PCB ink is printed circuit board used in the ink, one of the important physical characteristics of the ink is the viscosity, thixotropy and fineness. These physical properties need to be known to improve the ability to use ink.
Characteristics of PCB ink
1. Viscosity and thixotropy
Screen printing is one of the essential processes in PCB manufacturing. In order to obtain the fidelity of image reproduction, the ink must have good viscosity and suitable thixotropy. The so-called viscosity is the internal friction of a liquid, which means that under the action of an external force, one layer of liquid slides on another layer of liquid, and the friction exerted by the inner layer of liquid. Thick liquid inner sliding encountered greater mechanical resistance, thinner liquid resistance is smaller. The unit of viscosity measurement is poisons. In particular, it should be noted that temperature has a significant effect on viscosity.
Thixotropy is a physical property of a liquid, that is, the viscosity of the liquid decreases during agitation, and then quickly recovers its original viscosity after standing. By stirring, the thixotropic effect lasts long enough to reconstitute its internal structure. To achieve high quality screen printing effect, the thixotropy of ink is very important. Especially in the scraping process, the ink is agitated, and then make it liquid. This role speeds up the speed of ink through the mesh, promoting the original line of ink evenly connected. Once the scraper stops moving, the ink returns to a static state, and the viscosity is quickly restored to the original required data.
Pigments and mineral fillers are generally solid, finely ground to a particle size of no more than 4/5 micron, and form a solid state of homogeneous flow. Therefore, it is very important to require ink fineness.
Types of PCB ink
PCB ink is mainly divided into line, solder resistance, character ink three categories.
Line ink is used as a barrier layer to prevent corrosion of the line, etching when protecting the line, generally liquid sensitive type. There are two kinds of acid corrosion resistance and alkaline corrosion resistance, alkali resistance is more expensive, this layer of ink in the corrosion of the line to use alkali to dissolve away.
Solder solder ink is applied to protect the line after the line is done. There are liquid sensitive heat curing, as well as UV hardening, on the board to keep the pad, convenient welding components, play the role of insulation and oxidation.
Character ink is used to do PCB board surface marking, such as marking the component symbol, generally is white.
In fact, there are other ink, such as: stripping ink, is to do copper plating or surface treatment when the need to deal with the part of protection, and then can tear; Silver ink and so on.
PCB ink use precautions
According to the practical experience of most PCB manufacturers, the ink must be used in accordance with the following provisions:
1, in any case, the temperature of the ink must be maintained at 20-25℃ below, the temperature change can not be too large, otherwise it will affect the viscosity of the ink and screen printing quality and effect.
In particular, when the ink is stored outdoors or at different temperatures, it must be placed in the ambient temperature to adapt to a few days or make the ink bucket to the appropriate temperature. 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 stored or stored in the normal temperature process conditions.
2, before use must be fully and carefully to the ink manual or mechanical mixing. If the ink into the air, use to stand for a period of time. If dilution is required, mix thoroughly first and then test the viscosity. The ink drum must be sealed immediately after use. At the same time, never put the screen version of the ink back to the ink bucket with the unused ink mixed together.
3, it is best to use mutual adaptation of the cleaning agent to clear the net, and to be very thorough and clean. When cleaning again, it is best to use a clean solvent.
4, ink drying, must have a good exhaust system in the device.
5. The screen printing operation shall be carried out in the field where the operation conditions shall meet the technical requirements.
What is the role of PCB ink in PCB manufacturing process
Ink in the production to protect the role of copper foil, so that the copper skin is not exposed to the outside, will affect the back process, sensitive ink, carbon oil, silver oil, and carbon oil and silver oil have electrical conductivity, usually used in ink color, white oil, green oil, black oil, blue oil, red oil, butter.