Reflow oven is used for welding of SMT components on the circuit board welding production equipment, is to rely on the furnace heat convection on the printed circuit board solder paste is the solder paste on the solder joint, to melt into liquid tin solder paste to make SMT components and circuit boards welding welding together, then after reflow oven cools solder joints, solder paste of colloidal physical reaction under the certain high temperature air to SMT process welding effect.
The following is a detailed description of the working principle of reflow soldering:
Due to the need of continuous miniaturization of electronic PCB board, the appearance of sheet and element, the traditional welding method has been unable to meet the needs. In hybrid integrated circuit board assembly adopted the reflow soldering, assembly welding components mostly chip capacitors, chip inductor, SMT transistor and diode etc., with the development of SMT the whole technology improvement, the emergence of a variety of SMT components in SMT components, as part of SMT technology reflow soldering process technology and equipment have been expanded to a corresponding its applications are becoming more and more widely, almost have been applied in the field of all electronic products.
Reflow soldering is to realize the mechanical and electrical connection between the solder end or pin of surface assembly components and the PCB solder pad by remelting the paste solder predistributed on the PCB solder pad. Reflow soldering is to weld the components to the PCB board, and reflow soldering is to surface mount the devices. Reflow soldering is based on the role of hot air flow on solder joints, colloidal flux in a fixed high temperature airflow under the physical reaction to achieve SMD welding; It is called "reflow soldering" because the gas circulates through the welder to produce high temperatures for welding purposes.
The working principle of reflow soldering is divided into the following steps:
I. When the PCB enters the heating zone, the solvent and gas in the solder paste evaporate. At the same time, the flux in the solder paste wetting the pads and the pins of the component end, the solder paste softening, collapsing and covering the pads, isolating the pads and pins of the components from oxidation.
II. When the PCB enters the insulation area, the PCB and components should be fully preheated to prevent the PCB and components from being damaged when the PCB suddenly enters the welding high temperature area.
III. When the PCB enters the welding area, the temperature rises rapidly so that the solder paste reaches the molten state. The liquid solder wetting, diffusing, diffusing or reflux mixing of the solder contact on the pads of PCB and the end pins of components.
IV. When the PCB enters the cooling zone to solidify the solder joints, the reflow welding process is completed.
After the solder paste is printed and pasted on the circuit board of SMT patch element, the circuit board is formed after being transported by the guide rail of reflow soldering and the above four temperature zones are acted on.