Balancing layers in your PCB layout stack-up, which both layer surfaces and cross-sectional structure of the circuit board are reasonably symmetrical.
How to Build a Multilayer PCB Stack-up
Epec's Blog Printed Circuit Boards (7)
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Understanding PCB Thickness: A Comprehensive Guide
Balanced Copper Distribution and Weight in PCBs
noise - Four layer PCB layout suggestions - Electrical Engineering Stack Exchange
PCB Layers Explained: Everything You Need to Know
PCB Layer Stackup, PCB Stackup Design
PCB Copper Thickness: General Guidelines and Tips
Balanced and unbalanced PCB layer stack-up for controlling radiated emissions
The Importance of PCB Trace Widths in PCB Design
An Overview of Layer Stack Management in PCB Design
Determining the Number of PCB Layers
PCB Layer Stackup, PCB Stackup Design