I have had some recent discussions with fabricators about this subject.
I am told that the width of the soldermask dam should be 0.004 to 0.005 to
have enough adhesion surface to stay in place through HAL and soldering
operations. The clearance from the edge of the dam to the edge of the pad
needs to be 0.0025 to 0.003 to allow for fabrication tolerances. Therefore
the space from pad edge to pad edge needs to be 0.009; got that space and
they can make this work for you.
Our Assembly Manager wants to have these dams in place. There are a lot of
opinions about the need for these.
Barbara Burcham

-----Original Message-----
From: Yvon Hache [mailto:[log in to unmask]]
Sent: Wednesday, May 17, 2000 2:44 PM
To: [log in to unmask]
Subject: [TN] Soldermask between pads


Hello everybody out there,

We have a board where the footprint for a Plastic Quad Flat Pack 160pins
package has no soldermask between the pads.  The pads are 1,6mm x 0,33mm and
the spacing center to center is 0,5mm.  This board does not have any traces
running between these pads.  Can this cause any problem in the board
manufacturing process and in the board assembly process?  If yes, what would
be the recommendation?  How close can the soldermask be to the pads?

thanks,


Yvon Hache, P.Eng.
Tel: 506-863-2467
Email: [log in to unmask]

Concept + Inc.
Scientific Park, Suite 100
55 Crowley Farm Rd,
Moncton, NB
E1A 7R1

Tel: 506-858-4153
Fax: 506-858-4075
Web: www.concept-plus.com

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