Surface Mount Technology Production Research Articles

The preparation and wettability of the Sn-9Zn-2.5Bi-1.5In solder paste for SMT process and high shear ball performance

Purpose This study aims to focus on the surface mount technology (SMT) mass production process of Sn-9Zn-2.5Bi-1.5In solder. It explores it with some components that will provide theoretical support for the industrial SMT application of Sn-Zn solder. Design/methodology/approach This study evaluates the properties of solder pastes and selects a more appropriate reflow parameter by comparing the microstructure of solder joints with different reflow soldering profile parameters. The aim is to provide an economical and reliable process for SMT production in the industry. Findings Solder paste wettability and solder ball testing in a nitrogen environment with an oxygen content of 3,000 ppm meet the requirements of industrial production. The printing performance of the solder paste is good and can achieve a printing rate of 100–160 mm/s. When soldering with a traditional stepped reflow soldering profile, air bubbles are generated on the surface of the solder joint, and there are many voids and defects in the solder joint. A linear reflow soldering profile reduces the residence time below the melting point of the solder paste (approximately 110 s). This reduces the time the zinc is oxidized, reducing solder joint defects. The joint strength of tin-zinc joints soldered with the optimized reflow parameters is close to that of Sn-58Bi and SAC305, with high joint strength. Originality/value This study attempts to industrialize the application of Sn-Zn solder and solves the problem that Sn-Zn solder paste is prone to be oxidized in the application and obtains the SMT process parameters suitable for Sn-9Zn-2.5Bi-1.5In solder.

Investigation of solder beading phenomenon under surface-mounted electrolytic capacitors

PurposeThe purpose of this paper is to study the solder beading phenomenon (referring to larger-sized solder balls) of surface-mounted electrolytic capacitors. Solder beading could induce failures by violating the minimal electrical clearance on the printed circuit board (PCB). In modern lead-free reflow soldering, especially in high-reliability industries, such as automotive, aeroplane and aerospace, detecting and preventing such defects is essential in reliable and cost-effective manufacturing.Design/methodology/approachThe large size of the involved components may block the view of automatic optical inspection; therefore, X-ray inspection is necessary. To detect the failure mode, X-ray imaging, cross-section grinding, optical microscopy and Fourier transformed infrared spectroscopy were used. High-resolution noncontact profilometry and optical microscopy were used to analyse component designs. The surface mounting process steps were also analysed to reveal their dependence on the issue. Test methods were designed and performed to reveal the behaviour of the solder paste (SP) during the reflow soldering process and to emphasise the component design relevance.FindingsIt was found that the reduction of SP volume only reduces the failure rate but does not solve the problem. Results show that excessive component placement pressure could induce solder beading. Statistical analysis revealed that differences between distinct components had the highest effect on the solder beading rate. Design aspects of solder beading-prone components were identified and discussed as the primary source of the problem.Practical implicationsThe findings can be applied in surface-mount technology production, where the total failure count and resulting failure costs could be reduced according to the findings.Originality/valueThis paper shows that component design aspects such as the low distance between the underside of the component and the PCB and blocked proper outgassing of volatile compounds of the SP can be root causes of solder beading under surface-mounted electrolytic capacitors.

Optimization of the Rapid Design System for Arts and Crafts Based on Big Data and 3D Technology

In this paper, to solve the problem of slow design of arts and crafts and to improve design efficiency and aesthetics, the existing big data and 3D technology are used to conduct an in-depth analysis of the optimization of the rapid design system of arts and crafts machine salt baking. In the system requirement analysis, the functional modules of this system are identified as nine functional modules such as design terminology management system and external information import function according to the actual usage requirements. In the system design, the overall structure design, database design, and functional module design of the system are comprehensively elaborated, and the key issues such as 3D display and home layout generation algorithm based on reinforcement learning are analyzed and designed. In the implementation part of the system, the overall construction of the system and the composition of functional modules are introduced in detail and the main functional modules of the system are presented with interface diagrams. In the system implementation part, the overall system construction and functional module composition are introduced in detail, the main functional modules of the system are shown with interface diagrams, codes, and algorithms, and the specific implementation process of 3D display and soft layout algorithms are also explained in detail. The process of Surface Mount Technology (SMT) big data processing and analysis is designed, and the design of SMT production line data collection scheme and real-time data processing architecture is completed. Based on the characteristics of SMT production line data, the K-means algorithm is used to detect data outliers and verify the accuracy of the method; also, the Spark-based association rule printing parameter recommendation model is designed, and the efficiency of the Apriori algorithm is significantly improved by parallelization.

Predicting the printed circuit board cycle time of surface-mount-technology production lines using a symbiotic organism search-based support vector regression ensemble

This paper presents a symbiotic organism search (SOS)-based support vector regression (SVR) ensemble for predicting the printed circuit board (PCB) cycle time of surface-mount-technology (SMT) production lines. Being able to predict the PCB cycle time accurately is essential for optimising the SMT production schedule. Although a machine simulator can be reliably used for single-type PCB production, it is time-consuming and often inaccurate for the simulator to be applied for highly mixed orders in multiple flexible SMT production lines. Due to the dynamic changes in both PCB orders and SMT production lines, there is a diverse set of samples, but the size of similar samples is relatively small. An SVR model is therefore used to estimate the PCB cycle time, and the SOS algorithm is employed to optimise the SVR parameters. We assume that uncertainties during the assembly process can be captured by the characteristics of PCB and SMT lines, which are utilised as features to train the SVR model. To enhance the performance of the prediction accuracy, an SOS-SVR ensemble is proposed. Experiments based on datasets collected from a leading global electronics manufacturer confirm the efficiency of the proposed approach compared to industrial solutions currently in place and other machine learning methods.

Design and Experiment of a Solder Paste Jetting System Driven by a Piezoelectric Stack.

To compensate for the insufficiency and instability of solder paste dispensing and printing that are used in the SMT (Surface Mount Technology) production process, a noncontact solder paste jetting system driven by a piezoelectric stack based on the principle of the nozzle-needle-system is introduced in this paper, in which a miniscule gap exists between the nozzle and needle during the jetting process. Here, the critical jet ejection velocity is discussed through theoretical analysis. The relations between ejection velocity and needle structure, needle velocity, and nozzle diameter were obtained by FLUENT software. Then, the prototype of the solder paste jetting system was fabricated, and the performance was verified by experiments. The effects of the gap between nozzle and needle, the driving voltage, and the nozzle diameter on the jetting performance and droplet diameter were obtained. Solder paste droplets 0.85 mm in diameter were produced when the gap between the nozzle and needle was adjusted to 10 μm, the driving voltage to 80 V, the nozzle diameter to 0.1 mm, and the variation of the droplet diameter was within ±3%.

Research on Component Allocation Problem for Chip Mounter Based on MATLAB

With the widespread use of the Surface Mount Technology (SMT) in electronics assembly, the efficiency of SMT production line is the most important to increase the number of products quickly, enhance the market share and competitive strength. And the key point of efficiency improvement for SMT production line is the reasonable component distribution in chip mounter. In this paper, for a widely used SMT production line, its mathematical model of component distribution for two chip mounters was established. By identifying the model constrains and processing of the mathematical model, then the mathematical model was solved through Particle Swarm Optimization (PSO) based on natural selection with MATLAB. By contrast with the MATLAB function-bintprog solving, the results by PSO based on natural selection needs less iteration and short time, and the optimal component distribution program was efficiently obtained.

A study of SnAgCu solder paste transfer efficiency and effects of optimal reflow profile on solder deposits

The reliability of solder joints in electronic products are greatly enhanced by good stencil printing and quality reflow soldering. The stencil printing process is widely used in Surface Mount Technology (SMT) to deposit solder paste on the substrate and is a critical step in SMT assembly as it has been widely claimed that up to 50% of the defects found in the assembly of printed circuit boards (PCBs) are attributed to stencil printing. Solder paste release from stencil during printing is a key factor which affects the quality of solder prints. Thus, the efficient transfer of paste from stencil through aperture to pad is a fundamental concern in SMT production process. The recent trends on further miniaturisation of electronic products have introduced more process challenges in the SMT assembly. The assembly of surface mount packages such as flip chips, chip scale packages and fine pitch ball grid arrays are challenging the current stencil printing and reflow profiling capabilities. The effective mounting of these miniaturised packages requires good transfer efficiency of solder paste through small stencil aperture. As further electronic product miniaturisation culminates in progressive use of decreasing stencil aperture sizes, the in-depth understanding of the dependency of transfer efficiency of solder paste on diminishing stencil aperture areas has become vital to improving solder joint reliability. This study investigates the transfer efficiency of type 3, 96.5Sn3.0Ag0.5Cu solder paste through linearly decreasing rectangular stencil aperture sizes typically used in PCB assembly. In addition, the research examines the effects of optimal reflow profile (ORP) on the solder deposit volumes. The results from the study show a power law relationship between actual solder deposit volume (SDV) and aperture cavity. The observed effect of ORP on actual SDVs was a 46% volume change which was fairly constant across the pad geometries. Our study shows that the transfer efficiency of solder paste decreases with decreasing stencil aperture size. A novel mathematical model η T = 100 e - | V A - V C | ∗ | V A - V C + D m + e 10 - 5 D m - 1 | for V C ⩾ 0 is proposed for computing the transfer efficiency of solder paste through rectangular stencil aperture sizes.

Production planning for surface mount technology lines

A mathematical programming model is reported that can be used to support a key decision associated with production planning and control of surface mount technology production lines in certain environments. After a brief introduction on the nature of surface mount technology products and processes, a hierarchical view of surface mount technology production planning and control is presented, which in turn is used to organize a brief review of other published work on surface mount technology optimization. Following this, a mathematical programming model to support the making of decisions at one of the levels in the hierarchy, that concerned with allocating production lots to surface mount technology lines, is described in detail. Example results from using the model are given as well as conclusions about its value and future extensions.

Applications of neural networks to solving SMT scheduling problems a case study

In today's surface mount technology (SMT) production systems, an SMT assembly line is designed to produce different types of products. The system setup cost is often sequence dependent and the job sequence has significant impact on the productivity of these systems. In this paper, a nonlinear mixed integer programming model was proposed to generate production sequence and to minimize total setup cost for a small size SMT production line in Western Canada. A neural-network approach was employed to solve this case problem. Problem features and detailed results are presented to illustrate the model and the solution approach.

Optimization of high-speed multistation SMT placement machines using evolutionary algorithms

Surface mount technology (SMT) is a robust methodology that has been widely used in the past decade to produce circuit boards. Analyses of the SMT assembly line have shown that the automated placement machine is often the bottleneck, regardless of the arrangement of these machines (parallel or sequential) in the assembly line. Improving and automating the placement machine is a key issue for increasing SMT production line throughput. This paper presents experimental results using genetic algorithms to optimize the feeder slot assignment problem for a high-speed parallel, multistation SMT placement machine. Four crossover operators, four selection methods, and two probability settings are used in our experiments. A penalty function is used to handle constraints. A comparison of genetic algorithms with several other optimization methods (human experts, vendor supplied software, expert systems, and local search) is presented, which supports the use of genetic algorithms for this problem.

Comparison study of scheduling rules and set-up policies for a SMT production line

This paper examines the effects of some independent variables on the performance of an electronic manufacturing Surface Mount Technology (SMT) production line operating in a highly dynamic environment. Variables considered are: scheduling rules and set-up policies. Experimental design, ANOVA and simulation techniques (Awesim, C) are used in order to predict the performance of a SMT line on the work-in-process, the throughput time and set-up time.

SMT production scheduling: a generalized transportation approach

Abstract A generalized transportation model is first formulated for the scheduling of Surface Mount Technology (SMT) production. Its dual form is next discussed. By specially coding the SMT scheduling problem, it is unnecessary to develop the constraint matrix for the dual. The simplex method is not applicable for this problem due to its sparse data structure. An efficient algorithm for the dual model is then developed from the idea of the revised simplex method. To illustrate the algorithm, a numeric example is presented.

How to Use Automated X‐ray Inspection for Process Monitoring and Control

The initial excitement over increased solder joint densities, higher manufacturing throughput, and superior electrical performance brought forth by surface mount technology (SMT) has been replaced by frustrations over lower yields and the inherent difficulties of inspecting hidden solder joints. In the plated through hole (PTH) process, rework and inspection tasks were not only relatively easier tasks, but also less costly. The high cost of inspecting and reworking SMT assemblies dictates a rethinking of the assembly process. Increasing first time yields becomes the key to reducing SMT inspection and rework costs. In a high volume facility, a 100% visual inspection process is not feasible because of the high cost of inspection and rework. However, if a company intends to remain competitive, inspection and rework must be reduced without a sacrifice to final product quality. Realising that it is not possible to ‘inspect’ quality into a product, improved yield must result from a controlled process environment. By maintaining a controlled environment, one will be provided with lower inspection costs, lower rework costs, lower scrap and, in the final analysis, improved product quality. At the heart of any process control environment should be a real‐time process control system designed specifically to accommodate SMT process defects. Process monitoring is accomplished by locating and identifying SMT process flaws. These flaws will then be reported to a host system for statistical analysis. These are statistical data used to make timely adjustments to the various stages of the assembly process in a real‐time manner. Being able to monitor the production process objectively in real time, and detect hidden flaws accurately, are the keys to having a successful process inspection system. Automated X‐ray Inspection is gaining acceptance as a viable process monitoring tool, capable of detecting and reporting SMT process flaws, including those hidden flaws not reported with typical visual inspection systems. The purpose of this paper is to show how an Automated X‐ray Inspection system can be integrated into the SMT production process as a cost‐effective method for improving SMT yield.