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Warpage is a critical concern in the microelectronics industry for several decades. It is a root cause of failures during manufacturing processes such as open solder joints. Also the excessive warpage generates the delamination and die cracking which degrade the package reliability. Thus, the accurate estimation of package warpage is one of the imp...
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... The solution has been corrected and extended in the prediction of thermal stresses and deformations of the die-substrate assembly [23]. The solution has been further applied to warpage prediction of flip-chip packages and closely compared with finite-element and experimental results [6], [13], [24] and solutions of the classic lamination theory [25]. However, since the package structure is a die-substrate assembly with an extended substrate, with various length-thickness aspect ratios and underfill material properties and thicknesses, a thorough evaluation of this theory for thermally induced warpage (or deformation) of the packages has not been done yet. ...
The control of thermally-induced warpage on electronic packages is an important issue during their fabrication process and assembly. Apart from a commonly-used finite element method and experimental methods for thermally-induced warpage analysis of the packages, it still needs a fundamental theory to provide an insight of mechanics to assist and further check the finite element and experiment-obtained results, especially for critical parameter identification. This study aims to take a close look into the well-known, closed-form Suhir theory for calculating thermally-induced deformation of die-substrate assembly and correlate it with a finite element analysis, and further to propose a new Suhir-solution-based theory for predicting the thermal deformation of flip-chip packages. Through this study, the shear-effect region has been found and its effect on curvature distribution over entire package length and corresponding warpage have been examined in terms of elastic modulus and thickness of underfills. The other parameters such as extended substrate and fillets of underfill are also studied. The limitation and feasibility of the theoretical solution to thermal deformation (warpage) prediction of flip-chip packages are discussed in detail by comparing with the finite element and moiri experimental results in this study.
... Park et al. confirmed that the in-plane properties are more appropriate to represent isotropic properties of a composite structure rather than the out-of-plane properties. [22,23]. The rule of mixture (ROM) is constructed by assuming that the strain on the in-plane direction is uniform. ...
... Classical laminate theory provides an efficient approach to understand the warpage behavior of a composite structure. Among the theories that can be applied to study the warpage behavior of laminate structure, classical laminate theory has been utilized and provided better data [22][23][24][25]. It is preferably applicable to this package. ...
... There is no general solution to assist parameter adjustment for the electronic packaging samples. To carry out the in-situ warpage measurement of solder ball attached packages with 3-D DIC, the conventional strategy is to remove the solder balls mechanically or melt the solder balls on the substrate surface to generate a flat surface before the experiment [29,30]. It is destructive and poses the risks of damaging the copper pad. ...
Recently, 3-D Digital Image Correlation (DIC) is widely applied to the reliability analysis of electronic packages, which particularly characterizes the in-situ deformation of ball grid array (BGA) packages. During the image correlation procedure, many parameters influence the accuracy and data integrity of measurement result. Facet (subset) size is the principal parameter and has been studied with much effort. However, the solder balls, which are built on the substrate surface, make the scenario different with the conventional 3-D DIC experiment for the planar samples. The undulant surface generates more obstacles for the successful image correlation. In order to summarize an effective solution of 3-D DIC measurement method for solder balls attached packages, camera angle, facet size and facet step are studied with different BGA packages and different stereoscopic camera systems to achieve the best correlation quality. Also, a novel surface treatment method is introduced to guarantee the surface speckles are generated uniformly on the fluctuant surface.
... Park et al introduced DIC method to the reliability test of electronic packages [5]. Later, more applications were applied to the reliability assessment of BGA packages and the validation of effective finite element models [6][7][8]. To eliminate the contamination of surface treatment, some efforts have been made to improve the pattern generation method and recycle the specimen after warpage measurement [9]. ...
... To conduct in-situ warpage measurement of BGA package, both Shadow Moiré and 3D DIC remove the solder balls as the surface treatment [6][7]. These techniques require very fine solder ball elimination; otherwise the substrate surface will be damaged or the root of solder balls will be recognized as the surface of the substrate (Fig. 1). ...
