Guoyun Zhou

A new approach causing the patterns fabricated by silver nanoparticles to be conductive without sintering

Silver nanoparticles (Ag NPs) with a mean size of about 90 nm were synthesized by polyol reduction of silver nitrate with ethylene glycol (EG) in the presence of poly(vinyl pyrrolidone) (PVP). The Ag NPs undergo a spontaneous coalescence in the presence of chloride ions even without a traditional sintering process which occurs at a relatively high temperature. Such behavior can cause a rapid decrease in the resistivity of the patterns fabricated by Ag NPs. Conductive silver lines were successfully fabricated on FR-4 substrate using this method. The resulting conductivity of the silver lines reached about 16% of the bulk silver value, which enables fabrication of conductive patterns on some electronic devices.

Preparation of High-Performance Conductive Ink with Silver Nanoparticles and Nanoplates for Fabricating Conductive Films

A novel preparation method for a high-performance conductive ink which consisted of silver nanoplates, spherical silver nanoparticles, and epoxy resin was developed. Silver nanoparticles and nanoplates were synthesized via chemical reduction method in the presence of poly (vinyl pyrrolidone) (PVP). The prepared silver ink exhibited a remarkable electrical, thermal stability, and mechanical properties, which were confirmed by the four-point probe method, thermogravimetric analysis (TGA), and the three-point bending testing. We demonstrated the influence of sintering temperatures and time on the electrical resistivity. After sintering at 150°C for 15 min, the conductive film was able to achieve the volume electrical resistivity of (3–4) × 10−5Ω · cm.

Failure mechanism of solder bubbles in PCB vias during high‐temperature assembly

Purpose – Pb‐free soldering challenged printed circuit board (PCB) assembly with high temperature. The purpose of this paper is to explain the failure mechanism of printed circuit board (PCB) assembly with solder bubbles of vias to avoid the problems of via‐drilling defects and solder joint failure.Design/methodology/approach – The failure of PCB vias with solder bubbles was investigated through cross sections and SEM microstructure inspection, TMA measurement, moisture absorption analysis and DSC measurement. The moisture absorption and CTE of FR4 laminate matched with manufacturing requirement to avoid the effects of solder bubbles. The effects of via drilling with a dull drill bit were compared to that with a new drill bit.Findings – The moisture absorbed inside holes of via plating layers could be exposed to induce solder bubbles during Pb‐free soldering assembly and dull drill bits should be prevented during the drilling process to avoid the no‐bearing drilling effects.Originality/value – The failure...

Synthesis and characterization of Ag nanorods used for formulating high-performance conducting silver ink

Silver nanorods with ∼100 nm in diameter and ∼5 µm in length were synthesised by the soft solution-phase approach in the presence of poly(vinylpyrrolidone) (PVP), which was employed as a protecting agent. The obtained silver nanorods were characterised by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV-visible spectrum. The molar ratio and injection rate of PVP and AgNO3 played an important role in controlling the morphology and aspect ratio of nanorods. The growth mechanism of silver nanorods was also discussed. Moreover, the conductive ink was prepared using as-synthesised products, and the electrical resistivity of the final consolidated trace with this kind of ink was up to 2.7 × 10−5 Ωcm.

A Novel Nitric Acid Etchant and Its Application in Manufacturing Fine Lines for PCBs

We have developed a new etching solution for the printed circuit board industry. The primary oxidant of the solution is nitric acid, which reacts with copper coating on the substrate. The other components of the solution are sulfuric acid and additive, which are used to control etching reaction rate and solutions characteristics. The optimum parameters for the concentrations of nitric acid, sulfuric acid, additive, and the operating temperature were obtained through orthogonal experiment with stagnant etching method. The parameters were then verified by the spray etching experiment in the industrial production line. Then, there are a series of tests, carried out by metallographic slicing tester and scanning electron microscopy to evaluate the quality of copper conductive lines in stagnant and spray etching experiments. compared with conventional cupric chloride etchant, the testing results showed that the nitric acid etchant can manufacture fine lines with lower undercut, better wall sides, with higher etching rate, as well as being more friendly to the environment How the addition of H2SO4 influences etching rate and etching mechanism of nitric acid etchant is also discussed.

Research on etching blind holes and desmear with plasma

Plasma has a special advantage in cleaning micro blind holes due to simple process, easily operate and non-pollution. In this paper, different etching rates of materials include epoxy, polyimide(PI) and acrylic aid were obtained by cleaning blind holes with plasma in the same condition. The relationship between plasma parameters and etching depths of PI were discussed through orthogonal experimental design (OED). The effects of etching blind holes were investigated through metallographic cross section. Blind holes in a double-side flexible printed circuit(FPC) with PI materials were successfully obtained by plasma etching process.

Effects of microstrip line fabrication and design on high-speed signal integrity transmission of PCB manufacturing process

As a common transmission line, the microstrip line plays an important role in high-speed circuits. The purpose of this paper was to investigate the effects of the circuit design of microstrip lines on the signal integrity (SI). In addition, the influence of the type and thickness of the solder resist ink on SI was analyzed to provide guidance for the related producing process design of printed circuit boards (PCBs).,Microstrip line properties consisting of shape, line-width/line-space ratio, reference layer design and as-covered solder resist ink were designed to measure the insertion loss (S21) in high-speed PCB.,The study showed that the insertion loss (S21) of straight, meander, snake-shaped and wavy microstrip lines was approximately consistent. A microstrip line with width/space ratio less than 0.96 is necessary, as the differential line closing produces a mutual interference. Reference layer including the discontinuous area should be repaired by adjusting the microstrip line parameters. With regard to the solder resist ink, the insertion loss of novel solder resist ink decreased by 0.163 dB/in at 12.9 GHz and 0.164 dB/in at 14 GHz, compared with traditional solder resist ink. Accordingly, the insertion loss effectively improved at a lower thickness of solder resist.,This paper demonstrated that the common designing factors of line shape, line/space ratio, reference layer and solder resist influence microstrip line SI in the significant reference of designer-making PCB layout.

Directly electroless-plating NI-P thin-film to fabricate magnetic core of integrated inductor for printed circuit board

Integrated inductor with magnetic core is one of the three significant passive components for PCB (Printed Circuit Board) assembly. In this paper, a novel structure of integrated inductor with Ni-P (low P content) magnetic core deposited on the as-patterned conductive copper lines was fabricated by directly electroless-plating method. Two types of PCB integrated inductor with patterns of rectangle and hexagon winding were designed, respectively. The inductance changes were investigated under the changes of Ni-P plating times and tested frequency. Obvious increasing was observed after the deposition of Ni-P magnetic core. Furthermore, effects of the P content of Ni-P thin-film were also investigated in this paper.

Effects of Mn2+ on the electrical resistance of electrolessly plated Ni-P thin-film and its application as embedded resistor

Abstract The effects of manganese sulfate monohydrate (denoted as MSM) on the properties of electroless Ni–P thin-film were investigated. The properties of Ni–P thin-film were examined by means of atomic force microscopy (AFM), cyclic voltammetry, scanning electron microscopy (SEM), X-ray diffraction, energy-dispersive X-ray spectrometer and X-ray photoelectron spectroscopy. AFM and SEM results showed that MSM had significant influences on the morphology, including the formation of smaller nodules, nano-size particles boundaries on both surface and inside of nodules. Due to the specific topologies, the resistance of Ni–P thin-film deposited with MSM was increased. Based on the characterization results, we summarized that the Mn2+ or Mn2+-compound were primarily confirmed to act as the stabilizer in Ni–P electroless process. Moreover, the verification test for Ni–P thin-film in application as embedded resistor was carried out through electrical, thermal stability examination by means of current–voltage (I–V), temperature coefficient of resistance and thermal shock tests, respectively. Experiment results demonstrated the Ni–P thin-film deposited with MSM is qualified for embedded resistors.

Effects of MnSO4 on microstructure and electrical resistance properties of electroless Ni−P thin-films and its application in embedded resistor inside PCB

Purpose – Nickel phosphorus (Ni−P) thin-films have been electrolessly deposited in an acid-plating bath with the addition of manganese sulfate monohydrate (MSM) to achieve higher resistance for the application of embedded resistor with value beyond 10 KΩ. As this material is being used for fabricating embedded resistors under the addition of MSM, its resistance properties including effects of MSM concentration and plating time on resistances, temperature coefficient of resistance (TCR), and resistance tolerance of embedded resistor were investigated. The paper aims to discuss these issues. Design/methodology/approach – The structure of fabricated Ni−P film was detected by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The properties of substrate, including the surface morphologies, glass transition process and boundary of copper pad and substrate surface, were performed by SEM, dynamic mechanical analysis and optical microscope, respectively. The resistance toleran...