PCB News - Multi-layer PCB pressing

Multi-layer PCB pressing

Each single layer must be pressed together to make a multilayer board. The pressing action includes adding an insulating layer between the layers and bonding each other firmly. If there are vias through several layers, each layer must be processed repeatedly. The wiring on the outer sides of the multilayer board is usually processed after the multilayer board is laminated.

Process solder mask, screen printing surface and gold finger part plating

Next, cover the solder mask on the outer wiring, so that the wiring will not touch the plating part. The screen printing surface is printed on it to mark the position of each part. It cannot cover any wiring or gold fingers, otherwise it may reduce the solderability or the stability of the current connection. The gold finger part is usually plated with gold, so that high-quality current connection can be ensured when the expansion slot is inserted.

test

To test whether the PCB has a short circuit or open circuit, optical or electronic testing can be used. The optical method uses scanning to find the defects in each layer, and the electronic test usually uses a flying-probe to check all connections. Electronic testing is more accurate in finding short circuits or open circuits, but optical testing can more easily detect incorrect gaps between conductors.

Parts installation and welding

The next step is to install and weld the parts. Both THT and smt parts are installed on the PCB using machinery and equipment.
THT parts are usually soldered by a method called Wave Soldering. This allows all parts to be soldered to the PCB at once. First cut the pins close to the board and bend them slightly to allow the parts to be fixed. Then move the PCB to the water wave of the co-solvent, so that the bottom is in contact with the co-solvent, so that the oxide on the bottom metal can be removed. After heating the PCB, this time it is moved to the molten solder, and the soldering is completed after contact with the bottom.

The method of automatically welding smt parts is called Over Reflow Soldering. The paste solder containing flux and solder is processed once after the parts are mounted on the PCB, and then processed again after the PCB is heated. After the PCB has cooled down, the soldering is complete, and the next step is to prepare for the final test of the PCB.

The above is the introduction of multilayer PCB lamination. Ipcb is also provided to PCB manufacturers and PCB manufacturing technology.