As an addition, I have looked into PCB prototyping and the 4pcb.com
deal, as well as others, and they seem to actually be quite a good deal for
what they offer. I wouldn't think it would take much work to lay the board
out with their software if they want a specific format, but they may limit
you to one usable item per board, aka... not putting 10 SIMMs on one board.
So, you end up with 3 prototypes, and you can order more with greater
variable specifications, and without any tooling costs. I can't see how
trying to do it all yourself would be better than using even a lower end
boardhouse. Obviously, a normal boardhouse will give you a real, 100% item,
but is that necessary for what is being made? It should still work either
way, and if the lesser cost means that it actually happens, then why not?
It just depends on how much you want to spend, and how many people are
interested.
-Chris
----- Original Message -----
From: <[EMAIL PROTECTED]>
To: "Compact Macs" <[email protected]>
Sent: Friday, August 26, 2005 6:23 PM
Subject: Re: .047" Thick Copper Clad Board for PCBs
As an FYI...
.047" (actually 3/64") Copper Clad Laminate is an industry standard
thickness and when you include plating (typically <.0005") and solder
mask, the board thickness will increase .002" - .003". A typical 1/16"
board (our typical thickness) measures .0645" or .065" depending on where
you take your measurement. I am not sure why people have had a difficult
time finding this (3/64") stuff, but it is quite common. If the only
standard stock was 1/16", imagine how thick a 16 layer board would be! We
have 4 layer boards which are 1/32" total.
Regarding the photo-resist. I "think" our local board house purchases
their laminate pre-coated... We used to purchase it that way when we made
one-off prototypes. You could certainly (using a silk screen) apply
(liquid) resist over your track & pad areas, but this method is not common
these days (the screens stretch and there are definite registration
issues).
Designing a SIMM should be fairly simple, but tooling costs would kill you
unless you had a fair number of buyers. I believe it runs us something
like $500.00 for an initial production run of 5 flats (roughly 64 sq. in.
each)... This includes all gerber and tooling costs. Granted you would
get a fair number of SIMMs in a flat, but how many do we need? I know of
the low cost board houses (4pcb.com among others), but they do not provide
the full range of services you get from a traditional pcb mfg. (one I
tried insisted we supply the files in a specific gerber version which our
CAD software does not support).
Is there really enough demand for this stuff to justify the cost?
Derek
About 2 years ago Gamba and I collaborated on making a ROM SIMM to
fit the SE/30, which had the IIci ROM code on board. When we were
nearly done we discovered that the ROM SIMM in the SE/30 is around
.050" thick, whereas all the modern PCBs and commonly available
laminate stock is .062" thick.
As it happens, the circuit boards for 30 pin SIMMs are also .050" thick.
Anyway, I found that this seller on Ebay,
<http://search.ebay.com/_W0QQsassZstarstreasuresQQhtZ-1> has several
lots of .047" thick copper clad laminate stock. No connection,
relationship, etc.
I don't know if anyone else is making boards, but if you are, this
could be useful. I've been thinking about trying to make some IIfx
SIMMs...
On the topic of PCB making, if one starts with copper clad stock, how
does one put a photosensitive surface on it, so that one can do
photolithographic circuit board masking for etching? Is there some
kind of stick-on material? The only clue I came up with seemed to
indicate that one needed an expensive laminating machine.
Jeff Walther
P.S. Gamba, I hope you're still out there. Your mailbox is full,
but at least it's still active (as opposed to "Unknown User").
--
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