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Showing papers in "IEEE Transactions on Components and Packaging Technologies in 1999"


Journal Article•DOI•
TL;DR: In this paper, an evaluation of environmental impact and reliability when using anisotropically conductive adhesives (ACA) for flip-chip joining in radio base station applications is provided.
Abstract: There is an increasing demand to move the radio base station closer to the antenna for future mobile telecommunication systems. This requires a significant reduction in weight and volume and increased environmental compatibility. This work provides an evaluation of environmental impact and reliability when using anisotropically conductive adhesives (ACA) for flip-chip joining in radio base station applications. Conventional FR-4 substrate has been used to assemble a digital ASIC chip using an anisotropically conductive adhesive and flip-chip technology. The chip has a minimum pitch of 128 /spl mu/m with 7.8 mm in chip 8 and has in total 144 bumps with a bump size of 114/spl times/126 /spl mu/m/sup 2/. Bumping was made using electroless nickel/gold technology. Bonding quality has been characterized by optical and scanning electron microscopy and substrate planarity measurement. The main parameters affecting quality are misalignment and softening of the FR-4 substrate during assembly, leading to high joint resistance. Reliability testing was conducted in the form of a temperature cycling test between -40 and /spl plusmn/125/spl deg/C for 1000 cycles, a 125/spl deg/C aging test for 100 h and a 85/85 humidity test for 500 h. The results show that relatively small resistance changes were observed after the reliability test. The environmental impact evaluation was done in the form of a material content declaration and a life cycle assessment (LCA). By using flip-chip ACA joining technology, the content of environmentally risky materials has been reduced more than ten times, and the use of precious metals has been reduced more than 30 times compared to conventional surface mount technology.

105 citations


Journal Article•DOI•
TL;DR: In this paper, a variety of nozzle configurations were tested to characterize and optimize the performance of confined impinging air jets used in conjunction with a pin-fin heat sink, and the results showed that the heat transfer coefficients and thermal resistance values were reported for the heat sink as a function of Reynolds number, air flow rate, pumping power, and pressure drop.
Abstract: A variety of nozzle configurations were tested to characterize and optimize the performance of confined impinging air jets used in conjunction with a pin-fin heat sink. Four single nozzles of different diameters and two multiple-nozzle arrays were studied at a fixed nozzle-to-target spacing, for different turbulent Reynolds numbers (5000/spl les/Re/spl les/20000). Variations in the output power level of the heat source and nozzle-to-target spacing were found to have only modest effects on heat transfer at a fixed Reynolds number. Enhancement factors were computed for the heat sink relative to a bare surface, and were in the range of 2.8-9.7, with the largest value being obtained for the largest single nozzle (12.7 mm diameter). Average heat transfer coefficients and thermal resistance values are reported for the heat sink as a function of Reynolds number, air flow rate, pumping power, and pressure drop, to aid in optimizing the jet impingement configuration for given design constraints.

98 citations


Journal Article•DOI•
TL;DR: In this paper, the authors studied the properties of a thin layer of organic lubricant on the surface of an Ag flake surface, which is needed for eliminating the Ag particle agglomeration while dispersing the Ag filler into the polymeric resin.
Abstract: Conductive adhesives are composites of polymer matrixes and metal fillers (conductive elements). Silver (Ag) flakes are widely used as fillers for electrically conductive adhesives (ECAs). Generally, there is a thin layer of organic lubricant coated on the commercial Ag flake surface. This lubricant layer is needed for eliminating the Ag particle agglomeration while dispersing the Ag filler into the polymeric resin. Therefore the lubricant influences rheology, conductivity, and other properties of ECA's. The nature of the lubricant on a Ag flake and the interaction between the lubricant and the Ag flake surface were studied by diffuse reflectance infrared spectroscopy (DRIR). Thermal decomposition of the lubricant was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). In addition, the effects of some chemical compounds on lubricant removal and the enhancement of conductivity of the ECA were also investigated. It was found that 1) a chemical bonding was formed on the Ag flake surface between the lubricant and Ag; 2) the short chain acids replaced the long chain lubricants; 3) an ether and a poly(ethylene glycol) enhanced electrical conductivity by partially removing the Ag flake lubricants.

96 citations


Journal Article•DOI•
TL;DR: In this article, solid to liquid phase change materials (PCM's) for passive energy storage during the condition of time varying workloads on portable electronics were investigated, and numerical simulations were performed to study the effect duty cycles and substrate thermal conductivities have on the thermal performance of the electronic wearable computer system.
Abstract: This paper describes the investigation of solid to liquid phase change materials (PCM's) for passive energy storage during the condition of time varying workloads on portable electronics. The model investigated includes a thermal control unit (TCU) embedded in an epoxy polymer. A TCU is an enclosure that contains phase change material (PCM) and a thermal conductivity enhancer, is located near the power source, and acts as an energy storage and heat-spreading module. Physical experiments were carried out to investigate the performance improvements of introducing a TCU into an embedded system and were used to validate the accuracy of the numerical model. Numerical simulations were performed to study the effect duty cycles and substrate thermal conductivities have on the thermal performance of the electronic wearable computer system with passive energy storage. Additionally, the TCU was numerically modeled to determine the influence of boundary conditions on TCU performance. To quantify the improvements of the system, metrics were developed from analyzing the thermal evolution of the TCU parameters, such as temperature fields, temperature bands, PCM characteristics, and power loads. Results indicate that using a TCU for passive energy storage significantly increases the portable electronics system's operational performance. Duty cycles with the same average power over the duration of the cycle do not influence the length of the PCM phase change time, but do impact the mean value of the temperature fluctuation bands.

75 citations


Journal Article•DOI•
TL;DR: In this article, a two-phase model of the combined resin and air is presented, which takes into account geometrical factors such as bumps and die edges, together with boundary conditions in order to track accurately the propagation of the flow fronts.
Abstract: The flow characteristics of a number of underfills were evaluated with quartz dies of different patterns and pitches bonded on different substrate surfaces. Perimeter, mixed array, and full array patterns were tested. Observations on the flow front uniformity, streaking, voiding, and filler segregation were collected, The information was compared with the results predicted by a new simulation code, plastic integrated circuit encapsulation-computer aided design (PLICE-CAD) under DARPA-funded development. The two-phase model of the combined resin and air takes into account geometrical factors such as bumps and die edges, together with boundary conditions in order to track accurately the propagation of the flow fronts, The two-phase flow field is based on the volume-of-fluid (VOF) methodology embedded in a general-purpose three-dimensional (3-D) flow solver.

70 citations


Journal Article•DOI•
TL;DR: In this paper, the authors used the modified J-integral and the stress intensity factor based on linear elastic fracture mechanics to predict the growth of interfacial delamination in integrated circuit (IC) packages.
Abstract: The modified J-integral and the stress intensity factor based on linear elastic fracture mechanics can be applied to predict the growth of interfacial delamination in integrated circuit (IC) packages. One of the key parameters required is the interfacial fracture toughness. This paper describes the measurement of the interfacial fracture toughness as a function of temperature and relative humidity using a three-point bending test. The interfacial fracture toughness was found to decrease with temperature and relative humidity. It is proposed that delaminations propagate from very small voids or defects present at the interface. The effect of the location of these interfacial defects or cracks on delamination was studied. The IC package evaluated in this paper was an 80-pin quad flat package with a 0.2 mm defect or crack at the edge or at the center of the interface. It was found that as the temperature of the package was increased, the stress intensity factor of the edge crack was higher than that of the center crack. However, whether the edge crack will propagate first as temperature is increased depends on the ratio of mode II interface toughness to that of the mode I interface toughness. For the package under investigation, it was established that when this ratio is less than 2.69 the edge crack would propagate first, otherwise the center crack would. For small defects, it was found that the water vapor pressure developed at the interface did not have a significant effect on the value of the crack-tip stress intensity factor.

63 citations


Journal Article•DOI•
TL;DR: In this paper, the microcrystalline and nanocrystalline CuCr alloys prepared by high-energy ball milling and hot pressing were investigated, and the experimental results showed that the nanocrystine Cu-Cr alloy powders are obtained by high energy ball-milling, and milled powders appear flaked or equiaxed morphology with or without liquid medium addition.
Abstract: The microcrystalline and nanocrystalline CuCr alloys prepared by high-energy ball milling and hot pressing were investigated in this paper. The experimental results show that the nanocrystalline Cu-Cr alloy powders are obtained by high energy ball milling, and the milled powders appear flaked or equiaxed morphology with or without liquid medium addition. The grain size of near fully dense alloys consolidated at 850 and 1200 K from milled powders is less than 100 nm and about 2-3 /spl mu/m, respectively. The ability to withstand high voltage of the nanocrystalline CuCr materials in vacuum is much higher than that of microcrystalline materials. The breakdown first takes place on the Cu-rich phase in the microcrystalline CuCr materials. For nanocrystalline CuCr materials, the breakdown exhibits a diffusional feature, in which the arc can move to the whole contact surface in a breakdown.

63 citations


Journal Article•DOI•
TL;DR: These models to estimate the peak and damped resonance noise of the ground and power bounce are developed for both long and short channel devices.
Abstract: Ground bounce estimation is important to determine the impact of simultaneous switching of input/output (I/O) drivers and clock drivers on the performance of application-specific integrated circuits (ASIC's). In this paper, we develop models to estimate the peak and damped resonance noise of the ground and power bounce. These models are developed for both long and short channel devices. Comparison with H-simulation program with integrated circuit emphasis (HSPICE) simulation indicates a good match. These models are simple and suitable for hand calculation.

55 citations


Journal Article•DOI•
TL;DR: In this article, a chemical kinetic model is proposed to explain the joint strength degradation data reported in literature, and the water-stress history along the interface can be modeled as a function dependent principally on water concentration without dependence on position.
Abstract: Mechanical properties of adhesive joints are degraded in the presence of water. The progressive decrease in strength has been attributed to propagation of interfacial crack. Water diffusion and stress distribution within the adhesive joint as a function of time has been modeled using finite elements in this study. The stress history at the interface displayed spatially invariant characteristics similar to that of interfacial water concentration variation as a function of diffusion. The water-stress history along the interface can be modeled as a function dependent principally on water concentration without dependence on position. On this basis, a chemical kinetic model is proposed to explain the joint strength degradation data reported in literature.

49 citations


Journal Article•DOI•
TL;DR: In this paper, a method for remetallizing the bond pads of electronic chips, which are initially metallized with aluminum or aluminum alloy, is presented, which can reduce the cost and complication of the widely accepted flip-chip interconnection technology.
Abstract: A method for remetallizing the bond pads of electronic chips, which are initially metallized with aluminum or aluminum alloy is presented. Application of electroless plating process for the remetallization of aluminum to a solderable gold surface can reduce the cost and complication of the widely accepted flip-chip interconnection technology. We have developed a step by step nickel/gold wafer bumping technique (remetallized bump height is 5.0 /spl mu/m) for the appropriate solder (15.0 /spl mu/m of In:Pb). Variation of roughness of the remetallized surface has been studied carefully. We have completed prototype research studies on test devices and successfully packaged the flip-chip bonded hybrid pair of a CMOS driver chip and a dummy structure of vertical cavity surface emitting laser (VCSEL) array. Cross section of the flip-chip solder joint is studied. Also, adhesion strength of the metal deposit is investigated.

48 citations


Journal Article•DOI•
TL;DR: In this article, the chip on glass (COG) bonding process using anisotropic conductive films (ACF) was investigated by both analytical and numerical means, and the assumptions concerning the thermo-mechanical and rheological properties of the polymer materials involved in the bonding process were characterized for dependence on temperature.
Abstract: The paper reports investigations on the chip on glass (COG) bonding process using anisotropic conductive films (ACF). Experimental methods as well as theoretical analyses, by both analytical and numerical means, are applied. The assumptions concerning the thermo-mechanical and rheological properties of the polymer materials involved in the bonding process are characterized for dependence on temperature. The transient development of the temperature field during the bonding process is studied by finite element (FE) analysis for dependence on the upper and lower chuck temperatures. Analytical techniques of fluid mechanics are used to predict the flow of the conductive particles during bonding, treated as dimensionless points embedded in a viscous matrix. This analytical description allows one to estimate the number of conducting particles on a bump of a chip after bonding. Furthermore, numerical calculations are applied to characterize the influence of viscosity gradients on the particle flow. Finally, nonlinear finite element simulations are used to investigate the stress development and stress relaxation process within the ACF joints.

Journal Article•DOI•
TL;DR: In this paper, the feasibility of single and two-phase micro heat exchangers applied to the cooling of insulated gate bipolar transistor (IGBT) power components is evaluated, and the experimental measurements are compared to the predictions of the thermal and hydraulic performance with water and the inert fluorocarbon liquid (FC72) as coolant fluids.
Abstract: Experiments have been performed to assess the feasibility of single and two-phase micro heat exchangers applied to the cooling of insulated gate bipolar transistor (IGBT) power components. After a brief recall of the principal characteristics of such heat exchangers, prototypes that have been built and tested are described. Then, the experimental measurements are compared to the predictions of the thermal and hydraulic performance with water and the inert fluorocarbon liquid (FC72) as coolant fluids.

Journal Article•DOI•
TL;DR: In this paper, the lateral resolution of broadband transducers commonly used in acoustic microscopy is discussed in the context of selecting optimum transducers to make images for the best possible resolution of defects in plastic encapsulated integrated circuit (IC) packages.
Abstract: The lateral resolution of broadband transducers commonly used in acoustic microscopy is discussed in the context of selecting optimum transducers to make images for the best possible resolution of defects in plastic encapsulated integrated circuit (IC) packages. A predictive model to accurately calculate the effective lateral resolution afforded by a transducer is proposed. The model, which explicitly considers the measured frequency dependent attenuation behavior in water and in encapsulant materials, is a practical tool for the acoustic microscopist interested in selecting a transducer with optimum characteristics for inspecting a particular IC package. Experimental data from plastic quad flat packages (PQFP's) molded with two different encapsulants-Nitto MP8000CH and Sumitomo 6300HJ are presented to demonstrate the validity of the modeling approach. Recommendations for optimum transducer selection are presented based on a parametric study of the effect of various transducer and material parameters on the effective lateral resolution and signal loss.

Journal Article•DOI•
TL;DR: A method to obtain an estimate of the time constant distribution underlying the observed transient, based on an iterative deconvolution that produces an approximation to the time Constant spectrum while preserving a convenient convolution form is presented.
Abstract: The study of the thermal behavior of complex packages such as multichip modules (MCMs) is usually carried out by measuring the so-called thermal impedance response, that is: the transient temperature after a power step. From the analysis of this signal, the thermal frequency response can be estimated, and consequently, compact thermal models may be extracted. We present a method to obtain an estimate of the time constant distribution underlying the observed transient. The method is based on an iterative deconvolution that produces an approximation to the time constant spectrum while preserving a convenient convolution form. This method is applied to the obtained thermal response of a microstructure as analyzed by finite element method as well as to the measured thermal response of a transistor array integrated circuit (IC) in a SMD package.

Journal Article•DOI•
TL;DR: In this paper, four isotropically conducting adhesives were used to form lap joints between copper fingers which had been prepared with four surface metallizations (Cu, Au, Pd, and PdNi).
Abstract: Four isotropically conducting adhesives were used to form lap joints between copper fingers which had been prepared with four surface metallizations (Cu, Au, Pd, and PdNi). A micromechanical tester was used to perform pull and fatigue tests on the 16 adhesive/finish combinations. The micro-ohm resistance change was measured during both the pull and fatigue tests. The similarities and differences between the mechanical strength, fatigue life, and resistance change for the 16 adhesive/finish combinations have been reported, and conclusions were made about relative motion between silver particles, and the fracture interfaces.

Journal Article•DOI•
TL;DR: In this paper, the Fickian model was used to evaluate the equilibrium moisture content in each laminate at various environmental conditions and the moisture content of each laminate was evaluated as a function of electrical capacitance via a capacitance monitoring plate.
Abstract: The electronic industry's most common laminates (FR-4, HTFR-4, PI, CE, and BT) were investigated for their equilibrium levels of moisture and diffusion rates and monitored for their moisture content as a function of electrical capacitance. Isothermal sorption tests were performed on the laminates to find the equilibrium moisture content in each laminate at various environmental conditions. The moisture content of each laminate was evaluated as a function of electrical capacitance via a capacitance monitoring plate attached to each laminate. A model was developed to assess the equilibrium content as a function of both temperature and humidity. Data from the sorption-time experiments was used to evaluate a diffusion coefficient for each laminate. The Fickian model was used to facilitate the evaluation. The results of the laminate moisture content analyses were subsequently applied to a printed wiring board (PWB) with a capacitor plate on each of its laminates. The capacitance method of moisture measurement in PWB shows slower moisture ingress than the theoretical moisture diffusion based on laminate experiments.

Journal Article•DOI•
Myung-Jin Yim1, Woonghwan Ryu1, Young-Doo Jeon1, Jun Ho Lee1, Seungyoung Ahn1, Joungho Kim1, Kyung-Wook Paik1 •
TL;DR: In this paper, anisotropically conductive film (ACF) flip-chip interconnection was investigated using a microwave network analysis and high-frequency measurement of the anisotropic film interconnection using a 1-poly and 3-metal 0.6 /spl mu/m Si process with an inverted embedded microstrip structure.
Abstract: Microwave model and high-frequency measurement of the anisotropically conductive film (ACF) flip-chip interconnection was investigated using a microwave network analysis. The test integrated circuits (ICs) were fabricated using a 1-poly and 3-metal 0.6 /spl mu/m Si process with an inverted embedded microstrip structure. As flip chip bumps, electroless Ni/Au plating was performed on Al input/output (I/O) pads of test IC chips, As an interconnect material, several ACFs were prepared and flip-chip bonded onto the Rogers(R) RO4003 high frequency organic substrate. S-parameters of on-chip and substrate were separately measured in the frequency range of 200 MHz to 20 GHz using a microwave network analyzer HP8510 and cascade probe, and the cascade transmission matrix conversion was performed. The same measurements and conversion were conducted on the test chip mounted substrates at the same frequency range. Then impedance values in flip-chip interconnection were extracted from cascade transmission matrix. The extracted model parameters of the 100 /spl mu/m/spl times/100 /spl mu/m interconnect pad show the resistance increases due to skin effect up to 8 GHz. Above this frequency, conductive loss of epoxy resin also increases. Reactance is dominantly affected by inductance of Ni/Au bumps and also conductive particles in the ACF interconnection over the measured frequency range. The inductance value of ACF flip chip interconnection is below 0.05 nH and the contact resistance is below 0.9 R. In addition, the effects of different ACF conductive particle materials on high frequency electrical behavior in GHz range were also investigated, Different ACF conductive particle materials show difference in the reactance, resistance, and resonance frequency behavior up to 13 GHz. Our results indicate that high frequency electrical performance of ACF combined with electroless Ni/Au bump interconnection is acceptable for use in the high frequency flip chip application up to 13 GHz. Finally, 80-ps rise time digital signal transmission with small dispersion low loss reflection was demonstrated through the flip-chip interconnection with combination of ACF and Ni/Au bump.

Journal Article•DOI•
TL;DR: In this paper, a review of IC technological trends and IC encapsulation materials and processes is presented, and a special focus is placed on the high-performance silicone and epoxy underfills, their chemistries and use as VLSI device encapsulants for single and multichip module applications.
Abstract: The success in consumer electronics in the 1990's will be focused on low-cost and high performance electronics. Recent advances in polymeric materials (plastics) and integrated circuit (IC) encapsulants have made high-reliability very-large-scale integration (VLSI) plastic packaging a reality. High-performance polymeric materials possess excellent electrical and physical properties for IC protection. With their intrinsic low modulus and soft gel-like nature, silicone gels have become very effective encapsulants for larger, high input/output (I/O) (in excess of 10 000), wire-bonded and flip-chip VLSI chips. Furthermore, the recently developed silica-filled epoxies underfills, with the well controlled thermal coefficient of expansion (TCE), have enhanced the flip-chip and chip-on-board, direct chip attach (DCA) encapsulations. Recent studies indicate that adequate IC chip surface protection with high-performance silicone gels and epoxies plastic packages could replace conventional ceramic hermetic packages. This paper will review the IC technological trends, and IC encapsulation materials and processes. Special focus will be placed on the high-performance silicone and epoxy underfills, their chemistries and use as VLSI device encapsulants for single and multichip module applications.

Journal Article•DOI•
TL;DR: In this paper, the effects of the concentration of the selected fluxing agent on the material properties, interconnect integrity and assembly reliability were extensively investigated and an optimum concentration window was obtained and a routine procedure of evaluating fluxing agents was established.
Abstract: As one of the key requirements of the no-flow underfill materials for flip-chip applications, a proper self-fluxing agent must be incorporated in the developed no-flow underfill materials to provide proper fluxing activity during the simultaneous solder reflow and underfill material curing. However, most fluxing agents have some adverse effects on the no-flow underfill material properties and assembly reliability. In this paper, we have extensively investigated the effects of the concentration of the selected fluxing agent on the material properties, interconnect integrity and assembly reliability. Through this work, an optimum concentration window of the fluxing agent is obtained and a routine procedure of evaluating fluxing agents is established.

Journal Article•DOI•
TL;DR: In this article, a constitutive framework proposed for solder alloys has been applied successfully to model the thermo-mechanical properties of the underfill in the HYSOL PP4526 underfill, which can be used for the analysis and design of advanced electronic packages with underfills such as flip-chip packages.
Abstract: The thermo-mechanical testing of HYSOL PP4526 underfill is reported, including the details of sample preparation and test procedures. It is found that the Young's modulus of the underfill depends on both temperature and applied strain rate. The constitutive framework proposed for solder alloys has been applied successfully to model the thermo-mechanical properties of the underfill in this paper. Excellent agreement between model predictions and experimental data is achieved, The test data and calibrated constitutive model can be used for the analysis and design of advanced electronic packages with underfills such as flip-chip packages.

Journal Article•DOI•
TL;DR: In this paper, an attempt was made to experimentally determine the dependence of the fatigue life of two packaging epoxy adhesives on: temperature, peak cycling stress as a fraction of adhesion strength, and cyclic frequency.
Abstract: Adhesives used in electronic applications are subject to high cyclic shear stresses resulting from differential thermal expansion of the bonded materials. In this study, an attempt has been made to experimentally determine the dependence of the fatigue life of two packaging epoxy adhesives on: temperature, peak cycling stress as a fraction of adhesion strength, and cyclic frequency. Both epoxies were used to bond surfaces of aluminum and silicon. Tensile lap-shear specimens were used.

Journal Article•DOI•
TL;DR: In this article, the TCE (thermal coefficient of expansion), T/sub g/ (glass transition temperature), flexural storage modulus, tangent delta, and moisture content of nine different underfill materials from three different vendors are measured.
Abstract: The curing conditions and material properties such as the TCE (thermal coefficient of expansion), T/sub g/ (glass transition temperature), flexural storage modulus, tangent delta, and moisture content of nine different underfill materials from three different vendors are measured. Their flow rate and the effect of moisture content on mechanical (shear) strength in solder bumped flip chips on organic substrate are also determined experimentally. Furthermore, their effects on the electrical performance (voltage) of functional flip chip devices on organic substrate are measured. Finally, a simple methodology is presented for the selection of underfills from the measurement results of these nine different underfill materials.

Journal Article•DOI•
S.K. Tran1, D.L. Questad, Bahgat Sammakia•
TL;DR: In this paper, the authors describe basic investigations into the properties of these underfills and also how these properties related to the overall development process and experiments were performed to determine the effects on adhesion degradation of flip chip assembly processes and materials such as IR reflow profile, flux quantity and residues.
Abstract: Flip chip attach on organic carriers is a novel electronic packaging assembly method which provides advantages of high input/output (I/O) counts, electrical performance and thermal dissipation. In this structure, the flip chip device is attached to organic laminate with predeposited eutectic solder. Mechanical coupling of the chip and the laminate is done via underfill encapsulant materials. As the chip size increases, the thermal mismatch between silicon and its organic carrier becomes greater. Adhesion becomes an important factor since the C4 joints fail quickly if delamination of the underfill from either chip or the solder mask interface occurs. Newly developed underfills have been studied to examine their properties, including interfacial adhesion strength, flow characteristics, void formation and cure kinetics. This paper will describe basic investigations into the properties of these underfills and also how these properties related to the overall development process. In addition, experiments were performed to determine the effects on adhesion degradation of flip chip assembly processes and materials such as IR reflow profile, flux quantity and residues. Surface treatment of both the chip and the laminate prior to encapsulation were studied to enhance underfill adhesion. Accelerated thermal cycling and highly accelerated stress testing (HAST) were conducted to compare various underfill properties and reliability responses.

Journal Article•DOI•
TL;DR: In this paper, the influence of moisture soaking conditions on true adhesion strength measured by a previously developed method was determined, and the predicted interface delamination in a moisture-absorbed package by considering the swelling of the molding compound due to moisture absorption.
Abstract: We have determined the influence of moisture soaking conditions on true adhesion strength measured by our previously developed method. The drop in true adhesion strength of a specimen that absorbed moisture at 50/spl deg/C is about 50% less than that of a specimen at 85/spl deg/C. This result suggests that the true adhesion strength depends on not only the moisture content but also the moisture absorption temperature. Therefore, we think that the general moisture condition (85/spl deg/C/85%) causes more damage to plastic integrated circuit (IC) packages than that of moisture absorption at room temperature. We also evaluated interface delamination in a moisture-absorbed package by considering the swelling of the molding compound due to moisture absorption. The predicted interface delamination agrees well with the experimental data for moisture-soaked packages.

Journal Article•DOI•
TL;DR: In this article, the effect of arc current, silver content, and density on contact erosion and contact resistance under break operation was measured for three types of AgW circuit breaking contacts in air.
Abstract: The effect of arc current, silver content, and density on contact erosion and contact resistance under break operation was measured for three types of AgW circuit breaking contacts in air. The arc current ranged from 2 kA/sub p/ to 22 kA/sub p/ and the percentage of silver in each of the contact materials was 40, 45, and 49% wt. Contact density and erosion measurements showed the closer the contact density was to 100% theoretical density the lower the erosion rate. Erosion rate results showed a gradual increase in the erosion rate over the 5-16 kA/sub p/ current ranges. The increase in erosion rate corresponded to an increase in contact resistance in all three materials. Above this range, the resistance dropped bark down near its original level as current density increased and the erosion rate leveled off. A relationship was established, through measurements of are diameter and surface composition, between arc current density and contact erosion/resistance.

Journal Article•DOI•
TL;DR: In this paper, the behavior of short circuit break arcs ignited between opening contacts is investigated using optical data, where the relative motion of the anode and cathode roots is compared.
Abstract: This paper presents experimental research into the behavior of short circuit break arcs ignited between opening contacts. The investigation is applied to arc chamber geometries commonly used in miniature circuit breakers (MCB). The movement of the anode and cathode roots are individually plotted from optical data, allowing the relative motion to be compared. The effect of a range of MCB configurations on the arc root motion has been investigated. The experiment was configured so that the fixed contact was always the cathode. The results show that the two are roots do not move away from the contact region simultaneously. Often the cathode root moved off the fixed contact and away from the contact region before the anode root commutated from the moving contact. The delay in anode root commutation leads to a delayed cathode root movement. These events are explained in terms of arc root emission processes.

Journal Article•DOI•
TL;DR: The use of the definitions described in this article related to the use of semiconductor parts outside manufacturer-specified temperature ranges represents a consensus among various sectors of the electronics industry as discussed by the authors.
Abstract: The use of the definitions described in this article related to the use of semiconductor parts outside manufacturer-specified temperature range represents a consensus among various sectors of the electronics industry. The use of these terms and definitions will improve the understanding of the issues involved, facilitate communication across the supply chain, and provide legal clarity.

Journal Article•DOI•
Yong-Jun Kim1, Mark G. Allen1•
TL;DR: In this article, two in situ measurement schemes, using micromachined resonant string structures, for the measurement of the polyimide residual stress and polyimides/metal adhesion durability have been developed.
Abstract: Two in situ measurement schemes, using micromachined resonant string structures, for the measurement of the polyimide residual stress and polyimide/metal adhesion durability have been developed. The residual stress of polyimide films, DuPont PI-2555 and PI-2611, have been measured using a bulk micromachined string structure. According to the Rayleigh's method, the resonant frequency of a polyimide string can be related to the film stress. By measuring the resonant frequency of these polyimide strings, the residual stresses have been calculated. The measurement results of various strings have been compared with conventional measurement results, which shows that they are in good agreement. Also, a noble scheme to quantize the adhesion durability between a polyimide film and a metal film has been developed. This scheme is based on a polyimide/metal bimorph string structures, fabricated using a surface micromachining technique, vibrating with an alternating potential. The change of resonance profile of this string structure can be related to the degradation of adhesion strength at the polyimide/metal interface. Various polyimide/gold string structures have been fabricated using a surface micromachining with Cu sacrificial layers, and the resonant qualities have been monitored. Notable changes of resonant Q-factor and resonant frequency, due to the degradation of adhesion between the metal and polyimide, have been observed after 10/sup 8/ cycles (string vibration) for the polyimide/gold bimorph strings. The changes of resonant Q-factor and resonant frequency over a time period (vibration cycles) have been monitored.

Journal Article•DOI•
L. Chane1, A. Torres-Filho, Christopher K. Ober, Shu Yang, Jir-Shyr Chen, R.W. Johnson •
TL;DR: In this paper, the development of a reworkable underfill for flip-chip underfills is described, along with materials selection process, information on the process for rework as well as pertinent reliability data are described.
Abstract: The rework of packages is a standard practice in surface mount technology (SMT) assembly. The reasons for rework include process yields, failed parts, and field returns. The implementation of flipchip has been hindered by the lack of reworkability following underfill cure. Current commercial underfills do not allow for the rework of the flipchip. The development of a reworkable underfill is described in this paper. The materials selection process, information on the process for rework as well as pertinent reliability data are described.

Journal Article•DOI•
D.C. Abbott1•
TL;DR: The structure and its rationale of the palladium/nickel leadframe finish which Texas Instruments introduced in 1989 is reviewed and the reasons for its development, the advantages and features of this lead finish are discussed as mentioned in this paper.
Abstract: The structure (and its rationale) of the palladium/nickel leadframe finish which Texas Instruments introduced in 1989 is reviewed and the reasons for its development, the advantages and features of this lead finish are discussed. Unique implications for the leadframe maker, the assembly test site and for the end user, result from using this finish, some of which were not anticipated at its inception. There are now more than 30 billion devices in the field with palladium/nickel plated leads. A synopsis of the performance of this finish with one of the lead-free pastes in the market is included. There is also a section on the observed shelf life of this finish under Battelle class 2 mixed flowing gas conditions.