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Zhao Z.B.,Delphi Corporation | Hershberger J.,Laird Technologies | Bilello J.C.,University of Michigan
Thin Solid Films | Year: 2010

In this work, the failure modes of thin films under thermo-mechanical treatments were observed via in-situ white beam X-ray topography. The in-situ experiments were carried out using an experimental setup on Beamline 2-2 at the Stanford Synchrotron Radiation Laboratory. Magnetron sputtered polycrystalline thin films of Ta and CrN on Si substrates were selected for the present study due to their disparate states of intrinsic residual stresses: the Ta film was anisotropically compressive and the CrN film was isotropically tensile. Under a similar heating-cooling cycle in air, the two types of films exhibited distinct failure modes, which were observed in-situ and in a quasi-real-time fashion. The failures of the samples have been interpreted based on their distinctive growth stress states, superimposed on the additional stress development associated with different forms of thermal instabilities upon heating. These included the formation of oxide for the Ta/Si sample, which led to an increase in compressive stress, and a phase change for the CrN/Si sample, which caused the isotropic stress in the film to become increasingly tensile. © 2009 Elsevier B.V. All rights reserved.

Shitvov A.P.,Queens University of Belfast | Olsson T.,Powerwave Technologies Sweden AB | El Banna B.,Laird Technologies | Zelenchuk D.E.,Queens University of Belfast | Schuchinsky A.G.,Queens University of Belfast
IEEE Transactions on Microwave Theory and Techniques | Year: 2010

This paper presents the results of experimental study of passive intermodulation (PIM) generation in microstrip lines with U-shaped and meandered strips, impedance tapers, and strips with the profiled edges. It is shown that the geometrical discontinuities in printed circuits may have a noticeable impact on distributed PIM generation even when their effect is indiscernible in the linear regime measurements. A consistent interpretation of the observed phenomena has been proposed on the basis of the phase synchronism in the four-wave mixing process. The results of this study reveal new features of PIM production important for the design and characterization of low-PIM microstrip circuits. © 2010 IEEE.

Tong C.,Laird Technologies | Johnson J.,Brush Wellman Inc
2010 Asia-Pacific Symposium on Electromagnetic Compatibility, APEMC 2010 | Year: 2010

CuBe fingerstock gaskets have long set the benchmark for slotted EMI shielding applications with excellent elastic performance. Other alloys such as stainless steels come with compromises in terms of both shielding effectiveness and elastic performance. Offering appealing attenuation performance nearly comparable to CuBe and close spring performance to that of CuBe, CnNiSn offers a potential alternative to traditional CuBe gaskets. This paper gives a brief comparison between CuNiSn and CuBe gaskets through FEA analysis and experimental tests, and highlights how to improve the performance of CuNiSn gaskets to fulfill the needs of manufactures who face an increasingly competitive global market place, in which consumers are both environmentally concerned and price conscious. © 2010 IEEE.

Tong C.,Laird Technologies
2010 Asia-Pacific Symposium on Electromagnetic Compatibility, APEMC 2010 | Year: 2010

The demands of environmentally friendly and whisker-generation-resistant board level shields are increasing with endless marking requirements for high EMC performance and cost-effective electronic products. As a result, some environmentally friendly composite plating steels, such as chromate-free electrogalvernized steel (ZE-38) and ECO-TRIO steel, have been developed and emerged as promising board level shielding materials. This paper assesses and evaluates the acceptability and performance of these materials in accordance with the requirement of board level shielding applications. With good solderability, high resistance to whisker generation, relatively high surface conductivity, and satisfactory corrosion resistance, the ECO-TRIO and ZE-38 steels have great potential to take the place of Tin plated cold rolled steels and Nickel Silver alloys as next generation board level shielding materials. © 2010 IEEE.

Arien Y.,2B Technologies, Inc. | Dixon P.,Laird Technologies | Khorrami M.,Laird Technologies | Degraeve A.,Catholic University of Leuven | Pissoort D.,Catholic University of Leuven
IEEE International Symposium on Electromagnetic Compatibility | Year: 2015

This paper describes a study on the effectiveness of grounding pins and high-frequency absorbers to reduce the emissions of heatsinks up to 20 GHz. The study considers four different types of excitations, namely a direct excitation, an excitation by a patch antenna, an excitation by a microstrip below the center of the heatsink, and an excitation by a microstrip that was off-set with respect to the center of the heatsink. Grounding post are positioned equidistantly along the edges of the heatsink and the number of grounding pins per side is varied. Adding grounding pins significantly reduces the emission of the heatsink below 1-2 GHz. At higher frequencies, they lose their capability to reduce the heatsink emission and even introduce extra resonance frequencies where the emission is higher compared to the ungrounded heatsink. Three different possible arrangements for the application of absorbing material were considered, namely a thin flat absorber just below the heatsink, a ring absorber between the heatsink and the PCB, and a collar absorber around the heatsink. The absorber succeeds in reducing the heatsink's emission above 1-2 GHz, but has little of no positive effect on the emissions below 1-2 GHz. Only by the combination of the grounding pins and the absorber material, a reduction of the heatsink's emission is achieved over the full frequency range. © 2015 IEEE.

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