SOLDER BALLS / SELECTIVE SOLDER

Higher temperatures are the primary reason that there are more solder balls with selective soldering than in wave soldering. Possible causes are:
* Solder mask type is the most important factor ... Solder resists becomes stickier at higher temperatures.
* One flux may be more prone to produce solder balls than another.
* Too much flux
* N2 adjustment is too high
* Preheat is too low

Here is a link to a recent thread on this topic here on SMTnet http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=66094

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