Accelerated Stress Testing

Accelerated Stress Test (AST) Chambers accelerate product failures and fatigue by applying high levels of stress to products to reveal design defects. Utilizing extreme temperature change rates in excess of 70°C per minute and repetitive shock multi-axis vibration with acceleration over 50 g's, product design and operating limits can be established in just hours, rather than years. Organizations use AST to improve product reliability, reduce product development time and lower costs associated with production, warranty and field-related failures.

Thermotron AST systems are able to perform various accelerated stress test methods such as Highly Accelerated Life Test (HALT), Highly Accelerated Stress Screen (HASS), Step Stress Testing among others. Each type of stress precipitates specific defects that might be missed by traditional testing methods and equipment.

• HALT Testing uses step-by-step cycling of environmental variables such as temperature, shock and vibration in order to force products to fail. It can also include the simultaneous cycling of multiple environmental variables (an example: aggressive temperature cycling and step-stress vibration testing) providing a closer approximation of real-world operating environments. Used as part of the product design process using prototypes, HALT quickly exposes product weaknesses allowing for improved product quality. HALT testing is performed multiple times after the weak components have been fixed, replaced or reinforced.



• HASS Testing applies similar stresses to those used in HALT however, HASS is an on-going screening test, performed on regular production units. This type of testing aims to verify that actual production units continue to operate properly and quickly detects component or manufacturing irregularities.. Environmental variables such as fast temperature cycling, shock and multi-axis vibration as a means of screening 100% of production units may be used. HASS Testing indicates that the entire final product, including all components, will be reliable.

There are important factors to take into consideration when choosing appropriate equipment for HALT and/or HASS testing. Both of these testing methods require testing equipment capable of producing temperature and vibration simulatenously. Thermotron is able to provide powerful HALT/HASS performing Accelerated Stress Test (AST) Chambers in a variety of sizes and utilizing several different methods of cooling for the highest temperature change rates.

The liquid nitrogen cooled chambers feature a high volume, adjustable air distribution system capable of pinpointing rapid airflow directly over the product. A large door located near the controller provides access to the chamber workspace and facilitates convenient product attachment and interconnect. Utilizing several sizes of repetitive shock vibration tables with durable, Teflon-coated impactors to last longer and reduce maintenance downtime, Thermotron's AST chambers allow impactor configuration to achieve the required vibration performance characteristics. Thermotron repetitive shock shakers incorporate a unique thermal isolation system designed to minimize thermal loading on the chamber and provide a stable condition for impactor operation.

Mechanically refrigerated AST Chambers that reduce or eliminate the necessity for liquid nitrogen and dramatically reduce the cost of operations are also available. For more information about Mechanically Cooled Alternatives for Accelerated Stress Testing see our presentation.

For customers that desire AST airflow and performance but have a large, cumbersome product unable to fit inside traditional AST Chambers, Thermotron has created FAST chambers. Utilizing a slide-out shaker, product loading has been made easy and expanded sizes up to 80 cubic feet allow for combined testing of large products.

Because all types of accelerated stress testing require that the product be continuously monitored while stresses are applied, Thermotron's Product Test Solutions group can provide hardware and software solutions to stimulate and monitor multiple product parameters, detect failures and collect pertinent information for proper failure mode analysis.

Our PC-based AST-8800 control system has been designed specifically for extreme change rate chambers and repetitive shock vibration systems. It features a 17-inch flat panel monitor that displays power spectral density, temperature and acceleration data all on easy-to-read screens. Ethernet-compatible and web-enabled with an internet-ready front end for virtual anytime/anywhere access.

Accelerated Stress Test (AST) Chambers
Model Number	Workspace Dimensions (WxDxH)	Temperature Range	Approximate Change Rate*
AST-8	24" x 22" x 24" (61cm x 56cm x 61cm	-100°C to +200°C (-148°F to +392°F)	Greater than 50°C per minute
AST-18	33" x 34" x 30" (84cm x 86cm x 76cm)	-100°C to +200°C (-148°F to +392°F)	Greater than 50°C per minute
AST-20R	30" x 30" x 40" (76cm x 76cm x 101cm)	-73°C to +200°C (-100°F to +392°F)	Greater than 50°C per minute
AST-30	42" x 42" x 35" (106cm x 106cm x 88cm)	-100°C to +200°C (-148°F to +392°F)	Greater than 50°C per minute
AST-35	42" x 42" x 40" (106cm x 106cm x 101cm)	-100°C to +200°C (-148°F to +392°F)	Greater than 70°C per minute
AST-70	54" x 56" x 40" (137cm x 142cm x 101cm)	-100°C to +200°C (-148°F to +392°F)	Greater than 70°C per minute

* Dependent on range and chamber loading.