What role does ink play in the manufacturing process?
Ink plays a role in protecting copper foil in production, so that the copper skin is not exposed, which will affect the subsequent process. There are photosensitive ink, carbon oil, silver oil, and carbon oil and silver oil are conductive. The commonly used ink colors are white oil, green oil, black oil, blue oil, red oil, yellow oil.
White oil is mostly printed on the flexible circuit board with characters and attached numbers, such as diode.
The black oil is used on the surface of the Flexible circuit board in a large area to strengthen the mechanical strength of the flexible circuit board. (It is also used to keep certain parts confidential)
The green oil has insulation effect on the solder joint. Generally, there is no place for glue preservation when it is used on the FPC.
The important physical properties of ink are its viscosity, thixotropy and fineness. These physical properties need to be known to improve the ability to use ink.
Types of PCB ink
PCB ink is mainly divided into three categories: three lines, solder mask and Ningfu ink.
Line ink is used as a barrier layer to prevent corrosion of lines. It protects lines when etching. It is generally liquid sensitive. There are two kinds of acid corrosion resistance and alkali corrosion resistance. Alkali resistance is more expensive. This layer of ink should be dissolved with alkali after it is corroded out of the circuit.
Solder resistance ink is coated on the circuit after the circuit is completed as a protective circuit. There are liquid photosensitive, heat cured, and ultraviolet hardened ones. The bonding pad is reserved on the board, which is convenient for soldering components and plays the role of insulation and oxidation prevention.
In fact, there are other inks, such as peelable ink, which can be removed after protecting the parts that do not need to be treated during copper plating or surface treatment; Silver paste ink, etc.
Precautions for use of ink
According to the practical experience of most manufacturers in using ink, the following provisions must be followed when using ink:
1. In any case, the temperature of the ink must be kept below 20-25 ° C, and the temperature change cannot be too large, otherwise the viscosity of the ink and the quality and effect of screen printing will be affected.
Especially when the ink is stored outdoors or at different temperatures, it must be put at the ambient temperature for several days before reuse or the ink bucket must reach the appropriate operating temperature.
This is because the use of cold ink will cause screen printing failures, resulting in unnecessary trouble. Therefore, to maintain the quality of the ink, it is best to store it at or under the process conditions at room temperature.
2. Before use, the ink must be fully and carefully stirred manually or mechanically. If there is air in the ink, it should be allowed to stand for a period of time.
If dilution is required, the mixture shall be fully mixed first, and then the viscosity shall be tested. The ink bucket must be seaLED immediately after use. At the same time, never put the ink on the screen back into the ink bucket and mix it with the unused ink.
3. It is better to clean the screen with a suitable cleaning agent, and it should be very thorough and clean. When cleaning again, it is better to use clean solvent.
4. The ink must be dried in a device with a good exhaust system.
5. Screen printing shall be carried out on the ground where the operation conditions shall meet the technological requirements.