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.

Reduction in Processing Time in Ca3Co4O9+δ Ceramics through Nanoprecursors Produced by an Easily Scalable and Environmentally Friendly Process

Attrition milling is an easily scalable and environmentally friendly process used to produce Ca3Co4O9+δ nanoprecursors in a relatively short time. Sintered materials produced through the classical solid-state method, involving ball milling, show much larger grain sizes and slightly lower density than those obtained in samples produced from attrition-milled precursors. On the other hand, electrical resistivity has been drastically decreased, accompanied with a slight decrease in the Seebeck coefficient in samples obtained from these attrition-milled precursors. Moreover, the use of an attrition milling process leads to a very important reduction in processing time (around 75%), together with a slight power factor improvement of around 10%, when compared to the classically prepared samples.

Production of aluminum nanoparticles by wet mechanical milling

One of the great challenges in the use of nanomaterials is their production at low costs and high yields. In this work aluminum nanoparticles, from aluminum powder, were produced by wet mechanical milling through a combination of different attrition milling conditions such as ball-powder ratio (BPR) and the amount of solvent used. It was observed that at 600 rpm with a BPR of 500/30 g for 12 h, it was possible to produce nanoparticles with a size close to 20 nm, while at 750 rpm with a BPR of 380/12.6 g for 12 h, nanoparticles of approximately 10 nm were obtained. Scanning and transmission electron microscopy confirmed that the milling product is an agglomeration of nanoparticles with different sizes. These results show the feasibility of obtaining aluminum nanoparticles by mechanical milling using only ethanol as solvent, avoiding hazardous by-products obtained from chemical routes, and the use of complicated methods such as laser ablation and arc discharge.

Fine Comminution of Pine Bark: How Does Mechanical Loading Influence Particles Properties and Milling Efficiency?

The use of lignocellulosic plant biomass as an alternative to fossil feedstocks for chemistry, energy and materials often involves an intense dry comminution step, for which the energy consumed can vary significantly according to the process parameters, the particle size targeted, and the properties of the biomass. Here we studied the fine milling of maritime pine bark in an impact-mill configuration and in an attrition-mill configuration. The properties of the resulting powders (particle size distribution, particle shape, specific surface area, agglomeration level) obtained in each configuration were compared in relation to process energy consumption. Results evidenced that the agglomeration phenomena drive milling efficiency and limit the possibilities for reaching ultrafine particles. Interestingly, impact loading proved more effective at breaking down coarse particles but tended to generate high agglomeration levels, whereas attrition milling led to less agglomeration and thus to finer particles.