Assuming a random vibe, single-axis screen is performed on a circuit card assembly, what is the optimal direction of vibe?
Case 1 - assume the card has only thru-hole components.
(Thru hole mount is typically rated 5-6 times mechanically stronger than surface mount.) It is an unusual question because for example, axial vs. radial leaded capacitors are greatly affected by vibration direction. On radial leads the direction perpendicular to the direction of vibration would be worst case. Also, use the direction that would give the card the greatest bending deflection.
Case 2 - assume the card has only surface mount components.
Use the direction that would give the card the greatest bending deflection.
Case 3 - assume the card contains both thru-hole and surface mount (mostly surface mount).
Use the direction that would give the card the greatest bending deflection.
HALT, as I'm sure you know, has six degrees of deflection and the stimulation is random, not sine. Sine has many problems that random eliminate. HALT would be the best technique and the fastest to gain information. Many papers were written 2-3 decades ago on single, dual and three axis vibration techniques, comparing one to another. A search would expand your knowledge.
Perhaps coming to the seminar on HALT/HASS that ERI has (I am the presenter) would be beneficial to your needs.
You can check out my web page too www.reliabilityhelp.com
Regards,
ted kalal
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