I have used some ssop parts with traces as fine as that using blue
pnp, although only in a single area of the board, and that creates a
few stuff ups occasionally. Its not very reliable, but if there are
just a few areas, its possible. 8 in 10 should work out i found, i
usually make batches of 10.
the PNP will transfer the trace that fine, but you must be careful
with the ironing. Too little, and it wont completely transfer and will
need pen fix ups. too much and the smear will join them together.
I make the pads as short as possible, and then branch away as quickly
as possible to minimize the areas where they are very close to each
other.
The other problem i find is they can get kocked off very easily during
etching i use plastic containers and with multiple boards bumbing each
other sometimes a pad that fine gets lost, so they must be well
seperated or etched alone.
