There are various soldering methods, such as hand soldering, wave soldering, reflow soldering (e.g., vapor phase, convection reflow), and selective soldering. Some of these processes have been around for many years, while others were introduced more recently. All of these processes have unique characteristics, advantages, disadvantages, and applications. For example, no process can compete with the cost-effectiveness of wave soldering for through-hole board assemblies. Similarly, if the board contains only surface-mount components, the predominant soldering process choice is convection reflow.
If you have to deal with mixed-assembly boards with both surface-mount and through-hole components—as is the case today for more than 95% of electronic products—the selection of a soldering process becomes more complex, especially if you use both tin-lead and lead-free components on the same board.
Vapor phase soldering (VPS), also known as condensation soldering, has gone through changes in popularity. Once the process of choice in the early 1980s, its use has declined considerably for two reasons: problems with the VPS process itself and improvements in the convection reflow process. The problems with VPS are mostly in the areas of higher defects, such as wicking mostly in J-leaded parts and tombstoning in chip components.
To read this entire column, which appeared in the October 2019 issue of SMT007 Magazine, click here.