JPH02122009A - Manufacture of solder powder - Google Patents

Abstract

PURPOSE:To obtain solder powder having even particle diameter at comparatively easy and stable by injecting molten metal jet stream of solder having higher than the specific temp. toward cooling liquid layer having laminar flow-state formed on inner circumferential face in a rotary drum with centrifugal force at almost the same speed as the peripheral speed of the layer. CONSTITUTION:The cooling liquid is supplied to the rotated rotary drum 10 to form the rotated cooling liquid layer 24 on the inner circumferential face in the drum 10. Successively, by feeding inert gas into the molten metal pressurizing piping 32, the molten solder 34 having high temp. at >=600 deg.C higher than the liquid phase line is injected 30 to the layer 24. At the same time of this, a molten metal injection device 26 is slowly shifted from the inlet end side 25a toward the inner end part 25b of the layer 24. In this case, the peripheral speed of the layer 24 and injecting speed of the jet stream 36 have to be almost the same. Then, the jet stream 36 is rapidly cooled with the layer 24. By this method, the solder powder 38 having the above characteristic is continuously formed to deposit this into the layer 24 in the drum 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing solder powder used for soldering electronic boards and the like.

[Prior Art] Conventionally, a rotating disk method has been used as a method for producing solder powder. In this method, molten metal is poured into the center of a horizontally rotating disk, and the molten metal poured onto the surface of the rotating disk is scattered from the periphery of the rotating disk due to centrifugal force and becomes powder.

In this rotating disk method, the shape of the rotating disk.

The material and surface properties have a significant effect on the shape and size of the particles to be powdered.

The shape of the disk is classified into three types: flat, concave, and convex. The concave shape is suitable for powders with a relatively v& fine grain size, and the convex shape is used for relatively large grain sizes. The horizontal type is somewhere in between.

Common materials used for the disk include stainless steel, special steel, die steel, titanium, and ceramics. Although the disk is rotating at high speed, the molten metal is concentrated in the center of the disk and drips, so the center is consumed by the molten metal and is consumed.

Therefore, materials that can prevent this are selected.

When the molten metal falls onto the surface of the disk, if the disk is cooled, some of the metal stuck to the surface of the disk will be blown away by centrifugal rotation, but the continuously falling metal will gradually accumulate and the disk may break. be. Therefore,
Before dropping the molten metal, it is necessary to preheat the disk to the melting temperature of the metal.

Further, the disk needs to be appropriately wetted with the molten metal. When the disk gets wet, the dropped metal flows to form a film on the surface of the disk and scatters from the tip of the disk rotating at high speed, making it possible to produce powder. Without wetting, the dropped molten metal becomes beads and rolls on the disk surface, making it impossible to collect uniform particles.

[Problems to be Solved by the Invention] As described above, in the conventional method of manufacturing solder powder using the rotating disk method, it is necessary to prepare various dyeing conditions such as preheating and wetting the rotating disk. It is very difficult to obtain solder powder stably.

The present invention has been made in view of the above-mentioned problems of conventional methods of manufacturing solder powder, and is a method of producing solder powder that can relatively easily and stably produce solder powder with uniform particle size. [Means for Solving the Problem] The inventors have conducted extensive research into a method for manufacturing solder that does not use a rotating disk. As a result, they came up with the idea of applying spinning in a rotating liquid, and after further research, they completed the present invention.

The method for producing solder powder of the present invention includes the steps of melting solder with a molten metal injection device having a molten metal nQ injection nozzle, rotating a rotating drum, injecting a cooling liquid into the rotating drum, and dissolving the solder on the inner circumferential surface of the rotating drum. forming a laminar cooling liquid layer by centrifugal force, and flowing a laminar molten jet flow of the solder at a flow rate substantially the same as the circumferential velocity of the cooling liquid layer at a temperature of 600°C or more above the liquidus line. The gist is that the method comprises a step of injecting the molten metal from the molten metal injection nozzle to the cooling liquid layer at a high temperature.

The reason why the melting temperature of the solder is set to be 600° C. or more higher than the liquidus line of the solder is that if the temperature is lower than this, the solder will be connected in a beaded shape or a line, and it will not be possible to obtain a solder powder.

As the rotating drum and the cooling liquid, those used in the conventional rotating liquid spinning method can be used as they are.

The cooling liquid layer and the molten solder jet must be in a laminar flow state. If they are not in a laminar flow state, the powder will be connected in a beaded shape or the powder will be in an irregular shape. The velocity of the molten solder jet flow and the circumferential velocity of the cooling liquid layer must be approximately equal. If they are not equal, the molten solder jet flow will not be separated in the cooling liquid in a laminar state, so the particle size will be It does not form a uniform powder.

[Function] The rotating submerged spinning device used in the present invention is shown in FIG. 1 as a front view and FIG. 2 as a side sectional view. In FIG. A coolant outflow prevention plate 16 that is attached to the cylinder and has a circular opening 14 in the center, and a blocking plate 18 that covers the entire surface of the other side of the cylindrical part 12 are integrally formed. motor 2
0 output shaft 22 is fixed, and the rotating drum 10 rotates at high speed. Cooling liquid is supplied to the inner periphery of the rotating drum 10 that rotates at high speed, and the cooling liquid forms a cooling liquid layer 2 due to centrifugal force.
form 4. The molten metal injection device 26 includes a vertical metal melting furnace 28 , a molten metal injection nozzle 30 installed downward at the lower end of the metal melting furnace 28 , and a molten metal pressurizing pipe 32 installed in the upper part of the metal melting furnace 28 . consisting of a rotating drum 1
It is inserted through the opening 14 of the rotating drum 10 and is movable in the axial direction of the rotating drum 10.

To obtain solder powder using this rotating liquid submerged spinning device, the rotating drum 10 is rotated to supply a cooling liquid to form a rotating cooling liquid layer 24 on the inner circumference of the rotating drum 10.Then, a metal melting furnace is used. The master alloy such as solder charged into the tube 28 is melted to form a molten alloy 34, the molten metal injection device 26 is inserted through the opening 14 of the rotating drum 10, and the molten metal injection nozzle 30 is placed above the inlet end 25a of the cooling liquid JI 24. Then, an inert gas is sent into the molten metal pressurizing pipe 32 to inject the molten solder 34 from the molten metal injection nozzle 30. At the same time, the molten metal injection device 26 blows the inlet end 2 of the rotating cooling liquid layer 24.
Move slowly from 5 m toward the far end 25b. The ejected molten solder jet stream 36 is ejected onto the cooling liquid layer 24 and rapidly cooled to become solder powder 38 . By this method, solder powder 38 is continuously formed and stored in the rotating cooling liquid layer 24 within the rotating drum 10.

In the rotating liquid spinning method, it is necessary that the circumferential speed of the rotating cooling liquid layer 24 and the jetting speed of the molten solder jet 36 are approximately the same. If the solder powder 38 is not matched, the obtained solder powder 38 will have a wavy line shape, a short fiber shape, a tape shape, or a bead shape.

Further, the diameter of the rotating drum 10 used in the present invention is preferably about 400 to 1000 mm, water is used as the cooling liquid, and the thickness of the rotating cooling liquid layer 24 is preferably about 10 to 30 mm. The distance from the tip to the rotating cooling liquid layer 24 is preferably 10 to 50 mm.

[Example 1] Examples of the present invention will be described below to clarify the present invention more specifically.

Solder with a composition of 5n63%-remaining pb (liIth point 1
83°C) as shown in Figures 1 and 2.
Solder powder was cast using a 0.2+am molten metal injection nozzle under the casting conditions shown in Table 1, such as the solder melting heating temperature, the flow rate of the molten solder jet, and the circumferential speed of the cooling liquid layer. . The shape of the obtained solder powder is shown in Table 1.

In Table 1, if the solder is in the form of a powder with uniform particle size, it is indicated by △ if the O2 particle size is uneven and the surface is uneven, and if it is bead-shaped or wavy line-shaped, it is indicated by ×. Ta.

In Table 1, Sample No. 1 is a comparative example with a low solder melting temperature, and Sample No. 2 is a comparative example with a slow jetting speed of the molten solder jet stream. Sample No.

3 to 5 are examples of the present invention.

(Left below) As is clear from Table 1, Sample No. 1, which is a comparative example with a low solder melting temperature, becomes bead-shaped and no solder powder is obtained, and the comparative example has a slow flow rate of the molten solder jet stream. Test fJI No. 2 was a powder, but the particle size was irregular.

On the other hand, in Tests f'-I No. 3 to 5, which are examples of the present invention, powders with uniform particle sizes were obtained, confirming the crushing effect of the present invention.

In this embodiment, the rotary drum 10 is of a vertical type, but the rotary drum 10 may be rotated horizontally.Also, the rotary drum 10 may be rotated horizontally. It is also possible to use a method in which a drum filled with coolant is fixed, a magnetic stirrer is inserted at the bottom of the drum, and a rotating magnetic field is applied under the drum to rotate the coolant.

[Effects of the Invention] As explained above, the method for producing solder powder of the present invention is a method for producing solder powder by applying a spinning method in a rotating liquid, which has not been thought of in the past. There is no need to adjust difficult casting conditions as in the conventional method, and it has the distinct advantage that solder powder with uniform particle size can be obtained extremely easily and stably.

[Brief explanation of the drawing]

FIG. 1 is a front view of a rotating submerged spinning device, and FIG. 2 is a sectional view of the rotating submerged spinning device shown in FIG. 10... Rotating drum, 24... Rotating cooling liquid layer, 2
6... Metal melting furnace, 30... Molten metal injection nozzle, 32
... Molten metal pressure piping, 34... Molten metal, 36...
/BM & Metal Jet, 38...Solder Powder Diagram Day 2b

Claims (1)

[Claims] (1) The process of melting solder with a molten metal injection device having a molten metal injection nozzle, rotating a rotating drum, injecting a cooling liquid into the rotating drum, and creating a laminar flow state by centrifugal force on the inner peripheral surface of the rotating drum. forming a cooling liquid layer, and cooling the molten metal jet stream of the solder in a laminar flow state from the molten metal injection nozzle at a temperature 600° C. or more higher than the liquidus line at a flow rate substantially the same as the circumferential velocity of the cooling liquid layer. A method for producing solder powder, comprising the step of spraying it onto a liquid layer.