Reliability and Durability Enhancement of Large-area Mullite-cordierite Composite Substrates for Semiconductor Probe Card

Spherical mullite (M)-cordierite (C) composite granules were prepared by spray drying the fine starting powders obtained from attrition milling to produce sintered mullite-cordierite composite pellets with a dense structure. The effects of attrition milling on the morphology, size and size distribution of the formed composite granules were investigated. The results showed that the milled starting powders formed the spherical granules with homogeneous size distribution. The composition ratio (M:C = 100:0, M:C = 90:10, M:C = 70:30, M:C = 50:50, M:C = 30:70, M:C = 0:100) and sintering temperature (1300–1450℃) were optimized to fabricate the sintered mullite-cordierite composite pellets with low thermal expansion coefficients (TECs) and excellent mechanical properties. Samples of 70 wt% mullite-30 wt% cordierite sintered at 1350℃ exhibited excellent bulk density, porosity, TEC, and flexural strength. Based on these results, a large-area mullite-cordierite composite substrate was fabricated for application in semiconductor probe card. The changes in sheet resistance and flexural strength were measured to study the influence of the environmental tests, including high temperature storage test, damp heat test, and thermal shock test, on the large-area substrate. A low rate of change in sheet resistance and flexural strength was observed. After the environmental tests, the sheet resistance and flexural strength were confirmed to be within 10% of their values prior to the tests. These results show that the fabricated mullite-cordierite composite exhibits high reliability and durability and is a suitable for semiconductor probe cards.

Effect of Carbon Addition on Direct Reduction Behavior of Low Quality Magnetite Ore by Reducing Gas Atmosphere

Recently, direct reduced iron (DRI) has been highlighted as a promising iron source for electric arc furnace (EAF)-based steelmaking. The two typical production methods for DRI are gas-based reduction and reduction using carbon composite pellets. While the gas-based reduction is strongly dependent on the reliable supply of hydrocarbon fuel, reduction using ore-coal composite pellets has relatively low productivity due to solid–solid reactions. To overcome the limitations of the above two processes, and to achieve a more efficient direct reduction process of iron ore, the possibility of combining these two methods was investigated. The experiments focused on performing an initial direct reduction using ore-coal composite pellets followed by a second stage gas reduction. It was assumed that the initial reduction of the carbon composite pellets would enhance the efficiency of the subsequent reduction by gas and the total reduction efficiency. The porosity, as well as the carbon efficiency for direct reduction, were measured to determine the optimal conditions for the initial reduction, such as the size ratio of ore and coal particles. Thereafter, further reduction by the reducing gas was carried out to verify the effect of the preliminary reduction. The reduction kinetics of the reducing gas was also discussed.

Synthesis of BiF3 and BiF3-Added Plaster of Paris Composites for Photocatalytic Applications

A BiF3 powder sample was prepared from the purchased Bi2O3 powder via the precipitation route. The photocatalytic performance of the prepared BiF3 powder was compared with the Bi2O3 powder and recognized as superior. The prepared BiF3 powder sample was added in a plaster of Paris (POP) matrix in the proportion of 0%, 1%, 5%, and 10% by wt% to form POP–BiF3(0%), POP–BiF3(1%), POP–BiF3(5%), and POP–BiF3(10%) composite pellets, respectively, and activated the photocatalytic property under the UV–light irradiation,in the POP. In this work, Resazurin (Rz) ink was utilized as an indicator to examine the photocatalytic activity and self-cleaning performance of POP–BiF3(0%), POP–BiF3(1%), POP–BiF3(5%), and POP–BiF3(10%) composite pellets. In addition to the digital photographic method, the UV–visible absorption technique was adopted to quantify the rate of the de-colorization of the Rz ink, which is a direct measure of comparative photocatalytic performance of samples.