Hello Tim,

See if there is a PCB manufacturer within resonable driving distance and
ask for scraps. That's how I got a huge stash decades ago. Single and
double sided, the good stuff (FR4). But it has to be picked up, in my
case they wouldn't have gone through the trouble of packaging and
mailing it. Basically it had to be no more effort on their part than a
walk to the dumpster would have been.

Mine weren't tinned though. Also, I am not sure if constantly touching a
pre-tinned board during experiments would be too healthy.

Regards, Joerg

http://www.analogconsultants.com