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I have thought about this a few times in the past.  It may be more environmentally friendly than using copper or other metals for a circuit board. I have some small scraps of wood that I think would make a good circuit board for a project.  Some Hams (amateur radio operators) have used the Manhattan style of building projects.  This method uses regular circuit board with dots cut out of copper as the pads.  Instead I thought that I could use small brass screws as the pads on the block of wood.  I have used brass escutcheon pins, which are small nails as terminals on a block of wood and they work OK.  I also thought about using a a dremel mototool with a small router bit and just cutting holes in the wood for the parts with grooves between the parts for the leads.  This has to be done manually unless some kind of an X-Y milling machine is used.  I see no problem with that because wood is relatively inexpensive.  But the wood is not a very good insulator and could cause problems with high impedance circuits.  In that case it would be better to use plastic or Nylon, which is still not expensive.  Also if the quantity of circuit boards is large enough, then a molding machine could be used to make the plastic parts.  The circuit board could then be integrated into the project case.

I have also thought about how to connect the leads.  If the circuit board is insulated then a small hole could be added where the leads come together and then the leads can be connected with a conductive material such as a metal plated plastic pin or a carbon filled conductive rubber plug.  Two or more leads would be stuck into a small hole and the rubber plug would connect them together.  This is the opposite of using a metal eyelet with an insulated rubber plug but it accomplishes the same thing.

Another thing I like about this is that some parts such as transistors have a case that is made to be placed by automated assemblers.  The hole for the transistor could be shaped so that the transistor can only be inserted one way.  This would be very helpful for a kit to be assembled by the user.  Obviously the parts would not be surface mount, they would have to be thru hole parts.

Another way to do this is to use a 3D printer. The circuit would be built up instead of cut out of plastic. This would be good for the prototypes and then later changed to a cheaper form of construction, such as molding.

I’ve read that people scan in a part with a 3D scanner and then use software such as SolidWorks to modify the design if needed. This will allow me to build a prototype out of wood and after it’s correct then scan it in and have it made out of plastic using a 3D printer for a prototype.

At Santa Ana College where I used to work they offer CAD/CAM classes where one can learn how to design a part and then actually make it on the milling machine. With a regular copper circuit board, I could put a small router bit into the milling machine and actually cut out the copper on the board leaving the traces and holes for the parts. But it would be easier just to print the circuit out and etch it, or send the design to a circuit board manufacturing company.

All this doesn’t sound very efficient but then when you build a prototype you’re not really too concerned about the cost if there are going to be thousands more made later. I’ve thought about the kinds of circuits that would work well with this assembly method and the best choice might be simple small circuits that would be put into a kit, that do not have to be very small. One good thing is that this assembly method eliminates soldering. Of course, it might be possible to program an automated machine to do the assembly. Some of the things I’ve talked about have or may have been used by kit makers. I would welcome a comment about any pro’s and con’s about this.