Tin whiskers do not grow from lead-free solders, where did you get
that crazy idea? Tin whiskers grow from tin plating and only tin
plating.
It's easy to solder most surface-mount parts by hand; just practise a
bit.
And it's OK to use rosin-flux leaded (63/37) solder, even to solder
lead-free parts. Better in fact.
As far as I know, nothing prevents whiskers, not even coatings. Except
lead, of course.
Lead does not prevent tin whiskers any better than any other means of
pinning dislocations in tin, such as any of the alloys used as
lead-free solders. No one has ever been able to show me believable
evidence that so much as a single tin whisker has ever grown from any
currently used lead-free solder alloy, and I doubt they ever will, it
is simply not a valid reliability issue.
Complaining about problems with lead-free these days makes as much
sense as still worrying about the Y2K bug. Forget about it, the
conversion is over and done with for all but the smallest
manufacturers, and reliability of the assembled circuits has continued
to increase.
Lead is in fact not a very good means of preventing tin whiskers, due
to well know problem of poor fatigue strength of tin-lead solders.
All high-rel applications which need to withstand shock and vibration
will be converting to lead-free; not the lowest cost SAC alloy but
high performance lead-free alloys which are now being qualified (a
lengthy process) but which clearly blow the socks off tin-lead in
strength, ductility, shock resistance and fatigue life; all of the
properties important for reliability except processing temperature are
greatly improved and the processing temp for these alloys is only
slightly higher than tin-lead. See for instance:
<
http://smt.pennnet.com/display_arti...one/1/STEP-3:-Holistic-Lead-free-Reliability/>
The down sides to lead-free are slightly higher cost and far higher
complexity of specifying the optimum alloy, flux, and processing
parameters, plus a need for tighter process controls.
This is not a reasonable forum for learning about soldering or PCB
assembly in general, the issue is too complex and almost no one here
is interested in it enough to have read up on the subject. Read the
trade rags like SMT <
http://smt.pennnet.com/home.cfm> and Printed
Circuit Design and Fab <
http://www.pcdandf.com/cms/> for a decent
introduction to the subject.