SMTA International Conference Proceedings


A COMPONENT LEVEL PREDICTIVE RELIABILITY MODELING METHODOLOGY

Authors: Jennifer V. Muncy and Daniel F. Baldwin
Company: Georgia Institute of Tech
Date Published: 9/26/2004   Conference: SMTA International


Abstract: To determine the reliability performance of electronic components, environmental stress tests, or accelerated life tests, are used to apply stresses to electronic packages that exceed the stress levels experienced in the field. In theory, these elevated stress levels are used to generate the same failure mechanisms that are found in the field, only at an accelerated rate. Therefore, an acceleration factor is typically used to correlate (extrapolate) the accelerated life testing data to a field failure rate for a specified use condition. Often times this data is time consuming and expensive to obtain, hence a need exists for reducing the time to data for electronic components in reliability testing.

A methodology is presented in this paper whereby existing reliability data can be leveraged to obtain ‘correction functions’ which can be used to modify a mean time to failure, MTTF, that was calculated analytically. A suggested analytical model will be presented in addition to the statistics based methodology that can be used to obtain correction functions. The correction factor approach is very similar to approach used for modifying fatigue strengths in engineering alloys. The concept of attaching correction functions to an unmodified variable is not new, fatigue strengths or endurance limits are modified to account for physical differences between the actual parts in use and the parts that were used to obtain the fatigue data.

Types of correction functions for steels include those for differences in loading conditions, temperature differences, and surface finish; correction functions for flip chip on board assemblies would be the glass transition temperature of the underfill, an area ratio for the solder joint, and the bond bad substrate metallization.



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