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Several effects of the atmosphere in the soldering oven on both the soldering process itself and the soldering results are discussed. Experiments have been undertaken to compare the results of soldering in air and in nitrogen containing 10,100 and 1000 ppm oxygen, in which, e.g., discolouration, wettability, solderability after reflow, solder bridging and solder‐ball formation were investigated. Unmounted FR‐4 testboards with both an RMA solder paste of known high quality and a low‐residue paste were used. Mounted test boards were used to analyse the self‐alignment of components and to compare the levels of soldering defects obtained in air and in nitrogen. The test results show that a nitrogen atmosphere containing 1000 ppm of oxygen or less is sufficiently pure to realise improved soldering conditions for most types of components. For the low‐residue paste tested, 1000 ppm is too high, but 100 ppm is sufficiently low. All effects on the soldering process will depend on the amount of oxygen in the gas. To produce an oven atmosphere of nitrogen with a very low amount of O2 (e.g., <100 ppm) is rather expensive, if this oven is to work under production conditions. Will the extra cost of investment and gas consumption be worthwhile in view of a better production yield and higher product quality? The authors explain why they do not believe this to be the case.

This paper describes the results of experiments to remove short circuits after wave soldering Surface Mounted Devices (SMDs), using an air‐knife debridging system. The air knife can improve the results of wave soldering by removing short circuits which otherwise cannot be removed by adjusting the solder waves; however, the knife must be properly adjusted. Furthermore, it appears that the most serious problem found by using the air knife is the formation of solder balls. The number of these can be reduced if a suitable agent is added to the second wave of the soldering machine, which makes the air knife more or less superfluous.

Although wave soldering is a long established technique, the touch‐up percentage is still unacceptably high. This leads to high touch‐up costs and too low product quality. One cause lies in the fact that the complexity of the boards is increasing all the time (greater component density, greater diversity, more leads and smaller pitches). The main reason, however, lies in the lack of a fundamental process technology background. This becomes even more serious now that soldering processes are becoming more critical. The touch‐up percentage can and must be lowered through accurate process adjustment and control. A further improvement in process adjustment and control will give a considerable improvement in soldering quality in the short term. In this way, the actions are successful, although benefits can be achieved only if the improvements are consolidated. Further improvements can be achieved through systematic application of design rules.

This paper presents the requirements for infra‐red soldering machines for reflow soldering of printed boards with components for surface mounting. Guidelines for controlling and adjusting the infra‐red reflow soldering process, as well as a computer model to help the user of infra‐red reflow systems to adjust an infra‐red oven, are provided. In specifying the various process conditions, the authors have considered that a careful adjustment of the process parameters will improve the soldering quality.

A method for assessing the solderability of thick‐film substrates is described. An appropriate quantity of solder, with a soldering flux, is applied to the land to be tested and is melted under precisely defined conditions. After solidification of the solder, the diameter of the base of the droplet is measured. The value of the wetting angle, which is a measure of the solderability, can be read from a calibration graph. An analysis of variance has been performed to evaluate the reproducibility of the test method used.

Removal and replacement instructions for surface mounted components are given, as well as certain precautionary measures and examples. Some of the figures have already been published in service manuals. A distinction is made between methods for replacing one or a few components, several components and many components. It is indicated which method can be applied, which equipment is available and what must be considered.

Drawbridging or Stonehenge Effect of leadless components (i.e., the standing up on their end faces) has been investigated. An explanation is offered based on a straightforward theoretical model considering surface tension, sustained by a great amount of experimental evidence. The phenomenon is strongly associated with condensation reflow soldering, whereas the dimensions of the metallisation at the underside of the leadless components and the size of the solder lands on the board are major influencing factors. Practical hints are given to overcome the problem.

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.

As a result of the trend towards portable communication products, low‐cost miniaturisation is becoming increasingly important. One of the methods to achieve low‐cost miniaturisation is flip‐chip assembly on FR4 boards. In this paper, two types of flip‐chip assembly process will be discussed: a process where flip‐chips with eutectic solder‐bumps are assembled by using a tacky flux, and a process where flip‐chips are assembled by using solder paste. Both processes have been verified on production boards, using production equipment. Demonstrated ppm defect levels are between 35 and 400 ppm (confidence level 95 per cent) at the solder joint level. Component yields for flip‐chips are between 99.2 and 100 per cent. The reliability of the assemblies fulfils consumer communication equipment requirements.

It was observed that “no solder” or “skipped solder” defects occurred on a particular printed circuit board assembly product during wave soldering. Investigations were carried out to find out the cause of this defect and to recommend an optimal hot air level coating thickness. To evaluate whether thicker plating helps to produce better solderability, new printed circuit boards with an average plating thickness of 4.27 μm were sent for solderability testing. This increase in plating thickness resulted in no defects in the solderability test. This is in contrast to the current printed circuit board that had a no/skipped solder defect rate of 1,433 ppm due to the thinner plating thickness which was in the region of 2.26 μm. In summary, the investigations made have revealed imperfections in the pad plating, and it is recommended that a thicker or more even plating is achieved during the hot air levelling process at the printed circuit board manufacturing site so as to eliminate no/skipped solder defects that are induced by this printed circuit board deficiency.