Method for repairing a fine line

A method for repairing a fine line, comprising:

• 1) filling nano metal particles in a defect of a circuit board, wherein a liquid or a paste prepared by adding the nano metal particles into a solvent is sent to the defect by a spray nozzle or a drip nozzle;
• 2) irradiating, by a laser, or heating, the nano metal particles in the defect, such that the nano metal particles in the defect are metallurgically bonded to an original line of the circuit board;
• and
• 3) cleaning a surface of the circuit board to remove residual nano metal particles on parts of the circuit board where metallurgical bonding is not performed, thereby completing line repairing of the circuit board;
• wherein in step 1), after the nano metal particles are filled in the defect, a light-transmitting plate covers the defect, and a downward force is applied to the light-transmitting plate;
• and
• in step 2), during the irradiation by the laser, the laser is focused on the nano metal particles under the light-transmitting plate,
• in step 2), when the laser irradiates the liquid or paste prepared by adding the nano metal particles into the solvent, the liquid or paste is irradiated by the laser;
• or the liquid or paste on the defect is preheated and dried using a laser with first energy lower than preset energy, so as to reduce an organic content in the liquid or paste;
• and then the liquid or paste is irradiated by a laser with second energy higher than the preset energy, so that the liquid or paste in the defect is metallurgically bonded to the original line.