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Direct-plated-copper (DPC) aluminum nitride (AlN) substrate with a high thermal conductivity can provide a good alternative to conventional aluminum oxide (Al 2 O 3 ) substrate for better heat dissipation in the high-power module applications. However, the DPC AlN substrate suffers AlN crack initiating at the edge corner of Cu film during thermal cycling, due to the higher thermal expansion coefficient mismatch with copper material. This study is to resolve the AlN crack problem of DPC AlN substrate during thermal cycling and further to provide important parameters for mechanical design for ensuring good thermal reliability. Prior to the analysis, the out-of-plane deformation measurement of a Cu-AlN bi-material plate subject to the solder reflow heating and cooling is conducted for evaluating the material property of the plated Cu film and residual stresses induced from the manufacturing and solder reflow process. The results show the hysteresis and Bauschinger-like behaviors for the Cu-AlN plate during the solder-reflow heating and cooling. It is also found from the validated finite element simulation that the Cu-film wedge angle, length, and thickness significantly affect the maximum 1st principal stress of AlN during thermal cyclic loading, and the predicted failure mode and location based on the maximum 1st principal stress is consistent with experimental observation. The other factors, such as single-side and double-side Cu-film (sandwich-structure-alike) substrates, length difference of Cu films, and the nonlinear property of Cu film will be presented and discussed in detail as well. [ABSTRACT FROM AUTHOR]

This paper aims to measure and simulate the warpages of 3D through-silicon via (TSV) die-stacked dynamic-random-access-memory (DRAM) packages during the manufacturing process. The related die stresses and keep-out zone (KOZ) for the stacked dies in the packages at room temperature are further calculated with the validated simulation model. The out-of-plane deformations (or warpages) of the packages from the full-field shadow moiré are documented under temperature loading and found consistent with those from finite-element method (FEM). The results of the stresses and KOZs at the proximity of a single TSV for each die in the package at room temperature are presented. It is found that the sizes of KOZs in four-die stacked DRAM packages with and without epoxy molding compound (EMC) at room temperature are dominated by the horizontal pMOS transistors and more than double the size in wafer-level die. The sizes of KOZs at each die are similar in this four-die stacked DRAM package, even though the stresses at each die are apparently different. [ABSTRACT FROM AUTHOR]

The thin silicon dies have been widely used in the three-dimensional integrated circuits (3DIC), stacked-die or wearable electronic packages to meet the requirements of small size, low-profile features, high-pin count, high performance, low-power consumption or even flexibility. The bending strengths of the thin dies cut from silicon wafers have to be determined to ensure no reliability problems, mostly resulting from packaging process handling, reliability testing, and operations. Three-point bending (3PB) and four-point bending (4PB) tests are commonly used for measuring die bending strength; however, both tests are still problematic for testing the thin silicon dies. Therefore, the mechanics of both tests are reevaluated in this study by a nonlinear finite element method (NFEM) with taking into account geometric nonlinearity (or large deflection), associated with the related theoretical formulations. The nonlinear mechanics of both tests are discussed in detail. NFEM results-based correction factors to the linear beam solutions are further proposed in the form of the polynomial fitting equations in this study. Those polynomial fitting equations of the correction factors are proved to be workable and easy to use with an engineering acceptable accuracy. Those correction factors are also found highly dependent on the deflection (δ), span length (L) and radius of roller support (r), but not on test specimen thickness (t) and elastic modulus (E). • The nonlinear mechanics and validation of 3PB and 4PB tests have been studied in detail. • Correction factors to the linear solutions for two tests are proposed with fitting equations extracting from the NFEM data. • Correction factors depend on deflection, span length and radius of roller supports, but not on specimen thickness and modulus. • Correction factors newly proposed can be applied for thin silicon dies and other materials. [ABSTRACT FROM AUTHOR]

Describes the use of recombinant retinoblastoma gene product to screen a human complementary DNA expression library. Reports that the isolated retinoblastoma binding protein genes exist in separate loci and produce discrete messenger RNAs.