Wave soldering is an automated process where components are soldered onto a PCB as it passes over a wave of molten solder. The process includes fluxing, preheating, and soldering stages. Wave soldering can produce thousands of solder joints in minutes, but poor process control can lead to faulty hardware. Proper maintenance of variables such as wave profile geometry, preheat and solder temperatures, and a clean manufacturing environment are necessary for high-quality PCBs.
Wave soldering is an automated process where components are soldered onto a printed circuit board (PWB) as the board passes over a wave of solder. Air pumped from the bottom of a container of molten solder creates this wave. Baffles fitted inside the pot also help form the wave profile required for the board to be welded.
A PCB that is assembled with a wave soldering process undergoes three basic stages. In the first stage, the underside of the panel is coated evenly with a material known as a flux. This is typically applied as a spray or foam. The flux prevents the production of oxidation at high temperatures and prevents the correct application of the solder to the parts to be welded.
Preheating follows fluxing to dry and activate the flux in preparation for soldering. It also reduces the thermal shock that the board and components experience when they pass over the hot wave of molten solder. The dissipation of volatile materials in the flux at this stage reduces the likelihood of spattering when soldering the board. This reduces the number of opportunities for weld defects to be created in the final product.
Once preheated, the PCB passes over a conveyor on the wave so that solder is applied to leads, terminations and other areas on the bottom of the board. No solder flows across the top of the board. Areas on the board that don’t need to be soldered are usually coated in advance with a solder mask to prevent solder from sticking to them.
Many manufacturing facilities use wave soldering because the process can create several thousand solder joints in minutes. This helps the plant achieve a much higher production rate than would otherwise be possible. The wave soldering process, however, poses some challenges in a manufacturing environment. Since the production rate of boards is high, there is also great potential for a large amount of faulty hardware to be rapidly produced due to poor process control.
The solder connections formed by the wave soldering process not only connect components to the board, they also form electrical connections between them. This is what allows the final product to function electronically. Welding defects are not just an aesthetic problem. They can also cause the card to malfunction or even damage it beyond repair.
To produce consistently high quality printed circuit boards, many variables must be carefully designed and tightly controlled. The geometry of the wave profile must be properly maintained to avoid the application of excess or insufficient solder. Controlling the preheat and solder temperatures is necessary to ensure that no damage is done to the PCB or the components on it. Maintaining a clean manufacturing environment helps ensure solder and flux purity, thereby reducing the risk of faulty hardware.
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