You are correct, Guy.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey
Sent: Tuesday, August 19, 2008 2:49 PM
To: [log in to unmask]
Subject: Re: [TN] Maximum HASL thickness for SMT of QFN

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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