Wave soldering is a method that large printed circuit boards can be soldered quickly and reliably during PCB assembly.
The wave soldering process gets its name from the fact that the process enters the printed circuit board through the wave solder to be soldered.
In this way, a complete plate can be welded within seconds when the production joints are reliable, mechanically and electrically. Besides being much faster than manual welding, wave welding also produces a higher degree of reliability of joints.
Wave soldering can be used in PCB assembly at the same time for through-hole mounting components and surface mounting components. However, other methods, such as infrared reflow soldering, are more suitable for surface mount components of printed circuit boards with fine features used today.
Wave soldering machine consists of a heating tank of solder. This is maintained at the required temperature for the welding process. The inner groove, the solder wave is established and the printed circuit board passes through, so that the bottom surface of the board just touches the solder wave. Attention must be paid to adjusting the height of the wave, so that it will not flow to the top side of the circuit board, which will cause the solder to enter the place where it is not needed.
The plate is fix in place on a conveyor belt using metal finger. These are usually made of titanium, because it can withstand the temperature and it is free from solder.
In order to make an electronic printed circuit board successfully processed by wave soldering machine, it is necessary to design and manufacture it in a correct way.
Solder layer: It is a standard practice to design boards these days. Solder resist or solder mask layer is included in the design of printed circuit board, which increases the "paint" of layered materials to the solder which will not adhere to the board. Only the areas to be welded are exposed. This solder resist is green, which is commonly used for color.
Pad spacing: The second major precaution is to ensure that there is a need for sufficient spacing between bonding pads. If they are too close to each other, there is a possibility that the solder can cross the two pads and cause a short circuit. In view of the way of wave soldering works, in which the soldering wave is caused by the solder flowing out of the storage tank, and when the board passes through it, the spacing requirement depends on the direction of the relative solder flow board. Spacers in the direction of solder flow should have a larger spacing than those with right-angle solder flow. This is because it is easy for solder bridges to occur in the direction of solder flow.
In order to ensure that the area to be welded is clean and free of charge, etc., flux is required. Flux should be applied to one side of the circuit board, that is, the bottom. Careful control of the amount of magnetic flux required. Too little flux and high risk of poor joints, while excessive flux will have residual flux on the circuit board. Although it doesn't look cosmetically bad, there is a risk of long-term degradation due to the acidic nature of magnetic flux. There are two main ways to apply flux:
Spray flux; The fine mist of flux is sprayed onto the board of ontoth, that is, the bottom surface of welding electrons. Some systems can even use compressed air jets to remove excess flux.
Foam flux; The electronic printed circuit board crosses the cascade head of magnetic flux foam. This is produced by immersing a small hole in a plastic cylinder in which a magnetic flux tank is used. The cylinder is covered with a metal chimney and air is forced through the cylinder. This will lead to a chimney with rising flow bubbles.
The wave soldering process exposes the electronic printed circuit board to a considerable degree of heat, which is far greater than what it would have suffered if it had been manually soldered. If it is not addressed, this thermal shock will cause a significantly increased level of failure. In order to overcome this problem, the board is preheated so that it can minimize any thermal shock and steadily rise to the required temperature.
Preheating area is usually done by blowing hot air onto the circuit board, because they pass through the hot air heater of the wave soldering machine. In some cases, the population, especially if the board is dense, the infrared heater can be used. This will ensure that all circuit boards are heated evenly and there are no shadow areas.
Although pre-heating is required to prevent thermal shock, the wave soldering machine will be generated, and the heating still needs the flux of activation. This flux must ensure that the welded area is clean and will take solder.
Application of wave soldering
Wave soldering is not widely used in PCB assembly because it is at the same time. It is not suitable for the very fine pitch required in today's manufacturing of many circuit boards. However, it is ideal to mount many boards with traditional lead-containing components and some surfaces to use larger component boards.