Thanks for the quick response to my question.
based on the two replies I received so far, there is no standard requirement for the minimum clearance
between conductors, but there is a complex equation to calculate the distance. If this is correct, then
how can I expect an inspector to determine whether or not a solder balls/splashes violate minimum
electrical design clearance on the floor? Any experience in this.
Jeff Seeger wrote:
> ryu wrote:
> >
> > I saw the term in the IPC-610. I think it has something to do with the
> > design of a product for cross talk elimination. But can someone tell me
> > if there is a minimal or maximum requirement for the distance, is there
> > any number a designer needs to follow? if the answer is no, then how the
> > designer comes up with the number ? Thanks.
>
> Well I've been trying all day to get to look it up for context
> "but it's not happenin' today!".
>
> The electrically dependent clearances have to do with either
> noise (often crosstalk) or safety. What matters is the amount
> and type (i.e. switching or static) of energy and the distances
> (and insulators) around that energy.
>
> Crosstalk is a complex issue, and Groovy's correct in that
> it involves gory detail on the signals involved as in their
> emmissive (is this a word?) characteristics and their suscept-
> ability (where's my spellchecker - I'll risk flames to get
> the comment out today). There is not a simple calculation
> to get specifics (a spice/field solver problem) and it is
> complicated (or eased, actually) by the timing of events i.e.
> if the receptor is not listening at that time the aggressor
> can do whatever it needs to.
>
> Electrical safety depends heavily on the environment and
> is just as deep a calculation to arrive at "knowns" - or
> deeper since you nomally have non-uniform insulators (pwb,
> s/m, air, moisture, contaminants, etc).
>
> Both issues, however, rely on a simple fundamental principle.
> Like any energy, electric and magnetic fields dissapate
> with the rule of inverse squares. That is, the effect of
> one conductor on another decreases with the square of the
> change in distance. One unit change in distance provides
> one unit change in interference but 2 units distance make
> a 4 unit effect. So while exactitude requires too much
> math, the principle relies on very little.
>
> This reply is quite hurried (entire books exist on but one
> aspect of the many raised here) but I hope I've helped.
>
> Regards,
> --
>
> Jeff Seeger Applied CAD Knowledge Inc
> Chief Technical Officer Tyngsboro, MA 01879
> jseeger "at" appliedcad "dot" com 978 649 9800
>
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