Hi Eli,
BOTH.
You need to make sure that your cooling rate is no faster than 1.5C/second 
[as measured on the assembly] to avoid warpage and pad cratering.

Werner
Future workshops:
Pb-Free Soldering Processes: Survival, Quality, Reliability, September 3, 
Stockholm, Sweden
Reliability Issues with Lead-Free Soldering Processes, September 22, 
Schaumburg
Failure Mode and Root Cause Analyses Reliability (Fatigue, Brittle Fracture, 
ENIG), September 22, Schaumburg
Solder Joint Reliability: Parts 1 & 4, Oct. 9, Moscow, Russia
Solder Joint Reliability: Part 4, Oct. 17, Timisoara, Rumania
Solder Joint Reliability: Parts 1 & 4, Oct. 22, Tallinn, Estonia



**************
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(http://information.travel.aol.com/deals?ncid=aoltrv00050000000047)

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