Thermal deformation measurement of the solder joints in electronic packages using electron moiré method

In this paper, electron moiré method is used to measure the thermal deformation of electronic packages. In order to observe the electron moiré fringe, a holographic grid was replicated on the cross section of the BGA type package at 150°C. This grid was fabricated on a glass plate using a moving point holographic system, and was replicated to measured area at high temperature. Under SEM, the holographic grid(specimen grid) and a programmed electron beam scan(master grid) interfere and form electron moiré patterns. The shear strain measurement technique using electron moiré method is described. Using the electron moiré method, the shear strains in the different solder joints were measured and analysed. Some useful results were obtained.     

Application of moiré technique in the stress analysis of cutting tools

Knowledge of the stress field in cutting tools is necessary for their strength evaluation. However, the experimental analysis of stresses in cutting tools during machining poses a number of problems in view of the steep stress gradient present. Photo-elasticity and the 'built-up tool' methods are the common techniques used for this purpose. In the present paper results on the stresses in cutting tools obtained during actual machining through the successful application of the transmitted moiré technique, are presented. In these experiments transparent epoxy tools carrying moiré gratings were used to machine commercial lead alloy at low speeds. The tool rake angle was varied. The effectiveness of moiré method, basically a displacement analysis technique, in providing useful data on tool stresses comparable with the other direct stress analysis techniques such as photo-elasticity is also discussed in the paper.     

Absolute Measurements of the Thermal Diffusivity of Aqueous Solutions of Sodium Chloride

The laser-induced thermal grating technique was used to determine the thermal diffusivity of aqueous solutions of sodium chloride. In comparison with conventional measurement methods, this noninvasive optical technique has the advantage that no sensors need to be inserted in the sample. Therefore, this technique is especially suitable for the measurement of electrically conducting and corrosive liquids. The aqueous solutions studied have weight fractions of 5, 10, 15, and 20% sodium chloride. Measurement results for the thermal diffusivity are presented for aqueous solutions of sodium chloride in the temperature range 293 to 373 K at atmospheric pressure.     

Thermophysical Characterization of Elastic Solids: A Novel Application for the Material Testing Machine

The conventional machine for the mechanical testing of materials finds a new application in thermophysical characterization of a large class of elastic solids, including metals and ceramics. A measuring technique, which is based on the thermoelastic effect and exploits a simple accessory for the testing machine, has been improved and is critically reviewed here. The technique allows the simultaneous measurement of the thermal conductivity and thermal diffusivity, the thermal expansion coefficient or alternatively the specific heat, and the Grüneisen parameter. Operational criteria for measurement and data analysis are presented and discussed. The method has been validated at room temperature using several Certified Reference Materials; its precision and accuracy turn out to be comparable to those of established methods.     

APPLICATION OF GRIDS TO PLASTICS FOR THE MOIRE FRINGE METHOD OF STRAIN MEASUREMENT

There has been considerable interest during recent years on the measurement of strain using the moiré fringe method. This report reviews the techniques of applying grids to specimens and gives details of methods used at NEL. Strain measurements on a simple tensile test specimen using the moiré mismatch technique are compared with those obtained with a Linley extenso-meter.     

Thermal Properties Measurement of Micro-electromechanical System Sensors by Digital Moire Method

Abstract:  The thermal properties of a micro-electromechanical system sensor were analysed by a novel digital moiré method. A double-layer micro-cantilever sensor (60  μ m long, 10  μ m width and 2  μ m thick) was prepared by focused ion beam milling. A grating with frequency of 5000 lines mm⁻¹ was etched on the cantilever. The sensor was placed into a scanning electron microscope system with a high temperature device. The observation and recording of the thermal deformation of the grating were realised in real-time as the temperature rose from room temperature to 300 °C at intervals of 50 °C. Digital moiré was generated by interference of the deformed grating and a digital virtual grating. The thermal properties including strain distribution of the sensor and the linear expansion coefficient of polysilicon were accurately measured by the phase-shifted moiré patterns.     

The use of strippable photographic film for moire grating production

Practical details are presented concerning the use of strippable film for the production of moiré gratings. Strippable film is produced primarily for application in graphic arts. The influence of the use of the film on the accuracy of measurement in the direct moiré method is discussed.     

Investigation of Analytical Solutions for Bonded Structures by Photomechanical Methods

Abstract:  In this paper, both photoelasticity and moiré interferometry were successively incorporated with finite element method to investigate the predicted thermal stresses and lateral displacement of bonded structures calculated from different theories. It was found that the distributions of moment and transverse force play significant roles in making different values of thermal stresses in the adherends by authors' and Suhir's 1986 theories. On the other hand, the values of lateral displacement obtained from different theories are almost identical.     

Determination of Residual Stresses by Thermal Relaxation and Speckle Correlation Interferometry

ABSTRACT:  A new technique for the measurement of residual stresses is presented. The technique is based on strain measurements following thermal stress relaxation. The heat input is supplied by a low power infrared laser and the strain is measured with speckle pattern correlation interferometry. This paper presents a comprehensive overview of the technique and an example of how it has been applied in a practical situation.     

New Photopyroelectric Technique for Precise Measurements of the Thermal Effusivity of Transparent Liquids

A new photopyroelectric methodology for thermal effusivity measurements in transparent liquids is presented. The new methodology involves the thermally thick limit of the pyroelectric signal in the standard front-surface configuration. A signal normalization procedure, which avoids the conventional requirement for transfer function determination, is implemented. The thermal effusivity of five liquids was measured by means of this technique, and very good agreement was found with corresponding values reported in the literature.     

Thermal expansion of glasses in the solid and liquid phases

In this study, the thermal expansion of a number of mixed oxide glasses was measured in the solid and liquid regions by gamma densitometry. Conventional density measurement techniques are limited to either the solid or the liquid phase; however, with this noncontacting technique, the density and thermal expansion of both the solid and the liquid phases may be investigated as the temperature is varied and the glass viscosity varies over a wide range. This technique allows the continuous measurement of density as the liquid cools to a supercooled glass or to a crystalline solid. Lead borate glasses were examined in the range 27 to 42 mol % PbO. The liquid-phase volumetric thermal expansion coefficient was observed to decrease with increasing PbO content, in contrast to the solid-phase linear thermal expansion coefficients. In soda-baria phosphate glasses (50 mol% P₂O₅), liquid-phase volumetric expansion coefficients were found to vary as the solid-phase linear expansion coefficients. Measurements on a lithia-aluminoscilicate glass ceramic were obtained by this method to approximately 400°C above the limit of conventional dilatometry. The gamma densitometry technique can yield density, thermal expansion, glass transition and crystallization information, and quenching-rate dependence data on glasses to temperatures in excess of 1500°C, and thus provides a means for high-temperature characterization of glasses which complements conventional dilatometry, calorimetry, and thermal analysis.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

A single exposure reflection moiré interferometric technique for complete curvature analysis of bent plates

Most known moiré methods need to be repeated three times for getting curvature information in three different in plane directions, for the complete analysis. To overcome this difficulty, a new single exposure moiré interferometric technique is proposed that maps completely partial curvature contours in three different directions of laterally loaded specularly reflecting plate models. Converging HeNe laser light is diffracted by a lens plane cross grating. The 00, + 10 and the +01 diffraction orders are permitted through the Fourier transform (FT) plane and collimated to illuminate the plate model. The reflected light from the loaded model records the model with the inherent deformed interferometric cross grating superimposed on it. A posteriori Fourier filtering of the developed recording (moirégram) gives partial curvature contours pertaining to three different in plane directions from which the principal curvatures and the principal directions are obtained. Also, this technique, being a single exposure technique, has the potential for complete bending analysis of plates subjected to lateral impact loading and destructive loading applications, where the repeatability of the event may not be possible.     

Curvature contours of flexed plates by a multiple illumination moiré shearing interferometer

A new moiré method is proposed to map partial slope, partial curvature and twist curvature contours of laterally loaded specularly reflecting plate models. Converging HeNe laser light is diffracted by a lens plane cross grating, different combinations of orders are selectively permitted through the Fourier transform plane and collimated to illuminate the plate model. This technique eliminates the difficulties involved in Fourier filtering in the imaging optics, thereby extending the reflection moiré' interferomelry to general plate structures and loading. The slope contours are obtained still by double exposure.     

Multidimensional Flash Diffusivity Measurements of Orthotropic Materials

A generalization of the radial flash technique is presented whereby the thermal diffusivity of an orthotropic solid is measured in directions parallel and perpendicular to the flash source. The theoretical formulation is based on a Green's function approach which assumes a general orthotropic solid with three mutually orthogonal thermal diffusivities (or conductivities). Using this approach, a solution to this problem is presented which can be used to develop solutions for arbitrary pulse waveforms and incident geometries. Analytical and numerical results are presented for two-dimensional and three-dimensional cases of finite and semiinfinite solids. Characteristic equations which describe the ratio of the temperatures at two points along a principal axis are given. The equations show excellent agreement with numerical predictions as well as experimental results. A parameter estimation approach is given which improves on the accuracy of the radial flash technique in the determination of thermal diffusivity from experimental data.     

A RAPID METHOD FOR CALCULATING THE TRANSVERSAL STRAIN IN THE MOIRE TECHNIQUE ALONG SECTIONS OF SYMMETRY

An approximate rapid method is described for calculating in the moiré technique the transversal strain directly from the longitudinal strain distribution across sections of symmetry. The method is based on evaluation of the load transmitted through the section and is corroborated by two examples.     

Low-Contrast Thermal Resolution Test Targets: A New Approach

A new type of thermal resolution test target optimized to minimize the effects of lateral thermal gradients at low thermal contrast is described. This target consists of thin-film inconel heater strips over an etched silica substrate bonded to an aluminum heat sink. A simple, finite-difference model is used to study how variations in target construction and materials affect the generated thermal resolution test pattern. The construction, testing, and use of this type of target to extend the lower end of the contrast range of a conventional target are described.     

TRIANGULAR AND v 2 GRATINGS FOR THE MOIRÉ TECHNIQUE

Methods for constructing two new types of grating for the moiré technique are described, their use is illustrated in application to a simple beam, and the range of measurable strains is established. In certain circumstances the use of these gratings presents a means of accurate analysis without recourse to elaborate equipment.     

Measurement of the thermal diffusivity of molten KCl up to 1000°C by the forced Rayleigh scattering method

This paper describes measurement of the thermal diffusivity of molten KCl in the temperature range from 804 to 1030°C by the forced Rayleigh scattering method. In this contact-free optical measuring technique for the thermal diffusivity of liquids, a sample needs to be colored by the admixture of a dye for suitable absorption of a heating laser beam. The dye substances employed are CoCl₂ and NiCl₂, which were chosen through the experimental evaluation. The accuracy is estimated to be ±7% for molten KCl colored with NiCl₂. The results converted to thermal conductivity show one of the smallest values among other previous data; the difference is a factor of four. The present study demonstrates the promising applicability of the forced Rayleigh scattering method to the measurement of high-temperature molten salts, which has never be attained by other conventional methods.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

Thermal Diffusivity Measurements on Insulation Materials with the Laser Flash Method

An iterative approach is adopted to determine the thermal diffusivity of the xonotlite-type calcium silicate insulation material with very low thermal conductivity. The measurements were performed with a conventional laser flash apparatus by rear-face detection of the temperature response of the three-layered sample, where the insulating material is sandwiched between two iron slices. In the evaluation of the thermal conductivity, the theoretical curve is fitted to the complete temperature–time curve, instead of just using the t _1/2 point. The theoretical model is based on the thermal quadrupole method. The nonlinear parameter estimation technique is used to estimate simultaneously the thermal diffusivity, heat transfer coefficient, and absorbed energy. Based on experimental results, the optimal thickness range of the insulation material in the sample is indicated as 1.6 to 1.9 mm. The effects of the uncertainties of the thicknesses, contact resistance, and thermophysical properties of the three layers on the measurement uncertainty are estimated, giving an overall uncertainty in the thermal conductivity of approximately 7.5%.Paper presented at the Seventh Asian Thermophysical Properties Conference, August 23–28, 2004, Hefei and Huangshan, Anhui, P. R. China.