Microelectronics International

Shital Patil; Vijaya Puri

2012 Microelectronics International

doi: 10.1108/13565361211219103

Purpose – The purpose of this paper is to study properties of magnesium oxide and mixed magnesium oxide‐bismuth oxide thick films for application in tuned devices. Design/methodology/approach – The effect of magnesium oxide and mixed magnesium oxide‐bismuth oxide thick films overlay of different thickness on Ag thick film microstrip rectangular patch antenna was investigated in the X band (8‐12 GHz). Using Ag thick film microstrip rectangular patch antenna the thick and mixed thick films was characterized by microwave properties such as resonance frequency, amplitude, bandwidth, quality factor and input impedance. Using the resonance frequency the permittivity of magnesium oxide and mixed magnesium oxide‐bismuth oxide thick films was measured. Findings – Cubic structure of single magnesium oxide and monoclinic structure of bismuth oxide was present in mixed thick film. Also the morphology of single thick films was maintained in mixed thick film of magnesium oxide‐bismuth oxide. Due to overlay magnesium oxide and magnesium oxide‐bismuth oxide mixed thick films, change in resonance frequency shifts towards high frequency end was observed. Dielectric constant of magnesium oxide and mixed magnesium oxide‐bismuth oxide thick film calculated from resonance frequency decreased with increase in thickness. Originality/value – The microwave properties using Ag thick film microstrip patch antenna due to overlay of magnesium oxide and mixed magnesium oxide‐bismuth oxide thick films have been reported for the first time. Thickness of overlay dependent tuning of the antenna has been achieved.

Jiun‐Wei Horng

2012 Microelectronics International

doi: 10.1108/13565361211219112

Purpose – The purpose of this paper is to present two new follower‐based current‐mode multifunction filters. Each of the proposed circuits can realize highpass, bandpass and lowpass filters, simultaneously. Design/methodology/approach – The input terminals of the proposed current‐mode biquadratic filters are virtual grounded. The output terminals of the proposed circuits can be easily cascaded with the similar sections. Findings – Highpass, bandpass and lowpass filters can be obtained simultaneously from the proposed circuits using only one or two followers. Originality/value – The paper presents new ideas for follower applications.

Liyu Yang; Joseph Bernstein

2012 Microelectronics International

doi: 10.1108/13565361211219121

Purpose – The purpose of this paper is to describe key failure mechanisms observed during the development of the advanced packaging technology. Extensive accelerated stress tests are conducted to collect failure data and understand failure characteristics and failure trends. The results will be useful for design improvement and failure rate predictions. Design/methodology/approach – High density chip scale packages (CSP) are developed to meet the needs for high performance and small form‐factor products, but with reduced process procedures and product cost. Test‐to‐failure approaches are applied to evaluate the failure rate and reliability models instead of compliance qualification testing approaches. Findings – The study shows Cu‐trace cracking failure can be treated as random failures and analyzed using a constant failure rate approach. The acceleration factor for the Cu‐trace cracking failure mechanism exhibits a large power exponent comparing to the parameters used in reference models. In addition, the solder joint failure data collected through the study do not fit well with the well‐known solder fatigue life model. Moreover, the test results affirm the test‐to‐failure approach adopted in data collection is providing more accurate failure characteristics compared to the compliance qualification testing approach. Practical implications – The paper shows that the reliability performance of package technology can be improved by enhancing the package design, improving manufacturing processes and materials optimization. Originality/value – This is an original research paper and the test‐to‐failure approach in the reliability study helps provide realistic reliability predictions.

Mondher Chaoui; Richard Perdriau; Hamadi Ghariani; Mongi Lahiani

2012 Microelectronics International

doi: 10.1108/13565361211219130

Purpose – The purpose of this paper is to develop a model of the inductive link for implantable systems. The model is suitable for a cochlear implant in which a lateral misalignment and distance coil can be up to 16 mm. Design/methodology/approach – The description of the generation of implantable systems' high‐power, such as a cochlear implant, are powered by transcutaneous inductive power links formed by two coils: the first is a printed spiral coil used in the receiver device and the second is a solenoid coil used in the emitter device. Optimizing the power efficiency of the wireless link is imperative to minimize the size of the external energy source, heating dissipation in the tissue, and interference with other devices. The authors have outlined the theoretical foundation of optimal power transmission efficiency in an inductive link, and combined it with semi‐empirical models to predict parasitic components. The power amplifier itself is a class‐E amplifier optimized in both output voltage and efficiency, and bears an excellent tolerance to misalignments. Findings – Two Spice‐based electrical models of the coils are achieved. The technique employed during the work is based on polynomial interpolation of the mutual inductance in which coil misalignments are considered as variables. On the other hand, a voltage regulator is studied and simulated by Cadence Analog Artist in the AMS 0.35 μ m CMOS technology. Originality/value – This paper provides a novel and useful method for transmitting power for an implantable system via an inductive link. The procedure of the authors' design is achieved at 10 MHz and the power transmission efficiency is 35 percent, whatever the longitudinal misalignment (up to 16 mm) between both coils.

Yidong Zhang; Weiwei He

2012 Microelectronics International

doi: 10.1108/13565361211219149

Purpose – The purpose of this paper is to demonstrate the I‐V characteristics of ZnO film on Si substrates with Ag buffer layer by conductive atomic force (C‐AFM). Design/methodology/approach – An Ag buffer layer and Zn film was first deposited on silicon substrate by RF‐sputtering deposition method from high pure Ag and Zn target, respectively. Then, the deposited film was sintered in air at 500°C for 1 h. Findings – The structures and morphologies of the prepared films were characterized by X‐ray diffraction (XRD), energy dispersive spectrum (EDS), atomic force microscopy (AFM), and C‐AFM. The results show that the prepared ZnO films with Ag buffer layer have a good crystallinity and surface morphology. Interestingly, the I‐V curve of ZnO film exhibited typical characteristics of semi‐conductive oxide under the conductive Ag buffer layer. Originality/value – The paper demonstrates, by C‐AFM, that the ZnO/Ag‐buffer/Si exhibits excellent crystal structure, morphology and typical I‐V characteristics.

T.S. Dhahi; U. Hashim; M.E. Ali; Nazwa Taib

2012 Microelectronics International

doi: 10.1108/13565361211219167

Purpose – Nanogap electrodes have important applications in power saving devices, electrochemical sensors and dielectric detections of biomolecules. The purpose of this paper is to report on the fabrication and characterization of polysilicon nanogap patterning using novelties technique. Design/methodology/approach – Polysilicon material is used to fabricate the nanogap structure and gold is used for the electrode and two chrome masks are used to complete this work; the first mask for the nanogap pattern and a second mask for the electrode. The method is based on the control of the coefficients (temperature and time) with an improved pattern size resolution thermal oxidation. Findings – Physical characterization by scanning electron microscopy (SEM) demonstrates such nanogap electrodes could be produced with high reproducibility and precision. Electrical characterization shows that nanogap enhanced the sensitivity of the device by increase the capacitance and the conductivity as well. They have also good efficiency of power consumption with high insulation properties. Originality/value – With this technique, there are no principal limitations to fabricating nanostructures with different layouts down to several different nanometer dimensions. The paper documents the fabrication of nanogaps electrodes on a polysilicon, using low‐cost techniques such as vacuum deposition and conventional lithography. Polysilicon is a low‐cost materials and has desirable properties for semiconductor applications. A method of preparing a nanogap electrode according to the present innovation has an advantage of providing active surface that can easily be modified for immobilizations of biomolecules.

Dhafer Abdul Ameer Shnawah; Mohd Faizul Bin Mohd Sabri; Irfan Anjum Badruddin; Suhana Said

2012 Microelectronics International

doi: 10.1108/13565361211219202

Purpose – The purpose of this paper is to discuss the reliability of board level Sn‐Ag‐Cu (SAC) solder joints in terms of both thermal cycling and drop impact loading conditions, and further modification of the characteristics of low Ag‐content SAC solder joints using minor alloying elements to withstand both thermal cycle and drop impact loads. Design/methodology/approach – The thermal cycling and drop impact reliability of different Ag‐content SAC bulk solder will be discussed from the viewpoints of mechanical and micro‐structural properties. Findings – The best SAC composition for drop performance is not necessarily the best composition for optimum thermal cycling reliability. The content level of silver in SAC solder alloys can be an advantage or a disadvantage depending on the application, package and reliability requirements. The low Ag‐content SAC alloys with different minor alloying elements such as Mn, Ce, Bi, Ni and Ti display good performance in terms of both thermal cycling and drop impact loading conditions. Originality/value – The paper details the mechanical and micro‐structural properties requirements to design a robust bulk SAC solder joint. These properties provide design and manufacturing engineers with the necessary information when deciding on a solder alloy for their specific application.