HALT/HASS Testing Guide: What Is HALT/HASS Testing?

Creating a reliable product that is easily manufactured, handled and shipped that is also of service to your customers for a sufficient amount of time isn’t an easy task. Innovation is at an all-time high and customers expectations are only getting higher. The market demands manufacturers to release new high-quality products that last at an increasingly higher rate.

Traditional test methods often take several weeks or upwards of many months to find any lackluster components of a product’s design. Even then, results are not guaranteed. Identifying these inferiorities is essential so that they can get fixed before they become expensive field issues.

Newer methods of product reliability testing can drastically shorten the amount of time it takes to find these weak points and can reach completion in as little as a couple of hours. Among the highest rated testing methods are HALT and HASS testing. Understanding what HALT/HASS testing is and applying these types of testing will allow improved product reliability that frees up time for other endeavors, and in turn, increases the revenue your company will be able to bring in.

what is halt testing

What Is HALT Testing?

There are typically two different ways to fatigue a component. You can either use low levels of stress for many cycles or use a very high level of stress for much fewer cycles.

Highly Accelerated Life Testing, or HALT, is a system to test product robustness that uses progressively higher stresses to force product failures. HALT testing makes it possible to elevate stress to a much higher degree, thus drastically shortening the time it takes to identify the weakest components confidently.

Stressors included in a HALT test commonly include extreme temperatures, electricity, thermal shock, vibration and voltage variation. There also may be other elements tested depending on the specific product. The stressors are generally conducted in a fixed sequence as follows:

  1. 1. Cold Step Stress
  2. 2. Hot Step Stress
  3. 3. Rapid Thermal Transition Cycling
  4. 4. Vibration Step Stress
  5. 5. Combined Environmental Stress

You may be wondering what Rapid Thermal Transition Cycling is and how it ties into the HALT process. Once the cold and hot operating limits have been determined from the previous tests, the temperature of the HALT chamber rapidly cycles between those temperatures during the Rapid Thermal Transitioning process. This test is particularly advantageous for discovering failures due to timing issues as well as components that do not operate well with temperature variation.

At each stage of testing during the dwell periods, the product is functionally tested to determine if it is still operating or if there is any failure from the stresses applied. If a component is damaged, if possible, it will be repaired temporarily so the testing can continue. After a full sequence of HALT testing, engineers may decide to make changes to the product, then it undergoes more sequences of HALT tests, expanding its failure limits to maximize margins and optimize its durability.

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applications for halt testing

Applications for HALT Testing

HALT testing is used to discover weak points in a product before design completion. Pinpointing the failure points of a prototype in the design phase allows designers to adjust their designs and create a better end product. Testing can be valuable at all levels of production, including systems, subsystems and components.

By applying HALT testing to products before they hit the market, you can tell where changes need to be made, and by doing so, create a better and more durable product that will provide more value to your customers. In turn, it reduces the cost of field failures, which can become very expensive. Analyzing each component and determining the cause of the failure can become time intensive, but pales in comparison to that of traditional test methods.

Engineers praise HALT testing techniques because it lets them improve the design of their products in a much easier and time effective way. The less a company has to roll out warranty services and product recalls, the better. These damage mitigation techniques can become extremely expensive and should be avoided at all costs.

The overall goal of HALT testing is to reach the Fundamental Limit of Technology (FLT). The FLT is the level of stress where a product no longer operates and is unrecoverable. Different materials and components will react differently to various temperatures. Plastic typically softens and becomes unusable at 100 degrees Celsius, while solder used in circuits can last until 250 degrees Celsius.

However, one disadvantage of HALT testing is that testing for FLT may produce exaggerated repairs that will never be necessary in the field, and are impossible to replicate. Doing so could become an added expense if you push these tests to the limits and use a large number of units, which is the protocol for HALT testing. HALT testing is considered a discovery test, so you must be flexible while performing them.

Reliability growth testing (RGT) goes hand-in-hand with HALT testing and is used to provide engineers with feedback about the stress tests being conducted. RGT captures information from previous tests and uses it to ensure that future concerns are dealt with appropriately. All the information gained from HALT and RGT allows engineers to take corrective action, which can include recoding software, redesigning components or making adjustments to the configuration of a product.

What Is HASS Testing?

After HALT testing, Highly Accelerated Stress Screening (HASS) is a follow-on method to monitor the manufacturing process.

HASS is an additional screen used to detect flaws that were not caught by Environmental Stress Screening (ESS) or any other test methods used to get the product to where it is at this point in the development process.

During HASS testing, stressors are applied beyond the product specifications but not further than the capability determined by the HALT test done before the HASS is conducted. The stressors applied are still much more rigorous than those of traditional testing and can correct manufacturing issues much quicker and earlier. Engineers are then able to make necessary corrections to further ensure there will be no problems through shipment and normal use of the product.

The typical routine for conducting a HASS test includes:

  1. Selecting appropriate stresses, which most commonly include vibration and thermal cycling
  2. Determining what the appropriate levels of stress are that will find the pertinent defects while not using more than 10 percent of the product’s expected life
  3. Using a sample at 100 percent initially
  4. Analyzing each failure and correcting the product

This process is repeated through four cycles, increasing the operational level each time if faults were not detected. The four cycles repeat until failures occur in the first HASS cycle.

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Applications for HASS Testing

The primary focus on HASS testing is increased reliability and upgrades the out-of-the-box quality of a given product. It exposes flaws in products and can occur during manufacturing to ensure that it does not fail in the field. Preventing poorly designed products from going out on the market will help make a customer’s view of what you produce to be more worthwhile due to those products lasting their estimated life and beyond. We’ve all had electronics, particularly cell phones, become faulty months before our plan allows for a replacement, and there’s nothing more frustrating. You don’t want that negative stigma surfacing when a consumer is looking into investing in your product offerings.

HASS is an excellent process for product screening because it can be streamlined to automate testing, create reports, and implement a feedback system that can be used to better communication between the designer and manufacturer. All of this combined can significantly reduce test time by creating a more seamless experience and offers more insight.

Abstaining from HASS testing risks letting dormant failures go unnoticed. It is also much less destructive than HALT testing, so a good product will remain intact. The test screening leaves the product with a high amount of useful life when testing is complete. If product failures occur during HASS, it will be necessary to determine if the failures are due to faulty components, over-stressing or some other factor.

difference between halt and hass

Difference Between HALT and HASS

The HALT and HASS meanings are similar, however, both come into play at different times during the product testing process. The most significant difference between HALT and HASS stress testing is when to conduct them and the goals in mind for execution.

HALT testing takes place before manufacturing a product, during its development phase. It allows engineers to quickly discover potential issues in a new or revised product design, then designers and engineers use that insight to decide which components to incorporate into the final product. It also only stresses on lower operational levels and does not bring the same kind of intensity as HASS testing does.

HASS testing comes into play once the product is ready for manufacturing. The actual test levels may be beyond the product’s specifications but will be tailored to make sure no damage occurs to good hardware. This form of accelerated stress testing is used to help assure companies that their product will be able to withstand environments such as shipping that can be much more intense than the setting it is expected to be at most of the time.

Both HALT and HASS contribute to ensuring the reliability of a product, and alert companies to defects in their products they may otherwise have missed. These tests also should be used in conjunction with other reliability testing strategies to cover all bases and get a complete picture of how your product responds in any situation. The benefits of overstress testing can be tremendous if used in a responsible way that avoids waste.


HALT and HASS testing are commonly used in electronic and electromechanical assemblies. These markets require products to be released to the market very quickly, so HALT/HASS tests are particularly advantageous in this domain. This strategy of testing also maintains a good track record in the aerospace and medical industries because of high-reliability demands in these industries.

HALT and HASS testing is also a good fit for military applications. Data acquisition systems are collections of hardware and software that work together to allow an individual to control the physical characteristics of something remotely. The reliability of these systems is extremely crucial to government projects, and after researching the best practices to test these systems, government researchers determined HALT and HASS methods for their stress tests were some of the most effective.

Contact Quality Testing Services for Your HALT/HASS Testing

Outside test labs provide many benefits to manufacturers. Independent third-party verification of product performance is unbiased and generally perceived as more credible than in-house operations. Testing equipment is also costly and can be difficult to operate efficiently, so turning your reliability testing over to an expert in the field will save your company from having to purchase and maintain expensive equipment. Implementing a proper testing regimen can save companies millions by detecting problems before they become expensive recalls that can damage a company’s reputation.

Studies conducted in accelerated reliability testing labs have shown that 32% of faulty components would go unnoticed without reliability planning procedures that include HALT and HASS testing. At Quality Testing Services, we collaborate with engineers to help design tests that quickly reveal weaknesses in products so they can make changes and improve the products before they go to market.

We offer HALT/HASS testing to help you identify and correct design issues with new or re-designed equipment. If you need special tooling or a custom test to accomplish your goals, we can tailor our methods to best suit your industry’s requirements. You can achieve the highest level of customer satisfaction by ensuring your products are free from defects.

Quality Testing Services is a small, yet highly skilled test lab in Southern California that can put full focus on your needs by offering many services with competitive, flexible and fair pricing. If you have any questions about HALT/HASS testing or any of our other testing services, don’t hesitate to contact us. You can also request a free consultation by filling out our request a quote form. We look forward to hearing from you.

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Related Resources:
HALT and HASS Testing Services
Product Testing Checklist
Is Product Testing Important?

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