The IPC recently released a new revision, IPC-9252A – Requirements for Electrical Testing of Unpopulated Printed Boards. Developed by the IPC Electrical Continuity Testing Task Group under the leadership of Michael Hill, quality control manager for Colonial Circuits, Revision A is a complete rewrite of the original standard published in February 2001. The new document defines levels of appropriate testing and assists in the selection of the test analyser, test parameters, test data and fixturing required to perform electrical testing on unpopulated printed boards and inner-layers.
“This new document defines things much more clearly so this standard can be used as a requirements document,” explained Michael Green, production design engineer for Lockheed Martin, whose comment sheet sparked the revision. “The previous version of the standard was a guideline on how to test boards compared to what is a requirement for what you should test them to. Revision A tells how to do the tests and requirements for the test. Electrical test equipment has got more sophisticated so we needed the document to meet these 21st century requirements.”
Revision A provides expanded coverage of adjacency concepts for isolating testing as well as new requirements for resistive and indirect continuity and isolating testing. Other parameter tests used to screen for conditions are also discussed. The document also addresses common misconceptions regarding flying probe testing.
A major portion of the standard is devoted to adjacency definitions, including adjacency distance, horizontal adjacency distance and vertical layer adjacency. These definitions are important because they vary with every machine. Green points out that when you buy a board you need to know you are getting the same standard no matter who you buy it from. To round out the standard, one of the last sections provides test program verification, electrical test certification and traceability.
Representatives from the printed board, fabrication and test industries, as well as personnel from OEMs and the US Department of Defence cooperated to update the new specification. “This specification, which is invoked by a broad range of industry, military and proprietary specifications, has been extensively revised to address recognised shortcomings within the original document, including new coverage for many commonly employed test methods, off-system fault verification, and minimum requirements for electrical test certification,” said Clifford Maddox, engineering specialist, Material and Processes for The Boeing Company, who played an integral role on the task group.
For more information visit www.ipc.org
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