Talk to the solder paste manufacturers technical service engineers, they
can typically provide information about shelf life during refrigeration and
room temperature.  They will also have information about stencil life,
sometimes even at high humidity and slightly elevated temperature (30C)

Karen Tellefsen - Electrical Testing
[log in to unmask]
908-791-3069



                                                                            
                                                                            
                                                                            
   [TN] Solderpaste Storage and Use                                         
                                                                            
                                                                            
   Amol Kane                                                                
              to:                                                           
                TechNet                                                     
                                                        06/20/2011 02:28 PM 
                                                                            
                                                                            
                                                                            
                                                                            
   Sent by:                                                                 
          TechNet <[log in to unmask]>                                         
   Please respond to TechNet E-Mail Forum, Amol Kane                        
                                                                            
                                                                            
                                                                            






I am re-writing our solderpaste use and storage procedures for water
soluble and no clean fluxes (SnPb and Lead-free) to say, in essence the
following:

"To be stored per the manufacturer's recommendations (usually upto 10C),
must be at room temperature before it is dispensed on the stencil (at least
an hour thawing is required). Maximum use period to be 8 hours.
Re-refrigeration and use beyond 8 hours not permitted"

The pushback is to the prohibition of re-refrigeration (for use the next
day) after it is thawed and use beyond 8 hours requirement. These
requirements are due to concerns with moisture absorption by the
solderpaste once thawed (affecting slump) and flux activity (due to ageing)

What criteria are all the learned folks on technet using for solderpaste
management? Is there any literature available that looks at solderpaste use
limits on time and temperature?

A logical solution would be to do a DOE to look at these parameters, but I
am being asked to come up with something ASAP:).   love how these things
work!




Thanks in advance


Amol


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