Cleaning method for welding heat radiator of miniaturized space traveling wave tube after lead-tin-silver welding

Abstract

The invention discloses a cleaning method for a welding heat radiator of a miniaturized space traveling wave tube after lead-tin-silver welding. The cleaning method comprises the following steps of rough cleaning for oil removal, fine cleaning for dust removal, acid pickling, physical polishing, acetone ultrasonic treatment, pure water washing, nitrogen blow-drying and the like. According to the lead-tin-silver solder, the lead-tin-silver solder can reach the use indexes of being clean in appearance and free of oxidation and dirt, the use requirement for the lead-tin-silver solder when a space traveling wave tube is used for welding a heat radiator is met, the sealing quality during welding is improved, and therefore the working reliability and stability of the traveling wave tube are guaranteed.

Description

Technical Field

[0001] The invention relates to a method for cleaning a miniaturized space traveling wave tube welding heat radiator after lead-tin-silver welding. Background Art

[0002] As a vital component of the heat dissipation system of the space traveling wave tube, the heat radiator is used to conduct the heat generated at the collector through radiation, effectively reducing the working temperature of the space traveling wave tube and ensuring its normal operation. At present, the welding of the heat radiator and the collector assembly of the miniaturized space traveling wave tube is carried out by soft soldering, and the solder used is lead-tin-silver material. Therefore, its sealing quality directly affects the working efficiency, life and reliability of the space traveling wave tube.

[0003] Solder plays a vital role in the welding process. The surface state of the solder directly affects the sealing strength. The research on the surface cleaning process of lead-tin-silver solder is of great significance to the quality of thermal radiator welding.

[0004] At present, there are two difficulties in the surface cleaning process of lead-tin-silver solder: First, a large amount of black floating dust remains on the surface of the solder. After the degreasing step using traditional alkaline detergent solution, the floating dust cannot be effectively removed, affecting the subsequent cleaning. Second, the solder is mechanically processed by electromachining. After the processing is completed, the surface is very easy to oxidize and blacken. The black oxide layer produced by electromachining is extremely difficult to clean. If there is a residual black oxide layer on the surface, it will directly affect the fluidity of the solder during welding. Therefore, it is necessary to master the surface cleaning process of lead-tin-silver solder in order to achieve high-reliability sealing of the thermal radiator. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to track and analyze the materials and mechanical processing process of lead-tin-silver solder. After a large number of experiments, it is concluded that through the steps of rough washing and degreasing, water washing, fine washing and deashing, water washing, acid washing, water washing, physical polishing, acetone ultrasound, pure water washing, and drying, the lead-tin-silver solder can reach the use indicators of clean appearance, no oxidation, and no dirt, meet the use requirements of lead-tin-silver solder when welding thermal radiators of space traveling wave tubes, improve the sealing quality during welding, and thus ensure the working reliability and stability of the traveling wave tube.

[0006] The cleaning method of the miniaturized space traveling wave tube welding heat radiator after lead-tin-silver welding provided by the present invention realizes high-reliability sealing between the heat radiator and the collector assembly.

[0007] The core technologies of the present invention mainly include four points. The first point is to further refine the alkaline cleaning ultrasonic process and divide the traditional one-step ultrasonic cleaning into two steps. First, the first step is to use an alkaline cleaning solution with good degreasing effect for ultrasonic treatment to remove oil stains introduced by mechanical processing. The second step is to use an alkaline cleaning solution with good dust removal effect to remove stubborn dust remaining on the surface. The second point is to use a mixed acid pickling method to remove the surface oxide layer, and add specific corrosion inhibitors and brighteners to effectively remove surface oxidation and avoid excessive corrosion, while ensuring the brightness of the surface. The third point is to use physical polishing to polish the surface of the parts to make the surface smooth and bright. The fourth point is to use pure water ultrasonic cleaning to ensure the cleanliness of the solder surface. Through the above four core technologies, a lead-tin-silver solder with a bright surface, no oxidation, no blackening, and high cleanliness is prepared.

[0008] In order to achieve the above purpose, the technical solution adopted by the present invention is: A cleaning method for a miniaturized space traveling wave tube welding heat radiator after lead-tin-silver welding, the process steps of which include: rough washing and degreasing, water washing, fine washing and deashing, water washing, acid washing, water washing, physical polishing, acetone ultrasound, pure water washing, nitrogen drying, and inspection.

[0009] In order to describe this application in more detail, it specifically includes the following steps: 1. Rough washing and degreasing Lead-tin-silver solder is processed by electro-machining, which will introduce a lot of oil and dirt on the surface. Therefore, it is necessary to use an alkaline cleaning solution with good degreasing effect (the alkaline cleaning solution is made of the following raw materials in mass percentage: 20% sodium hydroxide, 10% sodium carbonate, 10% sodium metasilicate pentahydrate, 10% surfactant, and the balance is water), and use ultrasonic equipment to perform ultrasonic treatment on the surface of the parts to achieve the purpose of removing the oil on the solder surface. At a temperature of 40~60℃, after 30 minutes of ultrasonic treatment, the surface oil basically disappears.

[0010] 2. Fine washing and dust removal After the rough cleaning and degreasing step, a small amount of black floating dust will remain on the surface of the lead-tin-silver solder. Therefore, it is necessary to replace it with an alkaline cleaning agent solution with good dust removal effect (the alkaline cleaning agent solution is made of the following raw materials in mass percentage: 20% sodium hydroxide, 10% sodium carbonate, 10% sodium metasilicate pentahydrate, 10% surfactant, and the balance is water) and use ultrasonic equipment to further ultrasonically treat the surface of the parts to achieve the purpose of removing the stubborn floating dust remaining on the solder surface. After 60 minutes of ultrasonic treatment at a temperature of 40~60℃, the surface floating dust basically disappears.

[0011] 3. Pickling After mechanical processing, the lead-tin-silver solder will form a very thick oxide layer on the surface, so it is necessary to use a strong acid solution to remove surface oxidation. Nitric acid, as a kind of inorganic strong acid with strong oxidizing property, can effectively remove the surface oxide layer, and a certain concentration of hydrofluoric acid is added at the same time, and some insoluble dirt can be removed. Both have good synergistic ability, so nitric acid is selected as the main body and a certain concentration of hydrofluoric acid mixed solution is added at the same time, as the main component. At the same time, in order to prevent excessive corrosion during pickling, causing size over-tolerance, a specific corrosion inhibitor needs to be added, and the present invention adds a certain concentration of ammonium molybdate to prevent excessive corrosion. In the process of chemical corrosion, the brightness of the solder surface will deteriorate, which is usually manifested as blackening of parts. Therefore, in order to increase the brightness of the surface, the present invention adds a certain concentration of glycerol to improve the surface brightness during pickling and chemical polishing. The specific pickling solvent composition includes nitric acid: 400ml / L~600ml / L, hydrofluoric acid: 20 ml / L~30ml / L, ammonium molybdate: 0.1~0.15g / L, and glycerol: 0.1~0.15g / L.

[0012] 4. Physical polishing After the pickling step is completed, some pits will remain on the solder surface, causing the surface to be rough and affecting the reliability of the subsequent welding process. Therefore, the solder surface needs to be leveled. Physical polishing is a method of polishing and leveling the surface of parts by physical grinding. At the same time, the size consumed during the polishing process is controllable, so physical polishing is used for surface treatment. The abrasive is selected as corundum, and ultrasonic equipment is used to use the energy of ultrasonic waves to achieve mutual grinding between corundum and the solder surface. After polishing for 60 minutes, the solder surface is smooth and bright, emitting a silver-white metallic luster.

[0013] 5. Acetone Ultrasound Acetone solution has strong cleaning ability and can effectively remove organic compounds and inorganic salts on the surface of solder. Therefore, using acetone solution for ultrasonic treatment for 10-15 minutes can effectively remove organic compounds and inorganic salts on the surface of lead-tin-silver solder and ensure the cleanliness of the surface.

[0014] 6. Pure water cleaning Using pure water with a resistivity of 15~18MΩ·cm in combination with ultrasonic equipment for cleaning can effectively reduce the number of particles on the surface of lead-tin-silver solder and further improve the surface cleanliness of parts.

[0015] 7. Nitrogen drying Use high-purity nitrogen to purge the surface of the parts to remove surface moisture and excess matter.

[0016] 8. Inspection When observing the lead-tin-silver solder after cleaning under an optical microscope, the surface should have a silvery white metallic luster and no black oxide residue should appear.

[0017] Beneficial effects: The cleaning method of the miniaturized space traveling wave tube welding heat radiator after lead-tin-silver welding provided by the present invention has the following main innovations: First, the traditional one-step ultrasonic cleaning is divided into two steps. First, the first step is to use an alkaline cleaning solution with good degreasing effect for ultrasonic treatment to remove the oil introduced by mechanical processing. The second step is to use an alkaline cleaning solution with good deashing effect to remove the stubborn floating dust remaining on the surface. Second, in the pickling step, in order to effectively remove the oxide layer on the surface of the solder, a mixed acid solution with better effect than a single type of acid is used to remove the oxide layer on the surface more thoroughly. At the same time, in order to prevent excessive corrosion during the pickling process and cause dimensional deviation, a specific corrosion inhibitor ammonium molybdate and a brightener glycerol are added, which can effectively control the reaction rate and increase the brightness of the surface. Third, after the surface oxidation is removed by pickling, some pits will be left on the solder surface. Therefore, physical polishing is used for surface treatment. Diamond sand is used in combination with ultrasonic equipment. Through physical grinding of diamond sand and the solder surface, the solder surface is smooth and bright, thereby meeting the high reliability requirements of the miniaturized space traveling wave tube welding heat radiator. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Photo of the heat radiator for welding miniaturized space traveling wave tube for lead-tin-silver welding before cleaning.

[0019] Figure 2 Photo of the cleaning of the heat radiator used for welding miniaturized space traveling wave tubes for lead-tin-silver welding. DETAILED DESCRIPTION

[0020] The present invention is further explained below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0021] Example 1 A method for cleaning a miniaturized space traveling wave tube welding heat radiator after lead-tin-silver welding, comprising the following steps: (1) Rough washing and degreasing An alkaline cleaning agent solution (the alkaline cleaning agent solution is made of the following raw materials in percentage by mass: 20% sodium hydroxide, 10% sodium carbonate, 10% sodium metasilicate pentahydrate, 10% surfactant, and the balance is water) is used in combination with ultrasonic equipment to perform ultrasonic treatment for 30 minutes at a temperature of 40~60°C to achieve the purpose of removing oil stains on the solder surface.

[0022] (2) Fine washing and dust removal An alkaline cleaning solution (the alkaline cleaning solution is made of the following raw materials in percentage by mass: 20% sodium hydroxide, 10% sodium carbonate, 10% sodium metasilicate pentahydrate, 10% surfactant, and the balance is water) is used in combination with ultrasonic equipment to perform ultrasonic treatment for 60 minutes at a temperature of 40-60°C, and further ultrasonic treatment is performed on the surface of the parts to achieve the purpose of removing stubborn floating ash remaining on the surface of the solder.

[0023] (3) Pickling After mechanical processing, the lead-tin-silver solder will form a very thick oxide layer on the surface, so it is necessary to use a strong acid solution to remove surface oxidation. Nitric acid, as a kind of inorganic strong acid with strong oxidizing property, can effectively remove the surface oxide layer, and a certain concentration of hydrofluoric acid is added at the same time, and some insoluble dirt can be removed. Both have good synergistic ability, so nitric acid is selected as the main body and a certain concentration of hydrofluoric acid mixed solution is added at the same time, as the main component. At the same time, in order to prevent excessive corrosion during pickling, causing size over-tolerance, a specific corrosion inhibitor needs to be added, and the present invention adds a certain concentration of ammonium molybdate to prevent excessive corrosion. In the process of chemical corrosion, the brightness of the solder surface will deteriorate, which is usually manifested as blackening of parts. Therefore, in order to increase the brightness of the surface, the present invention adds a certain concentration of glycerol to improve the surface brightness during pickling and chemical polishing. The specific pickling solvent composition includes nitric acid: 400ml / L~600ml / L, hydrofluoric acid: 20 ml / L~30ml / L, ammonium molybdate: 0.1~0.15g / L, and glycerol: 0.1~0.15g / L.

[0024] (4) Physical polishing The abrasive is corundum, and ultrasonic equipment is used to utilize the energy of ultrasound to achieve mutual grinding between the corundum and the solder surface. After polishing for 60 minutes, the solder surface is smooth and bright, emitting a silvery-white metallic luster.

[0025] (5) Acetone ultrasound Using acetone solution for 10 minutes of ultrasound can effectively remove organic compounds and inorganic salts on the surface of lead-tin-silver solder to ensure the cleanliness of the surface.

[0026] (6) Pure water cleaning Using pure water with a resistivity of 15~18MΩ·cm in combination with ultrasonic equipment for cleaning can effectively reduce the number of particles on the surface of lead-tin-silver solder and further improve the surface cleanliness of parts.

[0027] Photos of the lead-tin-silver soldered miniaturized space traveling wave tube welding heat radiator provided by the present invention before and after cleaning, respectively, as shown in FIG. Figure 1 and Figure 2As shown. The lead-tin-silver solder can meet the use indicators of clean appearance, no oxidation, and no dirt, meet the use requirements of lead-tin-silver solder when welding thermal radiators of space traveling wave tubes, and can greatly improve the sealing quality during welding, thereby ensuring the reliability and stability of the traveling wave tube.

[0028] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for cleaning a miniaturized space traveling wave tube welding heat radiator after lead-tin-silver welding, characterized in that: The method comprises the following steps: rough washing and degreasing, fine washing and deashing, pickling, physical polishing, acetone ultrasound, pure water washing and nitrogen drying.

2. The cleaning method of a miniaturized space traveling wave tube welding heat radiator after lead-tin-silver welding according to claim 1 is characterized in that: The rough cleaning and degreasing adopts alkaline detergent solution and ultrasonic equipment to perform ultrasonic treatment on the surface of the parts to achieve the purpose of removing oil stains on the solder surface.

3. The cleaning method of a miniaturized space traveling wave tube welding heat radiator after lead-tin-silver welding according to claim 2 is characterized in that: The alkaline cleaning agent solution is made of the following raw materials in percentage by mass: 20% sodium hydroxide, 10% sodium carbonate, 10% sodium metasilicate pentahydrate, 10% surfactant, and the balance is water. After ultrasonic treatment for 30 minutes at a temperature of 40-60°C, the surface oil stains basically disappear.

4. The cleaning method of a miniaturized space traveling wave tube welding heat radiator after lead-tin-silver welding according to claim 1 is characterized in that: The fine cleaning and deashing is to use alkaline detergent solution and ultrasonic equipment to further ultrasonically treat the surface of the parts to achieve the purpose of removing the stubborn floating dust remaining on the surface of the solder.

5. The cleaning method of a miniaturized space traveling wave tube welding heat radiator after lead-tin-silver welding according to claim 4 is characterized in that: The alkaline cleaning agent solution is made of the following raw materials in percentage by mass: 20% sodium hydroxide, 10% sodium carbonate, 10% sodium metasilicate pentahydrate, 10% surfactant, and the balance is water. After ultrasonic treatment for 60 minutes at a temperature of 40-60°C, the floating dust on the surface basically disappears.

6. The cleaning method of a miniaturized space traveling wave tube welding heat radiator after lead-tin-silver welding according to claim 1 is characterized in that: The pickling solvent includes: nitric acid: 400ml / L~600ml / L, hydrofluoric acid: 20 ml / L~30 ml / L, Ammonium molybdate: 0.1~0.15g / L, glycerol: 0.1~0.15g / L.

7. The cleaning method of a miniaturized space traveling wave tube welding heat radiator after lead-tin-silver welding according to claim 1 is characterized in that: In the physical polishing, corundum is selected as abrasive, and ultrasonic equipment is used to utilize the energy of ultrasonic waves to achieve mutual grinding between corundum and the solder surface. After polishing for 10 to 60 minutes, the solder surface is smooth and bright, emitting a silvery-white metallic luster.

8. The method for cleaning a miniaturized space traveling wave tube welding heat radiator after lead-tin-silver welding according to claim 1, characterized in that: The acetone ultrasound is to use acetone solution ultrasound for 10-15 minutes, which can effectively remove organic compounds and inorganic salts on the surface of the lead-tin-silver solder to ensure the cleanliness of the surface.

9. The method for cleaning a miniaturized space traveling wave tube welding heat radiator after lead-tin-silver welding according to claim 1, characterized in that: Pure water cleaning uses pure water with a resistivity of 15~18MΩ·cm in combination with ultrasonic equipment to effectively reduce the number of particles on the surface of lead-tin-silver solder and further improve the surface cleanliness of parts.

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