On Fri, 18 Mar 2016 09:03:23 -0700, you wrote:
>Thanks for this very excellent explanation. Its doubly hard being a newbie but also trying to understand how things were done back in the day.
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>Because this is a replica, the correct look is very important to me. It would have been much easier to take the offerings available on mouser or ebay.. but the colours look wrong and the boards themselves too modern. Further, for some bizarre reason, most of the manufacturers dont bother taking a picture of the actual PCB.. just the copper side, so you cant ever be sure what color it is. Its funny how one does that and then they all do.
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The colors are biased by the board material (now available in all
sorts of colors, black is particularly nice for displays), and the
silk screening.
Silk screening of that era, if present was more than likely the same
standard green.
The look of the board is far more how the parts are laid out, the vias
(if any), and whether or not the board was computer generated or tape
laid out.
Used to be that you decided on the size of your board, then drew a 2x
master on grid paper (there were parts templates). Then you'd put a
layer of acetate over that and lay down the pads, then connect them
with black crepe tape. You'd then photograph that (backlit) with a
view camera using Kodalith film (with the two solution developer)
which develops the film to pretty much transparent or complete black
(you had to get the one that did come used for photographs, you wanted
the line version). That produced a life sized negative, transparent
where there was to be copper. (and I'm doing this for single sided or
double sided without plated through holes).
Then you coat the board (or have it coated) with Kodak KPR (nasty
stuff), expose it under short wave UV, develop it, dye it to see how
it came out, then etch it.
Very different look from today's boards, mostly due to the lack of
solder mask (some) and definitely the layout techniques on the lines.
so photoetch from the template or toner transfer from the template
will get you very close.
I'd recommend doing a single sided (I think it was) board using toner
transfer on standard FR4, and then see how close you really are.
That would give you a test model at the least.
Harvey
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>So yeah, the reason I went to these guys is, it looks like we have the right grain and right colour. I dont care so much about fire resistance, but it seems like all the G10 Ive found in my color is FR4 regardless.
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>When you guys were doing these boards in the 70s.. they were single side copper clad photo sensitive right? I tried asking Don exactly what format the boards he used came in (ie if they were just the PCB or had copper affixed), but he tends to be cryptic in his responses.
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>From: Homebrew_PCBs@yahoogroups.com [mailto:Homebrew_PCBs@yahoogroups.com]
>Sent: Thursday, March 17, 2016 12:03 PM
>To: Homebrew_PCBs@yahoogroups.com
>Subject: [Homebrew_PCBs] Re: Custom G10 copper clad
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>Hi guys,
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>I have been following this group for many months, and I am very excited to see the quality of the discussions presented here.
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>I have not contributed until now because I had little to add. I made boards as a teenager in the '60s and then into the '70s. In those days I used G-10 board. A some point FR-4 crept in, and became the standard for PWBs. Recently, I have become interested in making boards again, and am delighted to have discovered this group.
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>My 2 cents: I think the train has become derailed on the subject for G-10 vs. FR-4. It seems to me that the stated goal was to get boards that look like Don Lancaster's green G-10. There are several companies making unclad G-10 and FR-4. You only need to look at the websites to see that both are the same color when purchased as natural. The only difference between them is the addition of a small amount of Bromine to make
>the FR-4 boards flame retardant. Check this out: http://www.acculam.com/data-chart.html. Other places on this website (Accurate Plastics, inc) show samples of the material, and it can be seen that the color is the same. The color of the G-10 from American Micro Industries is the same.
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>The "green" color is called natural. Back in those days, the only color that glass/epoxy boards came in was natural or "green." The shade did vary between manufacturers, probably because of differences in the epoxies they used.
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>Since the color is the same and the goal is to provide the same looking boards, I think that the solution is to use FR-4, and specify "natural" color for the base material.
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>(Another) Harvey
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