Before starting the printing process, careful design and preparation are crucial. Firstly, pay attention to the resolution and image quality settings. Avoid excessive scaling of images in software, as this can lead to image distortion or reduced clarity. For instance, if you scale a low - resolution image up too much, it will appear pixelated in the final print. It is recommended to select suitable image formats for printing, such as TIFF, EPS, or JPEG. Steer clear of using untreated source files like PSD.
Another important aspect is the bleeding area. The bleeding area is the edge part reserved to compensate for cutting errors during printing. Usually, a 3mm bleeding area should be reserved. During the design phase, elements like images and text should be extended into the reserved bleeding area to ensure the integrity of the content after cutting. Before submitting for printing, double - check that the bleeding area meets the requirements to prevent content loss due to improper settings.
When it comes to equipment operation, different types of printing machines have their own specific requirements. For example, in the case of a pad printing machine, every day before starting to use it, one must first check the ink in the oil pan. Adjust the dryness, thinness, and color of the ink to normal levels before commencing production. When stopping printing, use a cover plate to cover the ink to prevent solvent evaporation and the entry of debris.
In the process of pad - printing products, if there is a long - term pause, the ink on the rubber head cannot be used to print on the product anymore. Use adhesive tape to clean the rubber head before starting to print new products. For screen printing, the appropriate angle between the squeegee and the screen is around 65°. Maintaining this angle can ensure a more even ink transfer and better printing quality.
In the printing process, materials such as inks and solvents need to be handled with care. Printing workstations often use volatile and flammable solvents like machine - cleaning water and quick - drying water. Do not leave the containers of these solvents open for long periods. Leaving the lids open can not only cause solvent evaporation but also pose a fire hazard.
When dealing with inks, it is necessary to ensure proper storage. As mentioned earlier, when not in use, cover the ink to prevent solvent evaporation and the entry of foreign objects. Also, be aware of the compatibility between inks and different printing materials. Some inks may not adhere well to certain surfaces, which can affect the final printing effect.
When the printed product has a curved surface, different printing methods require corresponding adjustments. For silk - screen printing on curved products, a curved screen should be used. In the case of pad - printing, a rubber head of appropriate size with a corresponding curved surface should be used in conjunction with the steel plate. This ensures that the ink can be evenly transferred to the curved surface of the product.
When taking and placing products from the fixture, pay attention to the force and direction to prevent scratching the products. For example, if too much force is applied when removing a delicate product from the fixture, it may cause surface scratches, which will affect the appearance and quality of the final product.
The environmental conditions of the printing room also have a significant impact on the printing quality. The relative humidity in the printing room should be maintained between 50% - 70% RH, and the temperature should be around 22°C. These conditions can ensure that the ink dries at an appropriate rate and that the printing process proceeds smoothly.
If the humidity is too high, the ink may dry too slowly, leading to smudging or uneven drying. On the other hand, if the humidity is too low, the ink may dry too quickly, which can cause problems such as ink cracking. Additionally, printing personnel should wear dust - free clothing and hats to avoid having hair and lint from their clothes spread in the air and affect the printing quality.
Quality control is an essential part of the printing process. Before mass - production, a first - piece inspection is necessary. Check for any issues such as exposed copper, uneven ink distribution, impurities, ink accumulation around holes, or ink on the pads. If the first piece does not meet the requirements, adjustments need to be made before starting mass - production.
During the printing process, constantly monitor the quality of the prints. Check for ink unevenness, ink accumulation, and poor plug - hole conditions. Also, regularly check the position of the pins on the fixture to prevent them from shifting and damaging the circuits or copper surfaces. After printing, measure the ink film thickness. The ink film thickness should be maintained between 1.0mil - 1.2mil (which can be measured after pre - baking), and the wet film thickness of the printing should be between 20 - 35μm.
In addition, for double - sided printing, start the displacement action of the printing platform to minimize ink accumulation in the holes. After printing, the ink - printed PCB should be placed in an upright frame and left to stand for 10 - 15 minutes. This allows the ink to use its internal cohesion and self - gravity to expel air bubbles before pre - baking.
In summary, printing involves multiple aspects that require careful attention. From design and preparation to equipment operation, material handling, product - specific adjustments, environmental control, and quality management, each step is crucial for achieving high - quality printing results. By following these printing precautions, printers can reduce errors, improve efficiency, and produce products that meet or exceed customer expectations.