In Case You Missed It
Component Placement
“SimPLE, A Visuotactile Method Learned in Simulation to Precisely Pick, Localize, Regrasp, and Place Objects”
Authors: Maria Bauza, et. al.
Abstract: Existing robotic systems have a tension between generality and precision. Deployed solutions for robotic manipulation tend to fall into the paradigm of one robot solving a single task, lacking “precise generalization,” or the ability to solve many tasks without compromising on precision. This work explores solutions for precise and general pick-and-place. In precise pick-and-place, or kitting, the robot transforms an unstructured arrangement of objects into an organized arrangement, which can facilitate further manipulation. The authors propose SimPLE (Simulation to Pick Localize and placE) as a solution to precise pick-and-place. SimPLE learns to pick, regrasp and place objects given the object’s computer-aided design model and no prior experience. The authors developed three main components: task-aware grasping, visuotactile perception, and regrasp planning. Task-aware grasping computes affordances of grasps that are stable, observable, and favorable to placing. The visuotactile perception model relies on matching real observations against a set of simulated ones through supervised learning to estimate a distribution of likely object poses. Last, the authors computed a multistep pick-and-place plan by solving a shortest-path problem on a graph of hand-to-hand regrasps. On a dual-arm robot equipped with visuotactile sensing, SimPLE demonstrated pick-and-place of 15 diverse objects. The objects spanned a range of shapes, and SimPLE achieved successful placements into structured arrangements with 1mm clearance more than 90% of the time for six objects and more than 80% of the time for 11 objects. (Science Robotics, June 2024, https://doi.org/10.1126/scirobotics.adi8808)
Defect Detection
“Attentive Context and Semantic Enhancement Mechanism for Printed Circuit Board Defect Detection with Two-Stage and Multi-Stage Object Detectors”
Authors: Twahir Kiobya, et. al.
Abstract: Several methods have been proposed to detect PCB defects. Detecting significantly smaller and visually unrecognizable defects has been a long-standing challenge, however. The existing two-stage and multi-stage object detectors that use one layer of the backbone, such as Resnet’s third layer or fourth layer, suffer from low accuracy, and those that use multilayer feature maps extractors, such as Feature Pyramid Network (FPN), incur higher computational cost. Founded by these challenges, the authors propose a robust, less computationally intensive, and plug-and-play attentive context and semantic enhancement module (ACASEM) for two-stage and multi-stage detectors to enhance PCB defect detection. This module consists of two main parts, namely adaptable feature fusion and attention sub-modules. The proposed model, ACASEM, takes in feature maps from different layers of the backbone and fuses them in a way that enriches the resulting feature maps with more context and semantic information. The authors test their module with state-of-the-art two-stage object detectors, faster R-CNN and double-head R-CNN, and with a multi-stage cascade R-CNN detector on DeepPCB and augmented PCB defect datasets. Empirical results demonstrate improvement in the accuracy of defect detection. (Nature, August 2024, https://doi.org/10.1038/s41598-024-69207-8)
Microwave Circuits
“Frequency Shift in Microwave Circuits Manufactured with Circuit Board Plotters: Case Study of a Parallel Coupled Lines Filter”
Authors: Luigi Ferro and Emanuele Cardillo
Abstract: Board milling is one of the most widespread methods for manufacturing printed circuit boards from low frequencies to the microwave and millimeter wave range. In this work, the detrimental effect of defects typical of printed circuit board plotters has been investigated. In detail, a systematic frequency shift in the circuit performance has been observed both in terms of S21 and S11 parameters. The performance degradation has been analyzed and attributed to the inaccurate milling depth, which is typical of many plotters, particularly for less recent models. After the conductor removal step, the unwanted milling of dielectric material changes the electrical properties of the microstrip structure, in turn affecting the circuit performance. This circumstance has been investigated by means of electromagnetic simulations performed on the real case study of a parallel coupled lines filter. Therefore, a filter prototype has been realized and measured to confirm the simulated results. (Electronics, July 2024, https://doi.org/10.3390/electronics13153100)
Solder Alloys
“Intermetallic Compounds in Solder Alloys: Common Misconceptions”
Authors: David Hillman, et. al.
Abstract: Intermetallic compounds (IMC) or intermediate phases are formed between two or more metallic elements in many metal alloy systems. During soldering, an IMC is formed at the soldered interface as the molten solder reacts with an element in the substrate. IMCs also can form within the bulk solder as the joint solidifies. IMCs have critical roles in the solder joint quality and reliability. Unlike most metal alloys, an intermetallic compound typically has a fixed stoichiometry and is in variance with the conventional phases or constituents in the metal system (e.g., alpha and beta). IMCs have a different crystal structure than any of their constituents and some but never all the characteristics and properties of their constituents. Ductility is an important solder joint property, and the low intrinsic ductility of IMCs is associated with brittle behavior and reliability risk in service. A review of published solder field failures shows little evidence that IMC properties or IMC evolution under service conditions reduce solder joint reliability, however. Most IMC-induced solder joint failures are found to result from incorrect material specification or uncontrolled soldering processes. This work describes the IMCs that occur typically in eutectic Sn63Pb37 solder and near-eutectic SAC 305 or other tin-based Pb-free solder alloys, including how they impact solder joint reliability. The work also describes the potential impact of IMCs on the solder joint reliability for the newest generation of Pb-free high-performance solder alloys. (Journal of Surface Mount Technology, July 2024, https://doi.org/10.37665/pmtrnw39)
