Homebrew PCBs

Interesting link.  After reading it I think the comment "thank Stefan for
challenging the traditional view"  has me wondering whether 'traditional'
as used the sentence is in it self a mechanism of justifying a valid
debate where there isn't one.  ESD and protection from it doesn't have
anything to do with tradition.  It has to do with sound engineering
practices.  Anytime we deviate from those practices we take the chance
that things go wrong.

For example out here on the west coast of BC a number of years ago one
could have made the statement that condominiums and other building don't
leak and rot.  And that was true until the architects and builders stopped
following the standard engineering practices and began taking short cuts
and doing designs without thought of repercussions.  The arguments against
that type of building practice was ignored.  Inspectors who should have
known better looked the other way.  The result was a a huge financial loss
to a large number of people.  The total cost will probably never be known.

I too have my PIC demo boards hung over the side of my easy chair tied to
the USB port along with the ICD-3 also tied in. I understand that I'm
taking a risk that I may damage the processor.  I'm fine with that.  But
clearly I'll state again.  I understand I'm taking a risk.

So here's the problem.  One hardly hears about ESD related problems
anymore because the majority from the chip fabrication end to the final
product use the proper procedures.  Therefore it appears as if the risks
aren't that high because it doesn't make the news.  I remember hearing a
story that Apple-II computers were failing at a 25% level once they
reached the customers.  Needless to say Apple was concerned.  Turns out
the plastic bag they slipped around the computer was damaging it.  I don't
know if it was the act of putting it into the bag or taking it out of the
bag.  In either case, Apple changed to a an anti-static bag and their
failure rate dropped to 0%.

Also the arguments have been rather black and white.  For instance, a
comment I made earlier that hasn't been referenced or addressed is that
the failures from ESD aren't always total failure issues.  The devices
aren't always damaged to the point where they fail 100% and that's a hard
fault to quantify.  For example, the device someone is using is rated from
-25C to +85C.  It's sitting in your home hobby project and never sees a
temperature outside the range of +10C to +35C.  However, the ESD damage
could for example cause the device to function erratically or unreliably
at -5C.

So my point is if you want to do as I do, and dangle the project over the
arm of the easy chair the do so.  But to use that experience as a
generalization and advice to new people entering the electronics field
that in fact ESD protection is not important and that it's a view based on
traditions with all the connotations that the word 'traditions' implies
brings me out of the woodwork to reply.

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 clausundercover
Sent: Sunday, December 25, 2011 2:24 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: [Homebrew_PCBs] Re: PCB holder




In over 1 year of playing with microcontrollers and doing all kinds of bad
things to them (not minding ESD, inadvertently shorting pins, sloppy
soldering, etc.) I have burnt exactly 1 chip valued at $6 and I think that
was due to writing the wrong fuses.
For statistics purposes, humidity is 30-50%, I'm wearing cloth slippers
with plastic soles, and the floor is varnished.

Now, I've been playing with electronics consistently for 1 year, but I
worked in risk management for 6 years. Any discussion where risk is hard
to quantify is prone to people taking extreme stances. What's difficult is
striking a balance and I guess we have to at least thank Stefan for
challenging the traditional view. Make a short visit to
http://en.wikipedia.org/wiki/Logical_fallacy and identify quite a few
appeals to authority in this thread before you hopefully draw the logical
conclusion that for the proposed target group (hobbyists) there is indeed
a lack of statistical evidence.

Quantifiable loss is a function of loss per event (how much money, time or
annoyance I waste due to ESD risk materializing) and frequency/probability
of occurrence (how many times ESD risk does materialize). That's why when
once in a few years when building my computer or disassembling my laptop
(hundreds of euro devices) I take all ESD precautions because I can't
afford the risk. Similarly when working with mains I take all possible
precautions including having someone in the room at all times.

But when playing with my $5 TI launchpad I stay on my leather recliner
with my laptop on one side and with the USB board hanging next to it. I
would regret my convenience more by obeying the "rules" then having my
board toasted once.

I won't sweat over the principial concern that I am going to build an
unsafe machine. If I depend on the safety of my build I am hiring someone
to do the job.

In a business situation the picture changes radically. I would probably go
with the conventional wisdom there without questioning it if I afford the
cost.

--- In Homebrew_PCBs@yahoogroups.com
<mailto:Homebrew_PCBs%40yahoogroups.com> , "within walking distance"
<wkehr@...> wrote:
>
> --- In Homebrew_PCBs@yahoogroups.com
<mailto:Homebrew_PCBs%40yahoogroups.com> , Stefan Trethan
<stefan_trethan@> wrote:
> >
> > People who say "because that's just how it is" or "end of discussion"
> > as a rule are not worth my time talking to.
>
> Some things are pretty much self evident. Using the automobile example,
you might say that a car has to have brakes, end of discussion. Just as
don't cross the street blindfolded, end of discussion.
> To an electrical engineer, this might be self evident. Considering the
amount of silvery antistatic envelopes, pink foam, pink bubble wrap, and
black conductive foam that I have been sent with components that I have
ordered, it seems self evident to the manufacturers and sellers.
>
> > 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.
> Whether it's a controller for an aircraft or a blinking led for a child,
he doesn't want a failure in either case.
> >
> > 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.
>
> I use the SMD to DIP adapters. This gives me the advantage of being able
to test the SMD device before placing it in the finished circuit. I've had
more than my share of devices that did not sit correctly on the pads and
therefore did not work. But in all this time there have been two devices
that were soldered exactly right (close up lens on digital camera to
check) , that did not work right. One part did not respond at all and one
part had some gates working and some not. These both happened during the
winter (low humidity) while I was working in a carpeted room. The same
circumstances where petting my cat will give us a shock. I now have a
dedicated wire running from the metal legs on my table to a nearby cold
water pipe.
>
> > Mike KC7NOA wrote�.
> >
> >I wouldn't use it ... I would pintch a stop sign for a flat aluminum >
surface first!!
>
> Taking apart old electronic devices that have been thrown away, like fax
machines, can yield aluminum for making this. An old, large UPS might even
have some giant heat sinks where the fins could hold circuit boards.
>







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