Joe, This is really, really cool.
When I first read your paper on the Occam process, my first reaction was
"Darn, I wish I woulda thunkathat".
Sure, it may have some bugs to work out. Any really good
paradigm-shifting idea has bugs to work out.
Never mind the naysayers. They are everywhere, usually doing nothing but
neighing.
Just focus on the issues and work them out.
And it shall be done....
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joe Fjelstad
Sent: Tuesday, February 26, 2008 11:49 AM
To: [log in to unmask]
Subject: [TN] Do it yourself Occam assembly
Greetings folks,
I have tried to sidestep most of the controversy associated with Occam
and solderless assembly as much as possible to focus on getting projects
done.
However some controversy is, I suppose, good as it keeps interest
alive. As Yogi Berra might have noted: "If it wasn't controversial,
everybody would not stop to avoid talking about it"... ;-) So I thought
it might be worth while to give everyone here a way to make their own
Occam type assemblies using legacy through hole components at their
desk in a matter of minutes. This will allow folks to form their own
opinions
as to the fundamental viability of the concept for the future.
This is only for demonstration purposes but I trust it will open some
minds to the possibilities that exist in the fundamental concept. The
following will work for one or more metal layers but designs should be
kept simple for practical reasons.
1) Obtain a piece of corregated cardboard box (Option: draw your
circuit
layout on the surface)
2) Tape a piece of clear polyethylene (a half a common sandwich bag
will
do) to the cardboard
3) Place a second larger piece of card board underneath to keep the
desk
or other surface clean
4) Clip the leads down slightly (one can intuit for themselves how
much
to clip off)
5) Push the leads through the polyethylene into the card board at
(the
polyethylene should seal the leads reasonably well but there might be
some small leakage to the card board) Pin holes might be required as
starters for many leaded devices. Shorter clipped leads will be easier.
6) Cut a hole in another piece of cardboard that will encompass the
components and provide a resin dam wrap polyethylene around the exposed
edges (this step is optional depending on size of the assemlby)
7) Mix up some 5 minute epoxy and pour over components (try not to
get
too many bubbles entrained)
8) Remove the assembly and trim the leads as necessary
9) Using a silver ink pen (available from some circuit equipment
providers) draw your interconnections between contacts
10) If cross overs are required, use some nail polish at the
intersection.
It can be used for cover coating if desired.
11) Attach battery and go have some fun. :-) Notes. 1) If you want to
include connectors, have the mated portions in
them in case some wicking occurs.
2) Small batteries (or screw top battery holders) can be embedded if
desired.
3) Dome switches are a low profile choice.
4) A piece of 100 mil center "bread board" without plated through holes
can be used in place of the cardboard for greater placement accuracy if
that is of interest.
5) The process will work for SMT devices as well but the devices need
to be kept flat and a sanding step will likely be required to clean off
resin from contact surfaces.
6) The conductivity of silver ink is about 10% of copper so stay away
from
high power designs. (keep it simple)
This is obviously not a production technology but it does provide a
simple demonstration. I sent Steve Gregory a photo of a simple assembly
for those interested to view what such a simple assembly looks like and
he has kindly consented to post it. Here is the link:
http://stevezeva.homestead.com/files/Through_hole_Occam_prototype.jpg .
It could also serve the needs of some hobbyists and could be a fun
project for anyone having children interested in electronics.
While I appreciate the skepticism of those who question the potential
of solderless assembly, including many long time friends whom I respect
and hold dear. I trust that there will be some increase in acceptance
of the concept
with the data that we are in the process of generating.
It may well be that the final versions of Occam assemblies will not
look very much like today's assemblies. They could well appear to look
more like metal jacketed bricks with interconnections on the surfaces to
which other assembly elements (keyboards, displays, etc.) can be joined
using other solderless techniques such low profile connectors or
conductive and/or anisotropic conductive adhesives.
The brick like structure should also prove great for product design
security. Remember when Apple announced the I-Phone last year? 3 days
later there was a public tear down of the product design an everyone
could see what was
going on. It will be much more difficult with the solderless brick
approach.
Fortunately, wholesale change within the industry is not required for
the process as identified. The equipment, materials and chemistry exist
for every process required. More importantly, there are some new
materials and processes on the horizon that appear extremely well
suited to the solderless approach.
Another point that needs to be addressed related to the process
environment.
A number of folks have registered alarm or at least concern at the
thought of having plating equipment under the same roof as pick and
place equipment (or vise versa). To allay such concerns, one need only
go to just about any PCB shop in the world to see precision equipment
(drills, lasers and imaging
equipment) under one roof with a plating shop. The process areas are
physically and environmentally separated of course. The PCB industry has
operated in such a fashion since the 1960s.
Changing topics, I found the following quote from a Test and
Measurement World article from October of last year.
http://www.tmworld.com/article/CA6482921.html
"In 1999, Stig Oresjo, then of Agilent Technologies, conducted a major
study of solder-joint defects on printed-circuit boards (PCBs). The
study, which at the time provided the most definitive data on the
subject, involved 15 companies and more than 1 billion solder joints.
Oresjo concluded that although companies claimed defect levels in the
range of 75 to 150 defects per million
opportunities (DPMO), the reality was 5 to 10 times that high."
In Oresjo's original study, he found the following defect distribution:
1) 41% Solder Opens
2 ) 20% Shorts
3 ) 20% Solder Quality
4 ) 8% Placement
5 ) 8% Electrical
6) 3% Other
It appears that almost 80% of the problems are related to soldering
(90% if the 8% for placement is included but I am sure it is much
better these days.) The 8% electrical problems cited are, I assume,
parts related problems of unspecified cause.
While on the subject of electrical failures, does anyone here have any
data on how many components are damaged by the temperatures associated
with the soldering process? Also how many of the electrical failures
might have been caused by poor cleaning? I have heard a lot of anecdotal
information but no hard facts. I guess I am wondering, has there been an
identified and measured effect of the lead-free assembly on first pass
product assembly yield compared
to tin-lead solder?
I would prefer an open forum answer to these questions but I realize
that there might be some discomfort so if anyone prefers to respond off
line, that is fine. Thanks in advance for any input on the topic.
Best wishes to all and have some fun with the table top solderless
assembly...
Joe
**************Ideas to please picky eaters. Watch video on AOL Living.
(http://living.aol.com/video/how-to-please-your-picky-eater/rachel-campo
s-duffy/
2050827?NCID=aolcmp00300000002598)
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