Lastly, there is no requirement or such need for glue for SMDs.Moreover, selective soldering doesn’t need the application of excess heat.Selective soldering works very well for special THT cases.The operator can also limit the areas of the board to be masked.Selective soldering can lead to cost optimization.
Selective soldering allows the operator to customize the board to be able to accommodate different parameters of different components. When you are using selective soldering, there is no need to use expensive aperture wave solder pallets. But now, this soldering process is done quickly without needing a real hand. Before selective soldering, expert technicians were required to hand-solder the through holes. These authorities allow the operator to be more precise with the soldering process without the need for a steady hand to handle and control the soldering iron. The operator programs the exact place where the molten solder nozzle should go for soldering or solder application. The solder joints after selective soldering are much more reliable. The operator has the freedom to specify how the nozzle should move, quickly or slowly, to give enough time for the through-hole to be filled with solder. The amount of solder and the temperature of soldering depends on the operator. Selective soldering gives the soldering operator the flexibility to utilize the soldering variables so that greater solder joints can be achieved in a short time and with less heat. Dip soldering has different capabilities than drag soldering they constitute a robust process with the least cycle times when used together. Multiple connections are soldered at once, but different tooling plates are required for each type of PCB. However, the results achieved from both drag and dip soldering are different due to heat distribution characteristics and thermal transfer characteristics of different types of boards.ĭip soldering involves a process of dipping the PCB on a custom nozzle plate that solders all the joints in one go. Another drawback of drag soldering is extended cycle time.ĭrag soldering does not contain certain capabilities like dip soldering. In drag soldering, the lead lengths are limited. It also increases the robustness and reliability of the drag soldering. It eliminates bridges from the PCB because it washes off the oxides. Heat transfer in drag soldering is inherently better than dip soldering due to the motion of the board and solder. On the other hand, some people think that there is no requirement of soldering before preheating.ĭrag soldering is mainly done using small single nozzle waves. Some people think that flux should be sprayed after the preheating process. Preheating can be done in different combinations. The settings of preheating temperature depend on the thickness, device package size, and flux of the PCB. Keep in mind that it is not to reduce the thermal stress on the PCB. Preheating in selective soldering is mainly to remove the flux from the parts where it is not needed, and the solder will have a proper viscosity before going into the solder wave. Micro-hole spray is the most accurate and used the most because it never contaminates the area outside the solder joint. The spraying phenomenon of the flux should be accurate during the microwave peak welding after the reflow process. These are single-nozzle spray, micro-hole spray, simultaneous multi-point spray, and pattern spray. 
Now, there are different types of flux sprays available. This robot holds the PCB and takes it through the flux nozzle, and then the flux is sprayed on the PCB to be soldered. The flux is usually sprayed by the robot. It is essential to make the flux sufficiently active as it will prevent oxidation and bridging of the PCB, mainly at the end of solder heating and soldering. Let us get into the details of these processes and see how it works.įlux coating is the first and most crucial step of selective soldering. The process of selective soldering mainly consists of four processes.Įach of these processes is significant and contributes to the selective soldering process.
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