JPH08295905A - Method and device for manufacturing fine metal balls - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to provide a method and an apparatus capable of stably supplying a large amount of fine metal spheres which are spherical and have uniform grains and which are not oxidized. [Structure] A metal wire piece supply part 2 used for dropping the metal wire piece 1 and a carbon tube 4 inside the core tube 3 are heated to heat and melt the metal wire piece 1 falling between them. A high frequency induction coil 5 outside the core tube 3 and a discharge port 8 for attaching a suction device for drawing a vacuum inside the core tube
And a fine metal ball recovery container 9 provided with a cooling pipe 7 for preventing the temperature rise of the fine metal ball recovery section. [Effect] It is possible to manufacture a fine metal ball without an oxide film, and it is possible to provide a highly reliable method and apparatus for manufacturing a fine metal ball as a joining member.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for producing fine metal balls used as a joining member when joining electrode terminals of an electronic circuit element of an IC chip.

[0002]

2. Description of the Related Art Various methods are used to connect electrodes of an IC chip and external leads. There is also a method of connecting using a fine wire (bonding wire) for wiring, but a method of sandwiching a metal protrusion called a bump between the electrode lead of a chip and thermocompression bonding is also widely used.

The TAB (Tape Automated Bonding) method is a technique that is drawing attention as a representative of the latter. In this method, bumps are formed in advance either on the electrode part of the IC chip or on the tip of the lead on the TAB tape.
A C chip electrode and a TAB tape having a lead are superposed on each other via bumps to bond them. Further, bumps are used not only in the TAB tape method but also in the flip chip method. The flip-chip method is a method of directly connecting electrodes on the chip surface to leads, a substrate, or the like by using bumps without using bonding wires.

A BGA (Ball Grid Array) method has been recently used as a connection method between an IC chip and a printed circuit board. In this method, metal spheres of a connecting member are attached to the electrode parts arranged in a two-dimensional matrix on the back side of the double-sided wiring board, and they are collectively bonded to the printed board.

The conventional method of making bumps provided for such applications has been plating. That is, a metal (mainly high-purity gold) to be a bump is directly formed on the electrode portion of the IC chip by plating, or is transferred to a lead tip portion on the TAB tape side once formed by plating on a glass substrate or the like. Method is the mainstream. However, the plating method has a drawback that the equipment is large and the composition of the metal used as the bump is also limited. Further, particularly when the bumps are formed by directly plating the electrode parts of the IC chip, there is a problem in that the IC chip itself passes through the plating process and the yield of the IC chips deteriorates.

As a method for solving these drawbacks, a bump forming method which does not use plating has come to be considered. One of them is a method of using fine metal balls for bumps. As a method of manufacturing the metal balls, there is already (1) a centrifugal atomized powder manufacturing method, and (2) a metal which is a material for bumps. A method in which a fine wire is processed, the metal wire is cut to a predetermined length, and then the metal wires are melted and solidified at a distance from each other to obtain spherical bumps by utilizing surface tension (Japanese Patent Laid-Open No. 4-066602). (3), and (3) free-falling the finely cut metal spheres in a vertical furnace, and heating them to a temperature above the melting point of the metal to make them spherical by the action of surface tension during dropping. A method of solidifying as it is and taking it out from the bottom of the furnace (see JP-A-4-066601); and (4)
There is a method (see Japanese Patent Application No. 05-082255) in which a finely cut metal wire piece is placed on an inert gas stream and dropped. The spherical bumps produced by these methods are used by thermocompression bonding to the tip portions of leads and the like (Japanese Patent Application Laid-Open No. 3-1747).
No. 37).

According to the new method of melting an arbitrary metal wire piece into a bump, the possibility of using an arbitrary metal having a characteristic suitable as a joining member for the bump is greatly expanded. That is, copper, silver, and various alloys based on them, in addition to gold, can be easily formed as bumps.

[0008]

In the conventional method for producing fine metal spheres, there is a problem in the above (1) that it is not possible to obtain a true sphere or one having the same particle size, and in the above (2). After the metal wire pieces cut into a predetermined length were placed in the crucible at regular intervals, they were melted. This is because, if the metal wire pieces enter the melting step with the metal wire pieces being in contact with each other or being placed too close to each other, the metal wire pieces may be united during the melting. In this method, if all the metal wire pieces had a constant length, it was possible to form fine metal spheres of uniform size. However, this metal wire is 2-3 at the longest.
Since it is as small as mm, there is a problem that it takes time to arrange the metal wires and collect the fine metal balls.

Further, in the above (3), the metal wire piece is freely dropped from the upper part of the core tube, heated and melted to be spherical. However, this free fall method is possible even if the metal wire piece is large and heavy, but the metal wire piece actually used (diameter 20 to 30 μm, length 0.15 to 0.40 mm)
Then, there is a possibility that the metal wire pieces may scatter or come into contact with each other and be united due to convection inside the core tube heated above the melting point of the metal. Further, since quartz glass is used for the core tube, even if some metal wire pieces fall, the metal wire pieces and the formed fine metal balls are heated to high temperature (quartz tube). There is a problem that it cannot be recovered from the lower part of the core tube because it adheres to).

In the above (4), the metal wire piece is put on an inert gas and dropped from the upper part of the core tube to the lower part of the core tube, and is heated and melted to be spherical. However, in the method using the inert gas, when the metal piece contains an element that is easily oxidized, the metal used for the metal piece is heated to a temperature equal to or higher than the melting point, and when the metal piece is melted, a trace impurity in the gas causes There is a problem of oxidation.

The present invention has been made on the basis of the above-mentioned matters, and further improves the working efficiency by a simple device and stabilizes fine metal spheres having a perfect spherical grain and no oxide film on the surface. It is an object of the present invention to provide a method and a device that can be supplied in large quantities.

[0012]

Means for Solving the Problems The present invention for achieving the above-mentioned object is as follows: (1) The inside of a vertically arranged reactor core is evacuated from the lower portion of the reactor core, and a metal wire piece is fed from the upper portion of the reactor core to the core. A fine metal sphere characterized by making the metal wire piece spherical by dropping it to the lower part of the tube and heating and melting the metal wire piece to a temperature above the melting point of the metal used for the metal wire piece. (2) The metal wire piece supply unit arranged at the upper end of the core tube, the carbon cylinder arranged inside the core tube, and the carbon cylinder are heated to drop in the carbon cylinder. A heating unit that combines a high-frequency induction coil arranged outside the core tube for heating and melting the metal wire piece, and a gas exhaust for drawing a vacuum inside the core tube arranged at the lower end of the core tube Consists of a fine metal ball recovery unit with a mouth Preparative an apparatus for producing fine metal spheres characterized by.

[0013]

According to the present invention, with the above-mentioned structure, the inside of the core tube is evacuated to 1 Torr to 10 ^-7 Ton by the method of introducing vacuum from the lower end of the core tube.
A metal piece that has been pulled to a vacuum of rr and dropped in that vacuum is passed through a carbon cylinder that has been heated by using a high-frequency induction coil, so that the temperature is equal to or higher than the melting point of the metal used for the metal wire piece. Heat to melt. Since the molten metal has a large surface tension and becomes spherical, the metal wire piece changes into a spherical shape while falling in a carbon cylinder that has generated heat, and becomes a fine metal sphere. The vacuum not only selects the metal wire pieces and the formed fine metal balls, but also can prevent the carbon cylinder from being oxidized and damaged. The degree of vacuum depends on the metal used for the metal wire piece.
From 1 Torr in the case of high purity without fear of oxidation, it is set to 10 ^-7 Torr which is the limit of the degree of vacuum that can be reached in the core tube heated to a high temperature.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a schematic view of an apparatus used in a method for producing fine metal spheres which is an embodiment of the present invention. In this embodiment, two kinds of metal pieces (metal wire pieces) having a wire diameter of 28.4 μm and a length of 0.18 mm and a wire diameter of 17.2 μm and a length of 0.15 mm are used, and a ball diameter of 60.16 μm. And ball diameter 40.52
Two types of μm gold balls (fine metal balls) are manufactured.

The apparatus shown in FIG. 1 includes a core tube 3 and the core tube 3
The metal wire piece supply unit 2 used for dropping the metal wire piece 1 into the inside, the carbon tube 4 provided inside the core tube 3, and the metal wire piece 1 which causes the carbon tube 4 to generate heat and drops between them. Heating
A high-frequency induction coil 5 provided on the outside of the core tube 3 for melting, an exhaust port 8 for attaching a suction device for drawing a vacuum in the core tube, and a cooling for preventing the temperature rise of the fine metal ball recovery part. Fine metal sphere collection container 9 equipped with tube 7
Consists of

The core tube 3 has an inner diameter of 105 mm and a length of 550.
mm quartz glass was used. Also, the high frequency induction coil 5
The carbon cylinder 4 to generate heat using is 40 mm in inner diameter and 32 in length.
The temperature distribution was set to 0 mm and the maximum temperature (1410 ° C.) was provided near the lower end. The maximum temperature is set considerably higher than the melting point of gold in order to reliably heat the metal wire piece 1 to a temperature above the melting point by increasing the temperature.

The cooling pipe 7 is made of copper, and the cooling water is circulated to prevent the temperature rise of the fine metal ball recovery part. Further, the discharge port 8 for vacuuming and the fine metal ball recovery container 9 are made of quartz glass, and from the discharge port 8,
The internal pressure of the core tube was set to 5 × 10 ⁻⁶ Torr by a rotary pump and a diffusion pump in order to draw a vacuum inside the core tube.

The metal wire piece 1 cut by a cutting device (not shown) for fine metal balls is dropped from the metal wire piece supply portion 2 at the upper end of the furnace core tube 3, enters the furnace core tube 3, and is evacuated to carbon. Enter the cylinder 4. When the metal wire piece 1 falls in the carbon cylinder 4 and drops to a position where the high frequency induction coil 5 is present, the temperature starts to rise rapidly. Then, the metal wire piece 1 melts when the temperature becomes higher than the melting point of the metal. Therefore, the molten metal changes into a spherical shape while passing through the carbon-made cylinder 4, but when it exits the carbon-made cylinder 4, the temperature suddenly drops and the metal begins to solidify. Finally, the metal spheres fall into the collection container 9, and the solidified fine metal spheres 6 are obtained. The inventors of the present invention conducted an actual test using the above-mentioned device and metal wire piece, and found that gold spheres (particle size 60.16 μm and particle size 40.52 μm) with perfect spheres were used.
m was obtained).

As described above, in the method for producing fine metal according to the present embodiment, the step of collecting fine metal balls can be performed at once by simply inserting the metal wire piece into the core tube, so that the work efficiency is improved and mass production is performed. It is possible to improve the property. Further, in the apparatus of the present embodiment, for example, by equipping the upper end of the furnace core tube of the present embodiment with a device for cutting the fine metal wire at regular intervals, the step of cutting the fine metal wire, the spheroidizing of the cut metal wire pieces. The step and the step of collecting fine metal balls can be continuously performed.

Further, the method for producing fine metal of this embodiment can be applied to metals and alloys which have not been picked up in the past, so that fine metal spheres having an appropriate composition as bumps can be produced. In addition, in the above embodiment, the case of manufacturing a gold ball by using a metal piece has been described, but the present invention is not limited to this, and other metal corresponding to the bump may be used. Well, in that case, it is also necessary to change the maximum temperature and the degree of vacuum in the furnace. Depending on the metal, it is necessary to make the vacuum degree higher so that a chemical reaction does not occur in the high temperature heating furnace (inside the carbon cylinder 4). Further, in the above embodiment, the fine metal recovery container 9 is provided in the lower part of the core tube, but the present invention is not limited to this, and for example, the lower part of the core tube is processed into a tapered shape without using the recovery container. Alternatively, the fine metal balls may be collected from the opening hole at the lower end. As a result, for example, a belt conveyor or the like can be arranged below the core tube to continuously collect fine metal balls.

[0021]

As described above, according to the present invention, a metal wire piece dropped in a vacuumed core tube passes through a furnace (in a carbon cylinder) in which heat is generated using a high frequency induction coil. By heating and melting by doing so, a high-quality fine metal sphere without an oxide film can be easily produced, and a highly reliable method and apparatus for producing a fine metal sphere as a joining member can be provided.

[Brief description of drawings]

FIG. 1 is an explanatory view showing (a partial cross section) of a device of the present invention.

[Explanation of symbols]

 1 Metal Wire Piece 2 Metal Wire Supply Section 3 Core Tube 4 Carbon Cylinder 5 High Frequency Induction Coil 6 Fine Metal Ball 7 Cooling Tube 8 Vacuum Evacuation Port 9 Fine Metal Recovery Container

Claims (2)

[Claims] 1. Melting a metal piece in a vertically arranged core tube by dropping the metal piece from an upper part of the core tube to a lower part of the core tube, and heating the metal piece to a temperature equal to or higher than a melting point of a metal used for the metal piece. Thus, in the method for producing fine metal spheres for spheroidizing the metal pieces, the inside of the furnace core tube is evacuated, the method for producing fine metal spheres. 2. A core tube, a metal piece supply section used for dropping a metal piece arranged at the upper end of the core tube, a carbon cylinder arranged inside the core tube, and a heat generation of the carbon cylinder. A heating unit that combines a high-frequency induction coil arranged outside the core tube for heating and melting the metal piece that falls in the carbon cylinder, and an exhaust port for drawing a vacuum inside the core tube. An apparatus for producing fine metal spheres, comprising: a fine metal sphere recovery section disposed below the core tube.