What are the solutions for plug holes in pcb drilling?

What are the solutions for plug holes in pcb drilling?

What is PCB drilling plug hole? The so-called PCB drilling hole plug refers to that the entire through-hole is blocked by impurities, resulting in the failure of normal use in the hole during the later electroplating copper deposition, resulting in the absence of copper in the hole and other phenomena. What are the main factors that lead to PCB drilling plug hole: 

① Reuse of base plate;

② The substrate material has moisture or foreign matter;

③ The effective length of drill bit is not enough;

④ Insufficient suction force;

⑤ The drill bit is too deep into the backing plate;

⑥ The drill nozzle structure is not good;

Treatment method:

① set the drilling depth reasonably;

② Properly adjust the dust suction force of the borehole to 7.5 kg/s;

③ Select high-quality substrate materials;

④ Select the appropriate bit length according to the stack thickness;

⑤ Replace the base plate;

With the rapid development of the electronic industry, the user's requirements for electronic products are also increasing, which puts forward higher requirements for the PCB manufacturing process, which led to the emergence of the PCB plug hole. The conventional PCB through hole plays the role of connecting and conducting lines, and the plug hole is no more: 1 The copper in the through hole is sufficient, and the resistance welding can be plugged or not;

2. There must be tin and lead in the through-hole, with a certain thickness requirement (4 microns), and there must be no solder resist ink entering the hole, causing tin beads in the hole;

3. The through-hole must be sealed with solder resistant ink, which is not transparent, and shall not have tin ring, tin bead and flatness requirements.

With the development of electronic products in the direction of "light, thin, short and small", and the development of PCBs in the direction of high density and high difficulty, there are a large number of SMT and BGA PCBs, and customers require plug holes when mounting components, which mainly have five functions:

1 To prevent short circuit caused by tin penetrating the component surface from the through hole during PCB wave soldering; In particular, when we put the vias on the BGA pad, we must do the plug hole first and then the gold-plating treatment to facilitate the BGA welding.

2. Avoid the flux remaining in the through hole;

3. After the completion of SMT processing and component assembly in the electronics factory, the PCB should be vacuumed on the testing machine to form negative pressure:

4 Prevent the surface solder paste from flowing into the hole, causing faulty soldering and affecting the installation;

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