Start with Coombs' Printed Circuit Handbook and the IPC standards. Also call your connector suppliers and talk to their FAEs. Also if you're using a large boa

Start with Coombs' Printed Circuit Handbook and the IPC standards. Also call your connector suppliers and talk to their FAEs. Also if you're using a large board fabricator they may have FAEs. The rules-of-thumb you've picked up sound awfully industry-specific. If you're thinking about this stuff, you'd probably find a good undergraduate materials science textbook fascinating.