1. characteristics of ink
Viscosity and thixotropy
In the manufacturing process of printed circuit board, screen printing is one of the essential important processes.In order to obtain the fidelity of image reproduction, ink must have good viscosity and appropriate thixotropy.The so-called viscosity is the internal friction of the liquid, which means that under the action of external forces, one layer of liquid slides on the other layer of liquid, and the friction exerted by the inner layer of liquid.The mechanical resistance of the thick liquid inner layer is large, while that of the thin liquid is small.The viscosity is measured in mooring.In particular, it should be noted that temperature has a significant effect on viscosity.
Thixotropy is a physical property of liquid, that is, its viscosity drops in the stirring state, and it will recover its original viscosity soon after it is set.By stirring, thixotropy lasts long enough to reconstitute its internal structure.Ink thixotropy is very important to achieve high quality screen printing.Especially in the scraping process, the ink is stirred, which makes it liquid.This effect speeds up the ink through the screen hole, promoting the original screen line separate ink evenly into one.Once the scraper stops moving and the ink returns to a static state, its viscosity quickly reverts to the required data.
Pigment and mineral fillers are generally solid. After fine grinding, the particle size is no more than 4/5 microns, and homogenization flows in a solid form.Therefore, it is very important to require ink with precision.
Precautions for the use of ink
According to the practical experience of most manufacturers, ink must be used in accordance with the following regulations:
2.In any case, the temperature of the ink must be kept under 20 to 25 ℃, the temperature change is not too big, otherwise it will affect the ink viscosity and screen printing quality and effect.
Especially when the ink is stored outdoors or at different temperatures, it must be placed in the environment temperature for a few days before use or to the appropriate operating temperature in the ink barrel.This is because the use of cold ink will cause screen printing failure, causing unnecessary trouble.Therefore, to maintain the quality of ink, it is best to store or store in normal temperature process conditions.
Before using, the ink must be thoroughly and carefully mixed by hand or mechanically.If the ink enters the air, use it for a while.If dilution is required, mix well first and then test the viscosity.The ink barrel must be sealed immediately after use.At the same time, never put the screen printing ink back into the ink bucket with the unused ink.