Circuit Substrate Research Articles

Mechanical and dielectric properties of MgO ceramics with HNT additions

Abstract This study, the ceramics’ sintering, mechanical, and dielectric properties were examined, and the influence of HNT additives on these properties was investigated. HNT was added to the structure as a SiO2 source to the MgO ceramics, which are difficult to process, since SiO2 suppresses the grain growth of MgO ceramics and significantly reduces the sintering temperature. After calcination at 800 °C HNT at different ratios (1, 3, 5, 7, 9, 11 wt%) were added to calcined MgO powder. As a result of XRD analysis, it was determined that spinel, forsterite and periclase phases were formed and these results were also confirmed by SEM images. The addition of HNT led to the formation of the forsterite phase at grain boundaries, enhancing mechanical properties. The best mechanical properties were observed in MgO ceramics with 11% HNT additives. Adding HNT at different ratios increased the dielectric constant of MgO ceramics. HNT-added MgO ceramics exhibited higher dielectric constant value than those at ambient temperature. The lowest dielectric constant value was measured as ~ 8.5 for MgO ceramic without any HNT addition. Since the materials to be used as circuit substrates require strict dielectric and mechanical properties, it is aimed to improve the mechanical and dielectric properties of MgO ceramics with the addition of HNT. MgO ceramics incorporating HNT in this study exhibited outstanding dielectric and mechanical characteristics, suggesting their potential as favorable materials for circuit substrates.

Dielectric and structural properties evolution of PTFE-based high-frequency circuit substrates for mmwave application under hygrothermal aging

Dielectric and structural properties evolution of PTFE-based high-frequency circuit substrates for mmwave application under hygrothermal aging

Moculus: an immersive virtual reality system for mice incorporating stereo vision.

Due to technical roadblocks, it is unclear how visual circuits represent multiple features or how behaviorally relevant representations are selected for long-term memory. Here we developed Moculus, a head-mounted virtual reality platform for mice that covers the entire visual field, and allows binocular depth perception and full visual immersion. This controllable environment, with three-dimensional (3D) corridors and 3D objects, in combination with 3D acousto-optical imaging, affords rapid visual learning and the uncovering of circuit substrates in one measurement session. Both the control and reinforcement-associated visual cue coding neuronal assemblies are transiently expanded by reinforcement feedback to near-saturation levels. This increases computational capability and allows competition among assemblies that encode behaviorally relevant information. The coding assemblies form partially orthogonal and overlapping clusters centered around hub cells with higher and earlier ramp-like responses, as well as locally increased functional connectivity.

Ultrastrong, Ductile, Tear- and Folding-Resistant Polyimide Film Doubly Reinforced by an Aminated Rigid-Rod Macromolecule and Graphene Oxide.

As a high-performance polymer with exceptional mechanical, thermal, and insulating properties, polyimide (PI) has been widely used as flexible circuit substrates for microelectronics, portable electronics, and wearable devices. Due to the growing demand for further thinning and lightweighting of electronic products, PI films need to have further enhanced mechanical properties. Traditional nanofiller-reinforced PI films often exhibit reduced ductility and limited improvements in strength. Therefore, it remains a challenge to simultaneously improve the strength and toughness of PI films while preserving their ductility. In this study, we report an exceptionally strong and ductile PI doubly reinforced by one-dimensional rigid-rod para-aramid, poly(p-aminophenylene aminoterephthalamide ((NH2)2-PPTA), and two-dimensional graphene oxide (GO) nanosheets. The amino side groups of (NH2)2-PPTA react with the anhydride end groups of PI, forming covalent bonds. At a (NH2)2-PPTA content of only 0.4 wt %, the (NH2)2-PPTA/PI film displays significantly enhanced mechanical properties. When 0.4 wt % of GO is added together with (NH2)2-PPTA, the tensile strength, tensile toughness, and strain at break reach 284.8 ± 5.3 MPa, 277.9 ± 7.6 MJ/m3, and 132.6 ± 3.8%, which are ∼178, ∼312, and ∼51% higher, respectively, than those of pure PI. Moreover, the doubly reinforced PI film also exhibits a 206% increase in tear strength and significantly enhanced folding resistance. The dual reinforcement of PI with (NH2)2-PPTA and GO improves the mechanical properties more efficiently than any single reinforcing agents previously reported and overcomes the disadvantage of most inorganic nanofillers that reduce ductility.

The low-temperature thermal conduction and millimeter-wave dielectric properties of β-Si3N4 as a heat-dissipation substrate

Increasing operating frequency is required in wireless communication systems. In use, this generates heat, which results in serious problems for semiconductor devices. Silicon nitride (Si3N4) has high thermal conductivity and fracture strength. Therefore, it is expected to be suitable for heat dissipation in active circuit substrates for wireless communication. In this study, Si3N4 with varying thermal conductivities were prepared by controlling starting material and sintering conditions and their low-temperature thermal conductivities were measured. The mean free path of phonons in β-Si3N4 influences its thermal conductivity. The temperature dependence of the Debye–Waller factor obtained by synchrotron radiation scattering supported the high thermal conductivity of the β-Si3N4. The degradation of thermal conductivity was interpreted in terms of the full width at half maximum of Raman spectra. Further, infrared reflectivity and first-principles calculation for β-Si3N4 confirmed their superior dielectric properties compared with other high thermal conductive materials.

Thin Copper Plate Defect Detection Based on Lamb Wave Generated by Pulsed Laser in Combination with Laser Heterodyne Interference Technique.

Thin copper plate is widely used in architecture, transportation, heavy equipment, and integrated circuit substrates due to its unique properties. However, it is challenging to identify surface defects in copper strips arising from various manufacturing stages without direct contact. A laser ultrasonic inspection system was developed based on the Lamb wave (LW) produced by a laser pulse. An all-fiber laser heterodyne interferometer is applied for measuring the ultrasonic signal in combination with an automatic scanning system, which makes the system flexible and compact. A 3-D model simulation of an H62 brass specimen was carried out to determine the LW spatial-temporal wavefield by using the COMSOL Multiphysics software. The characteristics of the ultrasonic wavefield were extracted through continuous wavelet transform analysis. This demonstrates that the A0 mode could be used in defect detection due to its slow speed and vibrational direction. Furthermore, an ultrasonic wave at the center frequency of 370 kHz with maximum energy is suitable for defect detection. In the experiment, the size and location of the defect are determined by the time difference of the transmitted wave and reflected wave, respectively. The relative error of the defect position is 0.14% by averaging six different receiving spots. The width of the defect is linear to the time difference of the transmitted wave. The goodness of fit can reach 0.989, and it is in good agreement with the simulated one. The experimental error is less than 0.395 mm for a 5 mm width of defect. Therefore, this validates that the technique can be potentially utilized in the remote defect detection of thin copper plates.

The basal forebrain to lateral habenula circuitry mediates social behavioral maladaptation

Elucidating the neural basis of fear allows for more effective treatments for maladaptive fear often observed in psychiatric disorders. Although the basal forebrain (BF) has an essential role in fear learning, its function in fear expression and the underlying neuronal and circuit substrates are much less understood. Here we report that BF glutamatergic neurons are robustly activated by social stimulus following social fear conditioning in male mice. And cell-type-specific inhibition of those excitatory neurons largely reduces social fear expression. At the circuit level, BF glutamatergic neurons make functional contacts with the lateral habenula (LHb) neurons and these connections are potentiated in conditioned mice. Moreover, optogenetic inhibition of BF-LHb glutamatergic pathway significantly reduces social fear responses. These data unravel an important function of the BF in fear expression via its glutamatergic projection onto the LHb, and suggest that selective targeting BF-LHb excitatory circuitry could alleviate maladaptive fear in relevant disorders.

Quasi-direct Cu–Si3N4 bonding using multi-layered active metal deposition for power-module substrate

The advancement of power modules demands more reliable insulating circuit substrates. Traditional substrates, comprising Cu and Si3N4, are produced using active metal brazing (AMB). However, AMB substrates have reliability concerns owing to electrochemical migration and void formation from brazing filler metals. This study introduces a quasi-direct Cu–Si3N4 bonding technique using a Ti/Al bilayer active metal deposition at the bonding interface. A sputtered Ti/Al bilayer was formed on the Si3N4 surface, then heated and pressurized the sputtered Si3N4 substrate with Cu sheets in vacuum to bond each other without voids or delamination. The Ti/Al layers reacted with Si3N4 and Cu, forming a 300 nm intermediate layer. TEM observations show this layer contains segregated Ti–N and Cu–Al phases, with a good lattice match to Si3N4 and Cu–Al. Temperature-cycling tests on the Cu/Si3N4/Cu substrate revealed delamination caused by increased tensile stress at the periphery of the bonding area due to asymmetrical Cu patterns. This novel quasi-direct Cu–Si3N4 bonding technique addresses issues of electrochemical migration and void formation seen in AMB substrates, offering a reliable bonding interface for power electronic substrates.

Superconducting through-substrate vias on sapphire substrates for quantum circuits

Superconducting through-substrate vias on sapphire substrates for quantum circuits

High-frequency wearable ultrasound array belt for small animal echocardiography.

Wearable ultrasound has been widely developed for long-term, continuous imaging without the need for bulky system manipulation and repeated manual locating. To potentially lead to more accurate and reliable imaging monitoring, this work presents the design, fabrication, and evaluation of a novel high-frequency wearable ultrasound array belt (WUAB) for small animal echocardiography. The fabrication process involved precise dicing technology for a λ-pitch design. The 20 MHz WUAB consists of two matching layers, piezoelectric composite with 128 channels, customized flexible circuit substrate, acoustic backing layer, and customized belt structure with designed end tip and insertion point for wearability. The resulting WUAB demonstrates sensitivity of -5.69 ± 2.5 dB and fractional bandwidth of 57 ± 5 %. In vivo experiments on rat model showed expected echocardiography and B-mode images of rat heart. These results represent significant promise for future longitudinal studies in small animals and real-time physiological monitoring.

High Speed Copper Plating Process for IC Substrate

The integrated circuit (IC) substrate occupies an interesting place in electronic devices. They serve as the bridge between the integrated circuits and the PCB. In this connecting point, they must meet the requirements of both worlds. They must provide the high density of connections to match the IC chip, while at the same time be a stable and robust platform for the chip to reside on. The IC substrate feature sizes and uniformity requirements are moving closer to what is required in the semi-conductor industry, except these substrates must be made at a scale, speed, and cost expected in the PCB industry. In this paper, we present an acid copper electrolyte for plating 2 in 1 redistribution layers (RDL), with small vias and fine lines down to 10µm wide. The electrolytic process successfully plates these features, while maintaining a uniform surface across the panel. The 510 mm x 515 mm panel had less than 5% variation in Cu thickness. The electrolyte was evaluated in a vertical continuous plating (VCP) style tool and a tool that plates panels at high speed. The standard VCP tool operated around 1.0 – 3.0 ASD, whereas the high-speed plater operated around 4.5 – 6.5 ASD. The obvious benefit of the high-speed tool was to reduce the plating time, but it also provided new degrees of control that are not available in VCPs. In either tool, the electrolyte performed well and produced uniform deposits that met the physical requirements that IC substrate applications demand.

Addressing Advanced IC Substrate Deformation and Pattern Distortion Using an Extremely Large Exposure Field Fine Fine-Resolution Lithography System

The More than Moore era is upon us, as manufacturers increasingly turn to back-end advances to meet the next-generation device performance gains of today and tomorrow. In the advanced packaging space, heterogeneous integration combines multiple chips with different functionalities and from different silicon nodes inside one package, ranging in size from 75mm x 75mm to 175mm x 175mm. But as with any new technology, heterogeneous integration comes with its own set of unique challenges. For starters, package sizes are expected to grow significantly due to the number of components making up each integrated package. The problem: these significantly larger packages would typically require multiple exposure shots to complete the lithography steps for the package. Furthermore, the process of adding multiple redistribution layers (RDL) may cause stress to both the surface and inside of the substrate. Formation changes experienced by the panel, as a result of thermal, high-pressure and other fan-out processes, shift the design location from its nominal coordinates; this causes inaccurate overlay and low-overlay yield in the lithography process. And then there is the matter of tightening resolution requirements. RDL layers in advanced integrated circuit substrates (AICS) will require a resolution of 3µm and will eventually move toward a resolution of 1µm. To address these challenges, and better enable the heterogenous integration process, an extremely large exposure field, fine-resolution lithography solution was proposed to enable packages over 250mm x 250mm without the need for image stitching, while exceeding the overlay and critical dimension uniformity requirements for these packages. In this paper, a 515mm x 510mm Ajinomoto build-up film (ABF)+copper clad laminate (CCL) substrate is selected as the test vehicle. We will analyze the pattern distortion of an ABF+CCL substrate to understand the distribution of translation, rotation, scale, magnification, trap, orthogonality and other errors in the substrate, and then use an extremely large exposure field, fine-resolution lithography system to address the pattern distortion of the substrate. This demonstration will provide an analysis of panel distortion and detail how the extremely large exposure field, fine-resolution lithography solution addresses panel distortion to achieve an aggressive overlay number.

Performance of Microbial fuel cell as a post treatment unit of UASB reactor for distillery spent wash

Post treatment of Up-flow anaerobic sludge blanket reactor (UASBR) effluents by a duel chambered Microbial fuel cell (MFC) was evaluated for high strength distillery spent wash. Bench scale UASBR (5 L capacity) and MFC (1 L capacity) with carbon electrodes having proton exchange membrane were used to elucidate the energy generation potential and substrate (COD) removal efficiency. Step by step, the influent COD concentration of UASB-MFC unit was increased. The MFC shows increasing trend of open circuit voltage, COD removal and substrate degradation rate with increase in influent COD concentration. The maximum COD removal (73.79%) and open circuit voltage (1.1 V) were achieved at 20600 mg/L of COD. At maximum COD concentration, MFC showed power density (maximum), substrate degradation rate and power yield as 61.61mW/m2, 1.086 kg COD/m3day and 0.041 W/kg CODR respectively. UASB-MFC combined unit gave maximum COD removal of 90%. The experimental data revealed the potential of MFC as feasible, economic (cost saving) and sustainable option.

Adolescent neurostimulation of dopamine circuit reverses genetic deficits in frontal cortex function

Dopamine system dysfunction is implicated in adolescent-onset neuropsychiatric disorders. Although psychosis symptoms can be alleviated by antipsychotics, cognitive symptoms remain unresponsive and novel paradigms investigating the circuit substrates underlying cognitive deficits are critically needed. The frontal cortex and its dopaminergic input from the midbrain are implicated in cognitive functions and undergo maturational changes during adolescence. Here, we used mice carrying mutations in Arc or Disc1 to model mesofrontal dopamine circuit deficiencies and test circuit-based neurostimulation strategies to restore cognitive functions. We found that in a memory-guided spatial navigation task, frontal cortical neurons were activated coordinately at the decision-making point in wild-type but not Arc-/- mice. Chemogenetic stimulation of midbrain dopamine neurons or optogenetic stimulation of frontal cortical dopamine axons in a limited adolescent period consistently reversed genetic defects in mesofrontal innervation, task-coordinated neuronal activity, and memory-guided decision-making at adulthood. Furthermore, adolescent stimulation of dopamine neurons also reversed the same cognitive deficits in Disc1+/- mice. Our findings reveal common mesofrontal circuit alterations underlying the cognitive deficits caused by two different genes and demonstrate the feasibility of adolescent neurostimulation to reverse these circuit and behavioral deficits. These results may suggest developmental windows and circuit targets for treating cognitive deficits in neurodevelopmental disorders.

Adolescent neurostimulation of dopamine circuit reverses genetic deficits in frontal cortex function.

Dopamine system dysfunction is implicated in adolescent-onset neuropsychiatric disorders. Although psychosis symptoms can be alleviated by antipsychotics, cognitive symptoms remain unresponsive and novel paradigms investigating the circuit substrates underlying cognitive deficits are critically needed. The frontal cortex and its dopaminergic input from the midbrain are implicated in cognitive functions and undergo maturational changes during adolescence. Here, we used mice carrying mutations in Arc or Disc1 to model mesofrontal dopamine circuit deficiencies and test circuit-based neurostimulation strategies to restore cognitive functions. We found that in a memory-guided spatial navigation task, frontal cortical neurons were activated coordinately at the decision-making point in wild-type but not Arc-/- mice. Chemogenetic stimulation of midbrain dopamine neurons or optogenetic stimulation of frontal cortical dopamine axons in a limited adolescent period consistently reversed genetic defects in mesofrontal innervation, task-coordinated neuronal activity, and memory-guided decision-making at adulthood. Furthermore, adolescent stimulation of dopamine neurons also reversed the same cognitive deficits in Disc1+/- mice. Our findings reveal common mesofrontal circuit alterations underlying the cognitive deficits caused by two different genes and demonstrate the feasibility of adolescent neurostimulation to reverse these circuit and behavioral deficits. These results may suggest developmental windows and circuit targets for treating cognitive deficits in neurodevelopmental disorders.

An inhibitory circuit-based enhancer of DYRK1A function reverses Dyrk1a-associated impairment in social recognition

Heterozygous mutations in the dual-specificity tyrosine phosphorylation-regulated kinase 1a (Dyrk1a) gene define a syndromic form of autism spectrum disorder. The synaptic and circuit mechanisms mediating DYRK1A functions in social cognition are unclear. Here, we identify a social experience-sensitive mechanism in hippocampal mossy fiber-parvalbumin interneuron (PV IN) synapses by which DYRK1A recruits feedforward inhibition of CA3 and CA2 to promote social recognition. We employ genetic epistasis logic to identify a cytoskeletal protein, ABLIM3, as a synaptic substrate of DYRK1A. We demonstrate that Ablim3 downregulation in dentate granule cells of adult heterozygous Dyrk1a mice is sufficient to restore PV IN-mediated inhibition of CA3 and CA2 and social recognition. Acute chemogenetic activation of PV INs in CA3/CA2 of adult heterozygous Dyrk1a mice also rescued social recognition. Together, these findings illustrate how targeting DYRK1A synaptic and circuit substrates as "enhancers of DYRK1A function" harbors the potential to reverse Dyrk1a haploinsufficiency-associated circuit and cognition impairments.

CMOS substrate RC netlist reduction towards design cycle speed up

Integrated circuit substrate crosstalk is an effect with significant impact on design cycle and silicon success. Its accurate simulation comprises a significant design cycle acceleration means. A seamless way to incorporate the substrate crosstalk effect into the simulation is through a netlist describing the electrical behaviour of the substrate. Since such a netlist contains connections between all substrate contacts, it is extremely large for simulators to handle. Therefore it should be reduced, preserving the related accuracy and enabling simulation. In this work a methodology exploiting geometrical and electrical properties of the structure is applied, leading to a practical netlist. This netlist enables rapid simulation providing crucial information versus impact of the substrate crosstalk on system on chip performance.

A Dual-Layer Orthogonal-Layout Thin-Film Force Sensor for Digital Orthodontic Functional Appliances

Measuring the force exerted on oral tissue is crucial for orthodontic treatment. Without proper tools and methods, orthodontists must rely on their clinical experience to estimate the force, which limits the efficiency and accuracy of diagnosis and treatment. Previous works using flexible force sensor arrays and wireless technology are power-hungry and require either complex wiring or batteries for power supply. However, human oral nerves are highly sensitive to foreign objects, so these solutions are not suitable for clinical practice. This work presents a thin-film force sensor based on carbon paste on a flexible printed circuit (FPC) substrate with an area of 24×4mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The sensor is embedded in functional appliances and can be read out through a miniature connector by a handheld device that uses frequency-domain signal processing. The device is powered by a 360-mAh battery and can last for 15 hours with a form factor of 86×40×21 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . The device achieves a force resolution of 10 mN with an update rate of 10 Hz. Six samples are characterized and after two-point calibration, this system achieves a force accuracy of 1.3/-0.6 N. Our measurement results also show that the sensor is robust against liquid environment. A dual-layer orthogonal-layout method is proposed to check the alignment of the contact surfaces.

Spatial and Channel-Wise Co-Attention-Based Twin Network System for Inspecting Integrated Circuit Substrate

Spatial and Channel-Wise Co-Attention-Based Twin Network System for Inspecting Integrated Circuit Substrate

Automatic detection of wire bonding defects in microwave components using multi-stage hybrid methods based on deep learning

Wire bonding is one of the main processes in micro-assembly, as its quality directly affects the reliability of microwave components and their operating characteristics. Therefore, it is important to detect defects in wire bonding. Due to the diversity of chips, connections, and circuit substrates, the wire bonding regions vary greatly. Using image processing methods exclusively requires expert knowledge, and the solution lacks versatility. Meanwhile, in highly complex industrial scenarios, relying on end-to-end deep learning method alone cannot accomplish the task constrained by data volume and task difficulty. Therefore, we propose a three-stage wire bonding defect detection method that integrates deep learning with traditional image processing methods for the detection of complex wire bonding defects. In order to address the defect detection of more types of complex bonding images, we divide them into four categories and complete the detection step by step. In the first two stages, semantic segmentation and image processing methods are used in turn to complete the extraction of the region of interest, and in the third stage, we propose a defect recognition model based on Siamese network with a new feature fusion structure to enhance feature learning. Experiments show that the proposed three-stage method, which combines deep learning and image processing, can effectively detect wire bonding defects and is suitable for handling highly complex engineering tasks with greater efficiency and intelligence.