Design for Reliability

Chapter 11

Highly Accelerated Life Testing

Louis J. Gullo

Introduction

Highly accelerated life testing (HALT) is a method used for rapid acceleration of the precipitation and detection of failure mechanisms, latent manufacturing defects, and design weaknesses over time. The failure acceleration occurs through the application of a combination of environmental and electrical stress conditions, such as temperature, vibration, humidity, power, and voltage. HALT and highly accelerated stress testing (HAST) apply accelerated stresses that are applied nonuniformly in varying stress combinations, called step stresses, and various environmental conditions, called load case conditions.

Gregg Hobbs, who pioneered the HALT process and coined the term HALT, states: “In HALT, every stimulus of potential value is used under accelerated test conditions during the design phase of product in order to find the weak links in the design and fabrication processes. Each weak link found provides an opportunity to improve the design or the processes, which will lead to reduced design time, increased reliability, and decreased cost” [1].

Traditional reliability tests such as accelerated reliability testing (ART) and accelerated life testing (ALT) use environmental stresses applied uniformly and consistently to expose failures and to develop acceleration factors to equate the stresses applied in a test to reliability or to life in the actual customer use environment. With HALT, acceleration factors are difficult ...