I use "Stat-Les" anti-static floor finish on my benches.  You can find it at
Legge Systems,
http://www.leggesystems.com/c-177-static-control-floor-care-products.aspx
The price is pretty good for the 1 quart size bottles ($20 or so) and that
does a lot of benches.

-Bob, N3XKB

On Mon, Jan 25, 2010 at 8:42 AM, Brucekareen@aol.com wrote:

Bruce wrote:

I notice that many folks who have contributed on this thread use
anti-static benchtops, but I have never found it necessary (and I try
to keep the RH in my house under 45% -- it is generally 20% or less
in the winter).  I've been fooling with static-sensitive parts for 35
years and haven't lost one to static yet.  With that perspective, my
preferred benchtop is white Formica with a very, very slightly
pebbled surface.  Very durable, including to molten solder, and small
parts show up well.  I use rubberized "gunsmith" mats for preventing
scratches to delicate workpieces (these happen to be anti-static, but
that is not why I have them).

Other bench thoughts:

Bench depth is very important.  I sometimes work on equipment that is
more than 24" deep, so I want at least 30" of clear space in front of
any obstructions (power strips, Variac, test equipment,
whatever).  In the past, I used a "flying bridge" over the rear 18"
of a 48"-deep bench to elevate the test equipment, which worked very
well.  Now I use 24" deep adjustable wire-rack shelving units behind
a 30" benchtop (As others have pointed out, you can do the same with
equipment racks -- I'm not a fan of rack-mounting test equipment
unless the racks are anchored and everything is on slides, which I
was not prepared to do).  I don't have enough shop real estate to
have a permanent access aisle behind the test equipment, so the bench
and racks have large (5") locking polyurethane wheels and can be
pulled out relatively easily for reconfiguration.  This provides
plenty of stability for electronic projects, but you wouldn't want to
mount a big vise on the bench and try to bend 1" rebar.  For that, I
have a separate metalworking shop.

Bench height is also important.  I prefer a tall bench, suited to
working standing or sitting on an ergonomic stool, so my bench top is
44" above the floor -- a bit below my standing elbow height.

Finally, one can never have too many power outlets, or too much
light, in a workshop.  Lighting should be arranged so that it doesn't
cause specular reflections from the workpiece or the faces of test equipment.

Best regards,

Charles

In message 20100125182712.7014911B858@karen.lavabit.com, "Charles P. Steinmet
z" writes:

My worktable has a surface of hardwood-floor-boards and a painted
steel profile on the front that I make point out of touching before
sticking my fingers into any sensitive circuits.  Works for me.

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG        | TCP/IP since RFC 956
FreeBSD committer      | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

Hi Charles,

I'm in a similar boat where I've worked with static sensitive parts without
any problems without having so much as put on a wrist strap.  It's just
never been an issue, even with our RH sitting around 12% here in New
Mexico.  I've been shoulder deep in Cray and SGI supercomputers without
worrying about it.  Then the day came where I needed to do surgery on my
network analyzer.  I figured the $20 for the coating was cheap insurance.  I
don't have $37k sitting around to replace it should I fry it.  That was the
first time I ever put on a wrist strap too!

-Bob

On Mon, Jan 25, 2010 at 11:27 AM, Charles P. Steinmetz <
charles_steinmetz@lavabit.com> wrote:

One generally looks for static-dissipative surfaces, rather than conductive surfaces. 1 Megohm/square, for instance.  The idea is to keep everything isopotential as charge drops onto things, not to rigorously establish a common voltage.

You haven't lost one that you know of. It also depends on the kinds of parts you're working with. There are some that are quite sensitive AND which don't fail outright, but just degrade performance a bit when they take a hit. It also depends on the energy behind the hit, of course.  An example might be the MiniCircuits ERA-4 or ERA-5 (just because I happen to have the data sheet handy).  Take a look at the later pages in the report, and you can see where the gain changes slightly as a result of 100V ESD hits (see page 6, where you can see gain dropping about 1.5 dB over 8 pulses, with about 0.1dB per hit.)

As they say at the end of the report:
The new amplifier ERA-4XSM shows gradual degradation in the gain and the
device voltage. That fact is not so bad. Even with the multiple stress a customer
would rather have gradual changes then catastrophic failure. The amplifier
withstands a single 100V ESD pulse, or 3 pulses at 50V.

http://www.minicircuits.com/pages/pdfs/an60028.pdf

When we (JPL) do site visits to vendors, lackadaisical approaches to ESD handling are one of the common problems. For us, who are building just one or two of something that's going to be going somewhere where repair isn't an option, latent damage and gradual degradation are a big deal.

It's really a "habit" thing that everyone has to get used to. That's why even nuts and bolts come in ESD packaging (even though they're obviously ESD immune): it gets people in the mindset of "come in the area, put on the wrist strap".  Back in the 70s, when ESD processes started to be used, they would have multiple categories of parts, some which needed ESD precautions (CMOS parts, DRAMs,etc.) and some which didn't (resistors, capacitors).  It was found that workers would be working with something in one category, and the habits would carry over to the others, so the industry, in general, went to the "everything is ESD sensitive" approach.

The worst offenders for ESD are the engineers (like those of us reading the list!), because they actually know what parts are sensitive and which aren't, and tend to take shortcuts with the non-sensitive parts.  Which works, sort of, until they guess wrong, and cook something.  "Hey, why is the NF on this LNA 0.2 dB higher than it was yesterday?"

jim

I've still got a paper copy of an HP Bench Brief from 1983 that was one
of my first introductions to the dangers of ESD.  I've used a wrist
strap and antistatic mat since then.  ESD protection in the ICs has
improved since then, but I think that the article is still mostly
applicable today.

http://www.hparchive.com/Bench_Briefs/HP-Bench-Briefs-1983-03-05.pdf

Ed

Lux, Jim (337C) wrote:

So looking at ESD mat material at Digikey, there appears to be a
bewildering array of choices.  Elastomer, rubber, vinyl,
thermoplastic, laminate, foam rubber, and polyethelene.

Any guidelines about what to choose?

Scott

On Jan 25, 2010, at 11:59 AM, Ed Palmer ed_palmer@sasktel.net wrote:

If you're in and out of ESD areas, then shoes with conductive soles are easier to use than always wrist strapping. Ditto if you're working on something big where the cord for the wrist strap gets in the way.  In some of our clean rooms, we have booties to go over your street shoes that have conductive coatings on them, and a conductive ribbon that you tuck into your sock to make contact.  (And you go stand on a test pad to make sure, of course).

I like the conductive shoes approach, it's pretty screw up proof, because you don't have to remember to plug your wrist strap in when you come to the bench, but the floor needs to be conductive, too.

These days, the black bins are dissipative and not marking.  The black foam is history (we all have ICs with corroded leads in the garage where the black foam turns to goo). Here at JPl, we don't use the pink bags/peanuts/stuff at all, because apparently, the coating can flake or rub off.  We use plastic that has a very thin metalized layer, and I think that's pretty much industry standard now.

And the megohm is important to keep you from inadvertently dying when you happen to accidentally contact the AC line.