Reed Blade Pressing
Reed pressing is done by selecting a special alloy of Nickel-Iron called 52-alloy which is chosen for the purpose of having the closest thermal expansion match to glass. The size of the alloy wire diameter is selected depending the final switching capacity of the finished Reed Switch.
The wire is passed through multiple spin straightener stations and into press tools designed to accommodate different wire sizes. Reed blades are then pressed at high speeds and then ejected from the tools using compressed air. Carbide press tools are used to press the Nickel-Iron wire into reed blades, to minimise tool wear out.
The pressed blades then undergo inspection under special microscopes for burrs at the contact area and lead-out area where cropping occurs. Depending on the design of the carbide tools, cropping is done before or after pressing. This is governed by the design of the blade, whether it is symmetrical or off-centered. Usually, for glass tubes of inner diameter less than 1.7mm, off centered blades are selected.
Subsequently, the pressed reed blades are inspected for straightness and surface smoothness before being approved for de-greasing. Drawing tolerances in straightness and surface finish are check by quality personnel and then approved as a batch. Inspection is done periodically to ensure long term conformance to drawings and specifications. Additional blade stiffness calculations are also done prior to reed blade design to ensure the forces of grams/micron are targeted for the right closure forces.
Flatness and uniformity are crucial in the pressing process to ensure the efficiency of the reed switches. The selection of appropriate materials and precise pressing techniques play a vital role in the overall quality of the hermetically sealed reed switches. Quality control measures are implemented at each stage of the pressing process to guarantee the reliability and functionality of the final product.