Morgan Leijström a écrit :
onsdagen den 22 augusti 2012 21.43.07 skrev Rene Rasmussen:
On Wed, 22 Aug 2012 19:51:31 +0100, Maurice Batey wrote:
On Wed, 22 Aug 2012 18:35:09 +0100, Anne Wilson wrote:
To be honest, I'm not competent to start replacing chips on
a RAM board, either.
It's a bit scary the first time, but if you follow one of the
really helpful video clips out there on the 'net, it's not a big
deal.
The main importance (apart from using the correct chip!) is to keep
your fingers from direct contact with the chip, to avoid any static
charge jumping across.
To this point i do not fully agree; Metal tools give much stronger discharge
than fingers. But a reason to avoid toucing is to avoid contaminating around
pins with sweat (salt, acid), fat and other dirt.
I have conductive plastic pliers for component handling, but they do not have
such firm grip as metal pliers.
Then there are more expensive metalpliers with conductive plastic handles
(conductive in this case means very very sightlyu conductive not measureabla
using standard multimeter, as it should avoid hard discharge, - just slowly
bleed away the charge)
None of the options described is as important as avoiding charges to build up.
In my workshop (i build electronics prototypes) i avoid clothes of synthetic
fabric, wear conductive slippers - if any, have conductive carpet, and
conductive mat on the relevant tables. But those are expensive is sold as
such. I have measured some cheaper rubber mats are good too.
The less expensive approach is to use a wristband.
A plus is to avoid sunthetic clothing, and you could work on such pink bubble
palstic wrapping some electronics come with, it is antistatic. Avoid metal
and plastic table, prefer untreated wood.
Or set up an anti-static workplace. That would be the correct thing to
do.
Static discharges are probably responsible for 90% of all electronics
going bad.
(not counting design errors. My favourite complaint is that designers put
eletrolytics unecerrarily close to hot components - the most common repair we
do is to replace such.)
ESD damages are not always immediately noticeable, but often age the component
so it have less life left (simply speaking)
I never touch any of my computer or electronics parts without my ESD
wristband securely connected to my workspace.
(having worked with electronics professionally for most of my life has
taught me that!)
Sounds like good advice for 20 or 30 years ago, before chips normally had
tristate buffers and a common floor covering was those polyestre carpets which
were so good for rubbing your feet on so you could give an unsuspecting victim
a shock by touching them.
Chip technology has advanced enormously. Much circuitry is wave-soldered to
the process board, thus even more immune to static discharge and dirt.
And those cheap static-producing carpets are a lot rarer.
Single chips with delicate pins are also a lot rarer.
Static charge is more likely to disrupt a functioning system, rather than cause
any physical damage.
I'd say the biggest risk to electronics today is damaging a process board by
flexing it too much.
I'd prefer a soft cardboard surface to anything else. (Protects both the
surface beneath and the electronics, and doesn't create a static charge.)
regards,
Rene
--
André
