Homebrew PCBs

Hi all,

What methods do back-yarders use to get the sharpest
PCB tracks? Photographic? Milling?

--- Russell Shaw <rjshaw@...> wrote:
> Hi all,
> 
> What methods do back-yarders use to get the sharpest
> PCB tracks? Photographic? Milling?

I've never done PCB milling, but I have done
photographic. And it is very sharp and professional
looking, professional looking as your mask. I've used
both positive precoated boards and spray-it-yourself
negative. Both have good and bad points, mostly
overcome by computer aided drafting.

I've used drafting tape and those rub-on shapes, and
I've used photocopies on mylar but I usually had to
repair the masks (pinholes). Anyone remember that blue
film? It was on a backing and you cut out parts of it
with an Xacto knife to create a mask. A real pain in
the neck, I hated the stuff. Just try and cut out IC
pads with an Xacto.

Steve Greenfield


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In a message dated 29-Jan-02 03:00:04 Central Standard Time, 
rjshaw@... writes:


> What methods do back-yarders use to get the sharpest
> PCB tracks? Photographic? Milling?
> 
> 

When I need best I can do without having a pro-shop do etching, I use 
contact-printing of negatives with Kepro stuff.  But I haven't done a 
home-brew "photographic" in so long I don't even know what the various 
solutions were called!

I have done nothing more complex than a 6-IC little lashup in years, and I 
get by with Radio Shack and whoevermailorderitwas "pressure sensitive" 
"rub-on" stuff.  That works really fine, if done right, actually!

Jan Rowland, Old Troll


[Non-text portions of this message have been removed]

JanRwl@... wrote:
> 
> In a message dated 29-Jan-02 03:00:04 Central Standard Time,
> rjshaw@... writes:
> 
> > What methods do back-yarders use to get the sharpest
> > PCB tracks? Photographic? Milling?
> >
> >
> 
> When I need best I can do without having a pro-shop do etching, I use
> contact-printing of negatives with Kepro stuff.  But I haven't done a
> home-brew "photographic" in so long I don't even know what the various
> solutions were called!
> 
> I have done nothing more complex than a 6-IC little lashup in years, and I
> get by with Radio Shack and whoevermailorderitwas "pressure sensitive"
> "rub-on" stuff.  That works really fine, if done right, actually!

I was wondering how much resolution the various
methods get. I've found the best printers are
epson stylus colour inkjets (400 and higher),
used with epson transparencies (its coated
with an absorbing layer instead of 'sandpaper').
Using a lightbox etc, i can get 6-8mil tracks
and spacing. Works with precoated negative
boards, and spray-on positive resist (PRP).

Hello Russell,

Wednesday, January 30, 2002, 01:14:08, you wrote:



RS> JanRwl@... wrote:
>>
>> In a message dated 29-Jan-02 03:00:04 Central Standard Time,
>> rjshaw@... writes:
>>
>> > What methods do back-yarders use to get the sharpest
>> > PCB tracks? Photographic? Milling?
>> >
>> >
>>
>> When I need best I can do without having a pro-shop do etching, I use
>> contact-printing of negatives with Kepro stuff.\ufffd But I haven't done a
>> home-brew "photographic" in so long I don't even know what the various
>> solutions were called!
>>
>> I have done nothing more complex than a 6-IC little lashup in years, and I
>> get by with Radio Shack and whoevermailorderitwas "pressure sensitive"
>> "rub-on" stuff.\ufffd That works really fine, if done right, actually!

RS> I was wondering how much resolution the various
RS> methods get. I've found the best printers are
RS> epson stylus colour inkjets (400 and higher),
RS> used with epson transparencies (its coated
RS> with an absorbing layer instead of 'sandpaper').
RS> Using a lightbox etc, i can get 6-8mil tracks
RS> and spacing. Works with precoated negative
RS> boards, and spray-on positive resist (PRP).

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And I replied:

Photographic  method  preferred.  I  use positive precoated boards and
have a frend with typesetter who is producing the positive artwork for
my  boards.  It  is  the  cheapest method. The 3 sqft of artwork costs
approx $4, and those 3 sqft ia a lot of boards!

So compared with the price of Epson transpaerncies+ink cartridges (the
most  expensive  part  -  printers  are el cheapo, consumables are the
company lives on), Someone's typesetter is the best choice.

-- 
 Best Regards,
 Zoran, Belgrade, YU
 mailto:zasto@...

Sharpest tracks for me were with lith film (Ilford)-- I use this for 
unsharp masks for BW negatives so I always have some on hand.  I do 
almost all my stuff now using Avery Clear Full Sheet Labels (when I 
am in a hurry) or Xerox mylar film.  With the avery labels I usually 
use 20 mils as the smallest trace width -- going to 10 mils I find is 
chancy.

I find the main reason for the sharpest
tracks is to run traces between pins.
All other traces should be made as
wide as possible to minimize the 
possible problems is gaps or
smearing of traces.

To go between pins you usually need 10 or 12 mil
traces.  I have no problem doing them
by laser printing or copying pcb images onto
plain paper, ironing onto standard copper
clad boards, soaking the paper off, and then
etching in a warm bath.  
Here is how I do it.
http://www.infiltec.com/seismo/pcb-home.htm
Note that it is extremely important to coat the
boards after etching with something (floor wax!)
that keeps them from oxidizing and allows good
solder flow.

Ciao,

Dave
The Inexpesive Seismometer Project
http://www.infiltec.com/seismo/

> Note that it is extremely important to coat the
> boards after etching with something (floor wax!)
> that keeps them from oxidizing and allows good
> solder flow.

I've been using Mar-Hyde clear lacquer (spray can) for this purpose. It
leaves extremely thin coating which doesn't make any problems for soldering
while completely eliminates corrosion. Works great for many years.


KPL