Homebrew PCBs

On Thu, 23 Feb 2006 09:09:15 +0100, Richard <metal@...> wrote:

> Lyman, congrats on your first photo-board.
>
>
> You didn't say what your exposure tool was; but at the
>
> 1-mil level, you may well be running into effects of poor
>
> collimation; as much as any other factor.


Yea sure, making 1mil traces, that's 25um wide, a typical pcb has 35u of  
copper thickness.
So anyone telling me he is making PCBs with traces that are actually  
narrower than they are high is either very, very good, or a liar. 'Cause  
without directional etching like used for ICs that's just not happening.

I think industry standard is 2mil minimum, but that's on thinner copper  
and with spray etching.

 From my experience, anything below 6.66mil is unreliable due to  
underetching. And that's the same with toner transfer and photoprocess. 4  
or 5 mil traces i could believe with a well set-up etcher, but 1mil, come  
on! And it makes no difference if that is photoprocess or toner transfer,  
the underetching is getting you first with both methods.

So, unless someone shows me a PCB that actually has 1mil traces _made_  
_at_ _home_ i'll just take this at joke value, because i've been there,  
tried that:

<http://www.trethan.at.tf/pub/img1/PCB2.JPG>

that's toner transfer.

ST