Put a fair amount of stress on the bond between printed boards and electronic components and there’s a chance problems will arise, from solder ball cracking to conductor damage to pad cratering. Although measuring stress was a challenge for EMS and OEM companies, the recently updated joint industry guideline, IPC/JEDEC-9704A, Printed Circuit Assembly Strain Gage Test Guideline, makes it easier for engineers to run strain gage tests during the manufacturing process.
“Revision A is about making sure there’s a common accepted practice for measuring manufacturing strain on printed board assemblies due to board flexure,” said Jagadeesh Radhakrishnan, a reliability engineer with Intel Corp. and leader of the effort within the IPC SMT Attachment Reliability Test Methods Task Group that helped revise the guideline. Whereas the first-generation document provided industry with target pass/fail points, the A revision, as Radhakrishnan explains, “… changes the focus to providing a methodology. It doesn’t give you targets; it thoroughly explains how to measure strain."
Revision A includes formulas for calculating strain and describes techniques for analyzing data derived from these tests. The tests can be performed at many stages during the manufacturing of printed board assemblies. Components can be tested during assembly or during test processes in the factory or just before they’re packaged.
In addition to the change in focus, IPC/JEDEC-9704A has an expanded scope and provides recommendations for sockets and ceramic capacitors; in the past, it just addressed ball grid arrays (BGAs). “It also changes parameters for in-circuit test fixtures, providing best design practices so users will have fewer issues,” adds Radhakrishnan.
IPC/JEDEC-9704A is available for purchase by IPC members for $36. The standard industry price is $72. For more information or to purchase IPC/JEDEC-9704A, visit www.ipc.org/9704.
IPC (www.IPC.org) is a global trade association based in Bannockburn, Ill., dedicated to the competitive excellence and financial success of its 3,100 member companies which represent all facets of the electronics industry, including design, printed board manufacturing, electronics assembly and test. As a member-driven organization and leading source for industry standards, training, market research and public policy advocacy, IPC supports programs to meet the needs of an estimated $2.02 trillion global electronics industry. IPC maintains additional offices in Taos, N.M.; Arlington, Va.; Stockholm, Sweden; Moscow, Russia; Bangalore, India; and Shanghai, Shenzhen and Beijing, China.