To John Lennox,
The first thing to check is the drying in your tack dry process.  The
accepted way is to
weigh a panel before ink coating, before tack-dry and then again after
drying.  The ink
should lose about 24% of its weight more or less depending on the ink
(check with Electra).
It's good to keep an electronic balance in the coating room.

The second thing to check is the temperature of your printer glass.
Water cooled printers
should keep it at 20C or lower.  The warmer the glass the more the
marking.

If you can't fix it with these two then I's liik at other inks.  There
are some excellent inks out there
that tack dry well.


> -----Original Message-----
> From: John Lennox [SMTP:[log in to unmask]]
> Sent: Tuesday, September 01, 1998 5:06 PM
> To:   [log in to unmask]
> Subject:      [TN] Soldermask Artwork Marking
> We are getting a condition known as "artwork marking" when exposing
> LPI
> soldermask. This condition exhibits itself as shiny areas where the
> artwork
> comes into contact with any high spots on the mask.
> Although it appears to be totally cosmetic, we have a few customers
> who
> refuse to purchase boards with this condition.
> We primarily use Electra EMP110 soldermask with a Teledyne DSA 2000
> spray
> coater. The panels are then tack dried in a tunnel oven for 45 minutes
> at
> 180F.
> When imaging the panels, the top side (against the mylar) seems fine
> but
> the bottom (against the glass) is marked. The degree of marking varies
> depending on the surface of the board.
> Has anyone else seen this problem, or had the need to eliminate it?
> Also, what method do you use to ensure sufficient tack dry prior
> image, if
> any?
> Any responses would be appreciated
> Thank You
> John Lennox
> Process Engineer
> EMC
>

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