Composite Solder Joints Research Articles

Study on the Tensile Creep Behavior of Carbon Nanotubes-Reinforced Sn-58Bi Solder Joints

The microstructure and tensile creep behavior of plain Sn-58Bi solder and carbon nanotubes (CNTs)-reinforced composite solder joints were investigated. The stress exponent n under different stresses and the creep activation energy Q c under different temperatures of solder joints were obtained by an empirical equation. The results reveal that the microstructure of the composite solder joint is refined and the tensile creep resistance is improved by CNTs. The improvement of creep behavior is due to the microstructural change of the composite solder joints, since the CNTs could provide more obstacles for dislocation pile-up, which enhances the values of the stress exponent and the creep activation energy. The steady-state tensile creep rates of plain solder and composite solder joints are increased with increasing temperature and applied stress. The tensile creep constitutive equations of plain solder and composite solder joints are written as $$ \dot{\varepsilon }_{s1} = 14.94\left( {\sigma /G} \right)^{3.7} \exp \left( { - \frac{81444}{RT}} \right) $$ and $$ \dot{\varepsilon }_{s2} = 2.5\left( {\sigma /G} \right)^{4.38} \exp \left( { - \frac{101582}{RT}} \right) $$ , respectively. The tensile creep mechanism of the solder joints is the effects of lattice diffusion determined by dislocation climbing.

Effect of the Angle Between Sn Grain c-Axis and Electron Flow Direction on Cu-Reinforced Composite Solder Joints Under Current Stressing

With a body-centered tetragonal crystal structure, Sn grains were demonstrated to have highly anisotropic behaviors in various properties. The electromigration behavior of lead-free solder was impacted by the grain orientations. In this paper, the angle between the c-axis and the electron flow direction in composite solder joints (angle θ) was proven to be an important factor during electromigration. The effects of angle θ on the electromigration of composite solder joints were investigated in this paper. Cu particle-reinforced Sn3.5Ag solder joints were stressed under a current density of 104 A/cm2 at room temperature. After 336 h current stressing time, different electromigration phenomena occurred at the two sides of the grain boundary in the composite solder joint which contained two Sn grains with different angle θ. The Sn grains with the larger angle θ had a smaller growth rate of Cu6Sn5. In addition, a composite solder joint with a single Sn grain was set as the contrast and its angle θ was smaller than that of the composite solder joint with two Sn grains. The growth rate of Cu6Sn5 in the composite solder joint with a single grain was faster than that of the composite solder joint with two Sn grains.

Effect of Sn-Ag-Cu on the Improvement of Electromigration Behavior in Sn-58Bi Solder Joint

Reliability issues caused by the formation of a Bi-rich layer at the anode interface usually occurs in the Sn-58Bi eutectic solder joint during electromigration (EM). To improve the EM performance of a Sn-58Bi solder joint, Sn-3.0Ag-0.5Cu solder was introduced into it to produce SnBi-SnAgCu structural or compositional composite joints, and their EM behaviors were investigated with the current density of 1.0 × 104 A/cm2 for different stressing times. The structure of the compositional composite solder joint was obtained by the occurrence of partial or full mixing between Sn-Bi and Sn-Ag-Cu solder with a suitable soldering temperature. In the structural composite joint, melted Sn-Bi was partially mixed with Sn-Ag-Cu solder to produce a Cu/Sn-Bi/Sn-Ag-Cu/Sn-Bi/Cu structure. In the compositional composite joint, full melting and mixing between these two solders occurred to produce a Cu/Sn-Ag-Cu-Bi/Cu structure, in which the solder matrix was a homogeneous structure including Sn, Bi phases, Cu6Sn5 and Ag3Sn IMCs. After current stressing, the EM performance of Sn-Bi solder was obviously improved with the structural or the compositional composite joint. In Sn-58Bi joints, a thick Bi-rich layer was easily produced at the anode interface, and obviously increased with stressing time. However, after current stressing on the structural composite joints, the existence of s Sn-3.0Ag-0.5Cu interlayer between the two Sn-58Bi solders effectively acted as a diffusion barrier and significantly slowed the formation of the Bi-rich layer at the anode side and the IMC thicknesses at the interfaces.

Effects of Grain Orientation on the Electromigration of Cu-Reinforced Composite Solder Joints

Grain orientations are a significant factor under high-density current stressing, but there are few literature reports about the influence of grain orientation on electromigration in composite solder joints. Most research relating to the electromigration behavior of composite solders have been carried out by adding different kinds of reinforced particles in order to relieve the electromigration phenomena, while the impacts of grain orientation on the electromigration have been neglected. In this paper, Sn-3.5Ag composite solder joints reinforced by 2 vol.% Cu were fabricated to investigate the effects of Sn grain orientation on electromigration. The one-dimensional single-grained solder joints were stressed under a constant current density of 104A/cm2 for different times at room temperature. The samples, of which the c-axis of the Sn grains was nearly parallel to the electron flow direction, exhibited serious electromigration-induced phenomena after current stressing for 528 h. However, electromigration was not observed in the samples where the Sn grains had their c-axis perpendicular to the electron flow direction. Therefore, the grain orientations have a great influence on the electromigration behavior in composite solders and Cu atoms moved faster along the c-axis of the Sn grains than along the a- and b-axes during current stressing.

Electromigration reliability for Al2O3-reinforced Cu/Sn–58Bi/Cu composite solder joints

The Sn–58Bi based composite solder was fabricated via mechanical mixing 0.5 wt% Al2O3 particle, and the effect of electromigration (EM) behavior on the microstructure and mechanical properties of the Al2O3-reinforced Cu/Sn–58Bi–0.5Al2O3/Cu lead-free solder joints was investigated under the current density of 0.6 × 104 A/cm2 at room temperature. The results indicated that the EM failure behavior occurred at the cathode side as increasing EM time to 280 h for Cu/Sn–58Bi/Cu and 410 h for Cu/Sn–58Bi–0.5Al2O3/Cu, respectively. A continuous white Bi-rich layer was caused by heavy electron wind flow observed among the bulk solder in the two joints. The remarkable interfacial morphologies change was not found in the 0.5 wt% Al2O3 reinforced joint, and the EM-induced IMC layer growth rate of Cu/Sn–58Bi–0.5Al2O3/Cu was slower than that of the non-composite joint. The mechanical properties, including UTS, shear strength and hardness, of the Cu/Sn–58Bi–0.5Al2O3/Cu solder joint were improved slightly by adding 0.5 wt% Al2O3. Consequently, the EM reliability is enhanced for the Cu/Sn–58Bi–0.5Al2O3/Cu solder joint with adding Al2O3 concentration to 0.5 wt%.

Electromigration Behaviors of Cu Reinforced Sn-3.5Ag Composite Solder Joints

The composite approach, by incorporating small amounts of reinforcement particles in the solder matrix, has proven to be one of the effective ways to improve the reliability of solder joints. The effects of Cu addition on electromigration were investigated in this study by incorporating 2% volume fraction Cu particles into Sn-3.5Ag eutectic solder paste by the in situ process. The one-dimensional solder joints, designed to prevent the current crowding effect, were stressed under a constant current density of 104 A/cm2 at room temperature, and the temperature of the sample could reach 105 ± 5°C due to the Joule heating effect. Doping 2 vol.% Cu was found to retard the electromigration phenomenon effectively. After electric current stressing for 528 h, the growth rate of an interfacial intermetallic compound (IMC) layer at the anode decreased 73% in contrast to that of Sn-3.5Ag solder joints, and the IMC layer at the cathode was almost unchanged. The polarization effect of Cu reinforced composite solder joints was also apparently mitigated. In addition, the surface damage of the composite solder joints was relieved by incorporating 2 vol.% Cu particles. Compared to Sn-3.5Ag solder joints, which had protruded Cu6Sn5 and wrinkles of Sn-solder matrix on the surface, the solder joints with Cu addition had a more even surface.

Effect of Ni and Ni-coated Carbon Nanotubes on the interfacial reaction and growth behavior of Sn58Bi/Cu intermetallic compound layers

The interface reactions between Cu and Sn58Bi solder doped with mass fraction of 0.5 % Ni, 1 % Ni, 0.5 % Ni-CNTs and 1 % Ni-CNTs after reflow and solid-state aging were studied. Results show that the Ni and Ni-CNTs restrain the growth of IMC layer during reflow. After 120 and 240 h aging at 100 °C, the growth of total IMC layer and Cu3Sn layer was inhibited by the addition of Ni and Ni-CNTs. During aging, the thickness of (Cu, Ni)6Sn5 layer in Ni-CNTs-doped solder joint is always thinner than that in Ni-doped solder joint because the Ni-CNTs reduce the CTE of SnBi solder more effectively. The reason for the growth of Cu3Sn with Ni doped less than that with Ni-CNTs is that the stability of (Cu, Ni)6Sn5 gets an improvement as the Ni content increases. Besides, the IMC growth rate of composite solder joints decreases with the increasing Ni and Ni-CNTs content.

Retained ratio of reinforcement in SAC305 composite solder joints: effect of reinforcement type, processing and reflow cycle

Purpose This paper aims to systematically study the effect of reinforcement type, processing methods and reflow cycle on actual retained ratio of foreign reinforcement added in solder joints. Design/methodology/approach Two kinds of composite solders based on SAC305 (wt.%) alloys with reinforcements of 1 wt.% Ni and 1 wt.% TiC nano-particles were produced using powder metallurgy and mechanical blending method. The morphology of prepared composite solder powder and solder pastes was examined; retained ratios of reinforcement (RRoR) added in solder joints after different reflow cycles were analysed quantitatively using an Inductively Coupled Plasma optical system (ICP-OES Varian-720). The existence forms of reinforcement added in solder alloys during different processing stages were studied using scanning electron microscope, X-ray diffractometry and energy dispersive spectrometry. Findings The obtained experimental results indicated that the RRoR in composite solder joints decreased with the increase in the number of reflow cycles, but a loss ratio diminished gradually. It was also found that the RRoR which could react with the solder alloy were higher than that of the one that are unable to react with the solder. In addition, compared with mechanical blending, the RRoRs in the composite solders prepared using power metallurgy were relatively pronounced. Originality/value Present study offer a preliminary understanding on actual content and existence form of reinforcement added in a reflowed solder joint, which would also provide practical implications for choosing reinforcement and adjusting processing parameters in the manufacture of composite solders.

Performance of Sn–3.0Ag–0.5Cu composite solder with TiC reinforcement: Physical properties, solderability and microstructural evolution under isothermal ageing

This paper is focused on the effect of TiC nano-reinforcement that was successfully introduced into a SAC305 lead-free solder alloy with different weight fractions (0, 0.05, 0.1 and 0.2 wt%) through a powder-metallurgy route. Actual retained ratios of TiC reinforcement in composite solder billets and solder joints were quantitatively analysed. The obtained SAC/TiC solders were also studied extensively with regard to their coefficient of thermal expansion (CTE), wettability and thermal properties. In addition, evolution of interfacial intermetallic compounds (IMCs) and corresponding changes in mechanical properties under thermal ageing were investigated. Only about 10%–30% of initial TiC nanoparticles added were found retained in the final composite solder joints. With an appropriate addition amount of TiC nanoparticles, the composite solders exhibited an improvement in their wettability. A negligible change in their melting point and a widened melting range were found in composite solders containing TiC reinforcement. Also, the CTE of composite solder alloys was effectively decreased when compared with the plain SAC solder alloy. In addition, a growth of interfacial IMCs in composite solder joints was notably suppressed under isothermal ageing condition, while their corresponding mechanical properties of composite solder joints significantly outperformed those of non-reinforced solder joints throughout the ageing period.

An investigation on the ZnO retained ratio, microstructural evolution, and mechanical properties of ZnO doped Sn3.0Ag0.5Cu composite solder joints

In this study, ZnO nanoparticles with different weight fractions (0.1, 0.25, 0.5 and 1 wt%) were successfully incorporated into Sn3.0Ag0.5Cu (SAC305) solder through powder metallurgy method. The retained ratios of ZnO reinforcements were measured, and then their effects on the thermal behaviors, microstructural evolution and mechanical properties of composite solders were systematically studied. The element content analysis revealed that only about 12 % of the initially doped ZnO nanoparticles were retained in the final solder joints. With an increase in the amount of reinforcements, the undercooling of composite solders was decreased while the melting temperature was negligibly altered. Refined β-Sn grains were obtained in the composite solder matrix after addition of ZnO nanoparticles. Moreover, compared to the plain solder joints, the composite solder joints exhibited a lower growth velocity of interfacial intermetallic compounds during isothermal aging. A 17.9 % improvement in microhardness and a 10.1 % enhancement in shear strength were also achieved for composite solder joints after 1 wt% ZnO addition. These promotions are all contributed by the presence of ZnO nanoparticles and refined microstructure in solder matrix.

Improvement of Sn-0.7Cu Lead Free Solder Joints on Shear Strength with Addition of Titanium Oxide (TiO<sub>2</sub>) Particles

In this paper, Sn-0.7Cu composite containing weight percentage of 1.0 wt. % of titanium oxide (TiO2) particles were successfully fabricated by using the powder metallurgy (PM) route assisted hybrid microwave sintering. This research investigated the effect s of TiO2 particles addition on the interfacial reactions formed between Sn-0.7Cu solder/substrate and shear strength of a Sn-0.7Cu solder alloy. With the increasing of TiO2 particles, Sn-0.7Cu-TiO2 composite solder showed decreasing in thickness value and shear strength was increased. This signified that the presence of TiO2 particles effect on the thickness of Cu6Sn5 IMC layer at the interface and mechanical properties Sn-0.7Cu composite solder joint.

An investigation of microstructure and properties of Sn3.0Ag0.5Cu-XAl2O3 composite solder

Purpose The purpose of this paper is to investigate microstructure and properties of Sn3.0Ag0.5Cu-XAl2O3 composite solder which were prepared through powder metallurgy route. Design/methodology/approach Sn3.0Ag0.5Cu (SAC305)-XAl2O3 (X = 0.2, 0.4, 0.6, 0.8 Wt. %) composite solders were prepared through the powder metallurgy route. The morphology of composite solder powders which consists of Al2O3 particles and SAC solder powders after ball milling was observed. The retained ratio of Al2O3 nanoparticles in composite solder billets and solder joints were also quantitatively measured. Furthermore, the as-prepared composite solder alloys were studied extensively with regard to their microstructures, thermal property, wettability and mechanical properties. Findings After ball milling, the Al2O3 nanoparticles added were observed embedded into the surface of SAC solder powders. Only about 5-10 per cent of the initial Al2O3 nanoparticles added were detected in the composite solder joints after reflow. In addition, finer ß-Sn grains were achieved with addition of Al2O3 nanoparticles; the Al2O3 nanoparticles were found retained in the composite solder matrix. Besides, negligible changes in melting temperature and the considerably reduced undercooling were obtained in composite solder alloys. Wettability was improved by appropriate addition of Al2O3 nanoparticles. Microhardness and shear strength of composite solders were both improved after Al2O3 nanoparticles addition. Originality/value This paper indicated that powder metallurgy route offered a feasible approach to produce nanoparticle reinforced composite solder. In addition, the quantitative analysis of the actual retained ratio of the Al2O3 nanoparticles in solder joints provided practical implications for the manufacture of composite solders.

Microstructure, mechanical and electrical performances of zirconia nanoparticles-doped tin-silver-copper solder alloys

The present study investigates the influence of ZrO2 nanoparticles addition on microstructure, material properties i.e., elastic moduli, creep behavior, hardness, shear strength and electrical resistivity of Sn–3.0Ag–0.5Cu (wt%)-based interconnected alloys. From microstructure observation it was revealed that in the plain Sn–Ag–Cu bulk solder a needle-shaped Ag3Sn and irregular shaped Cu6Sn5 IMC particles were formed in the elongated-like β-Sn grains. However, in the composite solder alloy, very fine needle-shaped Ag3Sn and irregular shaped Cu6Sn5 IMC particles were formed in equiaxed β-Sn grain matrix. Further, material properties like elastic moduli, hardness, creep behavior and electrical resistivity of Sn–Ag–Cu solder were improved significantly after adding the ZrO2 nanoparticle. Sn–Ag–Cu-based composite solder joints were prepared on Au/Ni-metallized Cu pad ball grid array (BGA) substrate and investigated their performance after exposing a thermal shock chamber at –40 to 90 °C. From this test, it was confirmed that the degradation behavior of plain solder joints was much faster as compared to the composite solder joints and also detected some micro-cracks at the interface and solder matrix. Further, the shear strength of plain solder joints was decreased significantly as compared to the composite solder joints.

Rapid microstructure evolution of structural composite solder joints induced by low-density current stressing

The microstructure evolution of solder matrix and interfacial intermetallic compounds (IMCs) of Cu/Sn37Pb/Sn3.0Ag0.5Cu/Sn37P/Cu structural composite joints were investigated under low-density current stressing of 2.0×103A/cm2 at 100°C. Cu flux diffusion induced by electro-migration was delayed by Ag3Sn particles in eutectic phase of Sn3.0Ag0.5Cu solder, by which Cu6Sn5 particles could not reach the interfacial IMC at anode side, and then the growth of interfacial IMC or regular polarity effect at node was inhibited. Coarsened Cu6Sn5 particles were accumulated at the fusion zone between SnAgCu and SnPb close to anode side. Micro-cracks were found at cathode side after current stressing for as short as 100h, and increased with current stressing time until the failure of solder joint.

Improved microstructure and mechanical properties for Sn58Bi0.7Zn solder joint by addition of graphene nanosheets

The effects of graphene nanosheets (GNSs) on the microstructure and mechanical properties of Sn58Bi0.7Zn solder joint were investigated. Experimental results and finite element (FE) simulations showed that the best mechanical properties improvement came from the 0.076 wt.% GNS-doped Sn58Bi0.7Zn sample. It exhibited the highest creep resistant in all the as-prepared solder joints, and the average interphase spacing in solders was reduced by 32.52%, the stress exponent was increased by 13.70%. For the thermal aging samples, the ultimate tensile strength (UTS) of the solder joint was also increased by 2.04%. Moreover, the 0.114 wt.% GNS-doping significantly reduced the time exponent from 0.403 to 0.362 and decreased the thickness of total IMC layers by 56.31%. Based on the theories related to material performance and the restacking behavior of GNSs, the strengthening mechanism of GNSs in composite solder joint was analyzed and an optimum concentration of GNSs in Sn58Bi0.7Zn solder alloy was proposed.

Improving shear strength of Sn-3.0Ag-0.5Cu/Cu joints and suppressing intermetallic compounds layer growth by adding graphene nanosheets

This study investigated the effects of adding 0.1wt% of graphene nanosheets (GNSs) into Sn-3.0Ag-0.5Cu solder matrix on the growth of intermetallic compounds (IMC) layer with Cu substrates during isothermal aging at temperatures of 100, 125, 150 and 175°C for up to 7 days. The results indicated that the GNSs could provide huge diffusion barrier for the diffusion of Sn and Cu atoms in solder matrix, and the activation energy for IMC layer growth was calculated as 46.20 and 59.72kJ/mol for Sn-3.0Ag-0.5Cu solder and Sn-3.0Ag-0.5Cu-0.1GNSs composite solder, respectively. Compared with Sn-3.0Ag-0.5Cu solder joints, the IMC layer morphology transformation from scallop-type to layer-type and the IMC layer growth for composite solder joints were suppressed. After aging 7 days at 175°C, the shear strength of composite solder joints, whose IMC layer was comparatively thin, was 30% higher than that of Sn-3.0Ag-0.5Cu solder joints.

Interfacial microstructure, wettability and material properties of nickel (Ni) nanoparticle doped tin–bismuth–silver (Sn–Bi–Ag) solder on copper (Cu) substrate

This paper investigates the influence of adding nickel (Ni) nanoparticles on the microstructure, wettability and material properties of Sn–35Bi–1Ag (wt%) based solders. Material properties such as elastic and shear moduli, stress/strain behavior and electrical resistivity of bulk composite solder were improved significantly in comparison to the corresponding properties of reference solder alloy. The elastic and shear moduli of composite solder increased about 16.8 and 19 % respectively, while the electrical resistivity at room temperature was improved from 23.7 to 25.1 μΩ cm. On the other hand, in solder joint on Cu substrate, an island-shaped Cu6Sn5 IMC layer was clearly observed at interface for the plain solder/substrate system. Further a prolong reaction, a very thin Cu3Sn IMC layer was also formed at the substrate surface. However, in the case of the composite solder/substrate system, a scallop-shaped ternary (Cu, Ni)–Sn IMC layer was observed to be adhered at the interface without formation of Cu3Sn IMC layer for the composite solder/substrate system. Moreover, the composite solder/substrate system hindered the growth behavior of IMC layer as well as refined the microstructure which can influence life-span of electronic devices. Additionally, the overall micro-hardness values of composite solder joints exhibited higher values as compare to the plain solder joints due to the second phase strengthening mechanism.

Effect of Graphene Oxide Nano-Sheets (GONSs) on thermal, microstructure and stress–strain characteristics of Sn-5 wt% Sb-1 wt% Ag solder alloy

Regarding to the development of Sn–Sb–Ag (SSA) lead-free (plain) solders for advance electronic components, the effect of 0.2 wt% Graphene Oxide Nano-Sheets (GONSs) on thermal, microstructure and stress–strain characteristics of Sn-5 wt% Sb-1.0 wt% Ag (SSA510) lead-free solder alloy is investigated. Experimental results showed that addition of GONSs to SSA510 (composite) solder alloy slightly increased the melting temperature. Microstructure investigations revealed that addition of GONSs to SSA510 solder inhibited the growth of the β-Sn grains, SnSb and Ag3Sn intermetallic compounds which subsequently reinforced the strength and increased the resistance to deformation of the SSA510 composite solder. Increasing strain rate resulted in increasing the tensile strength while increasing the testing temperature decreased the strength of both the plain and composite solder alloys. Good and excellent higher values of strength accompanied with high ductility were attained in the composite solder at all test conditions compared with those in the SSA510 plain solder. Thereby, addition of GONSs to the SSA solder makes composite solder joints to be more efficient for industrial applications that can make composite solder endure higher stresses.

Microstructures and properties of new Sn–Ag–Cu lead-free solder reinforced with Ni-coated graphene nanosheets

This paper deals with microstructures and properties of SAC305 lead-free solder reinforced with graphene nanosheets (GNS) decorated with Ni nanoparticles (Ni-GNS). These Ni-coated GNS nanosheets were synthesized by an in-situ chemical reduction method. After morphological and chemical characterization, Ni-GNS were successfully integrated into SAC305 lead-free solder alloy with different weight fractions (0, 0.05, 0.1 and 0.2 wt.%) through a powder metallurgy route. The obtained composite solders were then studied extensively with regard to their microstructures, wettability, thermal, electrical and mechanical properties. After addition of Ni-GNSs, cauliflower-like (Cu,Ni)6 Sn5 intermetallic compounds (IMCs) were formed at the interface between composite solder joint and copper substrate. Additionally, blocky Ni–Sn–Cu IMC/GNS hybrids were also observed homogenously distributed in the composite solder matrices. Composite solder alloys incorporating Ni-decorated GNSs nanosheets showed slightly reduced electrical resistivity compared to the unreinforced SAC305 solder alloy. With an increase in the amount of Ni-GNS, the composite solders showed an improvement in wettability with an insignificant change in their melting temperature. Mechanical tests demonstrated that addition of 0.2 wt.% Ni-GNS would result in 19.7% and 16.9% improvements in microhardness and shear strength, respectively, in comparison to the unreinforced solders. Finally, the added Ni-GNS reinforcements in the solder matrix were assessed with energy-dispersive X-ray spectroscopy, scanning electron microscopy and Raman spectroscopy.

Effects of graphene nanosheets on interfacial reaction of Sn–Ag–Cu solder joints

In this work, varying amount of graphene nanosheets (GNSs) were introduced as reinforcements into Sn–Ag–Cu (SAC) solder to get composite solders. Then, the formation and growth kinetics of the intermetallic compounds (IMC) were investigated during the liquid–solid reactions and solid-state aging. Experimental results demonstrated that the morphologies of the interfacial IMC were transformed from scalloped to platelike after liquid–solid reactions and solid-state aging. The IMC thickness of composite solder joints was thinner than that of the unreinforced solder joints. The calculations revealed that the growth rate constant of composite solder was lower than that of bulk SAC solder. It's worth to mention that the composite solder joints exhibited lower diffusion coefficients (ranging from 0.6 × 10−12 m2/s to 1.07 × 10−12 m2/s) than that of the SAC solder joints (1.81 × 10−12 m2/s) after liquid–solid reactions and the composite solder joints also exhibited lower diffusion coefficients (ranging from 1.42 × 10−12 m2/s to 1.78 × 10−12 m2/s), as compared to that of the monolithic SAC solder joint (2.46 × 10−12 m2/s) after aging studies. It indicates that the addition of GNSs can effectively suppress the growth of the overall IMC layers, which can also hinder the IMC's growth and enhance solder joints' reliability.