Depending on what you are doing with the signals, the resistance of that trace, or it's impedance may be more of an issue than breaking through flexing.
If flexing really will be an issue, it's more likely to fail at the ends of the long trace if that trace terminates squarely into a pad or similar. Usually in these locations, solder mask clearance cuts directly across the trace. This abrupt change can lead to increased stresses on the copper, from stress risers. This may be more prevalent with dry film masks vs. LPI for example.
In the above case, failure would be possible from a high number of flexing cycles (high cycle fatigue), but only if the board is subject to lots of flexing or vibration.
Failure at the termination of the trace, or solder mask actually, might be more likely than anywhere else. Tear dropping the trace would probably help.
Dan
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On 1/9/2024 9:40 AM, Robert via groups.io wrote:
Hi,
Does anyone know of any guidance as to how wide very long straight
tracks should be to avoid manufacturing difficulties or breakage due to
board flexing (or any other potential problem I haven't thought of)??? I
have to run a couple of signal tracks a distance of 500 mm and I'm
guessing that my usual 0.2 mm width would be a bad idea, but I don't
want to make them excessively wide as that would add unwanted capacitance.
Regards,
Robert
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