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.

scholarly journals Evolution of Transient Liquid-Phase Sintered Cu–Sn Skeleton Microstructure During Thermal Aging

2019 ◽  
Vol 9 (1) ◽  
pp. 157 ◽  
Author(s):  
Hiroaki Tatsumi ◽  
Adrian Lis ◽  
Hiroshi Yamaguchi ◽  
Tomoki Matsuda ◽  
Tomokazu Sano ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Thermal Aging ◽  
Resin Composite ◽  
Transient Liquid Phase ◽  
Nitrogen Atmosphere ◽  
Sintering Process ◽  
Thermal Reliability ◽  
Cu6sn5 Phase ◽  
Die Attach ◽  
Negative Impacts

The evolution of the transient liquid-phase sintered (TLPS) Cu–Sn skeleton microstructure during thermal aging was evaluated to clarify the thermal reliability for die-attach applications. The Cu–Sn skeleton microstructure, which consists of Cu particles connected with Cu–Sn intermetallic compounds partially filled with polyimide resin, was obtained by the pressure-less TLP sintering process at 250 °C for 1 min using a novel Cu-solder-resin composite as a bonding material in a nitrogen atmosphere. Experimental results indicate that the TLPS joints were mainly composed of Cu, Cu6Sn5, and Cu3Sn in the as-bonded state, where submicron voids were observed at the interface between Cu3Sn and Cu particles. After thermal aging at 150, 175, and 200 °C for 1000 h, the Cu6Sn5 phase fully transformed into Cu3Sn except at the chip-side interface, where the number of the submicron voids appeared to increase. The averaged shear strengths were found to be 22.1 (reference), 22.8 (+3%), 24.0 (+9%), and 19.0 MPa (−14%) for the as-bonded state and specimens aged at 150, 175, and 200 °C for 1000 h, respectively. The TLPS joints maintained a shear strength over 19 MPa after thermal aging at 200 °C for 1000 h because of both the positive and negative impacts of the thermal aging, which include the transformation of Cu6Sn5 into Cu3Sn and the formation of submicron voids at the interface, respectively. These results indicate an excellent thermal reliability of the TLPS Cu–Sn skeleton microstructure.

Development of BiAgX® HT Solder Paste for 200°C Application

2016 ◽  
Vol 2016 (HiTEC) ◽  
pp. 000128-000133 ◽  
Author(s):  
Hongwen Zhang ◽  
Jonathan Minter ◽  
Ning-Cheng Lee
Keyword(s):  
Shear Strength ◽  
Thermal Cycling ◽  
Melting Temperature ◽  
Thermal Aging ◽  
Joint Strength ◽  
Solder Paste ◽  
Thermal Cycling Test ◽  
Cycling Test ◽  
Die Attach ◽  
Board Level

Abstract BiAgX® paste with the remelting temperature around 262°C has been tested and adopted successfully for die attach applications [1–5]. BiAgX® HT pastes with the enhanced remelting temperature above 265°C have been designed for the application of 200°C or even higher. The joint strength has been well maintained for most of the tested pastes after thermal aging @ 200°C for 1000hrs. The thermal cycling test (from −55°C to 200°C) degrades the bond shear strength but some of the tested pastes can still keep the joint strength well above IEC standard (IEC 60749-19) required. The melting temperature and the reliability have been observed to closely associate with the alloying elements Z%wt. The BiAgX® pastes have also been modified for board level assembly application. BiAgX® solder wire is under development too.

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.

scholarly journals Fabrication of Roughened Electrodeposited Copper Coating on Steel for Dissimilar Joining of Steel and Thermoplastic Resin

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 591
Author(s):  
Susumu Arai ◽  
Ryosuke Iwashita ◽  
Masahiro Shimizu ◽  
Junki Inoue ◽  
Masaomi Horita ◽  
...  
Keyword(s):  
Shear Strength ◽  
Thermal Shock ◽  
Bonding Strength ◽  
Steel Substrate ◽  
Copper Film ◽  
Copper Coating ◽  
Thermal Shock Test ◽  
Thermoplastic Resin ◽  
Shock Test ◽  
Lap Shear

Electrodeposition of a roughened copper coating onto steel was carried out to produce a bonding surface for thermoplastic resin (polyphenylenesulfide). The roughened copper film was electrodeposited using a copper sulfate bath containing polyacrylic acid (PAA). Following injection molding of the resin, the bonding strength was evaluated in a tensile lap shear strength test, followed by durability testing at high temperature and humidity (85 ± 2 °C and 85 ± 2% relative humidity, respectively) for 2000 h, and a thermal shock test (−50 °C–150 °C) for 1000 cycles. An analysis of the boundary microstructure showed that the PAA concentration had a large effect on the surface morphology of the copper film. The shear strength of the joint between the coated steel substrate and the resin was more than 40 MPa, and the bonding strength also remained above 40 MPa throughout the durability test. During the thermal shock test, although the bonding strength gradually decreased with increasing number of cycles, it remained at over 20 MPa, even after 1000 cycles. This method achieves not only high initial bonding strength, but also durability for joints between dissimilar materials such as steel and resin.

Preparation and Properties of Silicon Nitride Ceramics by Nitrided Pressureless Sintering (NPS) Process

2006 ◽  
Vol 317-318 ◽  
pp. 125-130 ◽  
Author(s):  
In Sub Han ◽  
Seung Ho Cheon ◽  
Yong Hee Chung ◽  
Doo Won Seo ◽  
Shi Woo Lee ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Silicon Nitride ◽  
Pressureless Sintering ◽  
Thermal Shock Test ◽  
Shock Test ◽  
Low Thermal Expansion ◽  
Metal Contents ◽  
Nitride Ceramics ◽  
Original Laboratory ◽  
Si Addition

Silicon nitride ceramics were prepared by new nitrided pressureless sintering (NPS) process in this study. The microstructures, strengths and thermal properties of the NPS silicon nitride ceramics containing three types of Al2O3 and Y2O3 sintering additives were investigated. Additionally, we have investigated the effect of silicon metal contents changing with 0, 5, 10, 15 and 20 wt% in each composition. The silicon nitride was successfully densified using NPS process, particularly at the starting composition of 5 wt.% Al2O3, 5 wt.% Y2O3, and 5 wt.% Si addition. The maximum flexural strengths and relative densities of these specimens were 500 MPa and 98%, respectively. The flexural strength of sintered specimens after the thermal shock test between 30oC and 1300oC for 20,000 cycles was maintained with the original laboratory strength of 500MPa by low thermal expansion coefficient, 2.9 × 10-6/oC, and high thermal conductivity, 28 W/m⋅oC.

Silver Sintering Paste Rendering Low Porosity Joint for High Power Die Attach Application

2016 ◽  
Vol 2016 (HiTEC) ◽  
pp. 000134-000142 ◽  
Author(s):  
Sihai Chen ◽  
Christine LaBarbera ◽  
Ning-Cheng Lee
Keyword(s):  
Shear Strength ◽  
Thermal Aging ◽  
Processing Condition ◽  
Total Porosity ◽  
Temperature Cycling ◽  
Large Area ◽  
Die Attach ◽  
Aging Test ◽  
Silver Sintering ◽  
Sintered Ag

Abstract Silver joints with ~10% porosity for die-attach have been achieved with specially engineered Ag sintering pastes, through combined pressureless sintering process plus thermal aging. The pastes developed in this work have the following advantages: 1) they can be used under pressure-less processing condition; 2) they are compatible with conventional reflow oven, resulting in a higher through-put as compared to that of stepwise heating oven; 3) they can be used under air reflow condition; 4) a highly reliable joint has been obtained as judged from the shear strength results from thermal aging and temperature cycling tests. The silver sintering pastes are versatile in bonding different metallization surface including Au, Ag and Cu. It can also be used in bonding large area (10mm × 10mm) dies. Shear test results under varied temperatures implied that the maximum service temperature of Ag sintered joints can be as high as 470 – 530 °C, depending on the shear strength pass criteria, and this is more than 250°C higher than that of high-Pb joints. Thermal aging test at 250°C for the joints generated on Ag-die/Au-DBC combination revealed that Ag continuously consolidates in the bulk phase resulting in the formation of larger pores with reduced numbers as compared to that of untreated samples. At the same time, it diffuses to sintered Ag/Au-DBC interface to form a dense Ag layer induced by alloying with Ni(Au) and Cu, which strengthened the bonding. A large bondline thickness is critical for obtaining highly reliable joints. The total porosity of the joint is found slightly decreased during the course of 3200h aging test. Temperature cycling at −55 °C to 200°C shows that the silver joints are stable for at least 1000 cycles.

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.

Degradation Behavior of TiN Coatings with Different Thicknesses after a Pulsed Laser Thermal Shock Test

2013 ◽  
Vol 51 (10) ◽  
pp. 729-734 ◽  
Author(s):  
Seol Jeon ◽  
Youngkue Choi ◽  
Hyun-Gyoo Shin ◽  
Hyun Park ◽  
Heesoo Lee ◽  
...  
Keyword(s):  
Thermal Shock ◽  
Pulsed Laser ◽  
Thermal Shock Test ◽  
Degradation Behavior ◽  
Shock Test ◽  
Tin Coatings
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