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July 2000

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Subject:
From:
Guy Ramsey <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 19 Jul 2000 17:03:23 -0400
Content-Type:
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text/plain (59 lines)
Look in the IPC-SM-782, IPC-SM-840 and IPC-2221 / IPC-2222. It does not
sound like the Solder Mask is your problem. 10 mils wide leaves 10 mils
between lands. How thick is the stencil? What is the ratio of the paste
brick to the land area? I would put my money on a process problem, paste,
printing, then reflow profile, last solderability of pads or parts.

-----Original Message-----
From:   TechNet [mailto:[log in to unmask]] On Behalf Of Jorge A Rodriguez
Sent:   Wednesday, July 19, 2000 4:07 PM
To:     [log in to unmask]
Subject:        [TN] Solder mask clearance

Fellow technetters,
               Can someone help me to find out what's the maximum clearance
on all sides of pads for a HASL board on a 20 mil pitch QFP. We are having
bridging problems with this device and we are suspecting  of the solder
mask between the pads. Currently the PWB we are using shows 10 mils pads
followed by a clearance of 2.5 mils and then 5 mils of solder mask. Also
what is a normal thickness of the plating on a HASL board?



               Any information will be appreciated



Jorge A Rodriguez
Process Engineer
Conexant Systems Inc

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