[SI-LIST] PCB Impedance Failure

Hello all,

I a have been watching this list for some time.  I am not a SI
engineer, but I am the divisions PCB expert.

A board we just had fabricated failed the impedance test coupon.  59
ohm vs 50+/- 10%.  They could not measure the diffferential pairs
because of an error on the coupon, but calculated 86 ohm impedance vs
100 +/- 10%

We have no SI simulation tools in house, something I am working to fix,
but I have been asked to characterize the risk in using these boards.

My answer:  I don't know... I have no idea what our noise margins are. 
I sound like an idiot, but at least an honest one.

Any ideas, comments, etc?

Clayton Wrobel
Electrical Engineer, IPC CID


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