DJ Delorie wrote:
> Philip Pemberton <ygroups@...> writes:
>> <http://pcbwiki.philpem.me.uk/tiki-download_wiki_attachment.php?attId=1>
>
> I do not have permission to use that feature :-(
That would be because I left "View Attachments" set to "Admins Only". It's set
to "All Users" now, so anyone should be able to see that file.
> For DS boards, what I do is include targets on my artwork. I print a
> paper copy of the artwork (in the same printer, just not film
> quality), tape it down, and pre-drill the targets, usually 13 mil
> holes.
That's what I was thinking of doing -- cut the board 1" or so oversize on each
side, then Scotch-tape the artwork to the board, drill through, then flip over
and align the other side.
I do have a double-sided exp. box, so it's a bit easier. What I've been doing
is aligning the two layers on an A4-sized light box, then using lengths of
foam mounting tape (B&Q, a shade under £2 for a 1.5m roll) to hold the masks
together. This stuff happens to be just about the right thickness to hold a
PCB between two transparencies, while maintaining near perfect alignment.
Ordinary double-sided tape seems to be a bit too thin.
Like said, I align the masks, stick it along three edges (leaving one side
open), leaving a pocket. Insert the PCB blank (with the lightproof film
removed!) into the pocket, check alignment, then put it in the UV box and
switch on.
I've just finished etching and drilling my first board, and it looks like it's
worked just about perfectly. I don't usually get this much success from a
completely new (to me) process :)
As for making the transparencies, I've been using "Jetstar Premium", in my
Canon iP4600, with the following settings:
--- Main ---
- Media type: Photo Paper Pro II
- Paper source: Rear Tray
- Greyscale Printing: On
- Print Quality: Custom [Set ==>]
- Quality: 1 (Fine)
- Halftoning: Auto
- Color / Intensity: Manual [Set ==>]
- Brightness: Dark
- Intensity: 50 (maximum/Dark)
- Contrast: 50 (maximum/High)
--- Page Setup ---
- Page size: A4, portrait
- Page layout: Normal-size printing
--- Effects ---
Make sure everything on this page is UNchecked.
This works pretty well for me, with very dense black print. Only problem is
you have to remember to apply these settings every time you print with EAGLE
(it doesn't preserve print settings AT ALL -- they reset to the driver
defaults as soon as the print dialog closes). Thankfully the Canon driver
allows configuration parameters to be saved to (and loaded from) a profile, so
it's not (too) bad, but you still need to remember to reload the profile
before hitting Print...
Ink needs to be on the matt side of the film (hold it between thumb and index
finger -- one side will feel "stickier" than the other -- that's the matt
side). EAGLE prints what's on screen, so turn off all layers other than the
ones you want to print (e.g. for the top layer, turn all layers off except
Top, Pads, Vias, and Dimension). Print the top layer mirrored, and the bottom
layer non-mirrored (the option for this is in the Print dialog). Check the
"Black" and "Solid" boxes to force EAGLE to print everything in black, with no
hatching.
... and that's basically it.
> For my targets, I use four square pads, placed together in a square,
> with about 1 mil between them. Since I use negative film, this
> results in a 1 mil crosshair inside a square hole in the ink, which is
> really easy to align with those holes.
I've been using the drill holes in the pads for coarse alignment, and the "0
mil" (translation: print as thin as possible) outline on the Dimension layer
for fine alignment (if it looks thicker than "just barely visible", it's out
of line). This gets close enough for the part pitch I've been using.
--
Phil.
ygroups@...
http://www.philpem.me.uk/