Analysis of the Reasons for Solder Mask Stripping

Ink is one of the important factors affecting the quality of circuit boards, and poor quality ink is also one of the reasons for the detachment of soldering green oil on circuit boards. Let's take a look at what should be paid attention to when using printed circuit board ink?

 

There are three main reasons for the detachment of green ink from pcb solder mask:

 

1. When printing ink on a pcb, the pre-treatment is not done properly, such as stains, dust, or impurities on the surface of the board, or some areas being oxidized. In fact, solving this problem is very simple. Just do the pre-treatment again, but strive to clean up the stains, impurities, or oxide layer on the surface of the printed circuit board. This is due to the mistakes of production staff in operation and poor management.

 

2. The baking time of the printed circuit board is short or the temperature is not enough, because the printed circuit board needs to be high-temperature baked after printing the thermosetting ink. If the baking temperature or time is insufficient, it will cause the strength of the ink on the board to be insufficient. After the subsequent process flow, the final product is shipped, and customers receive the board for SMT processing. During SMT processing, the high temperature in the tin furnace can cause the ink on the printed circuit board to fall off.

 

3. Ink quality issues, such as expired ink or purchasing unknown brands of ink, can also cause PCB ink to fall off when passing through the soldering furnace. Some small board factories purchase ink that has not been used up for a long time, and there are differences in color and performance after multiple uses, making it easier for ink to fall off.

 

What precautions should I pay attention to when using ink? In the pcb industry, most manufacturers have experience in using ink and must refer to relevant regulations when using ink:

 

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1. Temperature requirements: In any case, the temperature of the ink must be maintained below 20-25 ℃, and temperature changes should not be too large, otherwise it will affect the viscosity of the ink and the quality and effectiveness of screen printing. Especially when ink is stored outdoors or at different temperatures, it must be placed at ambient temperature for a few days before reuse or until the ink barrel reaches the appropriate operating temperature. This is because using cold ink can cause screen printing malfunctions and cause unnecessary trouble. Therefore, to maintain the quality of the ink, it is best to store it under normal temperature process conditions.

 

2. Before use, the ink must be thoroughly and carefully mixed manually or mechanically. If air enters the ink, it should be left to stand for a period of time before use. If dilution is required, first mix thoroughly and then test its viscosity. 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 unused ink.

 

3. It must be equipped with a cleaning agent specifically designed for cleaning ink, and it must be very thorough and clean. No matter what color of ink it is, it should be cleaned in one go, preferably using a clean solvent, so as not to affect the use of other colors of ink.

 

4. When drying ink, it must be done in a device with a good exhaust system to ensure that the quality of the ink does not change significantly.

 

In the actual printing process, it is necessary to operate in a standardized manner and maintain the working conditions that meet the technical requirements of the process for screen printing operations.