I know wave soldering is primarily used for through-hole components, but I’ve also read that certain SMD components can be wave soldered on mixed-technology boards.
What I’m trying to understand is what actually comes into contact with the solder wave. Does the molten solder only wet the exposed terminations, or can it also contact part of the component body during the process?
If the component body is exposed to the solder wave, why doesn’t this damage the component? Is it simply because the contact time is very short, or are wave-solderable SMD packages designed to tolerate it?
The solder wave primarily wets the exposed pads and component terminations, but depending on the package geometry and process settings, it may also contact the underside or lower portion of the component body. That alone doesn’t normally damage the component because wave-solderable packages are designed to withstand the thermal profile, and the contact time with the molten solder is very short.
Compared with reflow, wave soldering subjects components to a much faster thermal excursion, so package suitability and process control become more important. Moisture-sensitive devices also need to be handled according to their MSL requirements, and baking may be necessary if the recommended floor life has been exceeded.
Component orientation also matters. Packages aligned perpendicular to the solder wave are more susceptible to shadowing and soldering defects, so pad geometry and placement are often optimized for the wave direction. It’s worth checking with your PCB assembler, as they may have specific design rules or recommendations for components intended for wave soldering.
One aspect that’s easy to overlook is component selection. Not every SMD package is considered wave-solder compatible, even if it can physically survive the temperature. Many manufacturers specify in the datasheet whether a package is rated for wave soldering, reflow only, or both, and that rating often comes with restrictions on which side of the board the component can be mounted on. It’s worth checking the component’s recommended soldering profile before assuming it can go through a wave process.