Kevin E. Howard

Reliability, performance and economics of thermally enhanced plastic packages

Thermal demands on electronic packages are increasing. Resolving these issues in plastic packaging frequently involves a balance of engineering, performance and cost. Conventional plastic packages exhibit limited thermal performance. Thus, engineering solutions, such as modified lead frames, heat sinks or spreaders, which often involve a significant increase in cost, must be considered in those applications where heat dissipation requirements exceed design capabilities. The use of a novel hydrolytically-stable aluminum nitride filler (SCAN), replacing standard fused silica fillers, in transfer molded plastic packages offers another option. AlN is an inorganic dielectric possessing a thermal conductivity much higher than standard silica fillers. Molding compounds and various device packages based on this powder have been introduced commercially. These packages offer large improvements in thermal performance, comparable to heat spreaders and in some cases, exposed heat slugs: reductions of 25-30% in /spl Theta//sub ja/ and 50% in /spl Theta//sub jc/, respectively are typical. Reliability data, including electrical, thermal, environmental and mechanical properties, measured for QFP and SOIC packages indicate that SCAN-based packages exhibit reliability equivalent to packages molded with standard molding compounds. Perhaps most importantly, these packages may also offer significant cost savings, depending on the specific package type.

A green synthesis of bis[1-(hydroxy-κO)-2(1H)-pyridinethionato-κS2]-(T-4)-zinc (zinc pyrithione) nanoparticles via mechanochemical milling

Particulate bis[1-(hydroxy-κO)-2(1H)-pyridinethionato-κS2]-(T-4)-zinc (zinc pyrithione; ZPT) in the diameter range 0.5–0.7 µm is a US FDA-approved anti-dandruff active widely used in anti-dandruff shampoos. A nanoparticulate form of ZPT is expected to exhibit a higher activity, be distributed more effectively on the scalp, require less thickening agent in the shampoo formulation to ensure its stability against settling than the standard form of ZPT, and would enable clear anti-dandruff shampoo formulations. We demonstrate, for the first time, that a green, mechanochemical nanoparticle synthesis process can be used to prepare nanoparticulate ZPT from zinc chloride and sodium pyrithione monohydrate. Both a Reeves attrition mill and a Retsch MixerMill were found to be effective tools for delivering the mechanical energy needed for the conversion. The infrared spectra and X-ray powder diffraction patterns for the products correspond to those for the known desired material. Transmission electron microscopic analysis indicates that ZPT nanoparticles with primary particle diameters in the range of 20–200 nm (mean diameters of 65–100 nm) can be obtained via this method.