Why HALT Will Not Give You a MTBF & Why You Should Not Care by Mark Morelli – FREE – 1 hr

Managers and engineers eagerly anticipate accelerated stress test results for various reasons. Some look forward to verify that their products are “reliable”, others look to identify weaknesses in a new design, and still others think that a “reliability number” can be calculated based upon the results.

This webinar will focus on making the case for recommending that results from a particular form of accelerated testing, Highly Accelerated Life Testing (HALT), are not used in the calculation of reliability parameters such as Mean Time Between Failures (MTBF). HALT should instead be used as a means to make a product more robust, which can then withstand the manufacturing and end use environments.

Background The traditional definition of MTBF is the cumulative total operating time divided by the number of failures occurring in a repairable fleet of products. The equation MTBF = OT/NF is used in the airline industry.  For example in a fleet of units fielded with 15 failures occurring in 10 million operating hours the MTBF would be equal to 10 million/15 = 666,667 hours. It doesn’t provide any indication of the underlying failure distribution.

HALT is a process typically applied to electronic products that uses temperature, vibration, and electrical stress in various combinations on a few test articles in order to identify potential weaknesses. Those defects that are likely to occur in the field under expected operating conditions should have corrective action implemented and verified.

Why HALT doesn’t give you a MTBF

This section will provide some examples of why HALT cannot provide a MTBF value.


Mark Morelli has 32 years of reliability and test engineering experience on commercial, industrial, aerospace and military electronic, electrical, electromechanical and mechanical products and systems.  In addition, he has taught mathematics and electrical engineering courses at the University of Hartford and has authored or co-authored and presented several technical papers on the subject of accelerated reliability methods, including a previous Hobbs Engineering conference.

He received a BSEE degree from the University of Hartford. Mark is a recognized leader in the field of accelerated stress testing, including Highly Accelerated Life Testing (HALT) and Highly Accelerated Stress Screening (HASS).  He has planned, performed and supervised hundreds of tests in his career.  On one product line, a 10:1 reliability improvement over the previous version (and millions of dollars in “cost-of-poor quality” savings) was realized within 3 years of implementing a HALT and HASS process.

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