Growth Kinetics Of Intermetallic Compounds Research Articles

Interfacial Reactions between Sn-Based Solders and n-Type Bi2(Te,Se)3 Thermoelectric Material.

This study investigated the interfacial reactions between n-type Bi2(Te,Se)3 thermoelectric material, characterized by a highly-oriented (110) plane, and pure Sn and Sn-3.0Ag-0.5Cu (wt.%) solders, respectively. At 250 °C, the liquid-state Sn/Bi2(Te,Se)3 reactions resulted in the formation of both SnTe and BiTe phases, with Bi-rich particles dispersed within the SnTe phase. The growth of the SnTe phase exhibited diffusion-controlled parabolic behavior over time. In contrast, the growth rate was considerably slower compared to that observed with p-type (Bi,Sb)2Te3. Solid-state Sn/Bi2(Te,Se)3 reactions conducted between 160 °C and 200 °C exhibited similar interfacial microstructures. The SnTe phase remained the primary reaction product, embedded with tiny Bi-rich particles, revealing a diffusion-controlled growth. However, the BiTe layer had no significant growth. Further investigation into growth kinetics of intermetallic compounds and microstructural evolution was conducted to elucidate the reaction mechanism. The slower growth rates in Bi2(Te,Se)3, compared to the reactions with (Bi,Sb)2Te3, could be attributed to the strong suppression effect of Se on SnTe growth. Additionally, the interfacial reactions of Bi2(Te,Se)3 with Sn-3.0Ag-0.5Cu were also examined, showing similar growth behavior to those observed with Sn solder. Notably, compared with Ag, Cu tends to diffuse towards the interfacial reaction phases, resulting in a high Cu solubility within the SnTe phase.

The growth behavior and kinetics of intermetallic compounds in Cu–Al interface at 600°C–800 °C

Due to the low production cost and light weight, copper-clad aluminum conductors show great potential value in the field of power transmission, while the phase structure and organizational changes at the Cu–Al interface in high-temperature environments have a great impact on the electrical and mechanical properties. In this paper, Cu–Al diffusion couples are prepared to study the diffusion process, microstructure, and growth kinetics of intermetallic compounds (IMCs) in Cu–Al interface during heating from 600 °C to 800 °C, and the mechanical and electrical properties of Cu–Al diffusion couples are discussed. The results show that after heat treatment, IMC layers are formed at the Cu–Al interface and the Al-side is composed of CuAl and CuAl2, in which the CuAl phase transforms from long to thick dendrites with the increase of temperature, and finally grows into a “popcorn” form. The IMCs at the Cu–Al interface from the Cu side to the Al side are in the order of Cu3Al layer, Cu9Al4 layer, Cu3Al2 layer and CuAl layer, among which the Cu3Al2 layer is the thickest (168.42 μm at 700 °C), while the Cu3Al layer is the thinnest (37.32 μm at 700 °C). The kinetic calculations show that the diffusion layer grows up rapidly, which is caused by the generation of liquid-phase during the heating process, leading to the acceleration of the diffusion of Cu and Al. The kinetic factor of the Cu3Al2 layer is the largest (n = 0.69), causing the fastest growth rate of the Cu3Al2 layer, while the Cu3Al layer shows the largest activation energy for diffusion and the smallest diffusion rate (Q = 9.48 kJ/mol, D0 = 2.06 × 10−1 m2/s), therefore its growth rate is the slowest. Based on the thermodynamic calculations and the Cu–Al phase diagram, a growth mechanism of the Cu–Al interface is proposed, the formation sequence of IMCs at the Cu–Al interface is Cu9Al4, CuAl, Cu3Al2 and Cu3Al. The formation of IMCs layer at the Cu–Al interface leads to a significant increase in the hardness of Cu–Al samples (the hardness of the Cu3Al2 is 10 times higher than that of Cu) and an obvious decrease in electrical conductivity (the electrical resistivity of Cu–Al is 5 orders of magnitude higher than that of Cu), affecting its application in the electrical industry.

Correction: Microstructure evolution and growth kinetics of intermetallic compound in SAC305/Ag and SAC305/Cu solder joints during solid-state aging

Correction: Microstructure evolution and growth kinetics of intermetallic compound in SAC305/Ag and SAC305/Cu solder joints during solid-state aging

Microstructure evolution and growth kinetics of intermetallic compound in SAC305/Ag and SAC305/Cu solder joints during solid-state aging

Microstructure evolution and growth kinetics of intermetallic compound in SAC305/Ag and SAC305/Cu solder joints during solid-state aging

Effect of reaction temperature and holding time on the interfacial microstructure of Al–Si–Mg/Cu bimetals manufactured by hot-dip aluminizing

This study investigates the effects of reaction temperature and holding time on intermetallic compounds (IMCs) at the Al–Si–Mg/Cu bimetals interface fabricated by hot-dip aluminizing. Previous research has demonstrated that the presence of IMC layers in Al–Si–Mg/Cu bimetals significantly increased the interface hardness. This study aims to achieve a continuous change in hardness at the interface by forming Cu3Al layers, thus exhibiting the lowest hardness and highest ductility among the Al–Cu IMCs. The thickness and morphology of the Al–Cu IMC layer depend on the reaction temperature and holding time. Al–Cu intermetallic phases with higher Cu contents, such as Cu3Al, Cu9Al4, Cu3Al2, CuAl, and CuAl2, were closer to the Cu surface. The formation of Cu3Al leads to continuous changes in the hardness of the Cu and IMC layers. Furthermore, the growth kinetics of IMCs and their formation mechanisms are discussed. The results indicate that hot-dip aluminizing is an effective method for controlling the composition and thickness of the IMC layer to achieve a continuous change in the interfacial hardness.

Kinetics of Cu6Sn5 and Cu3Sn intermetallic compounds growth and isothermal solidification during Cu-Sn transient liquid phase sintering process

The kinetics of Cu-Sn intermetallic compounds (IMCs) growth relates to the materials preparation, process regulation and reliability prediction in the new energy field and electronic packaging industry. As a typical instance that Cu-Sn IMCs are involved with, this work investigated the kinetics of Cu-Sn IMCs growth and isothermal solidification of Cu-Sn transient liquid phase sintering (TLPS) process for high temperature resistant packaging of the third-generation semiconductors power devices. A three-dimensional kinetics model of Cu/Sn solid/liquid interfacial reaction and the corresponding kinetics equations of Cu6Sn5 and Cu3Sn growth was established. Based on Cu-Sn IMCs growth kinetics, a parameter ξSn called the residual rate of Sn was defined to characterize the isothermal solidification kinetics of Cu-Sn TLPS process. By measuring the volume fraction of Cu and Sn, the quality fraction of residual Cu and Sn and produced Cu-Sn IMCs were determined, and thus the kinetics of Cu-Sn IMCs growth and the isothermal solidification of Cu-Sn TLPS process were experimentally studied to validate the theoretical model. The results showed that the theoretical results predicted by the model were well-matched with experimental results. Besides rising temperature, the kinetics of Cu-Sn IMCs growth and the isothermal solidification can be remarkably accelerated by decreasing Cu particle size. Reducing Sn content does not affect the kinetics of Cu-Sn IMCs growth but helps to shorten the isothermal solidification time of Cu-Sn TLPS process.

Study of growth kinetics of intermetallic compounds at BAl88Si/Cu interface

• The diffusion behavior of the elements at the interface is investigated. • The diffusion reactions of the interface are analyzed. • The growth kinetics of the interfacial compound are analyzed. • The interfacial microstructure evolution model of BAl88Si/Cu are established. In this study, the growth of the intermetallic compounds (IMCs) at the BAl88Si/Cu interface was analyzed and its growth kinetics was investigated. The results reveal that Cu 3 Al, Cu 9 Al 4 , Cu 3 Al 2 and CuAl, four-layer IMCs are formed at the interface due to the interdiffusion of copper elements and aluminum elements. The thickness of the IMCs increases with increasing temperature and holding time, the transition from Cu 3 Al 2 to Cu 9 Al 4 is also observed at 893 K. The activation energies of the Cu 3 Al, Cu 9 Al 4 and total IMCs layers are obtained from the Arrhenius equation and are 127.10 kJ/mol, 189.68 kJ/mol and 184.93 kJ/mol, respectively, which provide a reference for assessing the ease of growth of IMCs.

In Situ Investigation of Microstructural Evolution and Intermetallic Compounds Formation at Liquid Al/Solid Cu Interface by Synchrotron X-ray Radiography.

Synchrotron radiation dynamic imaging technology combined with the static characterization method was used to study the microstructural evolution and the growth kinetics of intermetallic compounds (IMCs) at the liquid Al/solid Cu interface. The results show that the interfacial microstructure can be divided into layered solid diffusion microstructures (AlCu3, Al4Cu9, Al2Cu3 and AlCu) and solidification microstructures (Al3Cu4, AlCu and Al2Cu) from the Cu side to the Al side. Meanwhile, the growth of bubbles formed during the melting, holding and solidification of an Al/Cu sample was also discussed, which can be divided into three modes: diffusion, coalescence and engulfment. Moreover, the growth of AlCu3 and (Al4Cu9 + Al2Cu3) near the Cu side is all controlled by both interfacial reaction and volume diffusion. The growth of Al3Cu4 adjacent to the melt is mainly controlled by the interfacial reaction, which plays a major role in the growth of the total IMCs.

The formation and growth of intermetallic compounds during interdiffusion of Al/Cu bimetals

The diffusion couple technology was used to study the formation and growth of intermetallic compounds (IMCs) of Al/Cu bimetals at the temperature range of 480-540 oC for 5-20 h. The interfacial microstructure formed during interdiffusion and the growth kinetics of IMCs are determined. The results show that four different kinds of IMCs (Al2Cu, AlCu, Al2Cu3 and Al4Cu9) were formed at the Al/Cu interface, which is related to the interfacial diffusion reaction and the migration of phase interfaces. The growth of IMCs is mainly controlled by volume diffusion, and follows a parabolic growth kinetics, i.e. L = kt 1/2. Based on the effective heat of formation model and Gibbs free energy change calculation, the Al2Cu is predicted to form first and the formation sequence of the four IMCs is Al2Cu, Al4Cu9, AlCu and Al2Cu3.

The inhibitory effect of stir zone liquefaction and eutectic-phase formation on the growth of γ/β intermetallics during dissimilar FSW of Al/Mg alloys

Controlling the formation of intermetallic compounds (IMCs) is a critical issue in friction stir welding (FSW) of Aluminum (Al) to magnesium (Mg) alloys. During FSW, AlMg IMCs can form through two mechanisms comprising solid-state diffusion and liquefaction. Two kinds of IMCs can form during FSW of Al/Mg, Al3Mg2 (β) and Al12Mg17(γ). The IMCs produced via the former mechanism are identified as continuous whereas the IMCs produced by the latter typically appear as separate islands inside a matrix of eutectic structures. The present study aims to examine the impact of each morphology on the joint strength. For this purpose, dissimilar FSW of AA1050/AZ31 was carried out in lap configuration. The microstructure of the joints, as well as the fracture surfaces, were studied by scanning electron microscopy (SEM) and joint strength was evaluated by shear tensile testing. It was observed that the IMCs formed via diffusion were detrimental when their thickness exceeded 2 μm. It was also shown that liquefaction during FSW could control the thickness of the continuous IMCs layer. To elucidate this phenomenon, analytical and numerical methods were applied to calculate the growth kinetics of IMCs. It was concluded that the liquefaction phenomenon and the subsequent formation of eutectic structures reduced the activity of elements and thereupon hindered the diffusion rate in the solid state. In this case, although liquefaction raised the overall volume fraction of IMCs, the fracture load increased due to the propagated fracture through the eutectic microstructure rather than the continuous IMC layer.

Growth kinetics analysis of Nb–Al intermetallic compounds interfacial layers based on Nb–Al phase diagram

A model for studying the growth kinetics of intermetallic compounds by means of binary phase diagrams was proposed with some assumptions. The parabolic growth relationship of intermetallic compound is deduced mathematically using analytical solution of diffusion equations and the mass balance law. By comparing the solubility of the adjacent phase in intermetallic compound phase, the predominant parameter controlling the growth kinetics is the solute diffusion coefficient. The diffusion coefficient of Al atoms in intermetallic layers is quantitatively described and the smallest diffusion coefficient is 0.373 × 10−21 m2/s in Nb3Al phase. It is demonstrated intermetallic layers formed at interface indeed inhibit the Nb container being corroded further by TiAl melt, and Nb3Al layer is a dominant factor.

Effect of Si content on interfacial reaction and properties between solid steel and liquid aluminum

The effect of Si content on the microstructures and growth kinetics of intermetallic compounds (IMCs) formed during the initial interfacial reaction (<10 s) between solid steel and liquid aluminum was investigated by a thermophysical simulation method. The influence of Si addition on interfacial mechanical properties was revealed by a high-frequency induction brazing. The results showed that IMCs layers mainly consisted of η-Fe2Al5 and θ-Fe4Al13. The addition of Si reduced the thickness of the IMCs layer. The growth of the η phase was governed by the diffusion process when adding 2 wt.% Si to the aluminum melt. When 5 wt.% or 8 wt.% Si was added to aluminum, the growth was governed by both the diffusion process and interfacial reaction, and ternary phase τ1/τ9-(Al,Si)5Fe3 was formed in the η phase. The apparent activation energies of the η phase decreased gradually with increasing Si content. The joint with pure aluminum metal had the highest tensile strength and impact energy.

Microstructures evolution and growth kinetics of intermetallic compounds in Cu/Sn/Cu system during ultrasonic soldering process

PurposeThis study aims to investigate the effect of ultrasound on interfacial microstructures and growth kinetics of intermetallic compounds (IMCs) at different temperatures.Design/methodology/approachTo investigate the effect of ultrasound on IMCs growth quantitatively, the cross-sectional area of IMCs layers over a confirmed length was obtained for calculating the thickness of the IMCs layer.FindingsThe generation of dimensional difference in normal direction between Cu6Sn5 and its adjacent Cu6Sn5, formation of bossed Cu6Sn5 and non-interfacial Cu6Sn5 in ultrasonic solder joints made the interfacial Cu6Sn5 layer present a non-scallop-like morphology different from that of traditional solder joints. At 260°C and 290°C, the Cu3Sn layer presented a wave-like shape. In contrast, at 320°C, the Cu3Sn in ultrasonic solder joints consisted of non-interfacial Cu3Sn and interfacial Cu3Sn with a branch-like shape. The Cu6Sn5/Cu3Sn boundary and Cu3Sn/Cu interface presented a sawtooth-like shape under the effect of ultrasound. The predominant mechanism of ultrasonic-assisted growth of Cu6Sn5 growth at 260°C, 290°C and 320°C involved the grain boundary diffusion accompanied by grain coarsening. The Cu3Sn growth was controlled by volume diffusion during the ultrasonic soldering process at 260°C and 290°C. The diffusion mechanism of Cu3Sn growth transformed to grain boundary diffusion accompanied by grain coarsening when the ultrasonic soldering temperature was increased to 320°C.Originality/valueThe microstructural evolution and growth kinetics of IMCs in ultrasonically prepared ultrasonic solder joints at different temperatures have rarely been reported in previous studies. In this study, the effect of ultrasound on microstructural evolution and growth kinetics of IMCs was systematically investigated.

Interfacial reactions in Zn4Sb3/titanium diffusion couples

Cheap, environmentally-friendly zinc antimonide is considered more favorable than conventional tellurite-based and skutterudite thermoelectric (TE) materials. Although the highly mobile zinc atoms located in the interstitial sites of the Zn4Sb3 crystalline structure greatly increase the figure of merit (ZT) of TE materials, the high chemical activity of zinc also makes it difficult to find suitable barrier layer and electrode materials. This paper introduces a method of joining titanium with Zn4Sb3 by means of diffusion bonding, in which the critical mutual-interdiffusion phenomenon is prevented. Optimal process parameters for manufacturing TE modules are suggested in this work. The intermetallic compounds (IMCs) that formed at the interface of Zn4Sb3/Ti diffusion couples were proved to be stable at the temperature with the highest conversion efficiency of Zn4Sb3. The growth kinetics of IMCs were also investigated, and the joint strength could be enhanced to 13.9 MPa after long-term reliability tests of 1000 h without deterioration. The results indicated that titanium is feasible barrier layer and electrode material for Zn4Sb3 TE modules.

Effect of high current pulses on solder interfacial reaction and interconnect reliability

The trend of electrification and miniaturization brings the reliability of interconnects to the forefront. The solder joints are subjected to thermo-mechanical mismatch due to the Joule heating and electromigration (EM)-induced degradation under high current stressing conditions. However, most of the studies are limited to lab test samples or lab test conditions, which lack transferability in engineering applications. In this paper, automotive electronic components are studied subjected to field-like current pulse conditions. The work aims to understand the field-relevant failure modes of solder joints exposed to high current stressing via experimental and numerical investigations. Shunt components with and without Ni plating are analyzed in power cycling tests. A polarity effect is observed in the growth of intermetallic compounds (IMCs). The thickness of IMC at the anode exhibits an approximately linear growth with current stressing time, whereas the thickness of IMC at the cathode remains almost unchanged or slightly decreased. Ni, as diffusion barrier, serves to restrain Cu consumption from the terminals of shunts and also reduces Cu mass transport into and within the solder. The net Cu flux at the interface and in the solder is discussed to analyze the IMC growth kinetics. The shunts with Ni plating undergo less EM of Cu and yield longer lifetime. Voids and crack formation are detected in computer tomography (CT) scans and cross-sectional analysis by scanning electron microscopy (SEM). Finite element method (FEM) is implemented to simulate thermo-electro-mechanical fields of the assembly under power cycling test conditions. The distribution of divergence of material flux density corresponds well with the location of voids formation and provides good estimation for the lifetime.

Annealing-induced phase transformations and hardness evolution in Al–Cu–Al composites obtained by high-pressure torsion

Multilayered bulk Al–Cu–Al metal-matrix composite was fabricated by means of high-pressure torsion and subsequent annealing. The resulting composite had a heterogeneous structure consisting of ductile aluminum matrix and hard intermetallic inclusions with a gradient decrease in grain size and layer thickness when moving from the center to the periphery of the sample. Precipitation of $$\hbox {Al}_{2}\hbox {Cu}$$ intermetallic phase was revealed at the edge of the sample in the as-deformed state. Post-deformation annealing initiated the emergence of AlCu and $$\hbox {Al}_{\mathrm {4}}\hbox {Cu}_{\mathrm {9}}$$ intermetallic precipitates with increased hardness compared to strain-induced $$\hbox {Al}_{\mathrm {2}}\hbox {Cu}$$ particles. The growth kinetics of intermetallic compounds was obtained using precise X-ray phase analysis. It was found that the initial growth of intermetallic phases at temperatures 150–210 $$^{\circ }$$ C depends on time $$t^{1/2}$$ , indicating the bulk diffusion-controlled growth. The growth activation energy of Al $$_2$$ Cu and AlCu phases was calculated to be 0.48 and 0.33 eV, respectively. The results obtained contribute to an understanding of the kinetics of annealing-induced growth of intermetallic phases and the corresponding evolution of strength characteristics in Al–Cu–Al composites. It was revealed that thermal treatment regimes resulting in enhanced mechanical properties are associated with moderate time and temperature of annealing, which allows avoiding partial dissolution of strengthening phases. The applied approach of phase kinetics analysis can become the basis for the development of new energy-efficient heat treatment modes of in situ Al-based composites allowing to govern their heterogeneity type and tailoring the mechanical properties of the material.

On stress-affected kinetics of intermetallic compound growth in the presence of electromigration

This paper is concerned with the analytical modeling of an intermetallic compound formation in a eutectic tin solder joint on copper interconnects subjected to an electrical current. We propose a model that couples mechanical stresses, chemical reaction, diffusion, temperature, and electromigration. The kinetics of the chemical reaction fronts of the intermetallic phase formation is investigated based on the notion of the chemical affinity tensor within the small strain approximation. It allows incorporating the influence of stresses and strains on the chemical reaction rate and the normal component of the reaction front velocity in a rational manner. Electromigration is introduced into the model as an additional summand in the total flux of the diffusive constituents, which, in turn, also affects the reaction front velocity. In the considered model, the mechanical stresses arise due to the internal strains produced by the chemical transformation and by the thermal expansion. We formulate a model problem for planar reaction fronts. Within this model, the influence of stresses and electromigration on the reaction front kinetics is studied analytically. Based on the Mean-Time-To-Failure (MTTF) criteria, we calculate the critical thickness of the solder joint and estimate the amount of the accumulated vacancies. We introduce a dimensionless parameter, which characterizes the accumulation of vacancies due to electromigration enhanced diffusion. Finally, we discuss the coupling between the accumulated vacancies and Kirkendall void nucleation.

Effects of bismuth and nickel on the microstructure evolution of Sn-Ag-Cu (SAC)-based solders

The addition of alloying elements to the SAC alloy composition changes the growth behavior of thick Cu6Sn5 and Cu3Sn intermetallic compounds (IMCs) and their influences on mechanical responses. The purpose of this study is to investigate the effects of Bi and Ni on the growth kinetics of interfacial IMCs (Cu6Sn5 and Cu3Sn) and the mechanical strength of the bulk solders during high temperature aging. Reflowed samples of the SAC405 solder balls and the SAC + Bi,Ni solder balls were stored in high-temperature storage (HTS) chamber at 150 °C and 175 °C each for 0 h, 500 hs, 1000 hs, and 2000 hs. The microstructure evolutions of bulk solder and its interfacial areas were evaluated and the associated microhardness values were measured on the solder balls. During aging, the presence of Bi was seen only in the bulk solder region, resulting in increased hardness by a factor of ∼ 2 and resistance to the age softening due to solid solution strengthening. On the other hand, Ni was observed in both the solder ball and IMC regions. After aging at 150 °C, SAC + Bi,Ni solder balls had a thinner Cu3Sn IMC layer at its interface when compared to that in SAC solders with no Ni. At 175 °C, however, Ni addition did not decrease the growth of Cu3Sn. Long aging (2000 h) of the SAC405 sample at 175 °C resulted in the complete consumption of the Cu layer, which was slowed in SAC + Bi,Ni. The presence of Bi and Ni, therefore, show the potential to improve the reliability of the SAC solder ball joint during aging by restricting the solder deformation and the growth of the Cu3Sn layer.

Performance and reliability of Al2O3 nanoparticles doped multicomponent Sn-3.0Ag-0.5Cu-Ni-Ge solder alloy

The effect of Al2O3 nanoparticles addition on melting, microhardness, microstructural, and mechanical properties of multicomponent Sn-3Ag-0.5Cu-0.06Ni-0.01Ge (SACNiGe) solder alloy was investigated. The shear strength of the capacitor assemblies under varying high-temperature environments for different nanocomposites was assessed and the reliability of the joint was determined using Weibull analysis. The SACNiGe solder doped with 0.01 and 0.05 wt% Al2O3 nanoparticles to prepare nanocomposites and tested on the solder joints for their performance and reliability under different thermal conditions. Plain copper and NiP layer coated substrates were used to investigate the effect of different surface finish on the joint reliability. The addition of ceramic nanoparticles in small amounts did not affect the melting parameters of the solder. In comparison with the bare solder alloy, nanocomposites yielded about 20% increase in tin-climb height and 14% higher microhardness. The dispersion of ceramic nanoparticles in the matrix and presence of Ni and Ge elements in the solder resulted in substantial microstructure refinement and about 24% supression in intermetallic compounds (IMCs) growth at the joint interface. In comparison with the bare Cu substrate, the NiP coating on the substrate provided a strong diffusion barrier, promoted thin and complex (Cu, Ni)6Sn5 IMC layer formation at the interface, and significantly retarded the IMC growth kinetics under elevated temperature conditions. Under varying thermal conditions, nanoparticles doped solder compositions showed about 20% increase in the joint shear strength value. The reliability of joints improved appreciably with the addition of 0.05 wt% Al2O3 nanoparticles in the solder. Samples with SACNiGe+0.05Al2O3 nanocomposite reflowed on NiP coating showed about 32% higher reliability than that on the uncoated-copper substrate. The SACNiGe solder joint performance and reliability could be significantly improved by minor weight percent addition of Al2O3 nanoparticles in the presence of NiP coating on the substrate.

Ultra-thin intermetallic compound formation in microbump technology by the control of a low Zn concentration in solder

We report here the extremely slow intermetallic compound (IMC) growth kinetics in the reflow reaction between a Sn-based solder of SnBiIn-2 at.% Zn and Cu. The solder has a melting point about 90 °C, and after reflow for 5 min on Cu at 120 °C, the formed IMC was Cu5Zn8 with a thickness only about 0.36 μm, which is much thinner than the IMC in nowaday packaging technologies. We systematically studied the IMC growth kinetics and built up a model to explain the extremely slow IMC growth rate. The growth kinetics of the reaction is non-parabolic and the activation energy is about 23.8 ± 1.6 kJ/mol. The non-parabolic kinetics is related to the lateral grain growth in IMC during the reactive diffusion along the moving grain boundaries. Our theoretical model shows that the growth rate of Cu5Zn8 compound should be proportional to the square root of Zn initial concentration in solder and a low Zn concentration in the solder will lead to a very slow IMC growth rate. The finding could be applied to control IMC thickness in 3D integrated circuit (3D IC) with micro-bump technology.