carampsguru

Hello, Actually the short and accurate answer to the question is:The PCB copper traces can handle higher current densities,because their surface area is bigger and can dissipate the heat better(with lower temperature rise).This of course ,depends on the airflow and will be probably different for top and bottom layers.In multilayer PCBs the internal layers can't cool off as good and lower current density is allowed. For example: 50mm long and 30mm wide 2oz PCB copper trace can handle 83A of current with 80C temperature rise.For internal trace is half of that - 41.5A Also the fusing current(when it opens) will be 266A with time for melting of 5.47s