The unthreaded turned down section allows for the part to be secured to the circuit board via a swaging process. The swaging of the part curls the part back onto the board. This curled section keeps the part firmly in place. Parts are thoroughly tested to ensure that proper swaging will not cause excessive cracking or flaking. The round shape provide a nice finished look. Aluminum is widely used in Aerospace applications due to its high strength to weight properties. RoHS certifications available.
