A technique for scalable spray coating of colloidal CdSeTe quantum dots (QDs) for photovoltaics and photodetector applications is presented. A mixture solvent with water and ethanol was introduced to enhance the adhesive force between QDs and the substrate interface. The performance of the detector reached the highest values with 40 spray coating cycles of QD deposition. The photodetectors without bias voltage showed broadband response in the wavelength range of 300–800 nm, and high responsivity of 15 mA/W, detectivity of more than 1011 Jones and rise time of 0.04 s. A large size QD-logo pattern film (10 × 10 cm2) prepared by the spray coating process displayed excellent uniformity of thickness and absorbance. The large area detectors (the active area 1 cm2) showed almost the same performance as the typical laboratory-size ones (the active area 0.1 cm2). Our study demonstrates that the spray coating is a very promising film fabrication technology for the industrial-scale production of optoelectronic devices.
In this paper, the impact of ground solder ball failure in ball grid array (BGA) package on near electric field radiation was investigated from the perspectives of both theoretical modelling and experimental testing. Based on the structural and material parameters, a 3D electromagnetic field numerical calculation model of circuit boards with failed ground solder balls was developed. The influences of both different number of failed ground solder balls and different signal frequencies on near electric field radiation was calculated. The electromagnetic field model results are validated using experimental tests.
Printed circuit boards (PCBs) have a large number of electrical connection nodes. Exposure to harsh environments may lead to connection faults in these nodes. In the present work, intelligent detection methods for electrical connection faults were studied. Specifically, the fault characteristics of connectors, bonding wires and solder balls in the frequency domain were analyzed. The reflection and transmission parameters of an example filter circuit with electrical connection faults were calculated using the Simulation Program with Integrated Circuit Emphasis (SPICE). With these obtained electrical parameters, three machine learning algorithms were used to detect example electrical connection faults for the example circuit. Based upon the performance evaluations of the three algorithms, one can conclude that machine-learning-based intelligent fault detection is a promising technique in diagnosing circuit faults due to electrical connection issues with high accuracy and lower time cost as compared to current manual processes.
Bonding wires are extensively used to provide electrical interconnections in communication systems. From the perspective of circuit analysis, the effects of such elements are often treated as an inductance. Bonding wires may cause inductive impedance discontinuity, which negatively impacts signal integrity. In this work, an impedance compensation technique using a chip capacitor was introduced. The electrical performance was improved significantly in the frequency band below 4 GHz. In order to expand the operating frequency of the circuit, another compensation approach based on adding a ground conductor was also studied. This compensation strategy is shown to be effective for frequencies up to 18 GHz. The results obtained from the model simulation for both strategies were also validated experimentally. The model simulation results for both approaches show good agreement with those obtained from the experimental measurements.
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