How to Avoid Wave Soldering Problems

- Mar 30, 2018 -

Wave soldering


  As the current components become smaller and smaller and the PCB becomes more and more dense, the possibility of bridging and short circuit between solder joints has increased. But there are some effective methods to solve this problem, one of which is the use of wind knife technology. This is when PCB leaves the crest, it uses a wind knife to blow out a bunch of hot air or nitrogen to the melted solder joint. This wind knife with the same width as PCB can conduct quality check on the entire PCB width, eliminate bridge connection or short circuit and reduce operation cost. There are other possible defects including weld or leakage welding, also known as the open circuit, if no flux will be formed on PCB on. If the flux is not enough or the preheating stage is not running correctly, the top surface will be badly infiltrated. Although welding bridged or short circuit can be found in the test after welding, but to know that the weld will test in quality inspection after welding is qualified, and the problems in use. Problems in use will seriously affect the minimum profit index, not only because of the cost of on-site replacement, but also because customers find quality problems, which will also affect future sales.

In the wave peak welding stage, the PCB must be immersed in the wave peak to apply the solder on the solder joint, so the height control of the wave peak is a very important parameter. A closed loop control is added to the wave crest to keep the wave height unchanged. An inductor is mounted on the conveyor chain guide on the top of the wave crest to measure the height of the wave peak relative to the PCB, and then to accelerate the speed of the tin pump to keep the right immersion height. The accumulation of tin slag is harmful to the wave soldering. If tin slag is gathered in the tin trough, the possibility of the tin slag entering the wave peak will increase. It is possible to avoid this problem by designing a tin pump system to extract tin from the top of the tin trough instead of the top of the tin slag. The use of inert gas can also reduce tin slag and save cost.

Inert welding editors

Nitrogen welding can reduce the cost of tin slag, but the user must bear the cost of nitrogen and the initial investment of the transport system.  Usually, the above two factors need to be considered in compromise. Therefore, we must determine the cost saved by reducing maintenance and improving the defect rate due to the better penetration of solder joints.  In addition, low residue technology can also be used. There will be some flux residue left on the board at this time, and the residues are acceptable according to the requirements of the products or customers. Users such as contract manufacturers do not have a general control over the design of welded products, so they are looking for a wider range of processes, which can be achieved through the use of corrosive flux and cleaning. Although there will be an initial equipment investment, in most cases, this is the lowest cost way, because the products from the production line are all high quality products without rework.