As you probably know, even number of layers PCBs are pretty ubiquitous in the world of electronics. You will might find one in the devices that you use every day. So why?

Apparently it mainly refers to the processing cost. In general, the processing cost of odd number layers PCBs is virtually higher than the even number layers PCBs. Since the same inner layer processing cost but increasing the handling cost of outer layer.

Furthermore, the warpage of huge size odd number layer PCBs tends to over the standard that is why the processing cost of odd number layers counted as even number layers.

PS: The pros of balance stack up PCBs —Lower cost, warpage controlled, shorter lead time and quality guaranteed.