Circuit board ink is used for PCB processing ink, its important physICal characteristics are the viscosity, thixotropy and fineness of ink. After the circuit is completed, solder resistance ink is coated on the circuit as protection of the circuit. There are liquid photosensitive, heat curing and UV hardening. The plate is reserved for welding, which is convenient for welding components and plays the role of insulation and oxidation resistance. Character ink is used to MARK the surface of the circuit board, and it is usually white. In fact, there are other inks, such as strippable adhesive ink, which can protect parts that do not need to be treated during copper plating or surface treatment, and then can be torn off; Silver pulp ink, etc.
Screen printing is one of the important and indispensable processes in the process of printed circuit board processing. In order to improve the fidelity of image reproduction, ink must have good viscosity and appropriate thixotropy. The so-calLED viscosity is the internal friction of a liquid, that is, the friction generated by one layer of liquid when it slides over another layer of liquid under the action of an external force. The mechanical resistance to sliding inside a thick liquid is greater, while that of a thinner liquid is less. Viscosity is measured in units of poisons, and it is particularly important to note that temperature has a significant effect on viscosity.
Thixotropy is a physical property of a liquid in which the viscosity of the liquid decreases under agitation and quickly returns to its original viscosity after standing. By stirring, the thixotropic effect lasts long enough to reconstruct its internal structure. In order to obtain high quality screen printing results, the thixotropy of ink is very important. Especially in the scraping process, the ink is stirred into a liquid. This function can speed up the ink through the mesh speed, promote the original mesh line separation of ink evenly connected into a mesh. Once the scraper stops moving and the ink returns to static, its viscosity will quickly return to the original desired data.
Pigments and mineral fillers are usually solid. After fine grinding, the particle size does not exceed 4/5 micron, and forms uniform flow state in solid form. Therefore, the requirement of ink fineness is very important. PCB circuit board ink is mainly divided into circuit ink, solder resistance ink and character ink three categories, line ink used as a barrier to prevent line corrosion. It protects the line during etching. It is usually liquid sensitive. It is resistant to acid and alkali. Alkaline resistance is more expensive. This layer of ink should be dissolving with alkali after corrosion.
Ink use precautions, according to the actual experience of most manufacturers of ink use, the use of ink must be in accordance with the following provisions of reference:
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.Ink plays a role in PCB production to protect copper foil, so that the copper skin is not exposed to the outside, will affect the later process, sensitive ink, carbon oil, silver oil, and carbon oil and silver oil have electrical conductivity for use, usually used ink color, white oil, green oil, black oil, blue oil, red oil, butter.