Heraeus, Inc.

Feedstock of 97 weight% tungsten heavy alloy with different particle characteristics was injection molded as tensile bars and investigated for green d., solvent debinding kinetics, sintered d., and the tensile properties. Feedstock with higher agglomerate content resulted in injection molded bars with lower green d. Contrary to the expectations, the debinding kinetics, sintered d., and sintered properties of the heavy alloys were not influenced by the agglomerate content. Microstructural and fractog. anal. of the sintered samples supported the above observations, with similarities in microstructural parameters such as contiguity, porosity, grain size, and fracture morphol. of the sintered alloys. It is concluded that favorable wetting, spreading and solubility characteristics of tungsten and the liquid phase consisting of W-Fe-Ni eliminate the inhomogeneities in the microstructure resulting in densification and uniform sintered properties.

The problem of automotives running out of gas in a faster rate is addressed in this paper. Such problem can be eliminated through the replacement of the fuel level sender, a common automotive application for thick film. Specifically discussed is how thick film is applied for such purpose, the development of fuel senders over the years and the raw materials for its production The raw material used for a fuel sender, such as the wiper contact and the thick film pastes, which have different effects on the automotive performance must take into consideration the global nature of the automotive economy. Thick film alloy affects signal resolution, migration resistance and chem. durability. Manifestation of such effects is when the alloy is too soft or too high in silver, shorts between segments may occur and eventual reduction of Ag to <50% of the metal content has shown to be effective. For the application in fuel level sensors, mixtures or alloys of Ag/Pd or Au/Pd/Pt are generally preferred but some automobile manufacturers have issued a ban on the use of any Ag used in the fuel level sensor. For wipers, many Au bearing alloys are now recommended for usage.

The highest bump height-to-pitch ratio (H/P) possible with today solder paste and stencil technologies was determined using different pulse-stencil-pitch combination. Anal. of the different combination plots revealed three main trends. First, the finer Type 6 powder yielded a higher average H/P ratio. This was a result of higher packing d. which led to more solder deposited per unit μm³ of printed solder volume Second, round apertures produced the majority of the maximum H/P ratios. Lastly, as pitch increases, so does the H/P ratio. Since the denomination of the ratio is pitch, it was anticipated that the H/P ratio should be a straight line when plotted against pitch. One theory is that since the webbing dimension is independent of pitch, a larger percentage of the available printing real estate is consumed by the webbing.