In Case You Missed It
Defect Detection
“MDD-DETR: Lightweight Detection Algorithm for Printed Circuit Board Minor Defects”
Authors: Jinmin Peng, et. al.
Abstract: PCBs (printed circuit boards) are the core components of modern electronic devices, and inspecting them for defects will have a direct impact on the performance, reliability and cost of the product. However, the performance of current detection algorithms in identifying minor PCB defects (e.g., mouse bites and spurs) requires improvement. This work presents the MDD-DETR algorithm for detecting minor defects in PCBs. The backbone network, MDDNet, is used to efficiently extract features while significantly reducing the number of parameters. Simultaneously, the HiLo attention mechanism captures both high- and low-frequency features, transmitting a broader range of gradient information to the neck. Additionally, the proposed SOEP neck network effectively fuses scale features, particularly those rich in small targets, while INM-IoU loss function optimization enables more effective distinction between defects and background, further improving detection accuracy. Experimental results on the PCB_DATASET show that MDD-DETR achieves a 99.3% mAP, outperforming RT-DETR by 2% and reducing parameters by 32.3%, thus effectively addressing the challenges of detecting minor PCB defects. (Electronics, October 2024, https://doi.org/10.3390/electronics13224453)
Electroplating
“Effect of Matte-Sn Electroplating Parameters on the Thermo-Mechanical Reliability of Lead-Free Solder Joints”
Authors: Abhilaash Ajith Kumar, et. al.
Abstract: Most of the Cu/Cu alloy lead-frames of electronic components used for automotive applications contain electroplated matte-Sn terminal finish to improve the wettability of Sn-based Pb-free solders during reflow soldering process. When solder joints are subjected to combined thermal and mechanical cyclic loading, the influence of matte-Sn electroplating parameters can lead to early and brittle failure of the solder joint. To test this hypothesis, a factorial design of experiments (DoE) has been conducted with LFPAK-MOSFET (hereafter referred to as LFPAK) components plated with different matte-Sn electroplating parameters and reflow soldered with two solder alloys (SAC 305 and Innolot). The LFPAK solder joints were then subjected to thermo-mechanical in-phase cyclic loading under different strain amplitudes. No electrical measurement is done to eradicate the effect of electrical current on the solder joint. The response to the DoE is the crack percentage obtained in the LFPAK solder joints after 1000 and 2000 cycles. Innolot solder joints exhibited lower crack percentages than SAC 305. The level of organic additives in the electroplating process of matte-Sn influences the failure mode of the solder joint. Microstructural investigation attributes the nature of failure to the morphology of the (Cu,Ni)6Sn5 IMC phase that forms on the component side of the solder joint. (Journal of Surface Mount Technology, April 2024, https://doi.org/10.37665/smt.v37i1.46)
Flexible Circuits
“Ambient Printing of Native Oxides for Ultrathin Transparent Flexible Circuit Boards”
Authors: Minsik Kong, et. al.
Abstract: Metal oxide films are typically deposited at elevated temperatures by using slow, vacuum-based processes. The authors printed native oxide films over large areas at ambient conditions by moving a molten metal meniscus across a target substrate. The oxide gently separates from the metal through fluid instabilities that occur in the meniscus, leading to uniform films free of liquid residue. The printed oxide has a metallic interlayer that renders the films highly conductive. The metallic character of the printed films promotes wetting of trace amounts of evaporated gold that would otherwise form disconnected islands on conventional oxide surfaces. The resulting ultrathin (<10nm) conductors can be patterned into flexible circuits that are transparent, mechanically robust and electrically stable, even at elevated temperatures. (Science, August 2024, https://doi.org/10.1126/science.adp3299)
Soft Electronics
“Soft Electronic Vias and Interconnects through Rapid Three-Dimensional Assembly of Liquid Metal Microdroplets”
Authors: Dong Hae Ho, et. al.
Abstract: The development of soft electronics requires methods to connect flexible and stretchable circuits. With conventional rigid electronics, vias are typically used to electrically connect circuits with multilayered architectures, increasing device integration and functionality. Creating vias using soft conductors leads to additional challenges, however. Here the authors show that soft vias and planar interconnects can be created through the directed stratification of liquid metal droplets with programmed photocuring. Abnormalities that occur at the edges of a mask during ultraviolet exposure are leveraged to create vertical stair-like architectures of liquid metal droplets within the photoresin. The liquid metal droplets in the uncured (liquid) resin rapidly settle, assemble and then are fully cured, forming electrically conductive soft vias at multiple locations throughout the circuit in a parallel and spatially tunable manner. The authors’ three-dimensional selective stratification method can also form seamless connections with planar interconnects, for in-plane and through-plane electrical integration. (Nature Electronics, October 2024, https://doi.org/10.1038/s41928-024-01268-z)
