Understanding of Void Formation in Cu/Sn-Sn/Cu System During Transient Liquid Phase Bonding Process Through Diffusion Modeling

Bordère, S.; Feuillet, Emilien; Diot, Jean-Luc; Langlade, Renaud de; Silvain, Jean François

doi:10.1007/s11663-018-1391-8

Cited by 21 publications

(15 citation statements)

References 37 publications

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“…The microstructural, elemental, and chemical analysis of the Cu-SAC bonding via the TLP process and previous studies were then correlated to propose a bonding mechanism, including the Cu3Sn coated layer effect. Note that the following mechanisms rely on the experimental analysis presented in this paper and previously published kinetics and thermodynamics simulations [8]. The simulations are based upon Fick's diffusion law of the different elements and phases present in the bonding process and corroborated to interfacial mass transport equations.…”

Section: The Bonding Mechanism Of Cu-sac Joints Having or Not The Cu3...mentioning

confidence: 86%

“…It was observed that the Cu6Sn5 grows into a rounded grains morphology called scallops from both Cu/Sn bonding interfaces [15]. Later, such grains development led to a Cu6Sn5 impingement before the total Sn consumption, thus forming pores in the solder joint [2,8,16]. Naturally, pores degrade the IMC's thermal and mechanical properties and deteriorate its reliability [17].…”

Section: Introductionmentioning

confidence: 99%

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Controlling Interfacial Exchanges in Liquid Phase Bonding Enables Formation of Strong and Reliable Cu–Sn Soldering for High-Power and Temperature Applications

Silvain

Constantin

Heintz

et al. 2021

ACS Appl. Electron. Mater.

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Developing solder joints capable of withstanding high-power density, hightemperature, and significant thermomechanical stress is essential to further develop electronic devices performances. This study demonstrates an effective route of producing dense, robust, and reliable high-temperature Cu-Sn soldering by modifying the interfacial exchange during a transient liquid phase bonding (TLP) process. Our approach relies thus on altering internal phenomena (diffusion and transport of reactive species) rather than classical external TLP bonding parameters (e.g., time, temperature, and pressure). By adding a Cu3Sn coated layer between Cu and Sn before the TLP process, a fast dissolution of Cu in liquid Sn is achieved, altering undesired Cu6Sn5 scallop grains impingement and promoting their uniform growth within the liquid. A bonding and pore formation mechanism of the solder with or not the Cu3Sn coated layer is proposed based on experimental and theoretical analysis. The developed TLP joint possesses a shear stress resistance of more than 80 MPa with a thermal cycle endurance 2 superior to 1200 (-45 to 180 ºC), making it highly reliable compared to a classical solder joint with shear and thermal cycling resistance of 45 MPa and 500, respectively. The developed approaches provide, thus, an easy, affordable, and scalable method of producing hightemperature and durable Cu-Sn joint for high-power module applications.

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Section: The Bonding Mechanism Of Cu-sac Joints Having or Not The Cu3...mentioning

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Controlling Interfacial Exchanges in Liquid Phase Bonding Enables Formation of Strong and Reliable Cu–Sn Soldering for High-Power and Temperature Applications

Silvain

Constantin

Heintz

et al. 2021

ACS Appl. Electron. Mater.

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“…By (8), for the reaction (5) between Sn and Cu the ratio of volumes we find J tr ¼ 1:44 (44% volume expansion) if n ¼ 0 (solid skeleton approach) and J tr ¼ 0:92 (8% volume shrinkage) if n ¼ À1. To our knowledge the question about the value of the transformation strain accompanying IMC formation remains open and estimates of the relative volume change are in the range from À10%, 13,29,30 up to þ44%. 31,32 Further we fit model parameters for n ¼ À0:5, which corresponds to volume ratio J tr ¼ 1:18.…”

Section: Chemical Affinity Tensor and General Problem Statementmentioning

confidence: 99%

“…where x n is given by (30). The solution of the diffusion problem finally gives the concentration at the reaction front as a function of the reaction front position…”

Section: Analytical Solution Of a Model Problemmentioning

confidence: 99%

Experimental and Theoretical Studies of Cu-Sn Intermetallic Phase Growth During High-Temperature Storage of Eutectic SnAg Interconnects

Morozov

Freidin

Klinkov

et al. 2020

Journal of Elec Materi

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In this paper, the growth of intermetallic compound (IMC) layers is considered. After soldering, an IMC layer appears and establishes a mechanical contact between eutectic tin-silver solder bumps and Cu interconnects in microelectronic components. Intermetallics are relatively brittle in comparison with copper and tin. In addition, IMC formation is typically based on multi-component diffusion, which may include vacancy migration leading to Kirkendall voiding. Consequently, the rate of IMC growth has a strong implication on solder joint reliability. Experiments show that the intermetallic layers grow considerably when the structure is exposed to heat. Mechanical stresses may also affect intermetallic growth behavior. These stresses arise not only from external loadings but also from thermal mismatch of the materials constituting the joint, and from the mismatch produced by the change in shape and volume due to the chemical reactions of IMC formation. This explains why in this paper special attention is being paid to the influence of stresses on the kinetics of the IMC growth. We develop an approach that couples mechanics with the chemical reactions leading to the formation of IMC, based on the thermodynamically sound concept of the chemical affinity tensor, which was recently used in general statements and solutions of mechanochemistry problems. We start with a report of experimental findings regarding the IMC growth at the interface between copper pads and tin based solder alloys in different microchips during a high temperature storage test. Then we analyze the growth kinetics by means of a continuum model. By combining experiment, theory, and a comparison of experimental data and theoretical predictions we finally find the values of the diffusion coefficient and an estimate for the chemical reaction constant. A comparison with literature data is also performed.

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“…Among others, we can mention the solidification of pure liquid processes where energy diffusion is the main driving force, or precipitation/dissolution processes in multi-component systems involving a solid/liquid or a solid/solid interface where mass transport by diffusion has a large impact on microstructure evolutions. This is case in metallurgy during solid state annealing processes, where phase transformations have to be controlled in order to obtain the volume fraction of phases optimizing the mechanical properties [1,2]; and also during transient liquid phase phenomena involving diffusion-induced solidification, leading in some cases to detrimental pore formation [3,4]. In this broad field of diffusion processes involving complex coupling of driving forces, we focus in this paper on the particular case of diffusion-controlled phase transformations involving diffusion of components at constant temperature and pressure.…”

Section: Introductionmentioning

confidence: 99%

Numerical modeling of diffusion-controlled phase transformation using the Darken method: Application to the dissolution/precipitation processes in materials

Bordère

Glockner²

2021

Computational Materials Science

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Many material phase transformations are controlled by mass transport induced by diffusion. To better understand such transformations, numerous modeling strategies at the scale of the moving interfaces exist, with their strengths and weaknesses. Phase field approaches are based on diffuse interfaces that do not require any interface tracking, as opposed to those based on fixed-grid sharp interface tracking. In the case of binary two-phase systems, in this paper we address the key point of the mass balance equation at the interface involving a concentration jump, which determines the interface moving velocity. We propose a unique diffusion equation for both phases and their interface, based on the component's chemical potentials which are continuous throughout the interface and a smooth volume-of-fluid phase representation. This model is achieved in the framework of the Darken method, which involves intrinsic diffusion of components and a drift velocity to which all compounds are subjected. This drift velocity is shown to be that of the interface displacement as well. This methodology is verified for 1D and 3D dissolution/precipitation problems and has a first-order spatial convergence. The 3D simulations of precipitation and dissolution processes of more complex microstructures clearly show a bifurcation of the particle morphology from the initial spherical shape when the diffusion edges of each particle interact with each other. An extension of the diffusion potential to mechanical driving forces should make it possible to deal with mechano-chemical coupling of mass transport.

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Understanding of Void Formation in Cu/Sn-Sn/Cu System During Transient Liquid Phase Bonding Process Through Diffusion Modeling

Cited by 21 publications

References 37 publications

Controlling Interfacial Exchanges in Liquid Phase Bonding Enables Formation of Strong and Reliable Cu–Sn Soldering for High-Power and Temperature Applications

Controlling Interfacial Exchanges in Liquid Phase Bonding Enables Formation of Strong and Reliable Cu–Sn Soldering for High-Power and Temperature Applications

Experimental and Theoretical Studies of Cu-Sn Intermetallic Phase Growth During High-Temperature Storage of Eutectic SnAg Interconnects

Numerical modeling of diffusion-controlled phase transformation using the Darken method: Application to the dissolution/precipitation processes in materials

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