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Components and Packaging Technologies, IEEE Transactions on

Issue 1 • Date March 2006

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  • [Front cover]

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  • IEEE Transactions on Components and Packaging Technologies publication information

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  • Table of contents

    Page(s): 1 - 2
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  • Editorial

    Page(s): 3 - 4
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  • Electronic packaging solder joint reliablity assessment with a mechanics-based StrainGage methodology

    Page(s): 5 - 12
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    It is essential to understand solder joint strains to improve package reliability. However, it is often difficult to measure the true solder joint strains directly. Strain gages have been increasingly used by component suppliers and original equipment manufacturers (OEMs) to indicate package mechanical stress levels. One of the most used strain gage locations is on the component side, right next to the package corner. A concern with this location alone is that the strain gages mounted close to the package pick up the local stress concentration near the package edges or corners. In this paper, appropriate strain gage locations are suggested based on mechanics principles and finite element simulation results. An analytical methodology is developed to determine the solder joint deformations from strain gage readings at various locations. This paper also proposes a new strain matching criterion. Most OEMs have been using maximum principal strain to match stress levels and define critical strain limits. A problem with maximum principal strain is that it does not indicate the direction along which the maximum bending occurs. Experimental data demonstrates that the new strain criterion has much better correlation to solder joint failure than maximum principal strains in various bend modes. The conclusions apply to any strain gage mounting metrology on packages attached to printed circuit boards. View full abstract»

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  • Detection of flip chip solder joint cracks using correlation coefficient and auto-comparison analyses of laser ultrasound signals

    Page(s): 13 - 19
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    The detection of cracks in solder joints has been a challenge for the current nondestructive inspection techniques. This paper investigates the capability of a laser ultrasound and vibrometer inspection system to detect thermal cycle induced cracks in flip chip solder joints. Correlation coefficient analysis of ultrasound vibration signals is presented and compared with the previous error ratio method. The correlation coefficient method improves the system's signal-to-noise ratio. Optimum detection locations on the chip surface are investigated and an auto-comparison method is introduced to inspect a chip with fewer detection points and without the dependence on a reference chip. The results show that the system is able to identify thermally cracked solder joints from well-connected joints. When fully developed, the system can be put in-line and serve as a low-cost go/no-go inspection tool to screen out defects in solder joints at an early stage in the manufacturing process. It can also be used to evaluate the quality of many other types of electronic packages and other devices. View full abstract»

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  • General thermal force model with experimental studies

    Page(s): 20 - 29
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    Thermal force has proven to be a useful concept for managing the package-level thermal placement problem. However, the previous thermal force model is based on insulated edge boundary condition; thus it is only suitable to face-cooled packages. A general thermal force model is proposed to extend the applicability of the thermal force to cover general cooling conditions by introducing the concept of the heat transparency of a boundary /spl tau/. By managing /spl tau/, the present method generates a series of thermal-force-equilibrium placements fitting to situations from face-cooled to edge-cooled packages. Experimental results indicate that for generating the reliability-best placements, the best /spl tau/'s are in the range 0 /spl les/ /spl tau/ /spl les/ 0.05 for face-cooled packages and in the range 0.1 /spl les/ /spl tau/ /spl les/ 0.25 for the volumetric-cooled packages. For edge-cooled packages, the best /spl tau/'s are the largest values of /spl tau/ that can achieve convergent thermal-force-equilibrium placements. View full abstract»

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  • Effect of the inlet location on the performance of parallel-channel cold-plate

    Page(s): 30 - 38
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    This study numerically examines the influence of inlet locations on the performance of the Multichannel cold-plates. A total of five inlet configurations (namely I-, Z-, ]-, L-, and /spl Gamma/-arrangement) are investigated in this study. The velocity maldistribution and nonuniformity of temperature field caused by the fluid flow are shown in the simulation. For I-arrangement, higher inlet flow rate of the cold-plate shows more considerable maldistribution, and this maldistribution is decreased when the number of channels of the cold-plate is increased. The Z-arrangement and L-arrangements show a pronounced flow-recirculation that eventually leads to a much larger temperature difference along the surface of the cold-plate. Conversely, there is no flow recirculation in the ]-arrangement and a comparatively uniform flow distribution is seen. For the same average inlet velocity, I-arrangement has the highest pressure drop whereas ]-arrangement shows the lowest pressure drop. The I- and /spl Gamma/-arrangement give the best heat transfer performance due to their impingement configurations whereas the Z-arrangement shows the lowest heat transfer performance for its dramatic flow recirculation and maldistribution. View full abstract»

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  • Thermal analysis for indirect liquid cooled multichip module using computational fluid dynamic simulation and response surface methodology

    Page(s): 39 - 46
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    This paper demonstrates the application of computational fluid dynamic (CFD) simulation and response surface methodology (RSM) in analyzing the thermal performance of a high input/outputs, seven chips, indirect liquid cooled multichip module which will be applied in a kind of supercomputer. A series of similar experiments and corresponding CFD simulations are conducted firstly to evaluate the validity of CFD simulation method and determine the interfacial thermal resistance of thermal grease iteratively, and then a three-dimensional CFD model is established to investigate the heat transfer and fluid flow of the multichip module. Based on the CFD model, the individual effects of factors such as thermal conductivity of the thermal interface material and thermal grease, thickness of the chips, space between chips, solder bump patterns, solder ball patterns, flow velocity and liquid inlet temperature on the thermal performance of the module are studied with one-factor-at-a-time experimentation, and after that, four significant factors are selected to establish a response surface model of the maximum temperature of the module with central composite design based RSM and analysis of variance. View full abstract»

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  • Applying material optimization to fracture mechanics analysis to improve the reliability of the plastic IC package in reflow soldering process

    Page(s): 47 - 53
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    To prevent crack propagation in a plastic small outline J-lead package with a dimpled diepad under an IR soldering process, parametric study and optimization with respect to material properties are done. The main design variables among all material properties are determined from the parametric study. Their optimized values are determined by applying a constraint optimization technique to the IC package. View full abstract»

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  • Development of Au reflection film with high adhesion for high-density optical interconnection between LSI chips

    Page(s): 54 - 59
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    We have developed a new multilayered reflection film structure containing Au for achieving slab waveguide based optical transmission interconnections between large-scale integration chips for next-generation high speed computers. The noble metals, especially Au, have outstanding characteristic as a high reflection film in a slab waveguide. However, when these metals are combined with optically transparent films of a SiO/sub 2/ system, there are severe problems with poor adhesion and poor thermal stability. In this work, we have solved these problems by inserting Cr films above and below the Au film resulting in the development of a new multilayered reflection film structure with superior reflectivity and adhesion characteristics. View full abstract»

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  • Implications of Pb-free microelectronics assembly in aerospace applications

    Page(s): 60 - 70
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    The commercial microelectronics industry is rapidly implementing Pb-free assembly strategies and it should be mostly Pb free within the next decade. This trend is driven by existing and proposed legislation in Europe and in Japan, which has already led a number of firms (including AT&T, IBM, Motorola, Hewlett-Packard, and Intel) to adopt Pb-free implementation programs. This is another sign that the microelectronics industry has become truly global. Following Moore's law, progress in microelectronics is brisk but not uniform: in many cases, commercial industry is ahead of the aerospace sector in technology. Progress by commercial industry, along with cost, drives the use of commercial off-the-shelf parts for military and space applications. We can thus anticipate that the U.S. aerospace industry, which is not subject to foreign legislation, will, at some point, be forced to use Pb-free components and subsystems as part of their standard business practices. In this paper, we provide a snapshot of the commercial industry trends and how they may impact electronics in the aerospace environment. Impacts will be felt in the areas of reliability, assembly methods, cost drivers, supply chain selection, and alternative materials selection. In addition, we look at different strategies for implementation. The questions we address include the following: Should companies immediately embark on a program to convert all of their electronics to Pb free? Should they phase it in instead, and if so, over what time frame? Should companies try to comply with industry Pb-free standards? What requirements should flow down to subcontractors and component suppliers? Legislation is pending in a number of states that may affect these decisions and their timing. The U.S. Environmental Protection Agency, through some university programs, is examining the implementation of Pb free as well. Finally, we present data from a portion of a recent NASA project that focuses on finding suitable alterna- ives to eutectic Sn-Pb solders and solder pastes and on determining suitable processing operations in assembling printed wiring boards. The world is moving toward implementation of environmentally friendly manufacturing techniques. The aerospace industry will be forced to deal with issues related to Pb-free assembly, either because of the progressive scarcity of eutectic Sn-Pb solder or because of legislation. This paper provides insights into some of the key tradeoffs that should be considered. View full abstract»

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  • Investigation of cure kinetics and its effect on adhesion strength of nonconductive adhesives used in flip chip assembly

    Page(s): 71 - 79
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    The reaction kinetics of a commercial fast cure nonconductive adhesive has been systematically investigated using differential scanning calorimetry. Samples were isothermally cured at temperatures from 120 to 160/spl deg/C and dynamically cured at ramp rates between 5 and 20/spl deg/C/min. A good agreement between the autocatalytic kinetic model prediction and experimental results was demonstrated. Deviation occurred at high degrees of cure for curing below 140/spl deg/C due to the occurrence of vitrification. Additionally, by comparing the dynamic cure prediction with the isothermal experiment, good agreements and equivalence were demonstrated. As such, it is possible to predict the isothermal reaction behavior of fast cure materials at high temperature provided that the variation between the actual temperature of the heating system and the setting temperature is not large. Furthermore, the effect of curing process on the adhesion strength has been demonstrated by testing the shear strength of lap joint specimens. It was found that the evolution of adhesion strength was largely dependent on the buildup of mechanical properties during the curing process. At low and medium degrees of cure, cohesive and adhesive failures were respectively observed, while at high degrees of cure, adhesion strength surpassing the shear strength of the solder mask was observed. The sharp increase in adhesion strength was observed to coincide with the gelation point marked by the crossover between the storage and loss modulii, thus suggesting that the contributors to adhesion strength include mechanical interlocking as well as chemical bonding, as evidenced by buildup of storage modulus and mechanical strength of the adhesive. View full abstract»

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  • AEWMA control chart for monitoring variability sources of solder joints quality

    Page(s): 80 - 88
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    A statistical approach for monitoring solder joint quality is presented in this paper. In semiconductor manufacturing, there are often multiple independent root causes (variability sources) that contribute to the overall observed variability in the measured profile. Each variability source may result in a distinct spatial pattern across some of the measured product characteristics. A combinational blind source separation method is proposed to recognize these patterns based on a high-order statistical analysis of inspection data. Visualization of the resulting patterns is shown to help illustrate the nature of their root causes. For the identified individual variability sources, we apply autocorrelation exponentially weighted moving average control charts to monitor the mean shifts by accommodating their autocorrelation and non-Gaussian distributions. The proposed control chart also facilitates online monitoring of solder joint quality by avoiding the sophisticated time-series modeling. View full abstract»

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  • Benchmark heat transfer data for microstructured surfaces for immersion-cooled microelectronics

    Page(s): 89 - 97
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    Pool boiling from a surface featuring micropyramidal reentrant cavities (mouth size 40 /spl mu/m) etched in silicon, bonded to a glass substrate, was studied. All experiments were conducted in the dielectric fluid FC-72 at 1 atm. The heat sink is designed to eliminate spreading through the substrate, and back heat loss. Experimentation showed that the critical heat flux was 12.8 W/cm/sup 2/. A high speed camera (400 frames/s) was used to record and quantify the effect of heat flux on departure diameter and bubble emission frequency. Both departure diameter and frequency showed an increasing trend with heat flux. Comparisons with existing literature are also presented. View full abstract»

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  • Modeling the interdependence of processing and alloy composition on the evolution of microstructure in Sn-based lead-free solders in fine pitch flip chip

    Page(s): 98 - 104
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    Market demands and legislation are driving the electronics-manufacturing sector to move rapidly toward a lead-free future, with Pb-containing electronics products to be banned in Europe after 2006. Although the related scientific research has been undertaken for a decade, a number of technical complications still exist, which are further exacerbated due to the concurrent developments in miniaturization and multifunctionality of microelectronic products. As the packaging joint geometry shrinks toward a microscopic scale, the joint fabrication and reliability become extremely sensitive to the composition and resulting microstructure generated from the chosen joining process and materials. The current level of understanding of such issues is still in its infancy and therefore requires further fundamental study. Thermodynamic modeling is employed in this work as a computational tool to study the sensitivity of processing ranges (e.g., reflow temperature) and the resultant reliability of the microjoints by changing the alloying elements and their content in Sn-based lead-free systems. The work is implemented using the MTDATA program developed by the National Physical Laboratory. With a newly developed database containing critically assessed thermodynamic data appropriate for lead-free solder systems, MTDATA allows the prediction of the liquid-solid transformation and phase formation, for example, as a function of chemical composition and temperature. The paper emphasizes the formation and mass fraction of intermetallic precipitates of different phases in the bulk solder joints and the modeling is also validated through experimental work and recent literature. The results are expected to assist the optimization of processing parameters and cost-effective production using lead-free solders. View full abstract»

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  • Elastic modulus variation due to moisture absorption and permanent changes upon redrying in an epoxy based underfill

    Page(s): 105 - 111
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    In this study, the influence of moisture on the elastic modulus of a no-flow underfill is characterized over a wide range of accelerated testing environments, and the permanent changes are evaluated upon fully redrying. Moisture saturation is reached in all environments prior to testing, thus the inherent wet modulus of the underfill is identified for each respective level of moisture preconditioning. The change in the elastic modulus as a function of moisture concentration is measured, as well as the reversible and irreversible effects from moisture uptake in the underfill upon redrying. Thermal aging from the temperature component of the accelerated testing environment is found to have no effect on the elastic modulus, while the moisture uptake is found to notably decrease the modulus at higher humidity levels. Recovery experiments demonstrate that most of the loss in the elastic modulus from moisture exposure is recoverable, although more irreversible damage did occur at higher humidity levels. Hydrolysis contributed to the irreversible loss in the modulus, while the reversible component is attributed to plasticization of the underfill from moisture uptake. View full abstract»

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  • P-V-T-C equation for epoxy molding compound

    Page(s): 112 - 117
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    The isothermal and isobaric volume shrinkage is measured by a single-plunger-type dilatometer for epoxy molding compound (EMC). This device has been found suitable for measuring volume change of thermosetting materials such as commercial EMC under isothermal and isobaric conditions. Moreover, the degree of cure (conversion) was determined by a differential scanning calorimetry (DSC). Combining volume change and conversion, a mathematic pressure-volume-temperature-cure (P-V-T-C) model is proposed to describe the relationship between volume shrinkage, pressure, temperature and conversion. The P-V-T-C equation can be simply expressed as VS(P,T,C)=F/sub 1/(P,T)/spl middot/C/sup F2(P,T)/. This equation can well describe historical profiles of volume shrinkage under specified isothermal and isobaric states. From the predicted results, volume shrinkage under different pressure levels in any specified temperature can be approximated as and it obeys the principle of linearity. With the help of this model, together with three-dimensional mold filling simulation, engineers will be able to predict warpage and residual stresses for a package after molding. View full abstract»

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  • Solder connections for high frequency applications between flexible and rigid printed circuit boards

    Page(s): 118 - 126
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    This article examines the backplane connector technology for high frequency use and presents a novel concept for shielded enclosures without air vents. The experimental soldering of connections between a flexible printed circuit (flex, for short) and a FR4-board as part of a backplane connector is presented. A very high contact density is reached by soldering vias on the flex to pads on the FR4; this soldering was performed both with ordinary Sn/Pb solder material and as well with lead-free solder alloy. The solder joints were examined using a scanning electron microscope (SEM) and the electrical properties of the flex/solder joint structure were measured. View full abstract»

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  • A thermal, mechanical, and electrical study of voiding in the solder die-attach of power MOSFETs

    Page(s): 127 - 136
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    Large area die-attach defects have been shown to increase the thermal impedance of power semiconductor devices. The changes in thermal performance are simulated and measured in the silicon die using one-, two-, and three-dimensional methods. Experimental measurements for devices with various levels of die-attach void growth are presented. This data is then correlated with finite element thermal modeling to improve the estimate of peak die temperature for voided semiconductor devices. The results present a complete understanding of the heat flow within the voided semiconductor package with an estimate of its impact on performance over its lifetime. View full abstract»

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  • Effect of elastic recovery on the electrical contact resistance in anisotropic conductive adhesive assemblies

    Page(s): 137 - 144
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    The successful design of anisotropic conductive adhesive (ACA) assemblies depends mainly on the accurate prediction of their electrical contact resistance. Among the parameters that influence this resistance, the bonding force used to compress the conductive particles against the conductive tracks during the assembly process is very important. This paper investigates how the contact resistance changes as the bonding force is removed at the end of the assembly process when the epoxy resin used to bond the surfaces has cured. The final contact resistance is determined by examining, through theoretical, experimental and numerical analyzes, the evolution of the residual stress as the elastic recovery of the compressed conductive particles and tracks takes place when the bonding force is removed. An iterative algorithm derived from methods found in fracture mechanics analysis is used to determine the relationship between the contact resistance, the adhesive strength and the stiffness of the cured resin. It is shown that smaller values of adhesive strength yield higher contact resistance values; and similarly, smaller values of modulus of elasticity of the resin lead to higher contact resistance values. View full abstract»

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  • Geometric optimization of a micro heat sink with liquid flow

    Page(s): 145 - 154
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    Over the course of the past decade, a number of investigations have been conducted to better understand the fluid flow and heat transfer in microchannel heat sinks, particularly as it pertains to applications involving the thermal control of electronic devices. In the current investigation, a detailed numerical simulation of the heat transfer occurring in silicon-based microchannel heat sinks has been conducted in order to optimize the geometric structure using a simplified, three-dimensional (3-D) conjugate heat transfer model [two-dimensional (2-D) fluid flow and 3-D heat transfer]. The micro heat sink modeled in this investigation consists of a 10 mm long silicon substrate with rectangular microchannels fabricated with different geometries. The rectangular microchannels had widths ranging from 20 /spl mu/m to 220 /spl mu/m and a depth ranging from 100 /spl mu/m to 400 /spl mu/m. The effect of the microchannel geometry on the temperature distribution in the microchannel heat sink is presented and discussed assuming a constant pumping power. The model was validated by comparing the predicted results with previously published experimental results and theoretical analyses, and indicated that both the physical geometry of the microchannel and the thermophysical properties of the substrate are important parameters in the design and optimization of these microchannel heat sinks. For the silicon-water micro heat sink, the optimal configuration for rectangular channel heat sinks occurred when the number of channels approached 120 channels per centimeter. View full abstract»

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  • Cooling structure for EMC shielded high frequency electronics

    Page(s): 155 - 163
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    Cooling of electronics is normally achieved using air passing through apertures in the enclosure; as a result the shielding effectiveness of the shielded enclosure is reduced. In this paper, the design of a new cooling structure and its evaluation in a wind tunnel is presented. The developed design presented here is a double heat sink in extruded aluminum. Into one side of the heat sink, the printed circuit boards (PCBs) are inserted and enclosed by a complementary shielding surface. The other side of the heat sink is cooled by forced ventilation. The heat transport between these parts is completely inside the same body, without any heat flow interruptions. Tests carried out on a prototype have shown that the performance of the cooling structure is satisfactory for electronic cooling. An additional electromagnetic compatibility (EMC)-test has also elucidated the satisfactory shielding effectiveness of the structure. The cooling structure is scaleable and can accommodate for both future smaller printed circuit boards (PCBs) and those of today. The entire enclosure is furthermore based on near-standard items, which allows it to be inexpensive in high volume production. View full abstract»

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  • A reliability comparison of electroplated and stencil printed flip-chip solder bumps based on UBM related intermetallic compound growth properties

    Page(s): 164 - 172
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    The effects of under bump metallurgy (UBM) microstructures on the intermetallic compound (IMC) growth of electroplated and stencil printed eutectic Sn-Pb solder bumps were investigated. The process parameters and their effects on UBM surface morphology and UBM shear strength were studied. For the electroplating process, the plating current density was the dominant factor to control the Cu UBM microstructure. For the stencil printing process, the zincation process has the most significant effect on the Ni UBM surface roughness and Ni grain sizes. In both processes, the good adhesion of UBM to aluminum can be obtained under suitable UBM processing conditions. Samples with different UBM microstructures were prepared using the two processes. The resulting samples were thermal aged at 85/spl deg/C, 120/spl deg/C, and 150/spl deg/C. It was observed that the Cu UBM surface roughness had larger effect on the IMC growth and solder ball shear strength than the Ni UBM surface roughness. The thickness of Cu/sub 3/Sn and Cu/sub 6/Sn/sub 5/ IMC depended strongly on the UBM microstructure. However, for Ni/Au UBM, no significant dependence was observed. More likely, the thickness of Au-Ni-Sn IMC near the IMC/solder interface was controlled by the amount of gold and the gold diffusion rate in the solder. Shear tests were performed after thermal aging tests and thermal/humidity tests. Different failure modes of different sample groups were analyzed. Electroless Ni UBM has been developed because it is a mask-less, low-cost process compared to electroplated Cu UBM. This study demonstrated that the process control was much easier for Ni UBM due to its lower reactivity with Sn material. These properties made Ni UBM a promising candidate for the lead-free solder applications. View full abstract»

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  • Electrical property improvement of electrically conductive adhesives through in-situ replacement by short-chain difunctional acids

    Page(s): 173 - 178
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    To improve the electrical properties of electrically conductive adhesives (ECAs), short-chain difunctional acids, such as malonic acid (acid M), adipic acid (acid A), and terephthalic acid (acid T) were introduced into a typical isotropic conductive adhesive formulation. By in-situ replacement of the commonly used surfactant-stearic acid in silver(Ag) flakes, such difunctional acids can increase the conductivity of ECAs. With the addition of malonic acid and adipic acid, which only have short chain single-bond hydrocarbon between the dicarboxylic groups, the conductivity of the typical conductive adhesives was improved significantly. Terephthalic acid, however, deteriorates the conductivity due to the rigid aromatic structure in the molecule. Dynamic mechanical analysis and thermomechanical study indicated the improved electrical properties with malonic and adipic acids were achieved without negatively affecting the mechanical and physical properties of ECAs. View full abstract»

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Aims & Scope

IEEE Transactions on Components and Packaging Technologies publishes research and applications articles on the modeling, building blocks, technical infrastructure, and analysis underpinning electronic, photonic, MEMS and sensor packaging.

 

This Transaction ceased production in 2010. The current publication is titled IEEE Transactions on Components, Packaging, and Manufacturing Technology.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Koneru Ramakrishna
Freescale Semiconductor, Inc.