soldering tab wires to negative bus line(s)

System

all articles i have read online display the soldering of the tap wire(s) to the whole length of the negative bus line(s) of the solar cell.

if the neg bus line carries all current generated by the cell, doesn't this indicate the whole bus line is conductive ?
if so, when soldering the tab wires from the positive bus (the bottom of the solar cell) to the negative bus, why not only use say 1/4" over lap on the negative bus line and apply solder only to that point ?

what are the actual advantages to soldering the tab wire to the whole length of the negative bus line ?
is it adding some structural strength to the cell itself ?

it seems to me that there is a doubling of the 2 conductors - the bus line thickness which is probably quite thin, and the added thickness of the solder, and the tab wire.

please explain if possible...

mike95490

Re: soldering tab wires to negative bus line(s)

The metalization on the back of the cell, can barely carry the power from the cell, so adding the tab wire (tinned soft copper), lowers the resistance. (copper loss) When panels are in an array, and wires go to the charge controller or inverter, larger gauges have to be used there, to reduce copper loss, and turning your hard won power into heat in the wires.