This question is right up my alley. I used to work for Lucent Technologies. I built many Central Offices, and upgraded quite a few more. When attaching copper to copper, or any other metal for that matter, we used to use a product called NO-OX-ID. It is slightly toxic so if you do get it, don't ingest it...etc. But it is the preferred metal prep in a CO environment.

I used it when I built my eggbeaters.

John KB2HSH