Impedance discontinuities can sneak up on you.
Watch out for layout trouble spots like:
- Trace-to-via transitions
- Component pads and connector pins
- Antenna feed junctions
Tips to minimize reflections:
• Keep trace width uniform
• Taper traces to match connector pin widths
• Use LC matching and quarter-wave transformers
• Expose solder mask over critical RF traces
Watch the full webinar on common errors in RF PCB layout here.
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Is the suggestion about solder mask opening because the solder mask is poorly controlled (at least compared to other layers)? Or is it something more?
Hi Jim,
The main reason is that applying a solder mask over RF traces alters the effective dielectric constant (Dk). This alteration affects impedance and might increase insertion loss.
If you need to apply solder mask, consider its dielectric constant in your transmission line calculations to avoid performance degradation.
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