HALT Testing / HASS Testing

During a routine five-step HALT test, the unit under test is subjected to a combination of vibration and rapid transitions to extremely high and low temperatures. The testing exposes the product to conditions far beyond what would be encountered in the field environment and is commonly used during product development. Highly Accelerated Stress Screening (HASS) is a quality assurance or screening test used for components or sub-assemblies. HASS testing continues until the point of failure is reached; it is often preceded by HALT. The same chamber can be used for both HALT and HASS testing.

What is the relationship between HALT and HASS testing?

Both HALT and HASS use a combination of vibration and rapid transitions to extreme hot and cold temperatures to create a high-stress environment.

HASS, a component-level test that can stress the unit under test to a predetermined level, can be used as a screening tool to identify high or low-quality components.

HALT, often a precursor to HASS testing, is used in the development process to characterize product durability or robustness. The testing uses a series of progressively more difficult combinations of rapid temperature extremes and vibration to stress the unit under test to the point of failure.

Together, these tests can identify potential problems in the product’s design, materials, or manufacturing process. Then, after testing completes, designers and manufacturers can use the high-quality test data to improve the product and possibly avoid costly mistakes.

What is the purpose of Highly Accelerated Life Testing and Highly Accelerated Stress Screening?

Although HALT and HASS testing are subjected to similar test inputs, their primary objectives are different. Put simply, the basic goals of HASS and HALT testing are the following:

• HALT: Identify failure points to then improve upon, thereby increasing a product’s robustness and longevity.
• HASS: Identify either high or low-quality components enabling a higher quality product.

To gain a better understanding of the function of these tests and how they may be applied to your product, let’s dive into more detail.

HALT testing, also known as Highly Accelerated Life Testing, is a reliability test performed during a product’s early development or design stage. The test is engineered to precipitate failures by exposing the test sample to combined temperature and vibration stressors. During a HALT test, a product will endure rapidly increasing mechanical and thermal stresses until failure occurs. With HALT testing, developers can glean essential clues to find the source of defects, create corrective actions, and ultimately produce high-quality, reliable products.

• HALT tests generally include a series of dwells at high and low temperatures, vibration, rapid cycling between high and low temperatures, followed by combined test environments.

After HALT testing concludes, the resulting test data can be used by developers to establish the product’s operational and failure limits and improve product reliability. When screening components is the objective, HALT test data is often used to design the HASS test parameters.

HASS testing, also called Highly Accelerated Stress Screening, is a production screen that identifies components meeting specific criteria. HALT results are used to establish the test limits for HASS; therefore, HASS typically follows HALT. Test units for HASS testing typically come from batches from the production line. This screening process can help determine if a specific lot may have potential issues. The HASS testing process utilizes similar combined environments as HALT. Additionally, HASS test data may help establish the impact of alternative components on a product’s design and durability.

What are the differences between HASS and HALT testing?

Although HASS and HALT testing procedures use the same equipment and stressors, here are key differences between the two tests.