This is from the IPC News Releases dated 6/26/97:

ITRI STUDY: REQUIREMENT FOR ANNULAR RING WASTES MILLIONS

Northbrook, IL 6/26/97

The printed wiring board (PWB) industry loses more than $70 million
annually in boards discarded due to hole-to-land misregistration. The
Interconnect Technology Research Institute (ITRI) created an Improved
Registration Project Team to investigate the problem, and has just made the
report on its findings available for purchase.

In its report, PWB Hole-To-Land Misregistration: Causes and Reliability,
Project Final Report, the team concluded The requirement for an intact
annular ring at every innerlayer pad is excessively conservative. "This
study demonstrates that the requirement prohibiting breakout should be
changed to one that maintains a minimum spacing to adjacent circuits," says
Marshall Andrews, Chief Executive Officer of ITRI. "This change will allow
PWB fabricators and their customers to save millions of dollars while
improving board routability."

This conclusion culminates two years of research by ITRI. The project team
created a PWB test vehicle that was designed to have different degrees of
pad breakout from none to just a plated hole in a circuit line with no pad.
Hole reliability tests were conducted by thermal cycling the boards from
-65 to +125 degrees centigrade. No failures due to the line to barrel
connection were found even after 1000 cycles, 10 times the specification
requirement.

For more information on the report, or ordering instructions, contact Diana
Hempstead, Administrator, at ITRI at (512) 833-9930, fax questions to (512)
833-9925, or e-mail [log in to unmask]

ITRI is an industry-led consortium for collaboration among the electronic
interconnection industry, government and academia. Its purpose is to
enhance the global competitiveness of the North America electronics
interconnection industry by enabling collaboration among its members to
accelerate development and application of revolutionary and evolutionary
technology.