The core purpose of alkaline washing of tungsten wire

Remove surface oxides (WO ∝, W ₂ O ₅)

Remove residual drawing lubricants (graphite, silicone oil, etc.)

Improve surface activity and enhance adhesion of subsequent coatings (such as gold and nickel)

Improve surface uniformity and reduce the risk of subsequent wire breakage

Alkali washing process steps

Process conditions

Temperature: 80~95 ℃ (the higher the temperature, the stronger the cleaning ability, but the time needs to be controlled to prevent excessive corrosion)

Time: 1-5 minutes (adjusted according to the diameter of the tungsten wire and the degree of contamination, typically ≤ 2 minutes for Φ 0.1mm filaments)

Stirring: Ultrasonic assisted (40kHz) or mechanical oscillation to improve cleaning uniformity

Post processing

Washing with water:

First rinse with deionized water (DI water), then rinse thoroughly with ultrasonic water (5 minutes) to remove the alkaline solution.

Acid neutralization (optional):

Soak in dilute nitric acid (HNO ∝, 5%) for 10-30 seconds to remove residual alkali and activate the surface.

Drying:

Vacuum drying (100-150 ℃) or nitrogen blowing to avoid oxidation.

Application scenarios of alkali washed tungsten wire

Lighting industry: incandescent lamps and halogen lamps use tungsten wire, which improves luminescence uniformity after alkali washing.

Electronic packaging: Pre treatment of bonding wires (such as tungsten carbide) to ensure the bonding strength of the coating.

Semiconductor probe: Ultra fine tungsten wire with a diameter of 0.05~0.2mm, reduced contact resistance after alkaline washing.

3D printing: Surface cleaning of wire EDM to improve printing accuracy.