Walter Dauksher

A Second-Level SAC Solder-Joint Fatigue-Life Prediction Methodology

An acceleration model is developed for relating existing second-level fatigue-life data of tin-silver-copper solder joints to untested environments. The acceleration model retains the familiar canonical form of the Norris-Landzberg equation. Model parameters are obtained through calibration with an extensive set of published empirical data. The model will find use in making rapid assessments of a products potential solder-joint field life based on accelerated product tests.

Geometry Effects on the Electromigration of Eutectic SN/PB Flip-Chip Solder Bumps

This work investigates the effect of passivation opening diameter and underbump metallization (UBM) diameter on the electromigration (EM) resistance of Sn/Pb eutectic solder bumps. For the bump geometries studied, the electromigration lifetime depends strongly on the UBM area but weakly on the passivation opening area. The applicability of Blacks model for extrapolating lifetime from accelerated currents to operating currents is investigated. The thermal activation energy, EA, is approximately 1.0 eV and the current density exponent, n, is approximately 2.0. While Blacks model for current density acceleration appears to apply, the current density exponent may not be transferable between bumps of different geometries. A physical model of voiding within the bump using finite element analysis is proposed to explain the observed results

Analysis of Micromachined Piezoelectric Transducers Operating in a Flexural Mode

Micromachined acoustic transducers have recently emerged in multiple application domains. Bulk acoustic resonators, for example, are extensively used as filters in the cellular handset industry. As another example, silicon capacitive microphones are rapidly replacing electret-condenser devices in consumer electronics platforms. Piezoelectric materials are commonly used in acoustic sensing applications. Combining micromaching with piezoelectric thin-films opens up possibilities of multiple new applications, in addition to the miniaturization of existing sensors. Applications may be as diverse as nondestructive test, acoustic imaging, vibration sensing, acceleration/force sensing, or electroacoustics. This paper presents analysis and measured behavior of micromachined devices constructed as a molybdenum, aluminum nitride, molybdenum trilayer and operating in a flexural mode. A theoretical analysis is derived using thin-plate bending theory. Finite-element simulation results of plate dynamics are examined, and sensitivities and linearity of manufactured devices are shown.Copyright

A Finite-Element-Based Methodology for Evaluating Solder Electromigration Current Limits of Sn/Pb Eutectic Solder Bumps

This paper investigates the effect of current distribution to the bump and current crowding on the electromigration (EM) of Sn/Pb eutectic solder bumps. The peak current density in the bump is found to have a significant effect on the EM lifetime of the tested structures and, thus, impacts the maximum allowable bump current. A finite-element model is developed which accurately predicts the maximum allowable bump current as a function of the current crowding. This model makes it possible to predict the maximum bump current for a new current-distribution scheme based on results from EM tests on an existing current- distribution scheme.