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To enhance the detection efficiency of printed circuit board (PCB) soldered dot, this study aims to detect PCB soldered dot with image processing method.

Through a series of image processing algorithms, threshold segmentation and feature extraction of the solder joint images were completed; then, sphericity was confirmed based on the area and perimeter, as well as the shape parameter and eccentricity ratio of the calculated region, paving the way for defect pattern recognition.

It proves that the method with high efficiency and precision can satisfy the requirements of PCB soldered dot detection.

This paper is original in presenting a method for PCB welding spot detection.

In Part 1, background information on mechanical properties and metallurgy of solder alloys and soldered joints has been presented. In Part 2, mechanisms of damage and degradation of components and soldered joints during soldering, transport and field life have been discussed, the most important mechanism being low cycle fatigue of the solder metal. In this third part, the determination of the fatigue life expectancy of soldered joints is discussed. Accelerated testing of fatigue is needed, as the possibilities of calculations are strongly limited. A temperature cycle test under specified conditions is proposed as a standard. A model is worked out for the determination of the acceleration factor of this test. A compilation of a number of solder fatigue test results, generated in the author's company, is presented.

Strength measurements of soldered joints in electronics are widely used for the assessment of joint quality. However, a variety of experiments, reported in this article, clearly show that a strong relationship between initial strength and joint quality does not exist. Far more important for joint reliability is the resistance of soldered constructions to low‐cycle fatigue of the solder metal, caused by thermal expansion differences upon temperature cycling during use. A temperature cycling test is proposed as a standard accelerated ageing method for the prediction of the low‐cycle fatigue life of soldered joints in electronics.

A study was conducted to examine the sensitivity of solder joint integrity for PBGA assembly and post rework process yields to the change of the solder ball coplanarity specification from 0.15mm to 0.20mm as well as to increase the level of confidence with respect to the specification change. The study considered the following experimental variables: solder ball coplanarity; stencil thickness and aperture design; whether the assembly also experiences a wave soldering process; the rework method, i.e. whether there is dispensing of solder paste or just a flux. Electrical continuity tests were performed after PBGA assembly and rework. Accelerated thermal cycling and thermal shock tests were then used to evaluate the solder joint reliability. Additionally, standoff heights of PBGA solder joints were measured through cross sectioning samples. Statistical comparisons of the mean standoff height between different PBGA coplanarity groups, where different experiment variables were applied, allowed for determination of the variation of BGA solder joint integrity.

The mechanical design of the automatic placement machine and the integrated application of different tools dictate the result of the placement process. The placement accuracy of the system is a decisive factor for the quality and cost of the printed circuit board. Vision systems have become indispensable in today's SMD placement technology.

Intensive, informative, interesting and also highly enjoyable—such were the adjectives that immediately sprang to mind during the short homeward flight from Eindhoven's modern international airport after the busy and varied two‐day SMD Technology Workshop. Time during the brief visit did not permit any exploration of the area, but journeys between airport, De Brug Congress Centre at Mierlo, and Philips SMD Centre provided a few impressions of the enviably clean and pollution‐free, and generously spacious centre and suburbs of this modern city in Southern Holland. Encompassing an agglomeration of what were originally small villages, Eindhoven currently has a population of 200,000. The presence of Philips is inescapable, as, apart from the sheer size of its production and research facilities employing some 35,000 people, many other buildings in the city have been constructed by the company. In 1891, when Anton and Gerard Philips established the Gloeilampenfabriek (the original building now housing a museum of lighting), the town had virtually no infrastructure. Schools and shops were built at Philips' instigation over the ensuing years, followed more recently by the huge Philips Stadium, a theatre and entertainment centre, and now the airport. The company at present engages 75,000 personnel in The Netherlands, and employees worldwide total 350,000, with a turnover of more than 60 billion guilders in 1985.

The effects of Pb contamination on the microstructure and shear strength of lead‐free solder joints with non‐lead containing finishes on both the PCB and terminals of 1,206 chip capacitors at different temperatures were investigated. Two kinds of lead‐free solders (Sn96.5Ag3.5 and Sn95Sb5) were selected, and different amounts of eutectic Sn‐Pb were added to these lead‐free solders according to the potential Pb contamination in a 1,206 chip capacitor solder joint. It was found that there was no difference in shear strength of solder joint at room temperature for those with or without Pb contamination, but the shear strength at 1258C for the solder joint without Pb contamination was about 15 percent higher than for those with Pb contamination.