Jagjiwan Mittal

Ammonia Gas Sensing Using Thin Film of MnO 2 Nanofibers

Here, we describe an ammonia gas sensor comprising of thin film of octahedral molecular sieves of OMS-2 nanofibers deposited on insulation substrate having gold-coated copper electrodes. We demonstrate that the OMS-2 nanofibers can exhibit reversible changes in its electrical resistance due to the adsorption and desorption of ammonia on its acidic sites. OMS-2 exhibits high sensitivity for the ammonia gas in air.

Bulk thermal conductivity studies of Sn/SnO coated and filled multiwalled carbon nanotubes for thermal interface material

ABSTRACT Multiwalled carbon nanotubes (MWCNTs) were successfully coated and filled with Sn using a simple method. Bulk thermal conductivity of Sn/SnO filled and coated multiwalled carbon nanotubes (MWCNTs) of ∼1 mm thickness pellet by laser method reveals surge in hybrid carbon nanotubes in comparison to pristine nanotubes. The thermal diffusivity and thermal conductivity of hybrid nanotubes are increased to 4.41 mm2/sec, 5.39 Wm−1K−1 of as compared to 0.36 mm2/sec and 0.28 Wm−1K−1 of the pristine nanotubes. The enhancement in thermal conductivity is attributed to the presence of Sn coating on surface and inside the carbon nanotubes and the formation of compact structures by reducing the air gaps between nanotubes because of their joining during compression and sintering.

Zn diffusion and reflow behaviour of Sn-9Zn and Sn-8.5Zn-0.5Ag-0.01Al-0.1Ga solders on a Ni/Cu substrate under IR reflow

Purpose – This paper aims to compare the reflow and Zn diffusion behaviors in Sn-Zn and Sn-8.5Zn-0.5Ag-0.01Al-0.1Ga (5E) solders during soldering on a Ni/Cu substrate under infrared (IR) reflow. The study proposes a model on the effect of various elements particularly Zn diffusion behavior in the solders on the formation of intermetallic compounds (IMCs). Design/methodology/approach – The melting activities of two solders near their melting points on copper substrates are visualized in an IR reflow furnace. Reflowed solder joints were analyzed using scanning electron microscope and energy dispersive X-ray spectroscopy. Findings – Reflow behaviors of the solders are similar. During melting, solder balls are first merged into each other and then reflow on the substrate from top to bottom. Both solders show a reduced amount of Zn in the solder. Theoretical calculations demonstrate a higher Zn diffusion in the 5E solder; however, the amount of Zn actually observed at the solder/substrate interface is lower th...

Activities during melting and reflowing behaviour of solders

Purpose – The purpose of this paper is to visualise the activities of three solders; Sn‐37Pb, Sn‐9Zn and Sn‐3.5Ag on Cu substrates during reflow near their melting points and to relate them with reflow reactions between solder and substrate.Design/methodology/approach – Melting activities of three solders near their melting points on copper substrates are visualised in an infrared reflow furnace.Findings – Solder balls demonstrate different ways of melting and reflowing behaviours in dissimilar times and temperature intervals. Melting of Sn‐9Zn solder balls is initiated simultaneously at the surface and joint between solder balls. This is followed by the melting at the joint between solder balls and the Cu substrate. During melting, solder balls are first merged into each other and then reflow on the substrate from top to bottom. Opposite to Sn‐9Zn, Sn‐3.5Ag solder balls start to melt at the surface and the joint between the solder and substrate, simultaneously. Balls are first reflowed from top to bottom...

Carbon nanotube-based interconnections

Reductions in feature size and function integration require either replacement or modification of existing interconnect materials to fit ever advancing technology. Due to their remarkable properties, carbon nanotubes (CNTs) are selected as candidates for future interconnect material. It is hopeful to help move the Moore’s law further since it is presently hindered by the current Cu- and Si-based technologies. The present paper serves as a compendium of research work on the application of CNTs for interconnection applications.

Formation of nanojoints between carbon nanotubes and copper nanoparticles

Exceptional properties and a one dimensional structure make carbon nanotubes (CNTs) a promising candidate for future applications in the electronic industry [1-3]. Because of their smaller dimensions and higher conductivity as compared to copper, multi-walled carbon nanotubes (MWCNT) may increase the bandwidth density of global interconnects [4]. They demonstrate charge carrier mean free paths between 500 nm and 10 μm as compared to 40 nm in metals. CNTs can carry exceptionally high current densities of up to 1010 A cm−2 even at elevated temperatures [5,6]. CNTs are expected to demonstrate resistance to electromigration higher than that of Cu-based interconnects [7].

Diffusion of elements during reflow ageing of Sn-Zn solder in liquid state on Ni/Cu substrate – theoretical and experimental study

Purpose This paper aims to study the diffusion of Zn, Ni and Sn in the liquid state during the reflow ageing of the Sn-Zn solder above its melting point on an Ni/Cu substrate in relation to the formation of intermetallic compounds (IMCs). Design/methodology/approach The Sn-Zn solder is reflowed on Ni/Cu substrates and is aged at 503 K. The formation of IMCs and their composition is characterized using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Diffusion coefficients and diffusion distances of Zn, Ni and Sn in the liquid state during reflow and ageing are theoretically calculated. Both experimental and theoretical behaviours for Ni and Zn diffusions are compared. Findings Calculations show a linear increment in the liquid-state diffusion coefficients of Ni, Zn and Sn in the solder matrix with a rise in temperature, but they remained constant during ageing. However, diffusion distances increased slowly with temperature but manifold with ageing time. The experimental results revealed segregation of Zn and Ni at the interface in the as-reflow aged specimens. The Zn was concentrated at the solder–substrate interface and it reacted with Ni diffusing from the substrate to form Ni-Sn-Zn IMCs. The rapid diffusion of Zn and Ni with the increase in ageing time increased their atomic concentrations in the IMCs against the reduction in Sn concentration owing to a comparatively slower diffusion. Originality/value The novelty of the paper is the detailed study of theoretical diffusion of Zn, Sn and Ni in the liquid state during reflow ageing of Sn-Zn above its melting points on a Ni/Cu substrate. This is compared with values obtained experimentally and related to the mechanisms of IMC formation.