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PCB hole plugging mechanism research and effective control

 PCB board hole plugging mechanism research and effective control

1. The cause of the problem


    With the continuous improvement of PCB manufacturing accuracy, the vias on the PCB are getting smaller and smaller. For mechanically drilled mass production boards, 0.3mm diameter vias are the norm, and 0.25mm or even 0.15mm is not uncommon. Accompanying the shrinking of the aperture is the lingering via plug. After the small holes are plugged, the boards are often broken and not broken after the holes are electroplated, and the base cannot be detected by the electrical test, and then flows into the client. After high temperature welding, thermal shock or even assembly, the incident occurred in the middle of the east window. Only then did a serious review, it was too late!



    If we can start with the production process and control the processes that may produce plugs one by one to prevent the occurrence of defective plugs, it will be the best way to improve quality. I tried to explain the mechanism of some hole plugs from the process, and give some effective control methods to avoid or reduce the occurrence of bad hole plugs.


2. Analysis of bad hole plugs in each process


    As we all know, the processes related to PCB production and hole processing include drilling, de-glueing, copper sinking, plate plating, pattern transfer, and pattern plating. Therefore, it is determined that hole plugs are also these processes, which are introduced one by one below.



    Although someone grumbled for drilling. But realistically speaking, drilling is still one of the main processes that lead to bad hole plugging. According to a statistical analysis done by the author, it is found that 35% of the holes without copper are caused by hole plugging caused by drilling. Therefore, the control of drilling is the focus of poor control of hole plugs. In my opinion, the following aspects are the main control points:


   1. Confirm reasonable drilling parameters based on the test results, rather than the traditional experience of a master with apprentices (as follows, if the knife is too fast, it is easy to plug);


   2. Regularly adjust the drilling rig;


   3. Ensure the dust collection effect;


   4. Understand that it is the drill that drills on the tape to bring the glue into the hole, not the tape itself. Therefore, the drill should not be drilled onto the tape at any time;


   5. Develop effective inspection measures for broken drills;


   6. Many manufacturers conduct a high-pressure air dust collector blow hole dust removal treatment after drilling, which can be promoted and used;


   7. The deburring process before copper sinking should have ultrasonic washing and high-pressure washing (pressure above 50KG/CM2), etc.