Thermally conductive films play a crucial role in expanding the lifetime of electronics by dissipating concentrated heat to heatsinks. In this work, a thermally conductive film (g-TC film) was manufactured using a perforated graphite sheet (p-GS) and a UV-curable pressure-sensitive adhesive (PSA) by lamination. A novel UV-curable PSA was prepared by incorporating a UV-curable abietic acid ester into a PSA composition. The UV-curable PSA became a tack-free film upon UV irradiation; thus, a flexible g-TC film with a 52-μm thickness was obtained. The defects in the g-TC film caused by air bubbles were removed by treating the p-GS with oxygen plasma. As the UV-cured PSA made a joint through the holes in the p-GS, cleavage of the graphite was not observed after 10,000 U-folding test cycles with a folding radius of 1 mm. The calculated in-plane thermal conductivity of the fabricated g-TC film was 179 W∙m−1K−1, which was stable after the U-folding tests.

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Delamination at the interface between a silicon backside and the die attach paste has been reported, and this delamination led to package cracking, resulting in reliability problem. In this paper, a series of experiments was conducted to investigate factors affecting the interfacial adhesion between the die back side and the attach paste of an Integrated Circuit (IC) package. Poor interfacial adhesion potentially leads to a delamination and crack at the interface. The aim is to understand better the interfacial adhesion phenomena, and possible failure mechanism(s) of a Ball Grid Array (BGA) package with delaminatiodcrack propagation between the die back side and the die attach paste.Numerous analysis and explorations on delamination were made by CSAM and cross-section work on dummy packages. During the course of investigations, contact angles, Atomic Force Microscopy, (AFM) and Electron Spectroscopy for Chemical Analysis (ESCA) were used. Adhesion test using a Shear test mode was done on dummy samples after die attach cure.Based on the evaluation results, factors that affect adhesion between die attach paste and silicon die were identified. Factors include namely UV tape adhesive transfer to die hack side, surface energy of silicon surface, and die attach paste toughness. The amount of chemical residues from the UV tape affects the adhesion strength. Contradictory to a common knowledge, the presence of a group of siloxane materials (silicones) which formed part of the chemical residues does not significantly influence the adhesion behavior between the die back side and die attach paste. An attempt was made to explain the observation.It was found that interfacial adhesion improves with die paste with a higher Kj, value (higher toughness). High surface energy of silicon surface remains the most important factor. This means that processes that activate the silicon surface would improve the adhesion strength. This can he achieved by, for example, a plasma treatment. Samples were built and the findings tested with positive results. delamination, and cross sectional work was done to further understand the delamination. Occasionally, delamination at the die back side and the die attach paste was observed, as illustrated in Figure 1. r -l Die back Figure 1: Cross section of a package showing die to paste delamination.

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In response to the demand for high-performance materials, epoxy thermosetting and its composites are widely used in various industries. However, their poor toughness, resulting from the high crosslinking density of the epoxy network, must be improved to expand their application to the manufacturing of flexible products. In this study, ductile epoxy thermosetting was produced using thiol compounds with functionalities of 2 and 3 as curing agents. The mechanical properties of the epoxy were further enhanced by incorporating fumed silica into it. To increase the filler dispersion, epoxide-terminated polydimethylsiloxane was synthesized and used as a composite component. Thanks to the polysiloxane–silica interaction, the nanosilica was uniformly dispersed in the epoxy composites, and their mechanical properties improved with increasing fumed silica content up to 5 phr (parts per hundred parts of epoxy resin). The toughness and impact strength of the composite containing 5 phr nanosilica were 517 (±13) MJ/m3 and 69.8 (±1.3) KJ/m2, respectively.