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Subject:
From:
Steven Creswick <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Steven Creswick <[log in to unmask]>
Date:
Tue, 1 Jun 2010 06:00:51 -0400
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Bob,

I leave the best answer to the ESD experts, however, I would defer from
placing ESD sensitive devices in a non-static dissipating container out of
concern for charge generation by the parts mechanically moving around in the
container - triboelectric charging.

Another comment on the general subject of grounding oneself.  My hands are
extremely calloused, farmer-like hands.  That thick layer of dead skin is a
VERY good insulator.  Simply 'touching' a grounded potential does not
'ground' me!  I have to slather lotion on my hands [girly-soft hands] and
literally squeeze the 'ground point' to become grounded myself.  Just
wearing a wrist-strap does not always guarantee ESD safety!  

I prefer the old adage - an ounce of prevention is worth a pound of cure -
Ben Franklin?  


Steve Creswick
http://www.linkedin.com/in/stevencreswick



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Thursday, May 27, 2010 11:10 AM
To: [log in to unmask]
Subject: Re: [TN] ESD spec question

Joe,

 Thanks for the feedback but I just don't buy either idea.

1.  I can not see how storing the plastic box in an shielded contain is
going to affect the parts inside the plastic box. 

2.  I do not see how the potential (with respect to Ground) of an operator
is going to influence what happens when an operator touches a part inside
the plastic box. 

In either case above I fail to see any current flow as an operator touches a
part in the plastic box.

Thanks,
Bob Kondner

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kane, Joseph E (US SSA)
Sent: Thursday, May 27, 2010 11:01 AM
To: [log in to unmask]
Subject: Re: [TN] ESD spec question

Again, it might be simplistic, but I think the spec gives you 
only two options - store the parts in ESD protective packaging, or 
if they're out of protective packaging, they have to be kept in 
an ESD Protected Area (EPA).

Some might object that those boxes are constructed of static generating 
plastic, but I think parts in the boxes will be okay as long as the box 
is either:

1. enclosed in an external static shielding container, or 
2. kept at an EPA where anyone who comes near it is grounded through a
strap or through conductive footwear and floor.

-Joe 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Thursday, May 27, 2010 10:26 AM
To: [log in to unmask]
Subject: Re: [TN] ESD spec question

Hi,

 Resend from yesterday.

 Does anyone have any good reasons why storing static sensitive parts in
small plastic containers is "Not Good". See the MOSFETs in these pictures.

 We use these small plastic boxes for engineering stock, very convenient. 

  www.kondner.com/files/partinbox.jpg

  www.kondner.com/files/partbox.jpg

Thanks,
Bob Kondner





Kenny,

 As long as you just look and don't touch you will not get in trouble! :-)

 There was a ESD Expert, I forgot who, who would say "No Spark means No
Problems". Spark was being used to infer current flow, obviously if no
current flows through a junction there is no problem, by definition.

 Now we get to the touching of parts. If a part is sitting on an insulator
can any current flow? The answer is yes due to capacitance to free space.
Small parts have very small level of capacitance to free space. I have never
seen numbers but I suspect any current flows would be well below damage
levels. 

 If you touch a part in a metal drawer wow oh wow is that a different story.


 I keep loose parts in plastic containers, that makes some folks cringe but
none has ever explained how a damaging current could be generated to/from a
part in an insulating container. 

 I would really like to get other folks informed ideas. Too many folks
simply repeat some mantra without having any data. (Like buy the biggest
house you can afford, don't worry about the payments. )

Bob Kondner

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ken Bloomquist
Sent: Wednesday, May 26, 2010 12:20 PM
To: [log in to unmask]
Subject: Re: [TN] ESD spec question

My first thought on this is that if I were looking in the drawers I'd touch
the metal of the cabinet before opening the drawer. Also if the drawers have
a metal handle and are grounded inside the cabinet the by virtue of all that
you would be grounded, no need for anything more.

KennyB
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Graham Collins
Sent: Wednesday, May 26, 2010 9:30 AM
To: [log in to unmask]
Subject: [TN] ESD spec question

Hey TechNet
It's been a quiet day on Technet!  

I've got a question regarding ESD.  I was taught that if I am not grounded I
do not go near anything that is ESD .  The example we are debating here
today concerns parts that are stored in metal cabinets.
The cabinet is grounded, and within the cabinet drawers there are ESD
sensitive parts in individual bins, not covered or packaged (no faraday
cage).  

Is it OK to open the drawer and look into the cabinet without being properly
grounded?  I say no, but am I being overly cautious?

If "no" is the right answer, where would I find that in an ESD spec?
I've given ESD-S20.20 a quick peruse, nothing jumped out at me.

regards, 
  
Graham Collins
Halifax Production Engineering
(902) 873-2000 ext. 6215 

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