Improvement of the Bond Strength of Ag Sinter-Joining on Electroless Ni/Au Plated Substrate by a One-Step Preheating Treatment

Kim

2021

Journal of Elec Materi

Low-temperature and pressureless silver (Ag) sintering was applied to a 1200 V/200 A silicon carbide (SiC) metal-oxide-semiconductor field-effect transistor (MOSFET) power module with a Ag-finished silicon nitride active metal-brazed substrate, and the results were evaluated for applicability in electric and hybrid electric vehicles. The sintering was performed at 220-240°C, 90 min in vacuum under nitrogen gas conditions; the bonding strength, bonding layer thickness (BLT), void content, and densification of the as-sintered Ag joints were 39 MPa, 71.4 lm, 2%, and 90.5%, respectively. The shear strength, BLT, densification, and microstructure of the Ag-sintered joints were compared before and after the thermal cycling test (À 50-150°C, 1100 cycles, TCT) and high temperature storage test (200°C, 1000 h, HTST). To simultaneously compare the electrical properties of the SiC power module with lead (Pb)-free solder joints, the same SiC MOSFET power module was manufactured using a Sn-3.0Ag-0.5Cu (SAC305) Pb-free solder. The shear strength and densification after TCT and HTST were 35.5 MPa and 39.7 MPa, as well as 92.8% and 94.8%, respectively. The on-resistance and total switching efficiency of the SiC power module with the Ag-sintered joint were also compared to those of the SAC305 solder joint module, which evinced maximum values of 7.3 mX and 10.7 mJ that were superior to those of 8.5 mX and 11.3 mJ for the SAC305 solder joint, respectively. Under the same measurement conditions, the maximum generated current and voltage values are lower than those of the solder joint module, so it is envisaged that stable power module operation is realizable for long-term use. The Ag-sintered joint surpassed the SAC305 solder interconnects in terms of the electrical and mechanical reliability of the power module. When a SiC wide band gap device was used, it was discovered that Ag sintering was superior to Pb-free solder interconnects to increase the power conversion efficiency of the power module.

Section: Thermal Cycling and High-temperature Storage Test Conditionsmentioning

confidence: 81%

Electrical and Microstructural Reliability of Pressureless Silver-Sintered Joints on Silicon Carbide Power Modules Under Thermal Cycling and High-Temperature Storage

Kim

2021

Journal of Elec Materi

2020 IEEE 8th Electronics System-Integration Technology Conference (ESTC)

“…Therefore, the good bonding for the study maybe attribute to the larger Au grains size. In addition, it was reported that the Ni could diffusion into Au lay during the sintering process for the ENIG substrate case, which lead to a weak interface bonding with sintered Ag layer due to the Ni oxide generation[9]. In this study, the Pd layer prohibited the Ni diffusion and thus assisted the Ag-Au interface bonding.In addition, the die shear strength was slightly increased to 36.5 MPa after 1000 h, which means that the bonding structure have a good high temperature stability.…”

mentioning

confidence: 73%

“…Electroless Ni plating (EN) with hypophosphate as the reducing agent, electroless pure palladium (or palladium phosphorus) plating (EP) with formate as the reducing agent, cyanide-type immersion gold plating (IG), usually called as ENEPIG, has received a lot attention because of its easy process, good solder ability, low consumption rate as well as good mechanical reliability properties. Ag sinter joining on Au finish surface is a very hot topic, but there are some difficulties to obtain a robust Ag-Au joint in a low temperature, low pressure sintering [7][8][9]. Furthermore, thermal aging reliability of Ag-Au joint is another issue, especially for the ENIG process where the Ni layer diffusion into the Au layer via Au grains boundaries, leads to die shear strength decrease after aging test.…”

Section: ⅰ Introductionmentioning

confidence: 99%

Evaluation of high temperature reliability of SiC die attached structure with sinter micron-size Ag particles paste on Ni-P/Pd/Au plated substrates

Chen

Zhang

Suganuma

2020

Self Cite

Next generation power modules empowered by wide bandgap semiconductors like SiC and GaN can operate for a higher power than Si-based semiconductors at a high temperature over 250 ℃ . Ag sinter joining as a die attach material with a high melting point and good thermal conductive properties have obtained many attentions for the next generation power modules. This study investigated the bonding properties and the high temperature reliability of Ag sinter joining on ENEPIG (Electroless Ni plating (EN), Electroless palladium plating (EP) and immersion gold plating (IG)) metallized DBA substrates. The initial die shear strength for SiC (3x3 mm 2 ) power modules was 33.9 MPa at 250℃ sintering without assisted pressure in air conduction. The high temperature reliability of Ag sinter joint structure was evaluated at 250 ℃ aging for 1000 h. The Ag-Au interface bonding mechanism, fracture behaviors and microstructure evolution of sinter Ag-Au joint were systematically analyzed. In addition, the connected Ag particles change to coarse with pore size increase during the aging process. The Ag-Au interdiffusion layer also increased with the aging time but not clearly delamination occurrence. The die shear strength was slightly increased from the initial to 36.5 MPa after aging 1000 h, which meaning the Ag-Au joint possessed a good high temperature reliability. This study should add the understanding of the reliability issues of Ag sinter joining on Au finished substrate for its applications at high temperature.

“…(3) The heat flux generated by the heated powder and the heat loss caused by evaporation are disregarded; (4) The impact of shielding gas, feeding gas and powder on the melt pool surface is omitted.…”

Section: Models and Parametersmentioning

confidence: 99%

“…Substrate preheating is an important factor because it can change the thermal process of the process. Related studies have shown that preheating the substrate/workpiece before the deposition process can reduce the thermal stress generated during the deposition process and ultimately reduce/eliminate the resulting delamination and cracking [ 1 , 2 , 3 ], and it is used in multiple applications, such as joining, welding, and laser melt deposition [ 4 , 5 , 6 ]. However, the preheating effect may affect the final expected properties of the deposited material.…”

Section: Introductionmentioning

confidence: 99%

Investigating the Impact of Substrate Preheating on the Thermal Flow and Microstructure of Laser Cladding of Nickel-Based Superalloy

Jin,

Kong,

2024

Materials

The preheating of the substrate in laser additive superalloys can reduce residual stress and minimize cracking. However, this preheating process can lead to changes in the heat transfer conditions, ultimately affecting the resulting microstructure and mechanical properties. In order to explore the influence of substrate preheating on the formation of laser cladding, this research focuses on investigating the characteristics of Inconel 718, a nickel-based superalloy, as the subject of study. To simulate the temperature and flow field of laser cladding, a 3D computational fluid dynamics (CFD) model is employed. By varying the initial preheating conditions, an investigation is conducted into the distribution of the temperature field under different parameters. This leads to the acquisition of varying temperature gradients, G, and solidification speeds, R. Subsequently, an analysis is carried out on both the flow field and solidification microstructure in the melt pool. The results demonstrate that the preheating of the substrate results in a slower cooling rate, ultimately leading to the formation of a coarser microstructure.