Here's some good reference docs on moisture sensitive parts

IPC-SM 786A  "Procedures for Characterizing and Handling of Moisture
          /Reflow Sensitive ICs"

EIA JEDEC  JESD22-A112-A (Test method A112-A)
     " Moisture Induced Stress Sensitivity for
     Plastic Surface Mount Devices"

National Semi APP Note 450 "SO Package Surface Mounting
     Methods-Parameters and their Effect on Product
     Reliability"

I think the guidelines these days are 28 pins and up PQFPs,
TSOPs , etc....

     Best
     John

John Brewer
Component Engineering Supervisor
Square D Company
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