Chris,

  ITRI (The Interconnect Technology Research Institute) recently published a
report that addresses your concerns. In essence they found that a PTH
without annular ring is as reliable as a pad with a large annular ring.
Samples were submitted from several PWB manufacturers and the thermal cycle
testing was performed by NIST or Crane. Any way I'm sure you can get the
report either from ITRI in Austin, Texas or from the IPC

David Arivett
Cuplex Inc.

At 01:24 PM 8/22/97 -0500, you 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
>
>