Showing papers in "IEEE Transactions on Components, Hybrids, and Manufacturing Technology in 1985"
TL;DR: A critical review of fretting based on published work by the author and by other investigators can be found in this article, where a discussion of mechanisms of transfer, wear, oxidation, and frictional polymerization which apply to the fretting of contacts; the effect of operational parameters such as cycle rate and force on contact resistance change; a survey of materials whose fretting behavior has been determined; and an analysis of the different roles which lubricants play in controlling fretting according to the contact materials that are involved.
Abstract: Fretting in mated electronic connectors can lead to unacceptable increases of contact resistance. Although this phenomenon has been known for many years, it was not until interest developed in replacing gold by certain low-cost contact materials, such as tin-lead solder plate, that the incidence of fretting problems rose dramatically. Over the past 10 years there has been considerable research on the origins of this contact resistance instability, on methods for its measurement, and on finding ways to avoid the problem. This paper is a critical review of fretting based on published work by the author and by other investigators. Included are a discussion of mechanisms of transfer, wear, oxidation, and frictional polymerization which apply to the fretting of contacts; the effect of operational parameters such as cycle rate and force on contact resistance change; a survey of materials whose fretting behavior has been determined; and an analysis of the different roles which lubricants play in controlling fretting according to the contact materials that are involved. Connector design, the particular conditions of field use, expected connector lifetimes, and their reliability requirements determine whether contact materials will be satisfactory. Hardware tests which tend to cause fretting, such as shock and vibration, should be employed before new contact materials and designs are incorporated in connectors.
221 citations
NEC1
TL;DR: A new aluminum nitride (AIN) substrate has been developed using the hot press sintering technique, which has high thermal conductivity of 160 W/mK at room temperture as discussed by the authors.
Abstract: A new aluminum nitride (AIN) substrate, which has high thermal conductivity of 160 W/mK at room temperture, has been developed using the hot press sintering technique. The new AIN substrate has the following excellent characteristics. 1) The thermal conductivity is eight times as high as that of AI 2 O 3 at room temperature and is almost equal to that of 99.5 percent BeO at 150°C. 2) The thermal expansion coefficient is smaller than that of AI 2 O 3 and BeO, and is close to that of a silicon semiconductor chip. 3) The electrical properties are almost as good as those for AI 2 O 3 and BeO in the wide frequency range. 4) It not only has higher mechanical stength but also easier machinable property than AI 2 O 3 . It is characterized by its light transparency from visible light to the infrared wavelength region. It was proved that the new AIN substrate is able to be metallized with good adhesion strength by the conventional evaporating method and the conventional sputtering method. The new AIN was found to be applicable to three kinds of semiconductor devices: 1) silicon epitaxial transistor, 2) GaAIAs light emitting diode, and 3) InGaAsP laser diode. Also, another AIN substrate was developed using the normal sintering technique, which has high thermal conductivity of 140 W/mK at room temperature.
103 citations
TL;DR: In this article, a procedure was developed for screening encapsulation plastics for mechanical stress on semiconductor chips, which involves temperature cycling of molded packages containing unpassivated test chips, and the degree of deformation of the metallization was used as a measure of stress on the chip.
Abstract: Plastic encapsulation of large semiconductor chips has resulted in increased stress-related failures such as cracked passivation, metal deformation and delamination, cracked chips, cracked packages, and parameter shifts. The large mismatch in the coefficient of thermal expansion between the silicon chip and the plastic encapsulant is felt to be the major contributor to these failures. In an effort to minimize stress problems, many mold compound manufacturers have modified their formulations and epoxy resin chemistries. As a result, many "low-stress" mold compounds have been introduced in recent years. A procedure was developed for screening encapsulation plastics for mechanical stress on semiconductor chips. The method involves temperature cycling of molded packages containing unpassivated test chips. The degree of deformation of the metallization is used as a measure of stress on the chip. Several semiconductor grade epoxy mold compounds were evaluated with this procedure. Many of the newer low-stress epoxy formulations gave metal deformation equal to or greater than the standard formulations. One of the materials, however, yielded no observable metal deformation under the test conditions. Metal deformation is a result of shear stress acting at the chip surface, with the direction of the deformation being toward the center of the chip. Microscopic cross-sectional analysis of temperature cycled packages revealed microcracks in the plastic which appeared to have initiated at the chip edge. In most cases, the cracks were about 400/ \mu m long and thus did not reach the package surface. The microcracks appear to promote metal deformation, since they reduce the restrictions on plastic movement at the chip surface. SEM analysis was employed to determine the topography of the deformed aluminum stripes. The effects of chip size, aluminum line width, number of temperature cycles, and post-cure conditions were also determined.
71 citations
TL;DR: In this article, copper was successfully formed on aluminum nitride (AIN) ceramics using X-ray micro analysis (XMA) and Xray diffraction (XRD) analysis, copper was formed at the boundary between the Cu metal and oxidized AIN.
Abstract: Thick film and direct bond copper (DBC) were successfully formed on aluminum nitride (AIN) ceramics. Commercially available gold (Au), silver-palladium (Ag-Pd), and copper (Cu) thick film pastes for alumina (AI 2 O 3 ) were formed on AIN under exactly the same firing conditions as on AI 2 O 3 . From X-ray micro analysis (XMA) and X-ray diffraction (XRD) analysis, copper (Cu), lead (Pb), silicon (Si), and oxygen (O) were observed at the adhesive boundary of the thick films and ceramics. On the contrary, poor bondings were observed when bismuth (Bi) segregated at the adhesive boundaries. Pre-oxidation of AIN ceramics at high temperature around 1250°C was required for the bonding of DBC to AIN. Cu 2 O was formed at the boundary between the Cu metal and oxidized AIN, thus copper was directly bonded to AIN firmly. Bonding strength, peel strength, and wire bondability were enough for practical use in applications to high power modules and large-scale integrated (LSI) packages.
56 citations
TL;DR: In this paper, a preliminary computer calculation shows that the arc voltage and the immobility time of the arc on the contacts is very important for the quality of the limitation of short-circuit currents in electric installations.
Abstract: The noteworthy increase in the present low-voltage circuitbreaker capacity implies that these products must be able to dramatically reduce the short-circuit currents in electric installations. This important current limitation can only be obtained by rapidly inducing an arc voltage in the circuit breaker, that opposes the mains voltage. A preliminary computer calculation shows that the arc voltage, and in particular the immobility time of the arc on the contacts, is very important for the quality of the limitation. Electric tests, carried out with constant or alternating current, made with an experimental device, clearly show the influence on the stagnation time of the contact opening speed and of the nature of the contact materials. The speed during breaking, which is constant, ranges between 2 m/s and 13 m/s (current publications are limited to 5 m/s). The contact materials under survey have been copper and silver, taken as references, and for the first time silver cadmium oxide as breaking material in circuit breakers. Tests have resulted in a semiempiric arc voltage model, deducted from a Cassie equation, extended to an arc being stretched. Solving by means of a computer the equation governing a break, for this arc voltage model, makes it possible to know beforehand with great precision the performances of a product.
48 citations
TL;DR: In this paper, an innovative low-stress epoxy encapsulant was developed for large and stress-sensitive devices by the utilization of silicone modification technology, which can be explained by achieving a lower Young's modulus and thermal expansion coefficient.
Abstract: An innovative low-stress epoxy encapsulant was developed for large and stress-sensitive devices by the utilization of silicone modification technology. The characteristics can be explained by achieving a lower Young's modulus and thermal expansion coefficient. The low-stress level was confirmed by piezo-resistance measurement with actual results showing a definite, significant improvement against package and passivation cracks. An interesting microstructure of the new material was determined and labeled "Sea-Island" structures.
45 citations
TL;DR: In this article, the effects of the strain loading waveform in isothermal mechanical fatigue and frequency and strain range in true thermal cycling were investigated experimentally for effects of solder joint fatigue and accelerated life testing of leaded chip carriers.
Abstract: Solder fatigue was investigated experimentally for effects of the strain loading waveform in isothermal mechanical fatigue, and frequency and strain range in true thermal cycling. Rapid strain loading followed by a long hold period at constant strain was found to be very damaging compared to constant rate cycling at the same peak amplitude and period. Thermal cycle fatigue data showed a stronger dependence on cycle period and weaker dependence on strain range than reported results in isothermal mechanical fatigue. Implications of the experimental findings are discussed with regard to solder joint fatigue and accelerated life testing of leaded chip carriers. Isothermal mechanical fatigue testing was carried out at room temperature with a custom torsional apparatus having an optical servo-loop for strain control. Mean joint compliance change per cycle was used as a fatigue metric. Experiments were carried out on 5/95 and 63/37 Sn/Pb solder joints. Mean stress in the solder joints was measured at 23°C and found to relax significantly after several minutes. Thermal cycle experiments were carried out with an air impingement apparatus capable of cycling the test samples between 30110°C in periods ranging from 2 to 120 min. Ceramic chip carriers were soldered to aluminum, zinc, and stainless steel substrates to permit fatigue life data to be taken from 0.3-14 percent strain range. A conventional crack criterion was used as the fatigue metric in the thermal cycle experiments. A simple finite element model of a 68 post molded leaded chip carrier (PLCC) was analyzed to examine expected stress loading of the solder joints under typical operating conditions. Transient thermal stress loading and low stress creep of the solder joint are discussed in light of this model and known creep properties of solder. It is shown that during typical operating cycles, the total creep strain can account for the majority of plastic or nonrecoverable strain.
38 citations
TL;DR: In this paper, a theoretical model to assess the signal degradation caused by the packaging of new devices is discussed, and its predictions are compared with results from time domain reflectometry (TDR) and network analysis measurements.
Abstract: Advances in silicon bipolar and GaAs FET technology have enabled digital circuits of medium complexity to be fabricated for operation at gigabit rates. However, signal degradation caused by the packaging of these new devices will limit their useful application. A theoretical model to help assess this problem is discussed, and its predictions are compared with results from time domain reflectometry (TDR) and network analysis measurements. Also described is a novel exlension of the TDR technique based on the use of fast Fourier transform (FFT) analysis, including the design of test fixtures and the analysis software which is run on a desktop computer. The results presented demonstrate that both the model and the FFT measurement technique accurately represent the electrical performance of all those packages tested.
33 citations
TL;DR: In this paper, a number of contact aid compounds commonly used for aluminum-to-aluminum connectors and conductors were evaluated on the basis of their effect on the contact resistance-force/torque relationships, stability to thermal degradation, consistency, and ability to protect the contact against fretting.
Abstract: A number of contact aid compounds commonly used for aluminum-to-aluminum connectors and conductors were evaluated on the basis of their effect on the contact resistance-force/torque relationships, stability to thermal degradation, consistency, and ability to protect the contact against fretting. The results showed that the use of the contact aid compounds markedly improves the contact properties of a joint and significantly reduces its susceptibility to fretting.
29 citations
TL;DR: The switching behavior of several varieties of Ag/SnO 2 contact materials was tested in commercial contactors and the results were compared with those obtained with standard Ag/CdO material as mentioned in this paper.
Abstract: The switching behavior of several varieties of Ag/SnO 2 contact materials was tested in commercial contactors and the results are compared with those obtained with standard Ag/CdO material. The properties tested were arc erosion under AC3 and AC4 conditions, contact resistance, temperature rise under continuous current, and making capacity. It was found that the newer Ag/SnO 2 -type materials, which contain WO 3 or MoO 3 in order to reduce overtemperatures, qualify as substitutes for Ag/CdO.
21 citations
TL;DR: In this paper, the effect of a thixotropic synthetic lubricant, composed of a mixture of an oil and a wax, on the production of fretting corrosion at dissimilar metal interfaces under conditions of very mild vibration is evaluated.
Abstract: The early failure rate of socketed dual in-line package (DIP) devices that used dissimilar metal interfaces (Sn/Au and SnPb-solder/ Au) have been previously reported by the authors. These high resistance failures (both in field systems and in the laboratory) were attributed to the formation of tin oxide fretting corrosion at the device/socket interface. Lubrication of metal contacts has been shown to reduce or eliminate fretting corrosion in various contact configurations. In this study, the effect of a thixotropic synthetic lubricant, composed of a mixture of an oil and a wax, on the production of fretting corrosion at dissimilar metal interfaces under conditions of very mild vibration is evaluated. The static resistance behavior of these samples was studied for 18 months. The samples were then disassembled and the contact surfaces examined using scanning electron microscopic (SEM) and scanning Auger microprobe (SAM) techniques. The resistance data obtained indicated that all dissimilar metal interfaces failed repeatedly. Only the SnPb/SnPb and Au/Au interfaces showed no significant increases in resistance over the test period. Subsequent SEM and SAM investigations showed that all of the dissimilar interfaces failed due to build-up of tin oxide fretting corrosion resulting in high contact resistances (> 100 \Omega ). It was observed that lubrication was effective in reducing both the amount of and the rate of fretting corrosion, as well as dispersing the corrosion that formed. The greatest reduction of fretting corrosion occurred in the SnPb/SnPb systems such that no resistance failures occurred during the 18 month study.
TL;DR: In this article, a comprehensive study using normal probability paper to project gold wire bond reliability has been performed and the results indicate that several orders of magnitude increase in reliability can be achieved from using optimum wire bond parameters.
Abstract: A comprehensive study using normal probability paper to project gold wire bond reliability has been performed. Reliability projections have been made using ceramic capillaries, tungsten carbide capillaries, gold wire, gold/palladium alloy wire, three different device metallizations, nine different wire lot numbers, and seven ultrasonic power settings. The reliability projections from all of the tests were then compared to the ball shear force from each test to correlate shear force with reliability. The results indicate that several orders of magnitude increase in reliability can be achieved from using optimum wire bond parameters. The ball shear force value has also been shown to be very useful in predicting reliability and thus eliminating time consuming wire pull tests.
TL;DR: In this article, basic investigations of the commutation and switching mechanisms between contacts and parallel thyristors and on results of erosion measurements at currents up to 500 A, 220 V, 50 Hz are reported.
Abstract: Basic investigations of the commutation and switching mechanisms between contacts and parallel thyristors and on results of erosion measurements at currents up to 500 A, 220 V, 50 Hz are reported. The experiments are carried out with different contact materials (copper, hard silver, silver/metal oxide compound). Depending on thyristor data; commutation inductance, contact material, and current, the commutation time and thus the arcing time for a given arrangement lies in the order of tens of microseconds. Consequently the contact erosion stays low. In comparison with conventional contactors the material losses are two to three orders of magnitude lower. Different contact materials range qualitatively in the same sequence as in conventional switches. The arc voltage at and immediately after the contact separation is analyzed. A simple model taking into account the current constriction in the contact material near the arc roots can explain the measured dependences.
TL;DR: In this paper, the authors used the finite element method (FEM) to calculate the plastic part of the stress-strain curve for thin metal films from a Brinell indentation test.
Abstract: Mechanical stresses occurring in electrical contact situations were calculated with the aid of the finite element method (FEM). As a first step the stresses in a gold film on a nickel substrate, indented by a sphere, were calculated, assuming elastic deformations. With the same normal contact force the stresses in the film can differ enormously for different film thicknesses of the gold. In many electrical contact situations plastic deformations occur. As a second step these deformations were also calculated. Therefore it is necessary to know the plastic part of the stress-strain curve. A method is presented for obtaining this curve for thin metal films from a Brinell indentation test. An elasticplastic contact situation for a cylinder sliding over a gold surface with different friction coefficients is investigated. It is shown that phenomena like the onset of prow formation and cracking of the surface can be observed from the calculated results.
IBM1
TL;DR: A bibliography of 237 publications dealing with heat transfer in electronic equipment is presented in this paper, covering the period from 1970-1984, although a majority of the papers listed were published in the last three years.
Abstract: A bibliography of 237 publications dealing with heat transfer in electronic equipment is presented. The papers are arranged in twelve categories, and cover the period from 1970-1984, although a majority of the papers listed were published in the last three years.
TL;DR: In this article, the authors measured the commutation delay of magnetically blown switching arcs up to 1 kA from a contact to an are runner, i.e., across an obstacle formed by a step downwards or by a gap in one of two parallel copper electrodes.
Abstract: This experimental investigation concerns the commutation of magnetically blown switching arcs up to 1 kA from a contact to an are runner, i.e., across an obstacle formed by a step downwards or by a gap in one of two parallel copper electrodes. The commutation delay of the arc was measured with the aid of an optoelectronical light detector. To obtain also detailed information about the arc commutation mechanism, both an optoelectronical analog arc motion indicator and a streak camera were used. The arc commutation delay depends mainly on the magnetic induction of the blast field, the geometry of the electrode step, and the site where the commutation takes place. The arc commutation behavior across gaps corresponds to that across steps. For both steps and gaps a polarity effect of the commutation mechanism was observed. In most cases an obstacle on the anode causes a shorter commutation delay than one on the cathode. The cathode spot always moves continuously downwards along the vertical front surface of a step or a gap, while the anode spot is able to jump across any obstacle without climbing downwards along its vertical face. All results can be qualitatively derived from an intuitive arc model which might be used to explain unexpected test results and to improve contact arrangements. Finally practical conclusions are drawn.
TL;DR: In this article, a vibrator monitored by a microcomputer controlled the vibration amplitude and frequency of a circuit breaker's separable contact was used to measure the fretting corrosion of separable electrical contacts with different base materials and coatings.
Abstract: The fretting corrosion of separable electrical contacts was studied with different base materials and coatings. The tests were performed on a device which simulates a circuit breaker's separable contact. A vibrator monitored by a microcomputer controlled the vibration amplitude and frequency. The normal contact force was also adjustable. Contact resistance, temperature, and vibrator's excitation current were recorded as a function of time and used to monitor the contact surface degradation. Scanning electron microscopy (SEM) and Xray analysis were used to characterize changes in the coating. In order to accelerate the aging process, the test is quite severe. Most of the coatings show contact resistance degradation after only a few hours. The materials investigated were copper, silver-plated copper and aluminium, tin-based coatings, and nickel coatings. Large differences between these materials were noticed. Also the influence of vibration amplitude, vibration frequency, and normal contact force were evaluated. The main goal of this study was to determine a standard fretting corrosion test for industrial use.
TL;DR: The particle sizes of Ru0 2 and glass powder have direct effects upon the resistance value, TCR, and current noise as mentioned in this paper, as well as their particle sizes have a direct effect on the current noise.
Abstract: The particle sizes of Ru0 2 and glass powder have direct effects upon the resistance value, TCR, and current noise.
TL;DR: In this article, the chopping current and the quenching capability during switching-off in a vacuum are investigated using Cu/Cr, Mo/Cu, and W/ Cu with added materials of high vapor pressure.
Abstract: The chopping current and the quenching capability during switching-off in a vacuum are investigated using Cu/Cr, Mo/Cu, and W/ Cu with added materials of high vapor pressure. Cylindrical contacts of small dimensions (15 mm diameter) with antimony, bismuth, cadmium, and zinc alloyed or added in solid form in holes or slots are used. The chopping current is determined duiing interrupting a 50-Hz current of 45 A. The investigation shows that alloying 2 percent of antimony or 3.7 percent of zinc to W/Cu 70/30 reduces the chopping current to about half of the value of W/Cu 70/30. Adding antimony, bismuth, cadmium, or zinc in solid form leads to a reduction from 6 A to about I A. The quenching capability is investigated in a synthetic test circuit using current injection with switchlng-off currents from 800-2400 A and values of the recovery voltage of 2.7 kV. The interruption properties of W/Cu 70/30 are deteriorated when components of high vapor pressure are added. If the contacts are separated shortly before current zero, multiple reignitions are possible due to the interruption of transient high-frequency currents. For the given circuit conditions, switching with short arcing times and small contact distances shows that multiple reignitions occur with all investigated materials. A dependence between reignition voltage and contact distance is given. Materials with a high vapor pressure generally reduce the reignition voltage.
TL;DR: In this paper, the authors performed electrical life tests in a dc contactor under DC4 and DC5 conditions and compared the performance of different silver-based contact materials with respect to the arc energy and material loss and transfer.
Abstract: Electrical life tests in a dc contactor are performed under DC4 and DC5 conditions. Results from our observations and erosion measurements are compared for different silver-based contact materials. For the device used a relation can be established between the arc energy and material loss and transfer. The erosion mechanism during the make operation determines the overall arc erosion to a larger than expected extent. Silver nickel 90/10 stands out as the contact material with the lowest erosion rate under both conditions.
TL;DR: In this article, a compliant press-fit pin connection in a plated through hole (PTH) is presented, where three fundamental design concepts for this connection are discussed: 1) the upper limit of pin insertion force to protect the copper plate of the inner PTH, 2) the lower limit of Pin retention force to accomplish reliable wire wrapping connection, and 3) acceptable PTH diameter tolerance.
Abstract: A design method for a compliant press-fit pin connection in a plated through hole (PTH) is presented. In this connection, both compliant press-fit pin and PTH cause elastic-plastic deformation. Considering this feature, three fundamental design concepts for this connection are discussed. First, three design conditions are set: 1) the upper limit of pin insertion force to protect the copper plate of the inner PTH, 2) the lower limit of pin retention force to accomplish reliable wire wrapping connection, and 3) acceptable PTH diameter tolerance. Second, the deformation and radial force characteristics were studied for both pin and PTH. These characteristics were numerically analyzed by using the elastic-plastic finite element method (FEM). According to actual connection states, the pin edge indentation effect into the plated copper is taken into consideration for the PTH deformation characteristics. Finally, the design point was determined, where the pin and PTH radial forces balance. This design point should satisfy the above-mentioned three conditions. An example of a compliant press-fit pin with N-shaped cross section was studied. Results from the numerical analysis are compared with those obtained from experiments. The two results compare favor- ably.
TL;DR: In this paper, the authors provide an analytical basis for the design and optimization of convective immersion cooling systems by focusing on the analytical development and experimental verification of composite relations for the natural convection heat transfer coefficients prevailing along the Surfaces of immersed, uniformly heated plates in both symmetric and asymmetric configurations.
Abstract: Complete immersion of electronic assemblies, in fluids of appropriately high dielectric strength and low dielectric constant, offers a most promising alternative to conventional thermal control measures. The present study is aimed at providing an analytical basis for the design and optimization of convective immersion cooling systems by focusing on the analytical development and experimental verification of composite relations for the natural convection heat transfer coefficients prevailing along the Surfaces of immersed, uniformly heated plates in both symmetric and asymmetric configurations.
TL;DR: The results of the differential thermal analysis (DTAt) and the thermal gravimetric analysis (TGA) of four different metal oxides and their respective Ag-MeO materials indicated that the thermochemical properties are directly influenced by the metal oxide components as discussed by the authors.
Abstract: The results of the differential thermal analysis (DTAt and the thermal gravimetric analysis (TGA) of four different metal oxides and their respective Ag-MeO materials indicated that the thermochemical properties of the Ag-MeO materials are directly influenced by the metal oxide components. The energies required to bring the different Ag-MeO materials into different thermal states were calculated, diseussed, and compared. This investigation postulates two hypotheses. First, the arc erosion loss of a contact material depends on the erosion mode. If the predominate mode is splattering, then the Ag-CdO material may be the superior to pure silver because it requires more heat to reach an equivalent thermal state. Second, the oxide, the function of which is to weaken the contact welding, tends to remain on the surface thus increasing the contact resistance. Cadmium, due to its low boiling point, evaporates from the surface. These unique properties may account for the superiority of Ag-CdO as a contact material over other single oxides.
TL;DR: In this article, the grain boundary potential barrier may offer a major source of impedance to leakage current in multilayer ceramic capacitors, and its decrease may result in device failure.
Abstract: Current-voltage and activation energy measurements can be used to probe grain boundary potential barriers. A common type of activation energy for Current conduction in a polycrystalline material is that due to the grain boundary potential barrier. Activation energy can be related directly to grain boundary barrier height. The height of this barrier depends on occupation of grain boundary states. Its decrease with applied voltage accounts for the superohmic current-voltage behavior of polycrystalline silicon and of ZnO varistors. It also accounts for positive temperature coefficient device behavior. A similar voltage dependence is reported here for barrier layer and COG type capacitors, where activation energies decrease from 0.99 to 0.44 eV and from 1.61 to 0.90 eV, respectively. Such decreases are not seen for X7R devices, even though currents are superohmic. Several mechanisms account for this. It is concluded that the grain boundary potential barrier may offer a major source of impedance to leakage current in multilayer ceramic capacitors, and its decrease may result in device failure.
TL;DR: In this paper, the influence of shape on the reliability of solder joints formed between 84 I/O, 0.025-in (0.635-mm) pitch noncastellated leadless ceramic chip carriers and multilayer printed wiring boards has been quantified.
Abstract: The influence of solder joint shape on the reliability of solder joints formed between 84 I/O, 0.025-in (0.635-mm) pitch noncastellated leadless ceramic chip carriers and multilayer printed wiring boards has been quantified. (A castellation is a metallized radial feature on the edge of a ceramic chip carrier for interconnecting conducting surfaces or planes within or on the chip carrier. Castellations are usually on all four edges of the chip carrier. Noncastellated chip carriers may use vias instead of castellations for achieving the same interconnection.) The method is discussed by which a solder joint can be shaped to provide a substantial improvement in thermal cycle performance. Aspects of the investigation that are reported include the room temperature tensile test characterization of the stress/strain behavior of 60Sn/40Pb solder, finite element method calculations of the impact of joint shape on the deformation behavior of leadless ceramic chip carrier solder joints, mechanical shear test characterization of selected solder joint shapes, and thermal cycle testing to quantify the fatigue performance of several shaped leadless ceramic chip carrier solder joints.
TL;DR: TRISIM1 as discussed by the authors, a capacitance and inductance calculation program for complex three-dimensional geometries, is described and the convergence of the numerical results to analytical or two-dimensional solutions is illustrated.
Abstract: TRISIM1, a capacitance and inductance calculation program for complex three-dimensional geometries, is described. The basic algorithm of capacitance calculation is Green's function integral equation method and the inductances are calculated by Neumann's formula applied to the thin filaments which make up the conductor segment. In TRISIM1, for efficient use of these algorithms, 1) triangular capacitance cells are adopted, 2) the calculation of the matrix element G ij is simplified according to the cell distance, and 3) the filaments for inductance calculation are infinitely thin. An approximate method of filament selfinductance calculation is used and the proof of its validity is given. The convergence of the numerical results to analytical or two-dimensional solutions is illustrated for simple geometries. The crosstalk noise induced among connector pins is calculated and the results are in good agreement with the measured data.
TL;DR: In this article, the problems and solutions relative to the design of PCB connectors for surface mounting are explored, and the conclusion being that all technologies are presently available to make the SMT connector a viable product family.
Abstract: The problems and solutions relative to the design of PCB connectors for surface mounting are explored. The systems approach is discussed because surface mount technology (SMT) for connectors is largely driven by the need for minimum labor, and automated production lines. Therefore, the design must consider the application of the connectors by robots. This in turn brings about the need to consider how to package the connectors for presentation to the robot, how to identify the connector, and how the connector can be picked Up by the robot arm, consistentlY. Once on the board, the effect of large mating and unmating forces must be brought into the equation. The connector must be held down by some mechanical means, which must also be compatible with the capabilities of the robot. These problems are all explored. Answers to the design Problems are put forth, the conclusion being that all technologies are presently available to make the SMT connector a viable product family.
TL;DR: In this paper, the effect of the angle of a line contact on the constriction resistance and the contact resistance was analyzed theoretically by solving Laplace's equation subject to boundary conditions determined by a modeled morphology of the contact.
Abstract: It can generally be considered that an actual contact makes an angle with the extension of the contact surface, because the tip of a contact element is convex in shape (macroscopically) and has surface roughness (microscopically). There are, however, few studies that have taken into account the effect of this angle on the constriction resistance or the contact resistance. A line contact is taken as an example, and the effect of space angle is analyzed theoretically by solving Laplace's equation subject to boundary conditions determined by a modeled morphology of the contact. The analysis leads to modified formulas for the constriction resistance and the contact resistance, which show that the effect can not always be neglected.
TL;DR: In this paper, the effects of wall material ablation and contact materials on the recovery of an arc gap were examined, and it was shown that the interaction of ablated wall-material vapor with the contact material has been observed to degrade gap recovery performance and enhance contact erosion.
Abstract: The purpose of this study is to examine the effects of wallmaterial ablation and contact materials on the recovery of an arc gap. A capacitive discharge current source provides 60-Hz arc currents up to 8 kA, and recovery is measured by reapplyiag a voltage step of 1 kV at a preselected time after current zero. The arc gap is surrounded by a cylindrical wall of an ablative insulating material. Both contact and wall materials are varied. We find strong dependence of the recovery time on the contact and wall material. For our geometry we observe fastest recovery at a current of approximately 5 kA, independent of wall materials. The interaction of ablated wall-material vapor with the contact material has been observed to degrade gap recovery performance and enhance contact erosion.
TL;DR: In this paper, a new measuring system of contact phenomena has been developed, which can control noncorrosive atmospheric conditions such as air pressure, mixture of air and noncrosive gas, and electrode temperature.
Abstract: A new measuring system Of contact phenomena has been developed, which can control noncorrosive atmospheric conditions such as air pressure, mixture of air and noncorrosive gas, and electrode temperature. The developed system is controlled by a microcomputer and measured quantities can be processed also by the microcomputer, and the final data can be printed Out and/or displayed. Arc duration and contact resistance can be measured under several atmospheric conditions at fixed contact opening speed. Contact materials of Ag and Pd were tested, and many interesting results for variation of arc duration have been obtained. For example, the variation of the arc duration for Ag and Pd contacts has a different tendency from each other with respect to the atmospheric pressure, and the variation of the arc duration relates the contact resistance.