To facilitate the fabrication of a reliable stacked package for a semiconductor, UV/heat dual curing of adhesives was investigated. The formulated adhesives contained acrylic monomer and epoxy resins. First, UV curing was conducted on the acrylic monomer, followed by heat curing. It was found that UV-curable acrylic monomers affected the adhesive's properties, e.g., adhesion, water absorption, and viscoelasticity. As the acrylic monomer, neopentylglycol diacrylate (NPGDA), trimethylolpropane triacrylate (TMPTA), dipentaerythritol hexaacrylate (DPHA), and tricyclodecanedimethanol acrylate (TCDDA) were used to investigate the effect of functional group numbers and structure. As a result, an acrylic monomer that has two functional groups with a rigid moiety (TCDDA) showed acceptable properties as adhesives for the fabrication, and thus a UV/heat-curing adhesive has been successfully developed.
The nonrepeatable radial vibration (NRRV) of spindle motors used in magnetic disk memory devices was studied in detail. In particular a theoretical and experimental investigation on the comparison of NRRV in time and frequency domains was conducted. The random and statistical characteristics of NRRV were ascertained by analyzing the amplitude distributions of both asynchronous and synchronous vibration components in the frequency domain. It was found that the main part of NRRV is composed of asynchronous components in most of the spindles tested. Some of the asynchronous component amplitudes, varying randomly, can be approximated by Rayleigh distribution function. It was also found that the synchronous vibrations include nonrepeatable components. The variance of NRRV measured in the time domain was shown theoretically and experimentally to be equal to the sum of the total power of asynchronous components and the total variance of synchronous components. From this relation, the cause of tracking error in such memory devices can be analyzed quantitatively in frequency domain.
Thermal curing of adhesive films was investigated to facilitate the fabrication of a reliable bonding for semiconductors. The formulated adhesive films contained acrylic polymer, epoxy resins, phenol resin, and an imidazole derivative that was the catalyst for curing the epoxy resins with phenol resin. The solubility, thermally latent characteristics, mechanical and adhesive properties of 2-methylimidazole/boron trifluoride (2MZ/BF3), and 2MZ/aluminum trisacetylacetonate (AlAC) were investigated. It was found that 2MZ/BF3 and 2MZ/AlAC had excellent solubility in adhesive materials and they had excellent latent characteristics as thermal curing catalysts for epoxy resins, whereas conventional catalysts (2MZ and 2-phenyl-4, 5-dihydroxymethylimidazole (2PHZ)) could not achieve both excellent solubility and thermally latent characteristics. The mechanical and adhesive properties of the post-thermal-cured adhesive film that contained 2MZ/ BF3 or 2MZ/AlAC were comparable to those of the postthermal-cured adhesive films that contained conventional catalysts.
The kinetics of the propylene polymerization with TiCl3‐AlEt3 has been investigated in the temperature range (30‐70°C.), the pressure range of propylene (100‐700 mm. Hg), and the concentration range of the catalysts (2 g. TiCl3/liter, [A]/[Ti] = 0.4‐3.0). The polymerization rate R increases rapidly with the polymerization time t at first (stage I), which is followed by a gradual decrease to the stationary value Roo, (stage II). The kinetic behavior in stage I in the case when propylene is introduced after the addition of AlEt3 is expressed by and that in the case when propylene is introduced before the addition of AlEt3 is expressed by The kinetic behavior in stage II, which is independent of the above procedure, is expressed by where R∞ is the stationary rate represented by and Ro a constant. The activation energies are E1 = 15, E2 = 17, Et3 = 2‐3, E3″ = 12, and EP = 10 kcal./mole, respectively. The heat of adsorption of AlEt3 was obtained as 12 kcal./ mole from the temperature dependence of K. Stage I is explained on the basis of the formation of polymerization centers from Al2Et6 and a propylene monomer on the surface of TiCl3. Stage II is attributed to an irreversible deactivation of the polymerization centers localized on unstable surface sites due mainly to a spontaneous process and partially to a propylene monomer (or polymer) attack.
To facilitate the fabrication of a reliable semiconductor package, the UV/heat dual curing of film adhesives was investigated. The curing system of the epoxy resin affected the film adhesive properties. As the UV/heat dual-curable epoxy resin, a modified o-cresol novolak epoxy resin, in which half of the glycidyl groups were substituted by acryloyl groups (OCN-AE), was applied to the film adhesive. The formulated film adhesive contained acrylic copolymer, OCN-AE, phenolic aralkyl resin as a heat-curing agent of the glycidyl groups, and 1-hydroxycyclohexyl phenyl ketone as a photoinitiator of the acryloyl groups. The formulated reference film adhesive contained unmodified o-cresol novolak epoxy resin (OCN-E) in place of OCN-AE. Formulated film adhesives containing a mixture of OCN-E and o-cresol novolak epoxy acrylate were also used as references. The morphology and the film adhesive properties were investigated. In these investigations, the film adhesive of OCN-AE showed better adhesive properties, lower modulus, and a better stress-relaxation ability than the referenced adhesives. As a result, a reliable film adhesive for semiconductor packages was successfully developed.
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