390 Chapter 13
13.1.8 Miscellaneous Points
● On double-sided PCBs, copper areas should be solid on the component side for
minimum resistance and maximum screening, but will need to be cross-hatched
on the solder side to prevent distortion if the PCB is fl ow soldered. A common
standard is 10 thou wide noncopper areas, that is, mostly copper with small
square holes; this is determined in the CAD package. If in doubt, consult those
doing the fl ow soldering.
● Do not bury component pads in large areas of copper, as this causes soldering
diffi culties.
● There is often a choice between running two tracks into a pad or taking off a
tee so that only one track reaches it. The former is better because it holds the
pad more fi rmly to the board if desoldering is necessary. This is particularly
important for components such as transistors that are relatively likely to be
replaced; for single-sided PCBs it is absolutely vital.
● If two parallel tracks are likely to cross talk, then it is benefi cial to run a grounded
screening track between them. However, the improvement is likely to be
disappointing, as electrostatic lines of force will curve over the top of the screen track.
● Jumper options must always be clearly labeled. Assume that everyone loses the
manual the moment they get it.
● Label pots and switches with their function on the screen-print layer, as this is
a great help when testing. If possible, also label circuit blocks, for example, DC
offset detect. The labels must be bigger than component ident text to be clearly
readable.13.2 Amplifi er Grounding .............................................................................................
The grounding system of an amplifi er must fulfi l several requirements, among which are:
● The defi nition of a starpoint as the reference for all signal voltages.
● In a stereo amplifi er, grounds must be suitably segregated for good cross talk
performance. A few inches of wire as a shared ground to the output terminals will
probably dominate the cross talk behavior.