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The following study is motivated by the need to capture the elasto-viscoplastic behavior of a “real” industrial power module lead-free solder joint. In this work, we carried out a numerical design of experiments in order to forecast the ability of an experimental bending system to identify the specimen material properties. As a proof of principle, the micro-mechanical elastic behavior of power module...
The A15-type superconductors have been used to fabricate the 10 15-T high-field superconducting magnets. Due to the strain sensitivity of this type of conductors, minimization of the strain in conductors is an important issue to realize the highest critical current density during operation. It is also known that the superconductors in epoxy-impregnated...
Ultrasonic nonlinearity measurements have been suggested as an effective tool for the early detection of fatigue damage in metallic structures. However, the correlation between ultrasonic nonlinearity and material damage induced by fatigue or plastic deformation has been observed to be non-monotonic by several researchers including by our group. To clarify the correlation between microstructure and...
A novel test sample with a micro scale free-standing specimen of Cu-TSV used for uniaxial micro-tensile test is presented in this paper. Design of a deformation-buffer reticular supporting frame of the test sample effectively reduces the deformation of Cu-TSV thin film during clamping operation. The stress resulting from electrodepositon process is minimized by fabricating Cu-TSV thin film on surface-treated...
In order to match high power density and large counts of I/Os with the need for smaller-sized automotive electronic devices and low cost, new solutions have to be developed without any concessions to reliability. The authors describe the so-called i2Board concept, developed by Schweizer Electronic AG and used in the VISA project, funded by the German Government. VISA is an abbreviation and means "fully...
Atomic diffusion in soldering process leads to growth and stress developed in the intermetallic compound layer in solder joints. The stress and morphological evolution of the intermetallic compound layer, which is driven by the stress, result in degradation of mechanical performance of solder joints. Microstructure of the intermetallic compound layer in solder joints is modeled. The model consists...
This study examines evolution characteristics of inelastic strains and materials damage in Sn-4Ag-0.5Cu (SAC405) solder joints of a BGA package under cyclic mechanical stressing. For this purpose, a finite element model of the assembly under four-point bend test set-up is employed. Strain rate-dependent response of the solder is represented by Anand model. Progressive damage in the solder joint is...
Thus far, there is a severe lack of understanding about interfacial fracture and impact behavior of the microscale lead-free solder interconnects. In this study, the finite element simulation and analytical method were used to characterize the interfacial fracture and impact behavior at the interfaces of the microscale Sn-Ag-Cu solder joints. The intersection of a linear microcrack tip upon Sn-Ag-Cu...
The deformation of core board affects the quality of circuit board, like misalignment, during lamination process of MLB (Multilayer Board). Three main factors causing the deformation are discussed, which are the mismatch of CTE (Coefficient of Thermal Expansion) among different materials, the residual stress in core boards and the special properties of the prepreg. Considering properties changing...
Deformation Measurements under thermo-mechanical load are quick and useful tool to increase the reliability of electronic products and to verify Finite Element Models (FEM). Two Examples demonstrate the advanced use.
In this paper, the investigation focuses on the copper stud bump solder joint thermal-mechanical reliability. The copper stud bump processing is simulated by FEM software Ansys/Ls-dyna, and then the relationship between the copper stud bump and processing parameters (bonding force, ultrasonic power, bonding time and bonding temperature) is studied. Based on the simulation result, the dimension of...
The Jedec drop test has become a popular method for the assessment of the dynamic mechanical reliability of 2nd level assemblies. It delivers repeatable results and is thus well suited for the development of a virtual lifetime model based on FEM simulations. Detailed experimental studies showed PCB copper trace fractures as the dominating failure mode. The virtual risk assessment applied a two steps...
Models for crack initiation and propagation in leadfree solders under shock-impact events have been developed using extended finite element method (XFEM). XFEM enables the modeling the solder interconnect without explicitly meshing the crack surface. The crack propagated in crack domain along the solution dependent path with no requirement of re-meshing the model. Interface damage properties of the...
A simulation of the Board Level Drop-Test is performed to evaluate some WL-CSP (Wafer-Level Chip-Scale Packages) performances. An elastic-plastic model is applied on both solder bump and copper pad materials. It intends to demonstrate that copper plasticity is mandatory due to the large plastic strain occuring in these materials. A statistical analysis discusses the required accuracy for the modeling...
Miniaturization and increasing functional integration as the electronic industry drives push the development of feature sizes down to the nanometer range. Moreover, harsh operational conditions and new porous or nano-particle filled materials introduced on both chip and package level - low-k and ultra low-k materials in Back-end of line (BEoL) layers of advanced CMOS technologies, in particular -...
Full density nanocrystalline (NC) Cu with average grain size of 33 nm was prepared through high energy ball milling. Effects of annealing on microhardness and activation volumes (V*) were studied. The magnitude observed for these characteristic deformation parameters is very different from their course-grained (cg) counterpart. The much higher micro-hardness of as-prepared Cu sample of 1.7 GPa was...
This paper presents mining the worst thermal fatigue life of solder joints on chip components used in vehicle electronics. The authors proposed an isothermal fatigue test method using real size solder joints to get the fatigue properties. The Manson-Coffin's law given by this method could improve the agreement between the simulation model and experimental results. Based upon the Manson-Coffin's law...
A strain-controllable dynamic bending method on WLCSP has been proposed in this paper. In order to identify the principle factor among the effects of stiffness attributed by different board level structures, the 0.4 mm pitch WLCSP packages with Sn-4.0Ag-0.5Cu solder ball are used. This combination of WLCSP is considered to have the high stiffness in the structure. It is also shown that there are interactions...
In this paper, the damage fracture of solder joints in board level electronic package subjected to drop impact loadings was numerically simulated by the finite element method and the cohesive zone model. The solder-Cu pad interface was modeled by cohesive zone elements. The results show that fracture initiates at the edge of the PCB side and the damage of solder joint is affected greatly by the used...
The stress of Cu interconnects embedded in advanced ultra-low-k (ULK) dielectrics was studied for different porosities. Interconnects formed a high porosity material result in a lower stress due to relaxation in the plane. This effect is less significant for narrow lines, where in-plane relaxation is reduced by the dense narrow spacing. The stress in isolated lines was found to be independent of dielectric...
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