PCB Tech - What is the difference between the solder mask and the flux layer of the multilayer circuit board?

In the manufacturing process of multilayer circuit boards, what is solder mask? What is flux? And what is the difference between the two? In general, the welding layer is mainly to prevent the direct exposure of the copper foil of the multilayer circuit board to the air, and play a protective role, and the welding layer is used as a steel mesh, which can accurately remove the tin Put the paste on the patch pad that needs to be soldered.

The difference between the solder mask and the solder flux layer of the multilayer circuit board

Resistance pad refers to the part of the PCB circuit board to be painted with green oil. In fact, this solder mask uses a negative output, so after the shape of the solder mask is mapped to the board, the solder mask is not painted with green oil, but the copper skin is exposed. Usually in order to increase the thickness of the copper skin, the solder mask is used to scribe lines to remove the green oil, and then tin is added to increase the thickness of the copper wire.

The soldering layer is used when the machine is patching. It corresponds to the pad of the patch component. In SMT processing, a steel plate is usually used, and the PCB corresponding to the component pad is punched, and then solder paste is placed on the steel plate., When the PCB circuit board is under the steel plate, the solder paste leaks, and it happens that every pad can be stained with solder, so usually the solder mask cannot be larger than the actual pad size.

The difference between solder flux and solder mask on multilayer circuit boards

Both layers are used for soldering. It does not mean that one is soldered and the other is green oil, but:

1. The soldering layer is used for chip packaging.

2. By default, the area without solder mask should be painted with green oil;

3. The solder mask means to open a window on the whole piece of solder mask green oil, the purpose is to allow soldering;