i train those two together,starting with back,i do 2 exercises for thickness,seated row and t-bar row and 2 exercises for width, wide unilateral pull down and front pull down,3sets each,total for back 12 sets.
for triceps,i do those 3 exercises,press down,hammer extension and over head extension,3sets each,total 9sets for triceps,i have a wide back and my arms are 20 inches cold,so what i do must have been working for me.
this is an advanced program.