The capability of a cobalt-phosphorous [Co(P)] layer, which was grown via the electroless plating process, to serve as the diffusion barrier of lead-tin (PbSn) solder was investigated in this work. The Auger electron spectroscopy (AES) and energy dispersive spectrometry (EDX) indicated that the phosphorous contents in Co(P) films decrease with increasing film thickness and that the average contents are no less than 8.7 at.% for the specimens prepared in this work. X-ray diffraction in conjunction with composition analyses revealed that the electroless Co(P) layer was a mixture of amorphous and nanocrystalline structures; however, the AES depth profile and subsequent analyses indicated that the first-formed Co(P) layer should be amorphous because it contains as much as 18 at.% P. This implied a good barrier capability for electroless Co(P) because, as revealed by EDX line scan, the Sn and Cu atoms could not penetrate the Co(P) layer after the PbSn/Cu/Co(P)/Cu/Ti/Si sample was subjected to annealing at 250°C in a forming gas ambient for 24 h. The fact that Sn and Cu underlayers could not penetrate the Co layer after such a liquid-state annealing step was evidence that the Co(P) layer may simultaneously serve as a diffusion-barrier interlayer dielectric and as an under-bump metallization for flip-chip copper (Cu) ICs.
This study synthesized a series of prepolymers from butyl acrylate and functional monomer with various side-chain structures. A bulk polymerization process was then applied under ultraviolet irradiation. The molecular structure of the prepolymer was characterized by Fourier transform infrared spectroscopy and gel permeation chromatography. The degradation temperature and glass transition temperature ( Tg) were examined. The prepolymer was employed to the acrylic hot-melt pressure-sensitive adhesives (HMPSAs) and the corresponding adhesive performance was presented. In this study, glycidyl methacrylate was considered to be an effective cross-linking agent for acrylic HMPSAs containing carboxylic acid groups. The prepolymer containing carboxylic acid synthesized acrylic HMPSAs exhibited high adhesion in peel strength and shear strength compared to the hydroxyethyl group. The adhesive performance of HMPSAs in different environments was also investigated.
This study introduced multi-quality optimization using the Taguchi method combined with response surface methodology (RSM) and the particle swarm optimization (PSO) method for synthesizing pressure sensitive adhesives (PSAs) of ultraviolet curing optically clear adhesives (OCAs). The process parameters used in this study included 2-ethylhexyl acrylate (2-EHA) monomer content, the photoinitiator content and the oligomer content using N,N-dimethylacrylamide and acrylic acid. The quality responses included the peel strength, the transmittance, the haze and the refractive index. The Taguchi method was adopted because it could reduce the number of experiments and cost, as well as effectively arriving at a single optimum parameter. The results from the Taguchi method were combined with RSM and PSO to obtain a single composition that has the optimum response for all qualities. The results of the confirmation experiment showed that the optimum parameters were 80 wt% of 2-EHA content, 4.32 wt% of photoinitiator content and 45 wt% of oligomer content, which could obtain the peel strength at 720.3 g/25.4 mm, transmittance up to 97.94%, haze of only 1.93% and refractive index at 1.48. All of qualities meet the industrial requirement of OCA PSAs.
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