A similar question was asked - What is Copper Thieving and why use it?
And my question originates from the comments of the answer in the linked question.
I have read and understand that to help the etching process, you balance the copper so that it effectively eats away at the board at the same rate. One of the answers/comments makes a note that its for the outer layers.
Thieving is added to the outer layers in order to help a more balanced chemical process for the plating.
What about the inner layers ?
I have a 8 layer stackup where some of the internal layers routing is not as dense as others. This is a relatively large board (15" x 8" ).
My gut/understanding tells me, that I should be balancing the copper on all layers and not just the outer layers, but I would like to be sure its needed and that my understanding is correct.