10V/mil - so 60mil.
60 mil is ~1.5mm, if I am not mistaken.
So you have a safety factor of ~2.5, based on the 0.5mm rating for 500V.
Not the 10 fold increase that Inge recommended, but depending on your
comfort level, may be OK.

If this is on the primary side for a voltage entering a product, there
may be CSA/UL type requirements to meet that may be different than the
absolute minimums mentioned in the IPC document.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Phil Nutting
Sent: October 15, 2007 8:29 AM
To: [log in to unmask]
Subject: [TN] inner layer spacing for voltage

Good morning,

One of our engineers posed this question;

" I have an inner ground plane in an area with high voltage (to 600 V).
My question is this: What is the recommended spacing between the
plated-though hole with this voltage and the internal ground plane
relief outline? I will go with 10 V/mil as a default, but I am hoping
the safe limit might be a bit higher than this."

Can you point me to an IPC spec for this?  I was thinking it might be in
2222.

Thanks in advance.

Phil

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