Introduction to Via Hole Plugging of FPC Circuit Board

The via hole functions as a connection between the lines, the development of the electronics industry promotes the development of the FPC circuit board. It also imposes higher requirements on the manufacturing process and surface mount technology of the printed board.

The FPC circuit board plugging process came into being, and the following requirements should be met:

1. There is copper in the via hole, and the solder resist can be plugged;

2. There must be tin-lead in the via hole, which has a certain thickness requirement (4 micron). No soldering ink should enter the hole, causing the solder ball to be hidden in the hole;

3. The via hole must have a solder mask ink plug hole, which is opaque, and must not have tin ring, solder ball and leveling requirements.

With the development of electronic products in the direction of “light, thin, short and small”, FPC circuit boards are also developing to high density and high difficulty. Therefore, a large number of FPC circuit boards of SMT and BGA appear.

Customers require plugging when mounting components. There are five main functions of plugging:

1. Prevent the short circuit of tin from the via hole through the component surface during the wave soldering of the FPC board; especially when we put the via hole on the BGA pad, we must first make the plug hole and then gold plating to facilitate the BGA soldering.

2. Avoid flux remaining in the via hole;

3. After the surface mount of the electronics factory and the component assembly are completed, the PCB is vacuumed on the test machine to form a negative pressure.

4. Prevent surface solder paste from flowing into the hole to cause solder joints, affecting mounting;

5. Prevent the solder balls from popping out during wave soldering, causing a short circuit.