Embedded Design

“Interfacing PIC Microcontrollers: Embedded Design by Interactive Simulation”

Author: Martin P. Bates; mbates@hastings.ac.uk.
Abstract: The second edition of this book is an introductory text for those starting out in this field and a source reference for more experienced engineers, containing a balance of theory and practice with numerous working examples throughout. It provides comprehensive coverage of basic microcontroller system interfacing using the latest interactive software, Proteus VSM, which allows real-time simulation of microcontroller based designs and supports the development of new applications from initial concept to final testing and deployment. It includes a comprehensive introduction to interfacing 8-bit PIC microcontrollers; designs updated for current software versions MPLAB v8 & Proteus VSM v8; and additional applications in wireless communications, intelligent sensors and more. (Elsevier, October 2013)

Optical Waveguides

“Influence of Photolithography on the Cross-Sectional Shape of Polysiloxane as an Optical Waveguide Material on Printed Circuit Boards”

Authors: Dr. Kam-chuen Yung, et al.; mfkcyung@polyu.edu.hk.
Abstract: Optical waveguide cross-sectional shapes that deviate from rectangles or squares may cause significant loss of signal. In this study, a photolithography approach was adopted to fabricate waveguides on PCBs, using photo imageable polysiloxane as a waveguide material. The effects of I-line ultraviolet (UV) lamp exposure, 355nm Nd:YAG laser direct imaging, and 248nm excimer laser direct imaging on the cross-sectional shape of waveguides were investigated. For I-line UV lamp exposure, increasing the exposure time could cause changes in the tilt angle of the waveguides from negative (inverted trapezoid) to positive (trapezoid). To obtain rectangular waveguides, the optimum I-line UV lamp exposure time was found to be around 150 sec. From the results for 355nm Nd:YAG laser direct imaging, the width and tilt angle of the waveguides varied with the energy density of the laser beam irradiating the core materials, being controlled by the repetition rate and focus. Lowering the laser energy density could produce waveguides with small widths and tilt angles. Excimer laser direct imaging at 248nm was found to be unsuitable for waveguide patterning since the core materials could not be cured at this wavelength. (Journal of Electronic Materials, December 2013)

Printing

“Plasma Stencil Treatments: A Statistical Evaluation”

Authors: Matt Kelly, William Green, Marie Cole and Ruediger Kellmann; mattk@ca.ibm.com.
Abstract: Integration of large and small body components onto a single PCB with increasing population densities and tighter placement spacings, drives the need for consistent solder paste print deposits to ensure maximum first-pass assembly yields and highest product quality/reliability levels. Balancing solder paste printing of large and small print deposits has been reported to be enhanced using various surface treatments on laser-cut stencils. This study focused on examining the effects of a plasma coating compared to conventional stainless steel laser-cut technology. Printing performance on a variety of components was evaluated including five different BGAs, flip-chip QFNs, SMT electrolytic capacitors, 0805, 0402, and 0201 passives. Lead-free no-clean and water-soluble paste chemistries were included, along with two different aperture ratio (A/R) design points for all components studied. For assessing the durability of the plasma coating, production volume cleaning simulations were conducted with 24 different solvents.

Statistical analysis was conducted to evaluate any observed differences between conventional stencil technology and a plasma-treated alternative. A DoE was conducted  to evaluate main effects and interactions. (SMTA Journal, vol. 26, no. 4, Winter 2013)

Solder Materials

“Thermal Conductivity Variation with Temperature for Lead-Free Ternary Eutectic Solders”

Authors: Namık Aksöz, et al.
Abstract: Variations of the thermal conductivity with temperature for the lead-free ternary eutectic solders Bi-42.73 wt.%Sn-1.03 wt.%Ag (Bi-Sn-Ag), Sn-3.5 wt.%Ag-0.9 wt.%Cu (Sn-Ag-Cu), Sn-6 wt.%Sb-5 wt.%Ag (Sn-Sb-Ag), Sn-42.8 wt.%Bi-0.04 wt.%Cu (Sn-Bi-Cu), and In-48.4 wt.%Sn-2.31 wt.%Ag (In-Sn-Ag) were measured using a linear heat flow apparatus. It was observed that the thermal conductivities of solid phases for the BiSnAg, SnAgCu, SnSbAg, SnBiCu, and InSnAg solders decrease linearly with increasing temperature. Thermal conductivities of the BiSnAg, SnAgCu, SnSbAg, SnBiCu, and InSnAg solders at their melting temperature were obtained as 17.89 ± 1.6 W/K-m, 49.89 ±4.5 W/K-m, 41.96 ±3.8 W/K-m, 20.03 ±1.8 W/K-m, and 70.21 ±6.3 W/K-m, respectively. Thermal temperature coefficients for BiSnAg, SnAgCu, SnSbAg, SnBiCu and InSnAg solders were determined to be −2.894 × 10−3 K−1, −0.907 × 10−3 K−1, −1.246 × 10−3 K−1, −2.638 × 10−3 K−1, and −1.250 × 10−3 K−1, respectively, from plots of thermal conductivity versus temperature. (Journal of Electronic Materials, December 2013)

This column provides abstracts from recent industry conferences and company white papers. Our goal is to provide an added opportunity for readers to keep abreast of technology and business trends.

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