That is correct, Werner.
Some sort of two-tier rating system needs to be adapted by the industry,
one MSL for a lead-free process, and another for SnPb process. This
should be part of J-STD-020.
J-STD-033 needs to define the handling based on the intended process.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier
Sent: Monday, June 20, 2005 10:46 PM
To: [log in to unmask]
Subject: [TN] Moisture sensitivity levels...

Hi Steve,
Even that is not the whole story. In J-STD-020 & 033, MSL levels are
established. however, no differentiation is made as to the difference in
the soldering temperatures for SnPb-soldering and LF-soldering. The MSLs
mean different things depending on the soldering temperature, since at
higher temperatures the same moisture level will result in higher vapor
pressures and thus more destructive forces. Thus, some sort of de-rating
system, i.e., MSLx(SnPb)=MSL[x+2](LF); thus, e.g., MSL3(SnPb)=MSL5(LF),
needs to be developed.

Werner

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