scholarly journals Thermal Conductivity Measurements on Polysilicon Microbridges Using the 3-Omega Technique

2008 ◽  
Author(s):  
Patrick E. Hopkins ◽  
Leslie M. Phinney
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Polycrystalline Silicon ◽  
Microelectromechanical Systems ◽  
Boundary Resistance ◽  
Mems Devices ◽  
Conductivity Measurements ◽  
3 Omega ◽  
3Ω Technique

The thermal properties of microelectromechanical systems (MEMS) devices are governed by the structure and composition of the constituent materials as well as the geometrical design. With the continued reduction of the characteristic sizes of these devices, experimental determination of the thermal properties becomes more difficult. In this study, the thermal conductivity of polycrystalline silicon (polysilicon) microbridges are measured with the transient 3ω technique and compared to measurements on the same structures using a steady state joule heating technique. The microbridges with lengths from 200 microns to 500 microns were designed and fabricated using the Sandia National Laboratories SUMMiT™ V surface micromachining process. The differences between the two measurements, which arise from the geometry of the test structures, are explained by bond pad heating and thermal boundary resistance effects.

Thermal Conductivity Measurements on Polycrystalline Silicon Microbridges Using the 3ω Technique

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Patrick E. Hopkins ◽  
Leslie M. Phinney
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Polycrystalline Silicon ◽  
Microelectromechanical Systems ◽  
Experimental Methods ◽  
Electrical Contacts ◽  
Conductivity Measurements ◽  
Advantages And Disadvantages ◽  
3Ω Technique

The thermal performance of microelectromechanical systems devices is governed by the structure and composition of the constituent materials as well as the geometrical design. With the continued reduction in the characteristic sizes of these devices, experimental determination of the thermal properties becomes more difficult. In this study, the thermal conductivity of polycrystalline silicon (polysilicon) microbridges are measured with the transient 3ω technique and compared with measurements on the same structures using a steady state Joule heating technique. The microbridges with lengths from 200 μm to 500 μm were designed and fabricated using the Sandia National Laboratories SUMMiT V™ surface micromachining process. The advantages and disadvantages of the two experimental methods are examined for suspended microbridge geometries. The differences between the two measurements, which arise from the geometry of the test structures and electrical contacts, are explained by bond pad heating and thermal resistance effects.

scholarly journals Measuring thermal conductivity of soils under laboratory conditions.

1969 ◽  
Vol 17 (1) ◽  
pp. 71-79
Author(s):  
A.I. Golovanov
Keyword(s):  
Thermal Conductivity ◽  
Flow Velocity ◽  
Soil Sample ◽  
Water Flow ◽  
Coarse Sand ◽  
Conductivity Measurements ◽  
Soil Layers ◽  
The Real ◽  
Real Flow

Experiments were made to determine the influence of size of soil sample, convection and water flow on the determination of thermal conductivity of soils using a thin needle (0.05 cm radius, 8.5 cm in length) as the heating element and copper cylinders for sample containers. For measurements during a period of 100 seconds the diameter of the sample must be at least 4 cm and to avoid any influence of convection measurements should not exceed 100 seconds. When heating elements are placed horizontally to measure simultaneously the thermal conductivity of different soil layers they should be placed at least 10 cm apart. Thermal conductivity measurements could be used to determine flow velocities of water in coarse sand samples provided that the real flow velocity was highev than 0.35 cm/ min. (Abstract retrieved from CAB Abstracts by CABI’s permission)

A Renewal Weakest-Link Model of Strength Distribution of Polycrystalline Silicon MEMS Structures

2019 ◽  
Vol 86 (8) ◽  
Author(s):  
Zhifeng Xu ◽  
Roberto Ballarini ◽  
Jia-Liang Le
Keyword(s):  
Experimental Data ◽  
Polycrystalline Silicon ◽  
Microelectromechanical Systems ◽  
Strength Distribution ◽  
Material Strength ◽  
Mems Devices ◽  
Efficient Computation ◽  
Weakest Link ◽  
Large Size ◽  
The Stability

Experimental data have made it abundantly clear that the strength of polycrystalline silicon (poly-Si) microelectromechanical systems (MEMS) structures exhibits significant variability, which arises from the random distribution of the size and shape of sidewall defects created by the manufacturing process. Test data also indicated that the strength statistics of MEMS structures depends strongly on the structure size. Understanding the size effect on the strength distribution is of paramount importance if experimental data obtained using specimens of one size are to be used with confidence to predict the strength statistics of MEMS devices of other sizes. In this paper, we present a renewal weakest-link statistical model for the failure strength of poly-Si MEMS structures. The model takes into account the detailed statistical information of randomly distributed sidewall defects, including their geometry and spacing, in addition to the local random material strength. The large-size asymptotic behavior of the model is derived based on the stability postulate. Through the comparison with the measured strength distributions of MEMS specimens of different sizes, we show that the model is capable of capturing the size dependence of strength distribution. Based on the properties of simulated random stress field and random number of sidewall defects, a simplified method is developed for efficient computation of strength distribution of MEMS structures.

scholarly journals Determination of thermal properties of some ceiling material commonly used in Ijebu- Ode, Nigeria

2020 ◽  
Vol 9 (1) ◽  
pp. 23-27
Author(s):  
J.O. Adepitan ◽  
F.O. Ogunsanwo ◽  
J.D. Ayanda ◽  
A.A. Okusanya ◽  
A.D. Adelaja ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Tropical Rainforest ◽  
Building Construction ◽  
Thermal Resistivity ◽  
Electrical Method ◽  
Insulating Materials ◽  
Insulating Material ◽  
Range Of Values

The study investigates the thermal properties of different insulating material used in building construction in Ijebu Ode, a tropical rainforest region, south western, Nigeria. Five insulating material; asbestos, Plaster of Paris (P.O.P), PolyVinyl Chloride (PVC), hardboard and paperboard, were subjected to thermal investigation using Lee’s disc electrical method. The result obtained showed that the thermal conductivities obtained are within the range of values specified for good insulating materials. Asbestos was found to be associated with the least thermal conductivity of the value 𝟎. 𝟏𝟕𝟏𝟕 𝑾𝒎-𝟏𝑲-𝟏while PVC had the highest thermal conductivity values of 𝟏. 𝟔𝟒𝟗𝟗 𝑾𝒎-𝟏𝑲-𝟏. This may be associated with the temperature and the heat flux on the surface of the material. The results obtained for thermal conductivity, thermal resistivity and thermal diffusivity correlated favourably when compared with those of previous work from other locations. Asbestos being the material with the lowest thermal conductivity is therefore recommended for use as the suitable insulating ceiling material in the study area. Keywords: thermal conductivity, diffusivity, resistivity, Lee’s disc

Automatic thermal conductivity measurements with 3-omega technique

2019 ◽  
Vol 90 (2) ◽  
pp. 024904 ◽  
Author(s):  
D. A. Chernodoubov ◽  
A. V. Inyushkin
Keyword(s):  
Thermal Conductivity ◽  
Conductivity Measurements ◽  
3 Omega

Wafer-Level Strength and Fracture Toughness Testing of Surface-Micromachined MEMS Devices

1999 ◽  
Vol 605 ◽  
Author(s):  
H. Kahn ◽  
N. Tayebi ◽  
R. Ballarini ◽  
R.L. Mullen ◽  
A.H. Heuer
Keyword(s):  
Fracture Toughness ◽  
Tensile Strength ◽  
Microelectromechanical Systems ◽  
Reliability Prediction ◽  
Bend Strength ◽  
Mems Devices ◽  
Wafer Level ◽  
Toughness Testing ◽  
Loading Devices

AbstractDetermination of the mechanical properties of MEMS (microelectromechanical systems) materials is necessary for accurate device design and reliability prediction. This is most unambiguously performed using MEMS-fabricated test specimens and MEMS loading devices. We describe here a wafer-level technique for measuring the bend strength, fracture toughness, and tensile strength of MEMS materials. The bend strengths of surface-micromachined polysilicon, amorphous silicon, and polycrystalline 3C SiC are 5.1±1.0, 10.1±2.0, and 9.0±1.0 GPa, respectively. The fracture toughness of undoped and P-doped polysilicon is 1.2±0.2 MPa√m, and the tensile strength of polycrystalline 3C SiC is 3.2±1.2 GPa. These results include the first report of the mechanical strength of micromachined polycrystalline 3C SiC.

Thermal Properties of Thin Metallic Layer Deposited on Insulators: Effect of the Interface on the Independent Determination of the Thermal Diffusivity and Conductivity of the Layer

2008 ◽  
Author(s):  
Danie`le Fournier ◽  
Jean Paul Roger ◽  
Christian Fretigny
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Thermal Resistance ◽  
Thermal Contact ◽  
Heat Diffusion ◽  
Metallic Layer ◽  
Good Thermal Contact ◽  
Lateral Heat

Lateral heat diffusion thermoreflectance is a very powerful tool for determining directly the thermal diffusivity of layered structures. To do that, experimental data are fitted with the help of a heat diffusion model in which the ratio between the thermal conductivity k and the thermal diffusivity D of each layer is fixed, and the thermal properties of the substrate are known. We have shown in a previous work that it is possible to determine independently the thermal diffusivity and the thermal conductivity of a metallic layer deposited on an insulator, by taking into consideration all the data obtained at different modulation frequencies. Moreover, it is well known that to prevent a lack of adhesion of a gold film deposited on substrates like silica, an intermediate very thin (Cr or Ti) layer is deposited to assure a good thermal contact. We extend our previous work: the asymptotic behaviour determination of the surface temperature wave at large distances from the modulated point heat source for one layer deposited on the substrate to the two layers model. In this case (very thin adhesion coating whose thermal properties and thickness are known), it can be establish that the thermal diffusivity and the thermal conductivity of the top layer can still be determined independently. It is interesting to underline that the calculus can also be extended to the case of a thermal contact resistance which has often to be taken into account between two solids. We call thermal resistance a very thin layer exhibiting a very low thermal conductivity. In this case, the three parameters we have to determine are the thermal conductivity and the thermal diffusivity of the layer and the thermal resistance. We will show that, in this case, the thermal conductivity of the layer is always obtained independently of a bound of the couple thermal resistance – thermal diffusivity, the thermal diffusivity being under bounded and the thermal resistance lower bounded. Experimental results on thin gold layers deposited on silica with and without adhesion layers are presented to illustrate the method. Discussions on the accuracy will also be presented.

A Self-Heated Thermistor Technique to Measure Effective Thermal Properties From the Tissue Surface

1987 ◽  
Vol 109 (4) ◽  
pp. 330-335 ◽  
Author(s):  
P. A. Patel ◽  
J. W. Valvano ◽  
J. A. Pearce ◽  
S. A. Prahl ◽  
C. R. Denham
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Properties ◽  
Tissue Blood Flow ◽  
Conductivity Measurements ◽  
Bioheat Equation ◽  
Tissue Conductivity ◽  
Diffusivity Measurements ◽  
Tissue Surface ◽  
Effective Thermal Properties

A microcomputer based instrument to measure effective thermal conductivity and diffusivity at the surface of a tissue has been developed. Self-heated spherical thermistors, partially embedded in an insulator, are used to simultaneously heat tissue and measure the resulting temperature rise. The temperature increase of the thermistor for a given applied power is a function of the combined thermal properties of the insulator, the thermistor, and the tissue. Once the probe is calibrated, the instrument accurately measures the thermal properties of tissue. Conductivity measurements are accurate to 2 percent and diffusivity measurements are accurate to 4 percent. A simplified bioheat equation is used which assumes the effective tissue thermal conductivity is a linear function of perfusion. Since tissue blood flow strongly affects heat transfer, the surface thermistor probe is quite sensitive to perfusion.

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