Pretreatment process for improving wettability of fluid on surface of metal tungsten filament

Abstract

Compared with the prior art, the pretreatment process for improving the wettability of the fluid on the surface of the metal tungsten filament has the advantages that an oxide layer on the surface of the tungsten filament is removed through washing liquid cleaning, vacuum preheating and the like, meanwhile, the tungsten filament is prevented from being oxidized again in a nitrogen environment, and cooling parameters are adjusted; the coverage rate and the coverage uniformity of the surface fluid are improved, the surface wettability of the metal tungsten is effectively improved, the liquid metal adhesion capacity in a long-time working state is improved, the stable working performance of an electrode emission system is improved, and the purpose of the invention is achieved.

Description

Technical Field

[0001] The invention relates to a process for removing an oxide layer and cleanly infiltrating the surface, and in particular to a pretreatment process for improving the wettability of a metal tungsten wire surface by a fluid. Background Art

[0002] The oxide layer (WO3, WO2 and intermediate oxide WO) is formed on the surface of the metal tungsten. n , where n is between 2-3), tungsten oxide seriously affects the wettability of the tungsten surface, affecting the fluid uniformity and coverage of the surface.

[0003] Improving the surface wettability of metal tungsten can improve the adhesion of liquid metal under long-term working conditions and enhance the stable working performance of the electrode emission system.

[0004] Therefore, a pretreatment process for improving the surface wettability of tungsten metal wire by fluid is particularly needed to solve the above-mentioned existing problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a pretreatment process for improving the surface wettability of metal tungsten wire by fluid. In view of the shortcomings of the existing technology, the present invention effectively removes the oxide layer on the surface of the tungsten wire, protects the tungsten wire from re-oxidation in a nitrogen environment, adjusts the cooling parameters, and improves the coverage rate and uniformity of the surface fluid.

[0006] The technical problem solved by the present invention can be achieved by adopting the following technical solutions: A pretreatment process for improving the surface wettability of a metal tungsten wire by a fluid comprises the following steps: S1. Soaking in cleaning solution: Soak the tungsten wire in cleaning solution for 10-20 minutes to remove surface impurities and part of the oxide layer. S2. Ultrasonic cleaning: The tungsten filament is immersed in the cleaning solution and cleaned in an ultrasonic cleaning machine for 10-20 minutes at a frequency of 40-60 kHz and a temperature of 30±3°C to disperse impurities on the surface of the tungsten filament into the solvent. After ultrasonic cleaning, it is rewashed with pure water. S3, Nitrogen drying: The tungsten filament after ultrasonic cleaning is placed in a nitrogen environment until it is completely dry, avoiding contact with oxygen; S4, vacuum preheating: at 5×10 -4 -1×10 -1 Under the vacuum degree of Pa, the tungsten wire external electrode is heated after being energized. The power supply is in OVP mode, the voltage range is 0.80-1.05V, and the heating time is 10-20 minutes. S5. Fluid Immersion: Immerse the vacuum preheated tungsten wire in the fluid. The tungsten wire maintains a reciprocating motion in the fluid. The displacement of the up and down uniform motion is 1-2 cm. The movement from top to bottom is one cycle. Each cycle lasts for 5-15 seconds. After 5-10 reciprocating cycles, the tungsten wire is lifted. S6. Gradient cooling: The tungsten filament is cooled by introducing nitrogen into the environment to control the gradient cooling process. The mechanical pump is disconnected and the nitrogen flow rate is maintained at 10-15L / min for 15-20s; the flow rate is increased to 20-25L / min and maintained for 15-20s; the nitrogen flow rate is enlarged to 40-45L / min and finally restored to the atmospheric environment. Wait for 9-10 minutes; in the atmospheric environment, the tungsten filament after improved infiltration can be stored in a refrigerated environment at 4°C.

[0007] In a preferred embodiment of the present invention, in step S1, the washing solution comprises the following components in mass percentage: 0.1%-3% hydrogen peroxide, 0.1%-3% Group IA metal hydroxide, 0.1%-3% ammonia water, 0.1%-3% monohydric alcohol, and the solvent is deionized water.

[0008] In a preferred embodiment of the present invention, the fluid includes liquid metal gallium, liquid metal rubidium and liquid metal cesium.

[0009] Compared with the prior art, the pretreatment process for improving the surface wettability of a metal tungsten wire by the present invention removes the oxide layer on the surface of the tungsten wire by means of cleaning with a lotion and vacuum preheating, while preventing the tungsten wire from being oxidized again in a nitrogen environment. The cooling parameters are adjusted to increase the coverage rate and uniformity of the surface fluid, thereby effectively improving the surface wettability of the metal tungsten and improving the emission performance and service life of the emission tip at the front end of the emission electrode of a focused ion beam (FIB) system, thereby achieving the purpose of the present invention.

[0010] The features of the present invention can be clearly understood by referring to the drawings and the following detailed description of preferred embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a schematic diagram of the fluid infiltration process of the present invention; Figure 2 Schematic diagram of voltage-current parameters of the vacuum preheating power supply of the present invention; Figure 3 Schematic diagram of the coverage uniformity of the present invention. DETAILED DESCRIPTION

[0012] In order to make the technical means, creative features, objectives and effects achieved by the present invention easier to understand, the present invention is further described below with reference to specific illustrations. Example 1

[0013] The pretreatment process of improving the surface wettability of the metal tungsten wire by fluids in this embodiment includes the following steps: S1. Soaking in cleaning solution: Soak the tungsten wire in cleaning solution for 10 minutes to remove surface impurities and part of the oxide layer. S2. Ultrasonic cleaning: The tungsten filament immersed in the cleaning solution is cleaned in an ultrasonic cleaning machine for 20 min at a frequency of 40 kHz and a temperature of 30 ± 3 °C to disperse the impurities on the surface of the tungsten filament into the solvent. After the ultrasonic cleaning is completed, it is re-washed with pure water; S3, Nitrogen drying: After ultrasonic cleaning, the tungsten filament is placed in a nitrogen environment until it is completely dry, avoiding contact with oxygen; S4, vacuum preheating: (6±1)×10 -4 Under the vacuum degree of Pa, the tungsten wire external electrode is powered on and heated. The power supply is in OVP mode, the voltage range is 1.00-1.05V, and the voltage is increased by 0.5V every 5 minutes. The heating time is 10 minutes. S5. Fluid Immersion: Immerse the vacuum preheated tungsten wire in the fluid. The tungsten wire maintains a reciprocating motion in the fluid, with a uniform up and down displacement of 2 cm. One cycle is from top to bottom, and each cycle lasts about 5 seconds. After 5 reciprocating cycles, the tungsten wire is lifted. S6, Gradient cooling: The tungsten filament is cooled by introducing nitrogen into the environment to control the gradient cooling process. The mechanical pump is disconnected and the nitrogen flow rate is maintained at 10 L / min for 20 seconds. The flow rate is increased to 20 L / min and maintained for 20 seconds. The nitrogen flow rate is increased to 40 L / min and finally restored to the atmospheric environment. Wait for 10 minutes. The washing liquid comprises 3% hydrogen peroxide, 3% Group IA metal hydroxide, 3% ammonia water, and 3% monohydric alcohol, and the solvent is deionized water. Example 2

[0014] The pretreatment process of improving the surface wettability of the metal tungsten wire by fluids in this embodiment includes the following steps: S1. Soaking in cleaning solution: Soak the tungsten wire in cleaning solution for 15 minutes to remove surface impurities and part of the oxide layer. S2. Ultrasonic cleaning: The tungsten filament immersed in the cleaning solution is cleaned in an ultrasonic cleaning machine for 15 minutes at a frequency of 60 kHz and a temperature of 30 ± 3 °C to disperse the impurities on the surface of the tungsten filament into the solvent. After the ultrasonic cleaning is completed, the tungsten filament is rewashed with pure water. S3, Nitrogen drying: After ultrasonic cleaning, the tungsten filament is placed in a nitrogen environment to dry and avoid contact with oxygen; S4, vacuum preheating: (8±1)×10 -3 Under a vacuum degree of Pa, the tungsten wire external electrode was heated after being energized. The power supply was in OVP mode, with a voltage range of 0.8-0.9V. The voltage was increased by 0.5V every 4 minutes, and the heating time was 12 minutes. S5. Fluid Immersion: Immerse the vacuum preheated tungsten wire in the fluid. The tungsten wire maintains a reciprocating up and down motion in the fluid. The up and down displacement is 1 cm. The movement from top to bottom is one cycle. Each cycle lasts about 15 seconds. After 8 reciprocating cycles, the tungsten wire is lifted. S6, Gradient cooling: The tungsten filament is cooled by introducing nitrogen into the environment to control the gradient cooling process. The mechanical pump is disconnected and the nitrogen flow rate is maintained at 12 L / min for 15 seconds. The flow rate is increased to 23 L / min and maintained for 15 seconds. The nitrogen flow rate is then increased to 45 L / min and finally restored to the atmospheric environment. Wait for 9 minutes. The washing liquid comprises 3% hydrogen peroxide, 3% Group IA metal hydroxide, 3% ammonia water, and 3% monohydric alcohol, and the solvent is deionized water. Example 3

[0015] The pretreatment process of improving the surface wettability of the metal tungsten wire by fluids in this embodiment includes the following steps: S1. Soaking in cleaning solution: Soak the tungsten wire in cleaning solution for 20 minutes to remove surface impurities and part of the oxide layer. S2. Ultrasonic cleaning: The tungsten filament immersed in the cleaning solution is cleaned in an ultrasonic cleaning machine for 10 min at a frequency of 60 kHz and a temperature of 30 ± 3 °C to disperse the impurities on the surface of the tungsten filament into the solvent. After the ultrasonic cleaning is completed, the tungsten filament is rewashed with pure water. S3, Nitrogen drying: After ultrasonic cleaning, the tungsten filament is placed in a nitrogen environment until it is completely dry, avoiding contact with oxygen; S4, vacuum preheating: at (9±1)×10 -2 Under the vacuum degree of Pa, the tungsten wire external electrode was heated after being energized. The power supply was in OVP mode, with a voltage range of 0.80-1.00 V, and the voltage was increased by 0.5 V every 4 minutes. The heating time was 20 minutes. S5. Fluid Immersion: Immerse the vacuum preheated tungsten wire in the fluid. The tungsten wire maintains a reciprocating up and down motion in the fluid. The up and down displacement is 2 cm. The movement from top to bottom is one cycle. Each cycle lasts about 10 seconds. After 8 reciprocating cycles, the tungsten wire is lifted. S6, Gradient cooling: The tungsten filament is cooled by introducing nitrogen into the environment to control the gradient cooling process. The mechanical pump is disconnected and the nitrogen flow rate is maintained at 15 L / min for 15 seconds. The flow rate is increased to 25 L / min and maintained for 18 seconds. The nitrogen flow rate is increased to 42 L / min and finally restored to the atmospheric environment. Wait for 10 minutes. The washing liquid comprises 0.1% hydrogen peroxide, 0.1% Group IA metal hydroxide, 0.1% ammonia water, 0.1% monohydric alcohol, and the solvent is deionized water.

[0016] The effects of the present invention and the prior art are compared as follows: Example Infiltration method Coverage Coverage uniformity Example 1 Vacuum short-time preheating - fast transmission - low-speed flow gradient cooling 100% Uniform cover thickness Example 2 Short-time preheating in vacuum - slow transmission - medium-speed flow gradient cooling 100% Uniform cover thickness Example 3 Vacuum long-time preheating-medium speed transmission-high speed flow gradient cooling 100% Uniform cover thickness Existing technology Atmospheric pressure touch wetting 80-90% Large thickness deviation The basic principles, main features and advantages of the present invention are shown and described above. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention, which is defined by the appended claims and their equivalents.

Claims

1. A pretreatment process for improving the surface wettability of a metal tungsten wire by a fluid, characterized in that: The steps include: S1. Soaking in washing liquid: Soak the metal tungsten wire in washing liquid for 10-15 minutes to wash away surface impurities and part of the oxide layer; S2. Ultrasonic cleaning: clean the tungsten wire immersed in the cleaning solution in an ultrasonic cleaning machine for 10-20 min at a frequency of 40-60KHz and a temperature of 30±3℃ to disperse the impurities on the surface of the tungsten wire into the solvent. After the ultrasonic cleaning is completed, rewash with pure water; S3, Nitrogen drying: The tungsten wire after ultrasonic cleaning is placed in a nitrogen environment to dry to avoid contact with oxygen; S4, vacuum preheating: at 5×10 -4 -1×10 -1 Under the vacuum degree of Pa, the tungsten wire external electrode is energized and heated. When the power supply is in OVP mode, the voltage range is 0.80-1.05V and the heating time is 10-20min. S5. Fluid infiltration: The vacuum preheated tungsten wire is immersed in the fluid. The tungsten wire keeps moving up and down in the fluid. The displacement of the up and down uniform motion is 1-2 cm. The movement from top to bottom is one cycle. Each cycle lasts for 5-10 seconds. After 5-10 cycles, the tungsten wire is lifted. S6, Gradient cooling: The tungsten filament controls the gradient cooling process by introducing nitrogen flow into the environment, disconnecting the mechanical pump, and maintaining the nitrogen flow rate at 10-15 L / min for 15-20 seconds; increase the flow rate to 20-25 L / min and maintain it for 15-20 seconds; The nitrogen flow rate is increased to 40-45 m / s, and finally restored to the atmospheric environment, and waited for 9-10 minutes; under the atmospheric environment, the tungsten wire after improved infiltration can be stored in a refrigerated environment at 4°C.

2. The pretreatment process for improving the surface wettability of a metal tungsten wire according to claim 1, characterized in that: In step S1, the washing liquid includes the following components in mass percentage: 0.1%-3% hydrogen peroxide, 0.1%-3% Group IA metal hydroxide, 0.1%-3% ammonia water, 0.1%-3% monohydric alcohol, and the solvent is deionized water.

3. The pretreatment process for improving the surface wettability of a metal tungsten wire according to claim 1, characterized in that: The fluid includes liquid metal gallium, liquid metal rubidium and liquid metal cesium.

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