Nano Tungsten Probe Needle Production Methods

Tungsten wire  is used for nano tungsten probe needle production and there are many production methods, such as: mechanical shearing method, mechanical grinding method, field evaporation method, ion bombardment method, electric spark machining method, electrochemical etching method and so on. The most commonly used production method is electrochemical etching method. This method is simple in production principle and production equipment, easy to realize, good in controllability and low in cost, so it is widely used. Electrochemical etching method can be divided into: AC-DC sharing method, magnetic field enhancement method, liquid film method, reverse electrochemical method, the lower end etching method and pulse electrochemical machining method. The above methods control the shape and aspect ratio of the tungsten probe needle by changing the concentration of the solution, the depth of immersion, the corrosion voltage and the duty cycle of the pulse voltage. However, during the etching process, the tungsten filament is stationary, so the shape of needle is exponential type and the adjustable range of aspect ratio is small.

New nano probe needle production method is to use single clip microcomputer stepper motor shaft lifting up tungsten wire with uniform velocity and to control the parameters of the electrochemical corrosion, so it can produce different aspect ratio nano tungsten probe needle and the tip radius of curvature can up to 30nm, which can meet different application requirement. Nana tungsten probe needle production processes are as follows:

1. Firstly, use electro corrosion for removing tungsten wire surface oxide layer, and then to clean it. That is tungsten wire as the anode, copper rod as the cathode, placed in NaOH aqueous solution (2mol / L), 2.5mm-9mm immersion depth of the anode and 40mm of cathode, passed IOV AC, for 30-100S corrosion, so it can remove the tungsten wire surface oxide layer, and then can use deionized water for cleaning.

2. Secondly, cleaned tungsten wire as anode and copper rod as cathode, placed in corrosion solution (2mol / L sodium hydroxide solution), turns on the power to start corrosion, while uses single clip microcomputer stepper motor shaft to lift up tungsten wire with uniform velocity and the part of the tungsten wire is kept in the solution at all times. After finished lift up we should stop the wire in the solution till the tip of the tungsten wire to fall off to obtain the nano tungsten probe needle.

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