To add my input to the argument:

Keeping the non-functional lands in the board does decrease the Z-axis
expansion at soldering temperatures by about 10-30%, mainly, because above
the Tg the Z-Axis expansion is great for the resin systems, but copper
remains the same.  As mentioned, the difference in expansion will make a
difference on whether you have lifted lands or not after HASL or soldering, I
have seen this demonstrated several times .  Of course, the boards with the
thinner dielectric benefit the most.  The hole-wall pullaway, if this is a
concern, is also decreased and many people subjected to the 40% rule will now
pass this requirement if non funtional lands are retained .  The fabricators,
of course, want them removed as they increase the probability of shorts or
other etching defects and removing them will increase yield.   

Phil Hinton
[log in to unmask]  

***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To unsubscribe from this list at any time, send a message to:           *
* [log in to unmask] with <subject: unsubscribe> and no text.        *
***************************************************************************