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Quality by negotiation.

Article Excerpt
By Martin Rowe, Senior Technical Editor

Engineers at Mercury Computer Systems work together to find the optimal balance among test, signal integrity, thermal analysis, mechanical fit, and component selection.

Chelmsford, MA-For the past 25 years, engineers at Mercury Computer Systems have designed processor boards and systems for military applications, but yesterday's design and test methods no longer work. Higher functionality, increased heat, more sensitive signals, shorter design cycles, higher test coverage, and tighter budgets have all changed how the engineers perform their jobs.

To produce high-reliability products that must run for years in harsh environments, the various engineers at Mercury push for design details that often compete with each other. Test engineers, signal-integrity engineers, and mechanical engineers often negotiate with each other and with circuit and PCB (printed-circuit board) designers early in a design. The result: fewer board iterations, shorter design cycles, and more reliable products. By implementing new procedures, engineers have reduced the number of engineering change orders by a factor of 10.

In 2005, Mercury embarked on a DfR (design-for reliability) project for gathering input from all engineering departments and giving it to designers early in a design cycle. The program stemmed from the fact that many component suppliers were moving to lead-free processes, so Mercury needed to overhaul its entire design, analysis, and test practices. In addition, devices such as microprocessors and FPGAs (field-programmable gate arrays) were running faster while their size was shrinking, which increased heat density and threatened reliability.

Darryl McKenney, director of engineering services, was put in charge of the program. McKenney set out not only to give information to designers earlier, but also to automate the process. He started with component selection, the first part of the DfR project staircase that the company implemented. Since then, the company has implemented programs for all the functions and departments listed in Figure 1 .

'The component turn from lead to lead free has been incredible,' McKenney exclaimed. 'It's the biggest change in electronics manufacturing since the move from through-hole to surface-mount components.' At Mercury, the change to lead-free products affected more than 37,000 components that the company uses in its boards.

Evaluating new components

Because Mercury's boards are often used in...

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