What is Highly Accelerated Stress Screening (HASS)?

HASS testing, short for Highly Accelerated Stress Screening, is used by manufacturers to identify possible defects and deficiencies in products. During testing the product will be put under different kinds of stresses to simulate the ageing process faster, including high temperatures, vibration, temperature shocks, and electrical stresses. These will hopefully uncover issues that would otherwise only become apparent once the product has been in use in the field for some time.

Highly Accelerated Stress Screening testing provides a number of interesting benefits, including more reliable and better quality products, happier customers, fewer product returns, and lower product development costs due to problems being found and fixed early enough before it becomes very expensive to do so.

With this in mind, let’s explore what Highly Accelerated Stress Screening testing is, when and how to do it, the equipment used, the time and budget required, and more, right here…

Table of Contents

What is a Highly Accelerated Stress Screening (HASS)?

The product is subjected to a variety of challenges beyond its typical working range during HASS testing, including temperature, vibration, humidity, altitude, and electrical stress. Engineers can find potential flaws or problems in a product by putting it into these loads that would not have been detected using typical testing procedures. The data collected during testing is then analyzed to establish the stress levels at which the product fails and to design a corrective action plan for any failures found.

Highly Accelerated Stress Screening. Why do I need it and when should I do it?

It is critical to fully test new electromechanical goods before they are released during the product development phase. Highly Accelerated Stress Screening (HASS) is a valuable testing methodology that can assist engineers in accomplishing this goal by submitting products to accelerated loads in order to uncover any flaws or problems. HASS testing can detect these errors faster than standard testing methods, making it a more efficient and effective approach to identifying potential difficulties.

You can see the graph here shows the different stages of the new product introduction (NPI) process and when each type of testing (in blue) starts during it. HASS would generally take place at the initial production stage. This will allow the product design to be verified and identify any design weaknesses that can be addressed before releasing too many products into the market.

Highly Accelerated Stress Screening screens electronic devices and components for flaws and weaknesses that could cause them to fail prematurely in operation. HASS is a more severe form of Accelerated Stress Testing (AST), a comparable method used to verify product reliability by subjecting it to adverse environmental conditions.

HASS is often performed on a representative sample of the manufactured items or components. The test is supposed to be extremely stressful, and it is conducted in a controlled atmosphere with close monitoring of the product’s performance and behavior. The test is usually carried out in a HASS chamber, which is a specialized testing chamber intended to generate the required stress conditions. These chambers are similar and often the same as those used in HALT testing.

The product is subjected to a series of stress cycles, such as extreme temperatures, rapid temperature changes, vibration, and mechanical shock, that are similar but far greater than those conditions expected to be encountered during normal use, each lasting several minutes, throughout the HASS process. During each cycle, the product is continuously checked, and any defects or weaknesses that are discovered are immediately rectified.

Risks of NOT doing highly accelerated stress screening

For organizations that develop electro/mechanical products, the risks of not completing Highly Accelerated Stress Screening (HASS) could prove enormous. Without HASS testing, a company risks releasing a product that fails early or does not match the performance and reliability criteria that customers demand. This can result in costly product recalls, reputational damage, and lost sales.

Furthermore, typical testing methods may fail to find flaws or faults in a timely manner, and the time required to detect such issues may stretch beyond the product’s launch date. HASS testing, on the other hand, can swiftly uncover such vulnerabilities and provide a way for the company to correct them before releasing the product. It is used to identify and eliminate materials and workmanship flaws in hardware.

What are the steps involved with Highly Accelerated Stress Screening?

Carrying out a Highly Accelerated Stress Screening (HASS) test on an electronic product involves several detailed steps to ensure the accuracy and reliability of the results. Each test should be designed and configured to match the product you are developing and testing, but these steps are consistent:

Define the test specifications: The first step in a HASS test is to define the test specifications, which include the stress factors that the product will be subjected to, such as temperature, humidity, vibration, and electrical stress. The test specifications should be based on the product’s intended use and the environmental conditions it is likely to encounter.
Determine the test plan: Once the test specifications have been defined, the test plan should be determined. This includes the testing procedures, the equipment required, and the data analysis and reporting procedures.
Prepare the test chamber: The test chamber should be prepared according to the test specifications. This may involve setting the temperature and humidity levels, installing vibration or mechanical stress equipment, and ensuring that the test chamber is properly sealed to prevent any outside interference.
Set up the test equipment: The test equipment should be set up according to the test specifications, which may include thermal chambers, vibration equipment, electrical testing equipment, and data acquisition systems.
Perform initial testing: Before starting the actual HASS test, initial testing should be performed to ensure that the test equipment is functioning correctly and that the test chamber is properly sealed and functioning.
Begin the HASS testing: Once the initial testing has been completed, the HASS test can begin. The product should be placed in the test chamber and subjected to the specified stress factors according to the test plan.
Monitor and record data: During the HASS test, data should be continuously monitored and recorded using the data acquisition system. This data should be analyzed and reported at regular intervals to identify any potential failures or issues with the product.
Modify the stress levels: If the product is not failing during the HASS test, the stress levels can be increased to encourage failures and identify potential weaknesses in the product’s design.
Record and report the results: Once the HASS test has been completed, the results should be recorded and reported, including any failures or issues identified during the testing. These results can be used to improve the product’s design and manufacturing processes.

What are the typical stresses used in HASS testing?

The stresses used in Highly Accelerated Stress Screening (HASS) testing may vary depending on the product or component being tested and the environmental conditions that it is likely to encounter during its normal use. However, some typical stresses that are often used in HASS testing include:

Temperature

Temperature is one of the most common stress factors used in HASS testing, as it can significantly impact the performance and reliability of many electro/mechanical products. During HASS testing, the product is subjected to a range of high and low temperatures that are beyond its normal operating range, in order to simulate the thermal stresses that the product may experience during use.

Temperature cycling is a common technique used in HASS testing to simulate thermal stress. During temperature cycling, the product is subjected to a series of rapid temperature changes, typically between two extreme temperature ranges. These rapid temperature changes can cause thermal expansion and contraction of the materials, which can reveal latent defects or weaknesses that may not be apparent during normal operation.

For example, let’s consider a printed circuit board (PCB) used in an automotive application. During normal operation, the PCB may experience temperature fluctuations due to changing weather and driving conditions. However, during HASS testing, the PCB may be subjected to more extreme temperature cycles to simulate the thermal stress it may experience during use. The product may be exposed to temperatures ranging from -40°C to 125°C in a matter of seconds, with each cycle lasting for several minutes. This can help identify any weaknesses or defects in the PCB, such as cracked solder joints or delamination of the circuit board, that may not be visible during normal operation.

Another example is a server rack used in a data center. During normal operation, the server may be housed in a temperature-controlled environment, but during transportation or installation, it may be subjected to extreme temperatures. HASS testing can subject the server to temperature cycles ranging from -30°C to 60°C, with each cycle lasting for several hours, to simulate the thermal stress it may experience during shipping and installation. This can help identify any defects or weaknesses in the server’s components, such as hard drives, power supplies, or fans, that may fail under extreme temperatures.

Vibration Testing

Vibration is another common stress factor used in HASS testing. Mechanical vibration can significantly impact the performance and reliability of many electro/mechanical products. During HASS testing, the product is subjected to a range of mechanical vibration frequencies and intensities that simulate the mechanical stress the product may experience during use.

Vibration testing is used to simulate the effects of mechanical stress that the product may experience during transportation, handling, or in harsh environments. During vibration testing, the product is subjected to a range of frequencies and intensities that may cause the product’s components to experience fatigue, looseness, or failure. Vibration testing can reveal latent defects or weaknesses that may not be visible during normal operation.

For example, consider a drone used in a military application. During normal operation, the drone may experience some level of vibration due to its propellers’ movement. However, during transportation or when deployed in a harsh environment, the drone may experience more intense and frequent vibration levels that can impact its performance and reliability. HASS testing can subject the drone to a range of vibration frequencies and intensities that simulate the mechanical stress it may experience during transportation or in harsh environments. This can help identify any defects or weaknesses in the drone’s components, such as the motors, gears, or circuit boards, that may fail under mechanical stress.

Another example is a medical device used in a hospital setting. During normal operation, the device may not experience significant vibration. However, during transportation or in a clinical environment, the device may be subjected to vibration levels that can impact its functionality and reliability. HASS testing can subject the device to a range of vibration frequencies and intensities that simulate the mechanical stress it may experience during transportation or in clinical environments. This can help identify any defects or weaknesses in the device’s components, such as sensors, motors, or connectors, that may fail under mechanical stress.

Humidity Testing

Humidity is another stress factor that can significantly impact the performance and reliability of many electro/mechanical products. During HASS testing, the product is subjected to high humidity levels that are beyond the normal operating range to simulate the effects of moisture and condensation on the product, which can cause corrosion and other types of damage.

Humidity testing is used to simulate the effects of moisture and condensation that the product may experience during use, such as in humid or wet environments. When moisture is present, it can lead to corrosion, rust, and other forms of damage that can affect the product’s performance and reliability. Humidity testing can help identify any defects or weaknesses in the product’s components that may fail under high humidity conditions.

For example, consider an outdoor security camera that is designed to operate in various weather conditions. During normal operation, the camera may be exposed to some level of humidity or moisture. However, in humid or wet conditions, the camera may be subjected to high levels of moisture that can lead to corrosion or mold growth, affecting its performance and reliability. HASS testing can subject the camera to high humidity levels to simulate these conditions and identify any defects or weaknesses in its components, such as the lens, sensors, or circuit boards, that may fail under high humidity conditions.

Another example is a smartwatch that is designed to be worn during exercise or in wet environments. During normal operation, the watch may be exposed to some level of humidity or moisture. However, in wet conditions or during intense exercise, the watch may be subjected to high levels of moisture that can lead to corrosion or other forms of damage, affecting its performance and reliability. HASS testing can subject the watch to high humidity levels to simulate these conditions and identify any defects or weaknesses in its components, such as the battery, sensors, or connectors, that may fail under high humidity conditions.

Altitude Testing

Altitude testing is another form of HASS that is used to simulate the conditions that a product may encounter at high altitudes. During altitude testing, the product is subjected to reduced atmospheric pressure to test its performance and reliability under these conditions. This type of testing is often used in the aerospace and military industries, where products such as aircraft, satellites, and missiles need to perform reliably at high altitudes.

At high altitudes, the atmospheric pressure is significantly reduced, which can affect the performance of many electro/mechanical products. For example, aircraft engines need to operate efficiently at high altitudes to provide enough thrust to keep the plane in the air. Similarly, satellite components need to be able to function correctly under reduced atmospheric pressure to ensure reliable communication and data transmission.

Altitude testing can help identify any potential weaknesses or defects in the product’s components that may affect its performance and reliability under high-altitude conditions. For example, during altitude testing of an aircraft engine, the engine is operated under reduced atmospheric pressure to test its performance and efficiency at high altitudes. If any defects or weaknesses are identified during the testing, they can be addressed before the product is deployed in the field.

Another example is the testing of military equipment, such as missiles or drones, that may be used at high altitudes. During altitude testing, the product is subjected to reduced atmospheric pressure to test its performance and reliability under these conditions. This type of testing is critical to ensure that the equipment functions correctly when deployed in the field.

Electrical stress testing

Electrical stress testing is a key component of HASS that is used to test the electrical performance and reliability of electro/mechanical products. During electrical stress testing, the product is subjected to high voltage or current to simulate the conditions that the product may encounter during use. This type of testing is critical to ensure that the product can withstand high electrical stress and perform reliably under these conditions.

Electrical stress testing can identify potential weaknesses or defects in the product’s electrical components that may cause the product to malfunction or fail during use. For example, if a product has a voltage regulator that is not properly designed to handle high voltage levels, the regulator may fail when subjected to high electrical stress. By subjecting the product to high voltage or current during testing, any potential weaknesses or defects can be identified and addressed before the product is deployed in the field.

Another example of electrical stress testing is the testing of electrical cables and connectors. During testing, the cables and connectors are subjected to high electrical stress to test their performance and reliability under these conditions. This type of testing is critical to ensure that the cables and connectors can handle high electrical stress and maintain their electrical conductivity over time.

The term Step Stressing is often used, how is this implemented in HASS testing?

Step stressing is a method that is often used in Highly Accelerated Stress Screening (HASS) testing to gradually increase the levels of stress applied to a product or component over a series of steps. This approach can help to identify the specific stress levels at which the product or component is likely to fail, allowing for targeted testing and analysis.

In step stressing, the product, sub-assembly, or component is subjected to a series of stress levels, with each level being applied for a set amount of time. The stress levels are gradually increased over the course of the test, with the goal of identifying the level at which the product or component begins to fail. The stress levels may be increased in a stepwise fashion or may be gradually ramped up over time.

For example, a step stressing test for a printed circuit board might involve subjecting the PCB to increasing levels of temperature stress in 5°C increments, with each increment being applied for 30 minutes. The temperature would be raised by 5°C after each 30-minute cycle until the PCB begins to exhibit signs of failure. Once the point of failure is identified, the specific stress level that caused the failure can be targeted for further testing and analysis.

Step stressing can be used in combination with other stress testing methods, such as temperature cycling, vibration testing, and electrical stress testing, to identify the specific stress conditions that are likely to cause failures in the product or component. By identifying these specific stress conditions, manufacturers can improve the reliability and quality of their products and reduce the likelihood of product failures in the field.

Why is LOL & UOL mentioned? (It’s not what you think ❌ 😂 )

Changes in temperature can affect the performance and reliability of electronic circuits. Therefore, during Highly Accelerated Stress Screening (HASS) testing, the temperature is often used as a stress factor to identify potential issues with the product or component being tested.

To test the impact of temperature stress on the product, cold and hot thermal step stressing are often used. Cold thermal step stressing involves subjecting the product to gradually decreasing temperatures, while hot thermal step stressing involves subjecting the product to gradually increasing temperatures.

During cold thermal step stressing, the product is subjected to progressively colder temperatures until it reaches the Lower Operational Limit (LOL). The LOL is the lowest temperature at which the product is still able to function normally. If the product fails to function properly before reaching the LOL, this indicates that there may be an issue with the product’s design or manufacturing process.

Image source: https://qualityinspection.org/product-functional-testing/

In addition to identifying the LOL, cold thermal step stressing can also reveal the Lower Failure Limit (LFL). The LFL is the lowest temperature at which the product is no longer able to function, and beyond which it may be permanently damaged.

During hot thermal step stressing, the product is subjected to progressively hotter temperatures until it reaches the Upper Operational Limit (UOL). The UOL is the highest temperature at which the product is still able to function normally. If the product fails to function properly before reaching the UOL, this indicates that there may be an issue with the product’s design or manufacturing process.

In addition to identifying the UOL, hot thermal step stressing can also reveal the Upper Failure Limit (UFL). The UFL is the highest temperature at which the product is no longer able to function, and beyond which it may be permanently damaged.

Overall, the use of cold and hot thermal step stressing during HASS testing can help to identify the temperature limits at which a product is likely to fail or become damaged. This information can be used to improve the product’s design and manufacturing process, as well as to set appropriate temperature specifications for the product’s normal use.

What is the vibration operational limit?

During Highly Accelerated Stress Screening (HASS) testing, vibration step testing is often used to determine a product’s resilience to mechanical stress, such as the forces encountered in its intended environment. Vibration step testing involves subjecting the product to progressively higher levels of vibration stress in a cyclic procedure, beyond normal operating levels that the product would be expected to experience. The goal of this testing is to identify potential weaknesses in the product’s design that could lead to failures in the field.

The vibration operational limit (VOL) is the vibration stress level at which a product begins to malfunction but can be returned to normal operation once the stress is decreased or removed. Identifying the VOL can help manufacturers set appropriate vibration specifications for their products and ensure that they are robust enough to handle the stresses they are likely to encounter in their intended environment.

During vibration step testing, typical failures include cracking or loss of mechanical strength due to fatigue. As the stress levels are increased, failures are encouraged in an accelerated timeframe, which highlights weaknesses in the product’s design that may not be apparent during normal use.

If the product fails to resume normal operation once the stress is reduced, this is an example of a hard failure. The stress level at which a hard failure occurs is called the Vibration Destruct Limit (VDL). Once the product reaches the VDL, it will no longer operate unless some type of repair is performed.

What are ‘Soft’ and ‘Hard’ Failures in terms of HASS Testing?

During Highly Accelerated Stress Screening (HASS) testing, products are subjected to various stress factors in order to identify potential issues or failures that may occur during normal use. These failures can be classified as either soft or hard failures, based on whether the product is able to resume normal operation once the stress is removed.

A soft failure occurs when the product under test ceases to operate correctly when subjected to a specific stress condition, such as extreme temperatures or high vibration but is able to resume normal operation once the stress is removed. For example, if a product is subjected to extreme temperatures during testing and stops functioning correctly, but returns to normal operation once the temperature is brought back within its normal operating range, this would be considered a soft failure. Soft failures can indicate that the product is not robust enough to handle certain stress conditions, but may still be usable under normal operating conditions.

On the other hand, a hard failure occurs when the product is unable to achieve normal operation, even under normal operating conditions, after being subjected to a specific stress condition. For example, if a product fails to operate correctly during HASS testing and is unable to resume normal operation even after being returned to normal operating conditions, this would be considered a hard failure. Hard failures can indicate more serious issues with the product, such as design flaws or manufacturing defects that could potentially result in product recalls or safety hazards.

What equipment is used in the HASS testing?

The equipment used in HASS testing may vary depending on the specific testing requirements and the nature of the product being tested. Generally, a HASS testing system consists of a chamber, which can be environmental or thermal, capable of maintaining a specific temperature and humidity level, and a vibration table, capable of subjecting the product to mechanical vibration.

Additionally, a HASS testing system may include electrical stress equipment, such as high-voltage or high-current sources, to test the product’s electrical performance. Data acquisition systems, including sensors and data loggers, are also used to monitor and record the product’s performance during the testing process.

It is important to note that the equipment used in HASS testing must be properly calibrated and maintained to ensure accurate and reliable results. Calibration and maintenance procedures should be performed regularly to ensure that the testing equipment is functioning properly and that the test results are accurate.

Environmental chambers: These chambers are used to control the temperature and humidity during temperature cycling and humidity testing.
Vibration shakers: These shakers are used to apply controlled vibrations to the product during vibration testing.
Data acquisition systems: These systems are used to collect and analyze data from the product during the HASS test.

Note 👉 We can arrange this test — you can refer to our own testing lab, RSQ-Labs.

In HASS testing, the focus is on quickly screening for defects and weaknesses in the product by subjecting it to high levels of stress using temperature, vibration, and other stress factors. The equipment used for HASS testing includes environmental chambers, vibration shakers, and power supplies, as well as specialized HASS chambers that are designed to rapidly cycle between stress levels.

The image below shows an environmental test chamber that is capable of temperature cycling and humidity cycling tests (also used for HALT testing, by the way).

(Image source: Thermotron.com)

How long does it take to complete HASS testing?

The length of time required to complete HASS testing can vary greatly depending on a variety of factors, including the complexity of the product being tested, the severity and duration of the stress levels applied, and the desired level of confidence in the results.

In general, the testing can take anywhere from a few hours to several days to complete. However, for highly complex products, the testing process can take several weeks or even months to fully complete due to the need for more extensive testing and time to analyze the data.

Other variables that can affect the length of time required for HASS testing include the number of stress levels applied, the duration of each stress level, and the number of cycles completed at each stress level. Additionally, the length of time required for HASS testing may also depend on the desired level of confidence in the results. Higher confidence levels typically require more extensive testing and data analysis, which can increase the time required.

What budget would I expect to complete HASS tests?

HASS costs vary greatly depending on a variety of factors such as the complexity of the product, the number of tests required, and the equipment and labor costs involved. Generally, the cost can be broken down into three main categories:

Equipment: Equipment costs can vary depending on the specific tests required for the product being tested. Environmental chambers, vibration shakers, and data acquisition systems can range in cost from a few thousand to tens of thousands of dollars. The number and type of equipment required will depend on the specific HASS tests being conducted.
Labor: Labor costs will also depend on the complexity of the product and the number of tests required. Engineers and technicians with specialized training and experience are typically required to perform HASS testing and the hourly rates of the personnel involved and the length of time required to complete the tests impact this.
The number of tests: A single test may take several days to complete, so the cost will increase with the number of tests needed. Additionally, multiple tests may be required to identify and address any potential weaknesses or defects in the product.

The expense for a HASS test might range from a few thousand dollars for a simple test to several tens of thousands of dollars for a full and complex test. The precise budget will depend on the product, the type of test being conducted, and the amount of granularity required for the data analysis.

For more information on how we can help, contact us to discuss your test requirements.

Who would benefit from using highly accelerated stress screening?

Any company or organization that wants to ensure the quality, reliability, and durability of its products.
HASS can be particularly useful for companies that produce products for industries where failure could have serious consequences, such as aerospace, automotive, and medical devices.

Product designers and manufacturers.
It can help them identify potential design weaknesses or defects early in the development process. This can save time and resources in the long run by preventing costly product recalls, repairs, or replacements.

End-users of products.
It can provide greater assurance of product quality and reliability. This can help build trust in the brand and increase customer satisfaction, which can lead to greater sales and revenue.

Examples of products that would benefit from HASS testing:

HASS can be applied to a wide range of products, including electronic devices, mechanical systems, and consumer goods; especially if they need to perform reliably in a range of environmental conditions. Ensuring customer satisfaction by providing reliable products is paramount for any business, but this also improves brand reputation which every company should be striving for.

Some examples of products that would benefit from HASS testing include:

Electronics: Electronic products, such as smartphones, laptops, and gaming consoles, are often subjected to temperature and humidity changes during shipping and use. HASS testing can identify any potential weaknesses in these products and help ensure they perform reliably under a range of environmental conditions.
Automotive components: Automotive components, such as engines, transmissions, and suspension systems, are exposed to a wide range of stresses and loads during use. HASS testing can help identify any weaknesses in these components and ensure they meet the high safety standards required for the automotive industry.
Aerospace components: Aerospace components, such as avionics, guidance systems, and landing gear, are subjected to extreme temperatures, pressures, and vibrations during flight. HASS testing can help ensure these components can withstand these stresses and perform reliably in a range of flight conditions.
Medical devices: Medical devices, such as implants, diagnostic equipment, and surgical tools, must perform reliably in a range of environmental conditions. HASS testing can help identify any weaknesses in these devices and ensure they meet the high safety standards required in the medical industry.
Consumer products: Consumer products, such as appliances, toys, and sporting equipment, are subjected to a range of stresses and loads during use. HASS testing can help identify any weaknesses in these products and ensure they perform reliably under a range of environmental conditions.

Summary of HASS

HASS testing is an essential tool for technical engineers and designers to ensure the reliability and durability of electronic products. By identifying design weaknesses and addressing them before the product reaches the market, HASS testing helps to improve product quality and minimize the risk of product failures, which can have significant financial and reputational costs for manufacturers.

Furthermore, HASS testing can help to reduce development time and costs by identifying potential failures early in the design process. By detecting and addressing issues early, engineers can avoid costly redesigns and delays in the product development timeline.

Various graphs can be plotted from the results of HASS testing, including time-to-failure (TTF) graphs, histograms, probability density function (PDF) graphs, Weibull distribution graphs, and stress versus failure rate graphs. These graphs help analyze the product’s performance under stress, identifying stress levels at which the product fails and its resilience to stress.

In summary, HASS is crucial in developing a new product as it ensures that the product meets quality standards, reduces the risk of costly product recalls, identifies root causes of failures, and reduces development time and costs. By subjecting the product to extreme stress levels, engineers can detect and address weaknesses or defects in the product before it is released to the market, ensuring its reliability and safety for consumers.

How can Sofeast help you with your HASS testing?

Our test laboratory technicians can help you define the test plan and then arrange for HASS testing, for a variety of products. Our HASS testing services can help you evaluate the reliability of a new product or ensure that an existing product can endure the rigors of real-world operation.

We can recreate extreme conditions and stress your product to its limits, revealing any design or manufacturing flaws.

Our objective is to assist you to detect and eradicate any possible reliability issues before they become problems, ensuring that your product is prepared to fulfill your consumers’ needs.

Got any questions or concerns about highly accelerated stress screening for your product? Let us know, we’ll be happy to give you some friendly advice and let you know how we can support you.