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Date:         19971119
From:         Richard Mustakos
Organization: mrj.com
To:           Jaap van Ganswijk
Subject:      Home built PCB's

I don't remember where, but some time ago I read an article on environmentally sound home manufacture of PCB's. The upshot is that you can have as complex a design as you want, in terms of layers, but that you need to make a through hole mask as well.

You Need:

• a sturdy piece of thin fiberglass (or some other insulator)
• a laser printer with a straight through paper path conductive paste, I think it is silver based, but there may be a squeegee

The procedure is this:

• Make each lead mask layer,
• Make a through hole layer
• Invert all layers (traces white and open space black)

• print side 1 negative on the plate
• squeegee conductive paste into the places where there is no toner
• (I think you bake it to set the paste, but I'm not sure)
• print though hole layer negative on top of side 1
• squeegee conductive paste into the places where there is no toner
• bake, if needed

• print side 2 negative on the plate
• squeegee conductive paste into the places where there is no toner
• bake, if needed
• print though hole layer negative on top of side 2
• squeegee conductive paste into the places where there is no toner
• bake, if needed

• print side 3 negative on the plate
• squeegee conductive paste into the places where there is no toner
• bake, if needed
• print though hole layer negative on top of side 3
• squeegee conductive paste into the places where there is no toner
• bake, if needed

• ...

Good points:

• There are no chemical pollution as a result of this process
• It will make boards of arbitrary complexity

Bad points:

• your laser printer has to register fairly well
• you have to be good with a squeegee
• you have to be careful not to damage the existing traces
• it is labor intensive
• I think the conductive paste is expensive, but I'm not sure
• you can only solder to one side, so you can only have components on one side unless you do surface mount for some and dips for others, then the dips have to be on one side, and the surface mounts have to be on the other.

I'd like to give credit, 'cause I kow this is someone elses idea, but I'll be damned if I know whose.

Good luck
RM

Date:    19951211
From:    Gilad Barak
To:      homebuilt-l mailing list [gone]
Subject: Re: Wow, real homebuilt discussions...

On 19951208 RZH wrote:

My biggest technical challenge right now is converting my prototype designs into printed circuit boards (I can't really afford to pay to have it done, and they are complex enough that I feel it would be very difficult to do myself). How do you guys do this....or do you? I'm talking about several 40-pin dips, several 28-pin dips, and 2 dozen or so glue chips (a single board computer, really) on a double-sided board, maybe 8 x 10". I've played with Easytrax, but wonder about etching and DRILLING something that big!

There is a Homebuilt FAQ (www.faqs.org/faqs/homebuilt-comp-FAQ/, Jaap) dealing with PCB layout software and home production methods.
I just ordered from the UK a type of transperancies which were described in Elektor magazine around last spring. They are fed into a laser printer or a photo copier and then transfered (heat of an iron) to the copper clad to create an etch resistant mask. Once I try it I will report how it is. There is a similar product sold in the US (by a company in CA called Dyna-art if I am not mistaken) which was described some years ago in Circuit Cellar Ink. I tried once the same method with simple transperancies, but the results were less than desirable.
Drilling is a pain. You must obtain the drills used in the PCB industry. If you have access to a PCB plant they may give their used ones for free. They have o discard them after such and such drills, but they are still perfect for home use. The main problem with these is that although they are very thin sometimes their shank is a bit thick (because they have to fit into these huge automatic drillers) and not always fit a Dremmel chuck. 8 x 10 for a homebuilt seems a bit big and difficult to handle. A typical microcontroller SBC (Micro*, RAM, ROM, address ecoding and some I/O) should fit easily in a 4 x 6 or so when using double sided. I don't know your design but 24 chips for glue logic seem a bit high, but even this should fit in something around 6 x 8.
Easytrax is nice because it is the only package I know which has a simple router (a track at a time) and has no restrictions. Recently on Simtel appeared a windows based package called PIA* which looks good. It has an autorouter good enough for home use, it is very simple to operate and registration is about $50 which seems a good deal for what it gives (The unregistered versin has no saving capabilities). There are two commercial packages from the UK which have an entry level version of less than $100 but I have not had the chance to evaluate them (one of them has a demo version available through FTP). Don't have their names with me bu I can check if you wish (or check recent issues of Elektor).

Hope this helped a bit,
Gilad

ftp.cdrom.com/pub/simtelnet/msdos/cad/ - Simtel's CAD* stuff (also for PCB's) in the USA
mic5.hensa.ac.uk/mirrors/simtelnet/msdos/cad/ - Simtel's CAD* stuff (also for PCB's) in the UK

bj@headwaters.com
Date:    19951211
From:    Brad Rodriguez
To:      homebuilt-l mailing list [gone]
Subject: Re: Wow, real homebuilt discussions...

On 19951208 RZH wrote:

I also have a strong interest in languages (C, FORTH) for these little systems, as well as operating systems.

Have you a copy of my ANSI Standard CamelForth for the Z80? (Easily ported to other 8-bit CPUs.)

My biggest technical challenge right now is converting my prototype designs into printed circuit boards (I can't really afford to pay to have it done, and they are complex enough that I feel it would be very difficult to do myself). How do you guys do this....or do you? I'm talking about several 40-pin dips, several 28-pin dips, and 2 dozen or so glue chips (a single board computer, really) on a double-sided board, maybe 8 x 10". I've played with Easytrax, but wonder about etching and DRILLING something that big!

I've been _really_ pleased with AP Circuits' prototyping service. I saw them advertised in Nuts & Volts; they'll do double-sided boards with plated-through holes (!), as few as two (2) boards, with next-day service (!), for something like Cdn$0.85 per square inch plus a Cdn$85 setup fee. (Last time I checked, that is. A recent ad says US$90 for two 5"x6" boards.) The limitations: no solder mask or silkscreen; rectangular boards only; no gold-plating (e.g. for edge connectors). They'll take an output file from Easytrax, via modem* or FTP. Email staff@apcircuits.com, or www.apcircuits.com/. I've used them for a couple of projects now....believe me, it's worth the money.

Regards,
Brad Rodriguez                      Computers on the Small Scale
Contributing Editor, The Computer Journal... www.psyber.com/~tcj
Director, Forth Interest Group......... www.taygeta.com/fig.html

See also

See also (elsewhere):

www.twyman.org.uk/PCB-Techniques/PCB-Assembly-Techniques/	Soldering and desoldering tips for SMT components by Harvey Twyman
www.faqs.org/faqs/homebuilt-comp-FAQ/	PCB Making FAQ
www.aracnet.com/~gpatrick/	Designer's Den: Info about PCB materials, isolation distances, trace width's etc.
www.apcircuits.com/	Download the file "newuser". They do a great job and cheap too!
www.thinktink.com/whoare.htm	Green CirKit: Info about PCB manufacturing with virtually zero environmental impact
www.aracnet.com/~gpatrick/	Lot of info about pcb*'s, a.o. current and voltage capacity.
www.super-tech.com/root/
www.eskimo.com/~randyn/