Tantalum wire is an important rare metal material with excellent physical and chemical properties, finding wide application in many high-end industrial fields. In capacitor manufacturing, tantalum wire is a key material for manufacturing tantalum capacitors (especially leaded capacitors). Due to the high dielectric constant of tantalum oxide film, capacitors are small in size, have large capacitance, and good stability, making them widely used in precision circuits in mobile phones, computers, automotive electronics, and military applications. In the semiconductor field, it is used as sputtering targets, high-temperature furnace components, or as a support material in chip manufacturing.
In vacuum furnace heating elements, tantalum has a high melting point (approximately 3017°C) and can be used as a heating element, heat shield, or support frame in high-temperature furnaces in vacuum or inert environments. It is commonly used in high-temperature sintering (such as ceramics and hard alloys). In optical coating equipment, tantalum wire is used to support evaporation materials or as a heating source in electron beam evaporation coating. In chemical and corrosion-resistant equipment, tantalum has excellent acid and alkali resistance (except for hydrofluoric acid and hot concentrated alkalis). Tantalum wire can be used to weave filter screens and sealing materials for chemical equipment, or as a reactor liner and a key component of heat exchangers. Due to its good biocompatibility, tantalum wire is used in medical devices, particularly in orthopedic implants (such as bone screws and plates) or surgical sutures.
Raw material preparation: High-purity tantalum powder is typically obtained from the smelting and purification of tantalite or niobium-tantalite ores, or the remelting and refining of recycled materials. Producing high-quality tantalum wire (especially capacitor grade) requires high-purity (typically ≥99.95%) tantalum powder with specific particle size and shape. The physicochemical properties of the powder directly affect the performance and consistency of the final product. Powder pressing and forming: Tantalum powder is loaded into a mold and pressed into a high-density "compact" or "electrode rod" under high pressure (typically 200-400 MPa) in an isostatic press (cold isostatic pressing CIP or hot isostatic pressing HIP). This step gives the powder preliminary shape and strength for subsequent processing. Impurities and gases are removed from the compact, and the powder particles are bonded together through atomic diffusion to form a dense metallic crystal structure.
Vertical melting sintering/electron beam sintering: The most mainstream method. Using a consumable electrode as a "consumable electrode," a large current is passed through it in a high vacuum environment. The high temperature (typically 70% above the melting point of tantalum, approximately 2200°C) is generated by the ingot's own resistance, causing it to melt from one end and solidify from top to bottom, forming a dense "tantalum ingot" or "tantalum rod." This process effectively purifies the metal. Vacuum furnace sintering is used for the production of certain special grades or intermediate products.
This is the core process of gradually thinning and lengthening large tantalum ingots, achieved through a combination of forging, rolling, and drawing. Forging/brushing involves heating the sintered tantalum ingot (typically at 1000-1400°C) and forging it on an air hammer or hydraulic press. This breaks up the coarse as-cast structure, initially refines the grains, and rolls it into a larger diameter rod. Under a protective atmosphere (such as argon) or vacuum environment, the heated tantalum rod is rolled multiple times through a rolling mill, gradually reducing its cross-sectional area to produce wire rods or smaller diameter rods. Multiple annealing processes are required to restore plasticity.
The rolled wire rod is sandblasted and pickled to remove oxide scale, then drawn in multiple passes through a drawing die to gradually reduce the diameter to a medium size (e.g., below Φ3mm). This stage is usually performed under heating. More precise control is required when the wire diameter is finer. A multi-pass continuous drawing machine, combined with intermediate annealing and lubrication, is used to draw the wire to the target diameter (capacitor wire can be as fine as below Φ0.1mm).
Heat treatment (annealing) eliminates work hardening, restores material plasticity, and controls grain size and final properties. It is performed in an annealing furnace protected by a high vacuum or high-purity inert gas. Temperature, time, and atmosphere are strictly controlled to prevent oxidation and contamination. Annealing is performed throughout the entire plastic forming process.
Surface treatment uses a mixture of hydrofluoric acid and nitric acid to remove the oxide layer and surface defects generated during drawing or annealing. Electropolishing is used for wires with extremely high requirements (e.g., ultrafine wires) to obtain an extremely smooth and clean surface, which is crucial for the energizing performance of the capacitor anode. Residual acid and impurities are thoroughly cleaned, and the wire is dried.
