Key-one Ahn

Particle Sampling and Real Time Size Distribution Measurement in H2/O2/TEOS Diffusion Flame

Growth characteristics of silica particles have been studied experimentally using in situ particle sampling technique from H2/O2/Tetraethylorthosilicate (TEOS) diffusion flame with carefully devised sampling probe. The particle morphology and the size comparisons are made between the particles sampled by the local thermophoretic method from the inside of the flame and by the electrostatic collector sampling method after the dilution sampling probe. The Transmission Electron Microscope (TEM) image processed data of these two sampling techniques are compared with Scanning Mobility Particle Sizer (SMPS) measurement. TEM image analysis of two sampling methods showed a good agreement with SMPS measurement. The effects of flame conditions and TEOS flow rates on silica particle size distributions are also investigated using the new particle dilution sampling probe. It is found that the particle size distribution characteristics and morphology are mostly governed by the coagulation process and sintering process in the flame. As the flame temperature increases, the effect of coalescence or sintering becomes an important particle growth mechanism which reduces the coagulation process. However, if the flame temperature is not high enough to sinter the aggregated particles then the coagulation process is a dominant particle growth mechanism. In a certain flame condition a secondary particle formation is observed which results in a bimodal particle size distribution.

In-situ observation of formation of nanosized TiO2 powder in chemical vapor condensation

Abstract The present study has attempted to in-situ observe the formation ofnanosized TiO2 powder during chemical vapor condensation process. For this purpose, the powders were sampled at various positions in the furnace using a quartz collecting rod of which surface acts as the powder condensation site. It was discussed in terms of size effect on the phase stability that the fine anatase particle transformed to the coarse rutile phase by growing in the high temperature region. Also the parabolic particle growth with the distance of reaction tube was explicated by computated residence time with solving temperature and gas velocity distribution numerically for different oxygen flow rate conditions.

Synthesis of dual nanoparticles embedded in polyimide and their optical properties

AbstractWe investigated the formation of Cu or ZnO nanoparticles and mixture of Cu and ZnO nanoparticles dispersed in polyimide (PI) films using Cu(NO3)2 and Zn(NO3)2 salts. Each metal salt or the mixture of Cu(NO3)2 and Zn(NO3)2 salts was blended with N-methyl-2-pyrrolidinone and polyamic acid (PAA), and the solutions were spin-coated onto the substrates. Metal and metal oxide nanoparticles formed in PI films during the imidization of PAA to PI in a reducing atmosphere. X-ray diffraction analysis showed that a single phase of Cu or ZnO nanoparticles, or mixture of Cu and ZnO nanoparticles formed in PI films depending on the metal salt types, and transmission electron microscopy revealed that Cu and ZnO nanoparticles were dispersed in the PI matrix. The absorption spectra showed a surface plasmon resonance peak (SPR) of Cu nanoparticles around 600 — 620 nm or an absorption shoulder of ZnO nanoparticles around 360 — 370 nm. The SPR peak was blue-shifted in nanocomposites containing dual nanoparticles in comparison with nanocomposites containing single Cu or ZnO nanoparticles.

A peel adhesion study of electroless Cu layers on polymer substrates

ABSTRACT The peel adhesion between two different electroless-plated Cu layers and polymer substrates was studied. Cu was electroless-plated onto polymer substrates using two different commercial solutions with different compositions. The adhesion strength between the electroless Cu layers and polymer substrates was measured with the 90° peel test. The adhesion was influenced by the coverage, grain size, and the thickness of the electroless Cu layer. Poor coverage of the electroless Cu layer increased the density of the pores at the interface between the Cu layer and the substrates, thereby degrading the adhesion strength because of a decrease in the contact area. In addition, the electroless Cu layers with larger nodules and larger grains were softer and had higher peel adhesion since the soft and ductile Cu layer promoted a greater amount of plastic deformation during the peel test. This led to enhanced peel adhesion. Finally, as the thickness of the electroless Cu layer increased, the peel adhesion decreased. The thicker Cu layers are not easily bent. Poor bending of the Cu layer induced less plastic deformation, causing a decrease in the peel adhesion. In conclusion, soft and thin electroless Cu layers with greater coverage are preferred in order to obtain good adhesion.

Degradation of adhesion between Cu and epoxy-based dielectric during exposure to hot humid environments

Abstract Degradation of adhesion between Cu and epoxy-based dielectric build-up film (EDF), which is used for fan-out wafer level packaging applications, was investigated by the reliability test. The samples were composed of four layers: epoxy molding compound substrate, laminated EDF, electroless Cu, and electrolytic Cu. Adhesion was evaluated by the 90° peel test before and after the temperature and humidity (T&H) test and the highly accelerated temperature and humidity stress test (HAST). The effects of the peel strip width and humidity exposure of the peeled edges on adhesion were determined. It was found that adhesion gradually decreased during the reliability tests. The adhesion reduction mechanism was explained by the combinatorial effect of the loss in chemical bonding and the degradation of mechanical interlocking due to moisture. A black strip was observed along the edges of the peeled Cu strips (herein referred to as the black band, BB). AES revealed the BB as the superficial oxidation of the Cu strip. HAST and the T&H test showed the effect of the BB in an additional adhesion loss. SEM revealed a local cohesive fracture of the polymer, which led to an additional loss due to an early failure of the degraded polymer. Furthermore, BB growth showed a linear correlation with the square root of time and was accompanied with adhesion reduction. Since the modern packages have micro-sized Cu lines, the formation of BB should be avoided for better reliability of devices.