Homebrew PCBs

This is just speculation with a sprinkling of theory, but it seems to me
that the whole electrostatic attraction thing does better on edges and thin
lines than it does on large areas. Certainly I remember most photocopies
rapidly losing filled areas while the edges got "ringy"

Because of this (assuming it's true of course), I've never had a problem
with a "pit" breaking a trace, only in pours or large pads where they're
not electrically a problem.

I also noticed, after I posted the photo, that the genuine-toner board I
tried most recently is exhibiting what are clearly (air) bubbles under the
toner which have prevented adhesion (the one I posted to show what a
trapped hair could
do<http://groups.yahoo.com/group/Homebrew_PCBs/photos/album/809517956/pic/2133723863/view?picmode=&mode=tn&order=ordinal&start=1&count=20&dir=asc>),
whereas I haven't had such a problem with the (much more empty) generic
toner I was using before.

So my theory is that the pitting *helped* by allowing trapped air to escape
thru the paper and got me better adhesion. I usually splash a bit of nail
polish on my bigger pour areas to alleviate the pitting.

PG

On Tue, Nov 15, 2011 at 4:59 PM, DJ Delorie <dj@...> wrote:

> **
>
>
>
> DaveC <davec2468@...> writes:
> > I wonder if those temps are absolute or if they depend of you're
> > using an iron or a laminator.
>
> Each toner "recipe" has a specific temperature at which it is plastic
> (and sticky) but not liquid. Ideally, you want to heat it to exactly
> that temperature, so it sticks to the copper but doesn't deform.
> However, that's harder than you'd think. So, each one of us needs to
> come up with a pattern of device + temperature + #passes that results in
> the toner hitting that "plastic" state. Lower temperature but more
> passes? Should work. Higher temperature, fewer passes? Should work.
>
>
> > But after etch, it looks like there were some pinholes in the toner:
>
> I always get this, I suspect we just can't tell modern printers to put
> down enough toner to make a really thick mask.
>
>  
>


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