Hello everyone. I'm curious about the effect of thermal transition if we used a multi layer PCB in large copper foil. I have an experience that I have measured two corner of a BGA which mounted on the PCB I mentioned above. But I can see a large difference of melting time between each corner. About 10 to 15 seconds delayed. Could someone help me to explain the condition and give some experience or suggestions to me? Thanks DLINK corp. SMT Engineer Jason Cheng E-mail: [log in to unmask]