It’s a given that everything man-made can potentially fail at some point during its useful lifetime. Designers and users of equipment would very much like to predict how long something is likely to last, how frequently failures can be expected, and what application conditions can lead to excessive failure rates.
One traditional measure of reliability is MTTF or Mean Time To Failure. In the case of electronics, it’s a calculated number based on the failure rates of individual electronic components that make up the complete assembly.
There’s a growing trend toward determining reliability through physical testing. One such method is called HALT or Highly Accelerated Life Test. The goal of HALT is to subject electronic products to extreme conditions that will induce premature aging and stress to uncover weaknesses in the design or components. These weaknesses can then be designed out of the product during product development, before they ever reach the end-user application.
HALT is a destructive test. An electronic product is subjected to ever-increasing environmental stresses until it fails, because the primary goal of the testing is to cause failure. The primary stress factors are high temperature, low temperature, rapid thermal cycling, shock, and vibration. HALT programs can be designed that combine various levels of these stress factors, exceeding standard specifications and expected application conditions until failure occurs.
Products designed and refined using the HALT methodology stand a better chance of achieving expectations for highly reliable operation than products which have not been subjected to a rigorous test-to-failure product development program. The HALT methodology can help define maximum upper and lower operating limits that go beyond standard specifications, as well as upper and lower destruct limits that reveal the ultimate breaking point of a device.
