Views: 0 Author: Site Editor Publish Time: 2022-03-29 Origin: Site
Through hole reflow (THR) is to assemble through-hole components and special-shaped components by using reflow soldering technology. Due to the increasing emphasis on miniaturization, increasing functions and increasing component density, many single and double-sided boards are mainly surface mount components. However, due to the inherent strength, reliability, applicability and other factors, in some cases, through-hole devices are still superior to SMC, especially the connector at the edge of PCB.
The disadvantage of using through hole devices on circuit boards with surface mount components is that the cost of a single solder joint is very high. For this kind of assembly, the key is to provide synchronous reflow soldering for through hole and surface mount components in a single integrated process. Compared with the conventional SMT process, the amount of solder paste used in the via reflow process is about 30 times more than that in the conventional SMT process.
At present, through hole reflow process mainly adopts two kinds of solder paste coating technology, including：solder paste printing, automatic spot solder paste.
Screen printing is the preferred method to deposit solder paste on PCB. The thickness of the screen is the key factor, which will affect the solder paste amount that is missed to PCB. The stepped mesh plate can be used, and the thicker area is specially designed for through hole devices. The design of this steel mesh can meet the requirements of different solder paste.
Automatic solder paste spotting successfully deposits the correct volume of solder paste for through holes and special-shaped components. It provides the flexibility and ability to deposit a large amount of solder paste that screen printing may not be able to achieve. It is recommended to use a nozzle with a slightly larger diameter than PTH when applying solder paste to bare plated through hole (PTH). In this way, the solder paste is forced to cling to the hole wall of PTH, and the material is slightly extruded from the bottom of PTH, and then the component is inserted from the opposite direction of the solder paste. If a nozzle with a smaller diameter than PTH is used, the solder paste will be discharged from the hole and cause serious solder paste loss.
Through hole reflow welding can replace wave soldering in many ways to realize the welding of plug-in components, especially the welding of plug-in solder joints with high density chip components (or SMD with fine spacing) distributed on the processing welding surface, which greatly improves the welding quality, which is enough to make up for the lack of expensive equipment. The appearance of through hole reflow soldering is helpful for enriching soldering means, improving PCB assembly density, improving soldering quality and reducing process flow. Our company purchases superior raw materials and components from the authorized dealer, and we have established a quality control department to strictly monitor each production detail. Additionally, all products can be functionally tested upon our customer's requirements to ensure that only qualified products leave our factory.
