What is “HALT”?
HALT is primarily a margin discovery process. Throughout the HALT process, the intent is to subject the product to stimuli well beyond the expected field environments to determine the operating and destruct limits of the product. Failures that typically show up in the field over a long period of time at much lower stress levels are quickly discovered while applying high stress conditions over a short period of time. In order to ruggedize the product, the root cause of each failure needs to be determined and the problems corrected until the fundamental limit of the technology for the product can be reached.
This process will yield the widest possible margin between product capabilities and the environment in which it will operate, thus increasing the product’s reliability, reducing the number of field returns and realizing long-term savings.
Typical stresses using during HALT are cold step stress, hot step stress, rapid thermal transitions, vibration step stress, combined thermal and vibration environments, and any other electrical and environmental stresses that are appropriate (voltage margining, frequency margining, etc).
Poor reliability, low MTBF, frequent field returns, high in-warranty costs, and customer dissatisfaction are often the result of design weaknesses, even if a product has successfully passed qualification tests.
In HALT, we can increase the reliability of a product by uncovering design weaknesses and expanding its design margins.
VALUE TO YOUR ORGANIZATION
By uncovering design weaknesses, we improve the design margins of the product, making it more reliable in the hands of the customer. The operating and destruct limits discovered during HALT can also be used to develop an effective Highly Accelerated Stress Screen (HASS) for manufacturing which will quickly detect any process flaws or new weak links without taking significant life out of the product. The HASS process can ensure that the reliability gains achieved through HALT will be maintained in future production.
An example of Reliability Integration during HALT is as follows:
How to Perform HALT in Conjunction with the other Reliability Tools
- Planning for a HALT
- Using results from the Modeling and Predictions, FMECA, and Derating Analyses to help develop the HALT Plan
- Executing the HALT
- Using a Closed-Loop Corrective Action (CLCA) Process for Root Cause Analysis on each failure
- Using the HALT Results
- Using the HALT results to help plan the RDT
- Using the HALT results to help plan HASS
- HALT Plan Writing: A key element of the HALT process is writing the plan. In this plan, we must determine the types of stresses, levels of stresses, and order of stresses. We must also determine the number of samples, functional tests, what parameters to monitor, and what constitutes a failure. Decision in this plan will dictate the relative success of the test.
- Guidance to Prepare for HALT: When a company prepares for a HALT for the first time, there are many steps that can be taken to help prepare for the test to make it run more smoothly, including lining up troubleshooting help, and having spares available.
- Perform HALT (On-Site or at one of our partner test labs):Step up each stress individually to the point of failure. Perform Root Cause Analysis on the failure to determine relevancy. Then choose next stress. At the end, combine stresses together for maximum effectiveness.
- HALT Report Writing: The HALT Report will document the setup of the test, the findings, and recommendations based on our experience of the many hundreds of HALTs we have performed across dozens of different industries.
- Drive Root Cause Analysis: Perhaps the most important step in the HALT process is the Root Cause Analysis process because this is the process that will determine which failures are relevant and how the failures may affect the product in the field. Companies that skip this process may either be chasing non-relevant failures, leading to wasted time and effort and possible embarrassment, or they may dismiss failures too easily, leading to field failures that could have been avoided.
We can help drive this process, guide you as to which failures to fix, and help implement the fixes within your organization.
The following case studies and options provide example approaches. We shall tailor our approach to meet your specific situation.
- The Standard HALT Process including Margin Expansion: For a Computer manufacturer, we started with a generic HALT plan using temperature and vibration as stresses. We performed HALT beyond the first failure, troubleshooting failures as they occurred, and expanding the margins of the product to the fundamental limit of technology of the product for each stress.
- Enhanced HALT process with Tailored Test Plan and Margin Expansion: For a Supercomputer company, we met with engineers and developed a tailored test plan to assure that the temperature and vibration stresses being applied were appropriate for the technology and to assure that we understood technological characteristics and limits prior to starting the testing. Also, as part of the stressing, we included not only temperature and vibration as stresses, but frequency margining as well. This, in combination with the temperature stressing, discovered new weaknesses that the temperature stressing did not find by itself.
- Tailoring HALT to Match Field Results: A Medical Device company had been performing HALT for several years and was still having field issues, yet the products would prove to have wide margins during the HALT process. The problem they were facing was that they were not applying the proper stresses during HALT. For this customer, we researched their field data and determined that we needed to perform input voltage margining in combination with temperature step stressing in order to find a key failure mechanism.
- Using HALT During Root Cause Analysis: During a HALT for a Networking company, we uncovered a flaw with their power supply. Because of our intimate knowledge of power supplies, we took the lead and handled the entire root cause corrective action process for the customer. This included a design change, a Verification HALT, and a field retrofit.