Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

----- Original Message -----
From: "derekhawkins" <derekhawkins@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, November 16, 2005 7:49 PM
Subject: [Homebrew_PCBs] Re: A $500.00 "UV" non-trivial exposure box.....


> >The same would seem to apply to photo resist
>
> Not quite. You print the artwork only once (both sides for double
> sided). You then align both sides and permanently fix the alignment

Yes, Russell made the same point. Almost compelling. We could have gotten
here sooner without the posturing, no?

>>All that aside, the quality of the artwork would seem to be
>>paramount. The laserjet prints very clean, very crisp edges. Filled
>>areas are very dense black and consistent.
>
> Quite the opposite on transparencies. Take a look here;
>
> http://www.pbase.com/eldata/lasvsink
>
> While the inkjet edges are more jagged this is actually a non-issue
> since with the right exposure time those edges disappear. What you
> cannot see in the laser print is the pin holes and dropouts that
> will lead to holes and pits in the tracks. The same holes and pits
> that are often there after etching a TT board. You just need greater
> magnification in order to see them. The transfer of toner from paper
> to copper is far from perfect.

The Pulsar paper releases very cleanly. You'll see the dropouts as effluent
in the soak water. That hasn't happened since fugging up the first board
with raised burrs.

>
>>The Epson 1280 (28800 dpi) only manages a fuzzy edge,not crisp at
>>all, and not nearly as dense.
>
> Fuzzy edge was discussed above but density of an inkjet print on
> transparencies should always be several times greater than that of a
> laserjet. You need to use Epson inkjet transparencies.

It won't be even close. Pigment inks, maybe possibly, but not dyes. If you
also have a laserjet, hold up one of each to a bright light.

>
>>If both are available, I expect you would choose the laserjet.
>
> No, just the opposite. Furthermore, just about every laser printer I
> have used has issues when it comes to CNC drilling. And this is not
> something scaling can correct since it's inconsistent.

That will be surprising, and I'll check it later as well. Seems
counter-intuitive that the rickety mechanism on plebian inkjets can hold
tighter tolerance than non-moving parts. (I'm assuming a lot, since I don't
really know what the laserjet really does in its dark innards.)

>
>>And if you're printing on the laserjet anyway, why not go straight
>>to the board for the onesie-twosie?
>
> When you magnify the tracks of your TT boards, do you really like
> what you see?

They're icky, likely from over etching. Still working on that part. I'll
hook up the scanner later and see what we see at 4800 dpi.