For homemade double sided non-plated through I use fine tinned copper wire, through the board and bent over on the top and soldered to the top pad. Then use IC sockets with tape pins, not round, and you can then insert the socket, if you have position the wire correctly, and then solder wire and pin to the bottom pad.
Malcolm
I don't suffer from insanity I enjoy it!
Mene, mene, tekel, upharsin
The writing is on the wall.
Ha-ktovet al ha-kir
--------------------------------------------
On Thu, 2/16/17, 'Brad' unclefalter@... [Homebrew_PCBs] <Homebrew_PCBs@yahoogroups.com> wrote:
Subject: RE: [Homebrew_PCBs] Good techniques for cleaning up old artwork?
To: Homebrew_PCBs@yahoogroups.com
Date: Thursday, February 16, 2017, 4:42 PM
Thanks so much for all
this! Yes, I think this will be a very
difficult project. But I like challenges, even if I
fail. Unfortunately as far as I know
there are no better copies of the artwork. The mail-in
offer for these plans was out only briefly in 1976 and so
far only one person has come forward with originals, which
is what these scans were based on. Cleaning up the artwork
will take a long time but I don’t think it’s impossible
– I’d just hoped for some faster method. Recently I acquired an original
set of plans for the 1974 Mark-8 mini-computer. I have
original boards and now these, but had originally planned in
the absence of both to make clone boards from scanned copies
of the plans online. I was stunned to realize just how
badly off the scans were when I compared the
three. Likewise on my TV Typewriter.
Although I had the foresight to print every pattern after
scaling and check each individual IC, I neglected to
consider the bus connectors that stack the four TVT boards
together vertically. I’ve made it work but it’s an
awkward squeeze, because one of those connectors is skewed
slightly to the left. I have printed off several random
sections of this artwork after scaling it correctly and so
far tihngs fit perfectly. I don’t have to worry about
connecting other boards, so I can use the techniques I’ve
learned to get top and bottom perfectly aligned. But yeah,
the through plate situation is tricky. I mean, I could just adopt the
approach used by Mark-8 builders – even the original
boards, although double-sided, were not through plate. You
had to solder on both sides. I could do that, although the
original board in this case had IC sockets. Not sure how
you’d solder both sides of a socket. One other thing I’m thinking
about now.. this board is much larger than 8x11 – I’m
guessing my only option re: toner transfer is to use two
blue press n peel sheets per side? Thanks for all your help and
information! It is greatly appreciated. From: Homebrew_PCBs@yahoogroups.com
[mailto:Homebrew_PCBs@yahoogroups.com]
Sent: Wednesday, February 15, 2017 9:24
PM
To:
Homebrew_PCBs@yahoogroups.com
Subject: Re: [Homebrew_PCBs] Good
techniques for cleaning up old
artwork? Brad,I looked at your
artwork scans. WOW. Has anyone suggested that you might be a
glutton for punishment? I noticed that the first two
scans are much cleaner than the others. If you have access
to the pages that they were scanned from, you should re-scan
with the lines square to the scanning direction. This will
produce much cleaner results. Before you invest too
much time is trying to make clean artwork using the scans as
a basis, make sure that the scanning process didn't
distort the dimensions in one direction or the other. I have
found small differences in the scaling between the x and y
axes that make assembly of 40 pin ICs, or long connectors
impossible. These boards will be difficult to etch.
The combination of large open spaces and very narrow traces
may make it difficult to keep the traces from over etching.
To answer your question about plated through holes,
they can be done, but it is a bit involved. There are a
number of tutorials on making plated through holes on
YouTube. Here are two of them:Process 1: https://www.youtube.com/watch?v=KTNuTv_IQp4Process
2:https://www.youtube.com/watch?v=s3GY-j4Gh0Ehttps://www.youtube.com/watch?v=9rME-XGCcCoI
have not tried either of these processes, but they do seem
possible.� The difficulty I see with your boards is the
sheer number of holes. The possibility that one or more of
the holes, especially the small via holes, not getting
plated through is very great. Finding an open would be very
difficult, not to mention time consuming.One thing to
remember: The holes are drilled and plated before the board
is etched. This means that the holes need to be protected
during the etching process. It seems to me that the best
process for doing this would be the photoresist process. The
photomask used for resist exposure would need to have the
drill holes omitted, so the resist will tent over the holes
during etching. Drilling before photomasking has the benefit
that it makes the mask easier to align. I would suggest that
some extra pads with holes should be included on the masks
to assist with alignment. These pads would include the drill
holes. This also improves the probability that two sided
boards would have proper alignment between sides.HarveyOn 2/15/2017 6:04 PM,
'Brad' unclefalter@...
[Homebrew_PCBs] wrote:� My TV Typewriter project is
getting close to the finish line so I�m working on
lining up a new project.�What I�d like to do next
is a replica of the SOL terminal prototype that appeared in
Popular Electronics in July of 1976.� I have the
artwork for it here:�http://www.sol20.org/articles/img/PE_SOL.pdf%c3%af%c2%bf%c2%bdAs you can see, the quality
of the scan is pretty lousy.� There�s no other
sources for this that I�ve found.� I can clean it
up manually with Photoshop or Illustrator (and in fact have
started on the former) but that will take hours (months,
probably).� I�m wondering if there�s a better
technique than endlessly using the rectangle tool to remake
the traces and remote the �noise�.�I expect there will be other
challenges, being that this is a double sided board.�
There ∗isn�t∗ a way for a home PCB maker to do
thru-plate without third party help is there?� I
don�t want to send this off to a board house because of
the likely cost but also because that�s not how a
hobbyist would have done it back then.� Since this
artwork was sent to those that wrote in for it, I�m
assuming they just created it as a two sided board the usual
way and then soldered in the connections between sides via
ICs, jumper wire, etc.�I also don�t want to
completely redraw the thing.� For me, that would lose
the spiritual connection to the original artwork.�
I�m trying to leave as much of it as original as
possible.�Anyway, thoughts and
suggestions here are most welcome.�
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