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

One of the big problems with static damage is often it is cumulative
rather than a one shot destruction. When the RCA CD40xx series
was new we were using them and the spec for leakage was around
100 na. In the world I worked they would be tested then to burn in
boards then tested some more burn in ect. It was found that about
the time they got to the product line they were failing. A study of the
data determined they were arriving with a leakage of less than 10
ma and this value was increasing every test cycle. They wee being
test on an older Fairchild tester using a Delta temperature chamber
and a carousal based handler using plastic carriers. It turned out
that the plastic carriers sliding down the anodised handler was
building up a charge and when they were inserted into the test
socket they were punching holes thru the gate. Every hole added to
the leakage. The solution was to tear the handler apart and strip of
the anodising plate it with nickle I believe.

At another mafg. place I worked we were using the RCA 60673 fet as
the first if amp and one of the rework ladies was always cutting the
ground off her iron. If she changed the fet you could bet the new one
was bad.

I would be concerned about buying anything from a place that used
no static controls at all. I am sure I have seen memory sticks
zapped at shows while being installed.

Garry

To: CAD_CAM_EDM_DRO@egroups.com
From: Jeff Barlow <jeff@...>
Date sent: Sun, 26 Nov 2000 19:18:58 -0800
Send reply to: CAD_CAM_EDM_DRO@egroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Re: Cleaning Circuit Boards and "Static" rant

> Ballendo,
>
> Ok, I guess I'll jump in here and open my big mouth. My experience
> with (absence of) static damage would seem to parallel that of Mariss.
> I worked with some of the very early MOS devices at TRW back in the
> late sixties and I never popped one then, and never have since.
>
> I fully understand why this *should* be a problem, but I've never worn
> a wrist strap, or used any of the other standard tricks, and never had
> it happen. It may just be that I'm careful about the order in which I
> touch things, without really thinking about it.
>
> The closest I've come to seeing this problem in the real world was in
> some production boards that were showing a high failure rate in
> testing. I was the "responsible engineer" for these and spent a quite
> a while chasing this. To make a long story short, it came down to
> either ESD damage or a bad batch of chips, and I was never sure which.
>
> None of this proves anything, of course, but I tend to think ESD
> prevention measures are generally over done.
>
> Jeff
>
>
> On Mon, 27 Nov 2000 02:36:32 -0000, 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?
> >
> >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?!?
> >
> >Gotta be honest here. This one's hard to swallow!
> >
> >Surely the several thousand volts of static can impact a 50V device.
> >Even at the infinitismal current?!?
> >
> >Is this something you can "back up" with documentation. (not a
> >challenge, I just would like to know for myself). I'm a science kind
> >of guy. You know, reproducible results, peer review, and all that :-)
> >
> >Or is this just an observation, based on your own experience? (which
> >may include EXCELLENT static practice, without you "consciously"
> >doing it) Seen THAT with "experts" ALL the time! (ability to make the
> >"correct" decision without "thinking" about it.)
> >
> >Ballendo
>
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