Fred, Michael,

  I was interested in your communique, because I too am designing motor/valve
drivers that are switching large powers where inductive impedences are a
concern. What type of reflow do you all use? Are we the only folks left who
use vapor reflow? I've heard that it is not common. I too am mildly skeptical
about the rules for traces egressing an SMD land and if this would be a sig-
nificant cause for uneven solder cooling of opposing lands. Since, during
vapor phase, there is a pre-heat 'ramp-up', the entire PCA should have a fairly
uniform temperature, no? And there is a cool-down phase as well. 
(I will query our assy people).

  One note about the SMD components on my hi-current nets; not all of the
components are necessarilly seeing hi-current. As a rule of thumb, I've 
noticed that the smaller packages (having smaller lands) on a hi-current signal
net generally are'nt seeing the hi-current anyway; such as the control side
of my switch where there are voltage dividers and maybe a suppressor diode
that will only see transient spikes when the motor fields collapse or res-
istors to testpoints on my buss voltage. So I just keep those traces smaller
anyway. Maybe this is obvious, but I thought I would just throw this out 
there. Stay active with this forum with these types of designs so I can pick
your brains. Thanks.

                                            James Patten
                                            TRW Space and Electronics Group
                                            (310) 813-8914