Conference Paper

Assessment of FOWLP process dependent wafer warpage using parametric FE study

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Abstract

The paper presents the steps for the parametric finite element model creation of the wafer, material characterization of the adhesive tape, analytical and finite element study of the wafer warpage considering the bifurcation, gravity effect on the wafer bow assessing the warpage of mold/Si bilayered structure under thermal loading. The analytical results are compared to finite element analyses (FEA) considering the linear and nonlinear deflection. Consequently, the FEA approach has been used to study the deformation of 12” reconstituted wafers in their FOWLP fabrication process. By changing the temperature, the deformation of the wafer shows a bifurcation point, at which the warpage changes between the spherical and cylindrical shapes. The bifurcation region has been analyzed for the relevant range of overmold thicknesses in order to provide the guidance to optimum wafer and process designs that avoid the excessive warpage. For different wafer structures, the study determines also the effects of the gravitational force on the wafer bow as well as its influence in combination with the thermal mismatch. Finally, the FOWLP process induced warpage has been demonstrated by FEA incorporating the geometrical nonlinearity, gravity and ground support by means of contact elements.

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... Неравномерные напряжение и деформации, существенное влияние способа и области крепления пластин, влияние гравитации [3] становится гораздо более выраженными для пластин диаметром 300 mm [4], для утоненных пластин [5], в том числе при создании сборок пластин [6]. Отдельно следует отметить, что при уменьшении толщины пластин начинает наблюдаться ассиметричный (цилиндрический, седловидный) изгиб [4,7,8], этот процесс в настоящее время слабо изучен. Для уменьшения коробления пластин может быть использована термообработка, нанесение пленки на обратную сторону пластины [7], формирование компенсирующих структур на обратной стороне пластины [7], управление толщиной и механическими напряжениями слоев и др. ...
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... Recently the use of simulations has also been extended to investigate the effect of bifurcation at wafer level packaging [1,22] and specifically in the fan-out-wafer level packaging technology [23][24][25]. Indeed, with the development of the ultrathin chip technology [26][27][28] and fan-outwafer level packaging [29,30] gaining a control of the warpage has become a more critical feature, either at die or at wafer level, since it can have an extreme influence on the mechanical reliability of the final system in package (SiP), as well as on the wafer processability [31]. ...
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