Good Morning TechNet!
     
     (or good evening depending on which side of the planet you're on!)
     
     The white haze you are observing could be MANY things - not all low 
     residue pastes are clear after the reflow process. Get a copy of your 
     flux technical data sheet, review it and then start asking your flux 
     vendor questions on the characteristics of the flux versus the process 
     parameters (temperatures,equipment, times, etc.) that you are using. 
     Tin oxide is not always bad, just depends where on the assembly you 
     find it (every assembly containing tin/lead solder has tin oxide!). 
     Give Doug Pauls at CSL a call ([log in to unmask]) - he can relate some 
     different scenarios that may relate to your flux chemistry and 
     process. Good Luck.
     
     Dave Hillman
     Rockwell Collins
     [log in to unmask]


______________________________ Reply Separator _________________________________
Subject: No clean paste
Author:  [log in to unmask] at ccmgw1
Date:    2/7/97 3:55 AM


Anyone,
     
I have been told that a no clean paste post curing 
will leave a white haze or residue around the well. 
And, that this haze is a TIN OXIDE.  My question 
is:  Is this ok?  Should we be concerned?  What 
chemistries could react with TnO2 causing corrosion?
     
My experience is oxide can be hazardous to the 
assembly, i.e. corrosion, tin wiskers etc.
     
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