On Wed, 17 Feb 2010 08:04:41 -0600, Jim Yanik
wrote:
I still can't buy that her body generated static charges.
I don't really understand the mechanism. My best guess(tm) is that
her skin resistance is less than mine. She would present a high
surface resistance (ohms/square) while I would present a somewhat
lower resistance. I would tend to bleed off generated static, while
she would tend to hold it. I've crudely tested this guess(tm) with an
ohmmeter. Grabbing the probes between index thumb and index finger on
both hands, I usually get about 4M Ohms. This lady would do about
twice that. (Note: She died in 2007 so I can't retest).
maybe her skin is really dry.
Yep.
Hmm... you're confirming my observations, suspicions and speculations.
Probably that their feet didn't sweat as much as mine....
Or that they wore different socks.
I don't know which articles of clothing cause the most ESD problems.
My guess(tm) is that the seat of the pants, rubbing against the chair,
would have the biggest effect. Google shows a few ESD safe socks, but
far more emphasis seems to be placed on ESD safe shoes. I would think
they would go together as an insulator in a problem with both socks
and shoes. Plenty of heel grounders, but few ankle straps.
Maybe a tin hat or colander with a long grounding strap? In the lab,
we used all metal stools with hard fiberboard seats. No ESD problem.
We did have a consultant running around looking for ESD and other
"safety" issues, but he never noticed the cotton Persian rug in my
office.
did you do electronic servicing in your office?
No. I slept on the office floor and the Persian rug (with foam pad
underneath) made it far more comfortable. I sometimes dragged
finished boards and products into the office for a show and tell, or
interview, but there was no soldering or electronics work done in the
office (mostly so as not to burn holes in the Persian rug).
Our office area had carpet,the service dept. had vinyl tile.
(with a pattern that hid small dropped parts well...)
My office is all nylon carpet. I've measured the ESD potential with
the electrometer and found that the carpet is not a serious problem.
My guess(tm) is that it's because I haven't cleaned (or seen) the
carpet in 20 years. Also, the RH is now about 85% and rarely drops
below 30%, which helps considerably.
Our printer guys used to do some repairs in their office area,on the
carpet,and they really didn't pay much attention to ESD.
Printer repair is mostly mechanical (which is why I like doing it).
The electronic part is mostly board swapping. I also used to do it on
the carpet, but when my back started protesting, I switched to a
proper (low) table. However, one of my work tables is just a steel
office desk. The formica or plastic top is a problem. I avoid using
it for anything other than storage or paperwork:
http://802.11junk.com/jeffl/pics/office/slides/radio-mess.html
In my never humble opinion, the trick to ESD protection is to do some
testing with an electrometer. There's no way to reduce ESD to what
would be considered safe in a production environment, but testing will
uncover some potential problems.
http://802.11junk.com/jeffl/crud/pace-desoldering-station.jpg
Man,that IS an ancient model!
It cost me about $25 plus about $50 in parts about 20 years ago. At
the time, comparable desoldering stations were going for perhaps $800.
It may be old, it may clog, it may be clumsy, and it certainly is
ugly, but it works. However, during the same time period, components
and lead spacing have shrunk to the point where it's basically
useless. I still use it for thru-hole component desoldering, but for
SMT, I'm shopping for a hot air device.
Of course,you could order a new handle assembly to use with your base.
And the longer DS tips.
Good idea as a longer tip would be better. I hate to admit that I'm
still using the same 20+ year old tip. When I bought it, the original
tip had to get pounded out and replaced.
BTW,I was wondering if the automotive high temp anti-seize lubricant made
by Permatex would help with the tip seize problem? It's rated up to
1600degF. item 81343
It's made to go on spark plug and O2 sensor threads.
It's got a lot of aluminum and graphite in it.
http://www.permatex.com/products/automotive/b_lubricants/specialty_lubricants/Permatex_Anti-Seize_Lubricant_a.htm
The problem with that stuff is that it has copper, graphite, and
aluminum in it. Fine for spark plugs in an aluminum or iron engine
head. However, most soldering iron tips are either nickel or chromium
(the non-solderable part) plated. The copper will eventually go into
solution (galvanic corrosion) and create a ceramic like coating. Avoid
the copper stuff. What methinks you want is a nickel based anti-seize
to match the tip plating.
http://www.drillspot.com/products/280558/Loctite_77124_Nickel_Anti_Seize_Lubricant
http://www.drillspot.com/power-tools-and-metalworking/lubricants/anti-seize-compounds/
Permatex and Loctite both carry it. It's suppose to be for stainless
and works to 2600F. I tried some on a big thermostatically controlled
iron, with a huge threaded nickel plated copper slab of a tip, and it
worked as expected. No stuck tips.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558