First, the open circuit caused by the exposed substrate
     1. The PCB CCL has scratches before entering the warehouse;
     2. The PCB CCL is scratched during the opening process;
     3. The PCB CCL is scratched by the drill nozzle during drilling;
     4. The PCB CCL is scratched during the transfer process;
     5. When the board is stacked after sinking copper, the surface copper foil is bumped due to improper operation;
     6. The surface copper foil is scratched when the production board passes the horizontal machine;

    Second, there is no copper open circuit in the PCB hole
     1. There is no copper in the sinking copper hole;
     2. There is oil in the hole to cause no copper in the PCB hole;
     3. Excessive micro-etching causes no copper in the PCB holes;
     4, poor plating caused no copper in the PCB hole;
     5. The hole in the drill hole or the dust blocking hole causes no copper in the PCB hole;

   Third, the fixed position open
     1. The scratch on the alignment film line creates an open circuit;
     2. There is a trachoma on the parallel line to open the road;

   Fourth, anti-plating open road
     1. Open circuit caused by dry film breakage on the line during development;
     2. The ink is attached to the surface of the line to cause an open circuit;