Abstract:

The current practice of viscoelastic numerical analysis based on the assumption of constant Poisson’s ratio or constant bulk modulus – architecture-dependent modeling – is discussed in conjunction with the authentic material-based modeling based on the linear viscoelastic constitutive questions that require the temperature-dependent viscoelastic properties of shear and bulk moduli. The paper explains in detail how shear and bulk moduli are calculated from the viscoelastic Young’s modulus, obtained from DMA testing, under the assumptions together with the critical implications of the assumptions. The property measurements for the authentic material-based modeling are then followed, specifically, (1) measurement of Young’s modulus using DMA, (2) determination of bulk modulus from measured hydrostatic testing data using shift-factors obtained from Young’s modulus master curve; and calculation of shear modulus from Young’s modulus and bulk modulus. Warpage can be predicted accurately using the required properties, which can possibly offer a radically different approach to "design" warpage, in contrast to the conventional approach to "control" warpage.

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