What Is HALT?

Part one of a three-part series describing the Highly Accelerated Life Test, or HALT.

What Is HALT?
Highly Accelerated Life Test (HALT) is a stress testing methodology used to determine product reliability and the operational parameters for a device or component. By simulating real world events (temperature, vibration, UV, etc.) HALT will help determine what environmental stresses the product can withstand, and which it cannot. With HALT, failures which would typically only show up in the field over a long period of time are quickly discovered while rapidly applying high stress conditions.

HALT is useful in almost every phase of product development and can help save time, money, and a company’s reputation. During the design phase it can identify potential design weaknesses at a stage when correcting them is far less costly or difficult than it would be once the device is in production. When a device is ramping into full production, HALT can help identify any issues with the manufacturing process and verify the device is performing to the set specifications. After a product has been fully launched into production, HALT can be used to audit product reliability and see if changes in manufacturing processes, suppliers, or materials are impacting performance.

Figure 1:  Devices are attached to substrate.

Figure 1: Devices are attached to substrate.

Figure 2: All devices cabled and powered and ready for testing.

Figure 2: All devices cabled and powered and ready for testing.

How HALT Differs from MTBF
Both HALT and Mean Time Between Failure (MTBF) evaluate the system’s components, aiming to accurately determine how long the finished product will last under certain conditions. HALT runs the system through a battery of tests meant to simulate real world events at an accelerated pace to provide quick results. Operating the unit with power interrupt, random vibration, rapid temperature cycles, and extreme hot and cold temperatures can demonstrate how a system will perform over years of normal operational stresses.

MTBF is either estimated using data collected over years from units installed in real world applications or by making predictions based on system design and analyzing known information about the components used in the design. Unlike HALT, MTBF typically has limited physical testing, and then only under nominal conditions, and the results of MTBF analysis are almost entirely determined by using mathematics.

What HALT Isn’t
HALT is not a pass/fail environment. It is merely a way to determine the operational and potential destruct limits. At the completion of testing, the data will provide a comprehensive idea of what environmental states the device can perform in and how it might respond to a variety of conditions. HALT is also not a certification process. The hardware will not be certified or accredited to any specifications after HALT is completed.

HALT Processes Vary
HALT test processes vary depending on the lab completing the testing or the applications the device is targeted for. Typically, the main piece of equipment used in HALT is a test chamber capable of withstanding a variety of environmental conditions. The chamber is hooked up to various mechanisms to control temperature, such as liquid nitrogen for fast cooling and high-power resistive elements for fast heating. Most chambers also include a vibration table which uses pneumatic hammers to create multi-axis, 6 degree-of-freedom vibration. The test chamber typically includes viewing windows to allow visual monitoring of the systems during testing.

The lab’s technician helps determine the best layout for the devices in the chamber to make sure they are visible and accessible. Once a layout is agreed upon, the tech will secure the device to a piece of substrate, a DIN rail, or some other secure housing. In turn, the housing will be further secured to the bed of the chamber. Once the systems are securely arranged in the chamber it is a matter of connecting power and other cables, and then it’s time to start HALT.

In the second article in this series we’ll go over preparation for HALT and provide some tips and tricks to make sure the most is made of lab time. The third article will cover the testing steps and show what a typical output looks like using  test results obtained during our case study.

More Than One Reason for HALT
Technologic Systems had multiple reasons to enter into HALT.

  1. Customers requested data and assurances—Our customers regularly deploy out our systems into situations where they are expected to perform reliably. They want to know that our products will operate even under the harshest of conditions.
  2. Improvements in product manufacturing—We have been implementing a variety of manufacturing and product improvements in our devices and wanted to verify that the changes increased the operational limits of the devices.
  3. New product launch—Our TS-7680 industrial single board computer was in the final stages of our engineering sampling program and preparing to launch to full product release. Having the HALT data on hand helped prepare the product and our production and sales team for final launch.
  4. Marketing and sales—HALT metrics can be very powerful marketing tools demonstrating overall product quality.

ABrownAlan E Brown is a Marketing Communications Manager at Technologic Systems.

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