Automatic inspection system for printed circuit boards

The purpose of this correspondence is to present problems and methods in automating visual inspection of printed circuit boards (PCB's). Vertical and diagonal illumination are useful in detecting PCB patterns correctly. An algorithm comparing local features of the patterns to be inspected with those of the pattern to be referenced is proposed. An inspection system using developed technologies is also described.     

Optimal component-insertion sequenceplanning methodology for the semiautomatic assembly of printed circuit boards

One of the primary concerns in the manufacturing of printed circuit boards (PCBs) is the definition of optimum component-insertion sequences for manual and automated operations. The problem is dynamic and multiple feasible solutions can be found. The research work described in this paper has developed a component-insertion sequencing methodology and a proof-of-concept expert system for printed circuit boards. This system solves the component-insertion sequencing problem for semi-automated work cells which utilize a light guiding system to identify for the operator where to assemble the next component. The innovation of the methodology is the application of Artificial Intelligence and Expert Systems techniques to represent the human reasoning involved in semi-automated PCB assembly planning. Based on established assembly criteria, sequencing decision rules and data available from a CAD system, the methodology leads to optimum component-insertion sequences.     

Prerouting analysis of printed circuit boards

Several methods used for the prerouting analysis of printed circuit boards are compared. The quality of a method is expressed as the correlation between predicted and actual values of objective measures of an interconnection problem complexity. The experimental data confirm that some indicators of a board complexity which are often used in practice, such as component density, are highly unreliable. The PAP program is based on the modelling of the actual routing process. It has been experimentally proved that the PAP program provides reliable results which can be used for the detailed analysis of an interconnection problem.     

Experiments with routing on printed circuit boards

Several ways of utilizing Lee's wave algorithm for routing on printed circuit boards were compared. It was proved that the order of net processing influenced the quality of the solution of a given interconnection problem. Moreover, it was found that the choice of ‘source’ and ‘target’ formations influenced both the computational time and the quality of the solution. The results obtained allowed the performance of the SYSDEB77 system for routing on two-layer boards to be improved.     

Artwork production for multi-layer printed circuit boards by computer

This paper describes a computer system which integrates three types of numerical control machines in the production of artwork drawings and drill tapes for multi-layer printed circuit boards.     

Modeling double‐side printed meander‐line inductors on printed circuit boards

A lumped element model for a double‐side printed meander‐line inductor with closed‐ form expressions for the electrical model parameters L, C, R_l, and R_c is presented. These structures are cheaper than coils and need less area per unit of inductance than single‐side printed meander‐line inductors. The model has been validated with measurements from 30 to 1000 MHz, finding a mean error in the inductance parameter of about 1%. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 105–112, 2003.     

Inspection of printed circuit boards by connectivity preservingshrinking

Two algorithms for visual inspection of printed-circuit boards are presented that perform width checking of conductors and insulators. The first detects the difference between the results of shrinking and connectivity-preserving shrinking (CPS). The second algorithm produces a difference between the original and the shrunk picture. This result is subject to a number of CPS-operations after which errors are easily detected. Both algorithms can be adapted to a suitable level of sensitivity to sharp corners and edge irregularities. A sequential version of CPS is also described which is well suited for hardware implementation in a pipelined structure     

Modeling and characterization of an industrial inkjet head for micro-patterning on printed circuit boards

A conceptual design using computational fluid dynamics (CFD) and micro-electro-mechanical systems (MEMS) fabrication has been performed to develop an industrial inkjet head for micro-patterning on printed circuit boards. The printhead has been fabricated with silicon and silicon on insulator (SOI) wafers by MEMS process and silicon to silicon bonding method. The measured displacement waveform from a piezoelectric actuator by laser doppler vibrometer (LDV) was used as input data for the three-dimensional flow solver to simulate the droplet formation. The mechanism of droplet ejection from piezoelectric-type inkjet heads was investigated by simulating two-phase flows of the air and metal inks. As a preliminary approach, liquid metal jetting phenomena are identified by simulating droplet ejection and droplet formation in a consequent manner. Parametric studies are followed by the design optimization process to deduce key factors to inkjet head performance: nozzle geometry, droplet size, ejecting speed, pulse amplitude, and ink viscosity. The present design tool, based on a two-phase flow solver and experimental measurements, has shown its promising applicability to various concept designs of industrial inkjet system for micro-patterning on electronic chips and boards.     

An evolutionary design methodology of printed circuit boards for high-speed VLSIs

As operation frequencies of the printed circuit boards (PCBs) increase in keeping with VLSI frequencies in the GHz domain, two independent serious problems occur in the PCB design. One is waveform distortion problem, or signal integrity (SI) degradation problem, in PCB traces. And the other is power-supply drop problem, or power integrity (PI) degradation problem, in PCB power planes. Those problems are barely able to be overcome on case-by-case empirical designs conventionally. In this paper we newly propose a design approach for each problem, both of which are based on the genetic algorithm. And we obtained improvement ratios of more than double compared with the both conventional designs for SI and PI degradations, respectively.     

Design of meander line inductors on printed circuit boards

A partial‐element circuit model for meander line inductors printed on circuit boards is proposed and its relation with the physical layout is derived. A procedure for the design is presented allowing to obtain inductances between 8 and 50 nH in the range from 30 to 1000 MHz with a 5% mean error. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 219–230, 2001.     

考虑切换时间的多品种印刷电路板表面贴装生产线调度优化

考虑了多品种小批量生产环境下的印刷电路板生产调度优化问题,建立了以包括切换时间在内的多品种平均流程时间最小化为目标的调度优化模型.针对电了产品组装独特的切换后效性,开发了主动禁忌搜索算法,分组间搜索和组内搜索2个层次对印刷电路板的排序问题进行优化.通过与理论下界值比较的仿真实验显示了模型与算法的有效性及现实应用的可行性...     

A generalised fuzzy reasoning algorithm for an object-oriented expert system tool

Abstract: A fuzzy reasoning algorithm is presented in this paper. It is based on the concept of a generalised fuzzy production rule that adds new conjunctions such as ADD and REL to the usual AND and OR conjunctions for the linkage of premises in conventional rules. A definition is given for weights and related factors, to express and measure a relation between the premises. A formal representation for fuzzy premises is presented, together with the introduction of a fuzzy match method. Multiple thresholds are used to convert the uncertainty measures of reasoning results into linguistic variables. We have applied the fuzzy reasoning algorithm to a frame-based hybrid expert system tool. An object-oriented approach is used in implementing the system. Some results of the application are presented and discussed.     

A solution technique for placing digital integrated circuitry on printed circuit boards

A mathematical formulation of the problem is presented using the concepts and terminology of graph theory. This formulation includes both stages of the placement problem wherein the vertices of the circuit graph are partitioned into several subsets (representing integrated circuit packages) which are, in turn, assigned to geometric positions corresponding to the printed circuit board specifications. Utilizing the manhattan metric, a heuristic procedure is described which provides minimum length placements on two-sided printed circuit boards consistent with the requirements of PC board designers. Computational results from problems arising in actual design efforts are discussed.     

A comparison of setup strategies for printed circuit board assembly

This paper develops and tests a set of strategies for operating a single printed-circuit-board assembly machine. In particular, the paper addresses decisions associated with feeder changeover, placement sequencing, and board sequencing. Solution procedures are developed and implemented for a variety of setup management strategies, including group and partial setup. These procedures are tested on a range of problems to determine their relative performance under different production environments. The procedure for group setup is shown to be applicable when component commonality is high and changeovers are time consuming. Partial setup strategies, which focus on minimizing the total production time, are shown to adapt to changing production conditions and therefore outperform the other setup strategies.     

Knowledge-based linguistic equations for defect detection through functional testing of printed circuit boards

Increasing globalization of the economy is imposing tough challenges to manufacturing companies. The ability to produce highly customized products, in order to satisfy market niches, requires the introduction of new features in automation systems. Flexible manufacturing processes must be able to handle unforeseen events, but their complexity makes the supervision and maintenance task difficult to perform by human operators.This paper describes how linguistic equations (LE), an intelligent method derived from Fuzzy Algorithms, has been used in a decision-helping tool for electronic manufacturing. In our case the company involved in the project is mainly producing control cards for the automotive industry. In their business, nearly 70% of the cost of a product is material cost. Detecting defects and repairing the printed circuit boards is therefore a necessity. With an ever increasing complexity of the products, defects are very likely to occur, no matter how much attention is put into their prevention. Therefore, the system described in this paper comes into use only during the final testing of the product and is purely oriented towards the detection and localization of defects. Final control is based on functional testing. Using linguistic equations and expert knowledge, the system is able to analyze that data and successfully detect and trace a defect in a small area of the printed circuit board. If sufficient amount of data is provided, self-tuning and self-learning methods can be used. Diagnosis effectiveness can therefore be improved from detection of a functional area towards component level analysis.     

Heuristic approaches for batching jobs in printed circuit board assembly

The goal of the printed circuit board job-batching problem is to minimize the total manufacturing time required to process a set of printed circuit board jobs on an insertion machine. We have developed four families of heuristics to solve this problem: the clustering family, the bin-packing family, a family of sequencing genetic algorithms, and a grouping genetic algorithm. Within each family of heuristics, we developed several variations. Some of the variations use techniques from the literature and some of the techniques we developed specifically for this problem. We test the variations and select a good performer from each family.     

A particle swarm optimization approach for components placement inspection on printed circuit boards

The importance of the inspection has been magnified by the requirements of the modern manufacturing environment. In electronics mass-production manufacturing facilities, especially in the printed circuit board (PCB) industry, 100% quality assurance of all work-in-process and finished goods is required in order to reduce the scrap costs and re-work rate. One of the challenges for PCB inspection is in the use of a surface mount device (SMD) placement check. Missing, misaligned or wrongly rotated components are the critical causes of defects. To prevent the PCB from having these defects, inspection must be done before the solder reflow process commences, otherwise, everything will be too late. The research reported in this paper concentrates on automatic object searching techniques, in a grey-scale captured image, for locating multiple components on a PCB. The presented approach includes the normalized cross correlation (NCC) based multi-template matching (MTM) method. The searching process has been carried out by using the proposed accelerated species based particle swarm optimization (ASPSO) method and the genetic algorithm (GA) approach as a reference. The experimental results of the ASPSO-based MTM approaches are reported.