Precautions for lead-free reflow welding

What is the difference between lead-free reflow soldering and leaded soldering?

First of all, we should understand that the whole process of lead-free welding is longer than that of lead welding, and the welding temperature required is also higher, mainly because the melting point of lead-free solder is generally higher than the melting point of lead solder, and the wettability will be worse. So, what do you need to pay attention to in the lead-free reflow welding process?

Before the lead-free reflow welding begins, we first need to choose the right welding material, because in terms of its welding process, the selection of lead-free solder, solder paste, flux and other materials is particularly important and quite difficult. In the selection process of these materials, we need to take into account the type of welding components, the type of circuit board and its surface coating status, which are generally selected by experience.
After selecting the welding material, we also need to choose the welding method, which generally needs to be selected according to the specific situation, such as in terms of component type, reflow welding method can be used for some surface mounted components, and wave soldering or spray welding can be selected for through hole inserted components. Here we also roughly introduce several common welding applications, for wave soldering, it is mainly suitable for some of the whole board through the hole insert components suitable for welding, dip welding method is more suitable for some of the whole board is relatively small, or there are parts of the board through the hole insert components when welding, Spray welding is more common in the welding of individual components on some plates or a small number of through-hole inserts. After the welding method is selected, the type of welding process is determined, at this time, we only need to select the equipment according to the welding process and the related process control wants to check together.
In addition, the manufacturer of lead-free reflow welding also needs to continuously improve the lead-free welding process, so that the product can achieve higher requirements in quality and pass rate. For any lead-free welding process, changing its welding materials and updating equipment can effectively improve its welding performance.