Method for reducing Sn-based brazing filler metal nanocrystalline through electron irradiation

Abstract

The invention relates to a method for reducing Sn-based solder metal nanocrystals through electron irradiation, and belongs to the technical field of irradiation surface modification. Comprising the following steps that 1, an oxidized brazing filler metal sample is prepared; and 2, the oxidized brazing filler metal is subjected to electron irradiation. According to the method, the Sn-based brazing filler metal surface is irradiated through electrons, an oxide layer on the Sn-based brazing filler metal surface can be reduced, and compared with a traditional oxide chemical reduction method and a mechanical cleaning method, the method has the advantages that environmental pollution is avoided, controllability is high, impurities are not introduced, and Sn-based brazing filler metal surface oxide of a fine structure or in a complex shape can be reduced.

Description

Technical Field

[0001] The invention relates to a method for reducing solder by radiation, belonging to the technical field of radiation surface modification. Background Art

[0002] Sn-based solders are widely used in electronic device packaging and microelectronic packaging due to their good soldering properties, low melting point, and excellent electrical and thermal conductivity. However, an oxide layer, such as SnO and SnO2, is often formed on the surface of the solder, which can affect the quality of the solder joints, 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 disadvantages. Chemical reduction often requires the use of strong acids or reducing agents, which may pollute the environment and are complicated to operate. Mechanical cleaning may damage the solder surface, especially when dealing with devices with fine structures or complex shapes.

[0004] Therefore, it is urgent to propose a method for electron irradiation reduction of Sn-based solder metal nanocrystals to solve the above technical problems. Summary of the invention

[0005] To solve the above problems, a method for reducing Sn-based solder metal 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 overview of the invention. It is not intended to determine the key or important 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 metal nanocrystals by electron irradiation comprises the following steps:

[0008] Step 1: Prepare oxidized solder sample;

[0009] Step 2: Electron irradiation of the oxidized solder.

[0010] Preferably, in step 1, the solder sample is operated at room temperature and pressure for 30 days to allow a surface oxide layer to grow naturally on its surface, thereby obtaining a solder sample having an oxide layer (oxidized solder); or an oxide layer is generated by long-term use in electronic devices.

[0011] Preferably: Step 2 comprises the following steps:

[0012] Step 2.1: Place the oxidized solder in an 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 surface of the Sn-based solder sample by atomic sputtering of the metal base during electron irradiation;

[0013] Step 2.2: using electrons emitted by an electron emission gun to perform electron irradiation treatment on the surface of the oxidized base solder sample;

[0014] Step 2.3: Obtain reduced solder.

[0015] Preferably: in step 2.1, the glass plate is a single-sided conductive glass plate with a length and width of 5 cm and a thickness of 5 mm, 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 electron irradiation metal base through a 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 normal temperature and pressure air conditions. During the electron irradiation process, the electron energy is 200 KeV to 10 MeV, and the electron irradiation injection rate is 1e11 e / cm 2 ·s~2e12 e / cm 2 ·s, the total electron irradiation dose is 5e15 e / cm 2 ~2e16 e / cm 2 .

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

[0018] Preferred: Sn-based solder is SnAg, 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] Preferably: a1, a2, b1, b2, c2 correspond to the mass percentage content of each element atom, respectively, 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 solder is in the form of one or more of flake, filament, sphere, block, powder, column, foil or paste.

[0021] Preferably, for the sheet-shaped and / or block-shaped solder, the length, width and thickness are all less than or equal to 1 cm, and for the filament-shaped solder, the diameter is 50 nm to 100 μm.

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

[0023] The present invention can reduce the oxide layer on the surface of the Sn-based solder by electron irradiation on the surface of the Sn-based solder. Compared with the traditional oxide chemical reduction method and mechanical cleaning method, the present invention has the advantages of no environmental pollution, strong controllability, no introduction of impurities, and the ability to reduce the surface oxide of the Sn-based solder with fine structure or complex shape. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The BFI and corresponding selected area electron diffraction patterns of the TEM sample of the oxidized SnPb eutectic solder joint before and after electron irradiation with a total injection of 2e16 e / cm2;

[0025] Figure (a) is the BFI of the TEM sample 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 red dashed box in Figure (a) with a total injection of 2e16 e / cm 2 BFI magnified image after electron irradiation;

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

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

[0030] Figure 2 It is a schematic diagram of the structure of the electron irradiation device.

[0031] In the figure: 1-servo motor, 2-gear, 3-ring gear, 4-first connecting rod, 5-second connecting rod, 6-base, 7-rotating shaft, 8-housing, 9-electron emission gun, 10-check valve, 11-mounting table. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described below by the specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0033] Specific implementation method 1: Combination Figure 1 This embodiment is described. A method for reducing Sn-based solder metal nanocrystals by electron irradiation in this embodiment comprises the following steps:

[0034] Step 1: Prepare oxidized solder sample;

[0035] Step 2: Electron irradiating the oxidized solder;

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

[0037] Specific implementation method 2: Combination Figure 1 To illustrate this embodiment, a method for electron irradiation reduction of Sn-based solder metal nanocrystals is provided. In step 1, the solder sample is operated at room temperature and pressure for 30 days, and a surface oxide layer is naturally grown on its surface to obtain 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: Combination Figure 1-2The present embodiment is described. The present embodiment is a method for electron irradiation reduction of Sn-based solder metal nanocrystals. 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 shell 8, an electron emission gun 9, a one-way valve 10 and a mounting platform 11. The middle of the rotating shaft 7 has a through hole, the rotating shaft 7 is fixedly connected to the mounting platform 11, the lower part of the base 6 is fixedly connected to the mounting platform 11 through the through hole, the upper edge of the base 6 is processed with an external thread, the shell 8 is a barrel shape, the inner wall of the shell 8 is processed with an internal thread, the base 6 is threadedly connected to the shell 8, the upper side wall of the shell 8 is provided with an inlet and an outlet, the inlet and outlet of the shell 8 are respectively provided with a one-way valve 10, the upper part of the shell 8 is fixedly provided with an electron emission gun 9, the rotating shaft 7 is connected to the ring gear 3 through a bearing, and the ring gear 3 is evenly provided with more than two connecting rod combinations, the connecting rod combination includes a first connecting rod 4 and a second connecting rod 5, the first connecting rod 4 and the second connecting rod 5 form an inward broken line shape, in The space is saved without affecting the operation of the device. The lower end of the shell 8, the first connecting rod 4, the second connecting rod 5, and the upper end of the ring gear 3 are hinged in sequence. The ring gear 3 is meshed 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 shell 8 to rotate through the connecting rod combination. During the rotation process, the lifting and lowering of the shell 8 is achieved by the cooperation of the internal and external threads, so that the electron emission gun 9 rotates and irradiates the solder. At the same time, the oxide layer has a thickness. As the surface of the oxide layer is reduced, the shell 8 descends to bring the electron emission gun 9 closer to the internal oxide surface under the surface of the oxide layer, reducing the influence of the thickness on the reduction of the oxide layer, ensuring that the oxide layer is irradiated uniformly in the horizontal and vertical directions, and improving the irradiation efficiency. The gas can be introduced through the inlet and outlet according to the experimental requirements to adjust the pressure. The base 6 remains stationary and provides sufficient placement space, which is convenient for irradiation and is suitable for solders of various shapes and forms.

[0039] The following steps are involved:

[0040] Step 2.1: Place the oxidized solder in an 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 surface of the Sn-based solder sample by atomic sputtering of the metal base during electron irradiation;

[0041] Step 2.2: using electrons emitted by an electron emission gun to perform electron irradiation treatment on the surface of the oxidized base solder sample;

[0042] Step 2.3: Obtain reduced solder.

[0043] Specific implementation method four: Combination Figure 1-2The present embodiment is described. The present embodiment is a method for electron irradiation reduction of Sn-based solder metal nanocrystals. In step 2.1, the glass plate is a single-sided conductive glass plate with a length and width of 5 cm and a thickness of 5 mm. 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 electron irradiation metal base by conductive tape to reduce the accumulated charge on the surface of the glass plate. 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 the irradiation process.

[0044] Specific implementation method five: Combination Figure 1-2 This embodiment is described. This embodiment is a method for reducing Sn-based solder metal nanocrystals by electron irradiation. In step 2.2, electron irradiation is performed under normal temperature and pressure air conditions. During the electron irradiation process, the electron energy of the electron emission gun 9 is 200KeV~10MeV, and the electron irradiation injection rate is 1e11e / cm 2 ·s~2e12 e / cm 2 ·s, the total electron irradiation dose is 5e15 e / cm 2 ~2e16 e / cm 2 ; Select electron irradiation injection rate of 1e11e / cm 2 ·s~2e12 e / cm 2 ·s, the total electron irradiation dose is 5e15 e / cm 2 ~2e16 e / cm 2 The Sn-based solder sample was irradiated with any combination of dose rate and total injection in the range, injection rate×time=total injection.

[0045] Specific implementation method six: Combination Figure 1-2 The present embodiment is described. A method for reducing Sn-based solder metal nanocrystals by electron irradiation is provided in the present embodiment. The method for reducing Sn-based solder metal nanocrystals by electron irradiation is applied to the reduction of Sn-based solder (solder sample).

[0046] Specific implementation method seven: Combination Figure 1 The present embodiment is described as follows: a method for reducing Sn-based solder metal nanocrystals by electron irradiation, wherein the Sn-based solder is SnAg, 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 CuC2 Sn a2 Pb b2 Sb C2 One or more alloys.

[0047] Specific implementation method eight: Combination Figure 1 To illustrate the present embodiment, a method for electron irradiation reduction of Sn-based solder metal nanocrystals is provided in the present embodiment, wherein a1, a2, b1, b2, and c2 correspond to the mass percentage content of atoms of each element, respectively, 50%≤a1≤100%, 50%≤a2≤100%, 0%≤b1≤50%, 0%≤b2≤50%, 0%≤c2≤50%, a1+b1=100%, a2+b2+c2=100%.

[0048] Specific implementation method nine: Combination Figure 1 The present embodiment is described as a method for electron irradiation reduction of Sn-based solder metal nanocrystals, wherein the solder is in the form of one or more of flakes, wires, spheres, blocks, powders, columns, foils or pastes.

[0049] Specific implementation method ten: Combination Figure 1 The present embodiment is described as a method for reducing Sn-based solder metal nanocrystals by electron irradiation. For sheet and / or block solders, the length, width and thickness are all less than or equal to 1 cm. For filamentary solders, the diameter is 50 nm to 100 μm.

[0050] Embodiment 1:

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

[0052] Step 1: Prepare a SnPb eutectic solder joint sample with natural oxidation on the surface;

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

[0054] Put the SnPb eutectic solder joint sample and the conductive glass plate into the electron accelerator device and align the sample with the center of the electron acceleration gun; start the electron accelerator and select the electron irradiation injection rate of 1e12 e / cm 2 ·s, the total electron irradiation dose is 2e16 e / cm 2 The Sn-based solder samples were irradiated;

[0055] See also Figure 1As shown in Figure (d), the selected area electron diffraction pattern after oxidation shows diffraction spots corresponding to β-Sn and polycrystalline diffraction rings corresponding to SnO2; as shown in Figure (e), after a total injection of 2e16 e / cm 2 After electron irradiation of 2e16 e / cm, the polycrystalline diffraction rings corresponding to SnO2 in the selected area electron diffraction pattern disappeared, and only the diffraction spots corresponding to β-Sn remained; this indicates that after a total injection of 2e16 e / cm 2 After electron irradiation, SnO2 in the SnPb eutectic solder joint is reduced to β-Sn; the reduction rate of the surface oxide of the Sn-based solder is greater than 90%. The present invention provides a method for reducing the surface oxide of the Sn-based solder by electron irradiation. By irradiating the surface of the Sn-based solder with electrons, the oxide layer on the surface of the Sn-based solder can be reduced. Compared with the traditional oxide chemical reduction method and mechanical cleaning method, the method has the advantages of no environmental pollution, strong controllability, no introduction of impurities, ability to reduce the surface oxide of the 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 arranged and combined, and those skilled in the art can exhaust all possibilities based on the mathematical knowledge of arrangement and combination. Therefore, the present invention will no longer describe the technical solutions after arrangement and combination one by one, but it should be understood that the technical solutions after arrangement and combination have been disclosed by the present invention.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for reducing Sn-based solder metal nanocrystals by electron irradiation, characterized in that: The following steps are involved: Step 1: Prepare oxidized solder; Step 2: Electron irradiation of the oxidized solder.

2. The method for reducing Sn-based solder metal 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 to obtain a solder having an oxide layer.

3. The method for reducing Sn-based solder metal nanocrystals by electron irradiation according to claim 1 or 2, characterized in that: Step 2 includes the following steps: Step 2.1: Align the oxidized solder to the center of the electron emission gun and place a glass plate between the oxidized solder and the base; Step 2.2: Electron irradiating the oxidized base solder sample; Step 2.3: Obtain reduced solder.

4. The method for reducing Sn-based solder metal nanocrystals by electron irradiation according to claim 3, characterized in that: In step 2.1, the glass plate is a single-sided conductive glass plate with a thickness of 5 mm, the base is a metal base, and the conductive surface of the glass is connected to the metal base through a conductive tape.

5. The method for reducing Sn-based solder metal nanocrystals by electron irradiation according to claim 4, characterized in that: In step 2.2, during the electron irradiation process, the electron energy is 200KeV~10MeV, and the electron irradiation injection rate is 1e11e / cm 2 ·s~2e12 e / cm 2 ·s, the total electron irradiation dose is 5e15 e / cm 2 ~2e16 e / cm 2 .

6. The method for reducing Sn-based solder metal nanocrystals by electron irradiation according to claim 5, characterized in that: A method for reducing Sn-based solder metal nanocrystals by electron irradiation is applied to the reduction of Sn-based solder.

7. The method for reducing Sn-based solder metal nanocrystals by electron irradiation according to claim 6, characterized in that: Sn-based solder is SnAg, 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 alloys.

8. The method for reducing Sn-based solder metal nanocrystals by electron irradiation according to claim 7, characterized in that: a1, a2, b1, b2, c2 correspond to the mass percentage content of each element atom, respectively, 50%≤a1≤100%, 50%≤a2≤100%, 0%≤b1≤50%, 0%≤b2≤50%, 0%≤c2≤50%.

9. The method for reducing Sn-based solder metal nanocrystals by electron irradiation according to claim 6, characterized in that: The solder is in the form of one or more of flake, filament, sphere, block, powder, column, foil or paste.

10. The method for reducing Sn-based solder metal nanocrystals by electron irradiation according to claim 9, characterized in that: For sheet-shaped and / or block-shaped solder, the length, width and thickness are all less than or equal to 1 cm. For filament-shaped solder, the diameter is 50 nm to 100 μm.

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