Oops.  My picture was goofed up with text running through it.  Sorry.  Here,
I fixed it.

Steve -  YES, I've seen a similar design, in fact I "laid one out"
s-i-m-i-l-a-r, but the
entire PCB began as a 4-layer board.  I designed (actually re-designed) 9
PCB's that were produced in a single array, all 9 PCB's were (of course)
fabricated at the same time.  Some of the daughter boards were required to
be 2-layers, others 4-layers.  Some of the 2-layer sections had been in
production as 2-layers and had been certified as 2-layer, I was not allowed
to "add" layers to those PCB's, when this panelization scheme came up.  The
"staple wires" were put in beetween main and various daughter boards in such
a way that the interconnections were all made using bare ~.028 dia lead
wire.   After wave solder, cleaning and testing, the array was de-panelized.
Then, the wires between boards were formed using a fixture.  When the board
jumpers were formed, this entire 3D Frankenstein-like assembly held it's
shape and was installed, as one unit, into the housing.  The savings in that
case were realized not by making "less square inches" of the 4-layer, but by
the combined savings of having only 1 PCB tooled, vs. 9; processing one
panel through assembly, instead of nine.  This concept was not mine, but it
sure seemed like a good idea.  But, an ECO to one was an ECO to all, and
replacement PCB's needed to be cut from array's or tooled separate as
replacement parts. Let me try to illustrate, (I realize these characters may
"wander" around in your e-mail viewer, but here goes):

___________________________
|                                                            |
|      -------+----+----+----+-----+------     |
|      |   __ |___|___|___|___|__   |      |
|      |  |     +     +      +     +     +   |   |      |
|      |  |__________________|   |      |
|      |_____________________|     |
|__________________________ |
This example has only one daughter bd with "staples" connecting
it to the "main" bd, which it is cut from.  My design was about 9" X 12".
We cut our temporory connector tabs from between daughter bds
with one of those new-fangled water knives.  ...but in my case, there were
9 daughter boards, a mix of 2L and 4L, fabricated by simply eliminating
inner and outer layers in each section as we desired.  Did that make
sense?....
(That was a fun project)   Don't know how production success was. Regards,
Russ

Russ Steiner, CID
National Sales Manager   Controls/inc.
1 Technology Way     Logansport, IN 46947
Voice 248 887-2970     Fax 248 889-9532
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Contract manufacturing with a unique feature... Comfort.
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-----Original Message-----
From: Stephen R. Gregory <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Wednesday, February 10, 1999 1:07 PM
Subject: [TN] Assy: Strange new PCB Technology?


>Hi everybody!
>
>     We've got a series of boards that we build for a customer who's
product >is a WEB/CATV sort of system. The main board is what they call
their
home-box, or set-top board. It's got a little of everything on it...a
digital section
>around the CPU, some RF circuitry with the metal sheilding, and analog
areas. The system is working and they've got customers, so the next logical
step
in the product life cycle is cost cutting, figuring out how to do the same
thing only cheaper.   Yesterday my contact at our customer (the materials
manager) asked me
if I have ever built a board that had two complete and distinct sections,
one
a 4-layer section, and the other a 2-layer section, that was joined by some
sort of "staple" (that was the best way he could describe it to me) and I
would
process it as one single board. He said he wasn't sure if the "staple" was
pressed into the PCB somehow, or soldered in. But he said he was sure that
it was said the assemblers would put it together as if it was one board.
I told him lordy no, I have never heard of such a thing. I've done
boards that are different layers connected by a flex circuit or a ribbon
cable, and that was a completely separate operation towards the end of the
process, but never processing two different layer boards at the same time
as one board...have any of you heard of such a thing? My customer said that
this was something that a fab house down in southern California had told to
one
of their engineers in their efforts to reduce costs...says that they can
save
on their PCB cost by doing something like that since the only section of the
board that needs to be 4-layer is a small area right around the CPU.
      My first reaction was holy-taco shell batman, how in the world is
something like that gonna stay flat? I can't visualize something like
that...is the materials manager just trying to mess with me or does
something like that really exist?

-Steve Gregory-

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