Multilayer Printed Circuit Board Research Articles

Power bus decoupling on multilayer printed circuit boards

Guidelines for the selection and placement of decoupling capacitors that work well for one-sided or two-sided printed circuit boards are not appropriate for multilayer boards with power and ground planes. Boards without internal planes take advantage of the power bus inductance to help decouple components at the higher frequencies. An effective decoupling strategy for multilayer boards must account for the low inductance and relatively high capacitance of the power bus.

High-resolution industrial radiography using convolutional neural networks

For quality control of electronic products with high-density electronic packaging and corresponding multi-layer printed circuit boards, x-ray inspection is not optional anymore. For high-resolution industrial radiography, we develop a de-blur filter using serial cascades of convolutional neural networks. We increase the number of channels along the network depth to accept complex features even at deeper depths. Various ways to increase the channel numbers are described. The performance of the networks is quantified in comparisons with the state-of-the-art networks. The result shows a large correlation between the performance and the total number of weights built in a network. Including the detailed results, this paper discusses the limitation of the present study, and future study.

A Miniature High-Sensitivity Active Electric Field Probe for Near-Field Measurement

A noncontact active electric field probe with miniature size and high sensitivity is designed for the noise location in electronic systems from 9 kHz to 1 GHz. This probe is fabricated in a multilayer printed circuit board (PCB) (dielectric constant of 4.2 and loss tangent of 0.02). The minimum width of the probe is 4 mm, and the length is 48 mm, which allows it to be used in compact and complex space like the PCB and the integrated circuit. The dual-stage amplifier circuit and the door-shaped structure are applied to the probe design, which improves the transfer gain of the probe 40–50 dB higher than that of an equivalently sized passive electric field probe. The spatial resolution is 0.6 mm, while the height of the probe tip above the device under the test is 0.3 mm. The proposed probe is verified with three-dimensional electromagnetic simulation and near-field measurement.

Fuzzy-multiple estimates of the parameter uncertainty influence in the computing devices elements calculating theory

A method for obtaining estimates for the scatter errors of endogenous characteristics in models for calculating the parameters of communication lines for elements of modern high-speed computing devices in the form of multilayer printed circuit boards is presented. The described methodology for taking into account the uncertainty of exogenous parameters of models in ratios for determining the cross-sectional area and spacing of conductors, delay parameters in short and long communication lines, allows to obtain a forecast of providing of signal integrity, providing of optimized matching of electric circuit elements, and observing of technological requirements for physical, mechanical and geometrical parameters of multilayer printed circuit boards. This technique is based on the theory of fuzzy sets and consists in using a modified form of the heuristic principle of generalization in the transition to fuzzy-sets arguments in the analytical calculation relationships for a number of the most important characteristics of communication lines. A number of examples of the application of the described technique is presented.

Transmission Line Representation of the Capacitive Via-Plate Interaction Toward a Capacitor-Free Via Model

Conventional physics-based via circuit model takes into account the capacitive coupling between via barrel and power/ground plane by a via-plate capacitor, whose calculation relies on a complex expression involving an infinite summation of Hankel functions. In this paper, a capacitor-free via model is proposed and realized by way of a novel transmission line representation of the via-plate capacitance. In particular, the via-plate capacitor is replaced by an open-circuited transmission line (OC-TL) with equal input admittance. The resultant capacitor-free model obviates the need of calculating the sum of infinite series. Instead, it only requires identifying the length of the OC-TL by simple closed-form expressions. Hence, the proposed efficient capacitor-free via model is able to facilitate the modeling of realistic multilayer printed circuit boards (PCBs) and packages. Both numerical and measurement results validate the proposed OC-TL-based via model.

Compact low‐cost high‐voltage pulse generator for biological applications

SummaryIn order to test the electroporation applied to mammalian cells (DU‐145 human prostate cancer cell line), treated with short (30 ns) intense electric pulses, a new architecture of a pulse generator is proposed. It provides a quasi‐rectangular output with nanosecond rise time and fully controlled repetition rate, which allows the control of the electric field dose applied to the cells. The system consists of a pulse generator with a high voltage gain and power efficiency, but it outputs exponential pulses. To improve that side, a pulse forming line (PFL) is used to get the final rectangular pulse. The whole device is designed using a multilayer printed circuit board (PCB) technology. That reduces the cost and increases the compactness of the generator. The output is connected to a special electroporation cuvette filled with special liquid. The impedance of such load is not well known, that is why some preliminary tests were carried out to identify the load of the generator. A number of simulations allowed to validate the design and to find out the influence of different parameters on its characteristics. Finally, a compact 4‐kV generator was built and tested. The results are discussed and compared with those obtained from simulations.

Effect of Electroplating Current on Surface Morphology and Thickness of Plated-Through Hole (PTH) in Multilayer Printed Circuit Board (PCB)

Multilayer printed circuit board (PCB) consists of many layers in PCB. In order to connect one layer to other layers is needed plated-through-hole (PTH). PTH is commonly formed from the copper metal using some methods such as electroplating or electroless plating. Electroplating is method which there is adhering process the copper metal using the electrical current. This method is easy and cheap in PCB manufacture. One of the important part of electroplating result is surface morphology and thickness of PTH in multilayer PCB. The objective of this study is to im the electroplating current in electroplating process to learn more about the effect of electroplating current against the surface morphology and thickness of PTH.. The electroplating current applied in this experiment is at 5 A, 10 A, 15 A, and 20 A. In this research is also used Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS) to characterize the formed PTH in multilayer PCB. The results shows that the PTH was successfully formed in through hole of multilayer PCB. The thickest PTH is about 37.8 μm for the applied current 20A and the smoothest morphology of PTH cross section is at the electroplating current 15 A.

Thermal Considerations of a Power Converter With Components Embedded in Printed Circuit Boards

Printed circuit board (PCB) technology is attractive for power electronic systems as it offers a low manufacturing cost for mass production. Integration technologies such as device embedding have been developed to take advantage of the interlayer space in multi-layer PCBs and to increase the performances (electrical and thermal). However, the PCB technology offers limited power dissipation due to the low thermal conductivity [≈0.3 W/( $\text {m} \cdot \text {K}$ )] of its composite substrate. In this article, we consider PCB embedding for a 3.3-kW ac/dc bidirectional converter. We describe the integration of not only the power dies but also the gate drive circuits and the power inductor, with a special focus on thermal management. The manufacturing processes of the boards are presented. Two thermal models based on finite elements (FEs) of this converter stage are introduced. The accuracy of these models is validated against experiments. The results show that a simplified FE model offers satisfying accuracy and fast simulation, even considering the relatively complex structure and layout of the PCBs.

Forward‐wave directional coupler based on slow‐wave coupled microstrip lines

This study presents the design of a forward-wave directional coupler based on slow-wave coupled microstrip lines realised in a multilayered printed circuit board technology. Thanks to the concept of slow-wave, a high difference between the even- and odd-mode phase velocities can be inherently achieved. Hence, by choosing adequate even- and odd-mode characteristic impedances close to 50 Ω, reduced-length forward couplers can be designed. As a proof of concept, a 0 dB forward coupler operating at 4.5 GHz is proposed. It exhibits a very high coupling of 0.56 dB at the centre frequency and a very large bandwidth of 43%, corresponding to 10 dB of isolation. A length miniaturisation of 84% is obtained as compared to the standard microstrip, leading to a total surface area of 0.132 λ g 2 , the smallest one reported so far.

Compact and Low-Phase-Noise Oscillator Employing Multilayer Sixteenth-Mode Substrate-Integrated Waveguide Filter for 5G Applications

In this paper, a compact and low-phase-noise (PN) free-running oscillator designed by sixteenth-mode substrate-integrated waveguide (SMSIW) bandpass filter (BPF) for 5G applications is proposed. The size of SMSIW cavity exhibits only one-sixteenth of the conventional SIW cavity. The SMSIW BPF is designed by using multilayered printed circuit board (PCB) process, and the active circuits and power divider are positioned on the top layer and bottom layer, respectively. The vertical feedback is achieved by using feedlines of SMSIW BPF and metallic via-hole. A parallel feedback configuration oscillator with four-order cross-coupling SMSIW BPF has been designed, fabricated, and measured. The measured results show that at the oscillation frequency of 3.52 GHz with −1.5-dBm output power, the PN is −107.36 and −132.07 dBc/Hz at 100 kHz and 1 MHz frequency offset, respectively. The figure of merit (FOM) at 1-MHz frequency offset is −191 dBc/Hz. Moreover, the size of SMSIW BPF is only $0.267\lambda _{\mathbf {0}}\times 0.109\lambda _{\mathbf {0}}$ . The proposed oscillator effectively demonstrates the advantages of compact size and low PN.

A Ka-Band Circularly Polarized Substrate Integrated Cavity-Backed Antenna Array

A high-gain 4 × 4 substrate integrated waveguide (SIW) circularly polarized (CP) antenna array at a Ka-band with a quadruple-ridge waveguide polarizer is proposed in this letter. The antenna array consists of 16 cavity-backed slot antenna elements, quadruple ridge waveguide polarizers, and SIW T-type power dividers. Dominant resonant mode TE110 is excited in the cavity-backed slot antenna element. The measured impedance bandwidth ( S 11 < –10 dB) is from 35.3 to 35.55 GHz, and 3 dB axial-ratio bandwidth is from 35.24 to 35.57 GHz. In addition, the maximum measured gain of 18.14 dBi at the boresight is experimentally obtained at 35.42 GHz. The antenna prototype was fabricated by a multilayer printed circuit board technology. To the best of our knowledge, the quadruple-ridge waveguide is used as polarizer to produce CP signals for the first time. Compared with an aperture antenna with a conventional rectangle or a circular waveguide polarizer, this work has high aperture radiation efficiency as well as compact size. This design idea may open a new way for development of millimeter-wave high-efficiency arrays.

Wear mechanisms of Ti(C7N3)-based cermet micro-drill and machining quality during ultra-high speed micro-drilling multi-layered PCB consisting of copper foil and glass fiber reinforced plastics

Printed circuit board (PCB) consists of copper foil and glass fiber reinforced plastics, and glass fiber reinforced plastics belong to the typical hard machining material, which leads to the poor surface finish and rapid tool wear. The new Ti(C7N3)-based cermet (TC) micro-drill was in-house developed to machine PCB S1000, the wear mechanisms and the machining quality were investigated comprehensively, while diffusional interactions between the TC and S1000 were also implemented. It was concluded that the main wear mode of the TC micro-drill was the flank wear, the area of the flank wear showed a trend of first increasing and then decreasing along with the feed per tooth, while no tool breakage occurred during the micro-drilling process. The main wear mechanisms contained the abrasive wear, adhesion wear, and diffusion wear. Moreover, both the 1st and 2nd layer PCBs had a good machining quality. Therefore, the TC micro-drill is suitable for machining PCB S1000.

Fast microfocus x-ray tube based on carbon nanotube array

A full vacuum-sealed macrofocus x-ray tube with a vertically-aligned ring-shaped carbon nanotube (CNT) emitter grown by microwave plasma enhanced chemical vapor deposition is presented in this paper. The external grid allowed the CNT-based x-ray tube to exhibit transient switching on and off. The total emission current was 200 μA, which corresponds to a maximum emission current density of 10.1 A/cm2 from the ring-shaped CNT emitter when the grid voltage was 2.4 kV. The optimized focus electrode controlled the beam convergence on the target to produce a very small x-ray focal spot size less than 5 μm. Consequently, this microfocus x-ray tube could produce x-ray images with very high spatial resolution. X-ray fluoroscopy images of a multilayer printed circuit board (PCB) and field programmable gate array show distinct gold PCB traces with approximately 20 μm width.

Transient analysis of finite multi‐conductor transmission line metamaterials (MTL‐MMs) based on discrete green's function (DGF) and macro‐modelling techniques

A new systematic macro-modelling technique for transient analysis of finite multi-conductor transmission line metamaterials (MTL-MMs) based on a Dyadic discrete Green's function (DGF) approach is proposed. Governing discrete voltage-based equations for one- and two-dimensional (1-D and 2-D) MTL-MMs are derived using a rigorous MTL analysis. Applying the idea of the Dyadic DGF solution to these equations, the impedance matrix representation of a finite open-ended MTL-MM is represented in a rational form, where the corresponding poles and residues can be identified exactly. The resulting pole/residue macro-model is converted into a state space model which is compatible to SPICE circuit simulator. The proposed macro-modelling technique significantly reduces the CPU time for transient analysis of 2-D electromagnetic band gap (EBG) structures embedded in large multi-layer printed circuit boards or volumetric NRI slabs with interaction with free space waves which can be modelled as an MTL-MM system. The usefulness of the proposed macro-model is illustrated by three sample MTL-MMs including 1-D shunt node negative refractive index ( NRI ) slab and 2-D two- and three-layered shielded EBG structures. The obtained results from the proposed macro-modelling technique are presented and compared with those obtained using a full-wave simulator, confirming the validity of the proposed model.

Design and Development of a Planar Electromagnetic Conveyor for the Microfactory

This paper presents a planar electromagnetic conveyor for a microfactory. The uniqueness of the conveyor design lies in its arrangement of overlapped two-dimensional mesh coils in matrix configuration that enables to drive a mobile part over long strokes. The conveyor architecture includes a fixed part, which consists of 5×5 matrix design that has been fabricated on a multilayer printed circuit board. An analytical model that takes into account the electromagnetic and friction effects has been developed. A conveyor prototype has been fabricated and experimentally characterized in open-loop control. Linear and planar motions, positioning repeatability error, straightness error, and rotation have been experimentally measured. From experimental results, the proposed architecture enables long linear displacement strokes ( $\leqslant$ 70 mm) and rotation ( $\leqslant \pm$ 12.37 $^\circ$ ). In addition, a 12 mm/s speed can be achieved for the mobile part at a nominal current of 0.8 A.

Wideband SIW-Based Low-Cost Multilayer Slot Antenna Array for $E$ -Band Applications

This paper proposes a substrate integrated waveguide (SIW) slot antenna array for the wideband gigabyte mobile radio application in the $E$ -band. The wideband unit cell design is based on simultaneous feeding of four-element radiation slots with a higher order cavity mode directly excited by a simple slot aperture fed by a microstrip fork-like tuning stub. Employing the higher order mode along with the slot aperture facilitates low loss, simple feeding network, and lower sensitivity to fabrication errors. To cancel the beam tilt versus frequency, the higher-order-mode unit cell is used in a $2 \times 2$ array along with a differential feeding structure. The array was designed and taped out using a new high-resolution multilayer printed circuit board (PCB) technology and characterized by using the constructed millimeter-wave (mm-wave) measurement setup at KU Leuven/imec. This technology provides the possibility to stack microvias in PCBs and reduces the fabrication cost compared to other multilayer technologies in mm-wave bands. The proposed array in $2 \times 2$ array configuration has a measured bandwidth of 11.4 GHz (16%), a total efficiency of 69%, a realized gain of 12 dBi at 72 GHz, and a 3-dB gain bandwidth that covers the entire impedance bandwidth. In comparison with existing $E$ -band SIW slot arrays (compensating for array sizes), the proposed design achieves similar or better performance in bandwidth but with lower cost, lower sensitivity to fabrication tolerances, and higher total efficiency.

Improvements of the Epoxy–Copper Adhesion for Microelectronic Applications

Upcoming electronic devices are required to be further miniaturized. The microelectronics industry and packaging technology focus efforts on optimizing adhesion between plated copper and printed circuit board (PCB) substrate (here epoxy/glass buildup composite), while keeping smooth surfaces for high-frequency application. We propose herein to review and deepen the basic understanding of the sequential buildup process employed worldwide for the past several decades for multilayered PCB manufacturing. This multiscale and interdisciplinary study aims to establish the relationships between degrees of precuring (α), oxidative etching (permanganate desmear wet treatment), and copper adhesion. The epoxy curing states on industrial coupons were evaluated by diffuse-reflectance infrared Fourier transform spectroscopy. Then, atomic force microscopy (AFM) described the desmear performances through topography evolution with α between the different sequence steps. Finally, polymer–copper adhesions were investigated b...

A Wireless Neurostimulator System with an Embedded ARM™ Microprocessor.

In this study, a novel multi-layer printed circuit board (PCB)-based neurostimulator system with an embedded microprocessor is presented for applications in neuroprosthesis. The system integrates rechargeable batteries, a power management block, adjustable constant-current waveforms, voltage transient monitoring, and evoked neural response recording. The system can be configured to select channels among the 16 stimulation channels via Bluetooth communication wirelessly. Bench top measurements demonstrated that the system generated biphasic current waveforms with various stimulation parameters with approximately 407 mW of power consumption. Additional testing and validation with microelectrodes are underway.

Aperture coupled stacked patch thin film antenna for automotive radar at 77 GHz

AbstractA hybrid thin film multilayer antenna for automotive radar is presented in this work. A 2 × 8 aperture coupled stacked patch antenna array is realized on a single layer printed circuit board (PCB) using a novel thin film-based approach. Using a compact 180° phase difference power divider, inter-element spacing in a 2×2 sub-array is reduced. Measurement results show a 19% (67.9–82.5 GHz) impedance bandwidth and a wideband broadside radiation pattern, with a maximum gain of 15.4 dBi realized gain at 72 GHz. The presented antenna compares favorably with other multilayer PCB antennas in terms of performance, with the advantage of simpler manufacturing and robust design. The antenna can be employed in mid-range automotive radar applications.

Сравнительная оценка условий прямой и электрохимической металлизации глухих отверстий многослойных печатных плат

The metal blind holes acting as interconnectors allow significantly reduce the number of layers, increase the efficiency of trace and decrease interference between the holes and signal conductors in the high frequency printed circuit boards. In this work, a comparative assessment of the conditions of direct and electrochemical metallization blind holes with diameters: 0,2; 0.25; 0.3; 0.4; 0.6; 0.8; 1.0 mm and a drilling depth of 0.5 mm located on experimental four-layer multilayer printed circuit boards, differing in the method of applying a conductive and copper coating was carried out. It has been established that in case non-fulfillment of mandatory conditions for the production of blind holes, in particular the aspect ratio is less than or equal to unity, incomplete metallization of the walls and especially the bottom of the holes is observed. The ways of combining the processes of direct and electrochemical metallization of holes, which provide the required thickness and quality of the copper coating at reduction of general duration of operations have been proposed based on the experimental data obtained during the work with multilayer printed boards. Also it has been established that the joint placement of blind holes with a smaller and larger diameter on one multilayer printed circuit board requires a more long direct metallization in combination with electrochemical at low values of current density. Copper films deposited on the walls of the holes and on the surface of the contact pads, regardless of the proposed way of metallization, have a highly dispersed structure. The composition of the palladium catalyst layers has been studied by energy dispersive analysis. The conductive coating on the blind hole’s walls contains between 1.55 and 6.77 at.% palladium.