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Wave soldering problems and solutions

In most of the products do not need to miniaturization are still in use perforated (TH), or mixed technology circuit boards, such as televisions, home audio-visual equipment, as well as the upcoming digital set-top boxes, are still in use perforated components, so need to use peak welding. From the process point of view, wave soldering machines can only provide small amounts to adjust the most basic of equipment operating parameters.

Production process

Circuit board through the wave soldering machine conveyor into the future, you pass a certain form of flux coating device, where the use of peak flux, foam or spray method of coating to the circuit board. Since most of the flux in the welding must be to achieve and maintain an activation temperature to ensure complete infiltration of solder joints, so circuit board, before entering the wave trough through a preheat zone.

Flux coating can gradually improve after the PCB preheat temperatures make flux activation, this process can also reduce the assembly into the thermal shock wave generated. It can also be used to evaporate all the possible absorption of moisture or diluted flux carrier solvent, if these things are not removed, they would boil in the off peak hours and cause solder sputtering, or to generate steam to remain in the formation of solder inside the hollow joints or trachoma.

Preheating section length of the wave machine and the conveyor speed by the production decisions, the higher the yield, for the board to achieve the required temperature of the infiltration area will require a longer warm. In addition, since pairs of panels and plywood of the heat capacity greater than the single-sided so they need a higher preheat temperature.

Wave soldering machine is basically the current approach to preheat thermal radiation, the most commonly used methods of wave forced hot air convection preheating, electric heating plate convection, electric heating and infrared heating rods. In these methods, the forced hot air circulation is often considered to be right where the majority of wave soldering machines process the most effective method of heat transfer.

In the warm, the circuit board with single-wave ( wave) or double-wave (spoiler wave and wave) welding methods. Pairs of perforated-element in terms of a single wave is sufficient, and circuit board into the wave, the solder flow direction and the board of the road in the opposite direction can be generated around the eddy current component pin. It's like a wash, will all the above flux residues and removal of oxide film, in the solder joint formed when the temperature reaches infiltration infiltration.

For the mixed technology assembly, generally at wave-front also features a spoiler wave. This Bobby narrow, disturbance carries with it a higher vertical pressure, can penetrate into the solder well placed tight pin and surface mount components (SMD) between the pads, and then complete the solder wave forming .

In the future, equipment and suppliers, prior to any assessment of the need to identify with the wave crest welding of the board of all the technical specifications, as these can determine the required machine performance.

To avoid the defects

With the current PCB components become smaller and more dense, in the solder bridge between the company and the possibility of short-circuit and therefore increased. There are already some time-tested methods to resolve this problem, and one way is to use air knife technology. This is the peak time in the PCB from an air knife to blow a bunch of melted solder hot air or nitrogen, such as wide as the wind and the PCB knife can be full width of the entire PCB quality control, to eliminate bridging or short-circuit and reduce operating costs.

There are other defects that may occur include cold solder joint or omitted to welding, also known as open circuit, if the flux is not painted when the PCB will form. If the flux is not enough, or preheat stage is not running correctly, will result in undesirable top surface infiltration.

Although the welding bridging or short-circuit testing can be found in the weld, but to know the cold solder joint in the weld quality inspection, tested, and in the future use problems. Use problems will seriously affect the formulation of the minimum profit targets, not only because the replacement will live expenses incurred, and because customers have found that the quality problems, which will affect future sales.

Stage in the wave soldering, PCB must be immersed in the solder wave will solder coating, so the peak height of control is a very important parameter. You can attach a closed-loop control of peaks so that the height of peaks remain unchanged, would be a sensor installed in the transmission chain of peaks above the rail to measure the height of peaks relative to the PCB, and then speed up or reduce the pump speed to maintain the correct tin a high degree of immersion tin.

Tin slag heap of the wave soldering is harmful. If the tin aggregation slot Dross, then the tin slag into the possibility of peaks inside will increase. Tin-pump systems can be designed to avoid this problem, so from the bottom of the tin bath, rather than the top of the tin slag aggregate extraction tin. Use of inert gas can also reduce Dross and cost savings.

Inertia welding

Nitrogen soldering tin slag can be reduced to save costs, but the user must bear the cost of nitrogen as well as the transmission system up-front investment. Usually require a compromise of these two factors into consideration, it must be determined to reduce maintenance as a result of defects in solder joints and therefore the rate of infiltration and better savings by lower costs. There is also a low residue technique can be used at this time there will be some flux residues remain on the board, and according to product or customer requirements of these residues can be acceptable.

Such as contract manufacturer for the welding of users in product design, there is no overall control, so they have to seek a wider range of processes, which can be through the use of corrosive flux and cleaning methods to achieve. There will be an initial investment in equipment, but in most cases, this is a lowest-cost approach, as off the production line are high-quality products but do not need rework.

Productivity in

Many users use of automated on-line equipment, the week seven heaven and earth to manufacture and assemble. Therefore, the issue of productivity is more important than ever before, all devices must have the highest possible uptime. Wave soldering equipment in the choice, we must consider the various systems of the MTBF (Mean Time Between Failure) and MTTR (average repair time). If a system uses that can be raised panels, can be folded completely controlled by the back door, as well as desktop repair doors have a high ease of maintenance, you can achieve a lower MTTR. Similarly, consider the module to reduce the maintenance and the reduction of solder flux coating device can also be made to maintain a shorter maintenance time.

Be adopted wave soldering method?

Wave soldering method or process used depends on the complexity of the product as well as the production of complex products as well If you want to output of high technology with nitrogen could be considered such as CoN 2 Tour crest to reduce solder dross and increase infiltration of .

If you use a medium-size machine, its function can be divided into nitrogen art craft and air craft. Users can still air environment, dealing with complex board, in this case, it can be according to customer's require the use of corrosive flux, in soldering after cleaning, or the use of low solid flux.

Air knife to bridge technology

Years in a variety of machine types, there are many additional options for the advanced. Speedline ELECTROVERT example, offers a patented hot-air knife to bridge technology is used to remove solder bridges, as well as do non-destructive testing force. Air knife slot at the exit of welding to the horizontal was 40 to 90 angle to the solder joint injection 0.4572mm narrow hot air. It can make all the air left in the first due to perforation of the weld seam is not a good solder joints to re-filling, but does not affect the normal joints.

However, we must pay attention to, to make solder joints significantly enhance the quality does not need to wave soldering equipment to set more options. But also for all production equipment, check the accuracy of each of the real engineering data is also very important, the best approach is to use the machine before buying the first board to run about.

Machine Selection

Based on price and output, wave soldering machines can be divided into three categories.

40,000 to 55,000 U.S. dollars can buy an entry-level, low-or medium-yield vertical machines. Although there are cheaper desktop models, but these are only suitable to be used in research and development or production of prototypes of the occasion, because for manufacturers to meet the growing demand for their part, have not been used.

Typical of such machines the belt output speed of about 0.8 meters / minute to 1 m / min, using foam or spray-type flux-type coating equipment. May not have the convection preheating device, but most vendors offer both single wave and double wave performance machine.

48,000 to 80,000 U.S. dollars can buy one in Taichung and production machines, preheat zone is about 1.22 meters to 1.83 meters, the production rate of about 1.2 m / min to 1.5 m / min. In addition to the double peak as a standard configuration, but also offers more advanced configuration, such as the inert gas environment.

In the high-end market, with 95,000 to 190,000 U.S. dollars can buy high-volume machines, can run 24 hours a day, and with little manual intervention. Generally use 1.83 meters to 2.44 meters warm-length, can be 2 m / min or higher yields.

It also includes many advanced features, such as statistical process control and remote monitoring devices, as well as in the same machine within the existing spray, foam-type coating system, there are peak-type flux, while there may be three peak performance.

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