After PCB passes through the automatic tin furnace, the insulation green paint of the circuit under the board will peel off.
Do not know why there are those?
What is the reason for S/M Peeling after chemical nickel gold?
There are three big possibilities for the green paint to fall off. The first is that the nature of the green paint itself is not enough to withstand the tin stove test, which may be caused by the insufficient nature of the green paint due to expiration and failure or poor operation. Almost all the green paint used by the industry will undergo heat resistance, reliability, and other testing procedures, so there should not be regular problems. In this respect, we should review whether the material itself has changed or the process has changed.
The second may be the influence of external forces, including flux supply and mechanical collision, especially in high temperature conditions, green paint characteristics are no longer as high hardness as normal temperature environment, at this time the green paint surface of the circuit board by any external force impact is easy to produce scratches and peeling.
The third greater possibility is that the circuit board in the green paint before painting or storage caused by moisture absorption burst, the volume of water vapor in the heat gasification expansion of nearly three hundred times, instant temperature and green paint softening, very easy to make the green paint peeling. This kind of problem in the circuit board production of tin spray process can occur, may also occur in wave welding, back welding, and other assembly processes.
SMPEELING after chemical nickel gold has several possible, before the first may be copper processing is not ideal, the second may be out of S/M coated before drying, the third oxide layer may be stagnant time is too long, the fourth is likely to be poor green paint material itself is not suitable for gold range, the fifth may be out of green paint polymerization degree, 6 if you do too much in the high temperature of more than one process, such as gold and gold-plated or two gold leaching, is also likely to occur. You must do a detailed analysis to clarify item by item because there are many possibilities, but in general, it is important to use it for S/M classes.
In some special green paint, UV light reaction is relatively slow, needs oxygen, and relatively high exposure energy to achieve a high degree of polymerization. If the exposure degree of polymerization is insufficient, subsequent baking will not be able to fully achieve the due polymerization strength. If this kind of material is used, the operator should be clearly informed of the correct handling method, otherwise, there will be continuous problems. The above is for your reference.
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