don't forget if it is ground plane, your allow the solder coverage  
50% (or 70%), you need take out one or two vias to ensure you have  
sufficient connection to avoid local heat... (make sure the solder  
coverage of 50% is not one sided under the components to avoid  
overheating upon components operation - not just open/short test...  
if it is split ground for MCM, you need to make sure EACH ground got  
sufficient via/solder coverage at assembly level, not just PCB)...IMHO.
jk
On Jan 20, 2018, at 3:47 PM, Wayne Thayer wrote:

> You simply take the length the via is carrying the current and  
> divide that
> by the circumference (pi * d). For power designs, you should insist  
> on a
> full ounce on the via wall. One ounce copper film is 0.7 milliohms/ 
> square,
> so you just take the calc above and multiply by 0.7 and now you  
> have the
> resistance of a single via. Multiply that by the current to get  
> voltage
> drop. If the voltage drop is too high, the via will get warm and  
> someone
> will complain about your lousy power distribution system. So add  
> vias, or
> make bigger vias until you're sure that won't happen!
>
> Wayne Thayer
>
> On Fri, Jan 19, 2018 at 11:00 AM, Nutting, Phil  
> <[log in to unmask]>
> wrote:
>
>> Many of our designs use 1, 2 or 4 ounce copper for our heavy current
>> applications.  Vias and plated holes might have ½ or 1 ounce of  
>> copper
>> plated in.  So, is there a design guide for the number and size of  
>> holes to
>> effectively transfer the current from one side of the board to the  
>> other
>> side of the board?
>>
>> Phil Nutting  |  HVP Senior Development Engineer   |  Excelitas
>> Technologies Corp
>>
>> Lab: +1 978.224.4332   |  Office: +1 978.224.4152
>> 35 Congress St, Salem, MA  01970 USA
>> [log in to unmask]<mailto:[log in to unmask]>
>> www.excelitas.com<http://www.excelitas.com/>
>>
>>
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