PCB ink quality is excellent, in principle can not be separated from the combination of the above major components.Ink quality is excellent, is the formula scientific, advanced and environmental protection of the comprehensive embodiment.It is reflected in:
Is short for dynamic viscosity (dynamicviscosity).Generally expressed in viscosity, the shear stress divided by the flow direction of fluid flow velocity gradient, the international unit for palmer/SEC (Pa).S) or mPa/S.S).In PCB production, refers to the ink is driven by external forces to produce the fluidity.
Conversion relationship of viscosity units:
1 of pa.S = 10 p = 1000 mpa.S = 1000 cp = 10. The dpa S
Refers to the ink is affected by external forces after deformation, still maintain its deformation before the nature.The plasticity of ink is conducive to improving the printing precision.
The ink is colloidal when it is stationary, and the viscosity changes when it is actuated.
(leveling) the degree to which the ink spreads out in all directions under external force.Fluidity is the inverse of viscosity. Fluidity is related to the plasticity and thixotropy of ink.The greater the plasticity and thixotropy, the greater the fluidity;Those with more liquidity tend to enlarge their footprints.The fluidity is small, easy to appear knot net, produce knot ink phenomenon, also called net grain;
Refers to the ability of the ink to bounce back rapidly when it is cut off after scraping.It is required that the printing ink deform quickly and the ink rebound quickly in order to facilitate printing;
Require ink on the screen plate drying as slow as possible, and hope ink transfer to the substrate, the faster the better;
The size of pigment and solid particles, PCB ink is generally less than 10 centimetres high. The fineness should be less than one third of the opening degree of the mesh hole.
When using the ink shovel to pick up ink, the degree of non-fracture of the silk ink is called wire-drawing.Long ink, ink surface and printing surface appear a lot of fine wire, so that the substrate and printing plate are stained, or even unable to be printed;
The transparency and covering power of ink
For PCB ink, according to the use and requirements of different, the transparency of ink and covering power also put forward various requirements.Generally speaking, line ink, conductive ink and character ink, all require high hiding power.Resistance flux is more flexible.
Chemical resistance of ink
PCB ink has strict standards for acid, alkali, salt and solvent according to different purposes.
Physical properties of ink
PCB ink must meet external force scratch resistance, heat resistant impact, mechanical stripping resistance, and meet various strict electrical performance requirements;
Ink safety and environmental protection
PCB ink requires low toxicity, no odor, safety and environmental protection.
Above we have summarized the basic performance of 12 PCB ink, and in the actual operation process of screen printing, closely related to the operator is the viscosity problem.The viscosity of the high or low, to the silk screen printing is appropriate or not, a great relationship.Therefore, in the PCB ink technical documents and QC reports, the viscosity is clearly marked, indicating under what conditions, the type of viscosity testing instruments used.In the actual printing process, if the ink viscosity is high, it will cause the difficulty of printing, and the edge of the graph is badly serrated. In order to improve the printing effect, thinner will be added to make the viscosity meet the requirements.However, it is not hard to find that in many cases, no matter what viscosity you use, it is impossible to achieve the desired resolution (resolution force).Why?After further study, it was found that ink viscosity is an important factor, but not the only one.There's another fairly important factor, thixotropy.It is also affecting the precision of printing.