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Debris Filter for E-Beam Machining Apparatus

IP.com Disclosure Number: IPCOM000086451D
Original Publication Date: 1976-Sep-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 3 page(s) / 41K

Publishing Venue

IBM

Related People

Sturans, MA: AUTHOR

Abstract

In the process of machining material with electron beams, both solid and gaseous substances are generated which effect the focus and positioning stability of the beam. The effect of these gases is to momentarily defocus the beam due to space-charge variations. This can be compensated for by a dynamic focus correction, usually referred to as kinetic focusing to distinguish it from deflection dynamic focusing, and, therefore, is an undesirable but not a critical effect. When the material to be machined is a dielectric such as green ceramic material in the multilayer ceramic technology, then the effect of generated debris is critical since it will accumulate on surfaces surrounding the beam, obtain a charge from the ions and electrons, and cause the beam to deform and deflect.

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Debris Filter for E-Beam Machining Apparatus

In the process of machining material with electron beams, both solid and gaseous substances are generated which effect the focus and positioning stability of the beam. The effect of these gases is to momentarily defocus the beam due to space-charge variations. This can be compensated for by a dynamic focus correction, usually referred to as kinetic focusing to distinguish it from deflection dynamic focusing, and, therefore, is an undesirable but not a critical effect. When the material to be machined is a dielectric such as green ceramic material in the multilayer ceramic technology, then the effect of generated debris is critical since it will accumulate on surfaces surrounding the beam, obtain a charge from the ions and electrons, and cause the beam to deform and deflect.

This filter device, when placed in the final magnetic lens of an E-beam apparatus, will allow electrons to pass through it almost undisturbed but will stop all debris and most gas modules generated by the thermal machining. The basic principle stems from the fact that in a magnetic lens, electrons are not only focused but also undergo a rotation about the beam axis. An approximate equation for the angle of rotation is: Theta = 0.187 NI over the square root of V rad. wherein; N = the number of turns I the lens current V = the accelerated voltage.

A simple embodiment of the debris filter is illustrated in Fig. 1 which consists of a metal cylinder 10 with its axis aligned with the axis of an electron beam. The filter is located in the center of the beam focusing coil 12. Two shutter elements 14 and 16 are supported in cylinder 10. The shape of the elements 14 and 16 is designed to be spaced a distance wherein an electron in the beam following the path 18 undergoes a 60 degree rotation, as defined by the above formula. The segments of the shutter 14 and 16 are arranged so that the bottom shutter 16 is advanced 60 degrees relative to the segment shown in shutter 14. Thus, viewing the filter fr...