conditions for calculating the amount of a conductive material formed on the surface of a concave portion of a particle manufacturing substrate.

FIG. 5 is a sectional view showing a terminal connection structure according to a conventional example.

FIG. 6 is a cross-sectional view for explaining a problem of the terminal connection structure of FIG. 5;

FIG. 7 is a process chart showing a method for producing conductive particles previously proposed by the present applicant.

FIG. 8 is a cross-sectional view for explaining a problem of the method for producing the conductive particles of FIG. 7;

[Explanation of symbols]

 7 Substrate for particle production 8 Depression 10 Material film 11 Conductive particles 14 Flux

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01B 13/00 B01J 2/00 H01B 5/00 H05K 1/02-1/14 H05K 3/32

Claims (1)

(57) [Claims] 1. A film of a conductive material is formed on the surface of a substrate for producing conductive particles having fine concave portions formed on the surface, and then a flux is applied to the surface of the film. Producing the conductive particles by heating and melting, and then cooling the melted conductive material into a spherical shape due to surface tension, thereby forming conductive particles in each concave portion of the conductive particle manufacturing substrate. Method.