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Dynamic phasors models capture transients in (main) harmonic coefficients of periodically dominated systems, and their utility in state approximations is supported by machine and power systems case studies. This article explores analytical plausibility arguments, and inherent restrictions of such approximations in dissipative systems with quadratically nonlinear lossless components. Index Terms--Dissipative system, dynamic phasors.

A study was conducted on previous solutions for the influence of single layers on the thermal spreading resistance of heat flux tubes, compound disks and other circular heat sources undergoing different heat flux distributions. A compound disk solution was found to effectively compute the spreading resistance for all heat sources. Proposed approximations offer upper and lower bounds on the total thermal resistance for a spreader-heat sink problem that can be used on diamond spreader-copper heat sink devices.

A thermal evaluation of the passive heat sink for a PowerPC 620 microprocessor in a multiprocessor computer shows that the microprocessor junction temperature is 85 degrees celsius for a 25 W heat dissipation. The temperature is maintained at 101 degrees celsius for a 30 W heat dissipation. Fluid dynamic computer simulations model the airflow at the system- and board-level. The results obtained using a compact heat exchanger are discussed.

Thermal performance of a pin fin heat sink of a height up to 15 mm, base size of 25 X 25 mm and 6 X 6 pin fin configuration is optimal in low velocity, open flow and unshrouded type conditions. The fin cross section is 1.5 X 1.5 mm. The performance of the sink is independent of flow direction. A study on different heat sinks shows that the effect of anodizing on the thermal performance is negligible and chromated sinks are suitable for most applications.

The problem of estimating the geometrical parameters of a heat sink for maximum heat dissipation of power semiconductor devices (PSD) is considered. To this end, an experiment to investigate heat exchange 'in cooling channels under forced movement of dielectric coolant.' The experiment involves 'liquid boiling on finned surfaces' for removing high-intensity heat fluxes from cooled PSD components.

A particulate heat sink paste, consisting of submicron diamond dispersed in n-decane, provides a short thermal path between the working face of a semiconductor device and its casing. Its thermal conductance increases with increasing temperature without mass flow, contrary to the linear decrease in thermal conductance of its constituents, namely the diamond and n-decane. An increase in packing fraction results in a greater gas-like behaviour and a consequent increase in thermal conductance. Micropore geometry also affects the heat transport in a direction normal to the particle surface.

Gold-tin solders in 80%-20% ratio are used to mount commercial 1 watt laser diodes soldered on chemical vapor deposition diamond heat sinks. An additional metallization of 2 micrometers gold reduces the mechanical stress in the laser diode and forms reproducible bonds. An analytical model calculates the maximal shear, tensile, and peel stress. High resolution X-ray microscopic results show the absence of voids in the bond interface. The results of the burn-in and the first-accelerated aging tests are presented.

Vapor-deposited micro heat pipe arrays (VDMHP) were fabricated as an integral part of semiconductor devices to act as efficient heat spreaders by reducing the thermal path between the heat sources and heat sink. Fabrication of the VDMHP was accomplished by first establishing a series of grooves in a silicon wafer. Orientation dependent etching (ODE) using a KOH-1-propanol-[H.sub.2]O solution on a (100) wafer with a (111) fiat covered with an oxide mask, resulted in grooves 25 [[micro]meter] wide and 25 [[micro]meter] deep with sharp, perpendicular edges. The wafers were predeposited with a layer of chromium followed by a layer of gold to improve the adhesion characteristics. Dual electron beam vapor deposition, followed by planetary process using molybdenum crucibles, were used to deposit copper 31.5-33.0 [[micro]meter] thick, and provide complete closure of the grooves. A glass cover slip was bonded on the top of the deposited layer. The grooves were finally charged and sealed. A computer model Simulation and Modeling of Evaporated Deposition Profiles (SAMPLE) was used to optimize the metal step coverage and successfully predict the cross-sectional profile of the VDMHP.

A two-phase thermosyphon system was developed for cooling power devices having high heat fluxes, such as thyristas. The system utilizes an inert dielectric fluorocarbon as the heat-transfer medium, effecting heat transfer via boiling and condensation. The thermosyphon system demonstrated a maximum cooling capacity of 3 kW per power device.

A comparison of the cooling effect of a microconfigured heat sink of differing channel widths, based on pool boiling, indicates that decreasing relative channel widths result in less cooling power, until a point is reached where the thermosyphon effect begins to manifest itself. The thermosyphon effect helps to draw cooling fluid through the heat sink thereby improving heat transfer performance.

The cooling behavior of a heat sink with plate fins for a multichip module was determined through experiment and numerical analysis, and nodal network analysis. The cooling behavior, calculated using nodal network analysis, was found to be in good agreement with the results obtained experimentally.

Cooling systems for electronic equipment can be designed using computational fluid dynamics (CFD) with as few as eight cells in the heat sink. A comparison was made between the coarse and detailed CFD modeling of a finned heat sink, both with identical dimensions and boundary conditions but differing in the number of cells and in the representation of the heat sink. Performance was compared of the two CFD models with experimental results indicating good agreement between them.

The conjugated heat transfer problem caused by a thin flush heat source mounted on a conductive substrate is solved by a new formulation. The formulation involves a geometry which consists of a paradigm for direct air cooling of components on the conducting boards. The thermal field in the air cooling board are estimated by the application of printed in circuit board algorithms.

A new methodology and analysis is proposed for the development of the heatsink adhesive attachment strategy into the manufacturing process of semiconductor devices. Semiconductor devices exhibit a high risk of cracking during the manufacturing process. This high risk is caused by the stress produced by the coefficient of Thermal Expansion (CTE) mismatch occurring in the semiconductor packages. The new methodology involves the use of Low Modulus Adhesive (LMA).

The thermal characterization of the Tape Carrier Package (TCP) involves the consideration of the unenhanced performance of the TCPs. The performance of a 20 millimeter TCP on 8 layer boards is found to be 19 degree C/W. The package thermal resistance is 2 degree C/W. The addition of thermal bias with the use of low profile heat sinks enhances the thermal performance in accordance with the requirements for mobile computing systems.

A junction-to-liquid resistance can be achieved by a low profile 3-d multichip, module is less than 2.0 C/W for liquid flow rates which are less than 0.10 gpm. The use of miniature liquid-cooled heat sinks provide a junction-to-liquid resistances of 0.6 c/w and lesser values. The heat capacity rate of the liquid in both cases is increased significantly by the MicroPCM used in the process. This facilitates the production of several multi-chip modules.

Single-drift GaAs TUNNETT diodes were mounted on diamond heat sinks for improved thermal resistance and evaluated around 100 GHz in a radial line full height waveguide cavity. The diodes were fabricated from MBE-grown material originally designed for diodes that operate in CW mode around 100 GHz on integral heat sinks. An RF output power of more than 70 mW with a corresponding dc to RF conversion efficiency of 4.9% was obtained at 105.4 GHz. This is the first successful demonstration of GaAs TUNNETT diodes mounted on diamond heat sinks. To the authors' knowledge, these dc to RF conversion efficiencies and RF power levels are the highest reported to date from TUNNETT diodes and exceed those of any single discrete device made of group III-V materials (GaAs, InP, etc.) at this frequency. Free-running TUNNETT diode oscillators exhibit clean spectra with an excellent phase noise of less than -94 dBc/Hz, measured at a frequency off-carrier of 500 kHz and an RF output power of 40 mW.

Single-drift GaAs TUNNETT diodes on integral heat sinks with RF power levels up to 40 mW at 102.33 GHz exhibit no sign of saturation in RF output power or efficiency and are thought to he thermally limited. Therefore, diodes from the same MBE grown material were fabricated using a different selective etching technology and mounted on diamond heat sinks for improved heat dissipation. RF output power levels of up to 95 mW with corresponding dc-to-RF conversion efficiencies of 5.85% were measured at 104.16 GHz. To further increase the available RF output power, two TUNNETT diodes at a time were power combined using two radial line full-height waveguide cavities. The combined RF output power was 46 mW at 102.3 GHz from two diodes on integral heat sinks and 142 mW at 103.87 GHz from two diodes on diamond heat sinks with corresponding combining efficiencies of 80% and more. This is the first successful demonstration of power combining with TUNNETT diodes and the power levels and efficiencies from either single or combined diodes are the highest reported to date from any devices made of III-V materials (eg., GaAs and InP). Single diodes in second-harmonic mode yielded RF power levels of 0.57 mW at 219.7 GHz and 0.19 mW at 235.7 GHz.

A silicon chip heat loss measurement model is tested for 'thermal via' and 'heat sink conditions' to gauge its effectiveness for use in the design of a high-speed, high-density module. The boundary conditions for the heat transfer coefficient and the thermal conductivity coefficients in the calculations improve the model's precision. Multi-chip module detailing is different because of compound materials in the module.

The electromagnetic radiation from a VLSI chip package and heatsink structure is analyzed by means of the finite-difference time-domain (FDTD) technique. The dimensions of a typical configuration calls for a multizone gridding scheme in the FDTD algorithm to accommodate fine grid cells in the vicinity of the heatsink and package cavity and sparse gridding in the remainder of the computational domain. The issues pertaining to the effects of the heatsink in influencing the overall radiating capacity of the configuration are addressed. Analyses are facilitated by using simplified heatsink models and by using dipole elements as sources of electromagnetic energy to model the VLSI chip. The potential for enhancement of spurious emissions by the heatsink structure is illustrated. For heatsinks of typical dimensions, resonance is possible within the low gigahertz frequency range. The exploitation of the heatsink as an emissions shield by appropriate implementation schemes is discussed and evaluated.

A dimensionless framework is used in introducing fluid dynamical equations and formulas for conductive and convective heat diffusion in a heat sink with either turbulent or laminar flow. A method for computing the equations to derive the optimal heat sink with the minimum thermal resistance is also given. The results are then employed to examine other heat dissipators in terms of constraints on the flow, fin thickness to channel width ratio and the fluid channel's aspect ratio.

The design and analysis of a liquid cooling system is presented as a measure of the possible innovations attainable for multichip packages in nonstationary electronic equipment with a high heat flux. The proposed system consists of a fluid expansion cavity, a liquid-to-air heat exchanger, a fan and a pump. Experimental results on its thermal performance indicate a heat dissipation capability of 274 W and a thermal resistance of 0.19 degrees Celsius per W.

Work on extending the Fourier series/integral closed technique used in thermal analysis programs is reported. The extensions consider the thermal interface resistance between an integrated circuit package and a circuit board and also that between the package and a local ambient. The proposed method incorporates lumped parameter thermal resistances to the original boundary value problem and may be used as a heat dissipation design tool.

The design, manufacture and performance of laser diode array heatsinks is presented. Based on laminar flow microchannel cooling technology, the heatsink consists of diode bars individually fastened to chip carriers which are then attached to a back plane cooler. It thus maintains a low thermal impedance and efficiency for the cooling liquid's circulation. A proposed architecture for large two-dimensional laser diode arrays is also shown.

A study was conducted on the strongly positive temperature dependence of diamond-based heat sink paste thermal conductivity. The n-decane/diamond interface phononscattering was found to cause a finite interfacial thermal conductance that was highly positive temperature dependent. Results also show that the enhancement of diamond particle size will increase thermal conductivity and reduce dependence on positive temperature.

Conventional microheat sink design primarily focuses on the use of continuous fin arrays to optimally dissipate thermal energy from electronic components. By contrast, this paper experimentally measures the thermal and structural performance of two micro pin fin heat sinks designed for use in load bearing applications such as mechanical seals and thrust bearings. One pin fin array is of low porosity, which is more optimal for load bearing capacity, and the other is of high porosity, which is more optimal for heat dissipation. By using these two extreme cases, the thermal-structural tradeoff found in load bearing microheat sinks is demonstrated. The heat sinks are constructed of nickel, electrodeposited onto a stainless steel thrust ring using a modified LIGA technique. Under forced air cooling, the thermal performance of each is compared to a simple model based on a combination of macroscale pin fin heat sink results and classical correlations for fins in cross flow. The low porosity design is also tested under the application of a 44.5 N thrust load at 2500 rpm and found to be structurally sound. Experimental temperature profiles demonstrate a substantial benefit of the microheat sink in cooling the load bearing surface. [601] Index Terms--Forced air cooling, mechanical seals, microheat exchanger, microheat sink, thrust bearings.

Micromechanical cantilevers are commonly used for detection of small forces in microelectromechanical sensors (e.g., accelerometers) and in scientific instruments (e.g., atomic force microscopes). A fundamental limit to the detection of small forces is imposed by thermomechanical noise, the mechanical analog of Johnson noise, which is governed by dissipation of mechanical energy. This paper reports on measurements of the mechanical quality factor Q for arrays of silicon-nitride, polysilicon, and single-crystal silicon cantilevers. By studying the dependence of Q on cantilever material, geometry, and surface treatments, significant insight into dissipation mechanisms has been obtained. For submicron-thick cantilevers, Q is found to decrease with decreasing cantilever thickness, indicating surface loss mechanisms. For single-crystal silicon cantilevers, significant increase in room temperature Q is obtained after 700 [degrees] C heat treatment in either [N.sub.2] or forming gas. At low temperatures, silicon cantilevers exhibit a minimum in Q at approximately 135K, possibly due to a surface-related relaxation process. Thermoelastic dissipation is not a factor for submicron-thick cantilevers, but is shown to be significant for silicon-nitride cantilevers as thin as 2.3/ [micro]m. [434] Index Terms--Cantilever, force sensor, mechanical dissipation, micromechanical resonator, quality factor, surface losses.