I'm also hooked on sports cars and circuit bikes of the old fashioned variety, which use the concept I'm about to unveil, and as part of my bid to save the planet I came up with this weight saving measure. If all our stompboxes all over the world did this we could conservatively save at least one whole barrel of oil due to the savings in energy by having lightweight circuit boards. The extra fibreglass shavings, though, in the air is another problem and next week I'll do something about using this chaf when laying up new boards.
(http://i4.photobucket.com/albums/y115/quickkiwi/effects/IMGP0912.jpg)
The question that hits me first is whether the energy used to drill the holes is less or more than you save by not carrying around the weight removed from the PCB.
One thing that's easier is to use thinner PCB stock. It comes in lots of thicknesses less than the "standard" 0.062" thick stuff. You can get 0.031" and 0.015" I know. Possibly much thinner if you get "pre-preg" for mulitlayer boards
Check out NASA soldering specs. Uses a very minimal amount of solder.
You may not think that would save weight, but when you consider something like a space shuttle or space probe with millions (or billions) of solder joints, it save loads of weight.
And then if we were to bow micro bubbles of oxygen into the resin during building of the boards we could save even more energy.
Incidentally, I'm in a country where most of our electricity generation is hydro so using that to save oil is a viable issue. But I do agree R.G. that alot of supposed savings that people think are neat and popular have issues around them that just re-distribute energy use and may even add to it.
Using surface mount components could shrink the PCB to perhaps 1/2 or 1/4 the size, how's that for a weight saving?
Dave