Nicholas LAI wrote:
>
> Hello all
>
> There is some item need help ..
>
> I have inner layer clearance..... What is clearance means...?
> What it related to.......?What is clearance function?
> Can anyone put some example to me.... on the usage of clearance?

I can from a compliance point of view.  "Clearance"
is used to specify the straight line distance between
two conductors. Inner layer clearance could mean the
straight line distance between two conductors between
inner layers say from a layer 6 to a layer 7.

It's dependent upon upon the voltages involved, the
environment the thing is going to be in, the type
of material used.

All of the member countries of the IEC agreed to
use certain international standards as templates
for their own countries.  That way we can all
supposedly speak the same language.

In this particular case, all the IEC members agreed
on something called IEC-950.  From this one standard,
member countries write their own version by editing
for their own national deviations. The United States
wrote one from it called UL-1950.  The European
Community wrote one from it called EN-60950.

It's a product safety standard.  Testing a product
to UL-1950 for here in the US will allow labelling
with the UL label if you have UL do the testing,
or the ETL label if you allow ETL to do the labeling.

Maybe that's what you need to know.

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