ENGINEERING ANSWER
RO4350B is reinforced, so a bulk material description does not fully describe every local field path. Trace geometry, reinforcement distribution and copper treatment can all matter when tight phase or impedance consistency is required.
What to decide before release
For phase-sensitive routing, keep paired structures geometrically comparable and discuss panel orientation and material construction with the supplier. Investigate repeatability across panel positions rather than drawing conclusions from one measured line.
Checks to put in your design brief
- Document panel orientation
- Compare repeated coupons
- Keep routing and layer references consistent
Important distinction
Do not claim that one routing angle universally eliminates local dielectric variation. Validate the exact construction and frequency range.
Sources & basis
Material facts follow the cited source. Design checks are preliminary guidance, not supplier process instructions.