Thermal Preconditioning and Restoration of Bismuth-Containing, Lead-Free Solder Alloys

Delhaise, André M.; Snugovsky, Polina; Kennedy, Jeff; Hillman, D.; Matijevic, Ivan; Meschter, Stephan J.; Adams, D. L.; Kammer, Milea J.; Romansky, Marianne; Juarez, Joseph; Straznicky, Ivan; Snugovsky, L.; Wilcoxon, Ross; Perović, D. D.

doi:10.1007/s11664-019-07666-w

Cited by 13 publications

(6 citation statements)

References 16 publications

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“…Examples of aligned Bi plates are given in Figs. 3, 4, 6b and 7, and similar examples can be found in the literature [7,31,48,49]. The shape of (Bi) precipitates suggests the existence of preferred interfaces between (Bi) and βSn.…”

Section: Orientation Relationships Between βSn Matrix and (Bi) Platessupporting

confidence: 73%

Precipitation and coarsening of bismuth plates in Sn–Ag–Cu–Bi and Sn–Cu–Ni–Bi solder joints

Belyakov

Xian

Zeng

et al. 2018

J Mater Sci: Mater Electron

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In recent years there has been increased interest in Bi-containing solders to improve the reliability of electronics and drive down processing temperatures. When the Bi content is more than ~ 2 wt% in SnAg -Cu-Bi and Sn-Cu-Ni-Bi solders, (Bi) phase forms by a non-equilibrium eutectic reaction and also precipitates in the solid state. Here, we study the development of bismuth plates during room temperature storage in a range of Bi-containing solders. It is shown that Bi plates precipitate with one of two (Bi)-βSn orientation relationships (ORs). During coarsening the OR with the better lattice match grows at the expense of the other, leading to a single OR. The plate coarsening kinetics scale with the cube root of holding time and are relatively rapid, with plates exceeding 1 µm in length within 1 day at room temperature. Prolonged room temperature storage of more than 1 year resulted in Bi accumulation in 5-20 µm (Bi) particles at βSn grain boundaries.

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Section: Orientation Relationships Between βSn Matrix and (Bi) Platessupporting

confidence: 73%

Precipitation and coarsening of bismuth plates in Sn–Ag–Cu–Bi and Sn–Cu–Ni–Bi solder joints

Belyakov

Xian

Zeng

et al. 2018

J Mater Sci: Mater Electron

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“…There is virtually no solubility of Sn in Bi, and no intermediate phases or intermetallic compounds (IMC) are found in the Sn-Bi system. Data from multiple studies show that Bi improves the mechanical properties of Sn and SAC solder [27,34,[37][38][39][40][41][42][43][44][73][74][75][76][77][78]. Vianco [30,31] and Witkin [34,[66][67][68] did extensive mechanical testing and microstructural analysis and discussed the dual strengthening mechanisms of Bi in solid solution and Bi precipitated within Sn dendrites and at Sn boundaries.…”

Section: Bismuth (Bi) Additions To Tin (Sn)mentioning

confidence: 99%

“…• The drop shock test did not provide results allowing for differentiation between the solder alloys REMAP Pb-free Testing Program [82] In 2014 -2019 the Refined Manufacturing Acceleration Process (REMAP) consortium initiated an extensive Pb-free solder reliability program investigating the influence of bismuth as a SAC solder alloy family constituent element addition. The REMAP consortium investigated topics such as solder joint microstructure evolution, solder joint aging, bismuth solid solution strengthening and precipitation hardening behaviors, tin whisker initiation/growth behavior and solder joint reliability.…”

Section: Drop Shockmentioning

confidence: 99%

Pb-Free Solders and Aerospace/Defense (A&D) High Performance Considerations

Rafanelli

Hillman²,

Johnson³

et al. 2023

Journal of SMT

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The Aerospace & Defense (A & D) industries maintain a high level of interest in the expansive amount of work performed in developing and qualifying Pb-free solder alloys. The three main areas of interest continue to be thermal cycle, mechanical shock, and vibration. The past twenty years have seen an unprecedented increase in alloy development such that the concepts of “generations of solders and “families of solders” have been coined to help manage the numerous individual alloys on the market today. This paper will discuss work done with Pb-free solder alloys, many with the addition of constituents focusing on varying property enhancements. The purpose is to provide a “snap shot” summary of progress to date and relate perspectives both as advantages and concerns solely in a constructive manner to aid researchers in planning their next steps in development and qualification of these alloys.

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“…In addition, Bi precipitation induces the recrystallization of the Sn matrix [15] into a homogeneous, equiaxed grain structure (Figure 18). This is likely a result of density and crystal structure mismatch between the Sn and Bi phases (Table 6) -as Sn is softer and more ductile than Bi, it will experience stress due this mismatch.…”

Section: Role Of Bi In Whiskeringmentioning

confidence: 99%

“…Recrystallization of Violet after aging[15]; (a) As cast and (b) after aging at 125°C for 100 hours.…”

mentioning

confidence: 99%

Tin Whisker Formation on Small Outline Transistors Assembled Using Bismuth-Containing Lead-Free Solder Alloys After Long-Term Ambient Temperature, High Humidity Storage Part 2: Statistical Analysis

et al. 2020

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With the introduction of environmental legislation such as the Restriction of Hazardous Substances (RoHS), lead (Pb)-free materials have made their way into the electronics manufacturing industry. One issue that has emerged is that Pb-free solder alloys can initiate and grow tin whiskers under specific conditions. These whiskers are thin, highly conductive filaments which have the potential to grow and can cause field failures in many applications. Most concerning with respect to tin whiskering are high reliability applications such as aerospace, automotive, and medical. Bismuth (Bi) is being considered for inclusion in solder alloys to replace the current industry standard (SAC 305) and provide improved thermomechanical and vibration reliability. In this paper, we discuss whisker formation of several Bi-bearing alloys after long-term (12,000 hours), ambient high humidity (25°C/85% RH) storage. Three alloys containing Bi, in addition to SAC 305 (Sn-3.0Ag-0.5Cu), were considered. These alloys were Violet (Sn-2.25Ag-0.5Cu-6.0Bi), Sunflower (Sn-0.7Cu-7.0Bi), and Senju (Sn-2.0Ag-0.7Cu-3.0Bi). The boards were fabricated with electroless nickel immersion gold (ENIG) and immersion tin (ImmSn) finishes and populated with parts having Cu and Fe42Ni alloy leads and chip parts, with half of assemblies cleaned and half cleaned and contaminated with low levels of NaCl. This paper is the second in a series of three in which we share quantitative statistical analysis from the whisker inspection of the small outline transistor (SOT) components. It was found that on ImmSn surface finishes, the longest whiskers were found on SAC, however the longest whiskers were found on Bi-bearing alloys for ENIG. In addition, whiskers were found to generally grow in regions where the tin coverage is thin, and, on ENIG-finished assemblies, near the PCB, likely due to galvanic corrosion between the solder and the finish chemistry.

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Thermal Preconditioning and Restoration of Bismuth-Containing, Lead-Free Solder Alloys

Cited by 13 publications

References 16 publications

Precipitation and coarsening of bismuth plates in Sn–Ag–Cu–Bi and Sn–Cu–Ni–Bi solder joints

Precipitation and coarsening of bismuth plates in Sn–Ag–Cu–Bi and Sn–Cu–Ni–Bi solder joints

Pb-Free Solders and Aerospace/Defense (A&D) High Performance Considerations

Tin Whisker Formation on Small Outline Transistors Assembled Using Bismuth-Containing Lead-Free Solder Alloys After Long-Term Ambient Temperature, High Humidity Storage Part 2: Statistical Analysis

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