In order to study the role of printed circuit board(PCB)in high-power LED heat dissipation,a simple model of high-power LED lamp was designed.According to this lamp model,some thermal performances such as thermal resi...In order to study the role of printed circuit board(PCB)in high-power LED heat dissipation,a simple model of high-power LED lamp was designed.According to this lamp model,some thermal performances such as thermal resistances of four types of PCB and the changes of LED junction temperature were tested under three different working currents.The obtained results indicate that LED junction temperature can not be lowered significantly with the decreasing thermal resistance of PCB.However,PCB with low thermal resistance can be matched with smaller volume heat sink,so it is hopeful to reduce the size,weight and cost of LED lamp.展开更多
The quality of printed circuit board(PCB)micro-hole processing directly determines the stability of the inner and outer circuit connections.Micro-hole drilling technology is a typical method for PCB micro-hole process...The quality of printed circuit board(PCB)micro-hole processing directly determines the stability of the inner and outer circuit connections.Micro-hole drilling technology is a typical method for PCB micro-hole processing.The problem of optimal control of its drilling force is one of the main factors affecting the quality of micro-hole machining.To address this problem,the thrust forces and torques in PCB drilling were first modeled and analyzed,and the corresponding prediction models were established.The drilling force analysis was carried out through the micro-hole drilling experiment,the specific cutting energy under different feed rates was calculated,the influence of the size effect was clarified,and the accuracy of the prediction model was verified.The result shows that during the drilling of glass fiber cloth,changes in the material removal mechanism are induced as the feed per revolution is varied.When the feed per revolution is less than the tool edge radius,the glass fiber is not cut by the main cutting edge,but is crushed and broken.When the feed per revolution is greater than the radius of the tool edge,the glass fiber is cut by the main cutting edge.At the same time,the established analytical model can accurately reflect the influence of the size effect on the drilling torque in PCB micro-hole drilling,and the error is within 10%.This method has certain practical application value in controlling PCB micro hole processing quality.展开更多
Electronic scrap, especially wasted printed circuit boards (PCBs), is regarded as an environmental challenge. At present, the physical separation is thought to be the environmental friendly and economical method of tr...Electronic scrap, especially wasted printed circuit boards (PCBs), is regarded as an environmental challenge. At present, the physical separation is thought to be the environmental friendly and economical method of treating and reutilizing electronic waste. An effective liberation of metals from non metallic components is a crucial step towards mechanical separation and recycling of wasted PCBs. In this paper, the selective shredding theory and mechanics characteristics of wasted PCBs were analyzed, and the shredded experiments of wasted PCBs by hammer mill were investigated. The result shows that the selective shredding exists in the wasted PCBs shredded process by hammer mill. The shredding velocity of non metallic components is far greater than that of metals in the wasted PCBs shredding, which makes the metals concentrate in the coarser fraction. And the impact force of hammer mill is superior to metal liberation from non metallic components, a satisfied metal liberation degree can be achieved in the wasted PCBs shredding by hammer mill.展开更多
Printed-circuit board (PCB) elliptic antennas with useful bandwidth exceeding 10:1 ratio are suitable for wideband radar, wireless ultra wideband (UWB) and other wireless communication applications. We present wideban...Printed-circuit board (PCB) elliptic antennas with useful bandwidth exceeding 10:1 ratio are suitable for wideband radar, wireless ultra wideband (UWB) and other wireless communication applications. We present wideband PCB elliptic dipole antennas which are capable of achieving the bandwidth requirements for all the applications. A set of elliptic dipole antennas with varying eccentricities have been fabricated for demonstration. We find one specific size (specific eccentricity) dipole that can yield an impressive 1.5-16 bandwidth exceeding the currently available. A couple of elliptic dipole antennas suitable for UWB application have been presented. We have measured swept frequency response, impedance and radiation patterns of all dipoles. An empirical formula is given for calculating the starting resonant frequency within the operating band. The calculated values are found in good agreement with measured results.展开更多
Harvesting mechanical energy from our surroundings to acquire a steady and high power output has attracted intensive interest due to the fast development of portable electronics. In this work the disk-structured tribo...Harvesting mechanical energy from our surroundings to acquire a steady and high power output has attracted intensive interest due to the fast development of portable electronics. In this work the disk-structured triboelectric nanogenerator （TENG） was prepared based on the mature printed drcuit board （PCB） technology and the composite structure for effectively improving the utilization in space. A narrow grating of 1~ was designed to produce high output. Operated at a rotation rate of 1,000 rpm, the TENG produces a high output power density of 267 mW/cm2 （total power output of 25.7 W） at a matched load of 0.93 MfZ After introducing a transformer, the output power can be managed so that it can be directly used to charge a battery for a smart phone. With the PCB production technology, fabrication of high performance TENG at low cost and large-scale becomes feasible.展开更多
Triggered spark-gap switch is a popular discharge switch for pulse power systems.Previous studies have focused on planarizing this switch using thin film techniques in order to meet the requirements of compact size in...Triggered spark-gap switch is a popular discharge switch for pulse power systems.Previous studies have focused on planarizing this switch using thin film techniques in order to meet the requirements of compact size in the systems.Such switches are one-shot due to electrodes being too thin to sufficiently resist spark-erosion.Additionally,these switches did not employ any structures in securing internal gas composition,resulting in inconsistent performance under harsh atmospheres.In this work,a novel planar triggered spark-gap switch(PTS)with a hermetically sealed cavity was batched-prepared with printed circuit board(PCB)technology,to achieve reusability with low cost.The proposed PTS was inspected by micro-computed tomography to ensure PCB techniques meet the requirements of machining precision.The results from electrical experiments demonstrated that PCB PTS were consistent and reusable with lifespan over 20 times.The calculated switch voltage and circuit current were consistent with those derived from real-world measurements.Finally,PCB PTS was used to introduce hexanitrostilbene(HNS)pellets in a pulse power system to verify its performance.展开更多
Printed Circuit Boards(PCBs)are materials used to connect components to one another to form a working circuit.PCBs play a crucial role in modern electronics by connecting various components.The trend of integrating mo...Printed Circuit Boards(PCBs)are materials used to connect components to one another to form a working circuit.PCBs play a crucial role in modern electronics by connecting various components.The trend of integrating more components onto PCBs is becoming increasingly common,which presents significant challenges for quality control processes.Given the potential impact that even minute defects can have on signal traces,the surface inspection of PCB remains pivotal in ensuring the overall system integrity.To address the limitations associated with manual inspection,this research endeavors to automate the inspection process using the YOLOv8 deep learning algorithm for real-time fault detection in PCBs.Specifically,we explore the effectiveness of two variants of the YOLOv8 architecture:YOLOv8 Small and YOLOv8 Nano.Through rigorous experimentation and evaluation of our dataset which was acquired from Peking University’s Human-Robot Interaction Lab,we aim to assess the suitability of these models for improving fault detection accuracy within the PCB manufacturing process.Our results reveal the remarkable capabilities of YOLOv8 Small models in accurately identifying and classifying PCB faults.The model achieved a precision of 98.7%,a recall of 99%,an accuracy of 98.6%,and an F1 score of 0.98.These findings highlight the potential of the YOLOv8 Small model to significantly improve the quality control processes in PCB manufacturing by providing a reliable and efficient solution for fault detection.展开更多
基金Special Fund Project of Science and Technology Innovation of Dongli District(21090302)Research Projectof Applied Basic and Front Technologies of Tianjin(10JCZDJC15400)
文摘In order to study the role of printed circuit board(PCB)in high-power LED heat dissipation,a simple model of high-power LED lamp was designed.According to this lamp model,some thermal performances such as thermal resistances of four types of PCB and the changes of LED junction temperature were tested under three different working currents.The obtained results indicate that LED junction temperature can not be lowered significantly with the decreasing thermal resistance of PCB.However,PCB with low thermal resistance can be matched with smaller volume heat sink,so it is hopeful to reduce the size,weight and cost of LED lamp.
基金National Natural Science Foundation of China(No.51805079)Fundamental Research Funds for the Central Universities,China(No.2232021D-15)Shanghai Science and Technology Program(No.20DZ2251400)。
文摘The quality of printed circuit board(PCB)micro-hole processing directly determines the stability of the inner and outer circuit connections.Micro-hole drilling technology is a typical method for PCB micro-hole processing.The problem of optimal control of its drilling force is one of the main factors affecting the quality of micro-hole machining.To address this problem,the thrust forces and torques in PCB drilling were first modeled and analyzed,and the corresponding prediction models were established.The drilling force analysis was carried out through the micro-hole drilling experiment,the specific cutting energy under different feed rates was calculated,the influence of the size effect was clarified,and the accuracy of the prediction model was verified.The result shows that during the drilling of glass fiber cloth,changes in the material removal mechanism are induced as the feed per revolution is varied.When the feed per revolution is less than the tool edge radius,the glass fiber is not cut by the main cutting edge,but is crushed and broken.When the feed per revolution is greater than the radius of the tool edge,the glass fiber is cut by the main cutting edge.At the same time,the established analytical model can accurately reflect the influence of the size effect on the drilling torque in PCB micro-hole drilling,and the error is within 10%.This method has certain practical application value in controlling PCB micro hole processing quality.
文摘Electronic scrap, especially wasted printed circuit boards (PCBs), is regarded as an environmental challenge. At present, the physical separation is thought to be the environmental friendly and economical method of treating and reutilizing electronic waste. An effective liberation of metals from non metallic components is a crucial step towards mechanical separation and recycling of wasted PCBs. In this paper, the selective shredding theory and mechanics characteristics of wasted PCBs were analyzed, and the shredded experiments of wasted PCBs by hammer mill were investigated. The result shows that the selective shredding exists in the wasted PCBs shredded process by hammer mill. The shredding velocity of non metallic components is far greater than that of metals in the wasted PCBs shredding, which makes the metals concentrate in the coarser fraction. And the impact force of hammer mill is superior to metal liberation from non metallic components, a satisfied metal liberation degree can be achieved in the wasted PCBs shredding by hammer mill.
文摘Printed-circuit board (PCB) elliptic antennas with useful bandwidth exceeding 10:1 ratio are suitable for wideband radar, wireless ultra wideband (UWB) and other wireless communication applications. We present wideband PCB elliptic dipole antennas which are capable of achieving the bandwidth requirements for all the applications. A set of elliptic dipole antennas with varying eccentricities have been fabricated for demonstration. We find one specific size (specific eccentricity) dipole that can yield an impressive 1.5-16 bandwidth exceeding the currently available. A couple of elliptic dipole antennas suitable for UWB application have been presented. We have measured swept frequency response, impedance and radiation patterns of all dipoles. An empirical formula is given for calculating the starting resonant frequency within the operating band. The calculated values are found in good agreement with measured results.
文摘Harvesting mechanical energy from our surroundings to acquire a steady and high power output has attracted intensive interest due to the fast development of portable electronics. In this work the disk-structured triboelectric nanogenerator （TENG） was prepared based on the mature printed drcuit board （PCB） technology and the composite structure for effectively improving the utilization in space. A narrow grating of 1~ was designed to produce high output. Operated at a rotation rate of 1,000 rpm, the TENG produces a high output power density of 267 mW/cm2 （total power output of 25.7 W） at a matched load of 0.93 MfZ After introducing a transformer, the output power can be managed so that it can be directly used to charge a battery for a smart phone. With the PCB production technology, fabrication of high performance TENG at low cost and large-scale becomes feasible.
基金We gratefully acknowledge support from the Natural Science Foundation of Jiangsu Province of China(Grant No.BK20151486).
文摘Triggered spark-gap switch is a popular discharge switch for pulse power systems.Previous studies have focused on planarizing this switch using thin film techniques in order to meet the requirements of compact size in the systems.Such switches are one-shot due to electrodes being too thin to sufficiently resist spark-erosion.Additionally,these switches did not employ any structures in securing internal gas composition,resulting in inconsistent performance under harsh atmospheres.In this work,a novel planar triggered spark-gap switch(PTS)with a hermetically sealed cavity was batched-prepared with printed circuit board(PCB)technology,to achieve reusability with low cost.The proposed PTS was inspected by micro-computed tomography to ensure PCB techniques meet the requirements of machining precision.The results from electrical experiments demonstrated that PCB PTS were consistent and reusable with lifespan over 20 times.The calculated switch voltage and circuit current were consistent with those derived from real-world measurements.Finally,PCB PTS was used to introduce hexanitrostilbene(HNS)pellets in a pulse power system to verify its performance.
文摘Printed Circuit Boards(PCBs)are materials used to connect components to one another to form a working circuit.PCBs play a crucial role in modern electronics by connecting various components.The trend of integrating more components onto PCBs is becoming increasingly common,which presents significant challenges for quality control processes.Given the potential impact that even minute defects can have on signal traces,the surface inspection of PCB remains pivotal in ensuring the overall system integrity.To address the limitations associated with manual inspection,this research endeavors to automate the inspection process using the YOLOv8 deep learning algorithm for real-time fault detection in PCBs.Specifically,we explore the effectiveness of two variants of the YOLOv8 architecture:YOLOv8 Small and YOLOv8 Nano.Through rigorous experimentation and evaluation of our dataset which was acquired from Peking University’s Human-Robot Interaction Lab,we aim to assess the suitability of these models for improving fault detection accuracy within the PCB manufacturing process.Our results reveal the remarkable capabilities of YOLOv8 Small models in accurately identifying and classifying PCB faults.The model achieved a precision of 98.7%,a recall of 99%,an accuracy of 98.6%,and an F1 score of 0.98.These findings highlight the potential of the YOLOv8 Small model to significantly improve the quality control processes in PCB manufacturing by providing a reliable and efficient solution for fault detection.
