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Electronics Packaging Manufacturing, IEEE Transactions on

Issue 1 • Date Jan. 2005

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  • [Front cover]

    Publication Year: 2005 , Page(s): c1
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  • IEEE Transactions on Electronics Packaging Manufacturing publication information

    Publication Year: 2005 , Page(s): c2
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  • Table of contents

    Publication Year: 2005 , Page(s): 1
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  • Foreword Special Issue on Tin Whiskers

    Publication Year: 2005 , Page(s): 2
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  • Tin whisker test standardization

    Publication Year: 2005 , Page(s): 3 - 9
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3104 KB) |  | HTML iconHTML  

    A National Electronics Manufacturing Initiative (NEMI) Committee, Whisker Test Method Standardization, was formed in 2001 to evaluate and identify environmental test conditions that are useful in predicting the propensity for tin whisker growth. The objective of the committee is to develop standardized whisker testing methods to provide to the electronics industry for characterizing and qualifying tin-based finishes. The team completed two evaluation phases and has identified three test methods effective in inducing whisker growth, two isothermal storage methods and one temperature cycle method. A Phase 3 evaluation was initiated in mid 2003 to confirm the consistency of these testing methods, determine effectiveness for different Sn-based finishes, and possibly define test end points by determining the longest duration for whisker growth saturation for different Sn-based finishes. Results thus far confirm that temperature cycling and 60C/93 RH isothermal storage are effective in producing whiskers. An additional evaluation, Phase 4, has been initiated to look at the effect of electrical bias on accelerating whisker growth. A Phase 5 Evaluation is in the design stage. The objectives of the Phase 5 Evaluation are still being discussed. A brief review of the Phase 1 and 2 Evaluations results which led to NEMI's test method recommendations will be provided. In addition, the latest results for the Phase 3 Evaluation and status of the Phase 4 and 5 Evaluations will also be shared. View full abstract»

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  • Whisker test methods of JEITA whisker growth mechanism for test methods

    Publication Year: 2005 , Page(s): 10 - 16
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1040 KB) |  | HTML iconHTML  

    As the industry moves toward lead-free electronics, a replacement for the traditional tin-lead plating is required. Pure tin is the coating of choice for many suppliers, but there is a well-known problem with the growth of tin whiskers. A whisker is comprised of a tin crystal which, after an incubation period, grows with time. Whiskers may grow long enough to cause shorts in electronic circuits. A test method is required for evaluating the reliability risk inherent in tin whiskers. The Japanese government requested the Japan Electronics and Information Technology Industries Association (JEITA) to establish test methods for solderability, reliability, whisker, and migration for lead-free electronics. The goal of this subcommittee was to propose the test methods for tin whiskers by March 2004. The committee carried out a literature survey, and developed hypotheses for whisker growth, which was then applied to test methods. Two types of studies were undertaken. One is a fundamental study to verify the hypothesis. The other looked at accelerated tests to develop recommended test conditions. As a result, we found that the diffusion of copper, oxidation, and thermal cycling all influence tin whisker growth. This paper describes the results of the fundamental studies and reports on the JEITA whisker growth mechanism. View full abstract»

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  • An integrated theory of whisker formation: the physical metallurgy of whisker formation and the role of internal stresses

    Publication Year: 2005 , Page(s): 17 - 30
    Cited by:  Papers (58)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3664 KB) |  | HTML iconHTML  

    Over 50 years of whisker research (cadmium, zinc, and tin) has not resulted in consensus about whisker formation fundamentals for metal films. New analytical tools have recently provided new insights into microstructural changes that occur during whisker formation. Integration of these newer observations with historical data led the authors to propose an Integrated Theory of Whisker Formation. The Integrated Theory incorporates physical attributes such as microstructure and internal stress states. Particular emphasis is placed on recrystallization, grain boundary diffusion, film-substrate interdiffusion (i.e., the Kirkendall effect), and stress gradients. The Integrated Theory does not require dislocation mechanisms for material transport to the whisker location. Material is transported to a whisker grain by the surrounding grain boundary network under the driving impetus of positive stress gradients. Transported atoms then move from the grain boundary network into the whisker grain. This movement into the whisker grain pushes the free surface of the whisker grain upward and, thereby, grows the whisker structure. View full abstract»

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  • Driving force for the formation of Sn whiskers: compressive stress-pathways for its generation and remedies for its elimination and minimization

    Publication Year: 2005 , Page(s): 31 - 35
    Cited by:  Papers (29)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1896 KB) |  | HTML iconHTML  

    Compressive stress is widely accepted as the driving force for tin whisker formation. There are several pathways for compressive stress buildup in Sn coatings, which include the following: residual stress generated during plating; stress formation due to interfacial reactions between tin and copper substrate; mechanical stress; and thermal mechanical stress due to coefficient of thermal expansion (CTE) mismatch between the tin layer and substrate during thermal cycling. In order to prevent or reduce whisker growth in tin deposits, compressive stress has to be eliminated or minimized. This paper discusses the pathways for compressive stress formation and various remedies for its elimination and minimization. Particularly, a novel approach for dealing with thermal mechanical stress due to CTE mismatch is discussed. View full abstract»

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  • Sn whiskers: material, design, processing, and post-plate reflow effects and development of an overall phenomenological theory

    Publication Year: 2005 , Page(s): 36 - 62
    Cited by:  Papers (31)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (8912 KB) |  | HTML iconHTML  

    Replacement of Pb/Sn terminations on electronic devices with pure Sn has proven to be much more difficult than expected. The main problem is Sn whisker formation. Sn whiskers are typically single-crystal, mechanically strong, metallic filaments that can nucleate and grow over time in such a way as to lead to device failure in the field. In this study, we present the results of Sn whisker formation and growth studies for plated matte-Sn on Cu Pb frames. We include data on the effects of Sn-thickness, post-plate annealing, and simulated board attach reflow. Also included are data on two different bath base chemistries, methane sulfonic acid (MSA) and mixed acid, three different plating bath suppliers, and three different lead-frame plating suppliers. The effects of trim and form as well as lead-frame alloy type were also investigated. Whisker testing was completed by storing devices for at least 1 year at room ambient, 60°C/93%RH, and 60°C/<10%RH. Additional tests were done by subjecting devices to temperature cycling between -55°C and +85°C. Finally, condensing environmental testing and bias/temperature/humidity tests were completed. The results indicate that the propensity for whisker formation and growth decreases with increasing Sn thickness, and with a post-plate heat treatment. The data imply that the improvement is one of increasing the incubation time, not one of complete elimination of the potential for whiskers. Analysis of the data also indicates the interpretation of Sn whisker formation and growth data taken from a small set of experimental conditions and or small number of devices or leads may lead to incorrect conclusions when compared to a larger data set. When taken in totality, no exact systematic dependency on the propensity for whisker formation was found between dependent variables of trim and formed and nontrim and formed lead frames or for stamped versus etched lead frames. With the exception of 60°C/93%RH exposure, no systematic interaction with process conditions and/or process/stress conditions were found. For stressing at 60°C/93%RH, there was a clear indication that the trim and form devices were significantly more susceptible to whisker formation than nontrim and formed devices. The pr- opensity for whisker growth was found to be similar at room ambient and 60°C/<10%RH. The propensity for whisker formation is lowest for the room temperature and 60°C/<10%RH storage, followed by temperature cycling, followed by noncondensing 60°C/93%RH storage. A condensing 60°C/93%RH environment was found to result in an accelerated corrosion assisted whisker growth mechanism producing locally dense clusters of whiskers or "flowers". No effects of electrical bias on the propensity for whisker growth were observed, and it is concluded that electrical bias itself does not appear to be a promary driving mechanism for Sn whisker growth. Finally, the application of a post-plate solder reflow is found to significantly impact the propensity for whisker growth. In particular, the incubation time for whisker growth in 60°C/93%RH was found to be of order 10-15 weeks for all devices subjected to a simulated board-attach reflow process at peak temperatures greater than 232°C. Whereas for devices not subjected to a simulated reflow, the incubation time was 26 weeks for 7-μm-thick films and 61 weeks for 15-μm-thick films. We have observed whisker growth on all samples independent of lead-frame alloy type, plating chemistry, and plating supplier. Finally, we have found that a Ni-underplate, if implemented correctly, eliminated whisker growth for at least 52 weeks at 60°C/93%RH independent of simulated reflow process. We present a model that reveals the improvements afforded by the post-plate anneal is one of extending the incubation time not one of complete elimination of whiskers. Finally, we propose a model tha View full abstract»

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  • Role of intrinsic stresses in the phenomena of tin whiskers in electrical connectors

    Publication Year: 2005 , Page(s): 63 - 74
    Cited by:  Papers (23)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5312 KB) |  | HTML iconHTML  

    The connector industry is at a crossroads with respect to selecting lead-free coatings in response to legislation and customer demands. Component manufacturers have long used tin-lead coatings because of lead's ability to inhibit tin whisker formation. Several lead-free alternate finishes such as pure tin, tin-bismuth, tin-copper, tin-zinc, Pd, and Pd-Ni-Au have been proposed. One simple, economical, and easy drop-in replacement is pure matte tin. Unfortunately, pure tin films have a fairly high risk of whisker formation. Factors, such as substrate material, plating process variables, and assembly operations also play a role in whisker generation. The stresses imposed at each process step pose a serious threat to whiskering. We have critically evaluated three matte tin chemistries by changing bath composition and deposition parameters. We also characterized stresses in these matte tin coatings by using flexure beam and X-ray diffraction techniques. This paper identifies stress types encountered in various connector applications, provides an insight to the users about practical situations, and suggests whisker mitigation strategies. The impact of environmental (e.g., temperature and humidity) stresses on tin coatings is also discussed. View full abstract»

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  • Electrostatic fields and current-flow impact on whisker growth

    Publication Year: 2005 , Page(s): 75 - 84
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3112 KB) |  | HTML iconHTML  

    Tin whisker growth is problematic due to the potential for short circuits in electronic devices. These devices are electrically active, generating electric fields, and transporting current. Controversy continues regarding the propensity for tin whiskers to grow more readily in the presence of an electrical bias, and other researchers have proposed that an electrical field can influence tin-whisker growth directions. The latter would exacerbate the problem of tin whiskers in electronic devices by potentially reducing the effective growth length required to induce electrical shorts. In this paper, we have developed a new test vehicle to examine the roles of electric field and current flow on the tendency to form tin whiskers. Parts have been exposed to various environmental conditions, similar to those proposed by the National Electronics Manufacturing Initiative (NEMI). In summary, the electrical fields used here, bias and current flow, do not significantly affect whisker growth. We will also present some analytical discussion regarding the potential of electromagnetic fields to influence whisker growth directions or deflections. View full abstract»

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  • Investigation of Sn-Cu intermetallic compounds by AFM: new aspects of the role of intermetallic compounds in whisker formation

    Publication Year: 2005 , Page(s): 85 - 93
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2456 KB) |  | HTML iconHTML  

    It has been observed that different tin whisker growth properties can result from the same tin deposit on two copper leadframe materials, C19400 and C70250. It was also found that modification of the surface condition of identical substrates, through pretreatment prior to Sn-plating, affects whisker growth behavior. Here, we report an atomic force microscopy (AFM) investigation of intermetallic compounds (IMC) formed on samples with significantly different whisker growth tendencies. AFM data analysis in conjunction with the IMC growth rate, determined using the weight gain method, provides quantitative data of the IMC characteristics. It was found that the whisker propensity is not directly related to the uneven growth front of IMC as detected by AFM. Whisker growth tendency, with respect to whisker density and length, decreases when the unevenness of the IMC layer exceeds a certain level. The results of this work show evidence that the whisker propensity is associated with the copper substrate texture as well as the substrate surface topography. View full abstract»

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  • Annotated tin whisker bibliography and anthology

    Publication Year: 2005 , Page(s): 94 - 122
    Cited by:  Papers (80)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB) |  | HTML iconHTML  

    Whisker publications from 1947 through 2004 are summarized and referenced in this document. The bibliography listings are chronological (by publication year) while the anthology section arranges references by topic. Almost all of the referenced documents deal with tin whiskers, but there are few that deal with zinc whiskers. View full abstract»

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  • 7th Electronics Packaging Technology Conference (EPTC 2005)

    Publication Year: 2005 , Page(s): 123
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  • Explore IEL IEEE's most comprehensive resource

    Publication Year: 2005 , Page(s): 124
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  • Join IEEE

    Publication Year: 2005 , Page(s): 125
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  • IEEE order form for reprints

    Publication Year: 2005 , Page(s): 126
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  • IEEE Transactions on Advanced Packaging - Table of contents

    Publication Year: 2005 , Page(s): 127 - 128
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  • IEEE Transactions on Components and Packaging Technology - Table of contents

    Publication Year: 2005 , Page(s): 129 - 130
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  • IEEE copyright form

    Publication Year: 2005 , Page(s): 131 - 132
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  • IEEE Components, Packaging, and Manufacturing Technology Society Information for authors

    Publication Year: 2005 , Page(s): c3
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  • IEEE Components, Packaging, and Manufacturing Technology Society Information

    Publication Year: 2005 , Page(s): c4
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Aims & Scope

IEEE Transactions on Electronics Packaging Manufacturing addresses design for manufacturability, cost and process modeling, process control and automation, factory analysis and improvement, information systems, statistical methods, environmentally friendly processing, and computer-integrated manufacturing for the production of electronic assemblies and products.

 

This Transaction ceased production in 2010. The current publication is titled IEEE Transactions on Components, Packaging, and Manufacturing Technology.

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Meet Our Editors

Editor-in-Chief
R. Wayne Johnson
Auburn University