Re: [CAD_CAM_EDM_DRO] Re: Cleaning Circuit Boards and "Static" rant

ballendo@... wrote:

> Mariss,
>
> Not really sure I want to get into this :-)
>
> So are you saying that, based on your experience (of many thousands
> of parts handled vs. product problems) that static control measures
> are unnecessary? Or over-hyped? Or both?

Possibly over hyped, but it may also be that experienced people
practice 'invisible' static protection strategies that they themselves are
no longer aware they are doing! Doing all your work on a metal bench,
with a grounded soldering iron, and keeping one elbow on the bench
pretty much all the time will do a lot to reduce static damage.

> I am willing to learn here, but some of this just doesn't make sense.
> Am I to believe that the days' conditions (humidity, etc.) which let
> me "pull" a 1/2 inch spark to the doorknob is of no consequence to my
> electronic parts?!? Because they have intrinsic protection diodes?!?

The 1/2" spark, especially if you can hear it, will definitely blitz almost
any component. It might not damage a unit with proper high-energy
static protection on all external terminals. There is a standard called
the 'human body model', which is approximated by a resistor and a
capacitor. You charge the cap up to increasing voltages, and apply
the testing device to it both by very slow approach and by rapid
approach leading to a 'pop' discharge. When the device is destroyed,
you then have determined its tolerance level. Maxim has some
RS-232 transmitter and receiver chips that are tested to +/- 15 KV
with the human body model, which means these chips also have to
withstand currents to several amperes on a single pin!

> P.S. If what you are saying is true, it will really help me! I have
> often "put off" electronic assembly due to weather conditions...

There are techniques that are quite simple to set up that prevent
most of this trouble. The first thing is to never walk up to a bench
or table and just grab a component, board, or whatever. First, you
touch the bench or table, and let static discharge for a second or so.
(Obviously, a metal table helps.)

Jon