Bond Layer Properties and Geometry Effect on Interfacial Thermo-mechanical Stresses in Bi-material Electronic Packaging Assembly

Thermo-mechanical mismatch stress is one of the reasons for mechanical as well as functional failure between two or more connected devices. In electronic packaging, two or more plates or layers are bonded together by an extremely thin layer. This thin bonding layer works as an interfacial stress compliance which is expected to alleviate the interfacial stresses between the layers. Therefore, it is very important to identify the suitable interfacial bonding characteristics for reducing the interfacial thermal mismatch stresses to maintain the structural integrity. This research work examines the influences of bond layer properties and geometry on the interfacial shearing and peeling stresses in a bi-material assembly. In this study a closed form model of bi-layered assembly is used with the up-to-date bond layer shear stress compliance expression. The key bond layer properties namely Young's modulus, coefficient of thermal expansion, Poisson's ratio, and physical parameters like temperature and thickness are considered for interfacial stress evaluation. It is observed that the Young's modulus, the thickness and the temperature of the bond layer have significant influence on the interfacial shearing and peeling stress. The results obtained are likely to be useful in designing bond layer properties in microelectronics and photonics applications

Material Selection for Interfacial Bond Layer in Electronic Packaging

In electronic packaging, typically two or more thin dissimilar plates or layers are bonded together by an extremely thin adhesive bond layer. Electronic assemblies are usually operated under high power conditions which predictably produces a high temperature environment in the electronic devices. Therefore, thermal mismatch shear and peeling stress inevitably arise at the interfaces of the bonded dissimilar materials due to differences in Coefficient of Thermal Expansion (CTE) typically during the high temperature change in the bond process. As a result, delamination failure may occur during manufacturing, machining, and field use. As such, these thermo-mechanical stresses play a very significant role in the design and reliability of the electronic packaging assembly. Consequently, critical investigations of interfacial stresses under variable load conditions in composite structure can result in a better design of electronic packaging with higher reliability and minimize or eliminate the risk of functional failure. In order to formulize bond material selection, analytical studies are carried out in order to study the influence of bond layer parameters on interfacial thermal stresses of a given package. These parameters include Coefficient of thermal expansion (CTE), poison's ratio, temperature, thickness, and stiffness (compliant and stiff) of the bond layer. From the study, stiffness and bond layer thickness are identified as the key parameters influencing interfacial shearing and peeling stresses. The other parameters namely CTE, poisons ratio has shown insignificant influence on interfacial stresses due to the very thin section of bond layer compared to the top and bottom layers. The results also show that the interfacial stresses increases proportionally with the increase of temperature in the layers. Therefore, it is very important that the temperature is maintained as low as possible during the chip manufacturing and operating stages. Since only two parameters namely stiffness and bond layer thickness are identified as the key parameters, the interface thermal mismatch stresses can be reduced or eliminated by controlling these two parameters only. Therefore the identification of suitable bond layer parameters selection with reasonable accuracy is possible even without performing optimization process. Finally, this paper proposes a Metal Matrix Composite (MMC) bond material selection approach using rule of mixture material design. The outcome of this research can be seen in the forms of practical and beneficial tools for interfacial stress evaluation and physical design and fabrication of layered assemblies. The Engineers can utilize this research outcome in conjunction with guidelines for electronic packaging under variable thermal properties of layered composites

Themo-mechanical Interfacial Stress Analysis in Electronic Packaging at Different Temperature Conditions: Revisit Author's Work

The study of thermal mismatch induced stresses and their role in mechanical failure is one relevant topic to composite materials, photonic devices and electronic packages. Therefore, an understanding of the nature of the interfacial stresses under different temperature conditions is necessary in order to minimize or eliminate the risk of mechanical failure. An accurate estimate of thermal stresses in the interfaces plays a significant role in the design and reliability studies of microelectronic devices. In the microelectronic industry, from a practical point of view, there is a need for simple and powerful analytical models to determine interfacial stresses in layered structures. This review paper summarizes the work conducted by the authors in relation to the bi-layered assembly with different temperature conditions on the determination of interfacial thermal stresses. The authors have extended the case of uniform temperature model by earlier researchers of two layered structure to account for differential uniform temperatures, linear temperature gradient in the layers. The presence of a heat source in one layer (die) is also presented. Finally, the effect of bond material properties and geometry on interfacial stresses and bond material selection approach are also considered in a simple way

Utilization of Agro-Industrial Waste in Metal Matrix Composites: Towards Sustainability

The application of agro-industrial waste in Aluminum Metal Matrix Composites has been getting more attention as they can reinforce particles in metal matrix which enhance the strength properties of the composites. In addition, by applying these agro-industrial wastes in useful way not only save the manufacturing cost of products but also reduce the pollutions on environment. This paper represents a literature review on a range of industrial wastes and their utilization in metal matrix composites. The paper describes the synthesis methods of agro-industrial waste filled metal matrix composite materials and their mechanical, wear, corrosion, and physical properties. It also highlights the current application and future potential of agro-industrial waste reinforced composites in aerospace, automotive and other construction industries

Microstructure analysis, physical and thermal properties of Al2O3-Al2TiO5 functionally graded ceramics for the application of car brake rot

Aluminium titanate (AT) (Al 2 TiO 5) is a promising engineering material because of its low thermal expansion coefficient, excellent thermal shock resistance, good refractoriness and non-wetting with most metals. Functionally graded material (FGM) is generally a particulate composite with continuously varying volume fractions. FGMs are alternative materials for dental implants, building materials and ballistic protection. It has been of great interest to future engines, internal combustion engines, metal cutting and other high temperature engineering application. There has been a demand for an adequate disc brake that requires less maintenance in the automotive manufacturing industry. FGM, the next evolution of layered structure, consists of graded compositions that are dispersed across the ceramic which produces a gradual improvement in the properties across the ceramic at a steady pace

A parametric study: Frame analysis method for masonry arch bridges

The predictability of masonry arch bridges and their behaviour is widely considered doubtful due to the lack of knowledge about the conditions of a given masonry arch bridge. The assessment methods for masonry arch bridges are MEXE, ARCHIE, RING and Frame Analysis Method. The material properties of the masonry and fill material are extremely difficult to determine accurately. Consequently, it is necessary to examine the effect of load dispersal angle through the fill material, the effect of variations in the stiffness of the masonry, the tensile strength of the masonry mortar continuum and the compressive strength of the masonry mortar continuum. It is also important to understand the effect of fill material on load dispersal angle to determine their influence on ratings. In this paper a series of parametric studies, to examine the sensitivity of assessment ratings to the various sets of input data required by the frame analysis method, are carried out

On the problem of novel composite materials development for car brake rotor

This paper presents a study of the potential materials that are suitable for the development of the automotive brake disc. Two new materials are proposed as an alternative material to the conventionally used gray cast iron for the disc brake, which are namely Metal Matrix Composite (MMC) and Functionally Graded Material (FGM). MMCs with ceramic particulate reinforcement are found to have a low density and high thermal conductivity compared to the cast irons. Two particulate reinforcements, Al2O3 and SiC were being considered for MMC. On the other hand, FGM has demonstrated high thermal shock resistance, better wear resistance and low density. Preliminary investigation indicated that MMC acquired improved hardness property. Meanwhile, the hardness property of FGM with Al2O3 and Al2TiO5 as layered composites materials can be further improved