The highly Accelerated Stress Test (HAST) is one of the main testing instruments that is employed in reliability tests for electronic parts exposed to severe conditions of the environment. HAST applies increased temperatures, high humidity, and pressure on a device to attain what otherwise would have taken a long time in field conditions. This way, manufacturers get a hint of how long a product will last, where the component will fail, and make adjustments to make it more robust.
Instrumentation
Testing with the HAST chambers is conducted in specific chambers designed to mimic the very extreme conditions of operation. Chambers can be used to set temperature rigorously, at values usually >100°C, and humidity values, usually above 85%. In this chamber, pressure is enhanced to elevate the stress rate on the components. The latest HAST systems have real-time monitoring of the behavior of devices, including electrical performance and degradation indicators, allowing the diagnosis of possible points of failure.
Strengths
The main strength of HAST testing is the acceleration of stress conditions with compression of time to predict long-term reliability. Such accelerated testing also allows for a quick return on feedback during the development phase, thus accelerating the time-to-market of high-reliability devices. HAST is also very effective at providing insight into problems associated with humidity and corrosion, which are typical failure modes in most electronic components.
Limitations
Although HAST is a very useful test for some classes of failures, the method is not without some limitations. There are types of failures that may not be sensitive to high humidity and temperature. For example, material defects caused by mechanical stress or low-temperature performance problems cannot be determined simply by using a HAST. In addition, the HAST is not applicable to materials that degrade rapidly due to such extreme conditions, without simulating any practical usage.
Related Techniques to HAST Testing Services
Thermal Cycling Tests evaluate the durability in terms of the component life under temperature fluctuations, the related technique to HAST.
