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To make wave soldering of SMDs a success, one must realise that not only the process involved is important, but also the board design and SMD mounting aspects play an important role as they may differ considerably from the rules established for reflow soldering. To elucidate this difference is the main issue of this article.

This paper describes some fundamental aspects involved in wave soldering of surface mount devices. Calculations are given on capillary behaviour to provide a greater understanding of the problems involved in wetting SMDs. The soldering of SMDs with a new single wave soldering concept will also be featured.

The effects of oxygen on solder surface tension, wetting time and surface damping are presented. Oxygen levels greater than 10 ppm lower surface tension, increase wetting time and increase surface damping. Decreased surface tension leads to higher misalignment defects in reflow soldering, but can lower the incidence of dewetting. Increased wetting times can increase non‐wetting defects in both wave and reflow soldering, especially when using no‐clean fluxes. Increased surface damping can lead to lower bridging rates in wave soldering, provided that the oxygen level and flux levels are properly balanced. Choosing the optimum oxygen level for production soldering is trade ‐ off between the stability and the versatility of the process. The most stable soldering processes will be those performed in an inert atmosphere with less than 10 ppm oxygen .These processes are insensitive to variations in soldering machine operating parameters (i,e. a larger process window).This is most desirable for manufacturers soldering large volumes of a given circuit board. The soldering process can be optimised by optimising the circuit board design. The most versatile soldering processes will be those performed in an inert atmosphere with controlled addition of oxygen in the range of 100 ppm to 10,000 ppm (1%). This will be most desirable to manufacturers soldering short runs of a large variety of circuit boards. The soldering process is best optimised by controlling the soldering machine operating parameters (oxygen, flux, preheat, conveyor speed, etc.).

The purpose of this paper is to present a three-dimensional finite volume-based analysis on the effects of propeller blades on fountain flow in a wave soldering process and performs an experimental validation.

Solder pot models with various numbers of propeller blades were developed and meshed by using hybrid elements and simulated by using the FLUENT fluid flow solver. The characteristics of the fountain, such as flow profile, velocity vector, filling time, and fountain advancement, were investigated. Molten solder (Sn63Pb37) material, a temperature of 250°C, and a propeller speed of 830 rpm were applied in the simulation. The predicted results were validated by the experimental fountain profile.

The use of a six-blade propeller in a solder pot increased the fountain thickness profile and reduced the filling time. Moreover, a six-blade propeller design resulted in a stable fountain profile and was considered the best choice for current wave soldering processes.

This study provides a better understanding of the effects of propeller blades on the fountain flow in the wave soldering process.

The study explores the fountain flow behavior and provides a reference to the engineers and designers in order to improve the fountain flow of the wave soldering.

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.

The screen printing and reflowing of solder paste is compared with wave soldering for the attachment of surface mounted devices to PCBs. Both techniques have advantages and disadvantages which are fully discussed. The method chosen for a particular application will depend upon the production facilities available, the principal package types involved in the design, and the anticipated cost. The main advantages of the screen printing process have been found to be a relatively low soldering temperature, freedom from device orientation and package design constraints, and few proximity effects, while those for the wave soldering process have been found to be compatibility with present mass soldering operations, the ability to combine both through‐hole devices and SMDs on the same board, a single soldering operation, and a solder joint volume defined by the joint design. It is concluded that in the long term screen printing and reflow is likely to become the dominant technology, but in the intermediate term wave soldering is likely to remain attractive while manufacturers move from the established through‐hole technology to the more space‐efficient surface mounted technology.

This issue of the journal features the final part of a two‐part series which comprises Chapter 15 from Volume 1 of a recently published book ‘A Comprehensive Guide to the Manufacture of Printed Board Assemblies’^* edited by W.MacLeod Ross.Volume 1, containing 800 pages, and Volume 2, scheduled to be published in the Spring of 1997 and estimated to contain around 900 pages, will, as far as the publishers are aware, be the most comprehensive book ever published on the subject of printed board assemblies.

Though lead‐free replacements for SnPb eutectic alloys for reflow, wave, and hand soldering have been developed, relatively little has been reported on practical experience of lead‐free wave soldering processes. In wave soldering, the interaction between the PCB, flux, solder alloy and processing equipment makes it desirable to develop the consumables and the wave soldering machine concurrently. A crossfunctional project team was formed and a lead‐free wave soldering process developed and validated through nine months of industrial use in production of broad‐band communications technology products.

For over 30 years, wave soldering has been the most popular and most economical method for mass soldering of electronic assemblies. For conventional circuits, this is a mature technology. Training, proper board design, process control during board fabrication, assembly and soldering and, finally, an awareness of the need for solderability have resulted in very high manufacturing yields in some companies with the associated high quality and much improved profits which result by doing it right the first time. With the introduction of surface mount technology, the same concerns need to be addressed. However, due to the smaller size of components and higher densities, new problems arise. This paper presents some of the concerns encountered in wave soldering of surface mount assemblies.

This paper deals with the thermal, chemical and metallurgical interactions between the printed circuit board and the solder wave. Special attention is devoted to the quality of the final solder fillet as a function of each variable. The individual zones inside of a solder wave is analysed. Their effect on the printed circuit and their components is explained. Guidelines for production parameters, i.e., solder temperature, conveyor speed, depths of immersion, impedance angle, hole‐to‐wire ratio, etc., are outlined. The wave solder operation cannot be isolated from fluxing and preheating; therefore, these two additional operations are also analysed. This will be limited, however, to those aspects directly related with wave dynamics. The paper concludes with a discussion of voids and entrapment in the solder fillet as they relate to the wave soldering process. A case history is used to outline the effect of voids on quality. Suggestions are made to avoid fillet imperfections such as blow holes, voids and incomplete fillets. Proper touch‐up procedures is also covered.