What is the reflow time for reflow soldering

Reflow soldering reflow time refers to the process in which the solder paste reaches its melting point and, under the action of its liquid surface tension and flux assistance, the liquid tin flows back to the component pins to form solder joints, allowing the circuit board solder pads and components to be soldered together as a whole. It is also known as the reflow soldering reflow process.

Reflow soldering is the process of soldering components onto a PCB board, which involves surface mounted components. Reflow soldering relies on the action of hot air flow on the solder joint, and the adhesive flux undergoes physical reactions under a certain high-temperature air flow to achieve SMD welding; The reason why it is called "reflow soldering" is because the gas circulates in the welding machine to generate high temperature and achieve the welding purpose.

Due to factors such as the formation rate of common boundary metal compounds and the decomposition rate of salt based metals in solder, their generation and filtration are not only proportional to temperature, but also to the time above the solder melting point temperature. To reduce the generation and filtration of common boundary metal compounds, the time above the melting point temperature must be reduced, usually set between 45 and 90 seconds. This time limit requires the use of a fast temperature rise rate, The rapid rise from the melting point temperature to the peak temperature, while considering the thermal stress factor borne by the component, the rise rate must be between 2.5 and 3.5 ℃/sec, and the maximum change rate cannot exceed 4 ℃/sec.

The speed of reflow soldering determines the most important factor in the quality of reflow soldering. If the time is too fast or too slow, it will cause a large number of defective reflow soldering products. The so-called reflow time refers to the welding time when the product reaches the welding area, usually referred to as reflow time. The reflow time should be as short as possible while ensuring that the component completes good welding, usually 30-60 seconds, which is best. Different solder pastes have different requirements. Excessive reflow time and higher temperatures, such as reflow time greater than 90 seconds and maximum temperature greater than 230 degrees, can cause thickening of the intermetallic compound layer, Affects the long-term reliability of solder joints.