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?
     
     
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