Arny,

   I am curious as to how the annular ring aids in the heat transfer to the
solder joints. Are you talking about external annular ring or internal or both?

David Arivett
Cuplex

At 09:40 PM 8/24/97 -0700, you wrote:
>Chris Gardini-ECG005 wrote:
>>
>> Seeking data/reports to address questions on the risks associated with
>> Annular Ring size.  In particular, as the mis-registration of the of the
>> mechanical drill to the PTH Pad moves towards a trace leading into the pad
>> the potential for an 'open' to occur increases.  Concerns center around
>> 'thin' ring passing ET, but in field stresses cause fracture and crack
>> propagation to 'open' state.
>>
>> Thanks, Chris
>
>Hi Chris -- I agree with Werner.  The Z-axis stress is the concern which
>normally occurs, above the 125C tg, at soldering temperatures, around
>260C. A second point to consider is the solderability issue. The annular
>ring aids in the transfer of heat to the solder joint especially for
>hand soldering during assembly or field repairs.
>regards,
>Arny Andrade
>Sandia Labs/ret.
>
>