ESD
Concerns
Aluminum tubes are coated with a mil-spec hardened coating called
NEDOX, which is highly conductive and has some teflon content to
facilitate part sliding. The tubes mount is such a fashion as to
provide good contact between the tube and the main plates of the
handler, which are in turn connected directly to ground. Thus, the
metal tubes offer a good electrical path to ground to prevent the
build-up of potentially hazardous static electricity.
A corollary of the above feature is that use of metal tubes
prevents wearing of standard ESD coated plastic tubes. These
tubes are typically coated with a thin layer of soap or a fatty
material to provide conductivity. After several uses of these
tubes, the ESD coating wears off and the ESD property is lost.
Use of Exatron metal tubes saves the use of empty plastic tubes
from use as output bins and cuts down wear on these tubes.
Reduction
of Jams
It has been our experience that plastic tubes often have very
serious tolerance problems. Tube dimensions will vary dramatically
from
vendor to vendor and sometimes from batch to batch, due to wear
on the extrusion die and material choice of tube material. With
small geometry devices (such as .150" body SOICs), these differences
between tubes can wreak havoc with the output shuttle, leading
to unwanted jams. Use of metal tubes, which are machined to precise
tolerances, greatly minimizes this problem.
Ease
of Changeover
In almost all cases, all Exatron metal tubes use the same tube
holder to mount to the handler. In almost all cases, tube holders
for plastic tubes are custom made for each device. Thus, if your
handler will have change-over kits, it is far easier to change
with metal tubes than with plastic. Plastic tubes require changing
the tube holder while metal tubes can use the same tube holder.
