Signal Orientation
Orienting high-speed traces at a non-orthogonal angle relative to the glass weave axes reduces periodic impedance fluctuations. Implementing angle routing helps to average out the dielectric constant variations encountered as a signal passes over glass bundles and resin gaps. This technique typically involves rotating the entire design or specific signal paths by 10 to 45 degrees.
Signal integrity improves as resonance effects are avoided.
Layout Implementation
Modern computer-aided design tools facilitate the placement of traces at arbitrary angles across the board surface. While angle routing consumes more board real estate than traditional 0-90 degree layouts, it significantly improves signal timing. Designers must verify that the manufacturing partner can handle the increased file complexity.
Errors in data conversion can lead to unintentional copper slivers or clearance violations.
Yield
Registration between layers becomes more complex when the primary axes of the traces do not align with the material grain. Although angle routing offers electrical benefits, it can lead to higher scrap rates if the fabricator lacks advanced optical alignment systems. Shrinkage factors must be calculated for multiple directions rather than just the X and Y axes.
Misalignment of a few mils can ruin the impedance of a differential pair. Advanced fabrication shops use automated optical inspection to verify the geometry of these angled structures. Success relies on precise compensation for substrate expansion during lamination.
