Solder ball reliability assessment of WLCSP — Power cycling versus thermal cycling

Rahangdale, Unique; Conjeevaram, Bhavna; Doiphode, Aniruddha; Rajmane, Pavan; Misrak, Abel; Sakib, A R Nazmus; Agonafer, Dereje; Nguyen, Luu; Lohia, Alok; Kummerl, Steven

doi:10.1109/itherm.2017.7992640

Cited by 7 publications

(5 citation statements)

References 5 publications

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“…Factors such as PCB thickness & copper density, solder alloy choice, type of organic laminate material, glass weave density, and mechanical hardware induced strain of the fi nished assembly can all affect the long-term solder joint reliability related to solder fatigue however any accelerated stress testing analysis performed without consistent solder joint quality will result in confounding data [7][8][9][10][11][12]. In order to better understand the variables that affect BTC package solder joint geometries a test vehicle was designed allowing for different variables to be tested.…”

Section: Experimental Setup Pcb Test Vehicle Configurationmentioning

confidence: 99%

Freeze Frame Reflow to Enhance Yields for Advanced Low-Profile Bottom Terminated Packages

Kummerl,

Sreenivasan,

Paku

et al. 2023

Journal of SMT

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Today, designers are demanding an overall form-factor reduction to save board space, increase functionality, and allocate more circuit board real estate toward end-user applications – all with less space allocated to power management where not just the X-Y shrink but the 3D volumetric shrink is required. Unlike most gull wing style leaded packages, QFNs (Quad Flat Pack No lead packages) also known as BTCs (Bottom Terminated Components) have coplanar terminals below the package body to answer this ever-decreasing form-factor requirement. The final standoff in these QFN style packages are dictated by the solder joint geometry formed. Within this advanced package family also finding a similar trend are power WCSPs (Wafer Chip Scale Packages) where traditional solder spheres are being replaced with low profile interconnects in expanded and asymmetrical geometries. This paper presents factors that influence advanced low standoff package solderability performance with the use of video microscopy and live in situ X-ray reflow. To reflect the QFN board assemblies that are typically designed a series of layouts were implemented across different coupon test boards. Assembled coupon test board were designed by varying 1) through hole via design, 2) solder mask tenting techniques, 3) periphery and center thermal pad printed solder joint volumes, 4) no-clean and water-soluble solder paste flux chemistry all using SAC 305 alloy and type 4.5 powder size. One case study using live in-situ X-ray system will explain the effects of a QFN land pattern layout incorporating vias in the center thermal pad with solder mask tenting over the via openings located on the back of the PCB. In another configuration vias were removed from the center thermal pad and vacuum reflow performed during the liquidus phase of the solder with an explanation of why some of the voids remained. The first and second order results presented within this paper have practical implications and from their observations a novel process evaluation technique coined as Freeze Frame Reflow (FFR) was developed. In the last case study presented, an advanced mrQFN (multi-row QFN) package is investigated for factors affecting yields. FFR is then implemented resulting in an increase in yield further demonstrating the benefits this new & novel technique can offer.

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Section: Experimental Setup Pcb Test Vehicle Configurationmentioning

confidence: 99%

Freeze Frame Reflow to Enhance Yields for Advanced Low-Profile Bottom Terminated Packages

Kummerl,

Sreenivasan,

Paku

et al. 2023

Journal of SMT

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“…They indicated that the sorting genetic algorithm facilitates to search for the Pareto-optimal solutions and the best design. Rahangdale (2017a, 2017b) performed a comparative study between effects of power and thermal loadings on the solder balls and found that the internal heat generation from power cycling shows more failure compared to thermal cycling. In another work (Li et al , 2009), the reliability assessment of solder interconnections under thermal and power cycling revealed that the fatigue life in the power cycling test was much longer than that in the thermal cycling test.…”

Section: Introductionmentioning

confidence: 99%

“…Laurila (2007) also carried out a comparative study and found that the recrystallization-assisted crack nucleation and propagation happen earlier in the solder exposed to the power cycling test compared to the thermal loading. Another work showed that the printed circuit board (PCB) thickness influences the reliability of solder joints under both of power and thermal loadings (Rahangdale, 2017a, 2017b). Shao (2018) revealed that the application of computational fluid dynamics simulation along with the finite element analysis improved life prediction of solder joints in 2.5D Package under both thermal and power cycling.…”

Section: Introductionmentioning

confidence: 99%

Reliability assessment of ball grid array joints under combined application of thermal and power cycling: solder geometry effect

Kumar¹,

Kuzichkin

Siddiqi

et al. 2020

SSMT

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Purpose This study aims to investigate simultaneous power and thermal loading. Design/methodology/approach Finite element method simulations coupled with experiments. Findings The effects of power cycling have been determined. Originality/value This paper aims to testify the combined effects of thermal and power cycling loads on the reliability of solder ball joints with barrel- and hourglass-type geometries in an electronic system. The finite element simulation outcomes showed that the maximum strain energy was accumulated at the edges of barrel-type solder, whereas the hourglass-type was vulnerable at the necking side. It was also found that the hourglass-type solder showed a reliable behavior when the sole thermal cycling was exerted to the electronic system, whereas the barrel-type solder was a better choice under simultaneous application of thermal and power loadings. The experimental results also confirmed the finite element simulation and indicated that the solder joint reliability strongly depends on the geometry of interconnection in different operating conditions. An extensive discussion was presented to shed light on the paramount importance of combined thermal/power cycling on the reliability of solder joints.

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“…However, the limitations of WLCSP are the low number of input/output (I/O) and unrealizable 3-dimensional (3D) routing. The WLCSP also shows poor performance of thermal-mechanical [7,8] when it works on the printed circuit board (PCB). The fan-out wafer level packaging technology [10,11] is developed to compensate the issues of wafer level chip scale packaging technology.…”

Section: List Of Tablesmentioning

confidence: 99%

“…8 shows the flexure strength of Yeung BBT. We can find that the chemical wet etching process improves the silicon die strength significantly.…”

mentioning

confidence: 99%

Advanced flip chip and wafer level packages for 2.5D and 3D IC package technology

Xu¹

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The demand of electronic product explodes in recent years, and the trend of electronic product is portable, multifunctional and budget currently. The fan-out wafer level packaging technology is a kind of wafer level packaging technology, and it becomes more and more attractive and popular because of its flexibility to integrate diverse devices in a very small form factor. The fan-out wafer level packaging technology has the advantages of high density of input/output, minimal package size and low cost. The fan-out wafer level package (FOWLP) is usually used to volume sensitive devices such as mobile phones and wearables. However, the strength of ultrathin FOWLP is low, and the low package strength often leads to crack issues. Therefore, the study of strength behavior of FOWLP is essential. FOWLP is made up of various materials and thus the proper structure design and material selection are important to meet the reliability requirement. The FOWLP strength is evaluated by the experimental method and numerical method. We confirm three significant characteristics of FOWLP strength from the experimental work. The wafer grinding process, FOWLP dimension and thermal factor affect the FOWLP strength significantly. The numerical work proves that the flexure strength of over-molded structure FOWLP is higher than the flexure strength of other structure FOWLPs with the same package thickness. Two theoretical models of FOWLP strength are proposed. These two models are based on the location of FOWLP initial fracture point. The comparison of FOWLP strength model with experiment results and simulation results shows that they are identical. A new theoretical model of FOWLP fatigue crack growth is proposed. This model additionally considers the effect of thermal factor on the FOWLP fatigue crack growth. ii ACKNOWLEDGMENT The author would like to express his gratitude to the people who have given their hands throughout the author's Ph.D. study journey. The author's thanks and appreciations also extend to: Associate Professor Zhong Zhaowei, the author's supervisor. He shows his generosity, encouragement and patience in guiding the author in various aspects during the Ph.D. study. He is also always trying to motivate and encourage the author to reach his goal. Dr. Choi Won Kyoung, the author's co-supervisor. She shows her attention, suggestion and guidance to the author. She also shares a lot of her knowledge and experience on the aspect of advanced packaging with the author. She is also always explaining the author's doubts throughout the project. Ms. Heng Chee Hoon, NTU biological laboratory assistant manager, Mr. Leong Kwok Phui, NTU materials laboratory manager and Ms. Yeong Peng Neo, NTU materials laboratory Executive. They show their generosity and patience in guiding and teaching the author to use the laboratory machines. They also provide the technical support to the author's experiment from hardware to software. Ms. Lee Koon Fong, mechatronics laboratory manager. She kindly and tremendously helps the author to purchase necess...

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Solder ball reliability assessment of WLCSP — Power cycling versus thermal cycling

Cited by 7 publications

References 5 publications

Freeze Frame Reflow to Enhance Yields for Advanced Low-Profile Bottom Terminated Packages

Freeze Frame Reflow to Enhance Yields for Advanced Low-Profile Bottom Terminated Packages

Reliability assessment of ball grid array joints under combined application of thermal and power cycling: solder geometry effect

Advanced flip chip and wafer level packages for 2.5D and 3D IC package technology

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