Wow, 18 responses to my question. What a helpful group this is !! Thank you all !
Special thanks to Paul for some free promotion of my employer ;->
Daan Terstegge
Unclassified mail
>>> Paul Klasek <[log in to unmask]> 11/06 12:06 am >>>
Well , Daan ; read the lot, didn't agree with any, only Phil spoke the magic
word :
Measurement .
ESD is like lead in solder , a LOT of feelings, overkills to satisfy less
informed customers still ,
sort of wearing umbrella full time because it may rain .
Like Phil, really went in to it, got half the static and surface meters on
market and "discovered" a magic new world .
(Others you can detect with gaussmeters or latest mobile phone detectors -
bad for your downloads).
I have been always concerned with wrist strap clumsiness in most operations
,
so when designing new plant it went this way :
The DISSIPATIVE (hearing about conductive floors in electronics never fails
to terrify me) carpet and vinyl with copper strip grid under wired to your
existing earth grid (same potential);
all benches have SSteel(alu extrusions are same but smudgy, anodized are
insulated) front edge clipping dissipative rubber, linked via 1meg resistor
to the same earth grid .
Under that edge is stretched a piano wire for crocodile clips of the desired
wrist straps .
Than the consequent moment of truth came (measurement)
Of those three (heelstrap/shoe, dissipative bench with edge, wrist strap) :
no price giving for guessing right : the forefront action of those static
sink edges taking up any nylon, coats, = moving = generative items is by far
ahead . Seen charges "sitting" on coats, bags, bins, etc. even with heel or
wrist straps correctly in action : the edge performed flawlessly .
So the verdict in form of procedure with this in mind was to give the folks
enough choice according to the nature of the work : if working behind test
gear, the wrist strap may be appropriate ;
when standing and turning while assembling boards to units the
edge/bench/shoe is sufficient as well (measured) .
Most interesting part have been actually the prevention of build ups :
the phenomenal charges sitting on bins from stores, mouldings, plastic
bags(really bad), people, "imported" to controlled areas are an eye opener,
I learned to watch for a totally different things at audits than the
traditional "obvious" items ,
and would never "think" without a meter in hand .
It came about when I grounded all of our silicon face masks production (non
electronic), finding 5KV+ sitting inside of each cup when popped out of
moulding (the bin was "glowing" on meter); fellows thought I went ESD nuts ,
before we proved one department was one giant capacitor .
From what you say Daan ; you're fine as it is even without deadly conductive
floor ,
don't believe any trends or customers ;
get yourself calibrated field and surface meters, ESD standards, and some
basic SPC charts,
I'd bet my last dollar you'll find things in places you have no idea they're
there ;
with little alarms on static controlled benches (barring Nicola's coils).
Sorry to stretch it ; sometimes the mindless hysterics in our industry
really wind me up .
On the other hand Eric may be right, all this is not worth it with some
banana customers .
The absolute classic is when after all of this care the store fellow just
floods it with polystyrene beans(10KV+)or polybag in contact with all sorts
of terminals . Rest my case
cu
Paul Klasek
ResMed
PS
Inge, Daan is actually very much classified , Signaal is one of the ancients
of Zeeland, nice place to learn,
check : http://www.signaal.nl ; sort of Channel opposite of Marconi's .
Quite interesting french Thomson-CSF apart from euro takeovers (like
signaal), took over even local ADI (Australian Defence Industry (a Co.),
resulting in lifted pentagon eyebrows , with ADI's subsequent loss of some
privy ties .
Should the galia win even the rugby union cup ; i'd start to analyze
seriously quiet quickening in the region .
-----Original Message-----
From: d. terstegge [mailto:[log in to unmask]]
Sent: Friday, 5 November 1999 20:28
To: [log in to unmask]
Subject: [TN] Wrist wraps for seated operators
Hello Technet,
We've recently received some complaints from a customer who is not happy
with the fact that our operators don't wear wrist wraps during seated
operations like handsoldering and inspection. Our factory relies on
grounding through the (conductive) chairs, ESD-shoes, conductive floor and
ESD-workbenches, but the chairs are tested only once per year, which is
obviously less frequent then one would test wrist wraps.
Is the customers concern justified, and should we introduce wrist wraps ?
Daan Terstegge
Unclassified
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