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As a new product goes through the design and production process, one of the most important steps along the way is to find out how reliable it will be when used in real-world situations. A uniform methodology system has been created that is implemented for a wide range of different products of a variety of sizes, shapes, and components. The standardized stress examination is known as HALT testing, which stands for a Highly Accelerated Life Test. The use of HALT testing works to decrease the likelihood of product failure, thus saving the creator both financial expenses as well as time spent in the design stage. With HALT testing, stress is applied to the product in a number of different forms, most commonly being temperature, temperature cycling, vibration and combining temperature cycling along with vibration simultaneously. The test is performed by first administering a low dosage of the stress and then gradually increasing the levels until a point is found that the product no longer functions or receives significant damage. With the sequential steps of the HALT process, only a small sample of products is needed to complete the test, with many being done using five samples or less. The main goal of these tests is to find out where the limits of operation and failure rates for the product to decide whether it should be put into production or not. HALT and the related HASS testing (Highly Accelerated Stress Screening) methodology takes place in an environmental test chamber that must meet certain accepted requirements. In measuring temperature changes, the chamber must be capable of rising or falling by 45 degrees Celsius every minute or more. High end HALT chambers have recorded temperature changes of 60 degrees Celsius in a single minute. For this type of testing equipment, specialized materials like liquid nitrogen is needed for the desired speed. In addition to temperature, a HALT chamber must also have the ability to perform vibration testing as well. These tests require a combination of temperature and vibration stresses to be applied at the same time. As part of a full test, an entire product is often examined as well as individual components or assemblies of the product.
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