PCB manufacturing makes raw printed circuit boards. Later some other process (hand-assembly or pick-and-place assembly) solders the various parts to the board. The result is a completed printed circuit board assembly, such as the Gen7 Board-ARM v2.0 and various extension boards.
Some people find trying to get a RepRap to make “its own PCBs” an interesting challenge. In particular, as of 2015 all known self-fabrication processes require relatively wide traces and relatively wide spaces between the traces – far too wide for most modern CPUs with their tightly-packed pins. But with careful tuning, it is possible for a RepRap-based desktop CNC mill to make spaces and traces narrow enough to fit a few modern CPUs with relatively widely-spaced pins.
Traumflug has successfully milled RepRap PCBs on a Wolfstrap.
Further reading
Visolate: software for generating G-code for manufacturing printed circuit boards (PCBs) by isolation milling. http://github.com/Traumflug/Visolate
Poul-Henning Kamp. “Height probing for PCB isolation routing with Eagle/pcb-gcode”. http://phk.freebsd.dk/CncPcb/
“PCB designing and isolation milling using only free Software”. http://www.instructables.com/id/PCB-designing-and-isolationmilling-only-using-free/
“A Step-By-Step Guide to Isolation Milling A PCB”. http://www.ofitselfso.com/LineGrinder/LineGrinderHelp/LineGrinderHelp_IsolationMillingStepByStep.html
List of PCB manufacturers. OSH Park is paticularly hobbyist friendly. http://www.opencircuits.com/PCB_Manufacturers
Bernhard Kubicek.
“notes on PCB milling on repraps.”
http://bernhardkubicek.soup.io/post/244415439/notes-on-PCB-milling-on-repraps
(FIXME: has this “trapezoidal lasercutable pcb mill” or any other PCB mill been released as open hardware?)
“First PCB milling success” http://people.openmoko.org/werner/cnc/pcb-1st/ implies that adding oil helps PCB milling.
Long discussion about milling PCBs on open hardware: http://www.contraptor.org/forum/t-192541#post-755646
Fabio is an Arduino compatible microcontroller board, designed to be milled using a 1/64th inch end mill out of a single layer PCB. http://makeyourbot.wikidot.com/fabio-1-1