It depends on the thickness of the overall copper (base copper + plated
copper). Ideally speaking if you are starting with 1/2oz. base copper
followed by 1.2 - 1.4mils of plated copper on the surface, the overall
copper thickness would be around 2.0mils. So using a 2.0mil thick dry
film would be ideal for optimal conformance & minimum mask thickness at
the knee of the traces. Using a 1.5mil thick dry-film, you would tend to
have air pockets between the mask & laminate surface or the mask
thickness at the knee would be very very thin or almost negligible.....
The only other thing you may want to take care is at the assembly side
during the solder-paste printing process as the volume of paste to be
printed might have to be increased to fill up the additional 0.5mil
cavity due to the increased dry-film thickness, otherwise you may end up
with insufficient solder-paste & tomb-stoning defects.....
Hope this helps.
Thanks & Best Regards,
Krishnan C
SANMINA-SCI
"It is easier to do a job right than to explain why you didn't."
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of [log in to unmask]
Sent: Friday, March 16, 2007 11:22 PM
To: [log in to unmask]
Subject: [TN] Dry Film Thickness
Board makers, are any of you still using 1.5 mil dryfilm? Seems our
supplier has run the last roll and is switching to 2.0 mil. Any issues
we should be wary of in switching?
Thanks for any input.
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