What is wave soldering?

2022-09-09

Wave soldering is a method by which large printed circuit boards can be soldered quickly and reliably during PCB assembly.Wave Soldering
The wave soldering process gets its name from the fact that the process enters the printed circuit board through the wave of solder to be soldered.
In this way a complete board can be welded in seconds while producing joints that are reliable, mechanically and electrically. In addition to being much faster than hand soldering, wave soldering also produces a higher degree of reliability of the joint.
Wave soldering can be used in PCB assemblies for both conventional through-hole mount components as well as surface mount components. However, other methods such as infrared Reflow Soldering are more suitable for surface mount assemblies with fine features on printed circuit boards used today.
wave soldering
A Wave Soldering Machine consists of a heated pot of solder. This is maintained at the temperature required for the soldering process. Inside the groove, the solder wave builds up and the PCB crosses so that the underside of the board just touches the solder wave. Note that this must be taken into account when adjusting the height of the wave so that it does not flow on the top side of the board where it would cause solder to enter where it is not needed.

The board is held in place using a metal finger conveyor belt. These are usually made of titanium because it is able to withstand the temperature and it is not immune to solder.

Wave Soldering

wave soldering
Prepare
In order for an electronic printed circuit board to be successfully machined using wave soldering, it is necessary to design and manufacture it in the correct way.
Soldermask: The first is standard practice these days when designing boards. A solder mask or solder mask layer is included in the PCB design, which adds a layer of "lacquer" material to the board where the solder will not adhere. Only the areas that need to be soldered are exposed. This solder resist is the most commonly used color for green.
Pad Spacing: The second major precaution is to ensure that there is adequate spacing between solder pads required. If they are too close then there is the possibility that the solder can create a short across the two pads. Given the way wave soldering works, where the solder wave is caused by the solder flowing out of the storage tank, and the board passes over it, the spacing requirements depend on the direction of the board relative to the solder flow. To space the pads in the direction of solder flow, they should have a larger pitch than those spaced at right angles to the solder flow. This is because, it is very easy for solder bridges to occur in the direction of solder flow.
Flux
Flux is required to ensure that the area to be soldered is clean oxidation free, etc. Flux is applied to solder on one side of the board, which is the bottom. Careful control of the amount of magnetic flux required. Too little flux and high risk of poor joints, while too much flux will have flux residue on the board. While this does not look cosmetically bad, there is a risk of long-term degradation due to the acidic nature of the magnetic flux. There are two main methods of applying flux::
Spray Flux; A fine mist of flux to spray ontoth the board that is soldered to the underside of the electronics. Some systems even use a jet of compressed air to remove excess flux.
Foam Flux; the electronic printed circuit board goes over a cascade head of flux foam. This is produced by dipping the canister into a small hole in a plastic cylinder using magnetic flux. The plastic cylinder is covered with a metal chimney and air is forced through the cylinder. This causes flow bubbles to rise up the chimney.
warm up
The wave soldering process exposes an electronic printed circuit board to a considerable degree of heat, far greater than it would suffer if it were hand soldered. This thermal shock can cause a significantly increased level of failure if it is not addressed. To overcome this plate is preheated so that it can stably rise to the desired temperature to minimize any thermal shock.
The preheat area is usually used to blow hot air onto the board as they pass through the hot air heater on the wave soldering machine. In some cases, especially if the population is dense, infrared heaters can be used. This will ensure that all boards are heated evenly and no shaded areas exist.
While preheating is required to prevent thermal shock the wave soldering machine will generate, heating is also required to activate the flux. This flux must ensure that the area being soldered is clean and will take the solder.
Application in wave soldering
Wave soldering is not as widely used for PCB assembly as it is at the same time. It is not suitable for the very fine pitch required in the manufacture of many circuit boards today. However, it is still ideal to use larger component boards with traditional leaded components and some surface fabrication for many board mounts.

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