PCB ink quality is excellent, in principle, it cannot be divorced from the above several components combination. Ink quality is excellent, is the formula of scientific, advanced and environmental protection of the comprehensive expression. It is embodied in: viscosity is the abbreviation of dynamic viscosity. It is generally expressed by viscosity, that is, the shear stress of fluid flow divided by the velocity gradient in the direction of the flow layer. The international units are PA / s or MPA / s. In PCB production, it refers to the fluidity of ink driven by external force. Conversion relation of viscosity unit: 1pA / S = 10p = 1000MPa; S = 1000cp = 10 DPa. S plasticity refers to the ink deformation under the action of external force, still maintain its properties before deformation. The plasticity of ink is helpful to improve the printing accuracy; thixotropic ink is gelatinous when standing, but the viscosity changes when it is touched, which is also known as shake and anti sagging.

Fluidity (leveling) refers to the extent to which the ink spreads around under external force. Fluidity is the reciprocal of viscosity, fluidity and ink plasticity and thixotropy. The larger the plasticity and thixotropy, the greater the fluidity; and the larger the fluidity, the easier the imprint to expand. Low fluidity, easy to appear netting, resulting in inking phenomenon, also known as reticulation; viscoelasticity refers to the ink after the scraper scraping, the shear fracture of the ink quickly rebound performance. It is required that the ink deformation speed is fast and the ink rebound is fast, which is conducive to printing. The drying property requires that the ink drying on the screen is slower, and the faster the ink is transferred to the substrate, the better the fineness of pigment and solid material particles.

PCB ink is generally less than 10 μ m, the fineness should be less than one-third of the mesh opening. Wire-drawing property when the ink is lifted by an ink spatula, the degree of tensile non fracture of the silk like ink is called wire-drawing. The ink filament is long, and there are many filaments on the ink surface and printing surface, which makes the substrate and printing plate dirty, and even unable to print. The transparency and covering power of the ink for PCB ink, according to the different uses and requirements, there are also various requirements for the transparency and hiding power of the ink. Generally speaking, line ink, conductive ink and character ink, all require high covering power. The solder resist is more flexible. Chemical resistance of ink PCB ink according to different purposes, the corresponding requirements for acid, alkali, salt and solvent requirements have strict standards; the physical properties of the ink must meet the scratch resistance, heat shock resistance, mechanical peel resistance, and meet all kinds of strict electrical performance requirements; the use of ink safety and environmental protection, PCB ink requires low toxicity, no odor , safety and environmental protection. The above summarizes the basic performance of twelve PCB inks, and in the actual operation process of screen printing, the viscosity problem is closely related to the operator.

The viscosity of the level of silk screen printing is very important. Therefore, in PCB ink technical documents and QC reports, the viscosity is clearly marked, indicating under what conditions, what type of viscosity testing instrument is used. In the actual printing process, if the viscosity of the ink is too high, it will cause the problem of missing printing, and the edge of the figure is seriously serrated. In order to improve the printing effect, diluent will be added to make the viscosity meet the requirements. But it is not difficult to find that in many cases, in order to obtain the ideal resolution (resolution), no matter what viscosity you use, it is always impossible to achieve. After in-depth study, we found that ink viscosity is an important factor, but not the only one. There is another important factor, thixotropy. It is also affecting the printing accuracy.