Whisker Formation on Electronic Materials

Dunn, B. D.

doi:10.1108/eb043543

Cited by 41 publications

(10 citation statements)

References 5 publications

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“…Sn-whiskers grow through continuous addition of material to their base [4]. Mechanical [5], electrical [6] and transmission electron microscopy investigations [7][8][9][10] proved Sn-whiskers to be nearly perfect single-crystalline filamentary structures forming on the surfaces of metals with a low melting point [11]. The diameters of Sn-whiskers are about 1-10 ptm, whereas the length can reach values up to 10 mm [12].…”

Section: Introductionmentioning

confidence: 99%

The Microstructure and State of Stress of Sn Thin Films after Post-Plating Annealing: An Explanation for the Suppression of Whisker Formation?

Sobiech¹,

Welzel²,

Schuster

et al. 2007

2007 Proceedings 57th Electronic Components and Technology Conference

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The post-plating annealing ('post-bake' treatment, annealing at 150°C for 1 h) of pure matte Sn thin films on Cubased substrates is known to be an effective whisker mitigation treatment. The microstructure and the stress state of Sn thin films on Cu-substrates produced with and without a 'post-bake' treatment have been investigated using scanning electron and focused ion beam microscopy (SEM & FIB), Xray photoelectron spectroscopy (XPS) and ageing time and depth-dependent X-ray diffraction (XRD) stress analyses. A comparison of the measured stress-depth gradients in the near-surface regions of the Sn thin films produced with and without 'post-bake' treatment indicates differences that might provide a plausible explanation for the observed long-term resistance against whisker growth of Sn thin films subjected to a 'post-bake' treatment. In specimens subjected to a 'postbake' treatment, an almost depth-independent tensile stress state prevails in the surface region even after prolonged ageing.

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Section: Introductionmentioning

confidence: 99%

The Microstructure and State of Stress of Sn Thin Films after Post-Plating Annealing: An Explanation for the Suppression of Whisker Formation?

Sobiech¹,

Welzel²,

Schuster

et al. 2007

2007 Proceedings 57th Electronic Components and Technology Conference

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“…While a significant amount of research was conducted in this area [2,7,15,23], the mitigation strategy of using lead-tin solders was identified [3,8,9] and reduced the problem of whiskering. With the addition of lead to tin, the interest in whisker growth diminished until legislation in various countries banned lead from solders.…”

Section: Chapter 2 Backgroundmentioning

confidence: 99%

Modeling tin whisker growth.

Weinberger¹

2013

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Tin, lead, and lead-tin solders are the most commonly used solders due to their low melting temperatures. However, due to the toxicity problems, lead must now be removed from solder materials. This has lead to the re-emergence of the issue of tin whisker growth. Tin whiskers are a microelectronic packaging issue because they can lead to shorts if they grow to sufficient length. However, the cause of tin whisker growth is still not well understood and there is lack of robust methods to determine when and if whiskering will be a problem. This report summarizes some of the leading theories on whisker growth and attempts to provide some ideas towards establishing the role microstructure plays in whisker growth.3

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“…In essence, it was a thermal "shock" rather than the The maximum length of whisker is another parameter often used traditional thermal "cycle" test. Prior to the thermal cycle test, the to describe whiskering propensity and risk [11]. In this study, the samples were conditioned with lead-free reflow treatment.…”

Section: Introductionmentioning

confidence: 99%

Properties of a Newly Developed Immersion Tin Coating

Yau¹,

Cai²,

Farrell³

et al. 2008

2008 3rd International Microsystems, Packaging, Assembly &Amp; Circuits Technology Conference

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tin coating [6], can this minimum thickness be reduced if the tin coating property is altered by the plating chemistries? Gradually diminishing solderability and potential risk of whisker growth are two major concerns in using immersion tin as a final EXPERIMENTAL finish for printed wiring boards. Both phenomena are attributable to the spontaneous formation of intermetallic compounds (IMC) of Sample Plating Cu6Sn5 and Cu3Sn between the tin coating and copper substrate. The formation of IMC consumes the free tin in the coating that is A newly developed immersion tin process developed by Enthone essential for good solderability. It also builds up compressive stress was used in this study. Test coupons were prepared through the within the tin coating that induces whisker growth. The formation of common process procedures used in applying final finishes at PWB IMC is known to be affected by the microstructure of the tin coating, fabrication, i.e., cleaning, rinsing, micro etching, rinsing, pre-dip, as evidenced by the difference in whisker propensity observed plating, rinsing and drying. To standardize the hydrodynamic between bright and matte tin coatings. Various methods have been conditions in the plating solution, sample coupons were plated used in the formulation of immersion tin chemistries to alter the manually in beakers with a reciprocal motion at about 1 cycle/second. microstructure of the tin deposit and to retard the intermetallic The dwell time in the plating solution was nine minutes unless formation process, yet there is no direct experimental data to link specified otherwise. Various test coupons were plated for their solderability and whisker propensity to the physical properties of the intended use. tin deposit. The objective of this study was to investigate such a link through the evaluation of a newly developed immersion tin chemistry. Tin Thickness MeasurementThe propensity to form whiskers was evaluated by aging in an ambient environment for 3000 hours and accelerated thermal cyclingThe tin coating thickness was measured by X-ray fluorescence tests. Solderability was evaluated by wetting balance tests after (XRF) and Sequential Electrochemical Reduction Analysis (SERA). simulated reflow thermal excursions. The distribution of IMCs was The XRF measurement was made using the SEA 5210 Element investigated by sequential electrochemical reduction analysis and Monitor MX from Seiko Instruments with the L-series X-ray lines cross examined by focused ion beam.for improved accuracy. The SERA test was conducted with the SURFACE-SCAN) QC-1OOTM from ECI Technology, using a 5%

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Whisker Formation on Electronic Materials

Cited by 41 publications

References 5 publications

The Microstructure and State of Stress of Sn Thin Films after Post-Plating Annealing: An Explanation for the Suppression of Whisker Formation?

The Microstructure and State of Stress of Sn Thin Films after Post-Plating Annealing: An Explanation for the Suppression of Whisker Formation?

Modeling tin whisker growth.

Properties of a Newly Developed Immersion Tin Coating

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