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'[OT] Definitly OT PCB design question'
1999\04\02@013646 by Eric Oliver

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I am attempting to design my first PCB for a PIC16C77 using Eagle Lite.  I
want to make the board as small as possible but I'm not sure how small my
traces can be.  Can I get away with .010 (decimal) thick traces ?  If the
board will run with that, can I successfully make the board using hobbyist
techniques with traces that small ?

TIA,
Eric

1999\04\02@113544 by Bob Blick

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Hi Eric,

The minimum trace width and clearance varies from board house to board
house and the type of production you are doing.

Generally most places will do .008 traces with .008 clearance no problem
even with the cheapest fastest process.

Don't attempt that with home process unless you have it to an exact
science with much practice. Try .013 traces with .012 clearance and be
prepared for some touchup.

Cheers,
Bob

1999\04\02@175440 by Russell McMahon

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Following is IMHO only. Others will disagree. YMMV.

From: Eric Oliver <spam_OUTericTakeThisOuTspamKEDCOENT.COM>

>I am attempting to design my first PCB for a PIC16C77 using Eagle
Lite.  I
>want to make the board as small as possible but I'm not sure how
small my
>traces can be.

> Can I get away with .010 (decimal) thick traces ?

Yes - but you'll be sorry and its unlikely you need to.
Power supply lines really really shouldn't be this fine.
Signal lines can be but 20 or 30 or ... will probably fit OK.
Remember pin-pin on a DIP chip is 100 mils. This will affect your
result.

>If the
>board will run with that, can I successfully make the board using
hobbyist
>techniques with traces that small ?



Not unless you have really GOOD hobbyist techniques.
eg possibly using commercial photo sensitive board etc and home
techniques.
The "iron on" solutions probably don't have  a chance and at 10 thou
its really easy to take off track A while waiting fro B to etch
somewhere else.

If you are new to this, start with something less fine.


regards

Russell McMahon

1999\04\03@161749 by Nigel Porter

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I use an ink jet printer to reproduce art work then a photocopier to transfer
image to film. In my experience, using this technique, I cannot sucessfully
reproduce tracks less than 0.014" (14 thou). ie. in my PCB software the
smallest track size used is 14 thou. If I go below this size the track tends
to break up in the copy process and becomes unreliable.

Eric Oliver wrote:

> I am attempting to design my first PCB for a PIC16C77 using Eagle Lite.  I
> want to make the board as small as possible but I'm not sure how small my
> traces can be.  Can I get away with .010 (decimal) thick traces ?  If the
> board will run with that, can I successfully make the board using hobbyist
> techniques with traces that small ?
>
> TIA,
> Eric

1999\04\04@103555 by wwl

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On Sat, 3 Apr 1999 16:45:30 +0100, you wrote:

>I use an ink jet printer to reproduce art work then a photocopier to transfer
>image to film. In my experience, using this technique, I cannot sucessfully
>reproduce tracks less than 0.014" (14 thou). ie. in my PCB software the
>smallest track size used is 14 thou. If I go below this size the track tends
>to break up in the copy process and becomes unreliable.
Have you tried printing directly onto drafting film or tracing paper -
These are UV-translucent, and I've heard of people getting good
results.

1999\04\05@091835 by Lawrence Lile

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I use different philosophies on trace thickness.  If I am going to build the
board myself, I try to make the trace much larger than 0.010".  If I can use
0.060" traces, I will, often I must use 0.30".  I rarely make a homemade
board with smaller than 0.020" traces.  A commercial board may have 0.008"
traces if I am using a good PCB house.

Your technique for making the board will also determine trace size to some
extent.  If you are using photolithography, you can make much finer traces
than, say, iron-on transfers.  Others will disagree, but I have had trouble
with fine traces and iron-ons.  (OK, flame away guys!)

I'd stay away from fine traces until you refine your technique.   Don't try
to make your board as small as possible, just try to make it AT ALL right
now.  Take your challenges in small steps.

A wise chinese sage once said:
The longest journey begins with a single step, just make sure that the first
step is not to put your foot in your mouth :)




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