Thanks Gary. That makes sense now.

Steve: board does not require UL or CSA approval (thank goodness!)

>>-----Original Message-----
>>From: DesignerCouncil [mailto:[log in to unmask]]On
>>Behalf Of Gary
>>Ferrari
>>Sent: Wednesday, January 18, 2006 4:29 PM
>>To: [log in to unmask]
>>Subject: Re: [DC] Electrical spacing in IPC2221 spec
>>
>>
>>Ron,
>>
>>You are not quite correct in your assumptions. First, the "A" side of
>>the table is for component lead terminations, not lands and
>>conductors.
>>The lands, as well as conductors, fall on the "B" side of the table.
>>That said, the B2 value would be higher than the A6 value since there
>>are always traces of contamination on the surface of the board which
>>will affect the isolation characteristics. Whereas the component leads
>>face air as an insulator and will not see the full effects of surface
>>contamination.
>>
>>Hope this clears it up some.
>>
>>Regards,
>>
>>  Gary Ferrari
>>Ferrari Technical Services
>>860-350-9300
>>
>>Ron O wrote:
>>
>>
>>>Can anyone help interpret the IPC2221 Electrical Conductor
>>>
>>>
>>Spacing chart
>>
>>
>>>6-1 (pg 39)?
>>>I have a pcb requirement of 500V spacing between nets. Board is FR4
>>>2layer, soldermask both sides, no conformal coating. Based
>>>
>>>
>>on the chart,
>>
>>
>>>I need a B4 spacing (0.8mm) for the soldermasked conductors
>>>
>>>
>>and an A6
>>
>>
>>>spacing (1.5mm) for the exposed pad areas (I'm assuming
>>>
>>>
>>this is pad to
>>
>>
>>>pad spacing not pad to coated trace spacing).
>>>
>>>Is my interpretation correct so far?
>>>
>>>Next question is the column B2, which applies to uncoated (no SM or
>>>conformal) and has a spacing requirement of 2.5mm. So this
>>>
>>>
>>would be bare
>>
>>
>>>trace to bare trace. Why would this spacing need to be
>>>
>>>
>>greater than bare
>>
>>
>>>pad to bare pad (the A6 rating)?
>>>
>>>
>
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