Homebrew PCBs

Hi folks. I was just looking at some of the boards in the 
photo/files area and i must say thats very good work. None of my 
homebrewed boards came out as good as those.
 I was just wondering , How narrow can a trace be etched in a 
homebrewed board? I'd like to know if anyone has tried running a 
trace between the pins of an IC. The reason i ask this is because 
there are times when the only solution to running a trace(s) is to 
route them between the pads for the IC pins, can this be done?



Net.

>From: "Larry" <nettron1000@...>
>Reply-To: Homebrew_PCBs@yahoogroups.com
>To: Homebrew_PCBs@yahoogroups.com
>Subject: [Homebrew_PCBs] PCBoard trace width
>Date: Sun, 20 Jul 2003 12:18:59 -0000
>
>  Hi folks. I was just looking at some of the boards in the
>photo/files area and i must say thats very good work. None of my
>homebrewed boards came out as good as those.
>  I was just wondering , How narrow can a trace be etched in a
>homebrewed board? I'd like to know if anyone has tried running a
>trace between the pins of an IC. The reason i ask this is because
>there are times when the only solution to running a trace(s) is to
>route them between the pads for the IC pins, can this be done?

I can manage 10/10 design rules, using a LaserJet IIIp. No problems putting 
a track between IC pins.

Leon
--
Leon Heller, G1HSM Tel: +44 1424 423947
Email:leon_heller@...
My web page: http://www.geocities.com/leon_heller

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I don't have any problem routing between IC pins. Usually use 8 mil 
traces and I use rectangular pads 70 mil across the IC and 40 mil 
along it - gives extra space between pads while still leaving lots of 
meat to solder into. Works fine with 50 mill circular pads too but 
its my soldering that worries me, not the etching :)

Having only recently started etching my own boards I can tell you the 
three things that seemed to have the greatest impact on the boards I 
made.

1) Overexpose! My kit says 6 minutes, I go 8-10. You'll have to 
experiment to see how long you can get away with. Underexposure makes 
development harder and you're much more likely to have an invisible 
film of resist left over, screwing up your etching. I was worried 
that overexposure would screw up my traces but, I've seen zero 
degredation of the developed image and a great improvement in the 
etched boards.

2) Brush the board while developing. At first I was scared to 
actually touch the board with my brush. I just used it to swish the 
solution around. Made for long etching times and a fair bit on trace 
undercutting (eating the trace from the sides - under the resist).

3) When the board looks developed - its not! Keep brushing for 
another minute or so - if you watch carefully you'll still see some 
coloured mist coming off the "clean" copper. Thats the invisible scum 
that can screw up your boards.

Of course you'll have to experiment a bit to get it right. Make a 
small circuit and repeat it several times over a larger board, then 
try things out. You'll likely lose a few but the gained experience is 
invaluable - like when you etch that 48"x56" 25000pin monstrosity!

--- In Homebrew_PCBs@yahoogroups.com, "Larry" <nettron1000@y...> 
wrote:

>  Hi folks. I was just looking at some of the boards in the 
> photo/files area and i must say thats very good work. None of my 
> homebrewed boards came out as good as those.
>  I was just wondering , How narrow can a trace be etched in a 
> homebrewed board? I'd like to know if anyone has tried running a 
> trace between the pins of an IC. The reason i ask this is because 
> there are times when the only solution to running a trace(s) is to 
> route them between the pads for the IC pins, can this be done?
> 
> 
> 
> Net.

track between ic pins (standard dil) is absolutely NO problem.
you can even do this with plotting resist on.

i think with photo process it would be well possible to make two traces 
between the pads.
but i never tried because i didn't need.

i always make very long pads for dil ics. up to 4mm long.
but i make them only wide enough to allow some copper at the sides of the 
drilled hole left.
so you get a good solder joint and can very easily run a thick track 
between pads.
i don't use round pads for dil. i like to have bigger pads, especially with 
"experimental" boards, this allows soldering parts in and out
some times if needed and also makes other modifications easier.
with my first boards years ago i sticked to the standard pads set in the 
software.
these were designed for throughhole plated boards, thus having only a small 
residual ring around the hole.
when i drilled sometimes this ring was broken on one side. you can imagine 
the mechanical stability was very poor.
now i use pads of 3mm or so on the simple boards where size doesn't matter.


Also for transistors i often use oblong pads.

i think worst components are 2 row connectors, maybe d-sub connectors and 
plcc sockets.
these components often can't have oblong pads because they have multiple 
rows of pins.
then i use round pads which are just small enough to run a track between 
two.

i hope this helped....

regards
stefan