Showing papers in "IEEE Transactions on Components, Hybrids, and Manufacturing Technology in 1978"

Enhancing Ultrasonic Bond Development

Abstract: To enhance ultrasonic bond development, an improved understanding is needed of the processes taking place at the bond interface. This work is designed to determine the role that bonding parameters play in contributing to bond development. Of particular concern are the effects created by the machine variables, i.e., load, power, and time. Silicon was selected as a bond surface for aluminum wire bonds. The brittle nature of silicon provides a permanent record of the bonding history. With both the crystal orientation and defects of the silicon well characterized prior to bonding, features such as the location of residual bonding strains in the silicon were determined. The pattern of partially bonded material exposed by peeling underdeveloped bonds simulates a torus (or doughnut) with an unbonded central region. Features of aluminum wire bonds to aluminum, glass, beryllium, and silicon were compared to show that a common mechanism exists independent of the bond surface material. The ability to bond to silicon varies with wire composition. For example, both Al-0.5% Mg and pure Al wires bond readily, while Al-l% Si wire does not. Two modes of material flow characterize interfacial behavior. Ultrasonic energy promotes a material softening which, in conjunction with the applied load, results in a gross flow to expose fresh material for bonding. In the second stage of material flow, a wave form is propagated through the wire to the periphery of the wire-silicon interface. This wave form is observed as a periodic cutting action into the silicon perpendicular to the pulsing direction. A fine ball-like formation in the grooves of the wave region at the bond zone was a feature common to the different bonding surfaces. The wavelength and wave amplitude vary linearly with the applied power as does the tip-to-tip displacement of the wedge. The groove spacings are of the same magnitude as the wedge displacement. For constant power and time, increased load increases the size of the central bond region that does not experience the wave action. For constant load and power, the width of the wave affected periphery increases toward the center of the bond with time. The method of thermally induced stacking faults by steam oxidation was used to characterize the residual bond strains in the silicon. Faulting was found in the peripheral region of the bond where the wave action was operable. This faulting correlated to stresses generated in the pulsing direction and not to the directions of gross material flow. Reliable bonding depends upon a proper control of the gross and wave flow processes by optimizing material properties as well as machine variables. A model has been developed to qualitatively relate the influence of these variables and the manner in which a change in one parameter affects the response of the remaining variables.

The Microelectronic Wire Bond Pull Test-How to use It, How to Abuse It

Abstract: The wire bond pull test is the most universally accepted method for controlling the quality of the wire bonding operation, and thereby offering added assurance that semiconductor devices will not fail in the field due to weak wire bonds. Specific test procedures and pull-force values are called out in military and other device purchase specifications, and yet there has never been a carefully controlled interlaboratory comparison of this important test. All of the variables that are known to affect the bond pull test are examined including ones that cannot be treated theoretically, such as bond peeling and tearing. Careless pulling methods and other abuses that affect test results are described and the results of an eight-organization interlaboratory pull test experiment are given. The conclusions are 1) attempts to cut costs during the test by following nonstandard procedures will generally result in pull-force values that are lower than those that would be obtained were the test conducted carefully in accordance with standard procedures; 2) Overdeformed bonds tend to show a larger percentage change in pull strength due to nonstandard pulling procedures than do less deformed bonds; 3) Although artificially inflated pull-force values can be obtained when one bond is significantly stronger than the other, the effort of intentionally exploiting this difference (cheating) in most cases is greater than any benefit derived.

Extreme Temperature Range Microelectronics

Abstract: Down-hole geothermal instrumentation must operate over a large temperature range. The technology and capabilities of room temperature to 300°C hybrid and printed-circuit (PC) board electronics that were developed during the last two years to meet that need are summarized. To ensure rapid widespread commercialization, this technology was developed, insofar as possible, using commericaUy available components, devices, and materials. Initial extensive high-temperature characterization revealed that selected thickfilm passive components and silicon junction-field-effect transistors had electrical parameters sufficiently insensitive to temperature change and sufficiently constant in time at high temperatures to form the backbone of this circuitry. Attachment techniques needed to be developed, since standard methods failed at high temperatures. Similarly, circuit design innovations were needed because of the restricted list of parts. Voltage regulators, line drivers, voltage comparators, special purpose amplifiers and multiplexers were constructed and operated over the 25-300°C temperature range. Temperature and pressure monitoring instruments using these circuits have been used for downhole measurements in geothermal wells. Methods of fabrication, circuit performance, and the scope of future work are discussed.

The Lubrication of Electrical Contacts

Abstract: The objectives of lubricant compounding for industrial uses involving the possibility of metallic contact, and those of lubricant compounding for electrical contacts are almost mutually exclusive. In the former case surfaces must be separated and in the latter, metallic contact must be maintained. The modern principles of lubrication are therefore simply explained and those which may be applicable to electrical contacts in field field of boundary lubrication are stressed. Types of contacts are then defined and the appropriate lubricant properties applicable to each type are discussed; some (like creep, prevention of oxide formation, and resistance to arcing) in more detail than others. Methods of application are discussed. The aim is to suggest directions for much needed research in the lubrication of electrical contacts.

High-Current Brushes, Part I: Effect of Brush and Ring Materials

Abstract: Experiments were conducted to assess the potential for extending the excellent performance of conventionally loaded brushring current collection systems which operate in inert gas environments to much higher current densities. Recent advanced design machines require current collection systems capable of efficient continuous operation at densities to at least 150 A/cm2. Based on screening test data presented here, the present state-of-the-art practice of 10 A/cm2brush current density is extendible to at least 80 A/cm2, the limit of our test range. Commercially available graphite brushes containing 65 to 75 weight percent (w/o) silver combined with high-strength highconductivity copper alloy slip rings are recommended for more extensive testing at higher current densities in more sophisticated test machines.

Radiation Effects on Silicon Charge-Coupled Devices

Abstract: The permanent ionizing and neutron radiation-induced degradation in silicon charge-coupled devices, (CCD's), along with transient upset effects, are reviewed. The operation of a threshold voltage insensitive CCD input technique in a total dose radiation environment is evaluated. CCD structural design rules for decreasing ionizing radiation sensitivity are presented. The increased total ionizing dose tolerance of CCD's fabricated with a radiation hard oxide is described. Liquid nitrogen temperature irradiation effects in CCD's are discussed.

High-Current Brushes, Part II: Effects of Gases and Hydrocarbon Vapors

Abstract: The performance of metal-graphite brushes sliding against a copper ring while carrying high current loads (to 80 A/cm2current density) has been evaluated under five nonoxidizing gas atmospheres (CO 2 , SF 6 , N 2 , He, and A) in the presence of constant water partial pressure (600 Pa) and under a dry CO 2 atmosphere in the presence of n-paraffinic hydrocarbon vapors (n-heptane to n-hexadecane, 0.2-1300 Pa) as vapor additives. Of the nonoxidizing atmospheres, a lowest friction coefficient (0.06) and lowest wear rate (0.7 mm3/Mm) were measured in file wet argon gas. Low wear rate was achieved in dry CO 2 with each of the hydrocarbon vapors, but the voltage drop, which was nearly constant for all, is higher than that observed in wet CO 2 . The latter phenomenon was implicated by static electric resistance measurements using graphite rod contacts under vacuum and under low partial pressures of the hydrocarbon vapors. The film resistances derived from the measurements remained near the same magnitude regardless of the carbon chain length of the vapor molecule. A discussion of absorption of these gases and vapors is presented.

Material Characterization of Thick Film Resistor Pastes

Abstract: The study of material characterization of DuPont 1400 BIROXr thick-film resistor pastes is described. An understanding of the aging mechanisms of thick-film resistors requires a precise knowledge of their chemical composition and material characteristics. This information provides the technical basis for the Arrhenius-type time-temperature extrapolations of accelerated aging data on the resistors in question. We have used X-ray diffraction and fluorescence to obtain a qualitative picture of the DuPont 1400 BIROX pastes. Results indicate that these pastes consist principally of a conductive oxide and glass phases after firing. The conductive oxide phase is a pyrochlore M2Ru207_x (M= Pb and/or Bi), and tile glass phase is a lead borosilicate glass frit. Small amounts of Cd, probably added as a TCR modifier, were also detected. It has also been determined that the proportion of glass phase increases as the sheet resistivity increases. On firing, some chemical reactions were observed, and an increase in the crystallite size of the conductive phase was confirmed. In addition, the chemical composition of the end members (10 \Omega and 106 Omega /s) was found to be different from the general composition of the 1400 BIROX series. The conduction mechanism in thick-film resistors is discussed in some detail. The role of additives and the doped glass phase is emphasized. An extensive review of technical, patent, and product literature has been made as a background for the study.

Suppression of Pip and Crater Formation During Interruption of Alternating Current Circuits

Abstract: The effect of adding W and Ni to Ag contacts in a slowacting switch has been evaluated. The experiments were performed in ac, 5.1 A and 12.4 A (peak), 220 V (rms) circuits. The erosion structure on the Ag contacts was a single pip and crater on each electrode. The addition of 10 percent by weight W to the Ag caused the erosion structure to change: many pip and crater structures were observed covering the contact surfaces (~60 structures after 120 000 switching operations) and the Ag-W contacts exhibited much greater arcing than the pure Ag contacts did, but the operating life nevertheless increased about 6 times. The Ag-W contacts failed by welding together. The addition of Ni (15 percent by weight) to the Ag resulted in a more uniform erosion of the contacts' surfaces and the duration of the arcing on closing and opening was very similar to that of pure Ag. After 160 000 operations very little loss of contact material was observed. These results are discussed in terms of the effect of the additives on the motion of the arc and the effects of the arc on the motion of the con- tacts.

The Behavior of Surface Oxide Film on Ruthenium and Rhodium Plated Contacts

Abstract: Although a surface oxide film on platinum-metal contacts is effective in preventing these contacts from polymerizing organic materials, it causes an increase in contact resistance. It is important to determine the thickness of surface oxide film which effectly prevents organic polymerization without causing a significant increase in contact resistance. Auger Electron Spectroscopy is used here to determine the thicknesses of the surface oxide films formed on Ru and Rh plated contacts at various temperatures in synthetic air. These are compared with results for untreated Ru and plated Rh contacts. Contact voltage versus contact resistance and contact force versus contact resistance characteristics of plated Ru and Ru oxidized after plating are measured by the crossed-rod method to study the relationship between contact resistance and thickness of a surface oxide film. The extent of organic polymerization on Ru and Rh plated contacts is determined by operating the contacts unloaded (dry) and monitoring the contact resistance after the treated and untreated contacts are exposed to benzene vapor. !t is found that, when the surface of the contacts is covered by a thin oxide film in either the case of plated Ru or plated Rh, the contact resistance can be low and stable, whereas contacts cleaned by Ar+ bombardment prior to sealing will be high in resistance. From these experimental results, it is determined that the thickness range of surface oxide film which prevents polymerizing without any measurable increase in contact resistance is approximately 5A ~25A.

Reducing Post-Trim Drift of Thin-Film Resistors by Optimizing YAG Laser Output Characteristics

Abstract: A study to determine the effects of laser parameters on tantalum nitride resistor stability is presented. A model Of the laser heat affected zone is proposed which relates laser pulse width, power, wavelength, repetition rate, and waist size parameters to energy delivered to remaining resistor material. Samples of qualified tantalum nitride resistors are trimmed with a range of laser parameters, and the results are compared with the model. The excellent agreement between the model and experiment allows these results to be used for process control and throughput versus tolerance calculations.

Reliability Evaluation and Failure Analysis for Multilayer Ceramic Chip Capacitors

Abstract: Reliability evaluation tests for multilayer ceramic chip capacitors mounted on a hybrid IC were implemented. Failure modes, failure mechanisms, and drift of characteristics were analyzed. Humidity acceleration as well as voltage and temperature accelerations were investigated to estimate the chip capacitor reliability. The chip capacitor reliability proved to be high and adequate for the service period of the communication system.

Mechanism and Control of Post-Trim Drift of Laser-Trimmed Thick-Film Resistors

Abstract: Some of the important parameters controlling the postlaser trim drift of 100, l-K, 10-K, and 100-K \Omega//\Box$^b$ thick-film resistors are reported. The fired thickness of the resistor plays a major role in the control of post-trim drift. The resistors with fired thickness (tf) \leq 0.5 mil show small ( \DeltaR/R \leq 0.3 percent) and predictable drift, whereas those with t f > 0.5 mil produce large ( \DeltaR/R \geq 0.3 percent) and unpredictable drift. A mechanism for the post-trim drift is proposed. Results indicate that the percent trimming for precision resistors should be held within 25 to 30 percent range for minimum drift. The trim geometry such as L-cuts or two P-cuts from the same side of the resistor produces the least amount of drift. The protective overglaze coating on the resistors has a beneficial effect of reducing the drift, especially for the resistors with t f > 0.5 mil. The resistor size (L X W) does not significantly influence the drift as long as the t f < 0.5 mil.

Chip-Module Package Interfaces

Abstract: The direction of progress for printed circuit board technology is illustrated through a design example using LSI chips and multichip modules. The interface requirements between the chips and modules and between the modules and the printed-circuit board are described. The use of large-scale integrated circuits in large systems is shown to require substantial increases in interconnection density at the module and the printed-circuit board. Approaches to providing the increased interconnection are described.

Electrical Overstress Failure Modeling for Bipolar Semiconductor Components

Abstract: Engineering techniques are presented for predicting the failure threshold of bipolar semiconductor components. The failure threshold is expressed in terms of a failure current and failure voltage. Prediction of the failure conditions is based on estimation of background doping concentration and junction area. These estimates may be reade either from specification sheet parameters commonly provided by manufacturers or from nondestructive terminal measurements.

Variable Microelectronic Inductors

Abstract: A thin-film microelectronic inductor is proposed. It is suitable for use in the frequency range from 5 to 20 MHz. The inductor is in the shape of a square spiral and is surrounded by patterned permalloy thin films. The pattern allows these films to be driven in their easy axes of magnetization by the high-frequency signal current. In the presence of a small dc magnetic field applied in the hard direction and equal to the anisotropy field, the resulting permeability is very high, and thus the inductance of the pattern is greatly increased. Since the inductance is a function of the dc magnetic field applied in the hard direction, variable inductors and tunable planar resonant circuits are readily implemented using the proposed device. The design considerations of the device are described, and the significance of the theoretical results is discussed. Experimental work is being carried out to verify the above results.

Velocity Distribution of the Moving Cathode Spot in Breaking Contact Arcs

Abstract: The motion of cathode spot in Au, Ag, Cu, and Ni contacts, which affects the formation of the pip and crater structures, has been precisely observed by utilizing a high-speed camera in moderate current, atmospheric pressure dc break arcs. Dependencies of contact material, current and voltage on the motion of cathode spot were examined experimentally. Behaviors of the cathode spot were evaluated by three factors: 1) the maximum length moved (l mx ) which was defined as a maximum shift distance of the spot in an arcing; 2) the maximum moving width (l mw ) which was the difference between the maximum and minimum distances on the motion of cathode spot; and 3) distributions of velocity of moving cathode spot. For these contact materials, the cathode spot moved rapidly in the sequence of Au > Ag > Cu > Ni. Moreover, the crater structures of each contact have been reasonably explained through the above behavior of the cathode spot.

Breakdown in Ceramic Capacitors Under Pulsed High-Voltage Stress

Abstract: Failure in ceramic capacitors due to high-impulse voltages was investigated to determine the parameters which limit the breakdown voltage. It was found that the breakdown field strength is a function of the dielectric constant, the dielectric thickness, and the capacitor area. There was little correlation between the breakdown voltage and the rated voltage. Breakdown usually occurred at the edge of the electrodes, and only small changes in capacitance and dissipation factor resulted.

Pulsed High Power Brush Research

Abstract: The successful utilization of homopolar machines for pulsed power applications requires the development of solid brushes capable of operating at very high current densities and slip ring speeds. Relevant data on the major current collection parameters are reviewed and, where possible, functional variations are suggested. Measured data on voltage drops, friction coefficients and wear rates at current densities up to 27.9 MA/m2(18 kA/in2) and slip ring speeds up to 360 m/s in air, hydrogen and carbon dioxide are discussed.

High-Frequency Measurement of Q-Factors of Ceramic Chip Capacitors

Abstract: No reliable instrumentation systems have been available for the measurement of capacitor properties, particularly Q-factor, in applications requiring operation in the 100-1000 MHz range. The production of large numbers of multilayer ceramic chip capacitors for such special use is a very recent development. The need for reliable measurement equipment is increasing both for purposes of device evaluation and device development. A high-Q transmission line has been constructed, and a mathematical system has been devised for employing that line in a resonant mode to determine capacitor parameters, and particularly Q-factor, at the range up to and including microwave frequencies. The device produces accurate reliable data. The equipment can be reproduced and the system can be used in analysis and evaluation with a degree of confidence not possible in the past.

Fatigue Failure of Encapsulated Gold-Beam Lead and TAB Devices

Abstract: A thermal stress model for gold-beam lead and tapeappliqued beam (TAB) devices TC bonded to a substrate is presented. The bonded appliqued beam-centerline is assumed to be geometrically similar to that of a bonded gold-beam lead. The devices are assumed to be encapsulated with room-temperature vulcanizing rubber (RTV). For gold-beam lead devices and TAB devices with large chips and long beams (LL c \geq 0.0014 in2, where L is free beam length and L c is chip length), the analysis predicts that the RTV remains intact and drives the chip up and down during temperature cycling. For small TAB chips with short beams (LL c \leq 0.0004 in2), however, the RTV may rupture and would then not control the chip motion. The protective capability of RTV is uncertain for such a structure. An analysis of gold beam fatigue relates the cycles to median failure (N f ) to magnitude of a temperature cycle ( \Delta T). The analytical results are compared with temperature cycling data for a gold-beam leaded device at \Delta Ts of 190, 100, 75, 50, and 35°C. Although there are differences between the experimental and analytical results, the trends are close and the degree of agreement is encouraging. Additional comparisons are made to establish the influence of the beam dimensions, gold properties and bonded geometry on the fatigue life. The N f versus AT analysis combines estimates of cyclic strain ( \beta\varepsilon ) as a function of AT with experimentally obtained fatigue data (N f as a function of \Delta\varepsilon ). The \Delta\varepsilon versus AT estimates are derived from elasticity and plasticity stress analyses. Since fatigue data on electrodeposited gold is apparently nonexistent, N f versus \Delta\varepsilon data on bulk gold is used. Equations of Weibull are used to scale the data to specimens with beam-lead dimensions. It is concluded that the model provides an adequate prediction of gold-beam lead device behavior over a wide range of temperature cycling conditions and beam geometries predictable from models of beams bent during bonding. Uncertainties exist over the relative severity of the high temperature portion of the thermal cycle versus the low temperature regime. The uncertainty is related to the effect of mean strain on fatigue life as well as to the annealing of gold. The low-cycle fatigue range is reasonably expressed by the Coffin-Manson law (i.e., N f = C( \Delta T)2) subject to the conditions that the plastic strain is large and is valid for a limited temperature cycle range. The elastic range extends for a \Delta T of roughly 50°C and normal fatigue behavior exists for \Delta T less than 50°C.

Contact Resistance Characteristics at Low Temperature

Abstract: The application of cryogenics to the fields of electrical engineering has great possibility. However, performance of contacts used in the application may be estimated to deteriorate due to contaminant films. It is important subject to clarify the electrical conduction mechanisms of contacts covered with contamination films to obtain low contact resistance characteristics at the low temperature as well as at the normal temperature. From these standpoints, electrical conduction mechanism and contact resistance at low temperature were examined. Schottky current was observed in oxide film covered contacts over a range from 300 K to 77 K. The contact resistance at the low temperature increased by approximately 100 times or more over that of normal temperature due to Schottky conduction. For clean surface, the contact resistance passes through a minimum at low temperature due to thermal contraction of true contact area. In conclusion, Schottky conduction was found predominantly. Therefore, if the contaminant films exist at the contact surface, contact resistance increased remarkably at low temperature. Moreover, even for contacts of clean surfaces, contact resistance has a limiting value unlike resistance of metal conductors. These results give a serious problems in the performance of contacts for the cryogenic application.

Ultra-High Density VLSI Modules

Abstract: A novel packaging approach is described for low-power digital VLSI (very large-scale integration) technologies, which provides low-capacity interconnections throughout and eliminates higher packaging levels. The approach is based on the use of hybrid circuits utilizing high-density interconnections on sapphire substractes with a Fotoceram (trademark-Corning Glass Company) backing. These sapphire/Fotoceram wafers are assembled in a single stack, and wafer-to-wafer interconnections are provided by a ring of elastomeric contacts. This assembly is mounted in a sealed container utilizing ebullient cooling. This design provides very high packaging densities, minimizes circuit delays, and is easily maintainable.

Sputtered Ruthenium as a Contact Material for Sealed Reeds

Abstract: Cobalt-hardened gold is used as a contact material on remreed sealed contacts. A possible change of material for contacts of this type has been studied. The contact material investigated consists of a thin film of ruthenium over a thicker film of hardened gold. Both films are deposited by dc sputtering. The advantages of this contact finish compared to electroplated hard gold are reviewed: lower erosion per arcing operation, reduced arcing, and better resistance stability due to lower foreign element comtamination. The reliability of ruthenium contacts is related to that of hard gold contacts. A small change of contact geometry (gap and overlap) is needed to maintain the contact resistance at the level found with hard gold. The reliability is better in low-voltage (~5 V) level operation, due to the elimination of carbonaceous contaminants. The ruthenium contacts exhibit longer life in erosion tests involving cable discharges. Ruthenium contacts can be sealed off in a water free atmosphere so they could be used at below-freezing temperatures. Ruthenium contacts are able to withstand magnetostrictive scrubbing without sticking failures. However, the life of the ruthenium contact when switching current of 100mA (make and break) at 50V in a resistive load does not show significant improvement over hard gold. This is explained in terms of bridge transfer due to chattering during the make operation of the contacts.

Environmental Tests for Connectors and Contact Materials: An Evaluation of a Method Involving Sulfur Dioxide

Abstract: The objectives of lubricant compounding for industrial uses involving the possibility of metallic contact, and those of lubricant compounding for electrical contacts are almost mutually exclusive. In the former case surfaces must be separated and in the latter, metallic contact must be maintained. The modern principles of lubrication are therefore simply explained and those which may be applicable to electrical contacts in field field of boundary lubrication are stressed. Types of contacts are then defined and the appropriate lubricant properties applicable to each type are discussed; some (like creep, prevention of oxide formation, and resistance to arcing) in more detail than others. Methods of application are discussed. The aim is to suggest directions for much needed research in the lubrication of electrical contacts.

Thermocompression Bondability of Bare Copper Leads

Abstract: Thermocompression bondability of bare (unplated) Cu leads to TiPdAu ~ms on alumina substrates was investigated. This is an extension of earlier work to reduce the Au-plating thickness on Cu leads. Initial bondability, prebond shelf life, and long-term reliability were evaluated. The results follow. 1) Initial bondability is satisfactory provided suitable bond deformation is used. 2) Prebond shelf life is described by t(SL) = 7.5 X 10'-10 exp (0.80 + 0.2 eV/kT) where t(SL) is the time in hours to unacceptable bondability. The mechanism causing loss of bondability is surface oxidation of the Cu leads. A prebond shelf life (without recleaning) of about two years is indicated for storage at room temperature. 3) Long-term reliability is described by t(LT) = 9.7 x 10-'10 exp (1.0 0.2 eV/kT) where t(LT) is the time in hours to unacceptable bond strengths. The mechanism causing loss of bond strength with time is believed to be interdiffusion of the Cu lead with the Au metallization. A lifetime of greater than 40 years at 50°C is predicted. Comparisons between the present findings for hare Cu leads and those previously obtained using Au-plated Cu leads are presented. They indicate that the bare Cu leads have less processing and safety margin. But for many applications, bare Cu leads should be acceptable.

Tantalum Film Capacitors with Improved AC Properties

Abstract: Tantalum thin-film capacitors have been fabricated from magnetron sputtered tantalum films with different nitrogen concentrations. Capacitors made from film containing between 13 and 22 atom percent nitrogen and heat treated at temperatures between 250°C and 350°C show lower ac losses and TCC, and improved capacitance stability, when compared to standard capacitors based on tantalum containing 3 atom percent nitrogen. In addition, the dc properties of the improved capacitors are equivalent or better than those of the standard product. It is proposed that in capacitors containing over 13 atom percent nitrogen, the nitrogen fills interstitial vacancies in the tantalum lattice. A barrier is therefore produced to substantial oxygen diffusion from the dielectric into the underlying tantalum film during exposure to temperature between 250° and 350°C. In addition, results at 200°C suggest that a second mechanism for improved characteristics is the removal of water or citrate molecules, incorporated during anodization, from the hulk of the dielectric.

Mass Changes of Adhesives During Curing, Exposure to Water Vapor, Evacuation and Outgassing, Part I: Ablefilms 529, 535, and 550

Abstract: Mass losses of Ablefilms 529, 535, and 550 during curing ranged from 1-1.8 percent of the adhesive. The major gases evolved included the curing agent, solvent, water, carbon dioxide, and carbon monoxide. Exposure of Ablefilm 529 to 2.4 kPa (18 tort) water vapor yielded a saturation uptake of 0.27 percent of the sample mass, which could supply up to about ten times more water than needed for a dew point of 22°C in a volume of 40 mm3. Ablefilm 550 sorbed even greater quantifies of water.

Acoustic Microscopy of Ceramic Capacitors

Abstract: The acoustic microscope has been shown to be a powerful new tool for characterizing nondestructively the internal structure of multilayer ceramic capacitors. Delamination resolution has been shown to be greater than is available with other current techniques. This tool is sensitive to erratic electrode stacking, ceramic margins, termination quality, and other defects. As such, it is already useful in production monitoring, failure analysis, and research with perhaps new capabilities still to be discovered.

A Field Study of the Electrical Performance of Separable Connectors

Abstract: A three-year study of separable electronic connectors in operating telephone equipment was conducted to determine failure mechanisms and rates of presently used designs. The study of nine different connector types (six of which are reported) was carried out in four cities, and higher than expected contact resistances were observed. These were due to factory contaimination and not pore corrosion as originally assumed. Nevertheless, there is some evidence to suggest that a time-dependent "wear-out" mechanism exists. Finally, disengagement/reengagement cycling does not offer an adequate "fix" for reducing high-contact resistance because the frequency of reducing contact resistance is about the same as the frequency of increasing contact resistance in some connector designs. The results are from the efforts of many people working as a team at four Bell Laboratories locations and are presented in order to bring together several important conclusions.