Book Review

Lead-Free Implementation and Production–A Manufacturing Guide PUBLIC ACCESS

[+] Author and Article Information
Jennie S. Hwang

Anthony J. Rafanelli1


Raytheon Integrated Defense Systems, Portsmouth, RI 02871-1087.

J. Electron. Packag 129(1), 109-110 (Mar 01, 2007) (2 pages) doi:10.1115/1.2429719 History:

Lead-Free Implementation and Production–A Manufacturing Guide

In this book, Dr. Jennie Hwang provides a companion reference to her previous work Environmental Friendly Electronics: Lead Free Technology. This book focuses on implementation and production aspects. It is easily read and provides many case studies. A prerequisite for readers is that they have a working knowledge of lead-free technology. Otherwise, review of the first book is advisable.

Chapter 1 is an introduction. It provides the purpose for the book and also discusses driving forces, world-wide legislation, research/technology development, and lead-free technology/manufacturing. Dr. Hwang has been an avid supporter of lead-free transition and should be commended for her passion and dedication to this cause. She presents a strong case of listing the many activities in lead-free legislation and includes statistics on lead use and thresholds. What is missing in this chapter is the statistic showing the relatively small amount of lead used in electronics (i.e., less than 2%), and subsequently how this transaction has greatly burdened the industry especially with the, as of yet, unfamiliarity with lead-free processes and product performance. This chapter could have been greatly improved by making this point. To the chapter’s credit, excellent summaries of the fore-mentioned topics are provided. Some very good insight is provided on behavior of lead-free versus lead as well as behavior of mixed technologies. Of particular note are Secs. 1.6.1–1.6.3 which discuss alloy strengthening and design. Approaches are neatly summarized to benefit the design engineer.

Chapter 2 discusses manufacturing implementation approaches. Five main steps of factory transition are presented. Implementation is presented in three approaches: drop-in, modifications, and tight process. The first two are distinguished by process temperature. The reviewer questions whether drop-in is at all feasible given contamination issues of equipment previously exposed to eutectic tin–lead. The third approach, tight process, involves careful identification and control of process control parameters. Yet, when discussing these approaches, should not equipment be considered as well? The detailed sections, discussing these approaches, appeared to be out of order (not a serious issue). Like Chap. 1, this chapter finishes strong with very good discussions on top performance parameters, process versus material options, and comparisons of the approaches.

Chapter 3 focuses on selection of lead-free alloys for solder interconnections. Information is directed to intrinsic wetting ability, melt temperature, and summaries of key mechanical properties. Data include wetting curves and wetting force for select alloys.

Chapter 4 addresses solder paste. Topics include multidisciplinary technology, basic technologies, formulations, fluxes/fluxing, solder powder characteristics, powder selection, performance parameters, dispensing, printing and new/future demands. The discussion on multidisciplinary technology is noteworthy since it shows how paste technology derives several key products for overall electronic assembly; thick films, conductive adhesives, EMI shielding materials, brazing pastes, and other metallic or oxide particle products. The section on new and future demands is very beneficial as it provides insight into paste considerations in package technology advances with respect to fine pitch and increased solder bumping.

Chapter 5 discusses the selection of component coatings and printed wiring board (PWB) circuit finishes. The first half of the chapter addresses coatings and their roles as well as application considerations. The section on tin whiskers is nicely done. Dr. Hwang does a very good job in summarizing the phenomenon, explaining possible causes, and presenting a suitable amount of detail for each of the possible causes. The graphics are very good as well. A brief section on tin pest is provided. The second half of the chapter deals with lead-free PWB surface finishes.

Chapter 6 focuses on applying mass reflow soldering. As a credit to the format of this book, this chapter provides key information for the process engineer on reflow soldering considerations for lead-free assembly. The Introduction discusses four heating processes and then the chapter presents examples and illustrations of reflow production, i.e., one-side reflow, two side reflow, and paste-in-hole reflow. For each of these, primary parameters/conditions and general results are given. Strong tutorial-like sections are provided on reflow principles, reflow profile effects, process parameters, and equipment/peripherals. The chapter ends with presentations on nitrogen atmosphere reflow, temperature measurement, and a brief discussion on vapor phase reflow.

Chapter 7 covers wave soldering and selection soldering in two parts. In the first part, a list of several factors affecting wave solder efficiency and effectiveness are presented. Similar to the previous chapters, several wave soldering production and test cases are given based upon alloy. For each alloy, primary parameters/conditions and general findings are disclosed. As is the overall trend of the book, the format facilitates the production engineer in using the information in this chapter. Considerations such as alloy, process, equipment, cost, and use of nitrogen are provided. Part 2 of the chapter discusses selective soldering and such heat sources as hot bar, hot gas, focused IR, soft beam and laser.

Chapter 8 is presented in two parts, the first addressing compatibility (process and material, lead-free/lead-free, lead/lead-free) and the second addressing cost considerations. The latter topic also includes a case study. The Material and process compatibility section is very thorough providing several real-life scenarios. Likewise are the sections on lead/lead-free for lead contamination and mixed technology considerations. There is also a very informative section on compositional tolerance providing guidelines on constituent limits for a variety of alloys with respect to optimum performance of reflow and wave soldering applications. The second part covers costs associated with metal elements, alloy composition, solder, operations, PWBs/components, equipment, and systems.

Chapter 9 discusses manufacturing and common production defect considerations. The beginning of the chapter briefly discusses industry standards, in particular ANSI-STD-001. The electronic product classes (Class 1 General, Class 2 Dedicated Service, and Class 3 High Performance) are also mentioned. Next a comprehensive list of potential production defects and concerns is presented with detailed sections on each.

Chapter 10 is directed toward accelerated life testing, in particular temperature cycling tests. The goal of such testing is to predict reliability of electronic assemblies. Dr. Hwang begins the chapter by discussing “evolutionary developments” over the past 25 years. These seven developments truly illustrate the significant advances in electronic system technology as well as emphasize the challenges. Thus the point is made in deciding upon a suitable reliability test approach. Section 10.1.1 does a very nice job of explaining the difference in performance concerns between solder joints and bulk solder. Also presented is a hierarchy of solder joints. Section 10.2.2 talks about challenging areas in life prediction modeling and while the list is pretty thorough, the effect of test temperature on materials is not included, an item which also bears consideration in deriving a model. The latter half of the chapter deals with all aspects of fatigue testing.

In general, the book is well organized. The typeface size facilitates easy reading. The book serves as an excellent reference for any engineer working in the electronics industry. This reviewer highly recommends this book.

Copyright © 2007 by American Society of Mechanical Engineers
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