A surface cleaning method for metal tantalum before welding

Abstract

This invention discloses a surface cleaning method for tantalum metal before welding, relating to the field of metal processing technology. The cleaning method includes the following steps: mixing tantalum metal with a cleaning agent and then cleaning; the cleaning agent is composed of the following raw materials in the indicated mass fractions: 20%–30% strong alkali; 10%–20% phosphate; 1%–5% emulsifier; 0.2%–0.3% additives; and the balance being water. After welding, tantalum parts cleaned using this method exhibit smooth, stable welds without porosity; the tensile strength and elongation at the weld location can reach over 80% of the base material.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of tantalum cleaning, and particularly relates to a surface cleaning method before welding of metal tantalum. BACKGROUND

[0002] Physical vapor deposition (PVD) is one of the most critical processes in the production process of semiconductor chips, and the purpose is to deposit metal or metal compounds in the form of a thin film on a silicon wafer or other substrate, and then form a complex wiring structure in the semiconductor chip through cooperation of processes such as photolithography and etching. Physical vapor deposition is completed by a sputtering machine, and a sputtering target is a very important key consumable used in the above process. Common sputtering targets include high-purity Ta, and non-ferrous metals such as Ti, Al, Co and Cu.

[0003] The tantalum target for semiconductor is a diffusion welded target of tantalum metal and other metal materials (mainly copper, aluminum and titanium). In order to ensure the welding quality of tantalum metal, the welding position must be cleaned before welding. In the industrial production process, mineral oil often pollutes the surface of the metal, and these impurities will affect the cladding effect of the metal in the molten pool, and the impurities will also pollute the weld, reducing the mechanical properties of the material.

[0004] Mineral oil remains on the surface of the tantalum welding part, and in the welding process, gas volatiles are generated, forming porosity defects at the weld position. At the same time, under the condition of high temperature welding, the impurity elements of mineral oil are enriched at the grain boundary of tantalum metal, which seriously deteriorates the plasticity of the material, and the tensile strength and elongation at the weld position are less than 50% of the base material. SUMMARY

[0005] The purpose of the present application is to provide a surface cleaning method before welding of metal tantalum to solve at least one aspect of the problems and defects in the background art.

[0006] Specifically, the present application provides a surface cleaning method before welding of metal tantalum, comprising the following steps:

[0007] Mixing and cleaning the metal tantalum with a cleaning agent;

[0008] The cleaning agent is composed of the following mass fraction of raw materials:

[0009] Strong base 20% to 30%;

[0010] Phosphate 10% to 20%;

[0011] Emulsifier 1% to 5%;

[0012] Additive 0.2% to 0.3%;

[0013] and the balance is water.

[0014] According to one technical solution of the surface cleaning method of the present invention, it at least includes the following:

[0015] Beneficial effects:

[0016] The cleaning method of the present invention mainly utilizes chemical methods to remove oil; this chemical method refers to adding emulsifiers and additives to an alkaline solution to remove mineral oil from the surface of tantalum metal through emulsification.

[0017] An emulsifier is a surfactant. When the mineral oil on the tantalum metal surface reacts with the emulsifier, it turns into many tiny oil droplets and disperses in the solution, forming an emulsion of two immiscible liquids. Under the influence of hydrodynamic factors, the oil film is broken down and splits into tiny oil droplets, thus achieving the purpose of degreasing.

[0018] When the content of strong alkali is too low, the degreasing effect is poor; when the content of strong alkali is too high, it is not conducive to the dissolution of emulsifier.

[0019] Phosphates can increase the alkalinity of detergents, which helps to further improve the efficiency of oil removal.

[0020] After being cleaned by the method of this invention, the tantalum metal weld is smooth, stable and free of pores; there are no impurities from mineral oil, and the tensile strength and elongation at the weld position can reach more than 80% of the base material.

[0021] According to some embodiments of the present invention, the cleaning temperature is 70°C to 80°C.

[0022] To remove oil using emulsification, measures such as heating to increase temperature and increasing stirring can be taken during the operation to make the emulsification process faster and better.

[0023] According to some embodiments of the present invention, the cleaning time is 20 min to 25 min.

[0024] According to some embodiments of the present invention, the strong base is at least one of sodium hydroxide and potassium hydroxide.

[0025] According to some embodiments of the present invention, the phosphate is at least one of sodium phosphate or potassium phosphate.

[0026] According to some embodiments of the present invention, the emulsifier is at least one of sodium stearate and stearic acid.

[0027] According to some embodiments of the present invention, the additive is a mixture of acrylic emulsion and sodium silicate;

[0028] The acrylic emulsion is composed of the following raw materials in parts by weight:

[0029] 10 parts acrylic acid, 1 to 2 parts butyl acrylate, 0.2 to 0.3 parts 3-(trimethoxysilyl)propyl acrylate, 0.3 to 0.4 parts 2-fluoroacrylic acid, 5 to 7 parts ethyl acetate and 0.1 to 0.5 parts benzoyl peroxide.

[0030] This invention uses acrylic acid and butyl acrylate as the main monomers, and modifies them with 3-(trimethoxysilyl)propyl acrylate and 2-fluoroacrylic acid; thereby introducing fluorosilicone elements into the acrylic acid polymerization segment, further improving the affinity of acrylic emulsion for mineral oil, thus improving the removal effect of mineral oil; and further improving the cleaning effect.

[0031] According to some embodiments of the present invention, the mass ratio of the acrylic emulsion to sodium silicate is 10:1 to 2.

[0032] According to some embodiments of the present invention, the method for preparing the acrylic emulsion includes the following steps:

[0033] S1. Acrylic acid, butyl acrylate, 3-(trimethoxysilyl)propyl acrylate, 2-fluoroacrylic acid and ethyl acetate are mixed to obtain the first mixture;

[0034] S2. Then mix the first mixture with benzoyl peroxide and react.

[0035] According to some embodiments of the present invention, the mixing temperature in step S1 is 100°C to 110°C.

[0036] According to some embodiments of the present invention, the mixing time in step S1 is 1h to 2h.

[0037] According to some embodiments of the present invention, the temperature of the reaction in step S2 is 110°C to 120°C.

[0038] According to some embodiments of the present invention, the reaction time in step S2 is 2h to 3h.

[0039] According to some embodiments of the present invention, after the reaction in step S2, the pH value is adjusted to neutral to obtain a neutral emulsion.

[0040] According to some embodiments of the present invention, the cleaning is ultrasonic cleaning; the power of the ultrasonic wave is 200W to 300W.

[0041] The cleaning process utilizes ultrasonic vibrations, which improves cleaning efficiency and cleanliness.

[0042] Tantalum metal cleaned by the cleaning method of this invention should be welded within 5 hours to avoid re-contamination of the material and affect the welding effect. Detailed Implementation

[0043] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0044] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0045] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0046] Example 1

[0047] This embodiment describes a surface cleaning method for tantalum metal before welding, which consists of the following steps:

[0048] The tantalum metal was mixed with the cleaning agent and then cleaned (ultrasonic power of 200W, cleaning temperature of 75℃, cleaning time of 20min);

[0049] The cleaning agent is composed of the following raw materials by mass fraction:

[0050] Strong alkali (sodium hydroxide) 28%;

[0051] 12% phosphate (sodium phosphate);

[0052] Emulsifier (sodium stearate) 3%;

[0053] Additive (acrylic emulsion and sodium silicate in a mass ratio of 10:1) 0.2%;

[0054] The remainder is water.

[0055] In this embodiment, the acrylic emulsion comprises the following raw materials in parts by weight:

[0056] 10 parts acrylic acid, 1.7 parts butyl acrylate, 0.3 parts 3-(trimethoxysilyl)propyl acrylate, 0.3 parts 2-fluoroacrylic acid, 7 parts ethyl acetate and 0.3 parts benzoyl peroxide.

[0057] The method for preparing the acrylic emulsion in this embodiment consists of the following steps:

[0058] S1. Acrylic acid, butyl acrylate, 3-(trimethoxysilyl)propyl acrylate, 2-fluoroacrylic acid and ethyl acetate are mixed and kept at 110°C for 1.5 h to obtain the first mixture.

[0059] S2. Mix half of the amount of benzoyl peroxide in the formula with the first mixture and keep it at 115°C for 1.5 hours to obtain the second mixture.

[0060] S3. Mix half of the amount of benzoyl peroxide and the second mixture and keep it at 125°C for 1.5 hours. Then cool it to room temperature (25°C) and add ammonia (28% by mass) to adjust the pH to neutral.

[0061] Example 2

[0062] This embodiment describes a surface cleaning method for tantalum metal before welding, which consists of the following steps:

[0063] The tantalum metal was mixed with the cleaning agent and then cleaned (ultrasonic power of 200W, cleaning temperature of 75℃, cleaning time of 20min);

[0064] The cleaning agent is composed of the following raw materials by mass fraction:

[0065] Strong alkali (sodium hydroxide) 22%;

[0066] 18% phosphate (sodium phosphate);

[0067] Emulsifier (sodium stearate) 4%;

[0068] Additive (acrylic emulsion and sodium silicate in a mass ratio of 10:1) 0.3%;

[0069] The remainder is water.

[0070] In this embodiment, the acrylic emulsion comprises the following raw materials in parts by weight:

[0071] 10 parts acrylic acid, 2 parts butyl acrylate, 0.2 parts 3-(trimethoxysilyl)propyl acrylate, 0.4 parts 2-fluoroacrylic acid, 7 parts ethyl acetate and 0.3 parts benzoyl peroxide.

[0072] The preparation method of the acrylic emulsion in this embodiment is the same as that in Example 1.

[0073] Example 3

[0074] This embodiment describes a surface cleaning method for tantalum metal before welding, which consists of the following steps:

[0075] The tantalum metal was mixed with the cleaning agent and then cleaned (ultrasonic power of 200W, cleaning temperature of 75℃, cleaning time of 20min);

[0076] The cleaning agent is composed of the following raw materials by mass fraction:

[0077] Strong alkali (sodium hydroxide) 20%;

[0078] 20% phosphate (sodium phosphate);

[0079] Emulsifier (sodium stearate) 1%;

[0080] Additive (acrylic emulsion and sodium silicate in a mass ratio of 10:2) 0.3%;

[0081] The remainder is water.

[0082] In this embodiment, the acrylic emulsion comprises the following raw materials in parts by weight:

[0083] 10 parts acrylic acid, 1 part butyl acrylate, 0.2 parts 3-(trimethoxysilyl)propyl acrylate, 0.4 parts 2-fluoroacrylic acid, 7 parts ethyl acetate and 0.3 parts benzoyl peroxide.

[0084] The preparation method of the acrylic emulsion in this embodiment is the same as that in Example 1.

[0085] Example 4

[0086] This embodiment describes a surface cleaning method for tantalum metal before welding, which consists of the following steps:

[0087] The tantalum metal was mixed with the cleaning agent and then cleaned (ultrasonic power of 200W, cleaning temperature of 75℃, cleaning time of 20min);

[0088] The cleaning agent is composed of the following raw materials by mass fraction:

[0089] Strong alkali (sodium hydroxide) 23%;

[0090] 20% phosphate (sodium phosphate);

[0091] Emulsifier (sodium stearate) 5%;

[0092] Additive (acrylic emulsion and sodium silicate in a mass ratio of 10:1) 0.25%;

[0093] The remainder is water.

[0094] In this embodiment, the acrylic emulsion comprises the following raw materials in parts by weight:

[0095] 10 parts acrylic acid, 1.5 parts butyl acrylate, 0.25 parts 3-(trimethoxysilyl)propyl acrylate, 0.37 parts 2-fluoroacrylic acid, 7 parts ethyl acetate and 0.3 parts benzoyl peroxide.

[0096] The preparation method of the acrylic emulsion in this embodiment is the same as that in Example 1.

[0097] Example 5

[0098] This embodiment describes a surface cleaning method for tantalum metal before welding, which consists of the following steps:

[0099] The tantalum metal was mixed with the cleaning agent and then cleaned (ultrasonic power of 200W, cleaning temperature of 75℃, cleaning time of 20min);

[0100] The cleaning agent is composed of the following raw materials by mass fraction:

[0101] Strong alkali (sodium hydroxide) 23%;

[0102] 20% phosphate (sodium phosphate);

[0103] Emulsifier (sodium stearate) 5%;

[0104] Additive (acrylic emulsion) 0.25%;

[0105] The remainder is water.

[0106] In this embodiment, the acrylic emulsion comprises the following raw materials in parts by weight:

[0107] 10 parts acrylic acid, 1.5 parts butyl acrylate, 0.25 parts 3-(trimethoxysilyl)propyl acrylate, 0.37 parts 2-fluoroacrylic acid, 7 parts ethyl acetate and 0.3 parts benzoyl peroxide.

[0108] The preparation method of the acrylic emulsion in this embodiment is the same as that in Example 1.

[0109] Example 6

[0110] This embodiment describes a surface cleaning method for tantalum metal before welding, which consists of the following steps:

[0111] The tantalum metal was mixed with the cleaning agent and then cleaned (ultrasonic power of 200W, cleaning temperature of 75℃, cleaning time of 20min);

[0112] The cleaning agent is composed of the following raw materials by mass fraction:

[0113] Strong alkali (sodium hydroxide) 23%;

[0114] 20% phosphate (sodium phosphate);

[0115] Emulsifier (sodium stearate) 5%;

[0116] Additive (sodium silicate) 0.25%;

[0117] The remainder is water.

[0118] Example 7

[0119] This embodiment describes a surface cleaning method for tantalum metal before welding, which consists of the following steps:

[0120] The tantalum metal was mixed with the cleaning agent and then cleaned (ultrasonic power of 200W, cleaning temperature of 75℃, cleaning time of 20min);

[0121] The cleaning agent is composed of the following raw materials by mass fraction:

[0122] Strong alkali (sodium hydroxide) 23%;

[0123] 20% phosphate (sodium phosphate);

[0124] Emulsifier (sodium stearate) 5%;

[0125] Additive (acrylic emulsion and sodium silicate in a mass ratio of 10:1) 0.25%;

[0126] The remainder is water.

[0127] In this embodiment, the acrylic emulsion comprises the following raw materials in parts by weight:

[0128] 10 parts acrylic acid, 1.5 parts butyl acrylate, 0.25 parts 3-(trimethoxysilyl)propyl acrylate, 7 parts ethyl acetate and 0.3 parts benzoyl peroxide.

[0129] The method for preparing the acrylic emulsion in this embodiment consists of the following steps:

[0130] S1. Acrylic acid, butyl acrylate, 3-(trimethoxysilyl)propyl acrylate and ethyl acetate are mixed and kept at 110°C for 1.5 h to obtain the first mixture.

[0131] S2. Mix half of the amount of benzoyl peroxide in the formula with the first mixture and keep it at 115°C for 1.5 hours to obtain the second mixture.

[0132] S3. Mix half of the amount of benzoyl peroxide and the second mixture and keep it at 125°C for 1.5 hours. Then cool it to room temperature (25°C) and add ammonia (28% by mass) to adjust the pH to neutral.

[0133] Example 8

[0134] This embodiment describes a surface cleaning method for tantalum metal before welding, which consists of the following steps:

[0135] The tantalum metal was mixed with the cleaning agent and then cleaned (ultrasonic power of 200W, cleaning temperature of 75℃, cleaning time of 20min);

[0136] The cleaning agent is composed of the following raw materials by mass fraction:

[0137] Strong alkali (sodium hydroxide) 23%;

[0138] 20% phosphate (sodium phosphate);

[0139] Emulsifier (sodium stearate) 5%;

[0140] Additive (acrylic emulsion and sodium silicate in a mass ratio of 10:1) 0.25%;

[0141] The remainder is water.

[0142] In this embodiment, the acrylic emulsion comprises the following raw materials in parts by weight:

[0143] 10 parts acrylic acid, 1.5 parts butyl acrylate, 0.37 parts 2-fluoroacrylic acid, 7 parts ethyl acetate and 0.3 parts benzoyl peroxide.

[0144] The method for preparing the acrylic emulsion in this embodiment consists of the following steps:

[0145] S1. Acrylic acid, butyl acrylate, 2-fluoroacrylic acid and ethyl acetate are mixed and kept at 110°C for 1.5 h to obtain the first mixture.

[0146] S2. Mix half of the amount of benzoyl peroxide in the formula with the first mixture and keep it at 115°C for 1.5 hours to obtain the second mixture.

[0147] S3. Mix half of the amount of benzoyl peroxide and the second mixture and keep it at 125°C for 1.5 hours. Then cool it to room temperature (25°C) and add ammonia (28% by mass) to adjust the pH to neutral.

[0148] Example 9

[0149] This embodiment describes a surface cleaning method for tantalum metal before welding, which consists of the following steps:

[0150] The tantalum metal was mixed with the cleaning agent and then cleaned (ultrasonic power of 200W, cleaning temperature of 75℃, cleaning time of 20min);

[0151] The cleaning agent is composed of the following raw materials by mass fraction:

[0152] Strong alkali (sodium hydroxide) 23%;

[0153] 20% phosphate (sodium phosphate);

[0154] Emulsifier (sodium stearate) 5%;

[0155] Additive (acrylic emulsion and sodium silicate in a mass ratio of 10:1) 0.25%;

[0156] The remainder is water.

[0157] In this embodiment, the acrylic emulsion comprises the following raw materials in parts by weight:

[0158] 10 parts acrylic acid, 1.5 parts butyl acrylate, 7 parts ethyl acetate and 0.3 parts benzoyl peroxide.

[0159] The method for preparing the acrylic emulsion in this embodiment consists of the following steps:

[0160] S1. Acrylic acid, butyl acrylate and ethyl acetate are mixed and kept at 110°C for 1.5 h to obtain the first mixture.

[0161] S2. Mix half of the amount of benzoyl peroxide in the formula with the first mixture and keep it at 115°C for 1.5 hours to obtain the second mixture.

[0162] S3. Mix half of the amount of benzoyl peroxide and the second mixture and keep it at 125°C for 1.5 hours. Then cool it to room temperature (25°C) and add ammonia (28% by mass) to adjust the pH to neutral.

[0163] Comparative Example 1

[0164] This comparative example illustrates a surface cleaning method for tantalum metal before welding, comprising the following steps:

[0165] The tantalum metal was mixed with the cleaning agent and then cleaned (ultrasonic power of 200W, cleaning temperature of 75℃, cleaning time of 20min);

[0166] The cleaning agent is composed of the following raw materials by mass fraction:

[0167] Strong alkali (sodium hydroxide) 23%;

[0168] 20% phosphate (sodium phosphate);

[0169] Emulsifier (sodium stearate) 5%;

[0170] The remainder is water.

[0171] The cleaned tantalum metal of Examples 1-9 and Comparative Example 1 of the present invention was subjected to welding tests; and the tensile strength and elongation of the weld were tested.

[0172] The argon-protected tungsten inert gas welding process is shown in Table 1.

[0173] Table 1 Argon-Shielded Tungsten Inert Arc Welding Process

[0174] Material Thickness / mm Current / A Voltage / V Welding speed / (cm / s) High purity tantalum sheet 2 250 12 1.2

[0175] Tensile tests were conducted on a materials mechanical property testing machine. The loading axis of the tensile testing machine was aligned with the axis of the specimen, and the load was applied slowly. The specimen deformed under a steady increase in load until it fractured. Based on the original cross-sectional area of ​​the specimen, the actual magnitude of the load, and the magnitude of the deformation at fracture, the tensile strength and elongation after fracture can be calculated. The test results are shown in Table 2.

[0176] Table 2 Performance test results of Examples 1-9 and Comparative Example 1 of the present invention

[0177]

[0178] In summary, the cleaning method of this invention mainly utilizes chemical methods for degreasing. This chemical method involves adding emulsifiers and additives to an alkaline solution, utilizing emulsification to remove mineral oil from the tantalum metal surface. The emulsifier is a surfactant; when the mineral oil on the tantalum metal surface reacts with the emulsifier, it transforms into numerous tiny oil droplets that disperse in the solution, forming an emulsion of two immiscible liquids. Under the influence of hydrodynamic factors, the oil film is disrupted, breaking down into tiny oil droplets, thus achieving the purpose of degreasing. If the content of strong alkali is too low, the degreasing effect is poor; if the content of strong alkali is too high, it is detrimental to the dissolution of the emulsifier. After cleaning using the method of this invention, the weld of the tantalum metal is smooth, stable, and free of porosity; there are no impurities introduced by the mineral oil, and the tensile strength and elongation at the weld location can reach more than 80% of the base material. The acrylic emulsion of the present invention is based on acrylic acid and butyl acrylate as the main monomers, and is modified with 3-(trimethoxysilyl)propyl acrylate and 2-fluoroacrylic acid; thereby introducing fluorosilicone elements into the acrylic acid polymerization segment, further improving the affinity of the acrylic emulsion for mineral oil, thereby improving the removal effect of mineral oil; and further improving the cleaning effect.

[0179] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for surface cleaning of metal tantalum before welding, characterized by, The method comprises the following steps: cleaning the metal tantalum after mixing with a cleaning agent; the cleaning agent is prepared from the following raw materials with the following mass fractions: 20-30% of strong alkali; 10-20% of phosphate; 1-5% of emulsifier; 0.2-0.3% of additive, and the rest is water; the additive is a mixture of fluorosilicon modified acrylic emulsion and sodium silicate, and the mass ratio of the fluorosilicon modified acrylic emulsion to sodium silicate is 10:1-2; the acrylic emulsion is prepared from the following raw materials with the following weight fractions: 10 parts of acrylic acid, 1-2 parts of butyl acrylate, 0.2-0.3 parts of 3-(trimethoxysilyl) propyl acrylate, 0.3-0.4 parts of 2-fluoroacrylic acid, 5-7 parts of ethyl acetate, and 0.1-0.5 parts of benzoyl peroxide; the preparation method of the acrylic emulsion comprises the following steps: S1, mixing acrylic acid, butyl acrylate, 3-(trimethoxysilyl) propyl acrylate, 2-fluoroacrylic acid and ethyl acetate to prepare a first mixture; S2, mixing the first mixture and benzoyl peroxide for reaction.

2. The surface cleaning method of metal tantalum before welding according to claim 1, characterized by, the cleaning temperature is 70-80℃.

3. The surface cleaning method of the metal tantalum before welding according to claim 1, characterized by, the cleaning time is 20-25 min.

4. The surface cleaning method of tantalum metal prior to welding according to claim 1, characterized by, the strong alkali is at least one of sodium hydroxide and potassium hydroxide.

5. The surface cleaning method of tantalum metal prior to welding according to claim 1, characterized by, the phosphate is at least one of sodium phosphate and potassium phosphate.

6. The surface cleaning method of tantalum metal prior to welding according to claim 1, characterized by, the emulsifier is sodium stearate.

7. The surface cleaning method of tantalum metal prior to welding according to claim 1, characterized by, the cleaning is ultrasonic cleaning, and the ultrasonic power is 200-300 W.

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