DJ Delorie <
dj@...> writes:
>
> I've got some preliminary (i.e. unetched) results.
>
> See: http://www.delorie.com/pcb/inkjet/
I looked at a 3200 dpi reflective scan of an LJ4 print very closely in
Photoshop, printed on the cheap paper I normally use. The results aren't
good. Some isolated, minor pitting is evident even without adjusting the
gamma curve. There is also some faint smudging, not significant and also
ignorable.
I then adjusted the bottom of the curve until it just began to clip the
blacks, and progressively brought down the highlights. At the point the
smudging disappeared, assuming etching is similar to a photographic process,
the board would have been usable at that state. A few more pits became
visible, but the fine details were still whole and intact. (I use 8 mil/8
mil rules for most stuff, dropping down to 6/6 only around 0.4 mm pitch
devices.) Continuing to adjust down the highlights, it began looking like
the boards and traces I typically make. Pitting became significant in
places, but not objectionably so until still higher levels of "over-etch".
At extremes, the over-etch is obvious, and looks surprisingly exactly like
copper on an over processed board. Many of my problem boards are from
etching, but I already knew that.
The scanner is an Epson 3200, calibrated using Monaco EZColor. What it sees
is pretty much what's there to be seen. I could try it again as a
transparency, but I think I can extrapolate from this the effects of
over-exposure on photo-resist. The only thing missing is a relative measure
of the (visible light) transmissive density compared to a Stouffer wedge.
I'm still curious, but don't have any transparency sheets laying about. (I
use toner transfer.)
By mere coincidence, I have an HP P2015dn on order (1200 dpi). I'll check
this again Tuesday when it gets here. (Its purchase is only peripherally
related to PCBs. I've been wearing out the pavement between here and Kinkos
the past few months, where I've been sending rather large print jobs. The
printer will actually pay for itself before the year is out.)
Mike.