Modeling of the Power Cycling Performance of a Si on Si Flip Chip Assembly

Flip Chip (FC) technology offers many advantages over conventional surface mount technology, including a smaller device footprint and higher interconnection density. Low power but complex consumer items, such as mobile telecommunications devices, utilise this packaging technology and it is likely to spread to other electronics sectors where components have higher power dissipations and/or they have to operate in a hostile environment. As the scope for FC packaging broadens, a reliable means of establishing the long term performance of a particular package is necessary. Traditionally thermal cycling has been a primary reliability test for electronic assemblies including FC, however this fails to capture the behaviour of assemblies where the component thermal expansion is well matched to that of the substrate due to the isothermal heating and cooling of the assembly. In this situation power cycling offers an alternative means of determining the module performance. This paper describes the use of Finite Element Modeling (FEM) to explore the effects of power cycling on a silicon on silicon Multi-Chip Module (MCM) constructed with a low solder joint standoff height of 30-35µm. Particular attention was given to the boundary conditions that are inevitably atypical of those used in traditional thermal cycling. The paper presents results of the temperature distributions throughout the assembly, which were found to depend upon the substrate base material (FR4 or copper) that the MCM was attached to. The results of the FEM analysis were verified by assembling test devices and measuring their temperature distribution under steady state and power cycling conditions. The predicted temperatures may then be used as boundary conditions in FEM of thermal stresses and fatigue in the assembly

Evaluating the most common mutation in BRCAI and BRCA2 genes in women who had mothers with brest cancer and controls

Background and purpose: Breast Cancer is one of the health problems in every population. The aim of this study was to determine the frequency of BRCA1 and BRCA2 common mutations in women whose mothers were diagnosed with breast cancer. Materials and methods: A case�control study was performed in 109 females (less than 40 years of age) who had mothers with breast cancer. For scanning of genomic mutations in BRCA1 and BRCA2, genes mutation analysis was done in BRCA1 (exon2, 20) and BRCA2 (exon11) using Real Time PCR test. We also studied 109 healthy controls without family history of breast cancer. Results: No any mutation was found in this population. Conclusion: This study showed no mutation in affected and control group. Therefore, other mutations and genes may have a role in breast cancer pathogenesis in our population. © 2016, Mazandaran University of Medical Sciences. All rights reserved

Effect of Covalent Functionalisation on Thermal Transport Across Graphene-Polymer Interfaces

This paper is concerned with the interfacial thermal resistance for polymer composites reinforced by various covalently functionalised graphene. By using molecular dynamics simulations, the obtained results show that the covalent functionalisation in graphene plays a significant role in reducing the graphene-paraffin interfacial thermal resistance. This reduction is dependent on the coverage and type of functional groups. Among the various functional groups, butyl is found to be the most effective in reducing the interfacial thermal resistance, followed by methyl, phenyl and formyl. The other functional groups under consideration such as carboxyl, hydroxyl and amines are found to produce negligible reduction in the interfacial thermal resistance. For multilayer graphene with a layer number up to four, the interfacial thermal resistance is insensitive to the layer number. The effects of the different functional groups and the layer number on the interfacial thermal resistance are also elaborated using the vibrational density of states of the graphene and the paraffin matrix. The present findings provide useful guidelines in the application of functionalised graphene for practical thermal management.Comment: 8 figure

Graphene -- Based Nanocomposites as Highly Efficient Thermal Interface Materials

We found that an optimized mixture of graphene and multilayer graphene - produced by the high-yield inexpensive liquid-phase-exfoliation technique - can lead to an extremely strong enhancement of the cross-plane thermal conductivity K of the composite. The "laser flash" measurements revealed a record-high enhancement of K by 2300 % in the graphene-based polymer at the filler loading fraction f =10 vol. %. It was determined that a relatively high concentration of single-layer and bilayer graphene flakes (~10-15%) present simultaneously with thicker multilayers of large lateral size (~ 1 micrometer) were essential for the observed unusual K enhancement. The thermal conductivity of a commercial thermal grease was increased from an initial value of ~5.8 W/mK to K=14 W/mK at the small loading f=2%, which preserved all mechanical properties of the hybrid. Our modeling results suggest that graphene - multilayer graphene nanocomposite used as the thermal interface material outperforms those with carbon nanotubes or metal nanoparticles owing to graphene's aspect ratio and lower Kapitza resistance at the graphene - matrix interface.Comment: 4 figure

Open Access Repository-Scale Propagated Nearest Neighbor Suspect Spectral Library for Untargeted Metabolomics

Abstract Despite the increasing availability of tandem mass spectrometry (MS/MS) community spectral libraries for untargeted metabolomics over the past decade, the majority of acquired MS/MS spectra remain uninterpreted. To further aid in interpreting unannotated spectra, we created a nearest neighbor suspect spectral library, consisting of 87,916 annotated MS/MS spectra derived from hundreds of millions of public MS/MS spectra. Annotations were propagated based on structural relationships to reference molecules using MS/MS-based spectrum alignment. We demonstrate the broad relevance of the nearest neighbor suspect spectral library through representative examples of propagation-based annotation of acylcarnitines, bacterial and plant natural products, and drug metabolism. Our results also highlight how the library can help to better understand an Alzheimer’s brain phenotype. The nearest neighbor suspect spectral library is openly available through the GNPS platform to help investigators hypothesize candidate structures for unknown MS/MS spectra in untargeted metabolomics data

Determination and simulation of the heat transfer characteristics of electronic assemblies

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN020197 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Thermal And Thermo-Mechanical Modelling of Polymer Overmoulded Electronics

This paper reports on the results from a research project investigating a novel technology for the manufacture of recyclable polymeric modules with embedded electronic controls and power distribution. The aim of this project is to develop a technology that fully encapsulates electronics for use in the demanding automotive environment. A two shot moulding technology will protect delicate electronic circuitry mounted outside of the passenger compartment from extremes of temperature, vibration and humidity. The resultant assemblies will also be readily recyclable, making it possible to cost-effectively separate electronic components from the polymer at the end of vehicle life, allowing the recovery of high purity recyclate

Failure mechanisms of dummy IGBT assembles constructed using liquid In-Sn/Nb system

Liquid solder joints have previously been proposed in order to improve the reliability of solder joints in general, and especially for those that are operated at elevated temperatures. The solder is designed to melt during high temperature operation, releasing the stresses on the joint. The component will remain mechanically attached to the substrate by use of a polymer underfill or glob-top. Assemblies of dummy insulated gate bipolar transistor (IGBT) devices were constructed using the In-Sn as a low melting point solder and Nb as a barrier layer, on both device bond pads and connecting wires. Silicone and epoxy based adhesives were used as glob top materials, and alumina was used as the substrate. Thermal cycling carried out between -20 and +125 °C lead to rapid joint failure, and analysis of the joints showed that the wires had moved under mechanical tests. Further testing is underway