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In case you missed it.

This month's abstracts come from the IPC/JEDEC International Conference on Lead-Free Electronic Components and Assemblies, which took place in December 2005.

Components

"A Feasibility Study of 01005 Chip Components in a Lead Free System"

Authors: Chrys Shea, Dr. Leszek Hozer, Hitoshi Kida and Mutsuharu Tsunoda; cshea@cooksonelectronics.com.

Abstract: A study was performed to understand assembly constraints of the newest miniaturized package chip components, 01005 (0402 metric). The study included all facets of surface-mount assembly: pad design and location, printability of small deposits, placement tolerances on components and reflow capability of small Pb-free deposits in an air environment. This study was a joint effort between a solder paste developer and pick-and-place machine supplier. It tested multiple solder deposit sizes in an effort to characterize the repeatability of the paste prints and the paste's reflow fusion capability in air. It also tested several component placement orientations and offsets, and multiple padstacks. The result shows strong feasibility of 01005 devices in modern assembly systems, and discusses the parameters that produced the best results in the system under consideration.

Reliability

"New England Lead Free Electronics Consortium--Phase III Efforts"

Authors: Greg Morose, Liz Harriman et al; greg@turi.org.

Abstract: The New England Lead-Free Electronics Consortium is a collaborative effort of New England companies spanning the electronics supply chain, sponsored by the Toxics Use Reduction Institute, the U.S. EPA and the University of Massachusetts Lowell. The consortium has published the results of two phases of manufacturing and testing of Pb-free PWBs with the goal of achieving zero-defect Pb-free soldering processes with comparable reliability to leaded solder processes. Phase I examined solder alloy combinations and reflow profiles, while Phase II focused more broadly on processing parameters, using a mix of component types and finishes in combination with five PWB finishes, two reflow atmospheres (air and [N.sub.2]) and three solder paste compositions based on Sn3.8Ag0.7Cu. The objective for Phase III testing was to focus on implementation issues by simulating an actual production board for parameters such as board layers, board size and component density. The Phase III PWB is a 20-layer, double-sided board populated with 1,750 components. Thirty-six PWBs were built and inspected to IPC-A-610D, and underwent thermal cycling, HALT and pull testing. This paper presents Phase III results, including the PWB interconnect stress test, test coupon failure mode analysis, visual inspection, thermal cycling, HALT and pull tests.

"Enhancements to Current Tin Whisker Risk Assessment Methods"

Author: David A. Pinsky; david_a_pinsky@raytheon.com.

Abstract: The author published an application-specific tin-whisker risk assessment algorithm in 2003, and issued an updated version in 2004. During the past year, experimental data have become available on the performance of conformal coating for containing tin whiskers. Additionally, data and a model have been published concerning the distribution of tin whisker lengths. This paper incorporates this new understanding into improved risk assessment methodologies. A model is presented that can be used to quantify the mitigation provided by imperfect conformal coating. Differences in the results predicted by the current and proposed improved methodologies, and their implications, are discussed.

RoHS Compliance

"Case Studies in RoHS Compliance: Eight Ways to Reach the Goal"

Author: Roger L. Franz; roger.franz@motorola.com.

Abstract: Achieving RoHS compliance is not straightforward. The requirement itself is elusive, requiring verification of every part in a product down to the homogeneous material level. Verification procedures are still new to OEMs as well as the entire electronics supply chain. Case studies in this paper are drawn from actual lessons learned at Motorola in preparing to launch RoHS-compliant consumer electronics devices. In the most rudimentary case, a component clearly fails due to having a restricted substance and all available evidence is in clear agreement. These components are simply replaced, in most cases by functional equivalents under new part numbers. An opposite case consists of parts which by some good fortune were always compliant and can continue to be used when the corresponding material disclosures are in place. Many of the mixed-case situations between these extremes were not even imagined before this work began. In retrospect, at least eight different scenarios can be encountered and must be resolved to achieve true agreement between engineering requirements, a supplier's perceived compliance and the same supplier's actual materials content data. Guidelines are also presented to deal with the added uncertainties of how to claim exemptions.

CIRCUITS ASSEMBLY provides abstracts of papers from recent industry conferences and company white papers. With the amount of information increasing, our goal is to provide an added opportunity for readers to keep abreast of technology and business trends.
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Title Annotation:Technical Abstracts
Publication:Circuits Assembly
Date:Mar 1, 2006
Words:765
Previous Article:Low power, [N.sub.2] reflow.
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