Reflow Process Research Articles

Soldering Defects on Immersion Tin and the Impact of the Tin-Oxide Layer

Immersion tin is a final finish highly accepted in the automotive industry and finds increasingly application in the package substrate industry. As due to the immersion reaction the plating thickness of tin is limited, there are concerns that due to the formation of the intermetallic phase during the reflow process, the solderability of the tin layer might be affected. During the assembly process and the formation of the intermetallic phase the free tin is consumed and only islands of free tin remain after the second reflow cycle. Additionally, an oxide layer is formed, and the homogeneity and thickness of the oxide layer is impacted by the reflow conditions and the overall process cleanliness. The interaction of intermetallic phase formation, the amount of remaining free tin and the tin oxide layer will define the soldering performance of the tin layer and the risk of the occurrence of soldering defects. In this paper different failure modes and connected failure mechanisms will be explained. The tin oxide layer is identified to play a crucial role in this interaction and factors are investigated, which impact the oxide layer formation and homogeneity. Various methods are presented to determine the oxide layer thickness and different approaches are studied to modify it. Results are presented that show that with a dedicated solution to modify the oxide layer the risk for solderability defects on immersion tin can be reduced.

Soldering reflow process optimization based on simulation

Soldering reflow process optimization based on simulation

Finite Element Analysis and Multi-Objective Optimization of Solder Joint Temperature Difference and Cooling Stress During PCBA Reflow Process

Finite Element Analysis and Multi-Objective Optimization of Solder Joint Temperature Difference and Cooling Stress During PCBA Reflow Process

Mitigating solder voids in quad flat no-lead components: A vacuum reflow approach

As global demand for high-efficiency automotive electronics grows, enhanced heat dissipation and reliability are essential to meet the energy demands of high-computation applications. Void formation in solder joints poses significant challenges, reducing thermal conductivity and joint strength. In response, this study optimizes the vacuum reflow process parameters and stencil aperture design to mitigate voids in Quad Flat No-Lead (QFN) packages, which are widely adopted for their heat dissipation capabilities.Using the Taguchi method, we determined the optimal stencil aperture shapes and reflow conditions for two thermal pad sizes in QFNs. For the large thermal pad (5.24 mm × 4.5 mm), the optimal parameters included a fence-type aperture covering 85 % of the pad area, vacuum pressure of 50 mbar, 10-s vacuum duration, and a fully open vacuum valve. For the small thermal pad (1.6 mm × 4.2 mm), optimal parameters were a fully covered aperture at 85 % of the pad area, 50 mbar vacuum pressure, 5-s vacuum duration, and fully open valve. Results demonstrated that these optimized conditions effectively reduced void ratios to 0.7 % for the large pad and 0.5 % for the small pad, meeting industry standards for automotive applications.

Fabrication and Reflow of Indium Bumps for Active-Matrix Micro-LED Display of 3175 PPI

Indium is acknowledged as a preferred material for micro-light-emitting diodes (micro-LEDs) flip-chip bonding within the industry, due to its favorable economic characteristics and low melting point. However, indium bumps fabricated via photolithography and thermal evaporation often exhibit irregular shapes and varying heights, and they readily oxidize in air to form a tightly adhered oxide layer (In2O3), leading to flip-chip bonding failures and blind pixels. The reflow process can not only remove the oxide layer but also enhance bump uniformity. Nevertheless, literature on indium reflow predominantly focuses on planar substrates, with limited studies on high-resolution micro-LED chips for flip-chip bonding. This paper details the preparation of micro-LED chips with a pixel density (pixel per inch, PPI) of 3175. An indium bump array with a diameter of approximately 5 μm was prepared on the micro-LED chips using thermal evaporation technology. The influence of reflow time and temperature on indium bumps was thoroughly investigated by the formic acid reflow process, revealing that under the conditions of 270 °C and 180 s, the indium bumps with a narrower size distribution could be reflowed into spherical shapes on the micro-LED structure. Furthermore, an inversely proportional relationship was discovered between mesa/metal layer height and indium bump growth, which influenced the reflow effect. Ultimately, micro-LED chips were integrated with si complementary metal–oxide–semiconductor (CMOS) driver chips through flip-chip bonding technology, resulting in the successful functioning of the devices.

SnPbInBiSb high-entropy solder joints with inhibited interfacial IMC growth and high shear strength

The rapid advancements in microelectronic devices towards miniaturization and multifunctionality have led to an increasing demand for solder joints that exhibit enhanced mechanical properties and reliability. This study focuses on investigating the high-shear strength of SnPbInBiSb/Cu high-entropy solder joints. The analysis encompasses the microstructure evolution, interfacial reactions, and shear behavior of these solder joints after reflowing at 180 °C. The study reveals the formation of very thin intermetallic compound (IMC) layers, specifically Cu6Sn5 and Cu3Sn, at the SnPbInBiSb/Cu interface with an average thickness of about 1.04 μm following a 10min reflow. Transmission electron microscopy (TEM) analysis illustrates the presence of nanoscale precipitates of InSn3 or Sn3Sb phases dispersed within the Cu6Sn5 IMC. The high mixing entropy of the SnPbInBiSb solder contributes to the suppression of the interfacial IMC growth rate during the reflow process. Notably, the shear strength and fracture behavior of the SnPbInBiSb high-entropy solder joints are significantly influenced by the thickness of the interfacial IMC. In particular, solder joints reflowed at 180 °C for 10 min exhibit a high shear strength of 102.4 MPa with a ductile fracture mode.

Quaternary low melting point Sn-Bi-in-xGa solder with improved mechanical performance for advanced electronic packaging

Managing thermal stress is important for ensuring the yield of chip integration and packaging. The development of appropriate low melting point solders has become the key to mitigating thermal stress during the assembling, which aligns well with the demands of next-generation interconnection technologies. In this study, we developed a quaternary low melting point solder based on Sn-Bi-In-xGa (x = 0, 0.1, 0.3, 0.5, 1.0, 1.5, wt%). The addition of Ga not only lowers the solder's melting point but also enhances its wettability. We also studied how the increase of Ga in the solder alloy influences the microstructure and shear test failure mechanism during aging. Upon subjecting solder joints to a 10-min reflow process at 100 °C with Cu substrates, two distinct types of intermetallic compound (IMC) were observed: Cu6(Sn, In)5 when Ga content was ≤0.1 wt% and γ3-Cu9Ga4 when Ga content was ≥0.3 wt%. The stable property of γ3-Cu9Ga4 IMC ensures the mechanical stability of the joints during aging. Therefore, the addition of an appropriate amount of Ga (0.3 wt%) can improve the mechanical performance of solder joints during aging. These findings offer valuable insights for the development of high-performance low-melting-point solders in microelectronics, shedding light on the mechanisms underlying the influence of Ga content on solder microstructures and mechanical reliability during thermal aging.

Microstructural Evolution of Intermetallic Compound Between SN100C Solder and ENIMAG Substrate During Isothermal Ageing

SN100C alloy emerges as a promising candidate when introducing lead-free solder alternativesdue to its mechanical properties and solderability. The study aims to explore interfacial reactions between SN100C solder and ENIMAG surface finish. Methods involve preparingENIMAG substrates, solder paste application, and reflow processes following JEDEC standards. Isothermal ageing treatments were conducted, and interfacial reactions were characterized using top surface and cross-section analyses via Optical Microscope (OM), Scanning Electron Microscope (SEM), and Energy Dispersive X-ray (EDX). Post-reflow, distinct IMC layers formed at the SN100C/ENIMAG solder joint's interface, evolving with ageing. Further analysis via cross-section confirms the initial formation of (Ni, Cu)3Sn4 layer followed by (Cu, Ni)6Sn5, each exhibiting varying appearance and thicknesses. Isothermal ageing increases IMC thickness, which is particularly influenced by Cu diffusion and exposure to high temperatures, and itfacilitates the growth rate of IMCs.

Contact Hole Shrinkage: Simulation Study of Resist Flow Process and Its Application to Block Copolymers.

For vertical interconnect access (VIA) in three-dimensional (3D) structure chips, including those with high bandwidth memory (HBM), shrinking contact holes (C/Hs) using the resist flow process (RFP) represents the most promising technology for low-k1 (where CD=k1λ/NA,CD is the critical dimension, λ is wavelength, and NA is the numerical aperture). This method offers a way to reduce dimensions without additional complex process steps and is independent of optical technologies. However, most empirical models are heuristic methods and use linear regression to predict the critical dimension of the reflowed structure but do not account for intermediate shapes. In this research, the resist flow process (RFP) was modeled using the evolution method, the finite-element method, machine learning, and deep learning under various reflow conditions to imitate experimental results. Deep learning and machine learning have proven to be useful for physical optimization problems without analytical solutions, particularly for regression and classification tasks. In this application, the self-assembly of cylinder-forming block copolymers (BCPs), confined in prepatterns of the resist reflow process (RFP) to produce small contact hole (C/H) dimensions, was described using the self-consistent field theory (SCFT). This research paves the way for the shrink modeling of the enhanced resist reflow process (RFP) for random contact holes (C/Hs) and the production of smaller contact holes.

Application of Cu Reflow Process on Ru Liner for Advanced Nanoscale Interconnects

Abstract A novel physical vapor deposition (PVD) Cu reflow process with chemical vapor deposition (CVD) Ru liner was optimized for 10 nm generation interconnects and beyond. For these and future device generations, void-free Cu interconnects are a key requirement, and the PVD Cu reflow process improvements reported here provide significant advancement in enabling excellent Cu reflow performance. The Ru liner exhibited much better Cu reflow performance than a Ta liner by effectively suppressing Cu agglomeration during the Cu reflow process, likely due to a better adhesion to Cu. Reflow temperature and Ru thickness (continuity) are critical parameters for achieving good Cu reflow performance, and this optimized Cu reflow process with Ru liner did not show line top voids or sidewall voids, which are the two major void types often observed at this dimension when pursuing Cu fill with the conventional Cu seed and Cu plating fill scheme. Furthermore, this novel Cu reflow process exhibited an electromigration (EM) performance enhancement due to having better Cu fill quality.

Bonding Properties of Package-on-Package Stack Interconnection Using by 150 ㎛ Height Copper Posts

In this study, we used copper (Cu) posts, plated to a height of 150 μm, as interconnections to form electrodes between different package layers. The upper layer consisted of a chip-scale package (CSP), while the lower layer was made up of a flip chip-chip scale package (FCCSP). We plated a Cu post on the side of FCCSP substrate, and produced the FCCSP package by thermo-compression (TC) bonding with copper pillar solder bumps on the center of substrate. The surface of the bottom electrode for the upper CSP received a surface finish of electroless nickel, electroless palladium, and immersion gold (ENEPIG). The bonding surface of the lower FCCSP was the bare Cu surface of the epoxy-molded Cu post. The PoP joining process used a vacuum reflow process with solder paste and solder balls. To understand the package joint's characteristics, we measured voids and shear strength, and analyzed the cross-sectional microstructure. The temperature profile used in the PoP joining process demonstrated optimal joint characteristics with a joint void content of 2.3% and a joint strength of approximately 44 MPa when formic acid was utilized and the activation preheating time was extended. Cross-sectional warpage analysis of the PoP package revealed a minimal difference of approximately 31 μm between the center and the ends. This study successfully developed a stacked package with a PoP structure using Cu Post, and the bonding process was optimized to minimize warpage in the PoP package.

Exploring joining techniques for diamond chips on metallized substrates: Micro- and nano-scale mechanical testing approach

This paper aims to comprehensively evaluate the shear strength of various junctions between diamond chips and double copper bonded ceramic substrates. The study involves several stages, beginning with the deposition of Ti/Ni/Ag metallization system on diamond chips using a chemical vapor deposition (CVD) process. These metallization systems are selected to determine their suitability as ohmic contacts on diamond. In parallel, Ni/Au and Ni/Ag layers are electroplated onto the thick copper metallization of the ceramic substrate. Following these depositions, junctions are created for both Cu/Cu and C/Cu assemblies using different techniques: reflow process for AuGe solder joints, reflow-diffusion process for Ag-In joints, and a thermomechanical process for Ag nanoparticle joints. To assess the effectiveness of these techniques, the shear strength of the junctions is measured using a micro-shear test, which is analogous to a classical micro-scratching test. Additionally, the mechanical behaviors of the layers adjacent to the assemblies are analyzed through nano-indentation tests. Finally, the fracture surfaces are examined using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) spectrometry to identify the microstructure and damage modes. The work described in the paper exhibits several innovative aspects. It introduces the novel combination of Ti/Ni/Ag metallization system on diamond chips, evaluated for its suitability as ohmic contacts, potentially leading to improved electrical and thermal performance in diamond substrate applications. The study employs diverse junction creation techniques, such as reflow for AuGe solder joints, reflow-diffusion for Ag-In joints, and a thermomechanical process for Ag nanoparticle joints, allowing for a thorough comparison and identification of the most effective method for different scenarios. We have also introduced an integrated testing methodology, which combines micro-shear tests and nano-indentation tests and provides a robust framework for assessing both the shear strength and mechanical properties of the junctions and adjacent layers, enhancing the reliability and depth of the evaluation. The specific focus on metallization system and junctions suitable for diamond, known for its exceptional thermal and electrical properties, positions this work as highly relevant for advanced electronic and thermal management applications.

Photothermal effects on low-temperature hybrid solder joints and its superior drop reliability

Hybrid solder joints incorporating the Sn-3.0Ag-0.5Cu/Sn–58Bi structure have been studied to tackle challenges such as warpage, thermal degradation, and excessive intermetallic compound (IMC) growth in heterogeneous integrated packages. However, the presence of Bi diminishes drop impact reliability, and conventional reflow processes aimed at increasing the Bi mixing ratio exacerbate IMC growth. This study investigates the feasibility of intense pulsed light (IPL) soldering for hybrid solder joints on electroless nickel immersion gold (ENIG) and (electroless nickel electroless palladium immersion gold (ENEPIG) PCB substrates, with the goal of advancing reliable and sustainable electronic packaging technology. Microstructural evolution and drop impact reliability of IPL-soldered joints were compared with those of conventionally reflow-soldered joints. Specifically, IPL soldering exhibited approximately sixfold higher drop impact reliability in ENIG and threefold in ENEPIG compared to reflow soldering under the lowest temperature conditions. This underscores IPL's effectiveness in suppressing interfacial reactions, thereby promoting crack propagation in the SnBi phases. Furthermore, under optimized IPL conditions on the ENEPIG substrate, drop reliability was approximately threefold higher than that achieved under the lowest temperature conditions, despite lower power consumption of 13.36 kWh. These findings demonstrate the potential feasibility of IPL soldering as a reliable and sustainable technology for electronic packages.

Enhanced Mechanical Properties with Ag Addition in Electroplated Ni-Sn Solder Joints: Sub-10 Micron Bond Thickness

Keywords: Micro-bump; Microstructure; Intermetallic compounds; Mechanical properties; thermocompression bondingThe advancement of electronic devices has garnered more extensive attention towards three-dimensional integrated circuit (3D-IC) technology due to microbump size reduction and increased power density. Microbumps play an important role in driving the development of this technology, especially in 3D chip-stacking involving multiple reflow processes. The reduction in microbump height spotlights the presence of intermetallic compounds (IMCs). In comparison to traditional ball grid array (BGA) solder joints, microbumps with smaller solder volumes exhibit a predominant fraction of IMCs at solder joints, especially with microbump dimensions potentially shrinking to less than 10 micrometers.The interface reaction within confined spaces has become a critical concern. Mechanical properties will be dominated by IMC properties rather than solder characteristics. In conventional Cu/Sn/Cu solder joints, grain coarsening and prolonged reflowing times, which result in IMC collisions from opposing substrates, forming columnar grains with a uniform orientation, make the solder joint less reliable. Furthermore, the Cu3Sn layer in Cu/Sn/Cu microbumps presents another challenges, indicating the formation of Kirkendall voids, increasing the risk of brittle interface fractures.This study investigates the mechanical reliability and microstructure of two sub-10um sandwiched structures: Cu/Ni/Sn/Ni/Cu and Cu/Ni/Sn-3.5Ag/Ni/Cu. In the 3D-IC manufacturing process, solder joints will experience multiple reflow processing. Different reflow heat treatment process to achieve different fractions of Ni3Sn4 IMCs were performed on both sandwiched structure. Despite the formation of internal voids due to volume shrinkage in Ni/Sn solder joints, the addition of silver in the solder, forming Ag3Sn, effectively fills these voids. The long-time reflowed sample showed outstanding mechanical properties via the addition of silver in solder. In this study, the influence of silver addition on the microstructure and mechanical properties of the overall joints under identical reflow conditions, the fracture path observation after shear test were investigated. The growth mechanism of Ag3Sn and its distribution in the solder would be further explored and addressed. Figure 1

Diffusion Barrier Performance of Ni-W Layer at Sn/Cu Interfacial Reaction.

As the integration of chips in 3D integrated circuits (ICs) increases and the size of micro-bumps reduces, issues with the reliability of service due to electromigration and thermomigration are becoming more prevalent. In the practical application of solder joints, an increase in the grain size of intermetallic compounds (IMCs) has been observed during the reflow process. This phenomenon results in an increased thickness of the IMC layer, accompanied by a proportional increase in the volume of the IMC layer within the joint. The brittle nature of IMC renders it susceptible to excessive growth in small-sized joints, which has the potential to negatively impact the reliability of the welded joint. It is therefore of the utmost importance to regulate the formation and growth of IMCs. The following paper presents the electrodeposition of a Ni-W layer on a Cu substrate, forming a barrier layer. Subsequently, the barrier properties between the Sn/Cu reactive couples were subjected to a comprehensive and systematic investigation. The study indicates that the Ni-W layer has the capacity to impede the diffusion of Sn atoms into Cu. Furthermore, the Ni-W layer is a viable diffusion barrier at the Sn/Cu interface. The "bright layer" Ni2WSn4 can be observed in all Ni-W coatings during the soldering reflow process, and its growth was almost linear. The structure of the Ni-W layer is such that it reduces the barrier properties that would otherwise be inherent to it. This is due to the "bright layer" Ni2WSn4 that covers the original Ni-W barrier layer. At a temperature of 300 °C for a duration of 600 s, the Ni-W barrier layer loses its blocking function. Once the "bright layer" Ni2WSn4 has completely covered the original Ni-W barrier layer, the diffusion activation energy for Sn diffusion into the Cu substrate side will be significantly reduced, particularly in areas where the distortion energy is concentrated due to electroplating tension. Both the "bright layer" Ni2WSn4 and Sn will grow rapidly, with the formation of Cu-Sn intermetallic compounds (IMCs). At temperatures of 250 °C, the growth of Ni3Sn4-based IMCs is controlled by grain boundaries. Conversely, the growth of the Ni2WSn4 layer (consumption of Ni-W layer) is influenced by a combination of grain boundary diffusion and bulk diffusion. At temperatures of 275 °C and 300 °C, the growth of Ni3Sn4-based IMCs and the Ni2WSn4 layer (consumption of Ni-W layer) are both controlled by grain boundaries. The findings of this study can inform the theoretical design of solder joints with barrier layers as well as the selection of Ni-W diffusion barrier layers for use in different soldering processes. This can, in turn, enhance the reliability of microelectronic devices, offering significant theoretical and practical value.

Stable SnAgCu solder joints reinforced by nickel-coated carbon fiber for electronic packaging

Today’s 3D electronic packaging is characterized by smaller size and higher functional density, which generally require multiple reflow cycles. However, due to the Ostwald ripening process of the interfacial intermetallic compound (IMC), the solder joint’s strength would decrease as the number of reflow cycles increases. To address this, we developed a novel composite solder by incorporating nickel-coated carbon fiber (Ni@CF) into the Sn–3.0Ag–0.5Cu (SAC305) solder connection. The study showed that Ni@CF effectively enhanced the stability and reliability of solder joints during multiple reflow processes. Compared with Ni@CF-free equivalents, Ni@CFs promoted the nucleation of interfacial IMC during the solid–liquid reaction and inhibited Ostwald ripening, leading to a refinement of the interfacial IMC grains. As a result, the interface was strengthened, and the shift of shear fracture to the brittle interface seen in the SAC305 solder joint with multiple reflows did not occur in the composite solder joint. Furthermore, carbon fiber strengthened the solder matrix through the load transfer and shear-off mechanisms, depending on its inclination angle with the shear plane. Consequently, the Ni@CFs-reinforced solder joints maintained a shear strength of over 42 MPa throughout ten reflow cycles, while the pristine SAC305 solder joint exhibited decreased shear strength to 33 MPa. This study provides new insights into composite solder joints’ stability and reinforcement characteristics when subjected to multiple reflows.

Scaling up multispectral color filters with binary lithography and reflow (BLR).

Efforts to increase the number of filters are driven by the demand for miniaturized spectrometers and multispectral imaging. However, processes that rely on sequential fabrication of each filter are cost ineffective. Herein, we introduce an approach to produce at least 16 distinct filters based on a single low-resolution lithographic step with minimum feature size of 0.6 μm. Distinct from grayscale lithography, we employ standard binary lithography but achieve height variations in polymeric resist through a post-development reflow process. The resulting transparent polymeric films were incorporated in Fabry-Perot cavity structures with cavity thickness ranging from 90 to 230 nm to produce transmittance across the visible spectrum. This binary lithography and reflow (BLR) process demonstrates control of the dielectric layer thickness down to ∼15 nm. This new process provides a cost-effective alternative to traditional techniques in fabricating microscopic transmission filters, and other applications where precise thickness variation across the substrate is required.

Theoretical prediction of soft-forming micro-hemispherical shells from fused silica substrates in reclining mold

A reclining mold can support the soft forming of fused silica substrates into micro-hemispherical shells with the same height, which makes the processing of micro-hemispherical shells attractive. Currently, it is difficult to determine the optimal process parameters for machining micro-hemispherical shells, and several iterations of experiments are required. This process wastes large amounts of substrate material, experimental consumables, and machining time, and increases the cost of the experiments. In this paper, we report a reflow process for soft-forming micro-hemispherical shells from fused silica substrates supported by a reclining mold. The shapes of the shells formed from the fused silica substrates in reclining and non-reclining molds were analysed by building a two-dimensional model. Moreover, we predicted the effects of varying the process parameters on the shell-forming time and geometrical parameters, as well as the stresses and deformations of the shells after cooling. The effect of the eccentricity of the central support column of the mold on the symmetry of micro-hemispherical shells was also investigated, and the influence of the mold and substrate heating inhomogeneity on micro-hemispherical shell formation was analysed. Additionally, the heat uniformity of the substrate in the rotating state was examined. Finally, we investigated the temperature field and thickness distribution during the shell-forming process through 3D modelling to verify the 2D modelling results. Analysing and predicting the parameters helps to reduce the number of trial-and-error processes in experiments, and we expect this work to provide a theoretical parametric basis for micro-hemispherical shell machining.

Effect of solder void on mechanical and thermal properties of flip-chip light-emitting diode: Statistical analysis based on finite element modeling

With the increasing demand for highly efficient lighting in the automotive industry, flip-chip light-emitting diodes (LEDs) have become widely used for both interior and exterior lighting. Solder, serving as a crucial interconnecting material, often develops voids during the reflow process, compromising the integrity and reliability of the connections. Thus, understanding the impact of these voids on the mechanical and thermal properties of the product is vital for improving reliability accuracy. This work employs computational methods alongside experimental approaches to address the challenges of replicating solder voids and controlling the solder void fraction. A comprehensive study investigates the effects of solder voids on shearing properties and thermal conductance. Random voids were introduced into the solder pads of an LED assembly within a finite element model (FEM), leading to predictions of maximum shear stress and LED junction temperature. The findings correlate well with the experimental data, validating the FEM's applicability. Furthermore, a statistical analysis was conducted to explore the relationship between solder void fraction, position, and size, aiming to provide objective guidelines for analyzing soldered assembly tomography in reliability assessments.

Microstructural Evolution and Phase Transformation on Sn–Ag Solder Alloys under High‐Temperature Conditions Focusing on Ag3Sn Phase

This study investigates the microstructural and phase transformations in Sn–Ag solder alloys under high‐temperature conditions, utilizing X‐ray diffraction, scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) analyses. Analytical techniques are employed pre‐ and postcontrolled thermal cycling from 30 to 180 °C, aimed at emulating solder reflow processes. The analysis at room temperature demonstrates pronounced crystalline peaks, suggesting a preferred orientation within the crystal structure. Upon heating, peak broadening suggests grain growth and the onset of recrystallization. SEM and energy‐dispersive spectroscopy analyses corroborate these findings, displaying a fine‐grained, well‐distributed microstructure with a homogenous composition of Sn and Ag elements. EBSD provides insights into the orientation and texture of grains, revealing a weak‐to‐moderate texture across the phases. Postexperiment data indicate a dominant presence of larger grains and significant variation in grain size, with an area‐weighted mean grain size of 68.47 μm and a standard deviation of 8.68 μm; this suggests significant grain growth and coarsening of the Ag3Sn intermetallic compounds. These structural evolutions have crucial implications for the mechanical properties and reliability of the solder alloy in electronic assemblies, underscoring the need for further exploration of lead‐free solder materials in the electronics industry.