Hotbar Soldering Process Control

The principle of hotbar soldering machine is to first print the solder paste on the solder pad of PCB, then melt the solder paste and pre weld it on the PCB, and then place the solder to be soldered (generally FPC) on the printed PCB, and then use the heat of hot indenter to melt the solder and connect two electronic components to be connected.

1. Control the gap between the hot indenter and the object to be pressed (usually PCB). When the hot indenter drops to the object to be pressed, it must be completely parallel to the object to be pressed, so that the object to be pressed will be heated evenly. The general method is to loosen the screws which are locked on the hot press by the hot head first, and then adjust them into manual mode. When the hot head is lowered and pressed on the pressing material, confirm that after full contact, lock the screws tightly, and finally raise the hot pressing head. Usually, the object to be pressed is PCB, so the hot indenter should be pressed on the PCB. It's better to find a plate without tin to adjust the machine.

2. Control the fixed position of the object to be pressed. Generally, the objects to be pressed are PCB and flex board. It is necessary to confirm that the PCB and flex board can be fixed on the fixture platform. At the same time, it is necessary to confirm that the position of hotbar is fixed each time, especially in the front and back direction. When there is no fixed object to be pressed, it is easy to cause empty welding or crush the quality problems of nearby parts. In order to achieve the purpose of fixing the object to be pressed, special attention should be paid to the design of positioning holes when designing PCB and FPC. The best position is near the hot pressing of molten tin, so as to avoid the displacement of FPC when pressing down.

3. Flux can be added as appropriate to facilitate the smooth welding. Of course, it's best to achieve the goal without adding. Because the solder paste is printed on the circuit board and flows through the reflow oven, the flux in the original solder paste has evaporated completely, so when pressing hotbar, it is usually necessary to add another flux to improve its soldering ability. The purpose of flux is to remove the oxide, because it is the solder paste printed on the circuit board. After a certain time of contact with the air, the oxide will be produced on the surface, and there are many impurities and organics in the air, which will affect the quality of welding. Therefore, flux is generally used in hotbar soldering to facilitate the smooth welding.