The perils of long, thin traces?

[juz_ad]

Kind of a general question (if there is a general answer)…

What are some of the main problems associated with long, thin traces on a PCB design?

I'm asking because I recently had to troubleshoot a circuit where the problem seems to be down to 3x traces at approx. 6cm long and 5 mil thick - which was about twice the distance and half the thickness of any of the other traces on the board.

Shorting them with wire solved all the problems - so it seems like a layout problem.

Can anyone offer any insight into that?

Thanks.

 

[andre_luis]

If the current layout clearance support a track thickening, I also would come to the same conclusion that most likely the thickness could be the cause of the problem, although we should not discard interference issues to certain routed paths.

 

[ads-ee]

6cm and 5mil isn't all that long, so unless there was a manufacturing issue with the PCB (like over etching) I wouldn't think that would be the source of the problem.

There are quite a few things that could be potential problems and a lot of them are dependent on the board design engineer and the quality of the board designer who did the job.

 

[chris.mourad]

Hi

Long and thin PCB traces are usually to avoid, because they tend to increase drastically track resistance.
Long wires on a PCB can also be considered as antennas, and will easily catch a lot of interferences/rubbish.
Moreover, long wires will have a bigger parasitic inductance, creating non-idealities on the dynamic signals.

Now long tracks can be used on a PCB, as long as it is for static logic signals: No current flowing into those tracks.

 

[andre_luis]

A track with 6cm/5mils/0.5Oz yelds less than 0,5 Ohms of resistace, which don´t make any difference for digital circuits and also even for analog circuits.

 

[marce]

Do loads of boards with these sort of track sizes, also look at PC motherboards, they are covered in them.... a lot will be 4 mil wide traces for the impedance figures..... DDR interfaces, gigabit Ethernet, PCIe etc.

What is a static logic signal???????

What specifically was the problem.....