Why should you not have aluminum feed wires for your electrical panel connecting to copper wiring?

Aluminum is softer than copper and weaker, and a poorer electrical conductor, so is not widely used iin home wiring. First, aluminum expands and contracts more than copper when it heats and cools. This can cause fasteners to loosen. More importantly, aluminum oxidizes easily and the oxide is a poor conductor. This causes overheating at the connection points (the main source of trouble). A further problem with some aluminum wire is fatigue. The wire becomes brittle and breaks if bent back and forth only a few times. Do not try to pull outlets and switches out of the wall to examine them yourself. Leave this to a qualified licensed electrician who can fix any problems that might be found.