Manufacturing method of tantalum capacitor anode

Abstract

The invention discloses a manufacturing method of a tantalum capacitor anode. The manufacturing method comprises the following steps: preprocessing a tantalum block and a tantalum wire; the tantalum block and the tantalum wire are positioned through a welding tool, and the tantalum block to be welded and the tantalum wire to be welded are placed in the sealed and welded cavity; the tantalum block and the tantalum wire are welded and connected through electric resistance welding, and protective gas is continuously introduced during welding; and sintering the tantalum block and the tantalum wire after welding, and taking out the tantalum block and the tantalum wire after the tantalum block and the tantalum wire are cooled to obtain the tantalum capacitor anode. Metallurgical bonding of the tantalum wire and the tantalum block is achieved through resistance welding, solder pollution is avoided, the contact resistance of a connector is smaller than or equal to 5 m omega, the tensile strength is larger than or equal to 5 N, and leakage current stability and structural reliability of the tantalum capacitor are guaranteed. By accurately controlling the welding current, time and pre-pressure, local overmelting of the tantalum block or crushing of a porous structure is avoided, meanwhile, high-temperature oxidation of tantalum is effectively prevented through inert gas protection, and it is ensured that the capacitive performance of the tantalum block is not affected by the welding process.

Description

Technical Field

[0001] This invention belongs to the field of capacitor manufacturing technology, and particularly relates to a method for manufacturing a tantalum capacitor anode. Background Technology

[0002] The connection quality between the tantalum wire and the pre-sintered tantalum block in a tantalum capacitor directly determines the capacitor's electrical performance, mechanical strength, and service life. In existing technologies, the traditional tantalum capacitor anode (sintered tantalum anode) is the core positive electrode structure. The core objective of its manufacturing process is to construct a porous tantalum matrix with high specific surface area, high conductivity, and stable structure using powder metallurgy technology, laying the foundation for the subsequent formation of the oxide film dielectric layer (Ta2O5) and cathode extraction. However, existing technologies cannot meet the market demands for miniaturization, high frequency operation, and large capacity in tantalum capacitors, necessitating a novel anode manufacturing method.

[0003] Resistance welding is widely used in metal joining due to its advantages such as good energy controllability, no solder contamination, and metallurgical bonding of joints. However, when applied to welding tantalum wire and pre-sintered tantalum blocks, it faces many technical challenges: the pre-sintered tantalum block has a porous structure with uneven electrical and thermal conductivity, which can easily lead to disordered welding energy distribution; the diameter of the tantalum wire is usually only 0.15-0.5mm, which is significantly different from the size of the tantalum block, making it easy for the tantalum wire to burn out or for the tantalum block to not fully fuse during welding; tantalum has high chemical reactivity and easily reacts with oxygen and nitrogen at high temperatures to form brittle compounds, reducing joint performance.

[0004] Traditional tantalum capacitor anode manufacturing follows an integrated technical route of powder preparation, precision molding, and high-temperature sintering. The core logic is that tantalum wire and tantalum powder are pressed into shape using a powder molding machine, followed by vacuum high-temperature sintering to form the tantalum anode. The parameters of these three processes must be strictly matched to ultimately achieve an anode matrix with high specific surface area, low impurities, and a stable porous structure, providing the foundation for the high performance of tantalum capacitors.

[0005] However, traditional tantalum capacitor anode manufacturing has the following drawbacks: 1. Tantalum wire itself does not contribute to capacitance. Calculated based on the total tantalum mass of the anode, tantalum wire only serves as the lead electrode, yet it consumes about 5-10% of the tantalum material, further increasing costs.

[0006] 2. Tantalum wire is a solid metal, which occupies a lot of tantalum block volume, thus reducing the volume utilization efficiency of the tantalum block.

[0007] 3. Density gradient problem: During compression molding, the pressure is unevenly distributed along the axial direction (upper mold pressure > lower mold pressure), resulting in a density difference between the upper and lower parts of the blank (deviation 5-10%). After sintering, a "layered porous structure" is formed, which affects the consistency of electrical properties.

[0008] 4. The conductive path of the porous structure is long and tortuous. Combined with the contact resistance of the tantalum wire, the ESR increases significantly in the high-frequency range (>1MHz). Furthermore, the minimum inductance of the tantalum capacitor is 20-200nH, resulting in a large equivalent series inductance (ESL). This makes it unsuitable for high-frequency applications such as radio frequency and fast charging (which require ESR <10mΩ and ESL <1nH). Summary of the Invention

[0009] This invention provides a method for manufacturing a tantalum capacitor anode. By optimizing the process parameters and auxiliary measures of resistance welding, a high-strength, low-defect connection between the tantalum wire and the pre-sintered tantalum block is achieved, ensuring the electrical performance stability and structural reliability of the tantalum capacitor and further improving the performance of the tantalum anode block.

[0010] The present invention is achieved through the following technical solutions.

[0011] The present invention provides a method for manufacturing a tantalum capacitor anode, comprising the following steps: S1: Pre-treatment of tantalum blocks and tantalum wires; S2: Use welding fixtures to position the tantalum block and tantalum wire, and place the tantalum block and tantalum wire to be welded into the sealed welding cavity; S3: Tantalum blocks and tantalum wires are welded together by resistance welding, with a shielding gas continuously supplied during welding; S4: After welding, the tantalum block and tantalum wire are sintered. After the tantalum block and tantalum wire are cooled, they are removed to obtain the tantalum capacitor anode.

[0012] Preferably, the tantalum block is pretreated to achieve a porosity of 20-40% and a density of 5.5-8.0 g / cm³. 3 The tantalum wire undergoes pretreatment to remove the oxide layer at its welding end, and the welding end head is ground to form an inclined surface at an angle of 0-30°.

[0013] Preferably, in step S2, the welding fixture includes a tantalum block clamping mechanism for positioning the tantalum block and a tantalum wire guiding mechanism for positioning the tantalum wire. The contact area between the tantalum block clamping mechanism and the tantalum block is not less than 80% of the bottom surface area of ​​the tantalum block. The welding end of the tantalum wire is aligned with the center of the tantalum block, and the contact pressure between the welding end of the tantalum wire and the tantalum block is 1-5 kg.

[0014] Preferably, the resistance welding is performed using a pulse resistance welding machine; the pre-pressure time for resistance welding is set to 50-100ms, the welding current to 100-1000A, the welding time to 0.1-0.5s, and the holding pressure time to 100-200ms.

[0015] Preferably, in step S3, the welding current is adjusted according to the following rules: when the tantalum wire diameter is ≤0.2mm and the tantalum block density is ≤5.0g / cm³. 3At that time, the welding current is 300-500A; when the tantalum wire diameter is >0.2mm and the tantalum block density is >5.0g / cm³. 3 At that time, the welding current is 500-1000A.

[0016] Preferably, the current is adjusted in real time during the welding process to keep the resistance change rate ≤ ±15%.

[0017] Preferably, the welding electrode head has a spherical structure, the electrode is a tungsten-copper alloy, and the radius of the spherical surface of the welding electrode is 1.5-2 times the diameter of the tantalum wire.

[0018] The sintering process includes: [the process is carried out] under a vacuum degree of not less than 1.3 × 10⁻⁶. -3 Sinter at 1200-1500℃ in an environment of Pa and hold for 10-30 minutes.

[0019] Preferably, in step S3, the protective gas includes argon or nitrogen.

[0020] Preferably, in step S3, the flow rate of the protective gas is 5-10 L / min.

[0021] The beneficial effects of this invention are as follows: 1. Excellent welded joint quality: Resistance welding is used to achieve metallurgical bonding between tantalum wire and tantalum block, eliminating solder contamination. The joint contact resistance is ≤5mΩ and the tensile strength is ≥5N, ensuring stable leakage current and structural reliability of tantalum capacitors.

[0022] 2. Protect the properties of pre-sintered tantalum blocks: By precisely controlling the welding current, time and pre-pressure, local overmelting of the tantalum blocks or crushing of the porous structure is avoided. At the same time, the inert gas protection effectively prevents the high-temperature oxidation of tantalum, ensuring that the capacitance performance of the tantalum blocks is not affected by the welding process.

[0023] 3. High process stability: Through workpiece pretreatment, special tooling positioning and adaptive adjustment of welding parameters, the welding process is standardized and controlled, with a yield of ≥98%, making it suitable for large-scale production.

[0024] 4. Strong compatibility: Welding parameters can be adjusted according to different specifications of tantalum wire (0.15-0.5mm) and pre-sintered tantalum blocks (porosity 20%-40%) to meet the manufacturing needs of tantalum capacitors with different capacities and packaging forms. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the welding steps of the present invention; Figure 2 This is a welding schematic diagram of the present invention; In the diagram: 1-tantalum wire, 2-welding point, 3-tantalum block. Detailed Implementation

[0026] The technical solution of the present invention is further described below, but the scope of protection is not limited to what is described.

[0027] Example 1: like Figure 1-2 As shown, a method for manufacturing a tantalum capacitor anode includes the following steps: S1: Pre-treatment is performed on tantalum blocks and tantalum wires with a purity of ≥99.95%. The tantalum block pre-treatment is sintering at a temperature of 1320℃ and a holding time of 15min. The sintering atmosphere is vacuum. Under these parameters, the tantalum block retains a suitable porous structure and has sufficient structural strength to support the welding process. S2: Use welding fixtures to position the tantalum block and tantalum wire, and place the tantalum block and tantalum wire to be welded into the sealed welding cavity; S3: The tantalum block and tantalum wire are welded together by resistance welding. During welding, the shielding gas is continuously introduced. After welding, the shielding gas is continued to be introduced until the tantalum block and tantalum wire cool down to ≤50℃, and then they are removed. S4: After welding, the tantalum block and tantalum wire are sintered. After the tantalum block and tantalum wire cool down, they are taken out and the welding joint of the tantalum block and tantalum wire is inspected to see if it is qualified. After the inspection is qualified, the tantalum capacitor anode is obtained.

[0028] The tantalum block is pretreated to reduce its porosity to 20-40% and its density to 6.1 g / cm³. 3 The welding area of ​​the low-density tantalum block is mechanically extruded to increase the density and strength of the welding area, so that its density reaches the above-mentioned value; the tantalum wire is pre-treated and its welding end oxide layer is polished, with a polishing length of 2mm, and the welding end head is polished into an inclined surface at a 20° angle.

[0029] The tantalum block pretreatment step includes: [the process is described in the original text, but the translation is incomplete and requires further context.] -3 Tantalum blocks were sintered at 1300°C in an environment of Pa and held for 20 minutes.

[0030] In step S2, the welding fixture includes a tantalum block clamping mechanism for positioning the tantalum block and a tantalum wire guiding mechanism for positioning the tantalum wire. The shape of the welding fixture is determined according to the shape of the tantalum block and the tantalum wire. The tantalum block clamping mechanism is made of conductive copper alloy. The contact area between the tantalum block clamping mechanism and the tantalum block is not less than 80% of the bottom surface area of ​​the tantalum block to ensure uniform current conduction. The welding end of the tantalum wire is aligned with the center of the tantalum block. The contact pressure between the welding end of the tantalum wire and the tantalum block is 3 kg to ensure good contact and avoid crushing the porous structure of the tantalum block.

[0031] The resistance welding is performed using a pulse resistance welding machine; the pre-pressure time is set to 80ms, the welding current range is maintained at 100-1000A, the welding time is 0.3s, and the holding pressure time is 150ms.

[0032] The current is adjusted in real time during the welding process to keep the resistance change rate ≤ ±15%.

[0033] The welding electrode head has a spherical structure with a diameter of 0.8 mm. The electrode is made of tungsten-copper alloy. The radius of the spherical surface of the welding electrode is twice the diameter of the tantalum wire. This avoids excessively high local current density caused by an excessively small contact area between the electrode and the tantalum wire, while also preventing energy dispersion caused by an excessively large contact area.

[0034] In step S3, the protective gas includes argon or nitrogen, and the purity of the protective gas is ≥99.99%.

[0035] In step S3, the flow rate of the protective gas is 8 L / min.

[0036] Figure 1 In the process, the welding process is as shown in the single-pulse power-on mode in the figure, consisting of starting switch (start) → pressurization time 42ms (electrode pressurization) → welding time 18ms (power-on) → holding time 3ms → ending time 3ms (electrode opening).

[0037] The sintering process includes: [the process is carried out] under a vacuum degree of not less than 1.3 × 10⁻⁶. -3 Sintering is performed at 1300℃ in a Pa environment and held for 20 minutes. This step is used to reduce impurities such as oxygen and nitrogen in the tantalum core, thereby improving its mechanical strength and reliability.

[0038] Example 2: like Figure 1-2 As shown, a method for manufacturing a tantalum capacitor anode includes the following steps: S1: Pre-treatment is performed on tantalum blocks and tantalum wires with a purity of ≥99.95%. The tantalum block pre-treatment is sintering at a temperature of 1200℃ and a holding time of 10min. The sintering atmosphere is vacuum. Under these parameters, the tantalum block retains a suitable porous structure and has sufficient structural strength to support the welding process. S2: Use welding fixtures to position the tantalum block and tantalum wire, and place the tantalum block and tantalum wire to be welded into the sealed welding cavity; S3: The tantalum block and tantalum wire are welded together by resistance welding. During welding, the shielding gas is continuously introduced. After welding, the shielding gas is continued to be introduced until the tantalum block and tantalum wire cool down to ≤50℃, and then they are removed. S4: After welding, the tantalum block and tantalum wire are sintered. After the tantalum block and tantalum wire cool down, they are taken out and the welding joint of the tantalum block and tantalum wire is inspected to see if it is qualified. After the inspection is qualified, the tantalum capacitor anode is obtained.

[0039] The tantalum block is pretreated to reduce its porosity to 20% and its density to 5.5 g / cm³. 3The welding area of ​​the low-density tantalum block is mechanically extruded to increase the density and strength of the welding area, so that its density reaches the above-mentioned value; the tantalum wire is pre-treated and its welding end oxide layer is polished, with a polishing length of 1mm.

[0040] The tantalum block pretreatment step includes: [the process is described in the original text, but the translation is incomplete and requires further context.] -3 Tantalum blocks were sintered at 1200°C in an environment of Pa and held for 10 minutes.

[0041] In step S2, the welding fixture includes a tantalum block clamping mechanism for positioning the tantalum block and a tantalum wire guiding mechanism for positioning the tantalum wire. The shape of the welding fixture is determined according to the shape of the tantalum block and the tantalum wire. The tantalum block clamping mechanism is made of conductive copper alloy. The contact area between the tantalum block clamping mechanism and the tantalum block is not less than 80% of the bottom surface area of ​​the tantalum block to ensure uniform current conduction. The welding end of the tantalum wire is aligned with the center of the tantalum block. The contact pressure between the welding end of the tantalum wire and the tantalum block is 1 kg to ensure good contact and avoid crushing the porous structure of the tantalum block.

[0042] The resistance welding is performed using a pulse resistance welding machine; the pre-pressure time is set to 50ms, the welding current is maintained in the range of 300-500A, the welding time is 0.1s, and the holding pressure time is 100ms.

[0043] The current is adjusted in real time during the welding process to keep the resistance change rate ≤ ±15%.

[0044] The welding electrode head has a spherical structure with a diameter of 0.3 mm. The electrode is made of tungsten copper alloy. The radius of the spherical surface of the welding electrode is 1.5 times the diameter of the tantalum wire. This avoids excessively high local current density caused by an excessively small contact area between the electrode and the tantalum wire, while also preventing energy dispersion caused by an excessively large contact area.

[0045] In step S3, the protective gas includes argon or nitrogen, and the purity of the protective gas is ≥99.99%.

[0046] In step S3, the flow rate of the protective gas is 5 L / min.

[0047] Figure 1 In the process, the welding process is as shown in the single-pulse energization mode in the figure, consisting of starting switch (starting) → pressurization time 20ms (electrode pressurization) → welding time 5ms (energization) → holding time 1ms → ending time 1ms (electrode opening).

[0048] The sintering process includes: [the process is carried out] under a vacuum degree of not less than 1.3 × 10⁻⁶. -3 Sintering is performed at 1200℃ in an environment with Pa, followed by a holding time of 10 minutes. This step is used to reduce impurities such as oxygen and nitrogen in the tantalum core, thereby improving its mechanical strength and reliability.

[0049] Example 3: like Figure 1-2 As shown, a method for manufacturing a tantalum capacitor anode includes the following steps: S1: Pre-treatment is performed on tantalum blocks and tantalum wires with a purity of ≥99.95%. The tantalum block pre-treatment is sintering at a temperature of 1400℃ and a holding time of 20min. The sintering atmosphere is vacuum. Under these parameters, the tantalum block retains a suitable porous structure and has sufficient structural strength to support the welding process. S2: Use welding fixtures to position the tantalum block and tantalum wire, and place the tantalum block and tantalum wire to be welded into the sealed welding cavity; S3: The tantalum block and tantalum wire are welded together by resistance welding. During welding, the shielding gas is continuously introduced. After welding, the shielding gas is continued to be introduced until the tantalum block and tantalum wire cool down to below 50°C before being removed. S4: After welding, the tantalum block and tantalum wire are sintered. After the tantalum block and tantalum wire cool down, they are taken out and the welding joint of the tantalum block and tantalum wire is inspected to see if it is qualified. After the inspection is qualified, the tantalum capacitor anode is obtained.

[0050] The tantalum block is pretreated to reduce its porosity to 20-40% and its density to 6.0 g / cm³. 3 The welding area of ​​the low-density tantalum block is mechanically extruded to increase the density and strength of the welding area, so that its density reaches the above-mentioned value; the tantalum wire is pre-treated and its welding end oxide layer is polished, with a polishing length of 3mm, and the welding end head is polished to form an inclined surface at a 30° angle.

[0051] The tantalum block pretreatment step includes: [the process is described in the original text, but the translation is incomplete and requires further context.] -3 Tantalum blocks were sintered at 1500°C in an environment of Pa and held for 30 minutes.

[0052] In step S2, the welding fixture includes a tantalum block clamping mechanism for positioning the tantalum block and a tantalum wire guiding mechanism for positioning the tantalum wire. The shape of the welding fixture is determined according to the shape of the tantalum block and the tantalum wire. The tantalum block clamping mechanism is made of conductive copper alloy. The contact area between the tantalum block clamping mechanism and the tantalum block is not less than 80% of the bottom surface area of ​​the tantalum block to ensure uniform current conduction. The welding end of the tantalum wire is aligned with the center of the tantalum block. The contact pressure between the welding end of the tantalum wire and the tantalum block is 5 kg to ensure good contact and avoid crushing the porous structure of the tantalum block.

[0053] The resistance welding is performed using a pulse resistance welding machine; the pre-pressure time is set to 100ms, the welding current is maintained in the range of 500-1000A, the welding time is 0.5s, and the holding pressure time is 200ms.

[0054] The current is adjusted in real time during the welding process to keep the resistance change rate ≤ ±15%.

[0055] The welding electrode head has a spherical structure with a diameter of 1.0 mm. The electrode is made of tungsten copper alloy. The spherical radius of the welding electrode is twice the diameter of the tantalum wire. This avoids excessively high local current density caused by an excessively small contact area between the electrode and the tantalum wire, while also preventing energy dispersion caused by an excessively large contact area.

[0056] In step S3, the protective gas includes argon or nitrogen, and the purity of the protective gas is ≥99.99%.

[0057] In step S3, the flow rate of the protective gas is 10 L / min.

[0058] Figure 1 In the process, the welding procedure is as shown in the single-pulse energization mode in the figure, consisting of starting the switch → applying electrode pressure for 50ms before welding → energizing and welding for 30ms → maintaining electrode pressure for 5ms after welding → ending for 5ms.

[0059] The sintering process includes: [the process is carried out] under a vacuum degree of not less than 1.3 × 10⁻⁶. -3 Sintering is performed at 1500℃ in an environment of Pa, followed by a holding time of 30 minutes. This step is used to reduce impurities such as oxygen and nitrogen in the tantalum core, thereby improving its mechanical strength and reliability.

[0060] Using the methods of Examples 1-3, 20 sets of tantalum wires and tantalum blocks were welded separately. The tantalum wires and tantalum blocks were prepared according to the specifications of tantalum capacitor D-shell, 2.5V 470μF. After welding, the tensile strength of the joint was tested with a tensile testing machine. The breaking force was ≥5N and the fracture location was not located at the welded joint. The contact resistance of the joint was tested with a micro resistance tester. The contact resistance value was ≤5mΩ. The minimum inductance of the tantalum capacitor was reduced by one order of magnitude to 10-30nH compared with the 20-200nH anode obtained by the prior art. The anode quality was qualified.

Claims

1. A method for manufacturing a tantalum capacitor anode, characterized in that, Includes the following steps: S1: Pre-treatment of tantalum blocks and tantalum wires; S2: Use welding fixtures to position the tantalum block and tantalum wire, and place the tantalum block and tantalum wire to be welded into the sealed welding cavity; S3: Tantalum blocks and tantalum wires are welded together by resistance welding, with a shielding gas continuously supplied during welding; S4: After welding, the tantalum block and tantalum wire are sintered. After the tantalum block and tantalum wire are cooled, they are removed to obtain the tantalum capacitor anode.

2. The method for manufacturing a tantalum capacitor anode as described in claim 1, characterized in that: The tantalum block is pretreated to reduce its porosity to 20-40% and its density to 5.5-8.0 g / cm³. 3 The tantalum wire undergoes pretreatment to remove the oxide layer at its welding end, and the welding end head is ground to form an inclined surface at an angle of 0-30°.

3. The method for manufacturing a tantalum capacitor anode as described in claim 1, characterized in that: In step S2, the welding fixture includes a tantalum block clamping mechanism for positioning the tantalum block and a tantalum wire guiding mechanism for positioning the tantalum wire. The contact area between the tantalum block clamping mechanism and the tantalum block is not less than 80% of the bottom surface area of ​​the tantalum block. The welding end of the tantalum wire is aligned with the center of the tantalum block, and the contact pressure between the welding end of the tantalum wire and the tantalum block is 1-5 kg.

4. The method for manufacturing a tantalum capacitor anode as described in claim 1, characterized in that: The resistance welding is performed using a pulse resistance welding machine; the pre-pressure time is set to 50-100ms, the welding current to 100-1000A, the welding time to 0.1-0.5s, and the holding pressure time to 100-200ms.

5. The method for manufacturing a tantalum capacitor anode as described in claim 4, characterized in that: In step S3, the welding current is adjusted according to the following rules: when the tantalum wire diameter is ≤0.2mm and the tantalum block density is ≤5.0g / cm³. 3 At that time, the welding current is 300-500A; when the tantalum wire diameter is >0.2mm and the tantalum block density is >5.0g / cm³. 3 At that time, the welding current is 500-1000A.

6. The method for manufacturing a tantalum capacitor anode as described in claim 4, characterized in that: The current is adjusted in real time during the welding process to keep the resistance change rate ≤ ±15%.

7. The method for manufacturing a tantalum capacitor anode as described in claim 4, characterized in that: The welding electrode head has a spherical structure, the electrode is made of tungsten-copper alloy, and the radius of the spherical surface of the welding electrode is 1.5-2 times the diameter of the tantalum wire.

8. The method for manufacturing a tantalum capacitor anode as described in claim 1, characterized in that: The sintering process includes: [the process is carried out] under a vacuum degree of not less than 1.3 × 10⁻⁶. -3 Sinter at 1200-1500℃ in an environment of Pa and hold for 10-30 minutes.

9. A method for manufacturing a tantalum capacitor anode as described in claim 1, characterized in that: In step S3, the protective gas includes argon or nitrogen.

10. A method for manufacturing a tantalum capacitor anode as described in claim 1, characterized in that: In step S3, the flow rate of the protective gas is 5-10 L / min.

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