I'm a bit confused on how to calculate the current capability of a SMT
pad.  We have a 2220 size chip bead that has 8A flowing through it.
Our pad geometry is built per IPC specifications but the manufacturers
datasheet calls out for a PAD twice the width (part max is 10A). 
So the question came up, with our current pad geometry (to IPC), what is
the current capability?  I understand that it is based on the 
cross sectional area of the copper.  The current density of copper is
4.02 A/sq-mm.  For a 1 oz copper trace the area is 
1.4 mils x trace width.  But what do I use for a PAD?  I have an width,
length, and thickness.  For instance I have a SMT pad that 
is 1.5mm X 6mm using 1 oz copper with multiple traces coming off of the
pad.  What is the current carring capability of that pad?   
Or am I thinking about this wrong?  Thank you.
 
Best Regards,
 
Michael Forrester
Sr. Product Engineer
 
Siemens Healthcare Diagnostics
101 Silvermine Rd.
Brookfield, CT  06804
PH: (203) 740-6452
 

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