Sinter Joints Research Articles

High performance Cu sintering joint for power devices enabled by in-situ generation of Cu particles with multi-level hierarchical structures

Copper (Cu) particle sintering is widely regarded as one of the most ideal interconnect technologies for wide band gap semiconductors owing to its potential for low-temperature curing while withstanding a higher working temperature. Nevertheless, the strict requirements for sintering conditions and high costs limit the widespread application of Cu sintering technology. In this paper, a simple vehicle was introduced into Cu paste formulation to achieve an effective sinter bonding even using commercially available sub-micron or even micrometer Cu particles (C-Cu particles) with the in-situ generation of composite Cu particles. This innovative vehicle comprises Cu salt, a combination of capping agents and reducing agents. The addition of the hybrid capping agent binds Cu atoms to the surface of the C-Cu particles and allows the generated Cu particles (G-Cu particles) produced from the vehicle to grow on their surface, resulting in the in-situ generation of composite Cu particles. Based on the in-situ generated composite Cu particles, sintering experiments were conducted at designated temperatures (200 °C, 225 °C, 250 °C) for various durations (3 min, 5 min, 10 min) in a N2 atmosphere under different pressures (10 MPa, 15 MPa, 20 MPa). A reliable Cu sintered joint with a high shear strength of 41.3 MPa can be achieved at a low temperature (200 °C) using 500 nm C-Cu particles. Moreover, the joints sintered with large size (>3 μm) particles at 250 °C could also reach 43.3 MPa. The in-situ generated composite Cu particles accomplish the transformation of low-energy interfaces of C-Cu/C-Cu to high-energy interfaces of G-Cu/G-Cu, which in turn facilitates low-temperature sintered connection of C-Cu particles and reliable sintered joints formed of large size C-Cu particles. These findings improve the feasibility of Cu sinter bonding in practical applications.

Microstructure evolution and micromechanical behavior of solvent-modified Cu–Ag composite sintered joints for power electronics packaging at high temperatures

With the increased deployment of power modules in demanding conditions, sintering materials, especially composite sintering materials, have raised growing interest due to their cost-effectiveness and suitability. Therefore, this study explores the viability of Cu–Ag composite sintering material, focusing on solvent influence through microstructure and mechanical behavior analysis. Micron-sized particle-based Cu–Ag composite pastes were designed and compared using eight solvents (four epoxy-free and four epoxy-added) based on fluidity and thermal stability. The sintered joints' performance, assessed through shear strength analysis, showed comparable values to pure silver sintering for both epoxy-free and epoxy-added samples. Optimized samples from each solvent system underwent reliability analysis, demonstrating that Cu–Ag joints with epoxy resin exhibited significantly higher shear strength after high-temperature storage and thermal cycling tests. Micromorphology and elemental composition analysis revealed differences in aging mechanisms, primarily attributed to variations in porosity due to oxide formation and pore filling by epoxy resin under different solvent systems. Further nanoindentation characterization of micromechanical properties, including hardness, modulus, and creep properties, during high-temperature aging, established constitutive models for insights into reliability evolution. In conclusion, the optimized epoxy-added Cu–Ag sintered joints proposed in this study demonstrated exceptional reliability and acceptable micromechanical properties, presenting a promising option for high-temperature power packaging.

High-Pressure-Assisted Large-Area (>2400 mm2) Sintered-Silver Substrate Bonding for SiC Power Module Packaging.

The emergence of new semiconductor devices puts forward higher requirements for packaging technology. Sintered silver technology has gradually developed into critical packaging technology in silicon carbide power module packaging due to its good heat dissipation performance and reliability. However, high sintering drive requirements, low sintering densification, and high thermal-mechanical stresses limit the application of sintered silver technology for large-area bonding. In this study, the high-pressure-assisted (≥10 MPa) large-area sintered-silver interconnection process between a substrate and baseplate was discussed. C-scan acoustic microscopy, warpage testing, and microanalysis were used to analyze the effects of drying methods, sintering pressure, and holding time on the sintered joints, and thermal fatigue reliability tests were conducted on large-area sintered silver joints. The results demonstrated that the quality of large-area sintered joints obtained via open-face convective drying is higher than that via close-face convective drying. Combining the performance of sintered joints and productivity, the recommended process condition is determined as follows: open-face convective drying, sintering temperature of 250 °C, sintering pressure of 15 MPa, and holding time of 5 min. Large-area sintered joints have outstanding reliability, with slight delamination of the sintered layer at the corners and no cracking after 1000 cycles of temperature cycling.

CALPHAD accelerated design of advanced full-Zintl thermoelectric device

Since thermoelectric materials have different physical and chemical properties, the design of contact layers requires dedicated efforts, and the welding temperatures are distinctly different. Therefore, a general interface design and connection technology can greatly facilitate the development of thermoelectric devices. Herein, we proposed a screening strategy for the contact materials based on the calculation of phase diagram method, and Mg2Ni has been identified as a matched contact layer for n-type Mg3Sb2-based materials. And this screening strategy can be effectively applied to other thermoelectric materials. By adopting the low-temperature sintering silver nanoparticles technology, the Zintl phase thermoelectric device can be fabricated at low temperature but operate at medium temperature. The single-leg n-type Mg3.15Co0.05SbBi0.99Se0.01 device achieves an efficiency of ~13.3%, and a high efficiency of ~11% at the temperature difference of 430 K has been realized for the Zintl phase thermoelectric device comprised together with p-type Yb0.9Mg0.9Zn1.198Ag0.002Sb2. Additionally, the thermal aging and thermal cycle experiments proved the long-term reliability of the Mg2Ni/Mg3.15Co0.05SbBi0.99Se0.01 interface and the nano-silver sintering joints. Our work paves an effective avenue for the development of advanced devices for thermoelectric power generation.

Power Cycling Reliability with Temperature Deviation of Pressureless Silver Sintered Joint for Silicon Carbide Power Module

SiC devices can enhance power conversion in electric vehicles. However, traditional soldering techniques are limited by their low melting temperatures. Therefore, we used pressureless Ag sintering to assemble a 1200 V/200 A SiC metal-oxide-semiconductor field-effect transistor power module and compared the long-term reliability, electrical properties, and driving performance of the module with those of a similar module assembled using the solder Sn-3.0Ag-0.5Cu (SAC305). To assess sinter joint reliability, we performed power cycling tests over two temperature ranges, 50–150°C and 50–175°C, for 15,000 cycles. Subsequently, we compared the breakdown voltage (BVDSS) and drain-source on-resistance (RDS(ON)) of the SiC power modules and performed cross-sectional analyses of the device bonding interfaces. No difference in BVDSS was found between the Ag-sintered and SAC305-soldered joints. However, the RDS(ON) exhibited minimal variation for the Ag-sintered module but significantly varied for the SAC305-soldered module, suggesting that the former better maintained its characteristics. Furthermore, the electrical characteristics of the SAC305-soldered module underwent more significant alterations with increasing temperature change during power cycling, indicating that cracks propagated throughout the SAC305 soldered joint over time. Therefore, Ag sintering was quantitatively validated as the superior die attachment technology compared to soldering for long-term reliability.

Bonding Characteristics of Solder and Sinter Joints on Active-Metal-Brazing Substrates with Nano Sputtered Ag-Cu-Ti Brazing Filler Metal

In this study, to improve the bonding interfacial characteristics of active metal brazing (AMB) substrates, a Ag-Cu-Ti brazing filler metal (BFM) layer was formed on aluminum nitride (AlN) and silicon nitride (Si<sub>3</sub>N<sub>4</sub>) ceramics by nano sputtering. The AMB substrates were manufactured by brazing bonding. The measured peel strengths of the bonding interfaces of the AlN and Si<sub>3</sub>N<sub>4</sub> ceramics were 2.35 kgf/mm and 4.26 kgf/mm, respectively. Fracture surface analysis revealed AlN crack initiation at the ceramic/BFM interface, which progressed into the ceramic interior. Silicon carbide (SiC) devices for a power module were bonded on the AMB substrates by Sn-3.0Ag-0.5Cu soldering and Ag sintering bonding. To compare the deterioration characteristics of the joint interfaces, a thermal shock test was conducted. Microstructural analysis after the thermal shock test showed that no defects occurred at the Si<sub>3</sub>N<sub>4</sub>/BFM interface, whereas delamination occurred at the AlN/BFM interface. Summarizing, in this study, the characteristics of AMB interfaces coated with a Ag-Cu-Ti BFM using the sputtering process were identified and the suitability of a SiC-based power module package was confirmed.

Thermal reliability of Cu sintering joints for high-temperature die attach

In this study, the thermal reliabilities of sintered Cu joints were investigated under aging and in thermal shock environments. Sintered Cu joints were maintained for 2000 h and 2000 cycles in high-temperature (200 °C) and thermal shock (from −45 to 175 °C) environments, respectively. Subsequently, the microstructural changes, Cu-oxide formation, and bonding strengths of the joints were evaluated. The initial shear strengths of the chips with bare copper and ENIG surfaces were 40.84 and 36.44 MPa, respectively, and after a 2000-h aging test, the strengths decreased to as 39.84 and 18.58 MPa, respectively. With an increase in the aging time under an aging environment of 200 °C, the internal porosity decreased owing to the formation of Cu2O and additional diffusion between the particles. Therefore, the shear strength of the chips with bare copper surfaces was maintained throughout the aging tests, whereas that of the electroless nickel immersion gold chip decreased owing to the formation of Kirkendall voids at the interface, which were attributed to the different diffusion rates of Cu and Au. In addition, Au3Cu, AuCu, and AuCu3 interfacial intermetallic compounds were formed between the Au and Cu layers after the aging test was performed at 200 °C for 2000 h. Copper oxide formed during the thermal shock test caused delamination at the interface because the coefficient of thermal expansion mismatched with that of pure Cu. Understanding this intrinsic Cu oxidation mechanism will widen the prospects for the application of Cu sintering in various devices.

(Invited, Digital Presentation) Fatigue-Resistant of Ag Sinter Joining on Ni-P/Pd/Au Finished DBA Substrate with Thick Ni-P Layer During Thermal Shock Test

The wide band-gap (WBG) semiconductor, such as silicon carbide (SiC) and gallium nitride (GaN), are widely expected to replace conventional Si-based chips, which provide the power modules with higher working temperature larger than 250 degrees. Ag paste sinter joining emerges as a promising alternative for the die attach material in WBG power devices owing to its superior electrical/thermal conductivity as well as a high melting point of 960℃. For Ag paste sinter joining on WBG chip or substrate, most studies are focusing on Ag metallization layers by which the Ag-Ag interface delivers high bonding strength because of the chemical/structural similarity. However, with the superior anti-oxidation/corrosion property, Au metallization layers ensure the Ag-Au joint much wider usage environment than Ag-Ag joint.The study was carried out to develop a highly reliable Ag-Au sintering joint in SiC chip and Direct bonded aluminum (DBA) power modules. The DBA substrate was strengthened by an electroless nickel/electroless palladium/immersion gold (ENEPIG) metallization layer. ENEPIG plated DBA substrate was modified to possess superior mechanical strength by thickening the Ni layer with the thickness of 7µm and 20µm. The reliability of SiC/DBA die-attached module by Ag-Au joining was evaluated during a long-term thermal shock test (TST) from -50℃ to 250℃ up to 1000 cycles. In the case DBA with a Ni metallization layer of 7µm, severe plastic deformation occurred at the Ag-Au interface. By thickened ENEPIG layer with Ni-P layer to 20µm, the Ag-Au interfacial deformation derived from Al plastic deformation was successfully suppressed even after 1000 cycles. The shear strength of as-sintered Ag-Au joint was evaluated to be larger than 35 MPa, but degradation was still found to be the interfacial delamination between Ag paste and ENEPIG substrate during thermal shock test for the two ENEPIG metallization cases. The bonding interface and fracture characteristics were systematically investigated, which provide basic understanding between microstructural evolution and reliability of Ag-Au joint during TST.

Oxidation-enhanced bonding strength of Cu sinter joints during thermal storage test

A special oxidation-enhanced property of Cu sinter joints with Cu particle paste was discovered during thermal storage test. The Cu sinter joints stored under ambient condition with oxidation showed better bonding strength (39.2 MPa) than those protected in vacuum (31.4 MPa), compared to the initial as-bonded strength of 27.6 MPa. It was found that the oxidation decreased the porosity of bonding layer by forming Cu2O shell structure on the sintered Cu microstructure, which enhanced the mechanical property of the sinter joint especially after storage time of 100 h. The corresponding electrical conductivity of solder joint at 100 h is 9.6 × 10−6 Ω, which is still acceptable compared to the as-bonded value of 1.0 × 10−6 Ω. The phenomenon implies that by introducing proper oxidation, Cu sinter joints with improved bonding strength and acceptable electrical conductivity can be achieved, which will provide another potential strengthening process of Cu sinter joining in practical applications.

Investigation and Simulation of the Surface Contact Characteristics of Sinter-Joined Binder Jetting Components

Binder jetting holds great potential for revolutionizing conventional production processes for high-performance components. However, current applications face significant challenges regarding the depowdering and cleaning of complex internal geometries. A novel approach to these challenges is splitting the desired component into smaller, easy-to-clean parts and using sinter bonding to achieve the desired shape. This greatly reduces manual cleaning and preparation time during the production since sintering is required in any case. The sinter joint is currently significantly weaker than the rest of the part and may pose a risk of failure. This study focuses on the effects of different parameters that influence the joint strength and the contact surface between two parts. With different experimental setups, a variety of influences is identified and quantified: depowdering air pressure, component orientation in the build box, initial contact pressure between the green parts, and macroscopic component deformation. The experimental results are supported by a modified Boussinesq contact model. Combining experiments and simulations, it was found that the relative contact between two green parts varies between 5 and 26%, depending on the parameter set used. In this study, the authors introduce the idea of two-part manufacturing in metal binder jetting and subsequent joining of the components in the sintering process.

Fracture behavior of thermally aged Ag–Cu composite sinter joint through microscale tensile test coupled with nano X-ray computed tomography

Herein, we investigated the fracture behavior of thermally aged Ag–Cu composite sinter joints through nano-X-ray computed tomography (nano-CT) combined with microscale tensile testing. Nano-CT results showed that the joint comprised Ag/oxidized Cu flake sintered layer and Cu oxide, which was formed on the Cu substrate; further, pores were present at the interface between the substrate and Cu oxide layer. The tensile test showed that the stress increased with plastic deformation up to a maximum of 308 MPa, before a subsequent steep decrease due to crack initiation inside the sintered layer. The nano-CT and in situ observation results suggest that the microscale joint fractured through the interface between the oxidized Cu flake and Ag. Results obtained herein suggest that microscale tensile testing coupled with nano-CT is an effective approach to describe the intrinsic fracture behavior of joints.

Simulating the Effect of Rigid Frameworks on the Mechanical Properties of Transient Liquid Phase Sintered (TLPS) Alloys

Abstract The need for power electronic devices and materials that can operate in harsh environments, together with the Restriction of Hazardous Substances (RoHS) legislation, has driven industry and researchers to develop new attach materials. Transient Liquid Phase Sintered (TLPS) joints are strong candidates to replace the current die attach materials due to their superior mechanical, thermal, and electrical properties. Despite these qualities, current TLPS systems may exhibit stiff and brittle behavior that can lead to die or attach fracture under large thermomechanical strains during wide temperature range cycling, or under mechanical stress from shock and vibration loading, such as is experienced in automotive electronics. This paper presents an approach for reducing thermal and mechanical strain levels by incorporating Transmission Electron Microscopy (TEM) Cu grids as a reinforcement to the attach material. The grids serve as ductile reinforcement capable of absorbing elastic and plastic energy, and as a barrier for crack propagations through the relative brittle TLPS material. Homogenization calculations were used to evaluate the effective properties of the TLPS, followed by numerical analysis that shows the effect of the grids on the die attach structure, and the mechanical integrity of the design.

Plasticity enhancement of nano-Ag sintered joint based on metal foam

Metal foam with excellent ductility was added into nano-Ag sintered joint to obtain the composite sintered joint with a sandwich structure of sintered Ag/metal foam/sintered Ag. The microstructure, shear behavior and fracture morphology of the composite sintered joint were investigated in this study. Experimental results indicate that the addition of ductile metal foam enhances the plasticity of composite sintered joint. As the number of pores of Cu foam increased from 110 to 500 per inch, the shear strength increased from 8.28 to 11.26 MPa. The composite sintered joint with 110ppi (pores per inch) Ni foam showed a higher shear strength than the other composite sintered joints did because of the higher Young’s modules and shear modules of Ni foam. In the Ni foam@nano-Ag composite sintered joint, cracks appeared at the interface between the metal foam and the nano-Ag sintered structure because of the mismatch of coefficient of thermal expansion (CTE). Compared with the Ni foam, the addition of Cu foam effectively depressed the generation of cracks at the interface between the metal foam and the nano-Ag sintered structure.

Online Thermal Resistance and Reliability Characteristic Monitoring of Power Modules With Ag Sinter Joining and Pb, Pb-Free Solders During Power Cycling Test by SiC TEG Chip

Despite the rapid progression of silicon carbide (SiC) power devices, the thermal characteristic evaluation during power cycling at high temperature (>200 °C) is an issue. In this article, a fast and miniaturized evaluation system with online thermal characteristic measurement function was introduced by an n-doped 4H SiC thermal engineering group (TEG) chip. Online thermal resistance measurement of a power module structure by Ag sinter joining with micron/submicron Ag particles paste in low temperature, low pressure, and cooling system by a thermal interface material bonding was performed. High-temperature reliability was systemically investigated by power cycling tests by switching on / off the power source which is connected to the SiC-TEG chip by Au wires. The total thermal resistance of the power module from the SiC-TEG chip to the cooling system increased from 0.5 to 0.53 K/W with the enhanced power source, and remained almost same after 20 000 power cycling at a swing temperature ΔTj of 150 °C. Furthermore, the SiC-TEG power module structure with the die attached with Pb and Pb-free solders, alongwith the same power source as sinter Ag paste was also measured. The Ag sinter joint possesses the lowest thermal resistance and highest high temperature reliability during power cycling compared with Pb and Pb-free die-attach materials.

Improved sinterability of micro-scale copper paste with a reducing agent

The sinterability of a micro-scale copper paste was improved by adding a reducing agent to the binder. The size of the copper particles ranged from 1 to 3 μm. The reducing agents were various dicarboxylic acids (glutaric, succinic, and adipic acid). The binder for the copper paste was formulated by mixing dicarboxylic acid and poly ethylene glycol (PEG). The shear strengths of the dicarboxylic acid + PEG samples were much higher than that without the reducing agent. The glutaric + PEG sample had a shear strength of over 40 MPa after sinter joining at 350 °C, which was higher than those of the succinic + PEG and adipic + PEG samples. The shear strength of the copper sinter joint did not significantly change with a bonding time up to 30 min.

Mechanical characteristics and fracture behavior of GaN/DBA die-attached during thermal aging: pressure-less hybrid Ag sinter joint and Pb–5Sn solder joint

Ag sinter joining provides superior mechanical and thermal/electrical properties and is considered to become a leading next-generation wide band-gap (WBG) die-attach material. However, the microstructural evolution and mechanical characteristics of Ag sinter joining when subjected to high temperature have never been directly compared to those same characteristics of solder materials. In this study, we have evaluated the high-temperature and long-term reliability of a GaN/DBA die-attached module by pressure-less Ag sinter joining and Pb–5Sn solder in a harsh thermal aging test. Both the Ag sinter joining and Pb–5Sn solder were subjected to a thermal aging test of up to 1000 h at 250 °C. Initial shear strength of the Ag sinter joint exceeded 42 MPa, and increased stably up to 1000 h without any defects such as interface oxidation, diffusion, or mechanical deformation. The increase in shear strength of the Ag sinter joints was the result of necking growth of the sintered Ag during thermal aging. On the other hand, the shear strength of the Pb–5Sn joints exhibited substantially decreased shear strength (by 60%) after aging 250 h. NixSnx intermetallic compounds (IMC) were also formed and serious interface degradation occurred during the aging process. These microstructure changes and mechanical characteristics have an important influence on mechanical reliability and, with that in mind, the tendency of fracture mechanism was investigated in detail by SEM–EDX. This study systematically examines the fracture mechanism on the microstructure of a DBA substrate and on high-temperature packaging during thermal aging tests for WBG semiconductor device applications.

Highly porous Ni-free Ti-based scaffolds with large recoverable strain for biomedical applications

Highly porous Ti–18Zr-12.5Nb–2Sn (at.%) scaffolds with porosities of 70%, 75% and 80% were prepared by sintering rapidly solidified alloy fibers. Superelastic behavior of alloy fiber was investigated by the dynamic mechanical analyzer (DMA). Phase identifications of alloy fiber and scaffold were studied by X-ray diffraction (XRD). Precipitates in alloy fiber were investigated by transmission electron microscope (TEM). Porous structure of alloy scaffold was observed by scanning electron microscope (SEM). Mechanical properties and the superelasticity of alloy scaffold were investigated using compressive test. The superelasticity of alloy fibers was improved after aged at 673 K for 3.6 ks due to α precipitates. The sintered scaffolds showed three-dimensional networks with fiber-fiber sintering joints. The compressive yield stress and elastic modulus of the alloy scaffolds aged at 673 K for 3.6 ks were in the range of 5.0–16.7 MPa and 0.33–1.05 GPa, respectively. These values were a close match to those for cancellous bone. The recoverable strain increased from 3.2% to 3.7% with the increase in porosity from 70% to 80% in aged Ti–Zr–Nb–Sn scaffolds when tested at human body temperature (310 K).

Superelastic Ti-18Zr-12.5Nb-2Sn (at.%) alloy scaffolds with high porosity fabricated by fiber metallurgy for biomedical applications

β-type Ni-free Ti-based alloys are promising materials for biomedical applications. In this study, highly porous Ti-18Zr-12.5Nb-2Sn (at.%) alloy scaffolds with a porosity of about 80% were fabricated by a process of combining rapid solidification method and fiber metallurgy technique for the replacement of damaged human cancellous bone. Alloy fibers were produced by melt overflow technique. Phase identifications of alloy fiber and scaffold were studied by X-ray diffraction (XRD). Transformation behavior and microstructure of alloy fiber were investigated by differential scanning calorimetry (DSC) and transmission electron microscope (TEM), respectively. Superelastic behavior of alloy fiber was investigated by the dynamic mechanical analyzer (DMA). Porous structure of scaffold was observed by scanning electron microscope (SEM). The mechanical properties and superelasticity of scaffold were investigated by compressive test. The rapidly-solidified fiber consisted of β phase, athermal ω phase and nanodomains. Clear superelastic behavior with the recoverable strain of 4.5% for 5% pre-strain was observed in rapidly-solidified alloy fiber. Three-dimensional networks with fiber-fiber sintering joints were observed in the as-sintered scaffold which consisted of predominant β phase, α phase and isothermal ω phase. The scaffold annealed at 973 K consisted of single β phase. Stress-induced martensitic transformation of β→α" occurred during the compressive test. The compressive plateau stress and elastic modulus of the as-sintered and annealed scaffold were found to be 7.9 MPa and 0.43 GPa, 7.4 MPa and 0.41 GPa, respectively, similar to those of cancellous bone. A recoverable strain of 3.4% was observed in the annealed scaffold at body temperature (310 K).

Pressureless Silver Sintering of Silicon-Carbide Power Modules for Electric Vehicles

Pressureless silver (Ag) sintering was optimized at 250°C in vacuum and nitrogen gas atmosphere with silicon carbide (SiC) chips, and silicon nitride active metal-brazed substrates (AMB). A 1200-V/200-A power module was developed using a pressureless Ag-sintered live SiC metal–oxide–semiconductor field-effect transistor (MOSFET) device and a Si3N4 AMB substrate module, and diverse reliability tests were performed. The void content and the bonding layer thickness of the Ag sinter joints were 1.2–3.4% and 68.5 µm. The bonding strength of the Ag sinter joints after thermal cycling testing (TCT) were slightly decreased due to the crack generation. In contrast, high-temperature storage testing (HTST) was carried out for a long time at high temperature, the sintering process occurred continuously, and the shear strength increased by 31% after HTST. The drain–source on-resistance (RDS(ON)) of a SiC MOSFET power module before and after the TCT and power cycle test was similar to the as-sintered state without change.

Necking growth and mechanical properties of sintered Ag particles with different shapes under air and N2 atmosphere

Ag sinter joint is gaining greater attention for use with wide-bandgap die attach modules in high-temperature applications. In this study, we have investigated both the necking growth of Ag grain and the mechanical properties of sintered Ag with different Ag particle shapes in a low-temperature, pressure-less sintering process in air and N2. The necking growth ratio of Ag grains plays an important role in the mechanical properties of sintered Ag. Large necking growth corresponds to stronger tensile fracture strength of sintered Ag paste and stronger die shear strength. Self-generated Ag nanoparticles (AgNPs) with of a size less than 10 nm were observed under an air atmosphere, an atmosphere that produces larger necking growth than does that of N2. In addition, self-generated AgNPs were observed in sintered Ag flake particles specimens. Ag flake particles also lead to larger necking growth than that of sintered Ag spherical particle specimens. Self-generated AgNPs accumulated together due to their high surface energy, thus improving the necking growth of Ag grain and leading to a stronger fracture strength. In addition, it was revealed that both the oxygen element and the grain residual strain of initial Ag particles play important roles in the AgNPs self-generation during the sintering process. This study enhances our understanding of the sintering mechanism of Ag particles and the relationship between grain necking growth and its mechanical properties.