Surface Mount Research Articles

A framework with revised rough-DEMATEL to capture and evaluate requirements for smart industrial product-service system of systems

Smart industrial product-service system of systems (SiP-S3) is a new extension of industrial PSS via smart technology and SoS (system of systems) engineering. A framework with revised rough-DEMATEL method is proposed to capture and evaluate requirements for SiP-S3. From the various interactions in value stream mapping of SiP-S3, business, functional and non-functional requirements can be captured and converged into SiP-S3 requirements. Due to the interrelation between requirements of SiP-S3 and uncertainty of expert judgments, rough-DEMATEL is adopted but is revised in two aspects. Generally, SiP-S3 requirement items are plentiful, a set of programming code for rough set approximation is firstly given to reduce manual calculation burden. Moreover, compared to multiple operators of modified-CFCS (converting fuzzy values into crisp scores) plus SVL (single vector-length), a feasible and simpler operator of AVL (average vector-length) on rough-prominence and rough-relation is firstly devised to prioritise requirements. As such, roughness can be remained till at the end of calculation procedure to avoid uncertain assessment information loss. Surface mount technology (SMT) is not trivial in electronic manufacturing service industry, an illustrative case study of SMTE-S3 (SMT equipment-service system of systems) is demonstrated to verify feasibility and potential of proposal methodological framework.

Design of a bi-manual haptic interface for skill acquisition in surface mount device soldering

PurposeOffering unskilled people training in engineering and vocational skills helps to decrease unemployment rate. The purpose of this paper is to augment actual hands-on conventional vocational training methods with virtual haptic simulations as part of computer-based vocational education and training.Design/methodology/approachThis paper discusses the design of a bi-manual virtual multi-modal training interface for learning basic skills in surface mount device hand soldering. This research aims to analyze human hand dexterity of novices and experts at micro level skill knowledge capture by simulating and tracking the users’ actions in the manual soldering process through a multi-modal user interface.FindingsHaptic feedback can enhance the experience of a virtual training environment for the end user and can provide a supplementary modality for imparting tangible principles to increase effectiveness. This will improve the teaching and learning of engineering and vocational skills with touch-based haptics technology, targeted toward teachers and students of various disciplines in engineering. Compared with the traditional training methods for learning soldering skills, the proposed method shows more efficiency in faster skill acquisition and skill learning.Originality/valueIn this study, the authors proposed a novel bi-manual virtual training simulator model for teaching soldering skills for surface mount technology and inspection. This research aims to investigate the acquisition of soldering skills through virtual environment, with and without haptic feedback. This acts as a basic-level training simulator that provides introductory training in soldering skills and can help initially unskilled people find educational opportunities and job offers in the electronics industry.

Effect of thixotropic agents on the rheology of SnAgCu lead-free solder pastes used for jet printing

Solder paste is the most important strategic bonding material for surface mounting components in electronics manufacturing field. The aim of this study was to investigate the effect of thixotropic agents on the rheology of SnAgCu lead-free solder pastes and grope for materials suitable for jet printing process. The rheological behaviors consisting of viscosity, oscillation, creep recovery and thixotropy of solder pastes added with four thixotropic agents were investigated. The jet printing test was carried out at room temperature. In this paper, it is found that thixotropic agents ST and CVS can reduce the G″/G′ ratio of solder pastes calculated by the oscillation stress curve. Besides, ST and CVS can effectively improve the area of thixotropic loop and the value of unrecovered stress, which is suitable for the jet printing. T4 samples with CVS can be jetted continuously for more than 5000 points with a minimum diameter of 372.3 μm. As the demand for solid-liquid two-phase fluid materials applied to jet printing increases, rheological methods can assist with the exploration of new high viscosity lead-free solder pastes.

Efficient integration of scalable active‐phased array antenna based on modular approach for MM‐wave applications

AbstractIn this article, efficient integration approach of building large‐scale active‐phased array antenna (A‐PAA) for millimeter‐wave (mm‐wave) is presented. In this approach, large‐scale A‐PAA is constructed from smaller size A‐PAAs (modules) with inter‐element spacing of half‐wave length and assembled into efficient planar waveguide feeding platform based on substrate integrated waveguide (SIW) technology. Simple low profile vertical RF‐connection between the SIW splitter/combiner outputs and the modules using surface mount super‐mini board‐to‐board (SM‐SMC) is presented. Embedded metallic via‐pad transition integrated into the SIW board is employed to match the SM‐SMC to the SIW mode at Ka band. Sixteen‐way power splitter with transitions to SM‐SMCs is designed at 30 GHz. The measured results of S‐parameters show insertion loss of <0.70 dB over the operating frequencies 28.50‐30.50 GHz.

An online machine learning framework for early detection of product failures in an Industry 4.0 context

ABSTRACTCurrent paradigms such as the Internet of Things (IoT) and cyber-physical systems are transforming production environments, where related processes are not only faster and with higher standards, but also more flexible and adaptable to changes in the environment. To address the ever-increasing flexibility requirements while keeping current production standards, a new set of technologies is needed. This paper presents an IoT machine learning and orchestration framework, applied to detection of failures of surface mount devices during production. The paper shows how to build a scalable and flexible system for real-time, online machine learning. Furthermore, the approach is evaluated by using a novel and realistic simulation of a production line for electronic devices as a case study. The system evaluation is done in a holistic manner by analyzing various aspects involving the software architecture, computational scalability, model accuracy, production performance, among others.

Rapid fault cause identification in surface mount technology processes based on factory-wide data analysis

Surface mount technology is an important process in modern electronic circuit manufacturing. Quality control problems have arisen in this area because of the increased design and processing complex...

Design and Modeling of a Compact Partially Transmissible Resistor-Free Absorptive Frequency Selective Surface for Wi-Fi Applications

A compact partially transmissible absorptive frequency selective surface (AFSS) which requires neither surface mount device resistors nor resistive ink is proposed in this communication. The resistor-free AFSS utilizes the lossy characteristic of FR-4 substrate material to achieve the absorption property. The method to efficiently model the AFSS based on physical phenomena has been thoroughly discussed, by which the effect of substrate loss can be predicted accurately. An equivalent circuit model is also presented, and its predicted result agrees well with the full-wave simulation. Furthermore, the fabrication and measurement are also conducted to demonstrate the feasibility of resistor-free AFSS. The highest absorption rate of the AFSS is designed around 2.46 GHz, while at least half-power transmission is guaranteed below 1 GHz. These electromagnetic functions as well as the low fabrication cost and complexity make the resistor-free AFSS a promising candidate for advanced packaging and shielding of mixed signal system.

Experimental setup for anisotropic thermoelectric transport measurements using MPMS

At reduced dimensions the electrical transport properties of materials often depend on the measurement direction. Here we report on a measurement setup designed on the manual insertion utility probe (MIUP) of the Quantum Design’s magnetic property measurement system (MPMS) to measure anisotropic transport properties in the temperature range of 10–400 K and magnetic fields up to 5 Tesla. The setup is capable of measuring the Seebeck coefficient and electrical resistivity both along and perpendicular to the applied magnetic field. The Seebeck measurement is based on the differential measurement technique; the four-probe electrical resistivity measurement can easily be performed on the opposite side of the setup. The setup consists of a small copper cube (5 × 5 × 5 mm3) fitted with diagonally cut electrically insulated square strips. The strips are fitted with copper-constantan thermocouple in differential arrangement for the temperature-gradient (ΔT) measurement and symmetrically arranged surface mount (SM) resistors to create the ΔT across the sample. The cube can be rotated to alter the direction of the applied magnetic field on the sample. We demonstrate the directional dependence of the measured transport properties for a normal platinum wire and for single crystal flakes of CuCr2Se4.

Multi-Objective Optimization Design of Fractional Slot Concentrated Winding Permanent Magnet Synchronous Machines

Fractional-slot concentrated-winding (FSCW) permanent magnet synchronous machines (PMSMs) have several advantages when compared to other conventional topologies. Design of these motors often rely on the designer's experience, or numerical methods which are time inefficient. This makes them unsuitable for multi-objective optimization design procedure in which a huge design space is adopted, and which have been shown to be effective in finding optimum machine designs. This work introduces a generic multi-objective optimization design framework for a surface mounted (SM) FSCW-PMSM based on a general analytical model that considers various machine aspects such as its geometry, winding configuration, losses, iron temporal flux density levels and drive control. The design procedure is demonstrated to design a surface-mounted (SM) FSCW-PMSM motor with a wide constant power speed range of 5:1. Validation is carried out using Finite Element Analysis (FEA) with good agreement in results.

Automated fabrication of multi-layer printed electronic circuits using a novel vector ink-jet printing process control and surface mounting of discrete components

Printed electronics offer great potential for new applications such as Internet of Things devices and wearables. A methodology for integration of design and process assessment based on a stepwise transfer of the circuit to be printed from printed circuit board test vehicles to the final printed substrate is introduced. A multi-layer vector ink-jet printing process with three functional inks is presented using the example of the fabrication of a demonstrator circuit. This fabrication is realized using a newly set up printing system as enabling technology: Integration of a piezo print head into the path planning of the printing system and its control as virtual stepper axis enable highly precise vector printing yielding printed functional elements with low tolerances. Finally, process improvements for assembly of surface mounted devices on printed foil substrates are outlined.

Solder paste wicking in socketable BGAs

The trend of the electronics industry to miniaturize package design has caused the need to adopt BGA packages for a variety of applications. OEM microprocessors have conventionally used LGA designs press fitted into sockets for ease of reworkability. However, BGA packages, which have been widely used for surface mount (SMT) applications, face challenges when they are used in sockets. One of the major challenges faced is the formation of intermetallics between the bare solder ball and the gold paddle of the socket. To address these challenges, Georgia Tech is developing a universal solution for socketing and SMT applications by surface modification of solder spheres. In this new approach, the solder spheres have an outermost noble metal layer which prevents any damage to the BGA and doesn't react with the gold paddle, when placed in a socket. The surface coating would also collapse with the solder ball under specific conditions during reflow when used in SMT applications. This paper focuses on the process of attaching these modified solder spheres on the package and subsequent assembly of the package on the board. We evaluated high and low melting solder pastes to attach the coated spheres to the package. A major challenge observed was the wicking of the solder paste to the entire surface of the solder sphere during reflow. This was addressed by studying the wetting characteristics of the solder paste on different metal surfaces and controlling the volume of solder paste required. Optimization of solder paste volume was done to control wicking and at the same time, achieve a strong and stable joint. Microstructure of the solder joint was analyzed to determine its effect on the joint stability. It was found that the amount of wicking is a strong function of the composition of the solder paste, the reflow time, and the material in surface with which the solder paste is in contact with. This work advances the assembly requirements of socketable BGAs.

A Boosting-Based Intelligent Model for Stencil Cleaning Prediction in Surface Mount Technology

This research proposes a stencil cleaning decision-making model in surface mount technology. Stencil cleaning is a critical process that influences the quality and efficiency of printing circuit boards. Stencil cleaning operation depends on various process variables, such as printing speed, printing pressure, and aperture shape. The objective of this research is to develop an intelligent model to guide stencil cleaning decision-making to reduce process defects. The stencil cleaning process is considered as a sequential detection problem in this study. Based on quality measures of printed historical boards, such as solder paste volume and the number of defects, a novel feature space is proposed by considering both short-term and long-term process trend. A gradient boosting model is applied to make the stencil cleaning decision. To validate the effectiveness of the proposed model, different scenarios are designed in the experimental test. State-of-art data mining models are also compared to the proposed cleaning decision-making model. Experimental results show that the proposed boosting-based intelligent model outperforms other models and can effectively provide the cleaning suggestion even the board design is changed in the future.

Design of Solder Connections for Self-Assembly of Optoelectronic Devices

Abstract In surface mount assembly, advantage is taken of the high surface tension of molten solder to self-align ball grid array packages and flip chip die. However, in these applications, the volume of solder applied as paste by stencil printing is not sufficiently well controlled to achieve the precise alignment required for optoelectronic devices. We believe that the requirement on solder volume control for assembly of optoelectronic devices can be relaxed by designing the bond pads so that the height or alignment of connections is controlled by the surface tension of the solder rather than its volume. Our design approach to accomplishing this is to connect auxiliary pads to the primary attachment pad, which act as solder reservoirs. Surface tension causes the solder to be redistributed among these pads to achieve a uniform pressure throughout the solder volume. This phenomena is governed by the Young-Laplace equation, ΔP = γκ, in which ΔP represents the difference in pressure within and outside the solder, γ the surface tension of the solder, and κ the local curvature of the solder surface. Thus, the design of the set of primary and auxiliary pads is critically important to realizing the desired control of joint height. In this article, we describe the use of the Surface Evolver software package in combination with analytical models, to analyze the behavior of various connection configurations with respect to variations in printed solder volume. Specifically, we calculate the equilibrium shape of the solder surface over the connected set of pads and examine how control of joint height is affected by the number, size, and geometry of auxiliary pad configurations.

Dynamic Predictive Modeling of Solder Paste Volume with Real Time Memory Update in a Stencil Printing Process

This research aims to develop a dynamic prediction model to assist real-time decision making of a stencil printing process by maintaining high prediction accuracy of the printing process. In a Surface Mount Technology (SMT) assembly line, the stencil printing process (SPP) accounts for more than 50% of the defectiveness of printed circuit boards (PCBs). During the printing process, environmental changes such as humidity or wear of blades may induce the PCBs printing results to deviate from the target volume. Thus, real-time adjustment of the printer settings (e.g., printing parameters, clean cycles, etc.) based on prediction of printing volumes is critical to maintain a high printing performance. However, research has been limited in real time SPP control, which is partially due to the difficulties in predicting the paste volumes with high accuracy and time efficiency. To tackle the challenges, this research proposes novel online learning models for real-time SPP status prediction. The prediction model is implemented by selecting advanced online learning models to estimate the printing volumes in averages and standard deviations (SDs) considering different pad sizes with different clean ages, directions, printer parameters, etc. The model performances are evaluated in Root Mean Square Error (RMS E), R2, etc. From comparison, the Support Vector Regressor (SVR) shows outstanding prediction performance with R2 values of 92% and 81% for volume averages and SDs. This research emphasizes the potential of using online learning as a preliminary process for effective real-scenario SMT assembly dynamic control.

Statistical Analysis for Component Shift in Pick and Place Process of Surface Mount Technology

The placed electronic component can shift on the wet solder paste in pick and place (P&P) process of surface mount technology (SMT). It does not usually attract much attention, because the shift is considered to be negligibly small and the following self-alignment effect in the solder paste reflow soldering process could also make it up. However, with the decreasing size of the electronic components and the increasing demand for the low defective rate of PCB, the component shift in P&P process is becoming more and more important in quality control of SMT industries. Though a few papers are related to the component shift in P&P process, there is no earlier research using the data from the real production line. In this paper, we study two basic and important issues: the behavior of the component shift in P&P process and the contributing factors to it. Several statistical methods are used to explore the behavior component shift based on the data from a complete state-of-the-art SMT assembly line. Main effects and regression analysis are implemented to pinpoint the contributing factors. In order to investigate the issues comprehensively, six types of electronic components and multiple potential factors are considered in this work, e.g., solder paste properties (position, volume, area, height), designed position of the component, placement pressure. The results indicate that component shift cannot be ignored. Also, the position of solder paste, designed position of component and component type are the top three most important factors to study the component shifts in P&P process.

The effect of solder paste volume on surface mount assembly self-alignment

In surface mount assembly, the consistency of solder paste volumes and the placement of the components play a vital role in the movement of the chip components when they go through the reflow soldering process. These movements may lead to common assembly defects such as overhanging, tilting, nonwetting, and tombstoning. Components to be assembled in surface mount assembly have self-alignment nature, which is driven by the total internal energy including gravitational energy, surface tension energy, etc. in the molten solder attributed to various factors. The factors include 1) solder paste composition, surface energy, gravity; 2) process variations such as solder paste volume, solder paste location, the inequality of solder paste volumes at the two terminals of the passive component, and components location and orientation; 3) design parameters such as pad dimension, pad-to-pad spacing, and pad surface finish.In this research, energy-based three-dimensional model is created to predict solder joint profile (shape). Three types of passive chip component are chosen to be the modelling examples to investigate the component self-alignment performance during the reflow soldering process. By nature, the molten solder being a bulk fluid always tends to minimize its internal energy towards mechanical equilibrium and it causes the passive component to move to the state of minimal energy. This movement leads the component to self-align. Thus, by creating an energy minimization model, we can simulate the process of component self-alignment and predict the solder joint profile, final location, and orientation of the passive component.Experimental studies are performed to develop a data-driven prediction model and are compared with the simulated component for validation. The passive components are placed with intended misplacements and their positions are measured before and after soldering. A wide range of surface mount assembly imperfections are considered and intentionally studied to achieve a powerful dataset and better convergence.

Optimization of Passive Chip Components Placement with Self-Alignment Effect for Advanced Surface Mounting Technology

Surface mount technology (SMT) is an enhanced method in electronic packaging in which electronic components are placed directly on soldered printing circuit board (PCB) and are permanently attached on PCB with the aim of reflow soldering process. During reflow process, once deposited solder pastes start melting, electronic components move in a direction that achieve their highest symmetry. This motion is known as self-alignment since can correct potential mounting misalignment. In this study, two noticeable machine learning algorithms, including support vector regression (SVR) and random forest regression (RFR) are proposed as a prediction technique to (1) diagnose the relation among component self-alignment, deposited solder paste status and placement machining parameters, (2) predict the final component position on PCB in x, y, and rotational directions before entering in the reflow process. Based on the prediction result, a non-linear optimization model (NLP) is developed to optimize placement parameters at initial stage. Resultantly, RFR outperforms in terms of prediction model fitness and error. The optimization model is run for 6 samples in which the minimum Euclidean distance from component position after reflow process from ideal position (i.e., the center of pads) is outlined as 25.57 (μm) regarding defined boundaries in model.

Prediction of Component Shifts in Pick and Place Process of Surface Mount Technology Using Support Vector Regression

In pick and place (P&P) process of surface mount technology (SMT) the placed component can shift from its ideal (or designed) position on the wet solder paste. The solder paste with some fluid properties could slump and the unbalance between different sides of solder paste can lead to other forces on the components as well. Though the shifts are usually considered to be negligible and can be made up to some extent by the following self-alignment during the process of soldering reflow, it should be attracted attention as its importance for addressing the quality of the printed circuit board (PCB) in SMT. To minimize or control the component shifts, whose relationship with the characteristics of the solder paste (e.g., offset, volume) should be studied initially. In this paper, we design a comprehensive experiment and collect the data from a state-of-the-art SMT assembly line. Then we use support vector regression (SVR) model to predict the component shifts based on different situations of solder paste and placement settings. Also, two kernel functions, linear (SVR-Linear) and radial basis function (SVR-RBF), are employed. The achieved results indicate that the component shift in P&P process is significant, and the SVR model is highly qualified for the forecast of the component shifts. Particularly, the SVR-RBF model outperforms the SVR-Linear model considering the prediction error.

Effects of Thermal Reflowing Stress on Mechanical Properties of Novel SMT-SREKs

A novel silicone rubber elastic key (SREK) is proposed in this paper for surface mounting technology (SMT) applications. Effects of thermal reflowing stress on the mechanical properties of SMT-SREKs are investigated. The manufactured SMT-SREKs, which underwent various reflowing conditions in advance, are subjected to pressing force and fatigue pressing tests. Fatigue lifetime projection model and its predicted error are then assessed systematically. The thermal degradation of silicone rubber materials is illustrated through the dynamic mechanical analysis and the Fourier transform infrared spectroscopy experiments. The mechanical finite element modeling is also conducted to simulate the pressing process. The results show that the pressing force and tactility of the SMT-SREKs are strongly affected by the reflowing condition, which contributes to the degradation of the silicone rubber materials. During the fatigue pressing test, the change rate of tactility increases with the reflowing peak temperature ( T-{p} ) and is accelerated by the repeated reflowing process. Moreover, a linear model can precisely project the tactility before the fatigue pressing number of 2.0E+6 times, and the impact rate of T-{p} on tactility with the increasing fatigue pressing number can be predicted effectively by using a logarithm model.

The Effect of Solder Paste Volume on Chip Resistor Solder Joint Fatigue Life

The solder joint topology plays a significant role in determining its fatigue life. Due to the complex nature of the actual manufacturing environment, there are variations in solder volume for each joint, which can induce the solder shape variations and misalignment of the chip resistor. The solder shape variation can severely affect its fatigue life. In this study, we use surface evolver software to calculate the solder shape with the global minimum energy. A finite element method was used to model the resistor solder joint under thermal cycling and to predict the fatigue life for different solder paste volumes. Through varying the solder past volume to obtain different solder joint shape, the corresponding fatigue life was predicted. The result could provide a guideline for an/the choosing optimal solder paste volume for surface mount components. Analysis results show that a larger and balanced solder volume can give the best fatigue life under thermal cycling conditions.