Review of Thermal Packaging Technologies for Automotive Power Electronics for Traction Purposes

The unique chemical and physical properties of nanoparticles make them extremely suitable for designing new and improved sensing devices, especially electrochemical sensors and biosensors. Many kinds of nanoparticles, such as metal, oxide and semiconductor nanoparticles have been used for constructing electrochemical sensors and biosensors, and these nanoparticles play different roles in different sensing systems. The important functions provided by nanoparticles include the immobilization of biomolecules, the catalysis of electrochemical reactions, the enhancement of electron transfer between electrode surfaces and proteins, labeling of biomolecules and even acting as reactant. This minireview addresses recent advances in nanoparticle-based electrochemical sensors and biosensors, and summarizes the main functions of nanoparticles in these sensor systems.

Application of nanoparticles in electrochemical sensors andbiosensors

Fatigue Testing of Copper Nanoparticle-Based Joints and Bonds

Cu nanoparticles (NPs) with two different size distributions were synthesized by a chemical reduction method, which are polydispersed Cu NPs with size in the range of 10 nm to 100 nm and bimodal-sized Cu NPs with large irregular-shaped particles (125 nm) surrounded by small NPs (9 nm). Cu pastes prepared by mixing the Cu NPs with the solvent were used to bond dummy die (i.e., copper plate with silver coating) and bare copper substrate. The results demonstrate that the bimodal-sized Cu NP based paste performs better than the other one in mechanical property of joints. Besides, the shear strength of joints fabricated by such paste can reach 52.6 MPa after pressureless sintering at 280 °C for 10 min in the atmosphere of nitrogen. The copper paste capable of pressureless sintering and making joints with high strength is a promising material for die attachment of IGBT.

Effects of size distributions of copper nanoparticles on the pressureless bonding performance of the copper paste for die attachment

A novel Cu nanoparticle (NP) paste with the capability of pressureless sintering at low temperature in nitrogen is developed using a type of easily synthesized Cu NPs. The feature of bimodal size distribution of Cu NPs can be inherited to the Cu NP paste, which facilitates the formation of dense as-sintered microstructure, mainly consisted of Cu bulks, in sintered joints. The optimization of the sintering process condition has been achieved by using Taguchi method, and so-obtained Cu paste joints show shear strength as high as 65.24 MPa. Moreover, the formulation of the solvent containing ethylene glycol (EG) and glycerol with an optimized weight ratio, which is employed for preparation of the Cu NP paste, has also been demonstrated to be crucial for the formation of Cu bulks in joints and so-induced superior bonding strength. Finally, the results of high temperature storage (HTS) tests of Cu paste joints after aging at 200 °C for 600 h show that there is a slight degradation of bonding strength of joints, mainly due to the generation of voids at the Cu-paste/Cu interface.

A highly reliable die bonding approach for high power devices by low temperature pressureless sintering using a novel Cu nanoparticle paste

A nano-Cu pressureless sinterable paste was developed for joint formation applications. The material was further engineered in both chemistry and process for enhanced oxidation resistance. This oxidation resistance capability allowed the paste exhibited a shelf life of 6 months when stored at -10°C. The paste was insensitive to either sintering atmosphere or surface finish type, and consistently exhibited a joint shear strength around 13 MPa. Nano-Ag pastes were observed to be sensitive to surface finishes, and performed particularly poorly for OSP-OSP system. The shear strength of nano-Cu was sensitive to sintering temperature and time, with shear strength increased from 220°C/15 min, 220°C/30 min, to 240°C/15 min. The joint shear strength deteriorated with increasing TCT (-40°C/150°C) cycle number. After 3000 cycles, the ranking of shear strength can be shown below: Nano-Cu > Ag-N > Ag-H2 > Ag-H1 > Ag-K > Ag-D. The high Pb joint performed the best. The microstructure of Nano-Cu joint formed at 240°C/15 min sintering condition indicated a continuous sintering progress with increasing TCT cycles, with porosity diminishing and smooth area increasing. This strongly suggests that either a higher temperature or a longer time than 240°C/15 min is desired for improved sintering extent

Nano-Cu Sintering Paste for High Power Devices Die Attach Applications

A nano-Cu pressureless sinterable paste was developed for joint formation applications. The material was further engineered in both chemistry and process for enhanced oxidation resistance. This oxidation resistance capability allowed the paste exhibited a shelf life of 6 months when stored at −10°C. The paste was insensitive to either sintering atmosphere or surface finish type, and consistently exhibited a joint shear strength around 13 MPa. Nano-Ag pastes were observed to be sensitive to surface finishes, and performed particularly poorly for OSP-OSP system. The shear strength of nano-Cu was sensitive to sintering temperature and time, with shear strength increased from 220°C/15 min, 220°C/30 min, to 240°C/15 min. The joint shear strength deteriorated with increasing TCT (−40°C/150°C) cycle number. After 3000 cycles, the ranking of shear strength can be shown below: Nano-Cu > Ag-N > Ag-H2 > Ag-H1 > Ag-K > Ag-D. The high Pb joint performed the best. The microstructure of Nano-Cu joint formed at 240°C/15 min sintering condition indicated a continuous sintering progress with increasing TCT cycles, with porosity diminishing and smooth area increasing. This strongly suggests that either a higher temperature or a longer time than 240°C/15 min is desired for improved sintering extent.

Nano-Cu sintering paste for high power devices die attach applications

A nano-Cu pressureless sinterable paste was developed for joint formation applications. The material was further engineered in both chemistry and process for enhanced oxidation resistance. This oxidation resistance capability allowed the paste exhibited a shelf life of 6 months when stored at −10°C. The paste was insensitive to either sintering atmosphere or surface finish type, and consistently exhibited a joint shear strength around 13 MPa. Nano-Ag pastes were observed to be sensitive to surface finishes, and performed particularly poorly for OSP-OSP system. The shear strength of nano-Cu was sensitive to sintering temperature and time, with shear strength increased from 220°C/15 min, 220°C/30 min, to 240°C/15 min. The joint shear strength deteriorated with increasing TCT (− 40°C/150°C) cycle number. After 3000 cycles, the ranking of shear strength can be shown below: Nano-Cu > Ag-N > Ag-H2 > Ag-H1 > Ag-K > Ag-D. The high Pb joint performed the best. The microstructure of Nano-Cu joint formed at 240°C/15 min sintering condition indicated a continuous sintering progress with increasing TCT cycles, with porosity diminishing and smooth area increasing. This strongly suggests that either a higher temperature or a longer time than 240°C/15 min is desired for improved sintering extent.

Min Yao

Papers

Nano-Cu Sintering Paste for High Power Devices Die Attach Applications

Nano-Cu sintering paste for high power devices die attach applications

Nano-Cu sintering paste for high power devices die attach applications