PCB ink quality is excellent, in principle can not be separated from the combination of the above major components.Ink quality is excellent, the formulation of scientific, advanced and environmental protection of the comprehensive embodiment.It is embodied 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 per second (mPa).S).In PCB production refers to the ink driven by external fluid.
Conversion relation of viscosity unit:
1 of pa.S = 10 p = 1000 mpa.S = 1000 cp = 10. The dpa S
Refers to the ink under the action of external deformation, but still maintain its pre-deformation properties.The plasticity of ink can improve printing accuracy.
Ink when static gelatinization, and when the viscosity of a change when touched, also known as rolling, anti-flow.
(leveling) ink in the external action, to the extent of development around.Fluidity is the inverse of viscosity, fluidity and ink plasticity and thixotropy.If the plasticity and thixotropy are large, the fluidity is large.The blots that are highly mobile tend to expand.Small fluidity, easy to appear network, inking phenomenon, also known as net;
Refers to the ink after the scratch board scratch, shear broken ink quickly rebound performance.It is required that the ink deforms quickly and the ink bounces back quickly to facilitate printing.
The more slowly drying ink on the screen, and the desired ink transfer to substrate, the faster the better;
The size of pigment and solid particles, PCB ink is generally less than 10 m, the fineness should be less than one third of the opening of the mesh;
When using an ink shovel to instigate ink, the extent to which the filamentous ink does not break is called wire-drawing.The length of the inks, in the ink and printing surface appear many fine wires, so that substrate and plate stained, or even unable to print;
Ink transparency and cover
For PCB ink, according to the use and requirements of different ink transparency and cover.Generally speaking, line ink, conductive ink and character ink, all require high cover.Resistance flux is more flexible.
The chemical resistance of ink
PCB ink according to the purpose of use, the corresponding requirements on acid, alkali, salt and solvent requirements are strict standards;
The physical resistance of ink
PCB ink must be resistant to external scratch, thermal shock, mechanical stripping, and meet all kinds of strict electrical performance requirements;
The use of ink safety and environmental protection
PCB ink requirements for low toxicity, odorless, safety and environmental protection.
Above we conclude the basic performance of twelve PCB inks, and in the actual process of screen printing, closely related to the operator is the problem of viscosity.The viscosity of the high and low, on the silk screen, or not, the relationship is great.Therefore, in the PCB ink technical documents and QC reports, the viscosity is clearly marked, indicating under what conditions, what type of viscosity test instruments.In the actual printing process, if the ink viscosity is relatively high, it will cause printing difficulties, and the graph edge serrated severely. In order to improve the printing effect, diluents will be added to make the viscosity meet the requirements.But it's not hard to see that in many cases, no matter what viscosity you use, you can't achieve the desired resolution (resolution).Why?After a thorough study, it was found that ink viscosity is an important factor, but not the only.There is another important factor, thixotropy.Is it also in affecting the printing precision.