Preserving signal integrity is without doubt one of the biggest difficulties in PCB style, Specifically with high-speed signals. In the 6-layer PCB, signal integrity may be preserved by: 2. OSP boards have to not be baked, as baking will induce the OSP film to crack and shed its protective capacity. https://keeganszfhm.bloggerchest.com/30895278/the-greatest-guide-to-20-layer-ic-industrial-control-test-substrate