CrossRoads:
They have been used to route out copper from plated PCBs, cut out the part that etchant would normally remove.
I have not seen that appleied conductive material to bare material (such as fiberglass sheet) to make a PCB.Before PCBs, we used to have PWBs - where actual wire was put down for the traces. Like in the 80's.
Glueing double sided boards together with B-stage material in between has been the norm for quite a while.
I have seen milling machines that do this and I was looking into this intensively a while back, but in this case I am talking about 3D printers, not milling machines. It seems they would be even better than milling machines because printing, if it is possible to do at all, would allow for multilayer boards without having to align and bind layers together, along with the through, blind, and buried vias. It would be so powerful it would be revolutionary. I was just wondering if anyone knew what the state of the art on this was. Lots of people are using the milling process - I learned about it in the book 'tinyAVR Microcontroller Projects for the Evil Genius' where the authors used a mill to make all their PCBs and explain the process in an appendix.