In a drive enclosure where head/disk
separation has to be kept under 2 nanometer,
control of external contamination is
of extreme importance. In the figures
below are reproduced photos of some
of the drive components that help keep
humidity, chemical and particulate contamination
under control.
Figure
1shows a picture of a
typical drive desiccant.
Generic humidity buffer
such as silica-gel can
be employed that help
reduce large relative
humidity excursions when
the outside environment
(T/RH) abruptly changes.
In this example, the desiccant
brick is wrapped in a
porous PTFE enclosure,
and a pressure-sensitive
adhesive allows it to
be attached to the top
cover of the drive.
Figure 2 shows a recirculation
filter, usually located
in a area of high flow
of the drive enclosure.
This allows very fast
cleanup of particulates
that could still be left
within the enclosure after
manufacturing, or that
could be generated during
drive operation. A vapor-drain
consisting of activated
carbon can also be added
to this component for
removal of organic contaminants.
Figure
3 shows a breather filter
unit. This component is
usually placed in an area
of lower pressure of the
drive, and allows controlled
in-and-out flow of outside
air during pressure changes.
A small filter is embedded
in it. To minimize diffusive
flow, a high length/area
ratio diffusion channel
can also be built within
the component.
