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Del Williams


HALT/HASS Testing Ensures Industrial Flash Storage Performs in Rugged Environments

Accelerated testing quickly detects latent flaws, enables corrective improvements to improve reliability

Published: Monday, May 4, 2020 - 12:02

We are all familiar with flash memory storage devices, the inexpensive “thumb” drives that you stick into your laptop to store and transfer data. However, there are much more rugged industrial flash drives that perform mission-critical storage functions built into systems that you rely on almost every day. You can find these in healthcare imaging, diagnostic, and therapeutic equipment; in aerospace for jet mission data collection, unmanned aircraft base stations, in-flight wi-fi services, and flight recorders; and in transportation for controlling a locomotive subsystem, recording event data, and launching the operating system for a commercial vehicle tracking system.

For industrial product OEMs such as these, flash memory storage devices must be designed and tested to provide mission-critical reliability despite regular subjection to vibration or temperature extremes in harsh environments. Failing to do so risks costly failure in the field that can potentially involve liability if safety is jeopardized, along with serious field service and warranty costs. In the transportation industry, for instance, the unexpected loss of vital data could compromise safety features that drivers rely upon to prevent accidents. In manufacturing automation, data device failures can cause machinery to malfunction, potentially causing safety issues along with production slows or stoppage.

Design qualification using HALT and HASS

Although industrial flash storage is designed to be rugged, different applications have different operating requirements. So, customizing the flash storage device to ensure mechanical ruggedness is necessary to ensure reliability while providing applicable memory capacity and form factors.

Although most of the flash storage industry promotes testing to ensure product performance within specified temperature ranges, industrial flash storage manufacturers that are committed to high reliability will exceed minimum standards. When industrial product OEMs experience flash storage card failures, one of the most common issues is that previous testing did not appropriately replicate real-world conditions for qualification testing.

“The only way that industrial OEMs can be assured that their products will withstand real-world vibration and temperature abuse is to put the flash storage components through the paces with accelerated tests like HALT [highly accelerated life test] and HASS [highly accelerated stress screen],” says Tony Diaz, product manager for Delkin Devices, a value-added supplier of nonvolatile flash storage solutions in a variety of SSD, card, and module solutions.

HALT and HASS techniques shortcut and avoid the problems of slower, traditional methods that only test to minimum specifications. The accelerated techniques quickly expose any weak links in a product by testing well beyond minimum specs so that any reliability problems can be fixed before they become expensive field service, warranty, or liability issues.

Accelerated qualification testing

During HALT testing, according to Diaz, products are exposed to the kinds of extreme environmental conditions that they might be subjected to after they are installed. The temperature is raised and lowered repeatedly, and the memory device is exposed to high levels of vibration. The exact conditions used during HALT can be adjusted to meet specific OEM needs.

“There are four steps to HALT: thermal step testing, rapid thermal cycling, vibration step testing, and combined environment testing,” says Diaz. “One computer manages the testing conditions while another runs the host application in which the memory will be used to emulate real operating conditions as closely as possible.”

Diaz, whose company performs HALT and HASS accelerated testing as well as design verification testing (DVT) and ongoing reliability testing (ORT), says that these results are analyzed in-house so that any necessary design changes can be made efficiently and effectively before the flash storage is used in any industrial OEM devices.

HASS testing is a screening method used to monitor the quality and uniformity of manufacturing by finding production flaws and defects in products. It is often used after HALT testing, as the two are complementary. It’s a verification that the flash storage is fully compatible with the extended specifications and requirements that the industrial application demands.

HASS is performed on a component based on the results of the preceding HALT. The HASS screening stresses are based on the limits identified through HALT, and combinations of stresses are applied simultaneously. The screening pushes the product beyond its operating limits until product failures are caused, and any inherent defects are revealed.

Because the stresses in HASS are more rigorous than those rendered by conventional approaches, the testing accelerates the detection of design issues, so the problem can be corrected and the flash storage device ruggedized to prevent failure in the field.

“Product can often be improved before design release by testing to failure utilizing HALT and HASS,” says Diaz. “Typically, these tests are used to ensure when a design goes to production that it exceeds its promised specifications whether in temperature, vibration, or other areas.”

According to Diaz, with such testing, improvements often can be discovered that allow a product’s design to exceed the specifications listed. For example, traces can be modified or pad sizes reduced or increased to improve soldering when breaks or bad electrical connections are found. Alternatively, connectors can be changed or repositioned to improve overall part performance or longevity.

One of the best ways for industrial OEMs to ensure that a storage device will work as expected in operating conditions is to partner with a manufacturer that offers accelerated testing reliability services. Such testing helps to determine not only failure modes and root causes but also the functional operating limits and destructive limits of flash storage cards. This information can be used to make necessary corrective improvements to significantly improve product reliability.

“The test process up to the release of a new design for production is often like a test of all the parts in the chain,” concludes Diaz. “The most likely weakest link is improved or replaced, then testing is resumed. Then the second weakest link is determined and improved. This process continues until a part well exceeds it specifications, so we can be sure the design and material are solid, and assurances can be taken that this part in mass production is going to exceed the promised specifications in all areas.”

For more information, contact Delkin Devices at (800) 403–8085.


About The Author

Del Williams’s picture

Del Williams

Del Williams is a technical writer based in Torrance, California. He writes about business, technology, health and educational issues, and has an M.A. in English from C.S.U. Dominguez Hills.