(All of which probably means that the number of PCB
layers is
irrelevant too - the critical thing is the number of solder points)
I dunno. I find single- and double-sided boards substantially easier
than three- or more-layer boards, simply because there are no
connections buried in the board and thus invisible; the only thing
making it impossible to completely trace the circuit by eye is etch
runs disappearing under components. (While this happens, it happens
seldom enough, at least in my experience, to account for the ease I
mention.)
It also might be nothing more than that being single- or double-sided
correlates positively with having low component density in the pc
boards I've tried to trace.
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