Dissertation
FRACTURE OF LEAD-FREE SOLDER JOINTS FOR ELECTRONIC APPLICATIONS: EFFECTS OF MATERIAL, PROCESSING AND LOADING CONDITIONS
Doctor of Philosophy (PhD), Washington State University
01/2013
Handle:
https://hdl.handle.net/2376/4709
Abstract
During service, micro-cracks form inside solder joints making a microelectronic package highly prone to failure during a drop. Hence, the fracture behavior of solder joints under drop conditions at high strain rates and under mixed mode conditions is a critically important design consideration for robust joints. This study reports the effects of (a) loading conditions (strain rate and loading angle), (b) reflow parameters (dwell time and cooling rate), and (c) post-reflow aging on the mixed mode fracture toughness of lead-free solder joints. A methodology based on the calculation of critical energy release rate, GC, using compact mixed-mode (CMM) samples was developed to quantify the fracture toughness of the joints under conditions of adhesive (i.e., interface-related) fracture. In general, the parameters which result in thicker IMCs layers and harder solder affect GC adversely. The sensitivity of the fracture toughness to all of the aforementioned parameters reduced with an increase in the mode-mixity. A methodology to construct Fracture Mechanism Maps (FMM) for Sn-3.8%Ag-0.7%Cu (SAC387) solder joints has been developed. Such map is plotted in a space described by two microstructure-dependent parameters, with the abscissa describing the interfacial intermetallic compound (IMC), and the ordinate representing the strain-rate dependent solder yield strength. Line contours of constant fracture toughness values, as well as constant fraction of each of the above mechanisms are indicated on the plots. The plots are generated by experimentally quantifying the dependence of the operative fracture mechanism(s) on the two microstructure-dependent parameters (IMC geometry and solder yield strength) as functions of the strain rate, reflow parameters, and post-reflow aging. Nominally Mode I Fracture Mechanism Maps (loading angle 0o) are developed for SAC387/Cu joints w/ and w/o surface finish, Electroless nickel immersion gold (ENIG); equi-mixed mode loading conditions (loading angle 45o) is also presented for SAC387/Cu joints (w/o ENIG). The maps allow rapid assessment of the operative fracture mechanism(s) as well as fracture toughness values for a given loading condition (strain rate and loading angle) and joint microstructure without conducting actual tests, and may serve as both predictive and microstructure-design tools.
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Details
- Title
- FRACTURE OF LEAD-FREE SOLDER JOINTS FOR ELECTRONIC APPLICATIONS: EFFECTS OF MATERIAL, PROCESSING AND LOADING CONDITIONS
- Creators
- Zhe Huang
- Contributors
- Indranath Dutta (Advisor)David Field (Committee Member)Hussein Zbib (Committee Member)William Cofer (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Mechanical and Materials Engineering, School of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 125
- Identifiers
- 99900581746201842
- Language
- English
- Resource Type
- Dissertation