Ken, 

Here is a link to an paper by Doug Brooks of UltraCad that may be of
help:

http://www.ultracad.com/articles/viacurrents.pdf

My regards,
Steve Smith


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kenneth Wood
Sent: Friday, July 24, 2009 8:56 AM
To: [log in to unmask]
Subject: Re: [TN] uVia Capacity

Yeah, I was hoping that the IPC had a formula by now that would be close
but
it doesn't look like it.
There are quite a bit of variables in micro vias that are not present in
a
standard via. 
I may end up ordering a board full of vias and testing them.
Thanks
Ken

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Rex Waygood
Sent: Friday, July 24, 2009 3:46 AM
To: [log in to unmask]
Subject: Re: [TN] uVia Capacity

Ummm. Not being an expert here but having seen sections of microvias I
would be inclined to put in a large safety factor.
Regards
Rex  

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dwight Mattix
Sent: 23 July 2009 19:53
To: [log in to unmask]
Subject: Re: [TN] uVia Capacity

IPC-2221 figure 6-4 "Conductor thickness and width for internal and
external layers."

Use the magic of pi to figure the equivalent flat trace width, check vs
the charts and voila!  If it's a solid copper filled uVia then look for
round wire equivalent.

At 10:32 AM 7/23/2009, Kenneth Wood wrote:
>Hi,
>
>Does the IPC, or anyone, have current capacity numbers for micro vias?
>
>Thanks
>
>Ken

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