Bonding strength of Cu/Cu joints using sintering process of micro-sized Cu particles for high-temperature application

2019 ◽  
Vol 2019 (HiTen) ◽  
pp. 000085-000090
Author(s):  
Hiroshi Nishikawa ◽  
Xiangdong Liu
Keyword(s):  
Shear Strength ◽  
High Temperature ◽  
High Efficiency ◽  
Reduction Process ◽  
Power Device ◽  
Sintering Process ◽  
Oxidation Reduction ◽  
Die Attach ◽  
Power Modules ◽  
Temperature Application

Abstract Recently the new SiC power device provides the possibility to develop the next-generation power conversion circuit with high efficiency and high power density. The SiC power device can operate with significant lower power loss and higher operating temperature, which contributes to miniaturization and higher performance of power modules. To assemble these power modules, the high temperature packaging technology such as die attach process is needed. As a die attach process, we have proposed a simple oxidation-reduction bonding (ORB) process to achieve good Cu-to-Cu joints using micro-sized Cu particles. In this study, the effect of the oxidation-reduction process on the surface morphology of Cu particles was evaluated by SEM observation, and the shear strength of the Cu-to-Cu joints was investigated. As a result, the bonding using micro-sized Cu particles was successfully achieved and the shear test results showed that the joints by ORB process had a shear strength of more than 20 MPa.

Effect of isothermal aging at 250 °C on shear strength of joints using Sn-Coated Cu particle paste for high-temperature application

2017 ◽  
Vol 2017 (HiTEN) ◽  
pp. 000202-000206
Author(s):  
Hiroshi Nishikawa ◽  
Xiangdong Liu ◽  
Siliang He
Keyword(s):  
Shear Strength ◽  
High Temperature ◽  
Isothermal Aging ◽  
Transient Liquid Phase ◽  
Process Time ◽  
Melting Temperatures ◽  
Tlp Bonding ◽  
Die Attach ◽  
Temperature Application ◽  
Component Assembly

Abstract High-temperature joining is a key technology for electronic component assembly and other high-temperature applications. As a die attach process for power devices, we focus on a transient liquid phase (TLP) bonding, which can be operated at a low temperatures while resulting in higher re-melting temperatures of bonded joints. However, some drawbacks of this technology still remain. For example, the duration of this process is too long, up to a few hours, and multiple hours of annealing are required to achieve a thermodynamically stable joint. So we are studying on a TLP bonding using Sn-coated Cu particles to reduce the bonding process time. In this study, we evaluated the effect of isothermal aging at 250 °C on the shear strength of Cu/Cu joints using a Sn-coated Cu particle paste. As a result, a thermally stable joint fully comprising Cu3Sn phase with a dispersion of Cu particles could be obtained after sintering for 30 s at 300 °C under a formic acid atmosphere. The shear strength of the joint before isothermal aging was about 25 MPa and the shear strength after isothermal aging at 250 °C for 1000 h was more than 25 MPa.

Mobile Packaging and Interconnect Trends

2014 ◽  
Vol 2014 (DPC) ◽  
pp. 1-21
Author(s):  
Brandon Prior
Keyword(s):  
Shear Strength ◽  
High Temperature ◽  
Thick Film ◽  
Cross Sections ◽  
Shear Test ◽  
Short Review ◽  
Test Machine ◽  
Die Attach ◽  
Shear Failures ◽  
Film Substrate

This paper will focus on emerging and fast growth package solutions to meet mobile products' density and cost requirements. A short review of where package miniaturization and modularization has taken us so far, and where it will lead in the next 5 years. Teardowns of high density systems and packages will be used to illustrate key points. Low temperature Ag sintering technology provides a lead-free die attachment compatible with high temperature (300°C) applications. Previous work with Ag sintering has required some pressure during the sintering process or been limited to small area die. In this paper, a pressureless sintering of micro-scale silver paste procedure is presented for large (8mm x 8mm) area die. Experimental combinations included: Ag metallized Si die, Au metallized Si die, Ag thick film substrate metallization, Au thick film substrate metallization, PdAg thick film metallization and sintering temperature. For Au metallization (die and/or substrate), the initial shear strength results were good with 8mm x 8mm die sintered at lower temperatures (200°C). The shear strength was out range of our shear test machine (100 kg), corresponding to >15.3 MPa. However, after aging for 24 hours at 300°C, the shear strength dropped significantly to 40.38 Kg (6.183 MPa). An SEM was used to characterize cross sections of as-built and aged sample. The decrease in die shear strength with high temperature sintering (250°C and 300°C) or high temperature aging is attributed to surface diffusion of Ag along the Au surface resulting in a dense Ag layer adjacent to the Au surface and a depletion layer within the die attach on the opposite side of the the dense Ag layer. Shear failures occurred through the depleted region. For Ag metallization, no decrease in shear strength was observed with 300°C aging. Shear strength of 8x8cm2 dies was out range of our shear test machine (>100 kg, >15.3 MPa) as-built. The shear strength remained out of range (>15.3MPa) after more than 2000 hours of 300C aging.

Evaluation of Low Cost, High Temperature Die and Substrate Attach Materials for Silicon Carbide (SiC) Power Modules

2018 ◽  
Vol 2018 (1) ◽  
pp. 000317-000325
Author(s):  
Sayan Seal ◽  
Brandon Passmore ◽  
Brice McPherson
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Operating Conditions ◽  
Acoustic Microscopy ◽  
Switching Frequency ◽  
Power Devices ◽  
Formidable Challenge ◽  
Die Attach ◽  
Power Modules ◽  
High Switching Frequency

Abstract The performance of SiC power devices has demonstrated superior characteristics as compared to conventional Silicon (Si) devices. Some of the advantages of SiC power devices over Si include higher voltage blocking capability, low specific on-resistance, high switching frequency, high temperature operation, and high power density. Thus, SiC modules are capable of processing significant levels of power within much smaller volumes compared with its Si counterparts. These high thermal loads present a formidable challenge in integrating SiC devices in power modules. For example, known-good materials and processes for silicon power modules are not rated at the aggressive operating conditions associated with SiC devices. Two of the most critical interfaces in a power electronics module are the die-attach and substrate- attach. A degradation in these interfaces often results in potentially catastrophic electrical and thermal failure. Therefore, it is very important to thoroughly evaluate die-attach materials before implementing them in SiC power modules. This paper presents the methodology for the evaluation of die attach materials for SiC power modules. Preforms of a lead-free high-temperature attach material were used to perform a die and substrate attach process on a conventional power module platform. The initial attach quality was inspected using non- destructive methods consisting of acoustic microscopy and x-ray scanning. Die attach and substrate attach voiding of < 5% was obtained indicating a very good attach quality. Cross-sectioning techniques were used to validate the inspection methods. The initial attach strength was measured using pull tests and shear tests. The measurements were repeated at the rated temperature of the module to ensure that the properties did not degrade excessively at the service temperature. At the rated module temperature of 175 °C, the die bonding strength was found to be ~ 75 kg. This was only 25% lower than the strength at room temperature. In addition, the contact pull strength was measured to be > 90 kg at 175 °C, which was 25% lower than the value measured at room temperature. The effect of power cycling and thermal cycling on the quality and strength of the die and substrate attach layers was also investigated.

PRESSURELESS SINTERING OF NANO- AG PASTE WITH LOW POROSITY FOR DIE ATTACH

2014 ◽  
Vol 2014 (1) ◽  
pp. 000092-000098 ◽  
Author(s):  
Sihai Chen ◽  
Guangyu Fan ◽  
Xue Yan ◽  
Chris LaBarbera ◽  
Lee Kresge ◽  
...  
Keyword(s):  
Shear Strength ◽  
Thermal Aging ◽  
Migration Rate ◽  
Dense Layer ◽  
Pressureless Sintering ◽  
Thermal Shock Test ◽  
Sintering Process ◽  
Shock Test ◽  
Die Attach ◽  
Ag Paste

A novel nano-Ag sintering paste C has been developed for a pressureless sintering process under air. Paste C was sintered at 250°C (C1) and 280°C (C2), respectively; C1 showed a slightly higher porosity but higher shear strength after aging at 250°C for 840 hours. Both C1 and C2 exhibited a microstructure much more stable than the control solder 92.5Pb/5Sn/2.5Ag, which suffered both IMC spalling after thermal aging and voiding. Ag migration toward the DBC to form a dense layer of AgCuNi(Au) was observed for all nano-Ag pastes that were studied, with C1 and C2 being more moderate in the migration rate. The Ag migration could be attributed to the tendency of Ag to form an alloy with Au, with abundant Ni and Cu at the DBC side, and appeared to be affected by the chemistry of nano-Ag paste. A liquid to liquid thermal shock test from −45°C to 240°C was attempted, and was considered too harsh for the die/DBC system employed in this study.

LT-TLPS Die Attach for High Temperature Electronic Packaging

2014 ◽  
Vol 11 (1) ◽  
pp. 7-15
Author(s):  
Hannes Greve ◽  
F. Patrick McCluskey
Keyword(s):  
Shear Strength ◽  
High Temperature ◽  
Melting Point ◽  
Low Temperature ◽  
Transient Liquid Phase ◽  
Liquid Phase Sintering ◽  
Die Attach ◽  
Metallic Interfaces ◽  
Dsc Analyses ◽  
Transient Liquid Phase Sintering

Low temperature transient liquid phase sintering (LT-TLPS) can be used to form high-temperature joints between metallic interfaces at low process temperatures. In this paper, process analyses and shear strength studies of paste-based approaches to LT-TLPS are presented. The process progression studies include DSC analyses and observations of intermetallic compound (IMC) formation by cross-sectioning. It was found that the sintering process reaches completion after sintering times of 15 min for process temperatures approximately 50°C above the melting point of the low temperature constituent. For the shear studies, test samples consisting of copper dice and copper substrates joined by sintering with a variety of sinter pastes with different ratios of copper and tin have been assessed. A fixture was designed for high temperature enabled shear tests at 25°C, 125°C, 250°C, 400°C, and 600°C. The influence of the ratio of the amount of high melting-point constituent to the amount of low melting-point constituent on the maximum application temperature of the sinter paste was analyzed. Ag20Sn and Cu50Sn pastes showed no reduction in shear strength up to 400°C, and Cu40Sn pastes showed high shear strengths up to 600°C. It was shown that LT-TLPS can be used to form high temperature stable joints at low temperatures without the need to apply pressure during processing.

Investigation of Die Attach for SiC Power Device for 300°C Applications

2013 ◽  
Vol 740-742 ◽  
pp. 1032-1035 ◽  
Author(s):  
A. Drevin-Bazin ◽  
F. Badawi ◽  
F. Lacroix ◽  
J.F. Barbot
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Creep Behavior ◽  
High Stress ◽  
Power Device ◽  
High Concentration ◽  
Die Attach ◽  
Creep Curves ◽  
High Stress Level ◽  
High Creep Resistance

The mechanical properties of die attach system SiC/Au-Ge/Au-Ni-Cu-Si3N4 using the eutectic Au-Ge solder (Teut = 356°C) were investigated in a temperature range up to 300°C. The as-resulting structure of the solder is observed to be lamellar with pockets of high concentration of Au close to the interfaces. The shear strength of joint decreases with temperature but, even at 300°C, its value is well higher than the IEC standard. The creep behavior of Au-Ge solder alloy was also investigated at 300°C for different strain levels. The creep curves show a high creep resistance even for high stress level.

Reliability and Corrosion Resistance of High Temperature Lead-Free BiAgX™ Paste

2014 ◽  
Vol 2014 (HITEC) ◽  
pp. 000347-000354 ◽  
Author(s):  
HongWen Zhang ◽  
RunSheng Mao ◽  
Ning-Cheng Lee ◽  
Satoshi Tanimoto
Keyword(s):  
Corrosion Resistance ◽  
Shear Strength ◽  
High Temperature ◽  
Salt Water ◽  
Lead Free ◽  
Water Spray ◽  
Bond Shear Strength ◽  
Die Attach ◽  
Increasing Temperature ◽  
Average Bond

The BiAgX™ paste, designed for die attach application, composed of the majority of BiAg powders (melting point >260°C) and the minority of additive powders. The additive powders are dominating the interfacial reaction to improve the wetting of the paste on various commonly-used surface finish materials. After reflow, the joint shows the above 260°C remelting temperature. The average bond shear strength of BiAgX joint between SiC die and AMBC-SiN substrate (Package A) decreases from 54MPa to 16MPa with increasing temperature from RT to 250°C. Upon thermal storage at 200°C or 230°C for 3000hrs, the bond shear strength decreases from 54MPa to 38MPa and 21MPa, respectively. Upon thermal cycling from −55°C to 125°C for 2000cycles and thermal shock from −55°C to 150°C for 2000cycles, BiAgX outperforms Pb5Sn2.5Sn (Package B). BiAgX also show the better corrosion resistance than SAC305 and Pb5Sn2.5Ag under 96hrs salt water spray (SWS) tests.

Evaluation of Pressure Free Nanoparticle Sintered Silver Die Attach on Silver and Gold Surfaces

2013 ◽  
Vol 2013 (HITEN) ◽  
pp. 000237-000245 ◽  
Author(s):  
G. Lewis ◽  
G. Dumas ◽  
S. H. Mannan
Keyword(s):  
Shear Strength ◽  
Cross Sections ◽  
Storage Time ◽  
Sintering Process ◽  
Die Attach ◽  
Free Process ◽  
Sintered Ag ◽  
Bondline Thickness ◽  
Ag Substrate ◽  
Thickness Measurements

A commercially available silver nanoparticle based die attach material was used in a pressure free process to bond 2.5 mm square Ag plated Si die to Ag and Au plated substrates. The two substrate types were 5mm square Ni/Ag plated silicon substrate and a W/Ni/Au metallised cofired alumina package. The assemblies were stored at 300 °C for up to 500 h and the morphology of the sintered Ag and the shear strength was monitored as a function of time. Bondline thickness measurements were carried out after following the paste manufacturer's drying and sintering temperature profile. On Ag substrate it was found that die shear strength increased with storage time. The fracture surfaces of the sheared die and substrate as well as cross sections of untested die were examined using electron microscopy. It was found that the Ag grains grew in size and porosity decreased over time. There was also a clear difference in morphology between sintered Ag at the die edge and centre. During shearing the Ni layer was found to separate from the chip at the edges of the die after ageing. On Au substrate, it was found that die shear strength decreased with storage time. It was found that the Au diffused into the Ag, creating a low porosity Au-Ag layer. Ag also migrated towards the Au surface, leaving behind a layer of voids which contributed to weakening of the joint. Rapid Au diffusion was associated with the high density of grain boundaries arising from the sintering process.

Investigation into the Role of Different Substrate Ni Compositions and Plating Methods on Die Attach Reliability

2015 ◽  
Vol 2015 (HiTEN) ◽  
pp. 000073-000082
Author(s):  
Jinzi Cui ◽  
R. Wayne Johnson ◽  
Michael C. Hamilton
Keyword(s):  
Shear Strength ◽  
High Temperature ◽  
High Power ◽  
Diffusion Barrier ◽  
Die Attach ◽  
High Temperature Storage ◽  
The Impact ◽  
Direct Bond Copper ◽  
Temperature Storage

Nickel is a commonly used diffusion barrier for direct bond copper (DBC) substrates used in high temperature, high power applications. The Ni can be deposited by electroless or electrolytic plating and may be pure Ni, Ni:P, Ni:B or Ni:Co. The reactivity of these different Ni layers with AuGe and BiAgX® solder is explored. Specifically the reaction to form Ni-Ge intermetallics and NiBi3 during high temperature storage and the impact on die shear strength and failure mode are discussed.

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