JPS605802A - Production of fine metallic ball - Google Patents

Abstract

PURPOSE:To obtain a fine metallic ball having a uniform grain size by kneading single metallic substance and mixed powder having a specific grain size or below with a binder in the specific amt. with respect to the amt. of the alloy powder, dropping the mixture at every weight to form a desired ball onto a graphite plate or ceramic plate with a constant rate feeder and heating to melt and cooling the same in a non-oxidative atmosphere. CONSTITUTION:Single metallic substance, mixed powder and alloy powder having <=44mu grain size are kneaded with 10-50%, by weight, an org. binder. The mixture is dropped with a constant rate feeder onto a graphite plate or ceramic plate by 100 pieces at every 1mg, 10mg respectively in order to obtain fine metallic balls having, for example 0.5mm., 1.1mm. and 2.4mm. grain sizes. The mixture is heated to a temp. higher by 0-200 deg.C than the m.p. of the metal and is cooled in a nonoxidative atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing microscopic metal spheres having uniform particle sizes.

With the development of the semiconductor industry, the use of minute metal balls for bonding semiconductor chips and substrates, as well as for brazing and soldering of various minute products, is rapidly increasing. It is also used to make decorative items such as brooches, pendants, rings, necklaces, and earrings.

Conventionally, in order to manufacture micro metal spheres, powder with a wide particle size distribution was created using the atomization method, classified to the desired particle size, and then sized by mechanical processing, or metal wires were sequentially cut to the desired weight. Then, by machining or remelting, microscopic metal spheres of approximately uniform particle size were produced.

However, with these manufacturing methods, there is no problem in producing metal spheres with a particle size of 0.5 or more, but with a particle size of Q,
The production of minute metal spheres of less than 5+ am would result in extremely low yields, and in the latter manufacturing method, it was extremely difficult to sequentially cut thin metal wires to desired weights.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a manufacturing method capable of obtaining fine metal spheres having a uniform particle size over a wide size range.

The method for manufacturing micro metal spheres of the present invention includes 441! The following metals alone or mixed (powder or alloy powder and 1 part of its weight)
~50% of the organic binder is kneaded, and then this kneaded material is dropped onto a graphite plate or ceramic plate by weight to form the desired spheres using a quantitative feeder, and then the metal is mixed in a non-oxidizing atmosphere. It is characterized by heating at a temperature 0 to 200°C higher than the melting point and then cooling to produce minute metal spheres.

In the method for manufacturing micro metal balls of the present invention, the reason for using single metal powder, mixed powder, or alloy powder with a particle size of 44 μ or less is that if the particle size exceeds 44 μ, it becomes difficult to produce micro metal balls with a particle size Q of 5 m + w or less. It is from.

The reason why the proportion of organic binders (e.g., acrylic acid, ethylene glycol, epoxy resin) is set at 1 to 50% is that if it is less than 1%, the kneaded material that is fed to the quantitative feeder cannot have viscosity. This is because if it exceeds 50%, the powder will not be sufficiently agglomerated during heating, making it impossible to obtain the desired minute metal spheres. Furthermore, the reason why the kneaded material is dropped onto a graphite plate or a ceramic plate is that its wettability with molten metal is low. The reason why the heating atmosphere is a reducing or inert non-oxidizing atmosphere is to prevent the formation of an oxide film on the surface of the molten metal and to effectively apply surface tension to the metal to make it into a nearly perfect sphere. . Furthermore, the reason why the heating temperature is set to 0 to 200 degrees Celsius higher than the melting point of the metal to be melted is that at a temperature lower than the melting point, the same phase will intervene and a sphere will not be obtained.
This is because at a temperature higher than 200° C. than the melting point, the surface tension becomes small, and the ball cannot be formed into a sphere, resulting in a flat shape.

Next, a specific example of the method for manufacturing micro metal spheres according to the present invention will be described.

[Example 1] 1-5 meters! Reduced silver powder with a particle size distribution of 20% by weight
This kneaded material is then kneaded with an organic binder consisting of acrylic acid, and then this kneaded material is fed into a quantitative feeder with a calculated particle size of 0.5+u+,
1.11J 2. To obtain 4 quantities of micrometallic spheres 1
100 mg, lomg, and 100 mg each were dropped onto a graphite plate, and then heated at 1000°C in a nitrogen gas atmosphere.
The mixture was heated for 5 minutes and then cooled to produce three different sizes of microscopic metal spheres.

Figure 1a shows the measurement of the particle size of these three types of micrometallic spheres.
With the particle size distribution as shown in the graphs of , b, and c, each of the micro metal spheres had the required calculated particle size and a particle size similar to the required calculated particle size.

[Example 2] 90% by weight of reduced silver powder having a particle size distribution of 1 to 5μ and 1 to 5μ
After mixing 10% by weight of reduced palladium powder with a particle size distribution of 5μ in a type mixer, kneading it with an organic binder consisting of ethylene glycol at a weight ratio of 50%, and then converting this kneaded product into calculated particles using a quantitative feeder. i￥0.4m, 0
．． 9mm, 2. 1mg to obtain hm minute metal spheres
, 100 pieces each of 10 mg + 100 mg were dropped onto a ceramic Nox plate, and then 1100 pieces of each were dropped in an argon gas atmosphere.
``c'' After heating and holding for 5 minutes, the mixture was cooled to produce three types of microscopic metal spheres with different sizes.

The particle diameters of these three types of micrometallic spheres were measured, as shown in Figure 2a,
With the particle size distribution as shown in the graphs b and c, each of the micro metal spheres had the required calculated particle size and a particle size similar to the required calculated particle size.

As can be seen from the above description, the method for manufacturing micrometallic spheres of the present invention has the excellent effect of being able to efficiently and reliably produce micrometallic spheres with uniform particle sizes over a wide size range.

[Brief explanation of drawings]

FIGS. 1a, b, and c and FIGS. 2a, b, and c are graphs showing the particle size distribution of micrometallic spheres subjected to BJ in a specific example of the method for producing micrometallic spheres of the present invention, respectively. 1 Outer Person Tanaka Kikinzoku Kogyo Co., Ltd. Figure 1 (a) (b) Deleted mm) (.) "ff ("ゝFigure 2 (Q) (b) 1! 4'k (mm) ,.) R″′°“.

Claims (1)

[Claims] Single or mixed metal powder or alloy powder with a size of 44μ or less is kneaded with an organic binder at a weight ratio of 1 to 50%, and then this kneaded material is fed into a graphite plate or ceramic plate by weight to form desired balls using a quantitative feeder. 1. A method for producing micro metal balls, which comprises dropping the metal onto the surface of the metal, heating the metal at a temperature of 0 to 200° C. higher than the melting point of the metal in a non-oxidizing atmosphere, and then cooling the metal to produce micro metal balls.