HALT and HASS, a new Recommended Practice (RP) from IEST, defines and describes Highly Accelerated Life Testing (HALT) and Highly Accelerated Stress Screening (HASS). IEST-RP-PR003.1 covers the philosophy behind the testing, generic examples of tests, differences between standard testing equipment and equipment used for highly accelerated testing, fixturing considerations, alternative approaches, additional environments, and lessons learned. Following are observations about this ground-breaking RP from Chris Peterson, Chair of Working Group PR003, which developed the document. Purchase RP
While HALT and HASS have been useful tools for over two decades, there has been no truly international standardized practice for using these methods. Instead, certain corporations have come up with proprietary methods, and chamber manufacturers have done some excellent white papers. However, there was no one base document readily available to the public.
Though I expect there will be comments on this RP leading to editing revisions, it is a stepping stone for the industry, a way of showing that accelerated testing can be uniform and measured, and how to make certain that the results are useful.
There are many who believe that the purpose of accelerated testing is simply to break something, that testing levels are chosen at random—and what exactly is "highly"? Experts supporting and opposing accelerated testing have been passionate in their beliefs. This document chooses a middle ground. While explaining how to perform the testing properly, the RP is also careful to point out that accelerated testing is only one tool in the testing toolbox.
For the first time that I've seen in an international document, highly accelerated testing and screening is open to many different types of equipment without a bias against any of them. For vibration, either repetitive shock or electrodynamic shakers can be used. Liquid nitrogen for cooling has its benefits, but mechanical refrigeration is not ruled out. The idea is to use the equipment that is best suited to the test item. This RP should help remove the divider between camps.
This RP would provide excellent guidance for anyone involved in testing, whether or not they are currently using accelerated testing. The ideas behind HASS, especially, are very similar to Environmental Stress Screening (ESS) principles. The RP could spur ideas for better testing, using combined environments, thinking outside the box to get the absolute best out of your testing.
I have wanted a document like this for over 20 years. I brought it to IEC (International Electro-Technical Commission, a sister organization to ISO) and they turned it down saying that none of their other test methods were intentionally destructive. I brought it to ISO who claimed the test methods are neither measurable nor uniform, both of which are false allegations but people weren't used to the methodology.
While I have seen HALT and HASS referenced in annexes of international specifications, it was only IEST that gave the go-ahead for the document to be written. The Working Group consisted of both users and manufacturers of HALT/HASS equipment. This balance means users cannot incorporate demands that the equipment is physically incapable of meeting, and equipment manufacturers cannot skew the guidance to conflict with how users actually apply the testing in their labs. The experts in the group were true professionals, willing to talk issues over, and every one of them showed passion in getting a user-friendly document out to the industry. It is with great pride and pleasure that I got to be a part of this group that made my dream come true: the first truly international, non-corporate specification for HALT and HASS.