What is the HAST Test?

As demand for electronic components, especially semiconductors, continues to grow rapidly, one of the challenges the industry faces is working to address the time required to test these components.

One of the most popular tests is the Bias (THB for short), which involves applying humidity and temperature stress to the sample; it's a very effective solution, but it requires over 1,000 hours of testing to complete.

For this very reason, another type of test was created: the HAST test, Highly Accelerated Temperature and Humidity Stress Test.

What is the Has Test?

This type of testing offers significant advantages. HAST testing takes between 96 and 100 hours to complete (often even less), resulting in significant time savings and a positive impact on business.

Because of this characteristic, HAST testing has quickly become the most widespread and popular endurance testing method for semiconductor devices. Although primarily related to semiconductor testing, HAST testing is used on a variety of compact, hermetically sealed and unsealed electronic components to provide rapid test results for a variety of situations and needs.

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The HAST test standards

Time isn't the only factor that impacts the test: for example, the THB test must be set to 85°C and 85% Rh, respectively, where the samples are subjected to polarization loads. However, this has become less relevant today, due to advances in packaging and passivation materials.

Alternatively, HAST test conditions use an elevated temperature of at least 100°C—typically around 105°C—along with arelative humidity of around 85%, combined with high atmospheric pressure, up to 4 atmospheres. There is also a saturated version of HAST testing that uses a temperature of 121°C and 100% relative humidity. If components are being tested in operation, testing is typically performed at 85% relative humidity. These environmental parametersprovide an accelerated method of verifying component reliability, quickly finding hidden defects that could cause failure during long-term use.

There are several standards for HAST testing, including IEC, JESD, JIS, and JEITA. They all specify different combinations of temperature and RH and are used for different situations. The most common are:

• IEC 60068-2-66 – Used for non-hermetically sealed compact electronic components
• IEC 60749-4 – Mainly used for semiconductors
• JESD020C – Used to perform solder heating resistance tests
• JESD22-A104D – Cyclic temperature testing to cover component and solder interconnection testing
• J-STD-002D – Accelerated Moisture Resistance Test , Autoclave , Undistorted
• JESD22-A108B – High Temperature Test (HTOL)
• JESD22-A102C – Used to test the accelerated humidity resistance of non-hermetically sealed semiconductor devices
• JESD22-A110C – Used for non-hermetically sealed semiconductor devices, while powering on, to evaluate their reliability
• JESD22-A118 – Evaluates the reliability of non-hermetically sealed semiconductor power devices
• JIS C60068-2-66 – Used for testing compact electronic components
• Method ED-4701/100 103 – Tests the durability of semiconductors that are stored or used within a high temperature and humidity atmosphere

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How to perform the HAST test with a test chamber

High Acceleration Stress Testing , abbreviated to HAST , is performed with dedicated test chambers designed to meet all the requirements of the same.

As previously mentioned, these chambers are used to replace existing THB test chambers, which use wet-bulb/dry-bulb mechanisms to control humidity. 

The climatic chamber, which controls temperature, humidity and pressure, is essential to provide faster results in all conditions.

HAST testing is particularly useful during product modifications where adjustments could potentially accelerate metal corrosion , with results achievable much more quickly than alternatives and, consequently, significantly impacting development times. HAST testing is the best option for testing for any type of moisture- induced corrosion  .

It also provides comprehensive test results of all components subject to deterioration, overall performance, including the performance of plastic-sealed components under a variety of conditions, including vibration testing. The HAST approach provides true shock testing, which provides a comprehensive view of product performance.

Conclusion

With its flexibility and ability to provide a variety of test results in a short amount of time,HAST testing is indispensable for modern production cycles. Essentially, the HAST testing process allows for both saturated and unsaturated testing of components within the test cycle, for components sealed in plastic or other components designed to be environmentally sealed. 

It provides a more streamlined and effective outcome, which significantly improves product development processes. Regardless of the testing standards used, the ability to perform tests in days, rather than months, creates new opportunities for product development. This streamlines the testing process, resulting in faster responses to changing production needs, improved performance, and increased user satisfaction.

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Reference Standards

• IEC 60068-2-66 — Environmental testing – Part 2-66: Tests – Test Cx: Damp heat, steady state (unsaturated pressurized vapor). European reference for HAST on non-hermetically sealed electronic components.
• IEC 60749-4 — Semiconductor devices – Mechanical and climatic test methods – Part 4: Damp heat, steady state, highly accelerated stress test (HAST).
• JEDEC JESD22-A110E — Highly Accelerated Temperature and Humidity Stress Test (HAST). JEDEC standard for non-hermetic devices under bias.
• JEDEC JESD22-A118B — Accelerated Moisture Resistance – Unbiased HAST for non-biased devices.
• IPC J-STD-020E — Moisture/Reflow Sensitivity Classification for Nonhermetic Surface Mount Devices, reference for MSL (Moisture Sensitivity Level).
• JESD22-A102D — Accelerated Moisture Resistance – Unbiased Autoclave (121 °C, 100% RH, 2 atm), “saturated” version of the test.
• JIS C 60068-2-66 — Japanese implementation of the IEC standard for HAST.

Authoritative Sources

• JEDEC Solid State Technology Association. American organization that publishes the JESD22 Series A standards on semiconductor reliability testing.
• IEC – International Electrotechnical Commission. International electrotechnical standards body, responsible for the IEC 60068 series for environmental testing.
• IPC – Association of Connecting Electronics Industries. Publishes J-STD-020 and MSL guidelines for the PCB assembly industry.
• Automotive Electronics Council (AEC)issues AEC-Q100/Q101/Q104 which calls for HAST as a mandatory qualification test.

Frequently Asked Questions about the HAST Test

What is the practical difference between biased and unbiased HAST?

Biased HAST ( JESD22-A110) applies a bias voltage to the device during exposure to 130°C/85% RH or 110°C/85% RH, simulating real-world operating conditions. The combination of electric field, humidity, and temperature accelerates failure mechanisms such as ion electromigration, bonding wire corrosion, and passivation degradation. Unbiased HAST (JESD22-A118) excludes bias and is designed to evaluate moisture ingress through plastic packages, delamination, and corrosion in the absence of bias. Typical duration is 96 hours at 130°C/85% RH or 264 hours at 110°C/85% RH , with the choice dependent on the required severity. Both methods are followed by functional tests to derive the fallout rate.

Why does HAST use higher-than-atmospheric pressure?

The temperature combination ≥ 100 °C + 85% RH requires an internal pressure greater than 1 atm, otherwise the dew point would not be reached in the vapor phase. At 130 °C with 85% RH , the partial vapor pressure corresponds to approximately 2.3 bar absolute (with total pressure ≈ 2.7 bar). The HAST chamber is built as a PED-certified pressure vessel (Directive 2014/68/EU) with a stainless steel autoclave, safety valves, and redundant pressure sensors. Control occurs via a thermodynamic model that simultaneously regulates temperature, pressure, and deionized water injection. Typical accuracy is ± 0.5 °C for temperature and ± 3% for RH, with useful volume mapping compliant with IEC 60068-3-5.

Which MSL level requires a HAST and which autoclave?

The Moisture Sensitivity Level (MSL) according to IPC/JEDEC J-STD-020 establishes how sensitive a non-hermetic SMT component is to moisture before reflow. MSLs 1-6 are determined by preconditioning in a climate chamber followed by three reflow cycles at 260°C: a component that survives 168 hours at 85°C/85% RH is MSL 2; 696 hours are required for MSL 2a. HAST (130°C/85% RH for 96 hours) is not used to determine MSL but as a reliability qualification test to evaluate corrosion and delamination. The JESD22-A102 autoclave test (121°C, 100% RH, 2 atm, 96-168 hours) is a more severe alternative method for moisture ingress but is less widely used in favor of HAST due to the shorter exposure time required.

How to qualify a HAST chamber according to AEC-Q100?

AEC-Q100 recalls JESD22-A110 for Grade 1 and Grade 0 with conditions of 130 °C/85% RH for 96 hours (Grade 1) and 264 hours at 110 °C/85% RH for under-hood applications. The chamber qualification includes: metrological traceability of the T and RH (ACCREDIA certified, uncertainty ≤ 0.3 °C and ≤ 1.5% RH); 9-point useful volume mapping according to IEC 60068-3-5; pressure verification with a Class 0.6 reference pressure gauge; overtemperature and dry-out tests. The IQ/OQ/PQ documentation must be accompanied by 21 CFR Part 11 records for audit trail, continuous T/RH/P recording with frequency ≥ 1 Hz and multi-threshold alarms. Calibration must be repeated at least annually or after each intervention on the pressurized circuit.