A method for reducing Sn-based solder nanocrystals by electron irradiation

Abstract

This invention relates to a method for reducing Sn-based solder nanocrystals by electron irradiation, belonging to the field of irradiation surface modification technology. It includes the following steps: Step 1: Preparing an oxidized solder sample; Step 2: Irradiating the oxidized solder with electron irradiation. This invention, by using electron irradiation on the surface of Sn-based solder, can reduce the oxide layer on the Sn-based solder surface. Compared with traditional oxide chemical reduction methods and mechanical cleaning methods, it has advantages such as no environmental pollution, high controllability, no introduction of impurities, and the ability to reduce oxide layers on the surface of Sn-based solder with fine structures or complex shapes.

Description

Technical Field

[0001] This invention relates to a method for irradiating and reducing solder, belonging to the field of irradiation surface modification technology. Background Technology

[0002] Sn-based solders are widely used in electronic device packaging and microelectronic packaging due to their excellent soldering performance, low melting point, and superior electrical and thermal conductivity. However, an oxide layer, such as SnO and SnO2, often forms on the solder surface. These oxide layers can affect the quality of the solder joint, leading to poor contact, reduced thermal conductivity, and reliability issues.

[0003] Traditional methods for removing oxides include chemical reduction and mechanical cleaning. However, these methods have some drawbacks. Chemical reduction often requires the use of strong acids or reducing agents, which can pollute the environment and is complex to operate. Mechanical cleaning can damage the solder surface, especially when dealing with devices with fine structures or complex shapes.

[0004] Therefore, there is an urgent need to propose a method for reducing Sn-based solder metal nanocrystals by electron irradiation to solve the above-mentioned technical problems. Summary of the Invention

[0005] To address the aforementioned problems, a method for reducing Sn-based solder nanocrystals by electron irradiation is provided. A brief overview of the invention is given below to provide a basic understanding of certain aspects of the invention. It should be understood that this overview is not an exhaustive summary of the invention. It is not intended to identify key or essential parts of the invention, nor is it intended to limit the scope of the invention.

[0006] The technical solution of the present invention:

[0007] A method for reducing Sn-based solder nanocrystals by electron irradiation includes the following steps:

[0008] Step 1: Prepare an oxidized solder sample;

[0009] Step 2: Irradiate the oxidized solder with electrons.

[0010] Preferred method: In step 1, the solder sample is operated under normal temperature and pressure conditions for 30 days to allow a surface oxide layer to grow naturally on its surface, thus obtaining a solder sample with an oxide layer (oxidized solder); or an oxide layer is generated by long-term use in electronic devices.

[0011] Preferred: Step 2 includes the following steps:

[0012] Step 2.1: Place the oxidized solder into the electron irradiation device (electron accelerator), align it with the center of the electron emission gun, and place a glass plate between the oxidized solder and the metal base to reduce the contamination of the Sn-based solder sample surface by atomic sputtering of the metal base during electron irradiation.

[0013] Step 2.2: Use an electron emission gun to irradiate the surface of the oxidized base solder sample with electrons;

[0014] Step 2.3: Obtain the restored solder.

[0015] Preferably, in step 2.1, the glass plate is a single-sided conductive glass plate with a length and width of 5cm and a thickness of 5mm, and the base of the electron irradiation device is a metal base. During the irradiation process, the conductive surface of the glass is connected to the metal base of the electron irradiation device through conductive tape to reduce the accumulated charge on the surface of the glass plate.

[0016] Preferably, in step 2.2, electron irradiation is performed under ambient temperature and pressure air conditions. During the electron irradiation process, the electron energy is 200 keV~10 MeV, and the electron irradiation flux rate is 1×10⁻⁶. 11 e / cm 2 ·s~2×10 12 e / cm 2 ·s, total electron irradiation flux is 5×10 15 e / cm 2 ~2×10 16 e / cm 2 .

[0017] Preferred method: An electron irradiation reduction method for Sn-based solder metal nanocrystals is applied to the reduction of Sn-based solder (solder sample).

[0018] Preferred: Sn-based solders are SnAg and Sn a1 Cu b1 Sn a1 Pb b1 Sn a1 Bi b1 Sn a1 Zn b1 Sn a2 Ag b2 Cu C2 Sn a2 Pb b2 Cu C2 or Sn a2 Pb b2 Sb C2 .

[0019] Preferred: a1, a2, b1, b2, c2 correspond to the mass percentage content of each element atom, 50%≤a1≤100%, 50%≤a2≤100%, 0%≤b1≤50%, 0%≤b2≤50%, 0%≤c2≤50%, a1+b1=100%, a2+b2+c2=100%.

[0020] Preferably, the shape of the brazing filler metal is one or more of the following: sheet, filament, ball, block, powder, column, foil, or paste.

[0021] Preferred: For sheet and / or block solders, the length, width and thickness are all less than or equal to 1 cm; for wire solders, the diameter is 50 nm to 100 μm.

[0022] The present invention has the following beneficial effects:

[0023] This invention reduces the oxide layer on the surface of Sn-based solder by electron irradiation. Compared with traditional oxide chemical reduction and mechanical cleaning methods, it has the advantages of no environmental pollution, strong controllability, no introduction of impurities, and the ability to reduce the oxide layer on the surface of Sn-based solder with fine structure or complex shape. Attached Figure Description

[0024] Figure 1 The TEM sample of the SnPb eutectic solder joint that has already undergone oxidation was subjected to a total flux of 2×10⁻⁶. 16 e / cm 2 BFI and corresponding selected area electron diffraction patterns before and after electron irradiation;

[0025] Figure (a) shows the TEM sample BFI of the oxidized SnPb eutectic solder joint;

[0026] Figure (b) is an enlarged view of the BFI within the red dashed box in Figure (a);

[0027] Figure (c) shows the area within the red dashed box in Figure (a) with a total injection volume of 2 × 10. 16 e / cm 2 Enlarged BFI image after electron irradiation;

[0028] Figure (d) shows the selected area electron diffraction mode corresponding to Figure (b);

[0029] Figure (e) shows the selected area electron diffraction mode corresponding to Figure (c).

[0030] Figure 2 This is a schematic diagram of an electron irradiation device.

[0031] In the diagram: 1-Servo motor, 2-Gear, 3-Ring gear, 4-First connecting rod, 5-Second connecting rod, 6-Base, 7-Shaft, 8-Housing, 9-Electronic emission gun, 10-One-way valve, 11-Mounting platform. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0033] Specific implementation method one: Combining Figure 1 This embodiment describes a method for reducing Sn-based solder nanocrystals by electron irradiation, comprising the following steps:

[0034] Step 1: Prepare an oxidized solder sample;

[0035] Step 2: Irradiate the oxidized solder with electrons;

[0036] The surface modification technology of this invention through electron irradiation can be carried out under normal temperature and pressure conditions without damaging the surface of Sn-based solder, and can effectively remove the oxide layer. It is efficient, pollution-free, and highly controllable, and has a promising application prospect.

[0037] Specific Implementation Method Two: Combining Figure 1 This embodiment describes a method for reducing Sn-based solder metal nanocrystals by electron irradiation. In step 1, the solder sample is operated under normal temperature and pressure conditions for 30 days to allow a surface oxide layer to grow naturally on its surface, resulting in a solder sample with an oxide layer (oxidized solder); or an oxide layer is generated by long-term use in electronic devices.

[0038] Specific implementation method three: Combining Figure 1-2This embodiment describes a method for reducing Sn-based solder nanocrystals by electron irradiation. Step 2 uses an electron irradiation device, including a servo motor 1, a gear 2, a ring gear 3, a first connecting rod 4, a second connecting rod 5, a base 6, a rotating shaft 7, a housing 8, an electron emission gun 9, a one-way valve 10, and a mounting platform 11. The rotating shaft 7 has a through hole in its middle and is fixedly connected to the mounting platform 11. The lower part of the base 6 passes through the through hole and is fixedly connected to the mounting platform 11. The upper edge of the base 6 is machined with external threads. The housing 8 is cylindrical, and its inner wall is machined with internal threads. The base 6 is threadedly connected to the housing 8. The upper side wall of the housing 8 has an inlet and outlet, and a one-way valve 10 is installed at each of the inlet and outlet. The electron emission gun 9 is fixedly installed on the upper part of the housing 8. The rotating shaft 7 is connected to the ring gear 3 through a bearing. Two or more connecting rod combinations are evenly arranged on the ring gear 3. The connecting rod combinations include a first connecting rod 4 and a second connecting rod 5, which form an inward zigzag shape. To save space without affecting the operation of the device, the lower end of the outer shell 8, the first connecting rod 4, the second connecting rod 5, and the upper end of the ring gear 3 are sequentially hinged. The ring gear 3 meshes with the gear 2. The servo motor 1 is connected to the mounting platform 11 by bolts. The output end of the servo motor 1 is connected to the gear 2. The servo motor 1 drives the ring gear 3 to rotate through the gear 2, thereby driving the outer shell 8 to rotate through the connecting rod assembly. During the rotation, the outer shell 8 is raised and lowered through the internal and external thread engagement, so that the electron emission gun 9 can rotate and irradiate the brazing filler metal. At the same time, the oxide layer has a thickness. As the oxide layer surface is reduced, the outer shell 8 descends, bringing the electron emission gun 9 closer to the internal oxide surface under the oxide layer surface, reducing the influence of the thickness on the oxide layer reduction, ensuring uniform irradiation of the oxide layer in the horizontal and vertical directions, and improving irradiation efficiency. Gas can be introduced through the inlet and outlet according to experimental needs, and the pressure can be adjusted. The base 6 remains stationary and provides ample placement space, providing convenience for irradiation. It is suitable for brazing filler metals of various shapes and forms.

[0039] Includes the following steps:

[0040] Step 2.1: Place the oxidized solder into the electron irradiation device (electron accelerator), align it with the center of the electron emission gun, and place a glass plate between the oxidized solder and the metal base to reduce the contamination of the Sn-based solder sample surface by atomic sputtering of the metal base during electron irradiation.

[0041] Step 2.2: Use an electron emission gun to irradiate the surface of the oxidized base solder sample with electrons;

[0042] Step 2.3: Obtain the restored solder.

[0043] Specific implementation method four: Combination Figure 1-2This embodiment describes a method for reducing Sn-based solder nanocrystals by electron irradiation. In step 2.1, the glass plate is a single-sided conductive glass plate with a length and width of 5cm and a thickness of 5mm. The electron irradiation device base is a metal base. During irradiation, the conductive surface of the glass is connected to the electron irradiation metal base by conductive tape to reduce the accumulated charge on the surface of the glass plate. The conductive tape is used to connect the conductive side surface of the conductive glass to the metal substrate base of the irradiation chamber to release the accumulated charge inside the sample during irradiation.

[0044] Specific Implementation Method Five: Combining Figure 1-2 This embodiment describes a method for reducing Sn-based solder nanocrystals by electron irradiation. In step 2.2, electron irradiation is performed under ambient temperature and pressure conditions. During the irradiation process, the electron energy of the electron emission gun 9 is 200 keV to 10 MeV, and the electron irradiation flux rate is 1 × 10⁻⁶. 11 e / cm 2 ·s~2×10 12 e / cm 2 ·s, total electron irradiation flux is 5×10 15 e / cm 2 ~2×10 16 e / cm 2 The electron irradiation flux rate was selected to be 1×10⁻⁶. 11 e / cm 2 ·s~2×10 12 e / cm 2 ·s, total electron irradiation flux is 5×10 15 e / cm 2 ~2×10 16 e / cm 2 Irradiate Sn-based solder samples using any combination of dose rate and total injection within the range, where injection rate × time = total injection.

[0045] Specific Implementation Method Six: Combination Figure 1-2 This embodiment describes a method for reducing Sn-based solder metal nanocrystals by electron irradiation, which is applied to the reduction of Sn-based solder (solder sample).

[0046] Specific implementation method seven: Combination Figure 1 This embodiment describes a method for reducing Sn-based solder nanocrystals by electron irradiation, wherein the Sn-based solder is SnAg or Sn a1 Cu b1 Sn a1 Pb b1 Sn a1 Bi b1 Sn a1Zn b1 Sn a2 Ag b2 Cu C2 Sn a2 Pb b2 Cu C2 Sn a2 Pb b2 Sb C2 One or more of the alloys.

[0047] Specific implementation method eight: Combination Figure 1 This embodiment describes a method for reducing Sn-based solder nanocrystals by electron irradiation. a1, a2, b1, b2, and c2 correspond to the mass percentage content of each element's atoms, with 50%≤a1≤100%, 50%≤a2≤100%, 0%≤b1≤50%, 0%≤b2≤50%, 0%≤c2≤50%, a1+b1=100%, and a2+b2+c2=100%.

[0048] Specific Implementation Method Nine: Combining Figure 1 This embodiment describes a method for reducing Sn-based solder nanocrystals by electron irradiation, wherein the solder is in one or more of the following forms: sheet, filament, sphere, block, powder, column, foil, or paste.

[0049] Specific Implementation Method Ten: Combining Figure 1 This embodiment describes a method for reducing Sn-based solder nanocrystals by electron irradiation. For sheet-like and / or block-like solders, the length, width, and thickness are all less than or equal to 1 cm. For filament-like solders, the diameter is 50 nm to 100 μm.

[0050] Example 1:

[0051] A method for reducing surface oxides of Sn-based solder by electron irradiation includes the following steps:

[0052] Step 1: Prepare SnPb eutectic solder joint samples with naturally oxidized surfaces;

[0053] Step 2: Place the SnPb eutectic solder solder joint sample on the conductive side surface of the conductive glass, and connect the conductive side surface of the conductive glass to the metal substrate base of the irradiation chamber using conductive tape.

[0054] The SnPb eutectic solder joint sample and the conductive glass plate were placed together in the electron accelerator apparatus, and the sample was aligned with the center of the electron accelerator gun; the electron accelerator was started, and the electron irradiation flux rate was selected to be 1×10⁻⁶. 12 e / cm 2 ·s, total electron irradiation flux is 2×10 16 e / cm2 Irradiation treatment was applied to Sn-based solder samples;

[0055] See Figure 1 As shown in Figure (d), the selected area electron diffraction mode after oxidation shows diffraction spots corresponding to β-Sn and polycrystalline diffraction rings corresponding to SnO2; as shown in Figure (e), after a total fluence of 2×10⁻⁶, 16 e / cm 2 After electron irradiation, the polycrystalline diffraction rings corresponding to SnO2 disappeared in the selected area electron diffraction mode, leaving only the diffraction spots corresponding to β-Sn; this indicates that after a total fluence of 2×10⁻⁶, the polycrystalline diffraction rings corresponding to SnO2 disappeared. 16 e / cm 2 After electron irradiation, SnO2 in the SnPb eutectic solder joint is reduced to β-Sn; the reduction rate of oxides on the surface of Sn-based solder is greater than 90%. This invention provides a method for reducing oxides on the surface of Sn-based solder by electron irradiation. By irradiating the surface of Sn-based solder with electrons, the oxide layer on the surface of Sn-based solder can be reduced. Compared with traditional oxide chemical reduction methods and mechanical cleaning methods, it has the advantages of no environmental pollution, strong controllability, no introduction of impurities, ability to reduce oxides on the surface of Sn-based solder with fine structure or complex shape, simple operation, and no surface damage.

[0056] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be permuted and combined. Those skilled in the art can exhaust all possibilities based on the mathematical knowledge of permutation and combination. Therefore, the present invention will not describe the technical solutions after permutation and combination one by one, but it should be understood that the technical solutions after permutation and combination have been disclosed by the present invention.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for reducing Sn-based solder nanocrystals by electron irradiation, characterized in that: Includes the following steps: Step 1: Prepare the oxidized solder; Step 2: Irradiate the oxidized solder with electrons; Step 2 employs an electron irradiation device, including a servo motor (1), a gear (2), a ring gear (3), a first connecting rod (4), a second connecting rod (5), a base (6), a rotating shaft (7), a housing (8), an electron emission gun (9), a one-way valve (10), and a mounting platform (11). The rotating shaft (7) has a through hole in the middle and is fixedly connected to the mounting platform (11). The lower part of the base (6) passes through the through hole and is fixedly connected to the mounting platform (11). The upper edge of the base (6) is machined with external threads. The housing (8) is cylindrical and has internal threads machined on its inner wall. The base (6) is threadedly connected to the housing (8). The upper side wall of the housing (8) is provided with an inlet and outlet. One-way valves (10) are respectively installed at the inlet and outlet of the housing (8). The electron emission gun (9) is fixedly installed on the upper part of the housing (8). The rotating shaft (7) is connected to the ring gear (3) through a bearing. Two or more connecting rods are evenly arranged on the ring gear (3). The connecting rods include the first connecting rod (4) and the second connecting rod (5). The first connecting rod (4) and the second connecting rod (5) form an inward zigzag shape. The lower end of the outer shell (8), the first connecting rod (4), the second connecting rod (5), and the upper end of the ring gear (3) are sequentially hinged. The ring gear (3) meshes with the gear (2). The servo motor (1) is connected to the mounting platform (11) by bolts. The output end of the servo motor (1) is connected to the gear (2). The servo motor (1) drives the ring gear (3) to rotate through the gear (2), thereby driving the outer shell (8) to rotate through the connecting rods. During the rotation, the outer shell (8) is raised and lowered through the internal and external thread engagement, thereby causing the electron emission gun (9) to rotate and irradiate the brazing filler metal. The outer shell (8) descends, bringing the electron emission gun (9) closer to the internal oxide surface under the oxide layer. Step 2 includes the following steps: Step 2.1: Align the oxidized solder with the center of the electron emission gun and place a glass plate between the oxidized solder and the base; Step 2.2: Irradiate the oxidized base solder sample with electron irradiation; The servo motor (1) drives the ring gear (3) to rotate through the gear (2), thereby driving the outer shell (8) to rotate through the linkage combination. During the rotation, the outer shell (8) is raised and lowered through the internal and external thread cooperation, so that the electron emission gun (9) rotates and irradiates the brazing filler metal. At the same time, the oxide layer has a thickness. As the oxide layer surface is reduced, the outer shell (8) descends, bringing the electron emission gun (9) closer to the internal oxide surface under the oxide layer surface, reducing the influence of thickness on oxide layer reduction, ensuring uniform irradiation of the oxide layer in the horizontal and vertical directions, and improving irradiation efficiency. Gas can be introduced through the inlet and outlet according to experimental needs, and the pressure can be adjusted. The base (6) remains stationary. Step 2.3: Obtain the reduced solder; In step 2.1, the glass plate is a single-sided conductive glass plate with a thickness of 5mm, the base is a metal base, and the conductive surface of the glass is connected to the metal base by conductive tape. In step 2.2, during electron irradiation, the electron energy is 200 keV~10 MeV, and the electron irradiation flux rate is 1×10⁻⁶. 11 e / cm 2 ·s~2×10 12 e / cm 2 ·s, total electron irradiation flux is 5×10 15 e / cm 2 ~2×10 16 e / cm 2 The method for reducing Sn-based solder metal nanocrystals by electron irradiation is applied to the reduction of Sn-based solder. Sn-based solders are SnAg and Sn a1 Cu b1 Sn a1 Pb b1 Sn a1 Bi b1 Sn a1 Zn b1 Sn a2 Ag b2 Cu C2 Sn a2 Pb b2 Cu C2 Sn a2 Pb b2 Sb C2 One or more of the alloys; a1, a2, b1, b2, and c2 correspond to the mass percentage content of each element's atoms, with 50%≤a1≤100%, 50%≤a2≤100%, 0%≤b1≤50%, 0%≤b2≤50%, and 0%≤c2≤50%.

2. The method for reducing Sn-based solder nanocrystals by electron irradiation according to claim 1, characterized in that: In step 1, a surface oxide layer grows on the surface of the solder under normal temperature and pressure conditions, resulting in a solder with an oxide layer.

3. The method for reducing Sn-based solder nanocrystals by electron irradiation according to claim 1, characterized in that: The solder may be in the form of one or more of the following: sheet, filament, ball, block, powder, column, foil, or paste.

4. The method for reducing Sn-based solder nanocrystals by electron irradiation according to claim 1, characterized in that: For sheet and / or block-shaped brazing filler metals, their length, width, and thickness are all less than or equal to 1 cm. For wire-shaped brazing filler metals, their diameter is 50 nm to 100 μm.

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