A highly accelerated life test (HALT) is a

stress testing Stress testing (sometimes called torture testing) is a form of deliberately intense or thorough testing used to determine the stability of a given system, critical infrastructure or entity. It involves testing beyond normal operational capacity, ...

methodology In its most common sense, methodology is the study of research methods. However, the term can also refer to the methods themselves or to the philosophical discussion of associated background assumptions. A method is a structured procedure for bri ...

for enhancing product

reliability Reliability, reliable, or unreliable may refer to: Science, technology, and mathematics Computing * Data reliability (disambiguation), a property of some disk arrays in computer storage * High availability * Reliability (computer networking), a ...

in which prototypes are stressed to a much higher degree than expected from actual use in order to identify weaknesses in the design or manufacture of the product.

Manufacturing Manufacturing is the creation or production of goods with the help of equipment, labor, machines, tools, and chemical or biological processing or formulation. It is the essence of secondary sector of the economy. The term may refer to a r ...

and

research and development Research and development (R&D or R+D), known in Europe as research and technological development (RTD), is the set of innovative activities undertaken by corporations or governments in developing new services or products, and improving existi ...

organizations in the electronics, computer, medical, and military industries use HALT to improve product reliability. HALT can be effectively used multiple times over a product's life time. During product development, it can find design weakness earlier in the

product lifecycle In industry, Product Lifecycle Management (PLM) is the process of managing the entire lifecycle of a product from its inception through the engineering, design and manufacture, as well as the service and disposal of manufactured products. PL ...

when changes are much less costly to make. By finding weaknesses and making changes early, HALT can lower product development costs and compress

time to market In commerce, time to market (TTM) is the length of time it takes from a product being conceived until its being available for sale. The reason that time to market is so important is since being late erodes the addressable market into which prod ...

. When HALT is used at the time a product is being introduced into the market, it can expose problems caused by new manufacturing processes. When used after a product has been introduced into the market, HALT can be used to audit product reliability caused by changes in components, manufacturing processes, suppliers, etc.

Overview

Highly accelerated life testing (HALT) techniques are important in uncovering many of the weak links of a new product. These discovery tests rapidly find weaknesses using accelerated stress conditions. The goal of HALT is to proactively find weaknesses and fix them, thereby increasing product reliability. Because of its accelerated nature, HALT is typically faster and less expensive than traditional testing techniques. HALT is a test technique called test-to-fail, where a product is tested until failure. HALT does not help to determine or demonstrate the reliability value or failure probability in field. Many accelerated life tests are test-to-pass, meaning they are used to demonstrate the product life or reliability. It is highly recommended to perform HALT in the initial phases of product development to uncover weak links in a product, so that there is better chance and more time to modify and improve the product. HALT uses several stress factors (decided by a Reliability Test Engineer) and/or the combination of various factors. Commonly used stress factors are temperature, vibration, and humidity for electronics and mechanical products. Other factors can include voltage, current, power cycling and combinations of them.

Typical HALT procedures

Environmental stresses are applied in a HALT procedure, eventually reaching a level significantly beyond that expected during use. The stresses used in HALT are typically hot and cold temperatures, temperature cycles, random vibration, power margining, and power cycling. The product under test is in operation during HALT and is continuously monitored for failures. As stress-induced failures occur, the cause should be determined, and if possible, the problem should be repaired so that the test can continue to find other weaknesses. Output of the HALT gives you: # Multiple failure modes in the product before it is subjected to demonstration testing # Operating limits of the product (upper and lower). These can be compared with a designer's margin or supplier specifications # Destruct limits of the product (limit at which product functionality is lost and no recovery can be made)

Test chambers

A specialized environmental chamber is required for HALT. A suitable chamber also has to be capable of applying pseudo-random vibration with a suitable profile in relation to frequency. The HALT chamber should be capable of applying random vibration energy from 2 to 10,000 Hz in 6

degrees of freedom Degrees of freedom (often abbreviated df or DOF) refers to the number of independent variables or parameters of a thermodynamic system. In various scientific fields, the word "freedom" is used to describe the limits to which physical movement or ...

and temperatures from -100 to +200°C. Sometimes HALT chambers are called repetitive shock chambers because pneumatic air hammers are used to produce vibration. The chamber should also be capable of rapid changes in temperature, 50°C per minute should be considered a minimum rate of change. Usually high power resistive heating elements are used for heating and

liquid nitrogen Liquid nitrogen—LN2—is nitrogen in a liquid state at low temperature. Liquid nitrogen has a boiling point of about . It is produced industrially by fractional distillation of liquid air. It is a colorless, low viscosity liquid that is wide ...

(LN₂) is used for cooling.

Fixtures

Test fixture A test fixture is an environment used to consistently test some item, device, or piece of software. Test fixtures can be found when testing electronics, software and physical devices. Electronics In testing electronic equipment such as circuit ...

s must transmit vibration to the item under test. They must also be open in design or use air circulation to produce rapid temperature change to internal components. Test fixtures can use simple channels to attach the product to the chamber table or more complicated fixtures sometimes are fabricated.

Monitoring and failure analysis

The equipment under test must be monitored so that if the equipment fails under test, the failure is detected. Monitoring is typically performed with

thermocouple A thermocouple, also known as a "thermoelectrical thermometer", is an electrical device consisting of two dissimilar electrical conductors forming an electrical junction. A thermocouple produces a temperature-dependent voltage as a result of the ...

sensors,

vibration Vibration is a mechanical phenomenon whereby oscillations occur about an equilibrium point. The word comes from Latin ''vibrationem'' ("shaking, brandishing"). The oscillations may be periodic function, periodic, such as the motion of a pendulum ...

accelerometer An accelerometer is a tool that measures proper acceleration. Proper acceleration is the acceleration (the rate of change of velocity) of a body in its own instantaneous rest frame; this is different from coordinate acceleration, which is accele ...

multimeter A multimeter is a measuring instrument that can measure multiple electrical properties. A typical multimeter can measure voltage, resistance, and current, in which case it is also known as a volt-ohm-milliammeter (VOM), as the unit is equipped w ...

s and data loggers. Common causes of failures during HALT are poor product design, workmanship, and poor manufacturing. Failures to individual components such as

resistors A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active el ...

capacitors A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals. The effect of a ...

diode A diode is a two-terminal electronic component that conducts current primarily in one direction (asymmetric conductance); it has low (ideally zero) resistance in one direction, and high (ideally infinite) resistance in the other. A diode ...

printed circuit boards A printed circuit board (PCB; also printed wiring board or PWB) is a medium used in electrical and electronic engineering to connect electronic components to one another in a controlled manner. It takes the form of a laminated sandwich struct ...

occur because of these issues. Failure types found during HALT testing are associated with the infant mortality region of the

bathtub curve The bathtub curve is widely used in reliability engineering and deterioration modeling. It describes a particular form of the hazard function which comprises three parts: *The first part is a decreasing failure rate, known as early failures. *Th ...

Military application

HALT is conducted before qualification testing. By catching failures early, flaws are found earlier in the acceptance process, eliminating repetitive later-stage reviews.

References

External links

Environmental Test Chamber Selector by Application

HALT AND HASS: The Accepted Quality and Reliability Paradigm

What is HALT/HASS Testing?

A Beginners Guide to HALT
Electronic engineering Product testing Environmental testing