Yuanming Chen

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...

Study on brown oxidation process with imidazole group, mercapto group and heterocyclic compounds in printed circuit board industry

The adhesion strength of the interface between copper foil and resin is an important technological parameter for applications in microelectronics. In this study, a new brown oxidation solution of copper foil, including the recipe composition and reliability tests, was fully discussed. We provided an overview of brown oxidation process used in the semi-flexible printed circuit boards production industry by investigating the brown oxide film. The morphology of the copper oxide film was changed from lamellar structure to honeycomb structure with the increasing of oxidation time. The peel adhesion strength of the Cu/polyimide laminates was increased from about 2–16 N/cm by altering the immersion time and the concentration of inhibitors in brown oxidation solution. Scanning electron microscopy, peel tests and X-ray diffraction indicated that the higher adhesion strength was resulted from the rougher surface and the proper etching depth of copper foil, which was caused by chemical reactions on the interface surface of copper foil.

Study of microvia filling process based on multi-physical coupling

ABSTRACT The microvia filling process used in the high-density interconnect printed circuit board manufacturing industry was investigated by multi-physical coupling technology. To achieve a perfect filling, SPS (bis-(sodium-sulphopropyl)-disulphide), EO/PO (ethylene oxide and propylene oxide block co-polymers) and PEOPI (polyethylene oxide-polyimide) were used. Furthermore, electrochemical behaviours of electrodeposition were investigated by cyclic voltammetry, galvanostatic potential transient measurement and dynamic potential polarisation technology. Through numerical simulation, the relationship between coverage of additive, concentration of additive, rotating speed of rotating disc electrode, exchange current density and curve slope was fitted. Based on multi-physical coupling to copper electrodeposition, a mathematical model of microvia filling was built to simulate the filling process by a finite element method, and a systematic analysis of the whole filling process was carried out. The void-free microvia filling and filling process with different shapes were finally achieved in acid copper electroplating solutions consisting of 0.3 M CuSO4·5H2O, 0.2 M H2SO4 and 80 mg L−1 Cl− (virgin make-up solution) plus additives SPS, EO/PO and PEOPI. Subsequently, from images of the microvia filling experiment at different times, shape evolution of the microvia filling and variation of electrodeposition rate at the bottom of the microvia and surface were analysed. The modelling result was compared with the measured data and showed good agreement with the experiment. The results showed that a process model was an excellent tool for quickly and cheaply studying the process behaviour greatly reduced need to execute time-consuming and costly experiments.

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.

Preparation of PMMA/PGMA Blend to Apply for Metallographic Cross Section of Printed Circuit Board

Poly (methyl methacrylate)/poly (glycidyl methacrylate) (PMMA/PGMA) blend was prepared with the reaction of PMMA, glycidyl methacrylate (GMA) and methyl methacrylate (MMA) at room temperature. Effects of the proportions of MMA and GMA were investigated to analyze the performance of PMMA/PGMA blend. When the weight fraction of GMA in GMA/MMA was 0.25, PMMA/PGMA blend exhibited good performance as curing time of 29 min, volume shrinkage of 9.83%, bending strength of 50 MPa, tensile strength of 31 MPa and bonding strength of 1.52 MPa. PMMA/PGMA blend could well cover the cross section of printed circuit board. Introduction Printed circuit board (PCB) is an indispensable module for signal transmission of electronic products .PCB quality at each process should be monitored to finally obtain reliable PCB structure due to the limitation of its complex manufacture processes [1]. Metallographic cross section of PCB is a useful method to directly observe the inside structure of PCB to find out the defects of delamination, skip plating, undercut, conductive anodic filament and copper migration etc [2].However, the fixation of PCB section is hard to be completed to avoid the structure damage after cutting a local segment from the whole PCB. Cold mounting is generally used for the fixation of PCB section since PCB section can be stable without the influence of outside pressure, heat and deformation during its grinding process. Epoxy resin for cold mounting is not suitable for quick observation of PCB section since the reaction of epoxy monomer needs long curing time (more than 12 h) under the presence of organic amine catalyst. Thus, other polymer system should be found to meet the requirement of quick evaluation of PCB section. Methacrylate monomer could exhibit short copolymerization time at room temperature so. In this paper, poly (methyl methacrylate)/poly (glycidyl methacrylate) (PMMA/PGMA) blend was prepared for the application of the fixation of PCB section. The performance of PMMA/PGMA blend was investigated to examine its compatibility of cold mounting for PCB-section observation. 3rd Annual International Conference on Advanced Material Engineering (AME 2017) Copyright

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.

Pre-curing investigation of filling conductive paste in prepreg to interconnect two multilayer structures of backboard for press-fit application

Purpose The purpose of this paper is to form high density interconnection (HDI) of backboard for press-fit applications with the pre-curing conditions of conductive paste. The best condition of pre-curing conductive paste should be found to obtain good electrical and physical performance of the conductive paste and avoid the simultaneous curing behavior of prepreg. Design/methodology/approach A novel structure of backboard was designed by using the connection of conductive paste-filled through holes to connect two multilayers. Pre-curing conditions of conductive paste were investigated to find their effects on resistance, bond strength and volume shrinkage. The reliability of pre-curing conductive paste was also analyzed. Findings Pre-curing conditions led to a great influence on the resistance, bond strength and volume shrinkage of the conductive paste. The best condition of pre-curing conductive paste was chosen as the low curing temperature of 60°C and a curing time of 30 min. Cured conductive paste exhibited square resistance of 4.205 mΩ/□ and bonding strength of 22.86 N. The as-obtained pre-curing condition could improve the reliability of conductive paste. Pre-curing process of conductive paste at extremely low temperature to interconnect two multilayer structures improved the density interconnection of backboard for press-fit applications. Originality/value The use of HDI of backboard could lead to good assembly for high-speed signal transmission of electronic products with press-fitting components. The connection of pre-curing conductive paste for multilayers could have important function for improving the application for communication backboard.

Bottom-up copper plating to form stacked interconnection of HDI printed circuit board for optical module application

Plating factors of graphic design of copper patterns and plasma pretreatment of dry film were investigated to find their effects on bottom-up plating quality of copper pillars. The thickness of copper pillars is examined using scanning electron microscope. John’s Macintosh Product software is used to analyze the thickness distribution of the copper pillars on the surface of the base board. Graphic design of less copper pillars in the surface, dry film with the thickness of 100 μm and two-time plasma pretreatment of dry film could result in good plating pillars for stacked interconnection of printed circuit board (PCB). High density interconnection (HDI) PCB can lead to high-speed signal transmission during optical module application.

Effects of additives on filling blind vias for HDI manufacture

Copper electrodeposition from chloride-containing and chloride-free copper plating solutions was investigated. Effects of carrier, brightener and leveler on the filling power of copper deposits in blind via were investigated by response surface design. Metallurgical microscopy was used to measure the filling power. Design-expert software was used to obtain and analysis the regression equation for the filling power as the response to organic additives. An extra experiment was completed to verify the optimized condition. The results showed that chloride-ion-containing plating solution exhibited a higher filling power, compared to the case without chloride ions. The optimum conditions of each additive were obtained as the concentrations of brightener, leveler and carrier at 0.92 mL/L, 12.7 mL/L and 12.7 mL/L, respectively. The filling power of copper deposits was high at the optimum condition. The filling power of copper deposits for blind via was 97.38%, indicating less difference from that of the model value at 97.45%.

Copper coin-embedded printed circuit board for heat dissipation: manufacture, thermal simulation and reliability

Purpose – The purpose of this paper is to form copper coin-embedded printed circuit board (PCB) for high heat dissipation. Design/methodology/approach – Manufacturing optimization of copper coin-embedded PCB involved in the design and treatment of copper coin, resin flush removal and flatness control. Thermal simulation was used to investigate the effect of copper coin on heat dissipation of PCB products. Lead-free reflow soldering and thrust tests were used to characterize the reliable performance of copper coin-embedded PCB. Findings – The copper coin-embedded PCB had good agreement with resin flush removal and flatness control. Thermal simulation results indicated that copper coin could significantly enhance the heat-dissipation rate by means of a direct contact with the high-power integrated circuit chip. The copper coin-embedded PCB exhibited a reliable structure capable of withstanding high-temperature reflow soldering and high thrust testing. Originality/value – The use of a copper coin-embedded PCB could lead to higher heat dissipation for the stable performance of high-power electronic components. The copper coin-embedded method could have important potential for improving the design for heat dissipation in the PCB industry.