Board manufacturers show interest and concern over new reliability standards
Industry observers are skeptical about a new standard for measuring electronic component reliability, which its framers intend to replace the obsolescent MIL-HDBK-217.
By John McHale
WASHINGTON — Industry observers are skeptical about a new standard for measuring electronic component reliability, which its framers intend to replace the obsolescent MIL-HDBK-217.
The new standard, called Prism, promises fewer penalties for using plastic parts than does MIL-HDBK-217, as well as an extensive database, yet experts from the printed circuit board industry are expressing caution after seeing one of the first public explanations of the new parts-reliability yardstick.
Formulating Prism were reliability experts at the Reliability Analysis Center (RAC) of the Illinois Institute of Technology Research Institute (IITRI) in Rome, N.Y. RAC officials gave a presentation on Prism in April at the Military & Aerospace Electronics magazine COTScon East 2000 conference and exhibition in Washington.
Prism is a software tool that ties together several RAC tools into a comprehensive reliability-prediction methodology. The PRISM concept accounts for factors that can influence system reliability, and combines those factors into an integrated assessment tool.
IITRI experts say they developed PRISM to overcome inherent limitations in MIL-HDBK-217, which the U.S. Department of Defense (DOD) is no longer maintaining or updating.
Many COTS suppliers have abandoned MIL-HDBK-217 for this reason and apply their own tests to determine reliability. The result has been a large disparity among reliability figures for systems and subsystems that use precisely the same components.
"MIL-HDBK-217 certainly needs a replacement," says Gorky Chin, vice president of advanced technology at Vista Controls in Santa Clarita, Calif., who says industry needs to standardize on one system.
"The RAC presentation was very interesting," says Duncan Young, director of marketing at DY 4 Systems in Kanata, Ontario. "It would be good to see it become an open standard. One common solution for calculating reliability would be great."
The problem, Young cautions, is persuading industry leaders to adopt it, and agree to help maintain parts of its database. "They have gathered a lot of historical data and need to develop a method for measuring the reliability of new parts," Young explains.
Among the core challenges to successful industry adoption of Prism is the cultural shift it represents for military systems designers, who are used to receiving the benefits of MIL-HDBK-217 free of charge. They must pay for Prism software — a change that is rubbing some of them the wrong way.
"The problem with Prism is that it is a proprietary model," where people have to buy the Prism software to get the solution, Chin says.
MIL-HDBK-217 still has a large following in the board industry. There were software packages for sale that would help calculate reliability, but for the most part it was free, Chin says.
Yet the new Prism approach must have a cost, says RAC Director Pat Hetherington. Proceeds from sales of the software will help pay for research already completed and for gathering future data on new parts, he says.
The DOD paid to develop the MIL-HDBK-217, but has since stopped, Hetherington adds.
The Prism software retails at $1,995, while users can download future upgrades off the World Wide Web, Hetherington says. RAC, he says, is a not-for-profit organization and all the proceeds go back into the product.
RAC officials plan to upgrade their data every 18 months, Hetherington explains. MIL-HDBK-217, by contrast, offered small updates less frequently than 18 months.
Among Prism's over MIL-HDBK-217 are its accounting for plastic parts and custom ASICs without the harsh penalties that MIL-HDBK-217 set down for plastic use, Hetherington says. There are still penalties if the application warrants it, but not as often as MIL-HDBK-217, he adds.
For more information on Prism contact Dave Dylis by phone at 315-339-7055, by mail at IIT Research Institute/Reliability Analysis Center, 201 Mill Street, Rome, N.Y. 13440-6916, or on the World Wide Web at http://rac.iitri.org.