TechNeters:
        With encouragement from Ken I am posting my comment I made to him
and taking the liberty of posting his since his
answers my comments:


Dehoyos, Ramon" wrote:

>         Ken:
>         I respect your input on how to properly use board carts in
specific
> the ones you manufacture. My question is, has any one in your company done
> any voltage measurements on how much voltage a cart can build up by being
> rolled a block on a tile floor? I walked fast pushing one roll cart for
about 200 feet and it
> did not build one volt of charge measured with a VOM. It may not be the
best
> way to measure static charge.  A better tool may be an oscilloscope.
> Experience has shown me that rolling carts on tile floors has negligible
> effect on ICs.
> Do not mean to argue just communicate my perspective on the matter.
>         Regards,
>         Ramon
                Wearing conductive material jackets does help a lot. Since
they do not charge up as some of the artificial materials. Sleeves do
contact boards while working and may discharge on components.

  Hi Ramon

Thanks for taking the time to write.

First to answer your question, no we have not done the measurement the way
you
described, we had 3M auditors come in several years ago with the standard
testers and field monitors and tell me the carts work great.

Let me explain the tray cart based on your comment.  Moving the cart may or
may
not actually generate a static charge, depending on a lot of variables.
People
around it or other equipment that may have a charge and are creating a
"field"
around them or it may transfer some of that static field to the cart or the
PC
boards.  You cannot see it of course but it can be measured if you have the
right equipment as you mentioned.  The only safe way that I can see to
ensure
there is none ever is to follow my guidelines.  Keeping it grounded prior to
touching a PC board is key.  Just like when you are about to work at a
techbench you plug in a wrist strap plug to ground you prior to touching the
PC
board.  You may not feel anything and you may feel a static shock when you
first touch ground.  It is a huge variable creating static electricity, that
is
why complete prevention is the only way to stop it safely.

I encourage you to post to the IPCnet forum your comment.

Ken Bliss

"
>

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