Tantalum wire made of tantalum powder by rolling, drawing and other plastic processing methods
Tantalum wire is a tantalum material made of tantalum powder by rolling, drawing and other plastic processing methods. Tantalum wire is used the most in the electronics industry and is mainly used for the anode lead of tantalum electrolytic capacitors.
Tantalum wire is a tantalum wire made of tantalum powder by rolling, drawing and other plastic processing methods.
Manufacturing method
Powder metallurgy method
The process flow is: raw material (tantalum powder) → mixing → forming → vertical melting → rotary forging → intermediate annealing → drawing → finished product annealing → quality inspection → packaging and storage.
Smelting method
The process flow is: raw material (tantalum powder) → mixing → forming → pre-sintering → electron beam melting → fine forging → intermediate annealing → rotary forging → intermediate annealing → drawing → finished product annealing → quality inspection → packaging and storage.
It can be classified according to its chemical purity, performance, use and state.
According to chemical purity, it is divided into 3 categories: (1) metallurgical tantalum wire, purity 99.0% Ta; (2) high-purity tantalum wire, purity 99.0% ~ 99.9% Ta; (3) ultra-high purity tantalum wire, purity 99.9% ~ 99.99% Ta.
According to performance, it is divided into 4 categories: (1) chemical corrosion-resistant tantalum wire; (2) high-temperature resistant and high-strength tantalum wire; (3) anti-oxidation brittle tantalum wire; (4) capacitor tantalum wire.
According to use, capacitor tantalum wire is divided into 3 categories: (1) tantalum wire for solid tantalum electrolytic capacitors (SDTa1, SDTa2); (2) tantalum wire for liquid tantalum electrolytic capacitor leads (LDTa1, LDTa2); (3) tantalum wire for capacitors with reliability indicators (DTals, DTalL).
Tantalum wire for capacitors is divided into three categories according to the state: (1) soft state (M), tensile strength σb = 300 ~ 600MPa; (2) semi-hard state (Y2), tensile strength σb = 600 ~ 1000MPa; (3) hard state (Y), tensile strength σb > 1000MPa.
Technical requirements
Includes three aspects: (1) Tantalum wire for solid tantalum capacitors, its chemical composition shall comply with the provisions of Table 1; mechanical properties, process properties, electrical properties and surface quality shall comply with the provisions of Table 2. (2) Tantalum wire for liquid tantalum capacitors, except for higher requirements on surface quality, other technical indicators are generally consistent with those of solid tantalum capacitor tantalum wire. The surface of liquid tantalum wire should be bright, free of oil stains, and no continuous pits and scratches when observed under 10 times magnification. (3) Tantalum wire for capacitors with reliability indicators. Surface quality, whether it is liquid tantalum wire or solid tantalum wire, must be observed under a microscope. Solid tantalum wire should be magnified 10 times, and liquid tantalum wire should be magnified from 10 times to 30 times. No scratches or continuous pits should be observed. The requirements for process performance have also been greatly improved. The number of bending times for anti-oxidation brittleness is increased from no less than 2 times to no less than 3 times for small diameter (d-0.25-0.40-mm) tantalum wire, and from no less than 3 times to no less than 4 times for thicker (d==0.50-00.60mm) tantalum wire.
Anti-oxidation brittleness theory
The literature “A Theoretical study on the Optimum Average Grain Size of Tantalum Wire for Capacitops” [see the English journal Chinese journal of Metal Science and Technology, 1987, 3(6)] proposed a theory on the “optimum grain size of capacitor tantalum wire”. The key points are: (1) To improve the resistance of tantalum wire to oxygen brittleness, the grain structure of tantalum wire must be refined; (2) The fine-grained structure must have high temperature resistance (above 1700°C and maintained for more than 30 minutes) and metallographic thermal stability; (3) The theoretical calculated value of the optimal grain size of the fine-grained structure is ≤40μm; (4) One of the process approaches to achieve fine-grained structure is to obtain it by initiating high-melting-point dispersed nuclei during the recrystallization of tantalum wire.