PCB Technical - Circuit board solder mask ink

The basic structure of the printed circuit board is the pad, the via, the solder mask, and the text printing part. The solder mask is the yellow or red or black or green or other colors that you see. Some boards are yellow solder mask. The function of the solder mask is to prevent the parts that should not be soldered from being connected by solder. Reflow soldering is achieved by the solder mask. Let’s talk about the circuit board solder maskink and the cause of the solder mask oil loss.

Circuit board solder mask ink introduction
We usually see a green film on the surface of the circuit board. In fact, this is a circuit board solder resist ink. It is printed on the PCB to prevent soldering, so it is also called solder resist ink. The most common PCB solder mask inks we see are green, blue, white, black, yellow and red, as well as various other rare colors.

This layer of ink can cover unexpected conductors except for soldering pads, which can avoid soldering short circuits and prolong the service life of PCBs during use; it is generally called solder mask or solder mask.

Circuit board solder mask introduction:
The solder mask ink is in a viscous state before use. Through printing, pre-bake, alignment, exposure, development, post-curing, etc., all positions that need to be soldered or assembled at the end customer are exposed without soldering or The assembled base material and copper foil position are all covered with solder mask ink. Such a solder mask layer has excellent acid and alkali resistance, solvent resistance, and high temperature resistance.

Circuit board solder resist function:
1. Cover the substrate between the lines to prevent short circuits between the lines.

2. Cover all the conductive lines that do not need to be soldered to prevent the copper layer from being oxidized, and short-circuit the conductive lines during the surface treatment process.

3. When performing reflow soldering, wave soldering, and manual soldering on the client side, prevent short circuits between conductive circuits and solder pads.

Causes of oil loss in solder mask
1. When printing ink on the circuit board, the pre-treatment is not in place, such as stains, dust or impurities on the surface of the PCB board, or some areas are oxidized, but in fact, the simplest solution to this problem is to re-do the pre-treatment. Just do it again, but try to clean the dirt, impurities or oxide layer on the surface of the circuit board.

2. It may be because it is out of the oven, the baking time of the circuit board is short or the temperature is not enough, because the circuit board must be baked at a high temperature after printing the thermosetting ink, and if the baking temperature or time is insufficient, it will As a result, the strength of the ink on the board surface is not enough, and eventually the solder mask of the circuit board will fall off.

3, ink quality problems or ink expired, these two reasons will cause the circuit board ink to fall off, to solve this problem, it can only be solved by replacing the ink supplier.
The green oil on the circuit board is solder mask oil. The English name is Solder Mask. It has red, blue, green, purple, white, black and other colors. Since green is the most commonly used, many people also call solder mask green oil. Solder mask green oil is a common name in mainland China, and Taiwan is called solder mask. I personally think this name is more appropriate.