iNEMI project on process development of BISN-based low temperature solder pastes — Part II: Characterization of mixed alloy BGA solder joints

Fu, Haley; Aspandiar, Raiyo; Chen, Jimmy; Cheng, Shihua; Chen, Qin; Coyle, Richard; Feng, Sophia; Hardin, Bill; Krmpotich, Mark; Mokler, Scott; Radhakrishnan, Jagadeesh; Ribas, Morgana; Sandy-Smith, Brook; Tang, Kok Kwan; Wu, Greg; Zhang, Anny; Zhen, Wilson

doi:10.23919/panpacific.2018.8318989

Cited by 19 publications

(6 citation statements)

References 4 publications

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“…Comparing conventional Sn37Pb eutectic solder (183 • C), the higher melting temperature of SAC305 (217-221 • C) limits its application when facing miniaturization challenges associated with emerging ultra-mobile computing, wearable devices, and the Internet of Things (IoT) markets [11]. Therefore, further studies have been carried out globally by industrial as well as academic consortiums on new Pb-free alternatives [12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Improved Reliability and Mechanical Performance of Ag Microalloyed Sn58Bi Solder Alloys

Ren

Collins

2019

Metals

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Ag microalloyed Sn58Bi has been investigated in this study as a Pb-free solder candidate to be used in modern electronics industry in order to cope with the increasing demands for low temperature soldering. Microstructural and mechanical properties of the eutectic Sn58Bi and microalloyed Sn57.6Bi0.4Ag solder alloys were compared. With the addition of Ag microalloy, the tensile strength was improved, and this was attributed to a combination of microstructure refinement and an Ag3Sn precipitation hardening mechanism. However, ductility was slightly deteriorated due to the brittle nature of the Ag3Sn intermetallic compounds (IMCs). Additionally, a board level reliability study of Ag microalloyed Sn58Bi solder joints produced utilizing a surface-mount technology (SMT) process, were assessed under accelerated temperature cycling (ATC) conditions. Results revealed that microalloyed Sn57.6Bi0.4Ag had a higher characteristic lifetime with a narrower failure distribution. This enhanced reliability corresponds with improved bulk mechanical properties. It is postulated that Ag3Sn IMCs are located at the Sn–Bi phase boundaries and suppress the solder microstructure from coarsening during the temperature cycling, hereby extending the time to failure.

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Section: Introductionmentioning

confidence: 99%

Improved Reliability and Mechanical Performance of Ag Microalloyed Sn58Bi Solder Alloys

Ren

Collins

2019

Metals

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“…[18] Bismuth is of great interest for a SnBi solder alloy alternative to SnPb in the years surrounding the RoHS directive mainly for its cost, availability and environmental impact. [1,2,4,6,[10][11][12][13][14] Promising results of tensile strength and creep resistance of eutectic SnBi which melts at 138°C compared to be better than that of SnPb same properties. [19][20][21][22][23] Still the eutectic SnBi was discredited as a viable solution from poor mechanical shock and fatigue resistance from the very nature of the element Bismuth is known to be more brittle than most.…”

Section: Literature Review Prior Low Temperature Solder Studiesmentioning

confidence: 99%

Properties of Mixing SAC Solder Alloys with Bismuth-Containing Solder Alloys for a Low Reflow Temperature Process

Swanson,

Anselm

2023

Journal of SMT

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The subject of extensive research has been the establishing of lower temperature soldering of electronic assemblies that are similar to the once common yet still preferred eutectic Tin-Lead (SnPb) soldering processes that are below 217˚C. This research measured and compared the mixing mechanisms of paste and ball dissolution. Mixed soldered assemblies will have different dissolution results that are dependent on the peak reflow temperature. The hypothesis for this experiment was to determine the relationship of various times above the melting point of low temperature solders containing Bismuth. The results measured are from solder joints of both SAC305 and Bismuth containing solders formed at lower process temperatures compared to the standard high temperatures which peak at 230˚C-260˚C. The Bismuth containing solders evaluated start with the highest to lowest weight percentage of Bismuth, the eutectic 58Bismuth/42Tin (58Bi/42Sn), 57Bi/42Sn/1Ag and a propriety alloy that has a lower Bismuth content along with various micro alloys, defined as 40-58Bi/Sn/X (X representing proprietary micro alloys or doping). The assembly was with an 18mil 96.5Tin/3.0Silver/0.5Copper (SAC305) solder ball mixed with each solder paste. These solder alloys were exposed to three different peak temperatures 180˚C, 195˚C, 205˚C. Another reflow profile attribute of focus was times above 138˚C - the melting point of the eutectic Sn58Bi alloy, this term used throughout the study is referred to Time Above Melting (TAM). The ball and paste assembly used the times above melting of 120sec and 240sec to represent process extremes and verify their significance on improving mixing level results. The average mixing % levels were recorded and compared for each solder joint combination to test the theory that the solder paste solidifies during the time above melting (TAM) within the reflow oven. [1] This experiment effectively demonstrates that the reflow profile parameter for time above melting has limited effectiveness in additionally mixing the paste with the BGA solder ball. Optimization of mixing percentages will need to be achieved by optimizing the paste and ball volumes.

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“…Other studies examined the collapse of the BGA solder joints after reflow. The collapse of BGA solder balls was analyzed by measuring the length of a diagonal line in a solder ball (edge–center–edge) [ 7 ] or by measuring the stand-off height after reflow [ 9 ]. Several works have also predicted the shape (geometry) of a BGA ball after one or several reflows using the finite element method [ 10 , 11 , 12 , 13 , 14 , 15 ] or computational fluid dynamic simulation [ 16 ].…”

Section: Introductionmentioning

confidence: 99%

A Novel Approach for Temperature-Induced Ball Grid Array Collapse Observation

Sorokina,

Dušek,

Bušek

2024

Materials

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This study presents a new approach to investigating the impact of repeated reflow on the failure of ball grid array (BGA) packages. The issue with the BGA package collapse is that the repeated reflow can lead to short circuits, particularly for BGAs with a very fine pitch between leads. A novel approach was developed to measure the collapse of BGA solder balls during the melting and solidification process, enabling in situ measurements. The study focused on two types of solders: Sn63Pb37 as a reference, and the commonly used SAC305, with measurements taken at various temperatures. The BGA samples were subjected to three different heating/cooling cycles in a thermomechanical analyzer (TMA) at temperatures of 250 °C, 280 °C, and 300 °C, with a subsequent cooling down to 100 °C. The results obtained from the TMA indicated differences in the collapse behavior of both BGA solder alloys at various temperatures. Short circuits between neighboring leads (later confirmed by an X-ray analysis) were also recognizable on the TMA. The novel approach was successfully developed and applied, yielding clear insights into the behavior of solder balls during repeated reflow.

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iNEMI project on process development of BISN-based low temperature solder pastes — Part II: Characterization of mixed alloy BGA solder joints

Cited by 19 publications

References 4 publications

Improved Reliability and Mechanical Performance of Ag Microalloyed Sn58Bi Solder Alloys

Improved Reliability and Mechanical Performance of Ag Microalloyed Sn58Bi Solder Alloys

Properties of Mixing SAC Solder Alloys with Bismuth-Containing Solder Alloys for a Low Reflow Temperature Process

A Novel Approach for Temperature-Induced Ball Grid Array Collapse Observation

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