ahhhhhh, I'm feeling BETTER...

But how did you know that? Where did that data come from?
and how can I adjust it for a 20 mil width 20 mil length tie bar?

thank you!
Jack

On Wed, Mar 16, 2016 at 4:56 PM, Hill, Robert J <[log in to unmask]>
wrote:

> Tie bars are not usually the limiting factor.  Because of the short length
> they heat sink to the surrounding copper reducing their temperature.  In 2
> oz. copper a 10 mil 150 mil long tie bar is good for 3.15 amps, so you
> would need 4 tie bars for 10 amps.  This about 3 times what a long trace
> could handle.  This is based on the tie bar rising about 10 degrees C over
> the adjacent area.
>
> Robert Hill
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Jack Olson
> Sent: Wednesday, March 16, 2016 11:33 AM
> To: [log in to unmask]
> Subject: EXTERNAL: [TN] Hole Fill and Thermal Relief
>
> Maybe I should know better than to ask two questions in the same email,
> but they're related...
> I got into a discussion about the hole fill requirement for some large
> through-hole power devices and connectors. The supplier is worried about
> using a "percentage" hole fill measurement, because he says that even if
> the hole is 75% full (or whatever percentage we want to use) the hole wall
> will not be WETTED 75%. He maintains that the cold solder can extend up
> farther than the actual portion that makes a good joint. So he is looking
> at the TOP PAD WETTING for verification of a good solder joint, even though
> we don't require it.
>
> Q1) It seems like an inspection procedure looking for WETTING instead of
> HOLE FILL is not what is intended in IPC, but does he have a point? The
> hole fill problem is with Selective Soldering, not Reflow
>
> Q2) Wanting to provide bare board designs using good DFM practices, I
> would be willing to reduce my thermal spoke widths so the solder will flow
> better, but I can't find a calculation that would tell me what I need for
> something like 10A. There is nothing about this in the IPC-2152 Current
> Carrying standard. Is there a rough guideline I can use for current through
> planes using thermal relief??
>
> thanks
> Jack
>
>
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