I would not recommend HASL, choose one of the flat alternative finishes.
Remember type 3 paste is about 50% solder by volume. A 100 um of variation
in the HASL is more than the total applied volume of solder in the paste
deposit. This type package will not work well with 100% variation in solder
volume in the solder connection.
You might be successful with 25 um of variation in the HASL finish.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of James Verrette
Sent: Tuesday, August 19, 2008 1:22 PM
To: [log in to unmask]
Subject: [TN] Maximum HASL thickness for SMT of QFN
What is the maximum SnPb HASL thickness/uniformity that can be tolerated in
the SMT assembly of a .5mm pitch QFN package? Is there anyone else out
there putting .5mm pitch parts on HASL finished boards that is willing to
share their experiences?
Jim Verrette
Senior Electrical Engineer
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