Extended cohesive zone model for simulation of solder/IMC interface cyclic damage process in pb-free solder interconnects
The current formulation of stress- and energy-based cohesive zone model (CZM) is extended to account for load reversals. Cyclic degradation of solder/IMC interface properties, namely penalty stiffness, strengths and critical energy release rates follows power-law functions of fatigue cycles. Per...
| Main Authors: | , , , |
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| Format: | Conference or Workshop Item |
| Language: | English |
| Published: |
2012
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| Subjects: | |
| Online Access: | http://irep.iium.edu.my/39051/ http://irep.iium.edu.my/39051/ http://irep.iium.edu.my/39051/1/IEMT_2012.pdf |
| Summary: | The current formulation of stress- and energy-based cohesive zone model (CZM) is extended to account for load
reversals. Cyclic degradation of solder/IMC interface
properties, namely penalty stiffness, strengths and critical
energy release rates follows power-law functions of fatigue
cycles. Performance of the extended CZM is examined using
finite element (FE) simulation of a single Sn-4Ag-0.5Cu
(SAC405) solder interconnect specimen. Strain ratedependent
response of the solder is represented by unified inelastic strain equations (Anand’s model) with optimized model parameters for SAC405 solders. The 3D FE model of the specimen is subjected to cyclic relative displacement (Δδ
= 0.003 mm, R = 0) so as to induce shear-dominant fatigue
loading. Results show that interface crack initiated at the
leading edge of the solder/IMC interface on the tool side of
the assembly after 22 cycles have elapsed. Bending stress
component induced by the solder stand-off height dominates
the interface damage process. A straight interface crack front is predicted indicating the relatively brittle nature of the SAC405/Cu6Sn5 interface. The extended formulation of the CZM to account for load reversals has demonstrated the
ability to describe the progressive solder/IMC interface
damage process consistent with the mechanics of relatively
brittle interface fracture. |
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