Cooling device for lead-free reflow soldering

The soldering temperature of lead-free reflow soldering is obviously higher than that of ordinary reflow soldering, which puts forward higher requirements for the cooling function of the equipment. Controllable rapid cooling rate can make the structure of lead-free solder joint more compact, which is conducive to improving the mechanical strength of solder joint.

Especially in the production of large heat capacity circuit boards such as communication backplanes, if only air cooling is used, it is difficult for the circuit board to meet the cooling requirements of 3-5 degrees / second, and the cooling slope cannot meet the requirements, which will loosen the solder joint structure and directly affect the reliability of the solder joint. Therefore, double circulating water cooling device is more recommended in lead-free production, and the cooling gradient of the equipment shall be set and fully controlled as required.

More flux is often added to the solder paste of lead-free reflow soldering. Flux residues are easy to accumulate in the furnace, affecting the heat transfer performance of the equipment, and sometimes even fall on the circuit board in the furnace, causing pollution. There are two ways to remove flux residues during production:

1. Exhaust

Venting is the easiest way to remove flux residues. However, excessive exhaust will affect the stability of hot air flow in the furnace. In addition, the increase of exhaust will directly lead to the increase of energy consumption (including electricity and nitrogen consumption).

2. Multi level flux management

Flux management generally includes filtering device and condensing device. The filtering device effectively separates and filters the solid particles in the flux residue. The cooling device condenses the gaseous flux residue into a liquid in the heat exchanger, and finally conducts centralized treatment in the collection tray.