Not quite. I^2·t will tell you the let through current of
the copper trace, but will not necessarily tell you if the
construction will be compliant. The compliance criteria for
this test include:
* no damage to the trace (no lifting, probably no
discoloration)
* no damage to the PWB (no delamination, burning; I don't
know if this includes burning off of solder mask)
* before and after earthing impedance must comply with the
0.1 Ohm maximum impedance
* no change in earthing impedance greater than 10% of the
before and after earthing impedance results
There is also the much more variable solder in the earthing
path. While manufacturing techniques have come a long way
in terms of consistency, the amount of solder in a joint and
the quality of the joint itself can play a significant role.
It should be expected that a lower melting point solder will
perform less well than a higher melting point solder.
Appropriate process controls will have a positive effect.
These are some of the reasons some form of safety agency
factory auditing of this type of construction is normal.
Regards,
Peter L. Tarver, PE
Product Safety Manager
Sanmina-SCI Homologation Services
San Jose, CA
[email protected]
> -----Original Message-----
> From: Chris Maxwell
> Sent: Tuesday, February 04, 2003 5:32 AM
>
>
> Exactly!
>
> Chris Maxwell
>
>
> > -----Original Message-----
> > From: drcuthbert [SMTP:[email protected]]
> > Sent: Monday, February 03, 2003 7:50 PM
> >
> > What is needed is the I squared t rating of the
> breaker. Then the (I^2)(t)
> > rating of the PCB. Then you know if the PCB can
> take it.
> >
> > Dave Cuthbert
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