What is the reflow soldering process requirement for PCBA processing?

Reflow soldering process requirement of SMT

Abstract: Reflow soldering is an important part of the SMT placement process. It is an important link to form the connection between components and circuit board electrical appliances after front-end PCB solder paste printing and PCB patch installation. Reflow soldering is to melt the solder paste into liquid by internal heating to weld components and PCB pads together. The components and pads are then solidified together by cooling. So what are the important process requirements for reflow soldering? The following SZTech-SMT will give you a detailed introduction to the reflow soldering process requirements.

At present, reflow soldering technology in SMT chip processing has been widely used in the field of electronic manufacturing. All electronic products, industrial, medical, communication, and other circuit boards used in our lives, and chip processing components are all through this reflow soldering process. soldered to the PCB board. The advantage of this process is that the temperature setting of each temperature zone is easy to control. After the placement is completed, it can be passed through the furnace in time to avoid oxidation through the same track of the wire body. If it is a double track, different PCBAs can be reflow soldered at the same time, and the manufacturing cost is also easier to control and reduce. The principle of this kind of equipment is to control the heat generated through the internal circuit of the equipment through the temperature we set. After the nitrogen gas is heated to the set temperature, the upper and lower hot air rolling cycles are used to heat the PCB and the components evenly, and the solder paste reaches a certain melting point (lead-free 217 degrees Celsius) to realize the soldering of the component pins and the PCB pads, and then solidify.

The curve of the solder paste

In combination with the temperature curve provided by the solder paste manufacturer, reasonably set the actual chip processing PCB board reflow soldering temperature curve and conduct real-time testing of the temperature curve regularly.

PCB design

Welding should be carried out according to the welding direction of PCB design, including comprehensive factors such as circuit board material, thickness, grounding area, PCB board size, component size, and heat absorption

The vibration of the reflow oven

Strictly prevent the vibration of the conveyor belt during the reflow soldering process, and monitor and maintain the equipment in real time.


The welding effect of the printed board must be checked. Cold soldering (cold sweat is now called insufficient melting of solder paste) is difficult to judge with the naked eye, resulting in poor circuit connection performance.


Check whether the surface of the solder joint is glossy, whether the shape of the solder joint is semi-crawling, and whether there are solder balls and residues around the solder joint, short circuits, and false soldering. In particular, check the color change on the surface of the PCB. If there is discoloration, it means that the temperature setting of the PCBA board for the current patch processing is too high. And adjust the reasonable temperature curve according to the inspection results. It is necessary to inspect the welding quality at the back end of the reflow furnace from time to time to avoid batch welding problems and reduce unnecessary losses.

Summary of reflow soldering process requirement of SMT

The above content is shared by SZTech-SMT for you on the principle of SMT chip reflow soldering. I hope it will be helpful to you. To learn more about SMT chip processing, welcome to visit www.sztech-smt.com

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