What it is

The Espec EHS series are Highly Accelerated Stress Test (HAST) chambers for humidity-resistance evaluation of electronic components and semiconductors under elevated temperature, humidity, and pressure. By running humidity testing above 100 °C under pressure, HAST dramatically shortens the classic 85 °C / 85% RH humidity-resistance test, which can otherwise run 1,000 to 3,000 hours. EHS chambers use a single-vessel design in which humidity is generated naturally inside the pressure vessel, a magnetic-couple fan with no shaft penetrating the vessel, and wet-bulb humidity measurement for accuracy. They are freestanding, with built-in supply and waste-water tanks.

• Highly Accelerated Stress Test (HAST) for semiconductor and component humidity resistance
• Temperature (wet-bulb, saturated) control to +142.9 °C or +162.2 °C by model
• Pressure to 0.196 MPa(G) or 0.392 MPa(G) by model
• Three M-type control modes: wet-bulb (saturated), unsaturated, and wet-saturated
• Single-vessel design — humidity generated naturally inside the vessel
• Magnetic-couple fan — no moving shaft through the pressure vessel
• Wet-bulb humidity measurement; freestanding with built-in water tanks
• Air-HAST option for improved oxidation of devices under test
• Conforms to IEC 60068-2-66 (HAST for electronic components)

What it is used for

HAST chambers compress long-duration humidity-resistance programs:

• Humidity-resistance evaluation — accelerated testing of electronic components and semiconductors
• Bias (biased-HAST) testing — humidity testing with an applied voltage and signal
• 85/85 acceleration — shortening long 85 °C / 85% RH humidity-resistance tests
• Whisker humidity-resistance evaluation — accelerated whisker-growth testing
• Package and moisture-ingress reliability — high-throughput reliability screening

Control modes (M-type)

Wet-bulb (saturated) temperature control. Steam is generated by raising temperature; testing runs saturated once chamber pressure reaches 0.010 MPa(G).

Unsaturated control. Humidifying-water temperature is controlled independently of chamber temperature to set an unsaturated humidity condition.

Wet-saturated control. Combined control for wet-saturated conditions.

Key features

Single-vessel design. Humidity is generated naturally inside the chamber, simplifying the system and improving reliability of heat-up and cool-down without pressure or moisture issues.

Magnetic-couple fan. Airflow is driven without a shaft penetrating the pressure vessel, eliminating a common leak and maintenance point.

Wet-bulb measurement. Provides more accurate humidity readings, especially when the chamber is not under pressure.

Freestanding and self-contained. Built-in supply and waste-water tanks; pressure, temperature, and humidity are shown on screen and can be read over Ethernet.

Air-HAST option. Adds air pressure to approximately 130 kPa for improved oxidation of devices under test.

Why engineers pick it

Dramatically shorter humidity-resistance tests. HAST above 100 °C under pressure compresses 1,000 to 3,000-hour 85/85 tests into far shorter runs.

A cleaner, more reliable pressure design. Single-vessel construction and a magnetic-couple fan remove leak and maintenance points found in other approaches.

Accurate humidity control. Wet-bulb measurement and three M-type control modes cover saturated, unsaturated, and wet-saturated testing on one chamber.

Standards-based. Conforms to IEC 60068-2-66 for electronic-component HAST.

Configuring and ordering

Choose the model for your test-area size and pressure range: EHS-212, EHS-222, or EHS-412 in M or deeper MD versions, or the larger EHS-432M and EHS-432M-L. Note that the EHS-412 is the higher-pressure model, reaching 0.392 MPa(G) and +162.2 °C where the 212 and 222 reach 0.196 MPa(G) and +142.9 °C, and that the MD versions add test-area depth at the cost of a taller, deeper chamber footprint.

Add the Air-HAST option if oxidation of devices under test is required. Per-model temperature, pressure, and dimension data are in the Specifications tab. Select your configuration on this page. For biased-HAST fixturing, Air-HAST, or facility water and drain planning, contact W5 Engineering and we will configure and quote it with you.