Preparation method of indium-based alloy powder for low-melting-point soldering paste

Abstract

The invention discloses a preparation method of indium-based alloy powder for low-melting-point soldering paste, and belongs to the technical field of metal powder preparation. The indium-based alloy powder for the low-melting-point soldering paste is obtained through an ultrasonic atomization method after induction heating; the method comprises the following steps: adding a low-melting-point indium-based alloy raw material into a graphite crucible of a heating chamber through a feeder; starting a vacuum system to vacuumize the heating chamber until the vacuum degree is lower than 3 * 10 <-2 > MPa, and filling argon as a protective atmosphere; the melting temperature in the crucible is set, an induction coil is adopted for heating the low-melting-point indium-based alloy raw material, and alloy liquid is formed; under the pressure difference between the injection pressure of the crucible and the pressure of the atomizing chamber, the alloy liquid flows into the atomizing chamber; the alloy liquid makes contact with an ultrasonic vibration piece and is atomized into alloy powder; and the obtained indium-based alloy powder is collected through a powder collecting chamber. The method has the advantage that the low-melting-point indium-based alloy powder with the particle size being 20-100 microns and the sphericity degree being larger than 0.96 can be obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of metal powder preparation, and in particular relates to a method for preparing indium-based alloy powder for low-melting-point solder paste. Background Art

[0002] The melting point of indium-based alloy is as low as 160℃. Compared with tin-based alloy, it has the advantages of good wettability, low melting point and long fatigue life. It is widely used in the welding of high-end electronic components in aviation, aerospace, medical, etc. In indium-based alloy, In has a low melting point, which is conducive to low-temperature welding of solder joints, thereby effectively avoiding thermal damage to the chip during welding; Pb has good fluidity and wettability, which can fill the weld during welding and enhance welding strength; Ag can improve the plasticity and creep resistance of the alloy.

[0003] At present, the methods for preparing low-melting-point indium-based alloy powders mainly include gas atomization, centrifugal atomization, and a combination of organic dispersants and mechanical oscillation ultrasonic atomization. The average particle size of the powders prepared by gas atomization and centrifugal atomization is greater than 50μm, and the shapes are irregular. A large amount of small satellite powder adheres to the surface of the powder, which seriously affects the printability of the solder paste. Compared with the first two methods, the powders prepared by the combination of organic dispersants and mechanical oscillation ultrasonic atomization have better sphericity, but the powder still adheres to a large amount of small satellite powder, and the preparation operation process is complicated. In summary, it is very urgent to improve the key parameters such as sphericity and particle size of low-melting-point indium-based alloy powders, and it is crucial to improve the welding performance and service life of high-end electronic components in aviation, aerospace, and medical. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing indium-based alloy powder for low-melting-point solder paste, which solves the problems of affecting the printability of solder paste, a large amount of small satellite powder adhering to the powder, and complicated preparation operation process. The method for preparing indium-based alloy powder for low-melting-point solder paste has the effect of obtaining low-melting-point indium-based alloy powder with a sphericity greater than 0.96 and a particle size of 20 to 100 μm.

[0005] The present invention adopts a closed system consisting of a heating chamber, an atomization chamber and a powder collection chamber, and obtains indium-based alloy powder for low-melting-point solder paste by ultrasonic atomization after induction heating. The specific steps are as follows:

[0006] Step 1: adding a low melting point indium-based alloy raw material into a graphite crucible in a heating chamber through a feeder;

[0007] Step 2: Start the vacuum system to reduce the vacuum degree in the heating chamber to less than 0.03 MPa, and then fill it with argon as a protective atmosphere;

[0008] Step 3, setting the melting temperature in the crucible, and using an induction coil to heat the low melting point indium-based alloy raw material to form an alloy liquid;

[0009] Step 4: Under the pressure difference between the crucible injection pressure and the atomization chamber pressure, the alloy liquid flows into the atomization chamber;

[0010] Step 5, the alloy liquid contacts the ultrasonic vibration plate and is atomized into alloy powder;

[0011] Step 6: Collect the obtained indium-based alloy powder through a powder collecting chamber.

[0012] The present invention is further configured as follows: the indium-based alloy is one of an indium-lead alloy (the mass ratio of In and Pb is 75-90:10-25), an indium-silver alloy (the mass ratio of In and Ag is 75-95:5-25) or an indium-lead-silver alloy (the mass ratio of In, Pb and Ag is 75-90:10-20:2-8).

[0013] The present invention is further configured such that the raw material is in the form of granules of any shape or rods of any cross-section shape.

[0014] The present invention is further configured as follows: the melting temperature in the crucible is 160°C to 300°C.

[0015] The present invention is further configured as follows: the crucible injection pressure is 0.02-0.05 MPa.

[0016] The present invention is further configured as follows: the pressure of the atomization chamber is 0.02-0.03 MPa.

[0017] The present invention is further configured as follows: the ultrasonic frequency is 40kHz, and the ultrasonic generator power is 30W.

[0018] The present invention is further configured such that: the ultrasonic amplitude is 40-100%.

[0019] The present invention has the following beneficial effects:

[0020] (1) Induction heating is used as a heating source to heat and melt the low-melting-point indium-based alloy raw materials, which has the characteristics of highly stable powder morphology;

[0021] (2) By controlling the melting temperature in the crucible, the pressure difference between the crucible injection pressure and the atomization chamber pressure, and the ultrasonic amplitude, low-melting-point indium-based alloy powders of various particle sizes can be produced. The particle size of the indium-based alloy powder can be controlled at 20 to 100 μm, and the sphericity is greater than 0.96, which effectively improves the key parameters of the low-melting-point indium-based alloy powder, such as sphericity and particle size, and improves the welding performance and service life of high-end electronic components in aviation, aerospace, medical, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a scanning electron microscope image of the indium-based alloy powder for low melting point solder paste prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0023] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0024] Unless otherwise specified, the raw materials used in the following examples are commercially available or can be prepared by known methods.

[0025] Example 1

[0026] 100 g of indium-lead-silver alloy (In, Pb and Ag mass ratio of 80:15:5) raw material is added into the graphite crucible of the heating chamber through a feeder, the vacuum system is started to evacuate the vacuum degree in the heating chamber to less than 0.03 MPa, and then argon is filled as a protective atmosphere. The melting temperature in the crucible is set to 160°C, and the raw material is heated by an induction coil to form an alloy liquid. The crucible injection pressure is adjusted to 0.05 MPa, and the atomization chamber pressure is adjusted to 0.02 MPa. Under the action of the pressure difference, the alloy liquid flows into the atomization chamber, the ultrasonic frequency is controlled to 40 kHz, the ultrasonic generator power is 30 W, and the ultrasonic amplitude is 40%. After the flowing alloy liquid contacts the ultrasonic vibration plate, it is broken and atomized into indium-lead-silver alloy powder, and is collected through a powder collection chamber.

[0027] Example 2

[0028] 100 g of indium-lead-silver alloy (In, Pb and Ag mass ratio of 80:15:5) raw material was added into the graphite crucible of the heating chamber through a feeder, the vacuum system was started to evacuate the vacuum degree in the heating chamber to less than 0.03 MPa, and then argon gas was filled in as a protective atmosphere. The melting temperature in the crucible was set to 200°C, and the raw material was heated by an induction coil to form an alloy liquid. The crucible injection pressure was adjusted to 0.05 MPa, and the atomization chamber pressure was adjusted to 0.02 MPa. Under the action of the pressure difference, the alloy liquid flowed into the atomization chamber, the ultrasonic frequency was controlled to 40 kHz, the ultrasonic generator power was 30 W, and the ultrasonic amplitude was 40%. After the flowing alloy liquid came into contact with the ultrasonic vibration plate, it was crushed and atomized into indium-lead-silver alloy powder, and collected through a powder collection chamber.

[0029] Example 3

[0030] 100 g of indium-lead-silver alloy (In, Pb and Ag mass ratio of 80:15:5) raw material was added into the graphite crucible of the heating chamber through a feeder, the vacuum system was started to evacuate the vacuum degree in the heating chamber to less than 0.03 MPa, and then argon gas was filled in as a protective atmosphere. The melting temperature in the crucible was set to 300°C, and the raw material was heated by an induction coil to form an alloy liquid. The crucible injection pressure was adjusted to 0.05 MPa, and the atomization chamber pressure was adjusted to 0.02 MPa. Under the action of the pressure difference, the alloy liquid flowed into the atomization chamber, the ultrasonic frequency was controlled to 40 kHz, the ultrasonic generator power was 30 W, and the ultrasonic amplitude was 40%. After the flowing alloy liquid came into contact with the ultrasonic vibration plate, it was crushed and atomized into indium-lead-silver alloy powder, and collected through a powder collection chamber.

[0031] Example 4

[0032] 100 g of indium-lead-silver alloy (In, Pb and Ag mass ratio of 80:15:5) raw material was added into the graphite crucible of the heating chamber through a feeder, the vacuum system was started to evacuate the vacuum degree in the heating chamber to less than 0.03 MPa, and then argon gas was filled in as a protective atmosphere. The melting temperature in the crucible was set to 300°C, and the raw material was heated by an induction coil to form an alloy liquid. The crucible injection pressure was adjusted to 0.04 MPa, and the atomization chamber pressure was adjusted to 0.03 MPa. Under the action of the pressure difference, the alloy liquid flowed into the atomization chamber, the ultrasonic frequency was controlled to 40 kHz, the ultrasonic generator power was 30 W, and the ultrasonic amplitude was 40%. After the flowing alloy liquid came into contact with the ultrasonic vibration plate, it was crushed and atomized into indium-lead-silver alloy powder, and collected through a powder collection chamber.

[0033] Example 5

[0034] This embodiment provides a method for preparing indium-based alloy powder for low melting point solder paste, which specifically includes the following steps:

[0035] 100 g of indium-lead-silver alloy (In, Pb and Ag mass ratio of 80:15:5) raw material was added into the graphite crucible of the heating chamber through a feeder, the vacuum system was started to evacuate the vacuum degree in the heating chamber to less than 0.03 MPa, and then argon gas was filled in as a protective atmosphere. The melting temperature in the crucible was set to 300°C, and the raw material was heated by an induction coil to form an alloy liquid. The crucible injection pressure was adjusted to 0.05 MPa, and the atomization chamber pressure was adjusted to 0.02 MPa. Under the action of the pressure difference, the alloy liquid flowed into the atomization chamber, the ultrasonic frequency was controlled to 40 kHz, the ultrasonic generator power was 30 W, and the ultrasonic amplitude was 60%. After the flowing alloy liquid came into contact with the ultrasonic vibration plate, it was crushed and atomized into indium-lead-silver alloy powder, and collected through a powder collection chamber.

[0036] Example 6

[0037] 100 g of indium-lead-silver alloy (In and Pb mass ratio is 85:15) raw material is added into the graphite crucible of the heating chamber through a feeder, the vacuum system is started to evacuate the vacuum degree in the heating chamber to less than 0.03 MPa, and then argon is filled as a protective atmosphere. The melting temperature in the crucible is set to 300°C, and the raw material is heated by an induction coil to form an alloy liquid. The crucible injection pressure is adjusted to 0.05 MPa, and the atomization chamber pressure is adjusted to 0.02 MPa. Under the action of the pressure difference, the alloy liquid flows into the atomization chamber, the ultrasonic frequency is controlled to 40 kHz, the ultrasonic generator power is 30 W, and the ultrasonic amplitude is 40%. After the flowing alloy liquid contacts the ultrasonic vibration plate, it is broken and atomized into indium-lead-silver alloy powder, and is collected by a powder collection chamber.

[0038] Example 7

[0039] 100 g of indium-lead-silver alloy (In and Ag mass ratio of 95:5) raw material was added into the graphite crucible of the heating chamber through a feeder, the vacuum system was started to evacuate the vacuum degree in the heating chamber to less than 0.03 MPa, and then argon gas was filled in as a protective atmosphere. The melting temperature in the crucible was set to 300°C, and the raw material was heated by an induction coil to form an alloy liquid. The crucible injection pressure was adjusted to 0.05 MPa, and the atomization chamber pressure was adjusted to 0.02 MPa. Under the action of the pressure difference, the alloy liquid flowed into the atomization chamber, the ultrasonic frequency was controlled to 40 kHz, the ultrasonic generator power was 30 W, and the ultrasonic amplitude was 40%. After the alloy liquid flowed down came into contact with the ultrasonic vibration plate, it was crushed and atomized into indium-lead-silver alloy powder, and collected through a powder collection chamber.

[0040] The indium-based alloy powder for low-melting-point solder paste prepared by the above method has uniform particle size, and can prepare low-melting-point indium-based alloy powder with a particle size of 20 to 100 μm and a sphericity greater than 0.96.

[0041] The above embodiments are merely descriptions of specific implementation methods of the present invention, and are not intended to limit the scope of the present invention. Those skilled in the art may make various modifications and changes based on the prior art. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary engineering and technical personnel in the field shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing indium-based alloy powder for low melting point solder paste, characterized in that: A closed system consisting of a heating chamber, an atomization chamber and a powder collection chamber is used, and a low melting point indium-based alloy powder is obtained by ultrasonic atomization after induction heating. The specific steps are as follows: Step 1: adding a low melting point indium-based alloy raw material into a graphite crucible in a heating chamber through a feeder; Step 2: Start the vacuum system to reduce the vacuum degree in the heating chamber to less than 0.03 MPa, and then fill it with argon as a protective atmosphere; Step 3, setting the melting temperature in the crucible, and using an induction coil to heat the low melting point indium-based alloy raw material to form an alloy liquid; Step 4: Under the pressure difference between the crucible injection pressure and the atomization chamber pressure, the alloy liquid flows into the atomization chamber; Step 5, the alloy liquid contacts the ultrasonic vibration plate and is atomized into alloy powder; Step 6: Collect the obtained indium-based alloy powder through a powder collecting chamber.

2. The method for preparing indium-based alloy powder for low melting point solder paste according to claim 1, characterized in that: The indium-based alloy is one of an indium-lead alloy, an indium-silver alloy or an indium-lead-silver alloy; wherein the mass ratio of In to Pb in the indium-lead alloy is 75-90:10-25, the mass ratio of In to Ag in the indium-silver alloy is 75-95:5-25, and the mass ratio of In, Pb and Ag in the indium-lead-silver alloy is 75-90:10-20:2-8.

3. The method for preparing indium-based alloy powder for low melting point solder paste according to claim 1, characterized in that: The raw material is in the form of granules of any shape or rods of any cross-section shape.

4. The method for preparing indium-based alloy powder for low melting point solder paste according to claim 1, characterized in that: The melting temperature in the crucible is 160°C to 300°C.

5. The method for preparing indium-based alloy powder for low melting point solder paste according to claim 1, characterized in that: The crucible injection pressure is 0.02-0.05 MPa.

6. The method for preparing indium-based alloy powder for low melting point solder paste according to claim 1, characterized in that: The pressure of the atomization chamber is 0.02-0.03 MPa.

7. The method for preparing indium-based alloy powder for low melting point solder paste according to claim 1, characterized in that: The ultrasonic frequency is 40kHz, and the ultrasonic generator power is 30W.

8. The method for preparing an indium-based alloy powder for low melting point solder paste according to claim 1, characterized in that: The ultrasonic amplitude is 40-100%.

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