All EMC long life, high performance
magnetic heads are made with the same materials, processes and construction techniques.
The general design features are similar for all EMC heads from the smallest cassette heads
to the largest motion picture sound heads. The attached drawing of the EMC magnetic head
structure points out some of these features using a four channel, 1/4" cartridge head
as an example.
The patented magnetic material used in both the track and shield
structures is a ceramic bonded stack of Hy Mu 800 magnetic material. The ceramic provides a long wearing surface for the tape to ride on and the Hy Mu
800 provides a high quality magnetic path for the magnetic flux to follow during either
the recording or playback function.
Stainless steel or ceramic spacers are used as separators between the track and shield
sections. The spacers are epoxy bonded to the magnetic material and this thin bond line is
the only epoxy present in the tape contact area. The case of the head may be made from
aluminum or brass while the shield can is Hy Mu 800 magnetic material. The
materials for the case and shield
can are completely outside the tape contact area and therefore do not affect the
head performance or interact with the tape in any way.
The EMC magnetic head structure was designed for extreme environments that have wide
variations in temperature and humidity and that have severe shock, vibration and
acceleration requirements. The passive magnetic material, ceramic and stainless steel used
in the tape contact surface is ideal for applications where the tape is left in static
contact with the face of the head for extended periods of time. Chemical reactions do not
readily occur between these passive materials and corrosive elements that may be released
from the compounds used to make up the magnetic tape whether in an inert atmosphere
environment or in an environment with extremely high humidity.
The EMC magnetic head structure was designed to minimize the amount of epoxy in contact
with the tape. As shown in the attached drawing there are only 16 epoxy bond lines in the
tape contact area. Conventional head designs have between 132 and 248 epoxy bond lines in
contact with the tape. These bond lines promote friction between the tape and the head
surface. In addition, foreign material can adhere to the soft epoxy structure and cause
spacing losses between the tape and the head.
This technical note describes the general features used in the design of the tape
contact surface on the face of EMC magnetic heads. Questions regarding this technical note
or other aspects of EMC magnetic head design should be directed to EMC
Engineering at 800
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