Fabrication of Microminiaturized Core Memories by Plastic Encapsulation Techniques

Plastic encapsulation of nonlinear ferrites, and the effect of this encapsulation on the magnetic characteristics of the ferrites, is discussed in this paper. This technique provides greater immunity to shock and vibration damage than conventional core frames and provides bit densities in excess of one million per cubic foot. Chemical deposition and photographic techniques may be used to form a portion of the wiring matrix. Through-hole plating of ferrites having a 15-mil diameter hole is possible. Small-evaluation memories have been fabricated, using both toroids and transfluxors. Temperature tests on these memories show that encapsulation causes a slight increase in switching speed and a small decrease on output for a given drive current. These changes remain almost constant over the temperature range. No significant changes have been noted in the noise output. Techniques outlined are presently being used in the fabrication of microminiaturized, nondestructive memories for missile and satellite application.