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One of fab houses suggested stackup with 2mil traces. Given that this is their stackup so they must be feeling comfortable with it and SI performance aside - are there any reliability/manufacturability issues that arise at such narrow geometry? I can think that maintaining consistent width (thus impedance) might be more challenging due to relative error being higher.

Any thoughts?

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  • \$\begingroup\$ They are confident they can build it without overetching enough to break the trace. Whether it meets your SI needs depends a lot what those needs are. \$\endgroup\$ – The Photon Nov 15 at 3:38
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If they are Sierra Ccts or "ProtoExpress", then they are a high quality, competent shop with adequate yields that always degrade if you do not have what it takes.

Track and gap is only 1 of dozens of metrics for quality & capability on fabrication.

Acid etching rate with not only sensitive to copper thickness but also temperature, fluid agitation rate, surface oxidation, density of nearby etching but also copper content dissolved in acid and more.

It used to be 10 mil track/space was std then 3/3 for advanced but now it's;

Min   Trace and Space  (aka track and gap)
-----  ------------
4 mil  Std
3 mil  Advanced 
2 mil  Micro

Sierra Ccts. was my "goto" shop when I needed highest quality boards in the fastest delivery time and they never let me down.

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