Dispersion polymerization of styrene in ethanol was carried out to encapsulate aluminum flakes. The effects of three reactive surfactants, two anionic and one nonionic, were investigated. It was confirmed prior to encapsulation that these surfactants did not polymerize by themselves but did promote polymerization of styrene. The capsules obtained were characterized with respect to the morphology and mean size. The encapsulating efficiency of the polymer of the wall material, the wall thickness, and the molecular weight distribution were measured. The effects of the concentrations of styrene monomer and reactive surfactants on these characteristics were determined and discussed. Aluminum flakes were coagulated to form secondary particles and they were covered with fine polymer particles, which were precipitated in the continuous phase. To improve encapsulation, the auxiliary addition of nonionic surfactant was attempted. By controlling those concentrations, capsules covered with polymer layer were prepared.

Propylene oxide was polymerized by diethylzinc/ketone system. Cocatalytic effects of twenty-four ketones were examined. Methyl ketones and cyclic ketones were effective as a cocatalyst for the polymerization, while a k y l ketones with longer chain and P-diketon were not. The reaction of the catalyst formation was discussed. Crystallinity of the polymers obtained was compared with that of polymers by diethylzinc/water or diethylzinc/ alcohol catalyst. ZUSAMMENFASSUNG:Propylenoxid wurde mittels eines Diathylzink/Keton-Systems polymerisiert. Es wurde die cokatalytische Wirkung von vierundzwanzig Ketonen gepriift. Dabei zeigten Methylketone und cyclische Ketone eine Wirkung, wahrend aliphatische Ketone mit langerer Kette und 1,3-Diketone unwirksam blieben. Es wurden die Reaktionen, die zur Bildung der Katalysatoren fiihrten, erortert. Die Kristallinitat der erhaltenen Polymerisate wurde mit derjenigen anderer Polymerisate verglichen, die mit Diathylzink/Wasser-und Diathylzink/Alkoholkatalysatoren hergestellt wordep waren.

We developed vacuum assisted underfill technology for large die (>18 × 18 mm) with fine pitch area array bumps (< 150 m pitch) to solve a critical underfill void issue. Material development and process optimization are the keys to realize a stable process for such an advanced package. It was also confirmed that the newly developed underfill materials have good reliability on the large die package.

This paper reports on the study of flexible epoxy resin which lowers modulus to minimize warpage while maintaining high filler content. Liquid Compression Molding (LCM) material is an encapsulation material applied at the wafer level. LCM requires high reliability and minimized warpage after curing. The flexible epoxy resin was studied to determine if it could be technically feasible to meet the requirements. Three epoxy resins with different structures, Conventional epoxy, and Flexible epoxy A and B, were examined. Both samples with Flexible epoxy A and B resulted in lower warpage than Conventional resin. Especially, Flexible epoxy B showed the minimal warpage with the lowest modulus. The sample with Epoxy B performs the best at 260 degree Celsius with the minimal warpage. A reliability test of LCM with Epoxy B was also conducted assuming the application for Fan-out packaging. Epoxy B showed no delamination or cracks under a thermal cycling test up to 1,000 cycles after MSL1 moisture exposure.

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