After the PCB passes through the automatic tin furnace, the insulation green paint of the circuit under the board will flake off.I don't know why?What is the reason for the S/M Peeling after gold removal?
There are three major possibilities for green paint to fall off. The first is that the nature of green paint itself is not enough to withstand the test of tin furnace.Almost all the green paint used by the manufacturer will be tested for heat resistance, reliability, etc., so there should be no problem with normality. In this regard, it is necessary to review whether the material itself has changed or the process has changed.
The second possibility is the influence of external forces, including flux supply and mechanical collision, etc., especially in the case of high temperature, the characteristics of green paint no longer have high hardness like normal temperature environment, at this time, the green paint surface of the circuit board is vulnerable to any external impact, which will easily cause scratch and spalling.
The third possibility is that the circuit board will burst due to moisture absorption before the green paint application or storage. The volume of water and gas will swell up by nearly 300 times when it is heated and gasified. The instant heating and softening of green paint will make it easy for the green paint to peel off.Such problems may occur in the soldering process of the circuit board production, or in the wave soldering, back soldering and other assembly processes.
SMPEELING after the 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.Because there is a lot of possibility that you have to do a detailed analysis to clarify each item, but generally it is very important for the S/M category.