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March 1997

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Subject:
From:
Steve Quinn <[log in to unmask]>
Date:
Thu, 20 Mar 1997 12:12:09 -0600 (CST)
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The problem is definitely from the vias in the pads.  We have experienced
the same problem with very short traces between the pad and via.  We are
currently masking those parts during wave solder.

Steve Quinn



At 08:24 AM 3/20/97 -0500, you wrote:
>
>     Hello TechNet:
>     
>     We have a .062", board with a top side QFP (SMT) that is reflowing as 
>     the board crosses the wave.  Our top side preheat temps have been 
>     checked and double checked and is in the 230 degree "F" range.  Peak 
>     temps shown as the board crosses the wave are well below the 361 
>     degree "F" mark.  We have vias in the pads on some of the leads.  The 
>     QFP is plastic.  The board is approximately 3"x5" in size.  Density is 
>     maybe a little over average.
>     
>     Has anyone out there experienced the same thing with some of your 
>     products?  We are not seeing a blatant open solder situation, but 
>     suttle fractures that will eventually turn to a open situation.
>     
>     Supposedly the SMT guys profiles are ok.  They are pretty reliable.  
>     The boards are inspected after SMT reflow.
>     
>     What do you think?  Is the reflow caused by the solder coming up 
>     through the vias?  
>     
>     R. Hollandsworth
>     [log in to unmask]
>
>
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