d) As lead-based solders have been phased out, lead free solders such as Sn-Cu have appeared. Figure 5 shows the phase diagram for the Sn-Cu system. What composition of Sn-Cu would be most useful as solder materials?

e) What are the phases present, the composition of each phase, and the weight fraction of each phase for a Sn-Cu mixture containing 50 wt% Cu at 100 C?

1200+ 1000- Liquid 800- Y B (Cu) T (C) 600- CU 10 Sn3 400- Cu 4475641 200- CuaSn5| CuaSno Cuz Sn (Sn) 0 0 Sn 10 20 30 40 50 60 70 80 90 100 Cu Mass % Cu