Sinter Joining Research Articles

Development of SiC Power Module Structure by Micron-Sized Ag-Paste Sinter Joining on Both Die and Heatsink to Low-Thermal-Resistance and Superior Power Cycling Reliability

Development of SiC Power Module Structure by Micron-Sized Ag-Paste Sinter Joining on Both Die and Heatsink to Low-Thermal-Resistance and Superior Power Cycling Reliability

Driving force for enhancing the cold silver sinter joining using time domain-dependent Ag–Au epitaxy and interfacial stress

We reveal the mechanism of the cold silver sinter joining process using time-dependent characteristics of Ag–Au interactions grown in the highly (111) orientation. In the initial (∼15 min) state at 175 °C, the Ag–Au inter-diffusion layers developed strongly in the (001) direction, and with increasing time (∼60 min), they switched epitaxial growth in the (111) orientation. The die-bonding strength was significantly improved from 14.9 MPa to 37.8 MPa when the sintering time increased from 15 min to 60 min. The gradual Ag–Au epitaxial growth behavior with a higher stacking-fault energy (SFE) at 175 °C was the dominant factor linearly increasing the cold silver sinter joining strength and ultimately maximizing energy absorption leading to fracture. The surface finish of Au, which can contribute to the time-dependent growth of Ag–Au inter-diffusion layers, underwent a dramatic transformation from a Cube texture to a γ-fiber texture over time. This change was attributed to the micro/nanoscale shear deformation, and reduction of the twin boundary fraction. This study unveiled the in-depth fundamental mechanism for strengthening and pressureless cold sinter joining of Ag–Au epitaxial layers by comprehensively considering this texture behavior, changes in X-ray residual stress, and mechanical properties.

Development of Ag@Si composite sinter joining with ultra-high resistance to thermal shock test for SiC power device: Experiment validation and numerical simulation

Owing to its cost-effectiveness and low coefficient of thermal expansion (CTE), micron Si is incorporated into sintered Ag matrix to develop an Ag@Si composite sintering strategy. The Si integration helps reduce cost and alleviate CTE-mismatch of Ag-sintered die attachments. An innovative Ag@Si composite sintering structure is achieved by low-temperature and pressure-less sintering process, where a possibly slight diffusion of native SiO2 on the Si surface toward Ag is indicated by TEM observation, enabling the integration of Ag and Si into one continuous network. Owing to the robust well-bonded composite sintering, the Ag@Si joining strategy provides mechanical/microstructural reliability far beyond the pure Ag sinter joining, demonstrating significant prospects in high-temperature interconnection applications. During the harsh thermal cycling (−50–250 °C), the mitigating effect of the Si addition on CTE mismatch is manifested through the substantial suppression of microstructure deterioration in Ag@Si joint that occurs in pure-Ag-sintered joint, while the shear strength retention rate is doubled. Detailed investigation into the mechanism for elevated performance was conducted by material property and Missies stress analysis. The incorporation of Si helps modify the CTE, elastic properties, and stress distribution of Ag@Si-sintered material, synergistically contributing to the satisfactory joining reliability.

Enhanced Reliability for Power Modules via a New Ag/Si Sinter Joining Strategy

In this work, with an appropriate adding amount of 20 vol% Si, the novel Ag-Si sintering demonstrated enhanced reliability during thermal shock cycling, specifically including the improved bonding strength stability as well as good microstructure maintenance. The high reliability can be attributed to the reduced CTE value of composited Ag-Si sintering inhibition of thermomechanical stress generation, allowing for the ultra-stable joining structure without coarsening, delamination and deformation. Additionally, the well-adhered interface between sintered Ag and Si additive was also verified by examining the microstructure, ensuring the reliable bonding characteristics of the Ag/Si sintered joint.

(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.

(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

In this study, a highly reliable Ag sinter joining on Direct bonded aluminum (DBA) substrate was introduced in SiC power modules. The electroless nickel /electroless palladium/immersion gold (ENEPIG) metallization layer was coated on the DBA substrate with the electroless nickel layer of 7µm and 20 µm. The reliability of SiC/DBA die-attached module by Ag sinter joining was evaluated by thermal shock test (TST) from -50℃ to 250℃ up to 1000 cycles. In the case DBA with the Ni metallization layer of 7µm, severe ups and downs deformation occurred from the Al layer during the TST, leading to uneven variation of sintered Ag layer. The deformation was suppressed when the Ni layer increased to 20 µm. The bonding interface and fracture characteristics were systematically investigated for the both cases, which provide basic understanding the Ag-Au reliability by the design for the metallization layer on substrate.

Failure investigation of a Ag sinter-joining SiC power device under harsh cycling conditions

Silicon-Carbide (SiC) power devices have become the prime candidates for future high-performance energy conversion on account of their superior performance over traditional silicon power devices. The superior electro-thermal properties of SiC power devices permit higher temperature of operation and enable higher power density. Nevertheless, the high operation temperature has introduced new changes in die attachment packaging of the SiC power device, which is one of the most vulnerable places due to a direct connection to the SiC chip. Traditional Pb-free solder-joining is hardly to withstand high temperatures because of the low melting point of solder materials. Besides, severe temperature swings of the SiC chip can introduce severe deterioration in the solder layer due to brittle alloy compounds. Currently, Ag sinter-joining is an ideal connection technique for high reliable power electronics packaging. Due to excellent thermal stability and chemical resistance, the Ag sinter-joining is applicable to various harsh conditions, such as extreme temperatures, high humidity, high heavy current, etc., showing promising application scenarios in die attachment packaging. In this work, we applied Ag sinter-joining to die attachment of a molded SiC device and focused reliability of Ag sinter joining under harsh thermal cycling and power cycling conditions. The SiC device was assembled by a SiC diode and direct bonding copper (DBC) substrate via the Ag sinter-joining. Ribbon bonding was used for the topside connection of the SiC device. An imide resin was applied to mold the SiC device. The thermal cycling test was conducted at a temperature range from -50 °C to 200 °C and the power cycling test was conducted at an initial junction of 200 °C. The structures inspection, thermal resistance variations, and voltage-current curve were investigated to understand failures in the SiC device. The thermal cycling can introduce crazing cracks in the sintered layer due to drastic thermal stress caused by a huge temperature swing. However, the thermal resistance, of the SiC device measured by T3ster, was not significantly affected by the crazing pattern. The Ag sinter-joining also shows an excellent resistance during the power cycling test, while the ribbon lift-off will introduce a final failure of the SiC device. Figure 1 shows a cross section of the structure of the SiC power device with and without a power cycling test. Obvious cracks can be differentiated at the ribbon bonding interface after cycling, while there is no deterioration happened in the sintered Ag layer. Base on the present results, it can be concluded that the Ag sinter-joining can withstand a harsh cycling condition either in huge temperature swings or heavy currents. Figure 1

Improved thermal cycling reliability of Ag sinter joining by optimized chip mounting speed and push depth

Improved thermal cycling reliability of Ag sinter joining by optimized chip mounting speed and push depth

Pressureless sinter joining of bare Cu substrates under forming gas atmosphere by surface-oxidized submicron Cu particles

Pressureless sinter joining of bare Cu substrates under forming gas atmosphere by surface-oxidized submicron Cu particles

Fracture mechanism of microporous Ag-sintered joint in a GaN power device with Ti/Ag and Ni/Ti/Ag metallization layer at different thermo-mechanical stresses

Ag sinter joining technology is emerging as a die attach material for next-generation power modules in high-temperature applications. Thermal shock test has revealed that the fracture characteristics and reliability of sintered Ag joint were influenced by thermo-mechanical stress. This was study conducted to understand the microstructure, vertical crack formation, and fracture behavior of sintered Ag joints which were designed with different metallization layers on a direct bonded aluminum (DBA) substrate, at different thermo-mechanical stresses during thermal shock tests. Two kinds of metallization layers were designed as Ti/Ag and Ni/Ti/Ag layers. A finite element model (FEM) simulation confirmed that the Ni layer prohibited Al hillock-like deformation and generates different thermo-mechanical stresses during the thermal shock test from − 50 °C to 250 °C. Depending on the degradation of the interfaces for both of the Ag-sintered joints, the sintered Ag grain necking thickness and microstructure characteristics including the Ag grain structures, which have a dominant influence on the bonding strength in terms of long-term reliability, are considerably different from the results by an electron back scatter diffraction (EBSD) analysis. This paper proposes a novel metallization technology that can induce joint fracture with complete recrystallization of sintered Ag joints by effectively suppressing interfacial degradation. The mechanism of this technology was systematically analyzed through experiments and FEM simulations.

(Invited) Advances in Ag Sinter Joining for WBG Power Device Assembly and High Temperature Reliability

SiC and GaN, wide bandgap semiconductors (WBGs), providing great benefits such as excellent energy saving, high power density, size reduction of power module, and long-life time, have been attracting many researchers for decades. Actually, there are several new products in the world market. At this moment, one of the technology demands for expanding the market of SiC/GaN is on power packaging technology, which can open these great functions. The increasing power density leads to high operation temperature beyond 200 °C at semiconductor junctions. Not only SiC/GaN devices themselves, insulating ceramic substrates such DBC and DBA must possess good heat-conductivity, heat-resistance and heat-shock resistance. Temperature swing range in operation will be from -50 °C to 250 °C, which is quite severe for the conventional packaging materials including not only insulating substrates, but also solders, wiring, molding compounds, and others. In our group, new assembly materials have been demonstrated and new design rules of die-attach and insulating substrates have been explored to realize reliable SiC/GaN power devices.Sinter joining technology is one of the most promising bonding methods for realizing both high performance and high reliability for WBG devices. The author has developed Ag micron-particles sinter joining with a hybrid of Ag micron/submicron size particles providing excellent heat-resistance beyond 200 °C without any assisting pressure. Ag reacts with oxygen in air resulting in low temperature sintering around 200 °C. The microporous joining structure provides high strength as well as excellent heat/electric conductivity. The die-attached devices are stable even up to 250 °C in thermal shock and in power cycling. For joining Ag sinter materials to various metallization faces such as Au, Ni, Cu or Al, has another critical factor to influence device performance. Ag sinter paste to Ag metallization face is the most recommended one. However, from the various requirements in the market, Ag sinter joining must be also applicable to these dissimilar surfaces. The latest sinter paste enables joining Ag sinter paste even to Al as shown in Fig. 1, which has been recognized as one of the most difficult combination. In this example, the bonding strength reached 35 MPa when bonded at 200 °C.Metal bonded ceramic substrates are the other key materials for WBG power modules. DBAs of AIN, Si3N4 and Al2O3 can survive even in severe thermal shock test between -50 °C to 250 °C. However, significant deformation of metal plates bonded on rigid ceramic insulators results in serious degradation of the WBG assembly. It was found that the properties of surface plating have a key to suppress this surface deformation.Operation monitoring in real service environment will be one of the useful technology for power devices. A nondestructive inspection method by using AE monitoring has been proposed to understand the degradation of module during thermal cycling. During power cycling, abrupt stepwise increases in AE occur showing crack extension in a die-attach layer. Figure 1

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.

Lifetime Prediction of a SiC Power Module by Micron/Submicron Ag Sinter Joining Based on Fatigue, Creep and Thermal Properties from Room Temperature to High Temperature

Ag sinter joining technology has gained increasing attention for its excellent thermal and mechanical properties, especially for high-temperature applications. This study focuses on the lifetime prediction of a SiC power module by Ag sinter joining based on mechanical properties including tensile, fatigue, and creep properties from room temperature to 200°C, as well as thermal properties including thermal conduction and the coefficient of thermal expansion. These mechanical properties and thermal properties of sintered Ag paste were evaluated in the study and the results show that mechanical properties of sintered Ag largely depend on the test temperature. The sintered Ag paste tends to soften at high temperature, and the fracture changed from nearly brittle to totally ductile with the testing temperature increase. From the S–N curve, the fatigue is close to the Morrow equation but not the Coffin–Manson law at room temperature. The finite element simulation of the lifetime based on Morrow’s equation for the sintered Ag layer shows that there has a crack occurrence with one fourth the side length after 10,000 cycles from − 40°C to 200°C but the crack extension area is less than one tenth of the sintered Ag layer. This study will add to the understanding of the high temperature properties and high temperature reliability as well as the lifetime of Ag sinter joining in high-temperature applications.

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.

Strengthening of DBA substrate with Ni/Ti/Ag metallization for thermal fatigue-resistant Ag sinter joining in GaN power modules

This study was carried out to develop a DBA (direct bonded aluminum) substrate with Ni/Ti/Ag metallization to achieve highly functional thermal shock stability of Ag sinter joining in GaN (Gallium Nitride) power modules. GaN /DBA die-attached module structures by Ag sinter joining was performed during harsh thermal shock cycling tests within a temperature range of − 50/250 °C. In the case of DBA without a Ni metallization layer (Ti/Ag), severe degradation occurred at the interface between the sintered Ag and Al due to significant plastic deformation of the Al layer. The shear strength decreased from an initial value of 33.1 MPa to 22.3 MPa after 500 cycles. With EBSD investigation, it was determined that the Al layer underwent sub-grain rotation recrystallization during thermal shock cycles. This led to a non-uniform grain orientation distribution at center and corner locations. On the other hand, Ni/Ti/Ag metallization showed that it can prevent severe Al deformation due to the superior rigidity achieved by Ni metallization. The die-shear strength maintained almost the same value as its initial value, even after 500 cycles. In addition, a numerical simulation analysis determined that the Ag sinter joining structure on the DBA substrate with Ni/Ti/Ag metallization had high functionality in stress relaxation. This study provided a novel approach to design thermal shock stability Ag sinter joining for next-generation power modules in high-temperature applications.

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.

Measurement of Heat Dissipation and Thermal-Stability of Power Modules on DBC Substrates with Various Ceramics by SiC Micro-Heater Chip System and Ag Sinter Joining.

This study introduced the SiC micro-heater chip as a novel thermal evaluation device for next-generation power modules and to evaluate the heat resistant performance of direct bonded copper (DBC) substrate with aluminum nitride (AlN-DBC), aluminum oxide (DBC-Al2O3) and silicon nitride (Si3N4-DBC) ceramics middle layer. The SiC micro-heater chips were structurally sound bonded on the two types of DBC substrates by Ag sinter paste and Au wire was used to interconnect the SiC and DBC substrate. The SiC micro-heater chip power modules were fixed on a water-cooling plate by a thermal interface material (TIM), a steady-state thermal resistance measurement and a power cycling test were successfully conducted. As a result, the thermal resistance of the SiC micro-heater chip power modules on the DBC-Al2O3 substrate at power over 200 W was about twice higher than DBC-Si3N4 and also higher than DBC-AlN. In addition, during the power cycle test, DBC-Al2O3 was stopped after 1000 cycles due to Pt heater pattern line was partially broken induced by the excessive rise in thermal resistance, but DBC-Si3N4 and DBC-AlN specimens were subjected to more than 20,000 cycles and not noticeable physical failure was found in both of the SiC chip and DBC substrates by a x-ray observation. The results indicated that AlN-DBC can be as an optimization substrate for the best heat dissipation/durability in wide band-gap (WBG) power devices. Our results provide an important index for industries demanding higher power and temperature power electronics.

Development of high-strength and superior thermal shock-resistant GaN/DBA die attach structure with Ag sinter joining by thick Ni metallization

With the advent of wide band-gap (WBG) semiconductors like silicon carbide (SiC) and gallium nitride (GaN), the operation temperature of WBG power modules are expected to be over 250 °C. High temperature die-attach materials that can withstand these harsh conditions are emerging as one of the main issues of the reliability of power electronic applications. In this study, high-strength and superior thermal shock-resistant GaN/DBA die attach structures with Ag sinter joining by thick Ni metallization (7 μm) were developed and compared to conventional Pb5Sn soldering die attach. A thermal shock test was conducted at a temperature range of −50/250 °C, holding 30 min at each extreme temperature up to 500 cycles. Consequently, the shear strength of the Ag sinter joining structure was sustained above the initial strength after 500 cycles, which showed durable sinter necks and non-deformed interfaces due to the thick Ni metallization. On the other hand, the Pb5Sn solder joined structure showed a 50% reduction in shear strength after 500 cycles compared to the initial state. Some disadvantages of these solder joints occurred such as an intermetallic compound and interface degradation. Thus, with the new design and evaluation reported in this study, Ag sinter joining can be expected as an environment-friendly replacement die material for the long-term reliability of WBG semiconductor module packaging.

(Invited) Ag Sinter Joining Technology for Different Metal Interface (Au, Ag, Ni, Cu, Al) in Wide Band Gap Power Modules

Wide-bandgap (WBG) semiconductor materials are expected to be widely utilized in next-generation power devices as modules to replace Si-based devices owing to their higher voltage-blocking capability, higher temperature operation, and switching frequencies, as well as their reduced power loss [1][2]. In WBG devices, die-attached materials that bond WBG dies to substrates are crucial for maintaining high performances in environments reaching 250 °C [3]. Conventional die bonding materials, such as Pb-5Sn solder [4], Au-Sn solder [5], and Bi-based solder [6], are not suitable for use in next-generation packaging because cracks can form at the intermetallic solder interface in high-temperature environments . One of the promising alternative approaches is Ag sinter joining technology, which allows for a sintering temperature below 300 °C at low pressure. As the melting point of Ag is higher than 900 °C, Ag sinter joining can be used in high-temperature environments exceeding 250°C .The quality of die-attach by Ag sinter joining depends on the bond-line cohesion from Ag sintering and interfacial adhesion from atomic inter-diffusion. Therefore, the bonding quality depends on the surface finish such as its chemistry and microstructure, on both device and substrate . Usually, electro-plated Ag, electroless-plated Ni(P)/Ag, electro- and electroless-plated Ni(P)/Au is used as surface finish layer for sinter Ag joining. On the other hand, the electro- and electroless-plated Ni(P) technology was well developed and used widely, which can achieve a sufficient resin adhesion resulting from the chemical interaction between the base metal Ni and the resins. However, this additional metallization layer increase costs due to the additional raw materials and processing steps. Ag paste-based, die-attachments on a bare the direct bonded copper (DBC) substrate or direct bonded aluminum (DBA) seems an ideal option due to reduced cost and a simplified process .Here we report a robust joint by Ag sinter joining technology for different metal interface (Au, Ag, Ni, Cu, Al) in wide band gap power modules. Micron-scale Ag flakes (AgC239, Fukuda Metal Foil, and Powder Co. Ltd, Japan) were used as the Ag fillers. The thermal behaviors and morphology of the Ag paste sintered at different temperatures were firstly studied to understand the sintering behavior of the prepared Ag paste. Sinter Ag joint structure for different metal interface was implemented by a sintering process under temperatures of 250 °C in air without pressure. In addition, each sinter Ag joint structure was investigated to obtain a comprehensive understanding for different metal interface bonding. A possible mechanism was proposed based on the SEM and TEM observation of the cross-sectional part of each sinter Ag joint structure.Fig. 1 shows the sinter Ag joint structure for Ag metallization metal interface, and the die shear strength of sinter Ag joint structure for different metal interface. Sintered Ag shows a microporous network structure and bonding well with the Ag metallization layer at the both SiC chip and substrate side. The die shear strength of each sinter Ag joint structure is larger than 25 MPa which comparable with the value of traditional Sn–Pb solders (19~24MPa. This study helps to understand the Ag sinter joining for different metal metallization interface, enlarger the Ag sinter joining for wide band-gap power modules in high temperature applications. ACKNOWLEDGMENTS This work was supported by the JST Advanced Low Carbon Technology Research and Development Program (ALCA) project “Development of a high frequency GaN power module package technology” (Grant No. JPMJAL1610). The author is thankful to the Network Joint Research Centre for Materials and Devices and Dynamic Alliance for Open Innovation Bridging Human, Environment and Material.