PCB Technical - After the circuit board passes through the automatic tin furnace, the insulating green paint of the circuit under the PCB board will peel off

After the circuit board passes through the automatic tin furnace, the insulating green paint of the circuit under the PCB board will peel off

After the circuit board passes through the automatic tin furnace, the insulating green paint of the circuit under the board will peel off. What are the reasons? What is the reason for S/M Peeling after the chemical?

There are three major possibilities for the green paint peeling off of the circuit board (PCB board)

1. The circuit board (PCB board) is that the nature of green paint is not enough to withstand the test of the tin furnace. This may be due to the expired green paint or poor operation. The green paint used by the industry is almost always tested for heat resistance and reliability. Therefore, there should be no problems with normality. In this regard, it is necessary to review whether the material itself has changed or the manufacturing process has changed.

2. It may be due to the influence of external forces, including flux supply and mechanical collision, etc., especially in high temperature conditions, the characteristics of green paint are no longer as high as normal temperature environment. At this time, the green paint surface of the circuit board is affected by any external force. Prone to scratches and peeling.

3. The greater possibility is that the circuit board (PCB) will burst due to moisture absorption before the green paint is painted or stored, and the volume of the water vapor will expand nearly three hundred times when heated and vaporized, and the temperature will rise instantly and the green paint will be added. Soften, it is very easy to peel off the green paint. This type of problem occurs in the spray tin process of circuit board production, and may also occur in assembly processes such as wave soldering and reflow.

SMPEELING has the following six possibilities after the circuit board (PCB board) is gold-melted

1. It may be that the treatment in front of copper is not ideal

2. It may be insufficient drying before S/M coating

3. It may be that the stagnation time is too long to produce an oxide layer

4. It may be that the material of the green paint itself is not good and not suitable for the gold production process

5. It may be that the degree of polymerization of the green paint is insufficient

6. If you do more than one high-temperature process, such as: gold plating and gold plating together or twice immersion gold, it may also happen. Because there are many possibilities, you must do a detailed analysis to clarify item by item, but generally speaking, it is very important for the type of S/M.

Some special green paints react slowly to UV light and require anaerobic and relatively high exposure energy to achieve a high degree of polymerization. If the exposure degree of polymerization is insufficient, the subsequent baking will not be able to fully achieve the desired polymerization strength. If you use such materials, you should clearly inform the operator of the correct handling method, otherwise there will be continuous problems, the above is for your reference.