Effect of Drop Angle Variation and Restraint Mechanisms on Surface Mount Electronics Under High G Shock

The paper proposed an alternative optical metrology to classical methods (strain gauge measurements and numerical simulation) for strain determination on printed circuit board (PCBs) due to thermal loads. The digital image correlation (DIC) technique was employed to record the strain distribution in some particular areas of the PCB. A thermal load was applied using a heating chamber, and the measurements were performed at four different temperature steps (25 °C, 50 °C, 85 °C and 120 °C). An increase in the principal strains with temperature was observed. For validation, the principal strains on the PCB obtained with DIC were compared with the values from gauge strain measurements and numerical simulation. The conclusions highlighted that DIC represents a technique with potential for strain measurement caused by thermal deformation, with the advantages of full field measurement, less preparation of the surface and good accuracy.

Electronic components (EC) detection is relevant for Printed Circuit Board (PCB) manufacturing, quality inspection, and assurance (cyber-security). Moreover, at end-of-life electronic devices, the PCBs become Waste PCBs (WPCBs), the primary source of high-value materials in electronic waste. However, the recycling process is challenging because of the WPCB’s high composition diversity. EC detection in WPCBs can reduce the uncertainty about WPCBs composition and help select a better recycling process. Nevertheless, large fully-annotated datasets for the PCB domain are available at a high cost. For WPCBs, there is only one publicly available dataset, the PCB-DSLR, and it is partially labeled. As for PCBs, the FICS-PCB dataset is available. However, it contains images of modern and clean PCBs, all in good condition, while the first has broken and dirty parts. Thus, we propose a self-training strategy for object detection algorithms without needing a fully labeled dataset. In the strategy, the YOLOv5 model is used to detect the eight types of electronic components present in FICS-PCB in PCB-DSLR, which initially has labels only for integrated circuits. The process occurs through the interaction between a teacher model, trained with the FICSPCB data, and a student model, which is trained by joining the FICS-PCB data and the teacher-generated labels for PCB-DSLR. The results show that the student model performs better in the electronic components detection task, obtaining greater precision and sensitivity when compared to the teacher model. Since we are dealing with partially labeled data, we provide a low-dimensional representation of the detections of both models using t-SNE.

High strain rate constitutive behavior of SAC105 and SAC305 leadfree solder during operation at high temperature

Printed circuit board (PCB) assembly lines consist of a number of different machines for mounting electronic components onto PCBs. While high-speed placement machines are employed to assemble standard components, so-called fine-pitch placement machines are used to mount complex electronic components with high precision and by use of specific nozzles. In this paper, we investigate a typical mass production environment where a single type of PCB is assembled in a line comprising high-speed as well as high-precision placement machines. The PCB assembly line balancing problem consists of assigning component feeders, each holding a specific electronic component type, and the corresponding placement operations to machines in the line so as to minimize the assembly cycle time. To solve this problem, a two-stage solution procedure based on genetic algorithm (GA) is proposed. In the first stage, component feeders are assigned to the placement machines with the objective of balancing the workload within the assembly line. A number of candidate solutions are then transmitted to the second stage, where specific machine optimization algorithms are applied to determine the feeder-slot assignment in the component magazine of the machines and the placement sequence of the various components. As a result, fine-tuned placement operation times are achieved which reflect the individual operation mode and the actual component setup of the placement machines. Finally, from the candidate solutions the one which minimizes the actual PCB assembly time is selected.

Electronics may be subjected to shock, vibration, and drop-impact during shipping, handling and during normal usage. Measurement of transient dynamic deformation of the electronics assemblies during the shock and vibration can yield significant insights in understanding the occurrence of failure modes and the development of failure envelopes. Failure-modes include solder-joint failures, pad cratering, chip-cracking, copper trace fracture, and underfill fillet failures. Previous researchers have measured the transient-dynamics of board assemblies with high-speed imaging in conjunction with high-speed image analysis for measurement of relative displacement, angle, velocity, and acceleration [Lall 2006, Che 2006]. In addition, high-speed data-acquisition systems with discrete strain gages have been used for measurements of transient strain [Lall 2004, 2005, Liang 2005] and with accelerometers for measurement of transient acceleration [Dunford 2004, Goyal 2000, Seah 2005]. Development of accurate models requires better understanding of full-field strain deformation in board assemblies. In this paper, the use of digital image correlation (DIC) with ultra high-speed imaging has been used for full-field measurement of transient strain in various board assemblies subjected to shock in various orientations. Measurements have been taken on both the package and the board side of the assemblies. Accuracy of high-speed optical measurement has been compared with that from discrete strain gages. Package architectures examined include flex ball-grid arrays, tape-array ball-grid arrays, and metal lead-frame packages. Explicit finite-element models have been developed and correlated with experimental data. Models developed include, smeared property models, Timoshenko-beam models, and explicit sub-models. The solder strains have been computed from the explicit finite element models for life prediction in shock.

Inspection of defects in the printed circuit boards (PCBs) has both safety and economic significance in the 4.0 industrial manufacturing. Nevertheless, it is still a challenging problem to be studied in-depth due to the complexity of the PCB layouts and the shrinking down tendency of the electronic component size. In this paper, a real-time automated supervision algorithm is proposed to test the PCBs quality among different scenarios. The density of the PCBs layout and the complexity on the surface are analyzed based on deep learning and image feature extraction algorithms. To be more detailed, the ORB feature and the Brute-force matching method are utilized to match perfectly the input images with the PCB templates. After transferring images by aiding the RANSAC algorithm, a hybrid method using modern computer vision algorithms is developed to segment defective areas on the PCBs surface. Then, by applying the enhanced Residual Network –50, the proposed algorithm can classify the groove defects on the surface mount technology electronic components which minimum size up to 1x3 mm. After the training process, the proposed system is capable to categorize various types of overproduced, recycled, and cloned PCBs. The speed of the quality testing operation maintains at a high level with an average precision rate up to 96.29 % in case of good brightness conditions. Finally, the computational experiments demonstrate that the proposed system based on deep learning can obtain superior results and it outperforms several existing works in terms of speed, precision, and robustness

Flexible electronics and sensors are a key enabling element for the realization of wearables and geometry adaptive devices needed to follow current trends such as the Internet of things or Industry 4.0. Within this paper, we present a new and flexible packaging platform by the fabrication of an ultra-thin and highly flexible printed circuit board (PCB).The thermoplastic polymer Parylene, which combines a variety of unique properties such as optical transparency, biostability and biocompatibility according to ISO 10993, thermal stability as well as low permeability for gases and water, was used as the base for the new PCB.Particularly, its mechanical properties, especially the absence of intrinsic stresses, as well as its low Young’s modulus and good bendability are advantageous when using Parylene films as a free-standing substrate for flexible applications. The chemical inertness of Parylene against all common acids, bases and solvents ensures its compatibility with established standard microsystem technologies.For the realization of ultra-thin flexible PCBs, Parylene was used as a substrate as well as for the encapsulation and protection layer, respectively. Furthermore, Parylene was the dielectric between the metallic conductive layers. These redistribution layers (RDL) were deposited and patterned by standard microsystem technologies, such as sputtering, lithography and wet chemical etching. Hence, structure sizes of down to 10 µm were successfully realized. Different metals, such as gold, copper, and aluminum were tested for the RDL. Alternatively, printing technologies such as screen printing and aerosol jet printing were successfully demonstrated for the if conductive silver layerse. The electrical connection between the various RDL was of special interest throughout the study and was realized by etching vertical vias through the Parylene using oxygen plasma. Due to the low total thickness of the flexible Parylene PCB of 20 µm or even less, the obtained vias through the Parylene feature an advantageous low aspect ratio. For the contact formation through the vias, different methods were investigated, e. g. sputtering, printing and electrochemical deposition.Finally, the fabricated flexible Parylene PCB were characterized with respect to their bendability and electrical properties. Doing so, the resistivity and capacitance were measured as well as the frequency response between 20 kHz and 500 MHz. Particularly, for frequencies below 1 MHz the realized flexible Parylene PCBs show a good electrical performance.A third function of Parylene with respect to the realization of an ultra-thin and flexible PCB is its usage as a barrier or capping layer. Doing so, new approaches such as embedding electronic or sensor components in the flexible PCB can be enabled. Other integration technologies such as wire bonding, printing or gluing were investigated with respect to their usability for the new flexible PCB as well. Besides, also the direct fabrication of sensors on the Parylene flexible PCB was successfully demonstrated by the realization of a flexible potentiometric pH sensor.The presented new type of ultra-thin PCB is a versatile platform for the realization of flexible electronics, sensors and devices. Due to its biocompatible properties, the flexible Parylene PCB can be used for medical applications but also for the integration of MEMS, chemical sensors and optical components, respectively. Doing so, it enables the realization of smart systems for wearable applications and their integration into light weight constructions. Within this paper, the concept of this new approach, the respected fabrication and integration technologies as well as possible applications are presented in detail. Figure 1

Printed Circuit Boards (PCB) are most important parts of nearly all modern electronic devices meant for mechanical support to the electronic components and to create the conductive paths to meet the desired circuit or to electrically connect the electronic components. Most commonly PCB’s are based on a laminate of multiple layers of weaved glass fiber and epoxy with copper on one or both sides of the PCB to form the electrical conductors. PCB material selection shall be undertaken with core and knowledge for electrical necessities of a given piece of equipment.In this paper, keeping fundamental frequency as a reference the equivalent mechanical properties of PCBs are being estimated by FE analysis, testing and calculations. Five number of PCB’s with different thickness, dimension and copper layers are considered for the estimation and comparison of mechanical properties. The relative mechanical properties are varied, different types of boundary conditions and damping values have been employed for the assessment of mechanical properties, mainly young’s modulus and possion’s ratio. These equivalent mechanical property values are documented and utilized as a reference.The damping values has been varied in sine response analysis to correlate the dynamic behavior/signature of analysis and testing results and which is not discussed in this paper.

Co-pyrolysis of printed circuit boards (PCBs): A review on current research and future prospects

This paper describes several low‐cost methods for fabricating flexible electronic circuits on paper. The circuits comprise i) metallic wires (e.g., tin or zinc) that are deposited on the substrate by evaporation, sputtering, or airbrushing, and ii) discrete surface‐mountable electronic components that are fastened with conductive adhesive directly to the wires. These electronic circuits—like conventional printed circuit boards—can be produced with electronic components that connect on both sides of the substrate. Unlike printed circuit boards made from fiberglass, ceramics, or polyimides, however, paper can be folded and creased (repeatedly), shaped to form three‐dimensional structures, trimmed using scissors, used to wick fluids (e.g., for microfluidic applications) and disposed of by incineration. Paper‐based electronic circuits are thin and lightweight; they should be useful for applications in consumer electronics and packaging, for disposable systems for uses in the military and homeland security, for applications in medical sensing or low‐cost portable diagnostics, for paper‐based microelectromechanical systems, and for applications involving textiles.

: 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.

Waste electrical and electronic equipment is a significant source of material that can contribute to reduce environmental impacts associated to extraction and discard stages; therefore, it is necessary to develop efficient recycling processes for components such as Printed Circuit Boards (PCBs). Current methods for PCB recycling may be optimized by previous disassembly of such components. In the work reported here, an especially designed and manufactured centrifuge was employed to disassemble PCBs from power supplies (PS-PCBs) and memory chips (ME-PCBs) of personal computers (PCs), through combination of hot air flow and centrifugal force. The results showed that the device was capable of separating tin solder, electronic components (EC) and PCB substrate, as long as hazardous components and plastic parts are previously removed. A scanning electron microscope (SEM) with combined energy dispersive X-ray (EDX) analyzer showed that the recovered solder had under 3%wt of contamination; therefore, it can be employed in the production of new soldering material, replacing the more commonly used solder dross. EC recovery rates were up to 94%wt for PS-PCBs and 32%wt for ME-PCBs, and once components such as inductors were not visibly damaged in the process, possibilities of reusing recovered components may be further investigated.

<div class="section abstract"><div class="htmlview paragraph">Thermal management in electric vehicles plays a significant role, in keeping all the electronic components under the safe operating region for lower power dissipation, higher efficiency and this increases the component’s life. Based on the increase in range of e-vehicles, the power dissipation requirement had increased from OEMs. In addition, the compact size, weight, and limited cooling technique have increased the thermal management requirements in printed circuit boards (PCB). In a passive cooling technique, high thermally conductive metal with plastic overmould concept in PCB cover or housing will have a huge advantage in transferring the heat from e-components to keep within operating temperature conditions [<span class="xref">1</span>, <span class="xref">6</span>]. The advantage of alumina or mica metal insert is that it has higher thermal conductivity and electrical resistivity, which helps to dissipate the heat at a higher level when it is locally in contact with hot spot regions of the PCB. This concept also helps to reduce the mass of the products by having plastic overmould [<span class="xref">3</span>] housing instead of a die-cast housing. This passive cooling technique will boost thermal management in PCB e-components, irrespective of all vehicle applications [<span class="xref">1</span>, <span class="xref">4</span>].</div></div>

As the application of power electronic components in renewable and green energy technologies continues to increase, there is an increasing trend in the utilization of higher voltage and frequency levels. This shift may result in more frequent partial discharge (PD) phenomena that can accelerate the degradation of insulation materials and shorten the lifespan of the components. Therefore, it is critical to ensure the reliability and durability of these components. This study investigated the effects of voltage magnitude and frequency on the PD and insulation degradation of printed circuit board (PCB) samples. Five different test samples were fabricated using a PCB as the substrate and an epoxy resin as the insulating coating. Two distinct testing configurations were employed: one for assessments based on a commercial frequency (60 Hz) and the other for assessments based on a high frequency (600 Hz). This study examined the behavior of PD within PCBs and the resulting insulation deterioration. The results demonstrated that all the samples exhibited significantly lower PD inception voltages (PDIV) at high frequencies compared with those at the commercial frequency. Specifically, the maximum decrease in the PDIV observed was 5 kV, while the minimum reduction was 3.3 kV. These findings highlight the critical impact of frequency on the PD behavior and underscore the importance of understanding these effects to enhance the reliability of electronic components in high-frequency applications.

Electronic equipment is exposed to rough vibrations throughout its life cycle. Electronic components can be damaged by these vibrations and could lead to device failure. The conventional Printed Circuit Boards (PCBs) that form the foundation of numerous electronic devices are predominantly constructed from copper films that are bound to fiber epoxy laminates, such as FR4, which is composed of glass fibers, and FR1, which is composed of paper. Being biodegradable makes cellulose a more sustainable choice. Nonetheless, it is imperative to uphold performance criteria, and this work aims to contribute to this assessment. Using simulation studies, we compare the behavior of these two PCBs under vibrational stress. The finite element analysis (FEA) of the vibrations for the PCB samples was modelled using the Ansys software. The FEA simulations show that both types of PCBs have similar movements and accelerations at certain places on the board.