Hi technetters

I thought I would ensure that is was clear how the tray cart is designed
to work.  I hope there is no one out there using Bliss tray carts without
either an ESD Static Dissipative floor or Conductive floor or properly
applied and maintained ESD Static dissipative or Conductive Wax.  I
am unaware of any research that shows without proper grounding to
the floor our cart is ESD safe.

How the tray cart does work. The PC Board sits on an ESD static
dissipative mat, which is in a Conductive composite reinforced tray,
which sits on zinc plated steel rails that are welded to a steel cart
frame that has a ground chain attached to the bottom which drags on
the floor about 2”-3”.  This works on the floors mentioned above very
well.  On a non grounded floor I do not recommend it with one
exception.  If you use our ground cable connector option on the cart
and plug it into a techbench or something else that is grounded to
drain any charges, then load the cart, then unplug the cart and move it
to the next location and plug it in there, (During this move the
employee is touching it so you already have a common ground
between the two), when you plug it in at the next location all the
charges on the operator and the cart will drain safely, provided you do
not touch the PC boards until after you plug it in. (do not leave a tray
cart sitting some where that is not plugged in) I would be comfortable
that this will work fine.  It certainly would require employee training to
reduce the chance of someone forgetting to plug it in.  For that reason
only I do not recommend it.  If you have really good people then it
would probably work fine.  Our products are designed to be virtually
worry free, ESD safe and easy to use.  This method stretches the
“easy to use” part.

I would wax the floor properly and eliminate the problem entirely.

The tray cart has become the industry standard for a reason, it works
better than any other method in the electronics industry to date for
handling and processing PC boards offline and in manual assembly
and protecting those boards from ESD and physical damage.

I would be interested to hear all additional constructive comments
good or bad.

Ken Bliss
President and CEO
Engineering Manager
Bliss Industries, Inc.

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