DEMONSTRATING RELIABILITY WITH ACCELERATED TESTING

by Mr. Larry Edson, BSME, CQE

This class uses extensive real life examples to teach the practical “How To” of the most efficient accelerated test methods available today. This class builds upon the concepts developed in the pre-requisite class, HALT & HASS + Workshop.

This class will provide the student with all of the skills necessary to demonstrate reliability requirements using accelerated test methods. The class includes the necessary knowledge of statistics and the "physics of failure" as these are essential in developing correctly correlated accelerated tests. The class will focus on accelerated test design that employs increased stress levels. This approach has tremendous advantage in reducing test time, sample size, and test facility resources. The methodologies taught are applicable to all types of stresses spanning the electrical, mechanical, pneumatic, and hydraulic worlds. Reliability statistics and the "physics of how things fail" for mechanical and electrical devices is covered in detail. Additionally, the failure mechanisms and unique physical properties of lead-free solder are also covered.

This class uses extensive real life examples to teach the practical "How To" of the most efficient accelerated test methods available today. Accelerated test methods for mechanical and electrical devices will be explained and practiced in class following an explanation of the sciences that support their use. Class time is organized by failure mechanism. The physics of each failure mechanism is explained, both at a science level and at a practical level. The major Stress-Life models that apply to each of the failure mechanisms will be explained through example in class. The majority of the class time will be spent learning exactly how to apply the accelerated test methods and their associated Stress-Life models to common test requirements. Class exercises along with videos of products being tested will reinforce all concepts taught. Explanation of the underlying concept of Stress-Strength-Interference will form the foundation for tying it all together.

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Statistical methods begin with understanding the need to design requirements around the severe user and how the severe user is quantified. The Analysis-Qualitative-Quantitative strategy is explained showing how analysis is combined with HALT, which is combined with quantitative testing. This combination forms a system that will rapidly develop product maturity while also demonstrating the required level of reliability actually exists. Students will learn how to produce Weibull plots to determine product reliability. Success-run testing statistics along with multiple life over-testing will be used on many in-class examples. Sudden death testing will also be explained in class.

The CALT method, which uses a process of extrapolation to normal stress from the outcome of increased stress tests, represents one of the most versatile and efficient accelerated test methodologies available. This method will be shown and explained through numerous examples. Degradation Analysis for wear will be explained and demonstrated through a video example. The CALT-MEOST method will be explained through a worked example in class. The CALT-MEOST method allows us to evaluate the effects of many stresses combined together. We can combine as many stresses as we want while still only testing six samples to failure. This method results in a Weibull plot allowing us to demonstrate a reliability requirement.

Failure mechanisms are explained in detail along with the established acceleration factors for each. A comprehensive understanding of failure mechanisms forms the foundation for good reliability test strategies. The problems and advantages of using lead-free solder are explained, along with the unique failure mechanisms associated with this material.

ADVANCED APPLICATIONS IN ACCELERATED TESTING

This former 1-day class has been incorporated into Demonstrating Reliability with Accelerated Reliability by adding a third day. This section is designed to develop a competent and comfortable working knowledge of accelerated test methods and builds upon the statistical and failure physics concepts. Sample problems covering electronics, hydraulic, pneumatic, and mechanical systems will be worked in class to develop a true competency in the attending student. Expanded attention to Test-Flows for electrical, mechanical and mechatronic products will be developed in class. Students are encouraged to offer up problems stemming from their own work situations as opportunity for collective class resolution.