PCB Tech - Discussion on important technical performance of PCB ink

Whether the quality of PCB ink is excellent, in principle, it is impossible to break away from the combination of the above major components. The excellent quality of PCB inks is a comprehensive manifestation of the scientific, advanced and environmentally friendly formulations. It is reflected in:

Viscosity

It is an abbreviation for dynamic viscosity. 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 unit is Pa/sec (Pa. S) or milli Pascal/sec (mPa. S). In PCB production, it refers to the fluidity of PCB ink driven by external forces.

Conversion relationship of viscosity unit:

1Pa. S=10P=1000mPa. S=1000CP=10dpa.s

plasticity

It means that after PCB ink is deformed by external force, it still retains its properties before deformation. The plasticity of PCB ink is conducive to improving printing accuracy;

Thixotropic

PCB ink is gelatinous when it is standing, but the viscosity changes when it is touched. It is also called tremor and sag resistance;

fluidity

(Leveling) The extent to which PCB ink spreads around under the action of external force. Fluidity is the reciprocal of viscosity, and fluidity is related to the plasticity and thixotropy of PCB inks. The plasticity and thixotropy are large, the fluidity is large; the fluidity is large, the imprint is easy to expand. Low liquidity, easy to appear netting, resulting in ink formation, also known as netting;

Viscoelasticity

Refers to the rapid rebound performance of the PCB ink that is sheared and broken after the PCB ink is scraped by the squeegee. It is required that the PCB ink deformation speed is fast, and the PCB ink rebounds quickly to be beneficial to printing;

Dryness

It is required that the drying of PCB ink on the screen is as slow as possible, and it is hoped that after the PCB ink is transferred to the substrate, it is required to be as fast as possible;

Fineness

The size of pigment and solid material particles, PCB ink is generally less than 10μm, and the size of the fineness should be less than one-third of the mesh opening;

Wire drawing

When the PCB ink is picked up with an ink shovel, the degree to which the silk-like PCB ink is stretched without breaking is called stringiness. The ink filaments are long, and there are many filaments on the PCB ink surface and printing surface, which make the substrate and the printing plate dirty, or even unable to print;

Transparency and hiding power of PCB ink

For PCB inks, various requirements are put forward for the transparency and hiding power of PCB inks according to different uses and requirements. Generally speaking, circuit PCB ink, conductive PCB ink and character PCB ink require high hiding power. The solder resist is more flexible.

Chemical resistance of PCB ink

PCB inks have strict standards for acid, alkali, salt and solvent according to the different purposes of use;

Physical resistance of PCB ink

PCB ink must meet external scratch resistance, thermal shock resistance, mechanical peel resistance, and meet various strict electrical performance requirements;

The safety and environmental protection of PCB ink

PCB inks are required to be low-toxic, odorless, safe and environmentally friendly.