Bond Layer Research Articles

Thermo-Mechanical Stress Analysis in Electronic Packaging with Continuous and Partial Bond Layer

Interfacial stress due to thermal mismatch in layered structure has been considered as one of the major causes of mechanical failure in electronic packaging. The mismatch due to the differences in coefficient of thermal expansion (CTE) of the materials in multi-layered structure may induce severe stress concentration to the electronic composites namely interfacial delamination and die cracking. Therefore, the studies and evaluation of interfacial stress in electronic packaging become significantly important for optimum design and failure prediction of the electronic devices. The thermal mismatch shear stress for bi-layered assembly can be analyzed by using the mathematical models based on beam theory. In this study, Finite Element Method (FEM) simulation was performed to an electronic package by using ANSYS. The shear stress growth behavior at the interface of the bonded section was studied with the considerations of continuous and partial bond layers in the interfaces. Based on the analysis, it can be observed that the partial bond layer with small center distances can be simplified as a continuous bond layer for bi-layered shearing stress model analysis.

A continuum based modelling approach for adhesively bonded piezo-transducers for EMI technique

In the electro-mechanical impedance (EMI) technique, which is based on induced strain actuation through piezoelectric ceramic (PZT) patch, the knowledge of shear stress distribution in the adhesive bond layer between the patch and the host structure is very pertinent for reliable health monitoring of structures. The analytical derivation of continuum based shear lag model covered in this paper aims to provide an improved and more accurate model for shear force interaction between the host structure and the PZT patch (assumed square for simplicity) through the adhesive bond layer, taking care of all the piezo, structural and adhesive effects rigorously and simultaneously. Further, it eliminates the hassle of determining the equivalent impedance of the structure and the actuator separately, as required in the previous models, which was approximate in nature. The results are compared with the previous models to highlight the higher accuracy of the new approach. Based on the new model, a continuum based interaction term has been derived for quantification of the shear lag and inertia effects.

Corrosion mechanism of an Al–BN abradable seal coating system in chloride solution

The corrosion mechanism of an Aluminum–Boron Nitride (Al–BN) abradable coating system (with NiAl bond layer and 0Cr17Ni4Cu4Nb substrate) in chloride solution has been investigated by potentiodynamic polarization and volumetric tests. Galvanic interaction of the coating system during corrosion has been confirmed. Upon coupling, the Al–BN layer assumes anodic character, while the bond NiAl and substrate act as cathodes. Spontaneous pitting is aroused on the Al matrix of the Al–BN layer due to the galvanic interaction. The Negative difference effect (NDE) of the Al–BN has been discussed.

Performance of Solder Bond on Thermal Mismatch Stresses in Electronic Packaging Assembly

Thermo-mechanical stresses have been considered one of the major concerns in electronic Packaging assembly structural failure. The interfacial stresses are often caused by the thermal mismatch stresses induced by the coefficient of thermal expansion (CTE) difference between materials, typically during the high temperature change in the bonding process. This research work examined the effect of bond layer on thermal mismatch interfacial stresses in a bi-layered assembly. The paper verified the existing thermal mismatch solder bonded bi-layered analytical model using finite element method (FEM) simulation. The parametric studies were carried out on the effect of change of bond layer properties in order to provide useful references for interfacial stress evaluation and the electronic packaging assembly design. These parameters included CTE, temperature, thickness, and stiffness (compliant and stiff bond) of the bond layer. The recent development on lead free bonding material was being reviewed and found to have enormous potential and key role to address the future electronic packaging assembly reliability.

Thermal and microwave characterization of GaAs to Si metal-bonded structures

Isothermal solidification metal waferbonding is well suited to heterogeneously integrate high-speed/high-power density RF and microwave devices with standard CMOS technology. It is capable of forming efficient electrical and thermal interconnects as well as bonded-microstrip waveguide structures. Accurate means of characterizing the electrical, thermal, and microwave properties of these structures are necessary to enable heterogeneous monolithic microwave integrated circuits (HMMICs). This article describes a bond layer thermal conductivity measurement method, a bond-metal microstrip microwave waveguide characterization method, and the fabrication method developed to support the measurement structures. As a result, an In-Pd bond alloy thermal conductivity of 2.51 W/(m K) was measured for GaAs devices bonded to Si. Also, an optimized bonded-microstrip waveguide was simulated based upon measured microwave results of the measurement structure, projecting a 0.56 dB/mm loss, a microwave index of 2.91, and a characteristic impedance of 41.3+6i Ω at 15 GHz, thus advocating this approach as a means of realizing high power HMMICs.

The effect of bond coat composition on oxidation behavior of basalt base glass and glass–ceramics

In the current study, the effect of bond coat composition and single versus double layers on the interfacial properties of basalt glass-based coatings were investigated. Two bond coats, Ni-5wt.% Al (METCO 450 NS) and NiCr-6wt.% Al (Metco 443 NS) were atmospheric plasma sprayed (APS) onto a commercial AISI 1040 steel substrate. These bond coating powders were used to observe the effect of a bond layer and multiple bond layers on certain mechanical properties, bonding strength and oxidation behaviour. Basalt was melted in a platinum crucible at 1500°C for 1h and cast into water. Basalt glass granules were ground and employed as a coating powder. After the APS process, amorphous coating layers were transformed to crystalline glass–ceramic with a heat treatment process. X-ray diffraction analysis (XRD) was used for glass–ceramic transformation and phase analysis. Scanning electron microscopy (SEM) examinations revealed that there is a uniform coating layer at the macroscopic scale. Cohesive bonding is dominant for both single and double bond-layered samples. It has been observed that the percentage of cohesive strength was approximately three to five times higher than that of the adhesion strength.

FILM THICKNESS INFLUENCES ON THE THERMOELECTRIC PROPERTIES OF NiCr/NiSi THIN FILM THERMOCOUPLES

NiCr / NiSi thin film thermocouples (TFTCs) with a multi-layer structure were fabricated on Ni -based superalloy substrates (95 mm × 35 mm × 2 mm) by magnetron sputtering and electron beam evaporation. The five-layer structure is composed of NiCrAlY buffer layer (2 μm), thermally grown Al 2 O 3 bond layer (200 nm), Al 2 O 3 insulating layer (10 μm), NiCr / NiSi TFTCs (1 μm), and Al 2 O 3 protective layer (500 nm). Influences of thermocouple layer thickness on thermoelectric properties were investigated. Seebeck coefficient of the samples with the increase in thermocouple layer thickness from 0.5 μm to 1 μm increased from 27.8 μV/°C to 33.8 μV/°C, but exhibited almost no change with further increase in thermocouple layer thickness from 1 μm to 2 μm. Dependence on temperature of the thermal electromotive force of the samples almost followed standard thermocouple characteristic curves when the thickness of the thermocouple layer was 1 μm and 2 μm. Sensitive coefficient K of the samples increased greatly with the increase in thickness of the thermocouple layer from 0.5 μm to 1 μm, but decreased insignificantly with the increase in thermocouple layer thickness from 1 μm to 2 μm, and continuously decreased with the increase in temperature. The sensitive coefficient and the stability of NiCr / NiSi TFTCs were both improved after annealing at 600°C.

Effects of Coating on Surface Recrystallization of DD6 Single Crystal Blades

The fully heat-treated DD6 single crystal turbine blades were treated in three ways: (1) surface grinding, without coating; (2) firstly surface grinding, then surface coated with HY3(NiCrAlY) anti-oxidation coating; (3) after surface grinding, coated surface with the bond layer of NiCrAlY and top layer of YSZ(Y2O3 stabilize ZrO2) for the double-layer thermal barrier coatings. All these three experimental blades were treated with vacuum heat-treatment at 1120°C for 4h. The effects of coating on surface recrystallization of single-crystal blades have been investigated. The results indicate that: just with surface polishing blade generated a 6~9μm thick cellular recrystallization zone on the surface. The γ' presented coarse morphology and distributed discretely within cellular, and the γ' growth direction was perpendicular to the cellular interface; blade surface coated with anti-oxidation coating after polishing formed a 3~6μm thick cellular recrystallization zone in the matrix interface. But the grain boundary was fuzzy and recrystallization morphology was incomplete; the matrix interface morphology of blade coated with thermal barrier coatings after polishing changed insignificantly, but some local cellular recrystallization was found. The results indicate that the coating changes the cellular recrystallization morphology of the original matrix of the blade, which can effectively reduce the occurrence degree of recrystallization.

接着接合を併用した重ねすみ肉溶接継手の静的引張強度特性

A series of tensile tests were carried out on fillet welded lap joints assisted with bonding for investigating the static tensile strength characteristics of the joints from the viewpoints of stress reduction effect around the welded part due to bonding. It was confirmed that the mechanical properties of epoxy resin bonding used in this study were not deteriorated by heating less than 150 degrees Celsius. When the fillet welded lap joints with bonding were assembled, the bond layer in 20 mm from the weld toe was subjected to heating over 150 degrees Celsius. In other words, the mechanical properties in that region were deteriorated. The strengths of elastic limit of specimens with welding and bonding were higher than those of specimens with only welding by from 60 to 100 MPa. The ultimate tensile strengths of them were almost the same because they were broken at the base plate. The strains around the weld toe and the root of specimens with welding and bonding were smaller than those of specimens with welding by around 13 % in elastic region. The strengths of specimens with only bonding were 170 MPa, which could be explained by a theory of elastic stress distribution. Even if the bond layer in 20 mm from weld toe of the specimens with welding and bonding was thermally damaged, the possibility was confirmed that the residual bond layer had around 100 MPa in strength. It could be concluded that the strength of the residual bonding assisted to decrease the stress around the welded part of the specimens with welding and bonding.

Characterization of nickel graphite sealing coatings in the system with the nickel-aluminum bonding coating

This study shows the mechanical and structural characteristics of the Ni - graphite sealing and the effect of its use in the low and high pressure compressor parts in a TV2-117A turbojet engine. The coatings were deposited through the atmospheric plasma spray (APS) process. The sealing materials were substituted on the compressor working ring, compressor focusing devices and the compressor front body in a TV2-117A turbojet engine to ensure a maximum air flow in a temperature range from 100 to 125°C through the compressor at a pressure of 7 bars. Soft seals are formed as double systems consisting of a lower bond layer based on the NiAl coating and upper sealing layers of coatings based on Ni - 25% graphite and Ni - 15% graphite. The microstructure of the layers was examined using the light microscope. The morphology of Ni - graphite powder particles and the fracture morphology of the coatings were investigated using a Scanning Electron Microscope (SEM). The microstructural analysis of the deposited layers was performed according to the Pratt-Whitney standard. The mechanical properties of the coatings were assessed by testing the microhardness of the bond layers using the HV0.3 method and by testing the macrohardness of the sealing layers using the HR15y method. The strength of the bonds of coating double systems was tested using the tensile testing. The compressor part sealing effect was tested within the TV2-117A engine.

Thermally Stable Bonding of SiC Devices with Ceramic Substrates: Transient Liquid Phase Sintering Using Cu/Sn Powders

A high–temperature–resistant bond withstanding up to 415°C for SiC power devices is realized at 260°C with a Cu/Sn powder paste and an electroless nickel plated Si3N4/Cu circuit substrate. The bond was formed by using transient liquid phase sintering (TLPS). The bond strength tested at 300°C increases with increasing aging time at 300°C, from the original 40 MPa to 50 MPa after aging at 300°C for 200 h. This is attributed to phase transformation from Cu6Sn5 formed during TLPS to Cu3Sn in the bond during aging. We observed an η–(Cu,Ni)6.26Sn5 phase at the interface between the TLPS Cu–Sn bond and Ni(P) layer. The interface between the TLPS Cu–Sn bond and Si3N4/Cu/Ni(P)/Ag substrate exhibits very high stability, characterized by a very slow Ni(P) layer consumption rate and Ni3P growth rate. The TLPS Cu-Sn bond on a 5 μm-thick electroless plated nickel layer is expected to have a life time beyond 105 h during storage at 300°C.

1P3-4 Analysis of the Effect of Non-piezoelectric Bonding Layer between Electrodes on PVDF Transducer Performance(Poster Session)

1P3-4 Analysis of the Effect of Non-piezoelectric Bonding Layer between Electrodes on PVDF Transducer Performance(Poster Session)

Structural behavior evaluation of T-joints of the composite bogie frame under bending

This study evaluates the failure strength and failure modes of two types of T-joint used in a composite bogie frame under a bending load. The average failure load and displacement of the adhesive-only joint were 4.1 kN and 0.99 mm. The cracks propagated through the bond layer and followed a mode I propagation mode. In contrast, the joint with the adhesive bonding and skin had an average failure load of 68 kN and a displacement of 8.1 mm. It also showed a mode I propagation trend. The strain distribution for the whole region of the two joints was evaluated with FE analysis. A comparison of experiment results and the FE analysis results revealed that the error was in range of 5.33%–42.6% for the adhesive-only joint and 1.07% and 17.3% for the joint with the adhesive bonding and skin. The maximum stress concentration locations showed good agreement between the experiment and FE analysis.

A durability study of externally bonded FRP-concrete beams via full-field infrared thermography (IRT) and quasi-static shear test

Durability of 36nos. externally-bonded CFRP-concrete beams was studied by monitoring the intermediate cracking (IC) processes using infrared thermography (IRT) and quasi-static direct shear test. Specimens were exposed to three elevated water temperatures (25°C, 40°C and 60°C) for 5, 15 and 30weeks. In addition to the measurement of the properties at ultimate state, this work attempts to characterize the intermediate states of the intact, softened and ruptured part during the IC debonding process. The results show that the adhesive bond layers of the 40°C and 60°C specimens were ruptured and softened at a force level much lower than that for the 25°C and control specimens. This is explained by the exposure condition that the water temperature exceeded the heat distortion temperature of the adhesive layer, which accelerated the bond deterioration of the composites.

The influence of the energy density and other clinical parameters on bond strength of Er:YAG-conditioned dentin compared to conventional dentin adhesion

The aim of this in vitro study was to optimise clinical parameters and the energy density of Er:YAG laser-conditioned dentin for class V fillings. Shear tests in three test series were conducted with 24 freshly extracted human third molars as samples for each series. For every sample, two orofacial and two approximal dentin surfaces were prepared. The study design included different laser energies, a thin vs a thick bond layer, the influence of adhesives as well as one-time- vs two-time treatment. The best results with Er:YAG-conditioned dentin were obtained with fluences just above the ablation threshold (5.3 J/cm(2)) in combination with a self-etch adhesive, a thin bond layer and when bond and composite were two-time cured. Dentin conditioned this way reached an averaged bond strength of 23.32 MPa (SD 5.3) and 24.37 MPa (SD 6.06) for two independent test surfaces while showing no statistical significance to conventional dentin adhesion and two-time treatment with averaged bond strength of 24.93 MPa (SD 11.51). Significant reduction of bond strength with Er:YAG-conditioned dentin was obtained when using either a thick bond layer, twice the laser energy (fluence 10.6 J/cm(2)) or with no dentin adhesive. The discussion showed clearly that in altered (sclerotic) dentin, e.g. for class V fillings of elderly patients, bond strengths in conventional dentin adhesion are constantly reduced due to the change of the responsibles, bond giving dentin structures, whereas for Er:YAG-conditioned dentin, the only way to get an optimal microretentive bond pattern is a laser fluence just above the ablation threshold of sclerotic dentin.

Preface

Abstract With the ever increasing axle load and traffic volume, premature failure of Heavy Duty Asphalt Pavement and Bridge Deck Pavement has been a major problem facing the academia and industrial community for years. In responding to the challenge, the ISAP (The International Society for Asphalt Pavements) Third International Symposium on Heavy Duty Asphalt Pavement and Bridge Deck Pavement was held in May 23–25, 2012, Nanjing, China. Experts in both academia and industry and from around the world shared their ideas and discussed state-of-the-art advancement in cutting-edge scientific research in related areas. This special issue on “Heavy Duty Asphalt Pavements and Bridge Deck Pavement” is a collection of 30 papers selected from over 190 papers through a rigorous peer review process in accordance with the academic standards set up by the Journal of Testing and Evaluation. The selected papers cover a broad spectrum of topics from materials to pavement structures, construction, maintenance, and management related to heavy duty pavement and bridge deck pavement. Fundamentally, these topics can be roughly divided into four groups. The first group deals with pavement materials such as design and performance of asphalt mixtures, test methods and characterization of mixtures, innovations in modified asphalt, and recycling. The second group focuses on pavement structures, including axle load investigation and axle load spectrum, semi-rigid base pavement structure, flexible pavement, composite pavement, pavement structure design, and subgrade structure. The focus of the third group is on bridge deck pavement, including mechanics analysis, concrete deck pavement, steel deck pavement, and waterproof layer and bond layer. The last group deals with construction, maintenance and management, including construction technique and equipment, preventive maintenance for heavy traffic roads, policies and measures for overweight control, life cycle assessments, and traffic planning for heavy traffic roads. The guest editors of this special issue are confi dent that this collection of highly relevant and impactful contributions will be of interest to many diverse audiences, be they in academia or industry. We are grateful to have achieved such a high quality collection of papers and would like to thank the authors for their contributions. We would also like to thank the chief editor and staff in the editorial office of the Journal of Testing and Evaluation for their assistance during the course of organizing this special issue. Furthermore, we would like to thank the anonymous reviewers for their rigorous review. We would like to encourage the whole field to continue the progress in all fronts related to heavy duty pavement and bridge deck pavement.

A refined shear lag model for adhesively bonded piezo-impedance transducers

The performance (sensing/actuating) of a piezotransducer highly depends upon the ability of the bond layer to transfer the stress and strain (through shear lag mechanism) between the transducer and the structure. Therefore, the coupled electromechanical response of the piezotransducer should consider the effect of dynamic behaviour, geometry and composition of the adhesive layer used to bond the transducer patch on the structure. This article presents a new refined analytical model for inclusion of the shear lag effect in modelling of adhesively bonded piezoelectric ceramic (lead zirconate titanate) patches for consideration in the electromechanical impedance technique. The previous models neglected the inertial term in shear lag formulations for simplicity. The present refined model, on the other hand, considers the inertial and the shear lag effects simultaneously, and is therefore more rigorous and complete. In this article, the formulations are first derived for one-dimensional case, and then extended to two-dimensional lead zirconate titanate–structure interaction. The overall results are found to be in better proximity to experimental observations. The refined formulations are employed for a detailed stress analysis of the bond layer. The article concludes with a parametric study on the influence of various sensor parameters on the electromechanical impedance signatures.

Fundamental Study on Setting of Diamond Abrasive Grains Using Electrostatic Force for Single-Layered Metal Bond Wheel

Single-layered metal bond diamond wheels are useful to high efficient grinding of difficult-to-grind materials because of the high gripping force of abrasive grains and the controllable grain density. In this paper, fundamental information are obtained for an application of electrostatic force to setting of diamond grains into pasted metal bond slurry layer on wheel surface, investigating experimentally jumping phenomenon of diamond grains in an electrostatic field between a electrode plate and metal bond slurry layer. The SD grains and the SDC grains coated with Ti are selected. SDC grains jump into a metal bond layer as quick as making an electrostatic field, however SD grains jump with short time lags. The setting rate of SDC grains is larger than that of SD grains, and setting position accuracy of SDC grain array is better than SD grain array. The possibility of setting abrasive grains into single-layered metal bond diamond wheel surface using electrostatic force is obtained and SDC grains are suitable to the proposed abrasive setting method.

Electroless Contact Study on CdTe Nuclear Detectors: New Results and Element Deposition

Electroless deposited contacts are frequently used for II–VI semiconductor materials and particularly on CdTe/CdZnTe. This chemical deposition method creates a stronger chemical bond and few nested interfacial layers between the contact and the semiconductor when compared to physical deposition methods such as sputtering or evaporation. This method also forms a moderate quasi-ohmic contact which eliminates the spectral degradation problem caused by the polarization effect.

Fabrication of thermal barrier coatings onto polyimide matrix composites via air plasma spray process

Thermal barrier coatings were fabricated on polyimide matrix composites via air plasma spray process. The phase structures and microstructural evolution of the coatings before and after testing were characterized by powder X-ray diffraction and scanning electron microscopy. During thermal shock test at 400°C, thermal shock lifetime of the coating systems increased with the decrease of thickness of Al layer as well as the increase in that of YSZ layer. The coating system consisted of 30μm Al bond layer and 130μm YSZ top layer exhibited the best thermal shock resistance. Meanwhile, owing to the protection of the coating system, the weight loss of the sample decreased from 7.05% to 1.90%, while the corresponding mass ablation rate reduced from 0.48mgs−1 to 0.21mgs−1. Failure mechanism of the coatings was mainly ascribable to the residual stress during deposition, oxidation of substrate and thermal stress induced by mismatch in thermal expansion.