Search results

The purpose of this paper is to apply the developed systematic mechanical design methodologies, that are obtained in part I, to investigate their success in designing mechanics of a flexible printed circuit board assembly (PCBA) rework cell.

The decision of soldering and desoldering tool, which is the most critical function of a PCBA rework or remanufacturing cell, significantly influences overall design concept. Therefore, the paper starts by applying the design methodology to the soldering and desoldering function. The same study is repeated for the rest of the sub‐functions but only the results are provided.

An application of rework machine design methodology for the design of a PCBA rework cell has been made available. In addition to this, the embedded knowledge, such as the requirements list, the function structure, the function/means tree, the weighted objective tree and evaluation chart for the soldering and desoldering function are provided.

The paper is the first work providing both embedded knowledge and the application of the systematic design methodology for the design of a fully automated flexible PCBA rework cell. The methodology leads rework machine designers in a well‐controlled and structured design environment.

The design methodology can be applied to all functions or targeted on key weighted areas to ensure that the designed rework machine meets the key areas of concerns. Furthermore, the methodology is generic and may be used to develop other complex manufacturing sytems.

The generic design environment for a flexible printed‐circuit board assemblies (PCBA) remanufacturing cell contains four interrelated complex design domains. Mechanical design domains are really complex and the use of well‐proven mechanical product design methodologies does not help the designer. Hence, this paper aims to develop a generic systematic design methodology for a flexible PCBA remanufacturing cell.

The study investigates the use of conventional mechanical product design techniques for the design of a flexible PCBA rework (remanufacturing) cell. It indicates problems and the weaknesses when conventional product design techniques are used for the development of flexible manufacturing systems (FMS). It then provides a new systematic mechanical design methodology for designing a flexible PCBA rework (remanufacturing) cell. The design methodology is intended to be generic in order to apply successfully to any FMS design.

Conventional product design methodology cannot be used directly for the design of a flexible PCBA remanufacturing cell. Hence, two design methodologies were developed: the generic FMS mechanical design methodology and a specific FMS design methodology for a PCBA rework cell. The first one was developed based on the tasks of the conventional product design process integrated with new design tools. The generic design methodology was then extended to obtain the second methodology for a PCBA rework cell design. Both of the methodologies were applied to a flexible PCBA rework cell design problem. Both design methodologies eliminated unusable design solutions at the early design stages of the conceptual design process and made the design process easier.

The generic and specific design methodologies provide a better design environment, even for less specialized FMS designers.

The design methodologies may help for the commercialization of a flexible PCBA remanufacturing cell that may be used for SM rework and assembly.

Despite continuous efforts in improving process reliability in printed‐circuit board assembly (PCBA), a zero‐defect situation is difficult to achieve because of the complexity of the process and the multitude of components involved. PCBA rework is necessary in many companies due to economic as well as commercial reasons. Presents the intermediate results of a research programme aimed to investigate the technical and economic feasibility of extending the use of a robotic assembly cell to perform single‐board rework. Outlines various manual rework practices and the equipment available. Examines the role of industrial robots and machine vision in PCBA and defines the objectives and overall boundary of the research programme in automatic rework. Describes individual equipment selected to assist the robot, the layout and the manner in which it is used in the cell. Concludes with the development of the cell controller and the methods of equipment integration.

To design a flexible integrated robotic assembly and rework (remanufacturing) cell for assembly, selective assembly and rework of advanced surface mount components (SMCs) using the generic methodology developed in this paper.

Manual rework procedures are investigated for all advanced SMCs. General and specific component‐related rework considerations are obtained and necessary tooling candidates for automation are determined. This is followed by determination of the specific automated rework procedure and selection of suitable tooling for automated robotic rework and generation and evaluation of design concepts.

The developed methodology, which considers the reflow tool at the centre of the development process, has worked well in designing a flexible integrated robotic assembly and rework cell.

This study identified the rework requirements for advanced SMCs, the essential features for rework reflow tools, criteria for comparing reflow tools, and a generic procedure for design and concept selection.

It provides valuable knowledge for designers of flexible integrated robotic assembly and rework cells for assembly, selective assembly and rework of advanced SMCs.

Although rework is labour intensive and conflicts with most modern manufacturing/assembly philosophies, realistic defect levels in surface mount technology (SMT) printed circuit board (PCB) assembly render rework indispensable on the shop floor. Most commercially available rework tools are manual or require very skilled operators for their efficient operation. The challenges of automating SMD rework are significant because the tools, their specifications and rework processes required are not fully understood, and the impact of rework processes on assembly quality and reliability are hotly debated. This paper describes an automated robotic rework cell for SMD and TH boards, and the method used for process characterisation of the solder paste dispensing system. The paper also describes equipment selection, the integration and interfacing of the dispensing equipment to the cell controller and the process characterisation experiments.

Rework is an integral part of printed circuit board assembly (PCBA) manufacturing. However, the state‐of‐the‐art for PCBA rework still relies on operator activity and is therefore semi‐automatic. As a result, the quality of rework depends very much on the skill of the operator. When developing an automatic PCBA rework cell, the cell controller is an essential part which organises and controls the overall rework operation. This paper describes the software modelling of the cell controller for the PCBA rework cell which has been implemented for reworking through‐hole and surface mounted components. The software model is based on hybrid representations and rule‐based control.

The purpose of the present study was to review the thermo-mechanical challenges of reflowed lead-free solder joints in surface mount components (SMCs). The topics of the review include challenges in modelling of the reflow soldering process, optimization and the future challenges in the reflow soldering process. Besides, the numerical approach of lead-free solder reliability is also discussed.

Lead-free reflow soldering is one of the most significant processes in the development of surface mount technology, especially toward the miniaturization of the advanced SMCs package. The challenges lead to more complex thermal responses when the PCB assembly passes through the reflow oven. The virtual modelling tools facilitate the modelling and simulation of the lead-free reflow process, which provide more data and clear visualization on the particular process.

With the growing trend of computer power and software capability, the multidisciplinary simulation, such as the temperature and thermal stress of lead-free SMCs, under the influenced of a specific process atmosphere can be provided. A simulation modelling technique for the thermal response and flow field prediction of a reflow process is cost-effective and has greatly helped the engineer to eliminate guesswork. Besides, simulated-based optimization methods of the reflow process have gained popularity because of them being economical and have reduced time-consumption, and these provide more information compared to the experimental hardware. The advantages and disadvantages of the simulation modelling in the reflow soldering process are also briefly discussed.

This literature review provides the engineers and researchers with a profound understanding of the thermo-mechanical challenges of reflowed lead-free solder joints in SMCs and the challenges of simulation modelling in the reflow process.

The unique challenges in solder joint reliability, and direction of future research in reflow process were identified to clarify the solutions to solve lead-free reliability issues in the electronics manufacturing industry.

Component removal for rework and repair is traditionally achieved by re‐melting of the solder, but the exposure of the assembly or its component parts to repeated soldering/ desoldering cycles may cause both immediate damage and create a significant long term reliability hazard. Rework is labour intensive and requires skilled operators. Area array components further increase the complexity of the rework process because of the number and inaccessibility of the solder joints. There is a growing requirement to recycle/reclaim electronic waste, creating the need for an effective process for dismantling of printed circuit board assemblies (PCBAs). This paper will present a brief review of alternative non‐thermal techniques for rework or dismantling of conventional soldered assemblies, including both chemical etchants and mechanical techniques. Results will then be presented on trials of chemical etchants, where rates of solder removal consistent with realistic times for component removal have been readily achieved using commercially available tin‐lead strippers. Electrochemical techniques are also shown to be usable in specific applications, i.e. where electrical contact can be readily made to the solder joints to be removed, and have the advantage of reclaiming the removed solder directly from the electrolyte.

This paper aims to focus on integrating a lean framework in a high-mix-low-volume (HMLV) printed circuit board assembly (PCBA) environment to enhance current assembly processes and facility layouts. An HMLV PCBA environment is characterized by stochastic demands, a variety of products in terms of shapes and sizes and different sequences of assembly and test operations, in addition to long cycle times and high fall-out rates.

Preliminary analysis indicates that the push inventory control system led to the longer cycle times, such that various lean methodologies have been applied to enhance the assembly operations. In this research, Kanban sizes for different assembly lines are also estimated to integrate and implement a “pull-system” into the lean framework. In addition, material movement and facility layout have been studied to minimize work-in-process travel time. An “iterative-MAIC” approach has been applied to implement lean principles.

As a result, a lean manufacturing pilot line has been implemented to evaluate the effectiveness of the lean principles before rolling them out across the manufacturing floor. It has been shown that the cycle times of the pilot line products are decreased by 40 per cent and the number of defects decreased by 10-30 per cent, depending on different assembly processes, after the lean implementation.

There is limited literature that addresses lean transformation in an HMLV electronics manufacturing service provider handling several product types with different testing methodologies, frequent product revision changes and higher fall-out rates. Hence, in this research, lean manufacturing has been implemented in an HMLV PCBA environment, which has the challenges of varying demand with a mix of assembly and test operations for different product families.

There are three distinct functions in the product realisation chain (product design, process design, and process execution) and thus there are two interfaces (product design – process design; process design – process execution) rather than one (product – manufacturing). This fact supports a need to shift from dyadic relationships to triadic relationships and from the traditionally single interface concept of design for manufacture (DFM) to multiple “design for” elements. This study seeks to discuss this issue.

Through an in – depth case study in an electronics plant and qualitative data analysis, we reveal the existence and functions of these “design for” elements are revealed, and also the link between the implementation of these elements to the levels of process engineering capability.

Proactive and capable process engineering allows improvement of technical coordination among functions. This enables the “design for” mechanisms for both upstream elements (product design) and downstream elements (process execution); this has a positive impact on the performance of product realisation (especially time to market) and thus operational competitiveness.

Since this is a single case study, future empirical research with larger sample sizes should provide further validation of these findings and demonstrate better generalisability of developed concepts.

This paper highlights several initiatives, conceptually linked to the appropriate “design for” elements, which may be applied in manufacturing settings to support product realisation objectives. Process design, as a significant and proactive intermediate component, should be given sufficient attention and investment.

The study expands the existing DFM concept to several new “design for” concepts and discusses some implementation‐related issues.