"Bart Bervoets" wrote in message ...
Is there any way to "look through" a circuit board which
has traces inside (multilayer)?
I tried making the layers visible with a lighttable, but
the board is simply not thick enough to let enough
light pass.
Any other way to look inside a board or other object?
I thought of infrared light, but no idea how to make that
visible on the other side.

If you understand what the circuit is doing, and there are only
4 layers and the 2 inner layers are power planes, you can do a pretty
good job by eye.

X-rays can do the job quite well. You do have to disentangle all the
layers, and for 5 layers it gets complicated with overlapping
internal vias.

There also are automated "bed of needles" test machines that will tell
you which pads are connected to which other pads. This isn't the same
as telling you all the details of internal routing (which can be very
important at hundreds of MHz). This is useful for unpopulated boards,
but I'd question its utility for boards with BGA parts already soldered
on.

As well, can electric current in a board made visible ?

Magna-See (for directly visible readout). Current probes
and/or Hall-effect probes for quantitative measurements.

Tim.