In Case You Missed It

3-D Printing

“Iterative Printing of Bulk Metal and Polymer for Additive Manufacturing of Multi-Layer Electronic Circuits”

Authors: Zeba Khan, et. al.

Abstract: In pursuing advancing additive manufacturing (AM) techniques for 3-D objects, this study combines AM techniques for bulk metal and polymer on a single platform for one-stop printing of multilayer 3-D electronic circuits with two novel aspects. The first innovation involves the embedded integration of electronic circuits by printing low-resistance electrical traces from bulk metal into polymer channels. Cross-section grinding results reveal (92±5)% occupancy of electrically conductive traces in polymer channels despite the different thermal properties of the two materials. The second aspect encompasses the possibility of printing vertical bulk metal vias up to 10mm in height with the potential for expansion, interconnecting electrically conductive traces embedded in different layers of the 3-D object. The work provides comprehensive 3-D printing design guidelines for successfully integrating fully embedded electrically conductive traces and the interconnecting vertical bulk metal vias. A smooth and continuous workflow is also introduced, enabling a single-run print of functional multilayer embedded 3-D electronics. The design rules and the workflow facilitate the iterative printing of two distinct materials, each defined by unique printing temperatures and techniques. Observations indicate that conductive traces using molten metal microdroplets show a 12-fold reduction in resistance compared to nanoparticle ink-based methods, meaning this technique greatly complements multi-material additive manufacturing (MM-AM). The work presents insights into the behavior of molten metal microdroplets on a polymer substrate when printed through the MM-AM process. It explores their characteristics in two scenarios: deposited side-by-side to form conductive traces and deposited out-of-plane to create vertical bulk metal vias. The innovative application of MM-AM to produce multilayer embedded 3-D electronics with bulk metal and polymer demonstrates significant potential for realizing the fabrication of free-form 3-D electronics. (npj Advanced Manufacturing, August 2024, https://doi.org/10.1038/s44334-024-00001-0)

 

Flexible Electronics

“Stretchable Arduinos Embedded in Soft Robots”

Authors: Stephanie J. Woodman, et al.

Abstract: To achieve real-world functionality, robots must be able to carry out decision-making computations. Soft robots stretch, however, and therefore need a solution other than rigid computers. Examples of embedding computing capacity into soft robots currently include appending rigid printed circuit boards to the robot, integrating soft logic gates, and exploiting material responses for material-embedded computation. Although promising, these approaches introduce limitations such as rigidity, tethers or low logic gate density. The field of stretchable electronics has sought to solve these challenges, but a complete pipeline for direct integration of single-board computers, microcontrollers, and other complex circuitry into soft robots has remained elusive. The authors present a generalized method to translate any complex two-layer circuit into a soft, stretchable form. This enabled the creation of stretchable single-board microcontrollers (including Arduinos) and other commercial circuits (including SparkFun circuits), without design simplifications. As demonstrations of the method’s utility, the authors embedded highly stretchable (>300% strain) Arduino Pro Minis into the bodies of multiple soft robots. This makes use of otherwise inert structural material, fulfilling the promise of the stretchable electronic field to integrate state-of-the-art computational power into robust, stretchable systems during active use. (Science Robotics, September 2024, https://doi.org/10.1126/scirobotics.adn6844)

 

Quality Assurance

“PCB Plug-In Solder Joint Defect Detection Method Based on Coordinated Attention-Guided Information Fusion”

Authors: Wenbin Chen, et. al.

Abstract: Printed circuit boards (PCBs) are the foundational component of electronic devices, and the detection of PCB defects is essential for ensuring the quality control of electronics products. Aiming at the problem that existing PCB plug-in solder defect detection algorithms cannot meet the requirements of high precision, low false alarm rate and high speed at the same time, this work proposes a method based on spatial convolution pooling and information fusion. First, on the basis of YOLOv3, an attention-guided pyramid structure is used to fuse context information, and multiple convolutions of different sizes are used to explore richer high-level semantic information. Second, a coordinated attention network structure is introduced to calibrate the fused pyramidal feature information, highlighting the important feature channels, and reducing the adverse impact of redundant parameters generated by feature fusion. Finally, the ASPP (atrous spatial pyramid pooling) structure is implemented in the original Darknet53 backbone feature extraction network to acquire multi-scale feature information of the detection targets. With these improvements, the average detection accuracy of the enhanced network has been elevated to 96.43% from 94.45%. This experiment shows that the improved network is more suitable for PCB plug-in solder defect detection applications. (Scientific Reports, August 2024, https://doi.org/10.1038/s41598-024-70100-7)

 

Signal Integrity

“High-Speed Signal Optimization at Differential Vias in Multilayer Printed Circuit Boards”

Authors: Wen-Jie Xu, et. al.

Abstract: The number of printed circuit board layers increases with increases in data transmission rates, and the signal integrity (SI) of high-speed digital systems cannot be ignored. Introducing vertical interconnect accesses (vias) in PCBs can realize the electrical connection between the top layer and innerlayers, however, vias represent one of the most important reasons for discontinuity between PCBs and package. In this work, a new optimization scheme for a differential via stub is proposed, with 3-D full-wave numerical simulation used for modeling and simulation. Results show that this scheme optimizes the return loss and insertion loss while making the signal eye diagram more ideal, which can improve the transmission effect of high-speed signals. (Electronics, August 2024, https://doi.org/10.3390/electronics13173377)