A Multiperiod Minimax Resource Allocation Problem with Substitutable Resources

Electronic circuit boards’ heat dissipation capability directly impacts their service life since the heat dissipation efficiency of components directly impacts the board’s life. This work focused on the problem of the high surface temperature of the electronic components at the control unit stage of a cement production line. Three dimensional CFD model has been developed to simulate all components in this circuit board. A thermographic camera has been used to measure the surface temperatures of the components on the circuit board. Consistency was very good in the results. Two cooling mechanisms were examined, one of which is a traditional technique by forced air cooling technology. The other is using graphene nanosheets coating technology to increase the dissipation of the generated heat to the surrounding atmosphere. Although an electronic fan was very effective in cooling the electronic circuit components, which reduced the temperature by 22.6%, it has two undesirable features: the need to install it in a safe place and the need for power to run it. Graphene nanosheets coatings provide efficient and economical heat dissipation. The thin graphene layer enhances the radiation effect for the heat significantly. The results showed that the smooth aluminium plate coated with graphene and mounted directly to the back part of the transistor behind the plastic chip carrier piece for heat dissipation provided an efficient, sustainable and economical solution in thermal management. In comparison with the fan, the graphene nanosheets coating technology reduces the temperature by an average of 16.4% without consuming any energy.

Commonplace electronic appliances for consumer or industrial use are still mostly rigid or at maximum flexible entities. The flexibility of foldable units like laptops or cell phones is usually realized through flexible circuit board (FCB) interconnectors. Although flexibility allows for considerably enhanced degrees of freedom in design, it is not compatible with more complex three dimensional curvatures and dynamics thereof. In the past years a number or approaches to realize stretchable electronic circuits in order to reach beyond unidirectional bending or folding of electronics have been reported. In the frame of the European Project STELLA a particular fabrication technology for stretchable electronic systems has been developed at Technische Universitaet Berlin. This technology, termed ?stretchable circuit board? (SCB) technology, is derived from conventional printed circuit board manufacturing. Stretchability of the boards is enabled by (i) using polyurethane instead of FR4 or polyimide as a carrier material of the copper structures and (ii) a meandering design of the Cu interconnects between commercial (rigid) electronic components. Such boards can be (once) extended by up to 300% before fracture of the Cu interconnections. For repeated elongation/relaxation cycles elongations with a few percent are allowable in order reach high cycle numbers. Electronic components are assembled after local application of a solder mask and surface finish for solderability. The electronic interconnection is established using a low temperature solder alloy (SnBi, Tm=142?C). For protection and enhanced system robustness all components are subsequently encapsulated within a polyurethane capping. Systems thus realized can be readily attached to different kinds of surfaces. Most interesting for various application cases is the easy attachment to textile substrates by a simple lamination process. The field use case studies of stretchable systems in the frame of the STELLA are mostly sensor applications in the field of medical electronics like a breathing frequency monitor for babies, a shoe insole pressure sensor for diabetes patients, or a band aid inlay to measure pressure and humidity of an acute wound when pressure therapy is applied. The latter application will be described in more detail since different aspects of bio-medical applications can be explained with this example. Another emerging field of applications is textile electronics, where it has been proven, that stretchable electronics can serve a versatile building blocks for complex electronic systems integrated in textiles.

Circuit boards are one of the key elements of the electronics industry. Because of its demand for portable electronic goods, the production of circuit boards has become more significant. The most significant aspect of printed circuit board production is AOI or Automatic Optical Inspection. When generated in a single quantity, the PCB requires a small way to teach and change the AOI method for process validation. This paper proposes a mechanism of detection of capacitors trained on circuit boards using the YOLO V3 algorithm. YOLO is a form of rapid object detection based on the convolutional neural network or CNN. CNN’s deep network can distinguish specific characteristics from all the image features. The study developed an AI with the same feature that the manufacturing industry uses to assist students with an effective evaluation of their circuit boards. It focuses on the capacitor in a circuit board. It will not, however, be capable of distinguishing other forms of electronic components. Nearly 60 percent of the entire test has a performance of 100 percent detection, according to the test results, while 33.33 percent is over 70 percent detection and 6.66 percent has a 0 percent detection output. Capacitor recognition has been done with an overall testing accuracy of 93.33%.

Industry-produced printed circuit boards (PCBs) used by the United States Navy and Marine Corps are typically coated with a layer of "conformal coating" made of silicone or polyurethane in order to protect electrical and electronic components on the board. Conformal coating has to be removed every time board troubleshooting and maintenance are performed, and must be reapplied after board maintenance is complete. This can be an expensive and time-consuming process. This paper describes an effort to develop a non-contact solution to detect failed components on a PCB without having first to remove the conformal coating. This patent-pending technique detects density changes in the physical makeup of circuit board components due to failure. By analyzing ultrasonic reflections from the components at 2MHz, the authors were able to distinguish between working components and failed components with varying degrees of accuracy. The authors applied this technique to 1KΩ resistors and three types of transistor-to-transistor logic (TTL) integrated circuits (ICs). Overvoltage faults were induced in these components in order to generate observable density changes. To reduce human error, a measurement rig was built which incorporated an automated X-Y-Z plotter system, in order to process dozens of components at a time without human interaction. The data gathered by this system was processed to isolate only the acoustic reflections of components on a circuit board. Time-domain and frequency-domain features were then extracted. These features were used to train neural networks to distinguish between working components and components with over-voltage faults that were not readily observable by eye. Each type of component or chip needed to have its own associated trained neural network. For 1KΩ resistors, the system has demonstrated seventy to eighty percent accuracy in distinguishing components with over-voltage faults. For two of the TTL ICs, eighty to eighty-five percent accuracy has been achieved. For one IC type, a fifty-five percent accuracy was measured. The authors have demonstrated that low-cost acoustic measurements in the megahertz range can be used to detect failures in ICs and other common circuit board components.

A printed circuit board with attached components has been subjected to corona discharges for 200 h at a pressure of 8.66 Pa. The preliminary investigations indicate that: (1) High altitude corona discharges produce visible surface degradation on electronic circuit boards and mounted components. (2) The deterioration is most pronounced in the regions where the electric field is greatest. (3) The solder coating has been removed in localized areas of the interconnecting paths and the underlying copper is now exposed. (4) The circuit board becomes covered with a white dust, the composition of which is still unknown. (5) The deterioration increases with increased exposure up to 200 h, the maximum exposure time considered here.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Parts with circular features, such as holes, are common in the microelectronics industry. For example, holes used for mounting integrated circuits and other electronic components are found on printed circuit boards. If the holes in these circuit boards are not located or shaped properly, electronic components may not fit into them correctly. Due to the small size of many electronic components, holes must be manufactured precisely. Therefore, inspecting the circular shape of these holes requires a high degree of accuracy.

A heat transfer analysis of a convective air cooled electronic circuit board (ECB) in a vertical electronic circuit boards channel was carried out.To validate the model and the algorithms used in the computations, experimental tests were performed on dummy ECBs. Temperature distribution on an axial ECB and axial temperature distribution of air were measured with thermocouples. The temperature measurements were in good agreement with the computed value.As a working example, the temperature distributions of air flow and the vertical circuit boards with evenly arranged electronic components cooled by forced convective heat transfer were simulated, and typical results were reported and discussed. It is clear that, such a computer program for the thermal analysis of electronic circuit boards is effective and enables the user to choose any arbitrary arrangement of components on the ECB as well as different values of all design parameters. The program can serve as a powerful tool either for checking the performance of an existing ECB or for sensitivity analysis in designing the packaging of new electronic circuit boards.

: As electronic products become much smaller, a limiting factor in the reduction of product size has been the size of electronic components which make up the product. The leads of the current electronic components are inserted onto a printed circuit board through holes. Due to the use of wire leads, it becomes more difficult to decrease the size of the components. A new method was created to mount components directly to the surface of the printed circuit board. This new technique is surface mount technology. A concern over the use of this is experienced by the military. Since the leads are not inserted through the board and crimped before soldering as conventional components are mounted, there is some regard as to whether the components can be mounted securely to the board. Due to the high forces that many munitions experience when dispensed, it is imperative that the electronic components be soldered to the circuits boards so they will not slip out of place or fall from the board. The military also requires many munitions to lie dormant in storage warehouses for up to 20 years. When the munition is needed, it must perform reliably. Little work has been done to study the effects of this long-term storage on these surface mount devices particularly the ability of different soldering techniques used to attach surface mount components to printed circuit boards to withstand damaging effects of long-term storage.... Surface mount technology, Solderability, Wave soldering, Reflow soldering, Conductive adhesive curing, Long-term storage, Accelerated age testing.

With more consumer products moving towards environmentally friendly packaging, making solder Pb-free has become an urgent task for electronics assemblies. Solder joints are responsible for both electrical and mechanical connections. Solder joint does not have adequate ductility to ensure the repeated relative displacements due to the mismatch between expansion coefficients of the chip carrier and the circuit board. Materials behavior of solder joints involves a creep–fatigue interaction, making it a poor material for mechanical connections. The reliability of solder joints of electronics components has been found playing a more important role in service for microelectronics components and micro-electro-mechanical systems. So many researchers in the world investigated reliability of solder joints based on finite element simulation and experiments about the electronics devices, such as CR, QFP, QFN, PLCC, BGA, CSP, FCBGA and CCGA, which were reviewed systematically and extensively. Synchronously the investigation on reliability of solder joints was improved further with the high-speed development of lead-free electronic packaging, especially the constitutive equations and the fatigue life prediction equations. In this paper, the application and research status of constitutive equations and fatigue life prediction equations were reviewed, which provide theoretic guide for the reliability of lead-free solder joints.

Since most accelerator control system circuit boards reside in a commercial bus architecture, such as CAMAC or VMEbus, a computerized test station is needed for exercising the boards. This test station is needed for the development of newly designed prototypes, for commissioning newly manufactured boards, for diagnosing boards which have failed in service, and for long term testing of boards with intermittent failure problems. WindoWorks was created to address these needs. It is a flexible program which runs on a PC compatible computer and uses a PC to bus crate interface. WindoWorks was designed to give the user a flexible way to test circuit boards. Each test is incapsulated into a window. By bringing up several different windows the user can run several different tests simultaneously. The windows are sizable, and moveable. They have data entry boxes so that the test can be customized to the users preference. The windows can be used in conjunction with each other in order to create supertests. There are several windows which are generic. They can be used to test basic functions on any VME (or CAMAC) board. There are other windows which have been created to test specific boards. New windows for testing specific boards can be easily created by a Pascal programmer using the WindoWorks framework. >

The current research highlights regarding future low-dielectric resins for circuit boards lie in their recyclability and pattern ability. In the present work, we put forward a new idea to simultaneously achieve the recyclability and pattern ability of low-dielectric resins in circuit board. In detail, a series of low-dielectric vitrimers were prepared by copolymerization of fluorinated monomers followed by employing imine cross-linked network. By incorporating fluorine-contained units, the dielectric constant of the vitrimers reached to ∼2.4, while preserving high mechanical strength around 33 MPa. Moreover, after reprocessing three times, the dielectric constants of the PFS-imines remained almost unchanged and 89% of original mechanical strength was recovered. Owing to the increased chain relaxation, PFS-imines can be multiply patterned by directly imprinting at the temperature above Tv . Furthermore, the pattern of PFS-imines is removable and reformed, which may be attributed to their reprocessability. Thus, PFS-imine exhibits pattern ability and recyclability, making it particularly suitable for applications in electronic packaging and circuit boards, compared with that of conventional low-dielectric resins.

The unique advantages of confocal microscopy are used to explore four cases of interest: (i) voids in solder (depth and surface texture determined), (ii) steam vs ambient aged solder coupons (significant differences detected), (iii) integrated circuit construction (sub‐surface contamination by µm‐size particles observed) and (iv) circuit boards and solder pads (non‐destructive optical sectioning through no‐wash flux layers). It is shown that confocal microscopy strongly complements SEM (scanning electron microscopy); SEM alone presents an incomplete description of a solder surface and in fact can sometimes produce misleading results.

A flexible control system for scanning laser ophthalmoscopes is described that is quick and simple to configure, easily modified or adapted, and containing many useful features. The system facilitates adjustment of several parameters to account for changes to the scan position, ambient light and temperature, including both optical and electronic components, which is otherwise difficult and time-consuming to perform. The system is portable and uses custom-designed printed circuit boards. All system parameters, such as focus, scan rate,scan depth and stereo control can be digitally controlled from a computer via a single serial port. Custom software allows changes to any system parameters by simply sending the required control data to the rack. The circuit boards in the system are multilayer,incorporating good ground-plane techniques to minimize noise, programmable logic and semicustom logic for low cost and compact size, and microcontrollers with embedded firm ware for flexible operation. Retinal images demonstrate that the system performs well.

DC/DC converters are widely used to produce various power supply voltages required for various electronic components on a board. Though DC/DC converter is more efficient than the linear regulator is, however, the switching noise becomes larger with the increase of the switching frequency. In particular, ringing noises at the sharp rising edge of the switching waveform generated by the effect of the parasitic inductance becomes a serious issue. This noise spreads out to the whole circuit board, and then generates electromagnetic interference (EMI), which often causes a malfunction of the electronic systems. In this paper, the methods to accurately reproduce the switching waveforms and to reduce ringing noises and resulting EMI from DC/DC converters were investigated. For this purpose, several evaluation boards were designed, and total electrical model was constructed by taking into account the parasitic inductances of traces on a board. First, frequency-domain analysis for the switching loop of the DC/DC converters was executed to find the optimum condition to suppress ringing noise effectively. Next, time-domain simulation was executed by considering the recovering time of MOS reverse current, which is not provided from device vendors. Finally, measured switching waveforms were well correlated with the simulated ones, and the optimal condition to suppress the ringing noise.

The focus of this chapter is to review the literature on flexible and stretchable electronics fabricated using gallium-based liquid metal alloys. Over the past few decades, gallium-based liquid metal alloys have gathered growing interest due to their application in various soft electronic applications as conductive yet fluidic metals that can be patterned at room temperature. Gallium-based liquid metal alloys have a melting point at or near room temperature and offer a low toxicity as opposed to the conventional liquid metal – mercury, in addition to having negligible vapor pressure and low viscosity. The surface of these metals reacts rapidly with oxygen in air to form a thin surface oxide ‘skin’ that allows these liquids to be deposited in several useful stable shapes despite the destabilizing effects of a large surface tension and gravity. There are several methods to pattern these liquid metals – traditionally using lithography-based subtractive approaches, and unconventionally using 3D printing and other additive techniques. Gallium-based liquid metal alloys have been used for fabricating various electronic structures such as ultrastretchable and self-healing wires, interconnects, and stretchable antennas. Integrating these components, many electronic components have been built such as optical and soft memory devices, reconfigurable circuits, soft diodes, microfluidic pumps, soft strain sensors, capacitors, and circuit boards.