The values ARE conservative. There is a 15% derating factor on top of the
fact that the source for that table is something of an mystery.

The minimum spacing per volt is being tightened in the IPC-D-275 revision 
document(s), although the new table needs to be approved by IPC membership.

Mike Buetow
Technical Staff


On Tue, 27 Feb 1996 [log in to unmask] wrote:

>      
>      
>      I have a customer who has asked what is the required spacing on
>      both innerlayers and outerlayers for 1500 VAC (~2100 VDC).
>      Outerlayers have dryfilm soldermask covering them.
>      I looked up IPC-D-275 and have referenced the data from table 3-1.
>      This customer feels these values are extremely conservative and
>      is curious if other designers are using that criteria rigidly?
>      
>      
>      [log in to unmask]
> 
>