Optimization of the assignment of circuit cards to assembly lines in electronics assembly

Process planning is an important and integral function for ensuring efficient operations in printed circuit card assembly systems. This paper presents a new approach for solving the circuit card to assembly line assignment problem to minimize assembly time. This problem occurs frequently in process planning for electronic assembly systems and involves considering other interelated process planning problems. The line assignment problem is formulated as a large-scale mixed-integer programming problem and then solved using problem decomposition along with the branch-and-bound algorithm. Techniques for improving the solution time are discussed, and the solution approach is demonstrated using industry representative data sets from Lucent Technologies. For the data sets considered, the solution approach provides solutions within 3% of optimal in approximately 6 min of computation time on a Sun UltraSparc 2 Workstation. The solution approach developed for addressing the line assignment problem can serve as a useful decision-support tool by offering significant opportunities to improve the productivity and throughput of the assembly lines with improved process plans. The approach also allows planning engineers to respond faster to changes in production requirements. This research will be of interest to researchers in printed circuit card assembly systems and to practitioners in both original equipment manufacturing and contract assembly firms.     

Component allocation to balance workload in printed circuit card assembly systems

Component allocation in printed circuit card assembly systems is a special case of the classical mixed-model assembly line balancing problem and involves assigning component types to machines to achieve specific production objectives. In this paper the component allocation problem is considered for the scenario where there are two or more placement machines (possibly nonidentical) and the objective is to balance, for every card type, a combination of the card assembly time and the machine setup time. A mathematical formulation of the problem is developed for a class of placement machines. Two alternative solution approaches are presented: a list-processing-based heuristic for a simple version of the problem, and a linear-programming-based branch-and-bound procedure for the general component allocation problem. Industrial case study results are presented for each approach that indicate expected throughput improvements of up to 8-10% over the company's current procedure, with much less direct effort required by the process engineer.     

Process and production planning for circuit board assembly

Process planning output can be post-processed into criteria for job scheduling decisions in printed circuit board assembly using surface-mount technology (SMT). Artificial intelligence-based techniques used in computerized planning and scheduling systems in other industries can be extended to printed circuit board operations. These techniques include blackboard architectures, object-oriented programming systems, and nonmonotonic reasoning systems. These techniques were used to demonstrate a unique architecture of blackboard systems that communicate via object-oriented messages to arrive at a shop-floor process plan and production schedule. The methodology was specialized to the assembly of printed circuit boards using surface-mounted components in a high-variety/low-volume product mix. The assembly facility was represented as a hierarchical object of product, process, and organizational knowledge. The system of working heuristics was integrated within a prototype environment with the practitioners that assisted in its development. The end result is a good working methodology for system development, implementation, and maintenance by knowledge worker involvement.     

A simultaneous-mounting process for automated printed circuit board assembly

Current robotized printed circuit board assembly systems allow one component to be inserted onto the board at a time and the corresponding design usually causes complicated operation planning problems for plant engineers. This paper addresses an opportunity for productivity improvement in automated printed circuit board assembly through the design of a new assembly mechanism from plant engineer's viewpoint. The mechanism not only will allow simultaneous insertions of multiple components but also will simplify the component placement planning task.     

PCB assembly scheduling for collect-and-place machines using genetic algorithms

In printed circuit board (PCB) assembly, collect-and-place machines, which use a revolver-type placement head to mount electronic components onto the board, represent one of the most popular types of assembly machinery. The assignment of feeders to slots in the component magazine and the sequencing of the placement operations are the main optimisation problems for scheduling the operations of an automated placement machine. In this paper, we present different genetic algorithms (GAs) for simultaneously solving these highly interrelated problems for collect-and-place machines in PCB assembly. First we consider single-gantry machines as the basic type of machinery. In the conventional GA approach all placement operations and the feeder-slot assignment are represented by a single chromosome. In order to increase the efficiency of the genetic operators, we present a novel GA approach, which integrates a clustering algorithm for generating sub-sections of the PCB and grouping the corresponding placement operations. It is shown that the proposed GAs can be extended to schedule dual-gantry placement machines, which are equipped with two independent placement heads and two dedicated component magazines. Hence, component feeders have to be allocated between the two magazines. To solve this allocation problem, two different heuristic strategies are proposed. Finally, detailed numerical experiments are carried out to evaluate the performances of the proposed GAs.     

Solderability and its measurement

The ease with which molten solder wets and spreads on the appropriate metallic surfaces of electronic component assemblies during the manufacturing process is referred to broadly as the solderability of the component or printed circuit board. Two needs are evident: a traceable solderability measurement method giving reproducible data that predict process performance, and an agreed level of solderability which, for a given manufacturing process, will deliver an acceptably robust solder joint. This paper describes briefly present understanding of the mechanisms that govern solderability and the measurement methods most likely to prove acceptable to the electronics assembly industry     

浮式液化天然气用印刷板路换热器研究和应用进展

印刷板路式换热器凭借其紧凑、高效、可靠的特点能够满足海上浮式天然气液化的主低温换热器的需求,近几年逐渐成为海上浮式天然气液化的主低温换热器的首选。本文对近几年印刷板路式换热器的研究进展进行了综述,包括印刷板路式换热器的基本原理、基于扩散焊接的制造工艺、传热和流动特性、换热器机械特性等;总结了印刷板路式换热器在海上浮式液化天然气中的应用现状以及亟需攻克的关键技术,包括热力设计、制造工艺、检测技术。     

Efficient operation methods for a component placement machine using the patterns on printed circuit boards

Operation of a PCB assembler is complicated to optimise since it requires simultaneous consideration of a component's rack assignment and component mounting sequencing. However, most previous researches considered the constraints separately on the optimisation process. Two different methods using special features on printed circuit boards are developed and presented in this research. Based on results from field surveys, it is found that identical components are positioned closely with each other or identical single boards are repeatedly printed on one big board to enlarge up to a proper size to be assembled in the machine. These patterns are adapted on the design of assembly methods to increase productivity. Simulation models are constructed using Visual C++ for performance evaluation purposes of the developed heuristics.     

Detection of capacitor electrolyte residues with FTIR in failure analysis

Detecting leakage from liquid aluminum electrolytic capacitors is not easy. Typically there is very little evidence of leakage because the electrolyte is volatile and leaves behind only trace residues. Liquid aluminum electrolytic capacitors are known to cause catastrophic failures where there is complete loss of functionality due to a short or open circuit. In the study presented in this paper, printed circuit board assemblies from a test and measurement system used in a clean room environment failed. Two units failed, causing burning in a particular area on the printed circuit board assembly. The failure area included several surface mount liquid aluminum electrolytic capacitors, and several others were mounted very close to the burnt region. A study was initiated to evaluate the cause of failure. Careful optical inspection revealed some residues on the outer side of the rubber seals of two of the electrolytic capacitors. Through using Fourier transform infrared analysis and a process of experimentation and analysis, it was determined that the residues were produced by liquid electrolyte that leaked out of the capacitor at some point in the field. The leaked electrolyte that came out of the capacitor was believed to be the cause of failure that led to the burning of the printed circuit board assembly.     

Simulation-based performance analysis and optimization of electronics assembly equipment

Due to the high degree of automation in modern printed circuit board (PCB) assembly, production planning and scheduling in this industry relies heavily on the accuracy of the underlying models of the automated machinery. In this paper, the derivation of such mathematical models is exemplified for one of the most wide-spread machine types (the so-called chip shooter). Moreover, a simulation system for practical use in the electronics assembly is presented which incorporates various types of assembly machines. It serves as a tactical production planning aid as well as a test field for the analysis of the kinematic processes of PCB assembly machines. Such simulation, tailored to the specifics of a production environment, gives reliable estimates of the achievable production volume. Considerable deviations between the performance figures provided by the machine supplier and the actual result can thus be explained, and potential assembly system configurations be compared by drawing on reliable measures. Since the equipment is modelled at a level which takes precise account of its specific kinematics, a detailed analysis of the operations of the individual machine can also be performed revealing potential bottlenecks in its design. These insights are used to optimize machine design and control. Methods based on graph theory as well as on modern numerical search algorithms have been developed for the latter purpose. They lead to considerable performance improvements.     

RESEARCH DIRECTIONS IN ELECTRONICS MANUFACTURING

The Workshop on Electronics Manufacturing Research was held in College Station, Texas, on February 24-26, 1992. It focused on the Industrial Engineering/Operations Research/Management Science disciplines and their capabilities in modeling, analysis, and manufacturing technology. The primary goal was to identify the critical research needs in electronics manufacturing and assembly that can be addressed by these disciplines and the means of accomplishing them.

Sponsors included the Production Systems Program of the National Science Foundation (NSF), three organizations at Texas A&M University (the Department of Industrial Engineering, the Texas Engineering Experiment Station, and the Institute of Manufacturing Systems), and SEMATECH. In addition. Ford Electronics, IBM, and INTEL each sponsored one representative.

Individuals recognized for their research accomplishments in the electronics industry were invited to participate. Representing ongoing programs across the United States and Mexico in industry, government, and academia, the group identified fertile research directions as a guide for the research community and sponsoring agencies. Interacting tracks dealt with semiconductor manufacturing and circuit card (and higher level) assembly. This paper documents the important research themes identified relative to three topic areas: integrating systems, models for design and operation of production/assembly systems, and assurance sciences. It also summarizes a lively discussion which sought ways to improve the effectiveness of university/industry partnering relationships. This paper includes essential recommendations that resulted from the Workshop, but the interested reader can obtain a somewhat more detailed Final Report from Dr. Wilbert E. Wilhelm, the Principal Investigator for the Workshop project.     

AM radio circuit using printed electronic components

In this paper, printing technologies have been employed to print the resonant circuit and detection circuit for an amplitude modulation system (AM radio), which consists of a printed inductor, capacitor, resistor and diode on plastic foils for using as an AM radio circuit. To test the printed inductor, capacitor, resistor and diode as components of AM radio, we selected 640 KHz, the strongest AM frequency in Sunchon City, Korea and monitored the audio signal by replacing each component by a corresponding printed one. As a result the 640 KHz AM radio signals were detected.     

Conductive filament formation in printed circuit boards: effects of reflow conditions and flame retardants

Conductive filament formation, a major cause of failures in printed circuit boards, is an electrochemical process that involves the transport of a metal through or across a nonmetallic medium under the influence of an applied electric field. With an increasing potential to market “green” electronics, environmental and health legislations, and the advent of lead-free and halogen-free initiatives, newer types of printed circuit board materials are being exposed to ever higher temperatures during solder assembly. The higher temperatures can weaken the glass-fiber bonding, thus enhancing conductive filament formation. The effects of the inclusion of halogen-free flame retardants on conductive filament formation in printed circuit boards are not completely understood. Previous studies, along with analysis and examinations conducted on printed circuit boards with failure sites that were due to conductive filament formation, have shown that the conductive path is typically formed along the delaminated fiber glass and epoxy resin interfaces. This paper is a result of a year-long study on the effects of reflow temperatures, halogen-free flame retardants, glass reinforcement weave style, and conductor spacing on times to failure due to conductive filament formation.     

A 13.56 MHz Rectifier Based on Fully Inkjet Printed Organic Diodes

The increasing diffusion of portable and wearable technologies results in a growing interest in electronic devices having features such as flexibility, lightness-in-weight, transparency, and wireless operation. Organic electronics is proposed as a potential candidate to fulfill such needs, in particular targeting pervasive radio-frequency (RF) applications. Still, limitations in terms of device performances at RF, particularly severe when large-area and scalable fabrication techniques are employed, have largely precluded the achievement of such an appealing scenario. In this work, the rectification of an electromagnetic wave at 13.56 MHz with a fully inkjet printed polymer diode is demonstrated. The rectifier, a key enabling component of future pervasive wireless systems, is fabricated through scalable large-area methods on plastic. To provide a proof-of-principle demonstration of its future applicability, its adoption in powering a printed integrated polymer circuit is presented. The possibility of harvesting electrical power from RF waves and delivering it to a cheap flexible substrate through a simple printed circuitry paves the way to a plethora of appealing distributed electronic applications.     

3D Printing technologies for drug delivery: a review

With the FDA approval of the first 3D printed tablet, Spritam®, there is now precedence set for the utilization of 3D printing for the preparation of drug delivery systems. The capabilities for dispensing low volumes with accuracy, precise spatial control and layer-by-layer assembly allow for the preparation of complex compositions and geometries. The high degree of flexibility and control with 3D printing enables the preparation of dosage forms with multiple active pharmaceutical ingredients with complex and tailored release profiles. A unique opportunity for this technology for the preparation of personalized doses to address individual patient needs. This review will highlight the 3D printing technologies being utilized for the fabrication of drug delivery systems, as well as the formulation and processing parameters for consideration. This article will also summarize the range of dosage forms that have been prepared using these technologies, specifically over the last 10 years.     

The role of SPC in printed circuit board manufacture

This paper reports on research which examined the use of statistical process control (SPC) in the quality improvement process of a printed circuit board (PCB) manufacturer. The implementation of SPC is discussed along with the difficulties encountered and benefits achieved. The findings indicate that SPC is a tool which can be of considerable assistance in the quality improvement process of PCB manufacture. However, the variety of manufacturing technologies used and the number of interconnecting processes makes the application of SPC more difficult than in other traditional industries. The lessons learned include that the introduction of SPC must not be rushed, that discipline and support from all levels in the organization are crucial to its success, that SPC cannot be used in isolation—it needs the structure of a continuous improvement initiative, and that getting processes in a state of statistical control and capable, and keeping them there, is a difficult task which involves considerable effort and patience.     

线路板印刷用Cu纳米粒子的研究进展

综述了电路印刷油墨用Cu纳米粒子在合成表征及应用方面的研究现状和发展趋势,并从工艺角度对其工业化生产做出了简要分析;归纳了电路板印刷油墨用Cu纳米粒子抗氧化技术进展;展望了今后印刷电子电路中Cu纳米导电材料的研究方向。     

Performance and characterization of new micromachined high-frequency linear arrays

A new approach for fabricating high frequency (> 20 MHz) linear array transducers, based on laser micromachining, has been developed. A 30 MHz, 64-element, 74-microm pitch, linear array design is presented. The performance of the device is demonstrated by comparing electrical and acoustic measurements with analytical, equivalent circuit, and finite-element analysis (FEA) simulations. All FEA results for array performance have been generated using one global set of material parameters. Each fabricated array has been integrated onto a flex circuit for ease of handling, and the flex has been integrated onto a custom printed circuit board test card for ease of testing. For a fully assembled array, with an acoustic lens, the center frequency was 28.7 MHz with a one-way -3 dB and -6 dB bandwidth of 59% and 83%, respectively, and a -20 dB pulse width of -99 ns. The per-element peak acoustic power, for a +/- 30 V single cycle pulse, measured at the 10 mm focal length of the lens was 590 kPa with a -6 dB directivity span of about 30 degrees. The worst-case total cross talk of the combined array and flex assembly is for nearest neighboring elements and was measured to have an average level -40 dB across the -6 dB bandwidth of the device. Any significant deviation from simulation can be explained through limitations in apparatus calibration and in device packaging.     

Combined effects of linear and angular errors in pc board assembly

Automated printed circuit board assembly is a complex process where accuracy is a critical issue. This paper discusses the quantitative effects of linear and angular errors present in such a system on the successful assembly of through-hole components that have been properly registered. Both additive and statistical error compounding methods are illustrated. Mathematical models developed in this study can be used to determine the relative effects of critical system parameters and tolerances on proper insertion of the component into the pc board. Optimal design and control specifications can therefore be obtained for an efficient and successful assembly system.