According to the company’s own conditions, a large number of experiments have been carried out on the pre-treatment process, parameters, and operational considerations. The process and parameters have been optimized, resulting in good outcomes.
Process flow of pre-treatment:
The specific process flow includes water pre-soaking, pickling, water cleaning, brushing, high-pressure water washing, municipal water washing, water roller squeezing, cold air drying, and hot air drying.
Specific operations and precautions for pre-processing:
1. Water pre-soaking: This step is crucial for washing away impurities on the copper surface and wetting the copper layer to accelerate pickling speed. Control the transfer speed of the machine to prevent excessive grinding of the copper surface.
2. Pickling: Spraying with a 5-10% sulfuric acid solution for about 1 minute to remove chemical impurities from the PCB surface. Rinse with city water after pickling.
3. Brushing the board: Use a 300-mesh brush for rough brushing followed by a 500-mesh brush for fine brushing. Control the pressure to prevent scratches and enhance the mechanical action between the solder mask and board surface.
4. High-pressure water washing: Maintain pressure above 12.5bar to wash away copper powder post-brushing and ensure sufficient insulation resistance.
5. Water squeezing rollers: Use three sets of squeezing rollers to absorb water on the printed board surface after high-pressure water washing. Keep the rollers semi-dry to prolong their lifespan.
6. Cold air drying: Blow out water in the holes to prevent oxidation points on the board surface. Control the cold wind direction to avoid oxidation spots and board jamming.
7. Hot air drying: Control temperature between 75-85℃ to dry moisture on the board surface and holes, ensuring proper adhesion of ink after silkscreen solder mask application.
Process flow of pre-treatment:
The specific process flow includes water pre-soaking, pickling, water cleaning, brushing, high-pressure water washing, municipal water washing, water roller squeezing, cold air drying, and hot air drying.
Specific operations and precautions for pre-processing:
1. Water pre-soaking: This step is crucial for washing away impurities on the copper surface and wetting the copper layer to accelerate pickling speed. Control the transfer speed of the machine to prevent excessive grinding of the copper surface.
2. Pickling: Spraying with a 5-10% sulfuric acid solution for about 1 minute to remove chemical impurities from the PCB surface. Rinse with city water after pickling.
3. Brushing the board: Use a 300-mesh brush for rough brushing followed by a 500-mesh brush for fine brushing. Control the pressure to prevent scratches and enhance the mechanical action between the solder mask and board surface.
4. High-pressure water washing: Maintain pressure above 12.5bar to wash away copper powder post-brushing and ensure sufficient insulation resistance.
5. Water squeezing rollers: Use three sets of squeezing rollers to absorb water on the printed board surface after high-pressure water washing. Keep the rollers semi-dry to prolong their lifespan.
6. Cold air drying: Blow out water in the holes to prevent oxidation points on the board surface. Control the cold wind direction to avoid oxidation spots and board jamming.
7. Hot air drying: Control temperature between 75-85℃ to dry moisture on the board surface and holes, ensuring proper adhesion of ink after silkscreen solder mask application.
