PCB Technical - The reason why there is no copper in the hole of the multilayer circuit board and the improvement measures have to be understood

The reason why there is no copper in the hole of the multilayer circuit board and the improvement measures have to be understood
To measure the process level of a circuit board manufacturer, the first thing that comes to mind is the number of layers in the production and processing of the circuit board, so the multi-layer circuit board has stricter technological requirements during the production process. The multi-layer circuit board needs to sink copper in the hole to make the via hole. Copper becomes a via. However, after inspection during the production process, it is occasionally found that there is no copper in the hole or copper is not saturated after the copper is deposited. What is the reason for the absence of copper in the hole? Is there any way to improve it?

1. Drilling dust plug holes or thick holes.
   2. There are bubbles in the potion when the copper is sinking, and the copper is not sinking in the hole.
   3. There is circuit ink in the hole, the protective layer is not electrically connected, and the hole is free of copper after etching.
   4. The acid-base solution in the hole is not cleaned after the copper is deposited or after the board is powered on, and the parking time is too long, resulting in slow biting corrosion.
   5. Improper operation, too long in the process of micro-etching.
   6. The pressure of the punching plate is too high, (the design punching hole is too close to the conductive hole) and the middle is neatly disconnected.
   7. Poor penetration of electroplating chemicals (tin, nickel).
   Make improvements to these 7 reasons for the hole-free copper problem.
   1. Add high-pressure water washing and de-smearing processes to holes that are prone to dust (such as 0.3mm or less aperture containing 0.3mm).
   2. Improve potion activity and shock effect.
   3. Change the printing screen and counterpoint film.
   4. Extend the washing time and specify how many hours to complete the graphics transfer.
   5. Set the timer.

6. Increase explosion-proof holes. Reduce the force on the board.
7. Do penetration testing regularly. So knowing that there are so many reasons that can cause the hole to have no copper open circuit, do you need to analyze it every time? ? Should we go to prevent and supervise in advance.
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