As demand for electronic components, especially semiconductors, continues to grow rapidly, one of the challenges the industry faces, is the time taken to test those components. Traditionally, Temperature Humidity Bias testing, THB for short, has been the solution, but with that taking 1000 hours to complete it represented a significant delay, and this is where HAST testing, Highly Accelerated Temperature and Humidity Stress Test, offers significant advantages.

Taking between 96 and 100 hours per test, and often even less, the HAST test provides significant time savings that can have significant impact on business, and so has quickly become the most dominant of the endurance test methods for semiconductor devices. While primarily connected with semiconductor testing, HAST testing is used on a variety of both hermetically sealed and unsealed compact electronic components to provide fast testing results for a variety of situations and needs.

HAST testing standards

Time Is not the only difference, THB testing holds 85°C/85% R.h. condition as the samples are subjected to bias loads, however this has become less relevant today due to advances in the materials used in packaging and passivation.

By contrast, HAST test conditions use a high temperature of at least 100°C and usually around 105°C along with high relative humidity of around 85% in combination with high atmospheric pressure of up to 4 atmospheres. There is also a saturated version of the HAST test that uses 121°C temperature and relative humidity of 100%. If components are tested with power on, it is usually the unsaturated version with 85%RH. These environmental parameters provide an accelerated method of component reliability testing that quickly finds concealed defects that could result in failure during long-term use.

There are several standards for HAST tests from the IEC, JESD, JIS and JEITA, all indicate different combinations of temperature and RH, and are used for different situations. The most common are:


  • IEC 60068-2-66 – used in non-hermetically sealed, compact electronic components
  • IEC 60749-4 – Mainly used for semiconductors
  • JESD020C – Reflow soldering
  • JESD22-A104DTemperature Cycling testing to cover component and solder interconnection testing
  • JESD22-B102E – Tests for accelerated moisture resistance, unbiased autoclave
  • JESD22-A108BHigh Temperature Operating Life (HTOL) test
  • JESD22-A102C – Used for accelerated humidity resistance testing of non-hermetically sealed semiconductor-based devices
  • JESD22-A110C – Used for non-hermetically sealed semiconductor-based devices while powered to evaluate reliability
  • JESD22-A118 – Evaluates the reliability of unpowered non-hermetically sealed semiconductor-based devices
  • JIS C60068-2-66 – For testing compact electronic components
  • JEITA ED-4701/100 Method 103Tests the durability of semiconductors that are stored or used within high temperature and humidity-based atmospheres


Hast testing in practice

The Hast highly accelerated stress test uses dedicated design test chambers that are rapidly being deployed to replace existing THB testing chambers that use wet bulb/dry bulb mechanisms to control humidity accurately and consistently. That constant temperature/humidity chamber under high pressure is key to delivering faster results in all conditions.

HAST testing is particularly useful during product changes where adjustments could potentially accelerate metal corrosion, with results being obtainable so much faster than alternatives and as a result having a significant impact on development times. HAST testing is the best option for testing for any kind of moisture driven corrosion, with its testing capabilities providing shock accelerated conditions that provide a true test of components.

The ability to provide full tests of all components, evaluating insulation deterioration, overall performance including the performance of plastic sealed components in a variety of conditions, including through a vibration test, the HAST approach delivers the true shock test that gives a real insight into overall performance of the product.



With its flexibility and intensity providing a variety of test results in a short space of time, HAST testing is well positioned for the modern production cycle. Crucially, the HAST testing process allows both saturated and unsaturated testing of components within the test cycle, and for plastic sealed components or others designed to be environmentally sealed, it provides a more streamlined, more effective outcome that enhances product development processes considerably.

Whatever testing standards are used, the ability to have tests completed in days, rather than months creates new opportunities for product development. By powering the agile testing process organizations are able to deliver faster responses to changing production needs, improving performance and delivering increased user satisfaction.