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April 1997

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Re: Reflowing gold plated board
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52:50 1997
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     Hi TechNet!
     
     Try conducting a thermal profile of your board with a thermocouple 
     attached to the QFP pads and a thermocouple attached to the QFP leads 
     - you may have uneven heating with the board internal layers thieving 
     enough heat that the leads become the preferred direction for solder 
     flow. The thermal profile data should help point you in the right 
     direction. Good Luck.
     
     
     Dave Hillman
     Rockwell Collins
     [log in to unmask]


______________________________ Reply Separator _________________________________
Subject: Reflowing gold plated board
Author:  [log in to unmask] at ccmgw1
Date:    4/12/97 12:54 PM


I am processing a board with pads that are gold plated. I am using OA 
paste 63/37. All the pads are flowing good except for a  QFP. Shorts are 
appearing after reflow. The screen apertures are the same dims that i 
normally use for HASL boards. The profile is set to the low side 
temperature wise ( i tried a higher temp and it was just as bad). It 
appears that the solder is not flowing evenly between the pads and the 
leads. It is flowing more so to the leads than the pads.  I also tried 
applying a liquid OA flux to the leads of the QFP prior to reflow and that 
made the shorts even worse. Anyone have any suggestions. Thanx
ahead.
     
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