Effect of Substrate Preheating Treatment on Thermal Reliability and Micro-Structure of Ag Paste Sintering on Au Surface Finish

In this work, efforts were made to prepare a thermostable die-attach structure which includes stable sintered microporous Ag and multi-layer surface metallization. Silicon carbide particles (SiCp) were added into the Ag sinter joining paste to improve the high-temperature reliability of the sintered Ag joints. The use of SiCp in the bonding structures prevented the morphological evolution of the microporous structure and maintained a stable structure after high temperature storage (HTS) tests, which reduces the risk of void formation and metallization dewetting. In addition to the Ag paste, on the side of direct bonded copper (DBC) substrates, the thermal reliability of various surface metallizations such as Ni, Ti, and Pt were also evaluated by cross-section morphology and on-resistance tests. The results indicated that Ti and Pt diffusion barrier layers played a key role in preventing interfacial degradations between sintered Ag and Cu at high temperatures. At the same time, a Ni barrier layer showed a relatively weak barrier effect due to the generation of a thin Ni oxide layer at the interface with a Ag plating layer. The changes of on-resistance indicated that Pt metallization has relatively better electrical properties compared to that of Ti and Ni. Ag metallization, which lacks barrier capability, showed severe growth in an oxide layer between Ag and Cu, however, the on-resistance showed fewer changes.

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A Novel Approach to Model the Lubrication and Friction between the Twin-Land Oil Control Ring and Liner with Consideration of Micro Structure of the Liner Surface Finish in Internal Combustion Engines

10.4271/2008-01-1613 ◽

2008 ◽

Cited By ~ 11

Author(s):

Haijie Chen ◽

Yong Li ◽

Tian Tian

Keyword(s):

Surface Finish ◽

Internal Combustion Engines ◽

Internal Combustion ◽

Combustion Engines ◽

Micro Structure ◽

Novel Approach ◽

Liner Surface

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Microstructure and Luminance Properties of Integrated Translucent Alumina Tube Used in Metal Halide Lamps

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.177.272 ◽

2010 ◽

Vol 177 ◽

pp. 272-276

Author(s):

Liu Feng ◽

Zhi Wei Chen ◽

Jin Ye Niu

Keyword(s):

Grain Size ◽

Surface Finish ◽

Sintering Temperature ◽

Metal Halide ◽

Alumina Tube ◽

Sintering Process ◽

Micro Structure ◽

Average Grain Size ◽

Gelcasting Process ◽

Metal Halide Lamps

The integrated translucent alumina tube used in metal halide lamps have been fabricated by gelcasting process. The influence of sintering process, various sintering fluxes on the micro- structure was discussed. Furthermore, the relation between the luminance and the microstructure was also investigated. The results reveal that when the sintering temperature is 1750°C, the holding time is 6h, the compact product whose average grain size is about 20μm could be obtained; the triple dopant combinations of MgO, Y2O3, La2O3 can promote sintering and improve the microstructure more than double, single dopants and the contents of sintering flux are 99.6wt%Al2O3, 0.2wt%MgO, 0.1wt.%Y2O3 and 0.1wt.%La2O3 respectively; The transmittance increases with the pore decreaseing, the grain size enlarging and the degree of the surface finish improving, the average in line transmittance is about 40%.

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High Thermal Stability of SiC Packaging with Sintered Ag Paste Die-attach combined with Imide-based Molding

International Symposium on Microelectronics ◽

10.4071/isom-2015-wp15 ◽

2015 ◽

Vol 2015 (1) ◽

pp. 000349-000352 ◽

Cited By ~ 1

Author(s):

Shijo Nagao ◽

Takuo Sugioka ◽

Satoshi Ogawa ◽

Teruhisa Fujibayashi ◽

Zhang Hao ◽

...

Keyword(s):

Lead Frame ◽

Thermal Cycles ◽

Thermal Reliability ◽

Molding Process ◽

Sem Images ◽

Transfer Molding ◽

Die Attach ◽

Ag Paste ◽

Thermosetting Composite ◽

Sintered Ag

We report that ultra-high thermal reliability can be achieved by combining Ag paste sintering die-attach and injection transfer molding with imide-based mold composite. Test specimens of SiC SBD in TO247 discrete-package are prepared; SiC dies bonded on Cu lead frame, Al ribbon wiring from electrode of SiC Schottky barrier diode (SBD) chip to the Cu leads, and injection transfer molding process. The hybrid nano+micro flake Ag paste realizes a low temperature bond process of 250°C in air, die-shear stress recorded 23 MPa without intensive pressure. The thermo-mechanical parameters like glass transition temperature, Young's modulus and CTE of the thermosetting composite are carefully tuned for both the manufacturing process targeting the device operating temperature of 250°C. The test pieces are tested by harsh thermal cycling between −50°C to 250°C, and compared with the other specimens made with usual Pb-5Sn soldering die-attach with the same molding composite. Interface failures are investigated by scanning acoustic tomography (SAT), and the electric properties of SBD are checked by I-V measurements. The sintered Ag die-attach survived over 500 cycles without any failures around the interfaces of SiC die, Cu lead-frame, and mold materials, and no obvious change is found in electronic properties. However, Pb-Sn die-attach joints are gradually damaged with increasing thermal cycles causing degraded I-V property. The SEM images indicate the microstucture of sintered Ag layer is unchanged after the thermal cycles, because of the impregnated imid-matrix into the porous Ag. Our results demonstrate that the combination of Ag sinter paste die-attach and imide-based thermosetting composite can be a massproduction-ready packaging technology to realize the high operation temperature of post-silicon power devices.

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Small Angle Electron Scattering From Vacuum Condensed Metallic Films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100101657 ◽

1968 ◽

Vol 26 ◽

pp. 380-381

Author(s):

J. Silcox ◽

R. H. Wade

Keyword(s):

Electron Scattering ◽

Small Angle ◽

Ring Structure ◽

Two Dimensional ◽

Metallic Films ◽

Micro Structure ◽

Angle Scattering ◽

The Fourier Transform ◽

Source Of Information ◽

Kinematical Theory

Recent work has drawn attention to the possibilities that small angle electron scattering offers as a source of information about the micro-structure of vacuum condensed films. In particular, this serves as a good detector of discontinuities within the films. A review of a kinematical theory describing the small angle scattering from a thin film composed of discrete particles packed close together will be presented. Such a model could be represented by a set of cylinders packed side by side in a two dimensional fluid-like array, the axis of the cylinders being normal to the film and the length of the cylinders becoming the thickness of the film. The Fourier transform of such an array can be regarded as a ring structure around the central beam in the plane of the film with the usual thickness transform in a direction normal to the film. The intensity profile across the ring structure is related to the radial distribution function of the spacing between cylinders.

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Characterization of machined polystyrene foam

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010015383x ◽

1989 ◽

Vol 47 ◽

pp. 372-373

Author(s):

C. W. Price ◽

E. F. Lindsey ◽

R. M. Franks ◽

M. A. Lane

Keyword(s):

Surface Finish ◽

Cell Walls ◽

Surface Structures ◽

Efficient Technique ◽

Low Density ◽

Polystyrene Foam ◽

Planar Surfaces ◽

Machining Characteristics

Diamond-point turning is an efficient technique for machining low-density polystyrene foam, and the surface finish can be substantially improved by grinding. However, both diamond-point turning and grinding tend to tear and fracture cell walls and leave asperities formed by agglomerations of fragmented cell walls. Vibratoming is proving to be an excellent technique to form planar surfaces in polystyrene, and the machining characteristics of vibratoming and diamond-point turning are compared.Our work has demonstrated that proper evaluation of surface structures in low density polystyrene foam requires stereoscopic examinations; tilts of + and − 3 1/2 degrees were used for the stereo pairs. Coating does not seriously distort low-density polystyrene foam. Therefore, the specimens were gold-palladium coated and examined in a Hitachi S-800 FESEM at 5 kV.

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