Homebrew PCBs

Hi,

I worked in the semi industry for a while.  They are fastidious about
keeping static down to a minimum.  And rightly so.  The reason is more
subtle.

Your analogy about driving doesn't really address the issue and really
tends to obfuscate the issue.

But what the heck,  let's stay with the driving example.  If I drive my
car at 200kph over few pot holes it's likely I won't wreck the car but
perhaps I've started a small crack in a tie rod or suspension member.  Now
since I rarely drive 200kph I really don't run the car at the limit so the
crack which is slowly getting bigger doesn't impact the operation of the
vehicle so much that I'd notice.

Then one day I hit a tiny bump in the road and the crack fractures
completely causing the car to veer right, killing the 7 year old girl at
the cross walk.  It's chalked up to mechanical failure and perhaps someone
tries to sue the automaker.  There's no real causal relationship with the
pot holes a few years ago yet the little girl died.

Extreme example?  Yes.  Much like I've yet to be hit by lightning yet a
number of people die from that every year and knowing that I avoid
swimming in the lake in a lightning storm.

In the electronic component industry that high voltage low current zap
(which if under 5Kv you can't really feel) can be enough to damage but not
destroy the device.  This is key.  The rise time of a switch may go from
8nS to 14nS.  That op amp may be a tad noisier or generate a tiny bit more
heat through a higher resistance junction than a non-damaged part.

It's the partial unseen damage that can cause issues.  Not today.  Not
tomorrow.  But maybe next week or next month or next year.  That junction
wasn't designed to be that thin or to run that hot.  Over time, the heat
takes a toll and eventually the part and the product fails.

Not everyone who builds PCBs at home builds frivolous projects that do no
harm when they fail.  A failed milling machine controller that has the
table move erratically destroys a tool bit snapping it off and flinging it
across the room or into someone is always a possibility,  even if small.

But worse I believe you are doing a disservice to manufacturers who sell
kits or board level products with a long term warranty.  Telling people
that it's all right to ignore anti static procedures invites potential
damage that you don't have to pay for.  Someone takes your advice and
treats electronics roughly and it fails 5 weeks later.  There's no causal
relationship to your advice and the failed part so you don't have to take
any responsibility.

Best Regards,

John Dammeyer

Automation Artisans Inc.
http://www.autoartisans.com/ELS/
Ph. 1 250 544 4950


-----Original Message-----
From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
On Behalf Of Stefan Trethan
Sent: Saturday, December 24, 2011 12:49 AM
To: Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] PCB holder




What's wrong with staying realistic about risk?

We could do all sorts of things safer - say reduce traffic deaths to
almost zero by driving no faster than 20mph, and yet we do not do it.
Here no lifes are at risk - just $1 components, why let yourself be
slowed down with ESD measures?

Having used only minimal ESD precautions all my life and never seen a
failure, and frequently testing designs with ESD guns gives me some
confidence that there is a certain amount of unwarranted hype
associated with this topic.

Would you care to elaborate using specific examples of how you damaged
components with ESD?
For some reason peope never can back their fear up with specific
incidents when I prompt them. The examples should _not_ involve either
a huge production quantity (where the statistics get you), or very
early CMOS components (which were much more sensitive).

This is similar to the temperature when soldering issue. There are old
books and stuff that suggest clamping heatsink tweezers onto
semiconductors while soldering, and generally put the fear of god into
beginners. When they ask for advise I have to first disabuse them of
the notion that components will just blow up as soon as they get
slightly warm. Modern components can withstand soldering heat to an
amazing degree.

It is not helpful to overrate risk, it just puts people off when they
really should be getting stuck into some hands on experience. I let
the magic smoke out so many times with stupid mistakes, why worry
about one or two components that may or may not have been damaged by
ESD?

ST

On Sat, Dec 24, 2011 at 9:11 AM, Boman33 <boman33@...
<mailto:boman33%40vinland.com> > wrote:
> You might be lucky but do not spread bad info.
>
> Bertho
>
>
>
> From:  Stefan Trethan   Sent: Saturday, December 24, 2011 02:28
>
>
>
> Come on people, stay realistic.
> Steve is most likely not going to make assemblies for an aircraft or
> anything like that.
> Nor is he going to run thousands of boards a day from his homemade PCB
> holder.
>
> In a typical home shop or even development lab setting you'll not
> notice the effects of ESD measures - there just aren't any failures
> even if you take no measures at all.
> ---<snip
>
>






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